Advanced Issues in springback

Robert H.Wagoner a ,?,Hojun Lim b ,Myoung-Gyu Lee c

a Department of Materials Science and Engineering,Ohio State University,Columbus,OH 43210,USA

Computational Materials Science and Engineering Department,Sandia National Laboratories,P.O.Box 5800,Albuquerque,NM 87185,USA

c Graduate Institute of Ferrous Technology,Pohang University of Science an

d Technology (POSTEC),San 31,Hyoja-dong,Nam-gu,Pohang,

Gyeongbuk 790-784,South Korea a r t i c l e i n f o Article history:Received 8March 2012Received in ?nal revised form 24July 2012Available online 24August 2012Keywords:Springback B.Constitutive behavior B.Metallic material C.Finite elements C.Numerical algorithms

a b s t r a c t

For purposes of this review,springback is the elastically driven change of shape of a metal

sheet during unloading and following forming.Scienti?c advances related to this topic

have accelerated dramatically over roughly the last decade,since the publication of two

reviews in the 2004–2006timeframe (Wagoner,2004;Wagoner et al.,2006).The current

review focuses on the period following those publications,and on work in the ?rst author’s

laboratory.Much of this recent work can be categorized into ?ve main topics.

(1)

Plastic constitutive equations (2)

Variable Young’s modulus (3)

Through-thickness integration of stress (4)

Magnesium (5)Advanced high strength steels (AHSS)The ?rst two subjects are related to accurate material representation,the third to

numerical procedures,and the last two to particular classes of sheet materials.The princi-

pal contributions in these areas were summarized and put into context.

1.Introduction

‘‘Springback’’in the present context refers to the elastically-driven change of shape that occurs following a sheet forming operation when the forming loads are removed from the work piece.It is usually undesirable,causing problems such as in-creased tolerances and variability in the subsequent forming operations,in assembly,and in the ?nal part.These effects typ-ically degrade the appearance and quality of the products being manufactured.

Springback involves small strains,similar in magnitude to other elastic deformation of metals.As such,it was formerly considered a simple phenomenon relative to the large-strain deformation required for forming.Nonetheless,appreciation for the subtleties of springback in two areas has grown dramatically.In particular,high precision is needed for the large-strain plastic response that directly affects the stresses in the body before removal of external forces.The unloading,while nominally linear elastic for most cases,can show remarkable departures from an ideal linear law.

Interest in springback as a research area and application area is substantial and is growing rapidly.A previous review in April 2005(Wagoner et al.,2006)showed that the word ‘‘springback’’appeared in virtually no standard dictionaries at the time although the term had been in use since at least the 1940’s.A search of the ISE Web of Science database (Thomson Sci-enti?c)identi?ed 334published technical papers published since 1980.A Google search found 26,800references to the word ‘‘springback.’’

?Corresponding author.Tel.:+16142922079;fax:+16142926530.

E-mail address:wagoner.2@https://www.360docs.net/doc/f318176628.html, (R.H.Wagoner).

4R.H.Wagoner et al./International Journal of Plasticity45(2013)3–20

Today,many dictionaries include the term‘‘springback.’’(Example:Free Merriam-Webster–https://www.360docs.net/doc/f318176628.html,/dictionary/springback).A search conducted on February29,2012,shows the following changes over the interven-ing7years using topics in the Web of Knowledge(Thomson Reuters)and in a World Wide Web search with Google:

20052012Increase Web of Knowledge Publications3341428428% Google/‘‘springback’’26,800499,0001862% Google/‘‘spring-back’’N/A1759,000–It appears that there has been more information and interest in springback in the past7years than in all years previously.

The current review starts from where two review papers published in2004and2006(Wagoner,2004;Wagoner et al., 2006)left off.It focuses on new advances since then,more particularly on work performed in the?rst author’s laboratory. (Neither of these limitations is strictly followed,but this simple statement captures the intent.)Five recent topics in spring-back are discussed in sections of this document:

(1)Plastic constitutive equations.

(2)Variable Young’s modulus.

(3)Through-thickness integration of stress.

(4)Magnesium.

(5)Advanced high strength steels(AHSS).

The?rst two subjects are related to accurate material representation,the third to numerical procedures,and the last two to particular classes of sheet materials.

2.Overview

Before looking at new advances,it will be useful to summarize brie?y the?eld of springback in a general way.For a more comprehensive treatment,the previous reviews are recommended(Wagoner,2004;Wagoner et al.,2006).

Many reports of springback data must be critically evaluated before accepting the results.While many kinds of experi-ments have been performed,most of them do not control the sheet tension directly,thus making reproducibility and accu-racy problematic.Examples of the kinds of geometries used include cylindrical tooling(Yu and Johnson,1983;Yuen,1990; Sanchez et al.,1996),L-bending(Livatyali and Altan,2001;Mkaddem and Saidane,2007;Gau and Kinzel,2001),U-bending (Chen and Ko?,2007;Liu et al.,2002;Hino et al.,1999;Sudo et al.,1974;Chakhari et al.,1984),V-bending(Hino et al.,1999; Chakhari et al.,1984;Zhang et al.,1997;Tekaslan et al.,2006;Tekiner,2004)and stretch-bend tests(Hino et al.,1999;Ueda et al.,1981;Kuwabara et al.,1996).

In order to reproduce springback under mechanical conditions similar to industrial practice while at the same time pro-viding the ability to control sheet tension,tool radius(R/t)and contact friction,the draw-bend springback(DBS)test was developed(Carden et al.,2002)from earlier designs used for friction testing(Wenzloff et al.,1992;Haruff et al.,1993;Val-lance and Matlock,1992).As shown in Fig.1,a strip of sheet metal is formed around a circular tool(roller)and the front actuator applies a constant displacement rate while the back actuator provides for a constant restraining force.Rollers can be set to free,driven or?xed conditions to alter the friction condition between the tool and the specimen.Draw-bend

R.H.Wagoner et al./International Journal of Plasticity45(2013)3–205 testing has been used widely for springback experiments and corresponding simulations(Carden et al.,2002;Li et al.,(1998, 1999a,1999b,2002);Geng et al.,2000;Geng and Wagoner,2002;Wagoner et al.,2000).

Springback predictions have been conducted using analytical methods and?nite element analysis(FEA).In general,the analytical approach assumes simpli?ed process and material properties.Analytical solutions for pure bending(Gardiner, 1957;Boklen,1953;Queener and De Angelis,1968;Marciniak et al.,1992;Hosford et al.,1993;Chan and Wang,1999; Yu et al.,1996)and bending with tension(Zhang et al.,1997;Kuwabara et al.,1996;Hosford et al.,1993;Chan and Wang, 1999;Yu et al.,1996;Crandall et al.,1961;Woo and Marshall,1959;Mickalich et al.,1988;Wenner,1983;Duncan and Bird, 1978;Kuwabara et al.,1995;Takahashi et al.,1996;Kuwabara et al.,1999)for various different hardening laws have been presented.More recent development of analytical solutions includes springback in creep age-forming processes(Jeune-champs et al.,2006),prediction of sidewall curl(Moon et al.,2008;Zhang et al.,2007),springback of magnesium alloys (Lee et al.,2008,2009),analytical models based on Hill’s yielding criterion and plane strain condition for U-bending and V-bending(Zhang et al.,2007a,b),and prediction of the draw-bend springback by a semi-analytical model(Lee et al.,2007).

Finite element analysis(FEA)is a well-established tool for analyzing and predicting sheet forming strains for various materials and test conditions.FE simulation of springback,however,is much more sensitive to numerical tolerances and to material model than forming simulations(Li et al.,1999b;Wagoner et al.,1997;Mattiasson et al.,1995;Lee and Yang, 1998).Numerical procedures that must be considered more critical for springback simulation include the spatial integration scheme(Li et al.,1999a,1999b;Lee and Yang,1998;He et al.,1996;Focellese et al.,1998;Narasimhan and Lovell,1999; Wagoner et al.,1999),element type(Li et al.,1998,1999a;Wang and Wagoner,2005)and time integration scheme such as implicit/implicit(Li et al.,1999a;Wagoner et al.,1997,1999;Hu et al.,1999;Lee et al.,2009b;Guo et al.,2002),expli-cit/implicit(Mattiasson et al.,1995;Lee and Yang,1998;He et al.,1996;Narasimhan and Lovell,1999;Papeleux and Pont-hot,2002;Lee,2005;Noels et al.,2004;Valente et al.,1999;Park et al.,1999),explicit/explicit(Montmayeur et al.,1999;Xu et al.,2004;Li et al.,1999),one-step approaches(Abdelsalam et al.,1999).Various material representations affect springback simulations signi?cantly:the unloading scheme(Yuen,1990;Li et al.,1999b;Wagoner et al.,1999;Tang,1987),strain hard-ening rule(Mickalich et al.,1988;Wenner,1983;Zhang and Lee,1995;Han et al.,1999),evolution of elastic properties (Chakhari et al.,1984;Morestin and Boivin,1996;Yu,2009;Eggertsen and Mattiasson,2009),plastic anisotropy(Chakhari et al.,1984;Geng et al.,2000;Geng and Wagoner,2002;Wagoner et al.,2000;Ragai et al.,2005;Verma and Haldar,2007; Gomes et al.,2005),Bauschinger effect(Gau and Kinzel,2001;Kuwabara et al.,1996;Geng et al.,2000;Kuwabara et al., 1999;Focellese et al.,1998;Zhang and Lee,1995;Baba and Tozawa,1964;Tozawa,1990;Pourboghrat and Chu,1995;Yos-hida and Uemori,2002;Firat,2007;Firat and Kaftanoglu,2008;Bouvier et al.,2005;Dongjuan et al.,2006)and anticlastic curvature(Carden et al.,2002;Li et al.,2002)are prominent examples.

In practice,springback is controlled in only two basic ways:

(1)by increasing sheet tension(Carden et al.,2002;Mickalich et al.,1988;Kuwabara et al.,1995;Zhang and Lee,1995;

Cho et al.,2003;Moon et al.,2003;Song et al.,2007;Padmanabhan et al.,2008;Sunseri et al.,1996;Liu,1988)to reduce springback,and/or

(2)by compensating the shape of tooling to achieve a?nal target shape after springback(Gan and Wagoner,2004;Ling-

beek et al.,2005;Wagoner et al.,2007;Kara?llis and Boyce,1996;Cheng et al.,2007).

The?rst method has dominated the solution to the problem of springback for the past century,and is still the mainstay. Upon increased sheet tension,the stress gradient through the thickness of the sheet is reduced and hence the bending mo-ment and the total springback is decreased.In addition to reducing springback itself,it greatly reduces the variability inher-ent with changes in material behavior.The only downside–it is a signi?cant one–is that increasing sheet tension promotes sheet splitting,particularly with newer high strength materials that typically have lower formability.Die compensation avoids this problem,but requires very accurate springback prediction and measurement,and it may not reduce the scatter of springback caused by typical process and material variations.

Perhaps the major driving force for the rapid increase of interest in springback is the rapidly increasing speci?cation of AHSS by automakers,particularly to grades such as dual-phase(DP)steel,transformation-induced plasticity(TRIP)steel,and twinning-induced plasticity(TWIP)steel.These steels represent unique challenges because in general they have higher strength/ductility combinations than traditional autobody steels and they make use of either very coarse microstructures (DP steels)or strain-induced transformations and complex hardening behavior(TRIP and TWIP steels).These differences manifest themselves in very large hardening transients following a stress reversal,large changes of elastic‘‘modulus’’follow-ing plastic deformation,and high temperatures attained by the plastic work in areas of large strain.It is not coincidental that much of the current work on springback focuses on these aspects.

3.Plastic constitutive equations

3.1.2006status

Accurate springback prediction requires knowing the stress state throughout the body before unloading,which is con-trolled by the plastic response of the material during forming.Features of the material model that can often be ignored in

6R.H.Wagoner et al./International Journal of Plasticity45(2013)3–20

satisfactory forming simulations must be taken into account for springback simulations.The dominant example of such a feature studied in recent years is the Bauschinger effect,1which is seldom considered in applied sheet metal forming simula-tions,but which can change springback magnitudes by a factor of2Geng et al.(2000).That result utilized a form of kinematic hardening(Armstrong et al.,1966;Dafalias and Popov,1976;Krieg,1975;Chaboche et al.,1979;Ristinmaa,1995;Jiang and Kurath,1996)based on Armstrong–Frederick-type hardening rules(Chaboche et al.,1979,1987;Chaboche,2008,1991;Chab-oche and Rousselier,1983;Chaboche and Nouailhas,1989;Ohno and Wang,1991,1993;Jiang and Sehitoglu,1996;Khan and Huang,1995),with a two-surface plasticity formulation.It allowed modeling of so-called‘‘permanent softening’’following a path change by incorporating a bounding surface that translates and expands according to a mixed hardening rule(Hodge, 1957;Cris?eld,1991).This hardening law has been implemented for plane-stress thin-shell elements in conjunction with three anisotropic yield criteria:Hill’48(Hill,1948,1950;Mellor et al.,1978),Barlat’s three-parameter yield function(Barlat Yld89) Barlat and Lian,1989and Barlat’s Yld96(Barlat et al.,1997).When proper material anisotropy and non-proportional path hard-ening were incorporated,springback simulations agreed with measurements within the experimental scatter(Geng et al., 2000).

3.2.Advances since2006

Nonlinear hardening models incorporating kinematic hardening have been widely adopted to improve the accuracy of the sheet metal forming simulations.Three main nonlinear hardening models used to predict springback accurately are:(1) Armstrong-Frederick type hardening models,(2)multi-surface-type hardening models and(3)a novel hardening model without simple kinematic hardening.

3.2.1.Armstrong–Frederick type hardening model

Among many models describing the?ow stress characteristics with the change of strain paths such as Bauschinger effect, transient behavior,and permanent softening,Armstrong–Frederick type non-nonlinear kinematic hardening models domi-nated before2005and remain prevalent,with new variations still being introduced.Choi et al.(2006)proposed an aniso-tropic hardening model describing an anisotropic evolution by rotation of the yield function combined with the common non-linear kinematic hardening concept.A comprehensive review on Armstrong–Frederick type hardening models is avail-able in the recent review article by Chaboche(Lee et al.,2005)where the modeling capabilities of various nonlinear kine-matic hardening models are compared in the context of predicting ratcheting effect.

The role of path changes on applied springback predictions was quanti?ed.Chaboche(2008)assessed various hardening models by the springback of a U-shaped rail.Springback prediction using the kinematic hardening underestimated the springback,while isotropic hardening overestimated it.Oliveira et al.(2007)studied the in?uence of hardening model on springback and found that not only must strain-path changes be accommodated,but also the magnitude of strain attained by each strain-path segment.

3.2.2.Multi-surface-type hardening model

Recently,conventional two-surface models,such as the ones proposed by Krieg(1975)and Dafalias and Popov(1976), were integrated and extended in a uni?ed mathematical context to incorporate anisotropy,the Bauschinger effect,transient behavior,and permanent softening(Lee et al.,2007).As shown in Fig.2,the inner loading and outer bounding surfaces were decomposed into isotropic and kinematic hardening parts,thus providing a?exible implementation to accommodate com-plex material behavior.A simple but effective stress-update algorithm was introduced with a supplemental numerical treat-ment to resolve so-called overshooting problem.

The draw-bend springback of aluminum alloy5754-O sheet was predicted(Lee et al.,2007)within the experimental scat-ter using the non-quadratic anisotropic yield function Yld2000-2d(Barlat et al.,2003)and tension/compression experiments. Comparisons with standard Chaboche-type(or Armstrong–Frederick type)hardening models showed that it is essential to consider permanent softening as shown in Fig.3.A standard method to characterize the change of the loading direction is not clear for general stress states and paths.In terms of the single surface model,particularly Armstrong-Frederick type non-linear kinematic hardening model,various modi?cations have been made mainly to include the permanent softening ob-served at large plastic strain upon reversal loading(Geng and Wagoner,2002;Choi et al.,2006).Note that the Chaboche-type hardening model used in Fig.3is the standard combined isotropic-nonlinear kinematic hardening model that cannot reproduce the permanent softening.More rigorous models modi?ed from this2-parameter model have been able to repro-duce the permanent softening successfully.

Among other hardening models based on two-surface schemes,the Yoshida–Uemori(Y–U)model Yoshida et al.(2002)is gaining popularity in part because it has relatively few parameters to be determined and it has been implemented into the commercial FE software Pam-Stamp(ESI/PSI,1995).It assumes kinematic hardening of the loading surface and combined isotropic-kinematic hardening for the bounding surface,with both surfaces based on Hill’s yield function(Hill,1948).The model reproduces the Bauschinger transient similar to a general two-surface model,but it allows for work hardening stag-1We refer to the Bauschinger effect in its most general meaning as the evolution of hardening under non-proportional paths,particularly after a path reversal such as is encountered in a tension/compression test.

nation at large plastic strain at the expense of additional complexity.It is unclear whether accounting for work hardening stagnation is critical for the accurate prediction of springback or not.Recently,Ghaei et al.(2010)proposed an implicit stress integration algorithm for Y–U model for ABAQUS (ABAQUS,2006)and applied it to a channel draw springback of DP 600steel sheet.Predicted springback angles using Y–U and Chaboche-type hardening models were in good agreement with experi-ments,although the accuracy was enhanced by taking into account reduced elastic modulus.

3.2.3.Hardening model without simple kinematic hardening approach

Kinematic hardening models,whether involving one or two yield surfaces,still invoke the translation and expansion of a ?xed surface shape,thus preserving the direction of normals at given locations.A new approach presented by Barlat et al.(2011)describes the smooth change of yield surface shape by homogenous yield function-based anisotropic hardening (HAH).The homogeneous yield function consists of a stable component associated with a general anisotropic yield function and a ?uctuating component which distorts the overall shape of the yield surface.The yield surface shape is ?attened oppo-site from the active stress state during the proportional loading,but this ?uctuating component does not affect the shape of the yield surface near the active stress state.The HAH approach leads identical plastic ?ow stress response to the isotropic hardening for the monotonous loading,but the Bauschinger effect and transient hardening behavior can be ef?ciently repro-duced by the appropriate control of ?uctuating component during continuous and reverse loading.In this regard,the HAH model is similar to the combined isotropic-kinematic hardening,but does not involve the translation of the yield surface.

The new feature in the HAH model is an introduction of a microstructure deviator which memorizes the previous defor-mation history and controls the continuous evolution of yield surface distortion during multiple strain path changes.

For

R.H.Wagoner et al./International Journal of Plasticity 45(2013)3–207

example,the yield surface locus evolution during uni-axial tension followed by equi-biaxial tension is shown in Fig.4where microstructure deviator continuously saturates from initial uni-axial loading direction to equi-biaxial direction.The FE sim-ulations for the NUMISHEET’93U-channel benchmark showed that the new approach captures the Bauschinger effect,tran-sient hardening behavior and permanent softening in cyclic stress–strain curves,which resulted in good agreement with experimentally measured springback (Lee et al.,2012,in press ).Other approaches have also introduced the distortion of the yield function (Francois,2001;Feigenbaum and Dafalias,2007,2008).

In real forming process,the deformation is more complex such that neither stress state nor the strain path does not follow that of the simple uni-axial deformation.Instead,the deformation usually involves a signi?cant strain change which leads to the development of more complicate constitutive models for the ?nite element simulation of sheet metal forming.For this purpose,physical descriptions of the microstructure changes during deformation (Teodosiu and Hu,1998;Haddadi et al.,2006)to account for the Bauschinger effect were proposed.For example,Teodosiu and Hu.(1998)and Haddadi et al.(2006)used a tensorial form of dislocation structures developed during reverse loading and combined this microstructure change effect with the conventional nonlinear kinematic hardening.The microstructure change by the description of the dis-location structure during strain path change was also considered in the crystal plasticity approach to explicitly investigate the slip activities among slip systems in polyscrystals (Peeters et al.,2000;Li et al.,2003;Holmedal et al.,2008;Kim et al.,2012).Based on this dislocation density based hardening model,the effect of strain-path change on the springback predic-tion or on the two-stage deep drawing was investigated by using ?nite element analysis (Oliveira et al.,2007;Haddag et al.,2007;Thuillier et al.,2010).The advanced constitutive models could predict the complex material behavior during stain path change under uni-axial condition.However,there was no signi?cant in?uence of the stagnated hardening or stress over-shooting during reverse or cross-loading on springback compared to that predicted by the phenomenological isotropic-non-linear kinematic hardening models which could also predict the Bauschinger effect.

Although the physically-based hardening models or dislocation-based models have been applied to the forming and springback simulations,these models usually require many parameters.For example,the model by Teodosiu and Hu (1998)has 13parameters to describe the evolutions of state variables including fourth-and second-order tensors.Recently,the HAH model was successfully extended to describe more complex material behavior during strain path change such as cross-loading (Barlat et al.,in press ).With 8hardening parameters,the extended model could predict measured stress-strain responses of an EDDQ steel sheet sample during various two-step tension tests.Especially,the ?ow stress overshooting and work hardening stagnation with very low or negative strain hardening rate for cross-loading conditions could be captured reasonably.

4.Variable Young’s modulus

4.1.2006status

Morestin and Boivin (1996)identi?ed the signi?cant role of an ‘‘elastic modulus effect’’in springback prediction while Ghosh et al.(Luo and Ghosh,2003;Cleveland et al.,2002)made detailed measurements for an aluminum alloy

and

hardening model in p -plane.The yield locus evolution during uni-axial tension uni-axial tension (Barlat et al.,2011).

R.H.Wagoner et al./International Journal of Plasticity45(2013)3–209 high-strength steel.Various mechanisms for the nonlinear unloading behavior following plastic deformation have been pro-posed over the years:residual stress(Hill,1950),anelasticity(Lubahn et al.,1961;Zener,1948),damage evolution(Yeh and Cheng,2003;Halilovic et al.,2009),twinning or kink bands in HCP alloys(Caceres et al.,2003;Zhou et al.,2008;Zhou and Barsoum,2010a,2010b),and piling up and relaxation of dislocation arrays(Morestin and Boivin,1996;Luo and Ghosh,2003; Cleveland et al.,2002;Yang et al.,2004).

AHSS show large deviations from linear unloading according to the usual Young’s modulus following plastic deformation (Morestin and Boivin,1996;Luo and Ghosh,2003;Cleveland et al.,2002;Yeh and Cheng,2003;Caceres et al.,2003;Yang et al.,2004;Augereau et al.,1999).Springback prediction can be improved signi?cantly by adjusting the value of an apparent ‘‘elastic modulus’’(Morestin and Boivin,1996;Yu,2009;Halilovic et al.,2009;Fei and Hodgson,2006;Zang et al.,2007;Li et al.,2002;Pourboghrat et al.,1998;Eggertsen and Mattiasson,2010;Vrh et al.,2008;Ghaei et al.,2008;Kubli et al.,2008; Sun and Wagoner,2011;Kim et al.,2009;Andersson et al.,2002;Yamamura et al.,2002;Bjorkhaug et al.,2004;Yao et al., 2002;Nguyen et al.,2004;Wagoner and Li,2007).Up to2006and beyond,nearly all proposed practical approaches adopt a chord modulus(Morestin and Boivin,1996;Yu,2009;Luo and Ghosh,2003;Fei and Hodgson,2006;Zang et al.,2007;Li et al.,2002;Ghaei et al.,2008;Kubli et al.,2008)that varies with plastic strain.The chord modulus uses a linear slope of stress–strain data from joining two points obtained from just before unloading and zero applied stress.It is readily incorpo-rated in?nite element(FE)simulations by adopting a different value of Young’s modulus(which may or may not be allowed to vary with the plastic strain before unloading).Unfortunately,such treatments,while convenient,do not capture the non-linearity of the unloading response.This means that partial unloading(to a?nal value of residual stress,for example)will occur with signi?cant errors of strain(corresponding to errors of?nal shape after springback).

4.2.Advances since2006

Li et al.Sun and Wagoner(2011)examined the nature of the so-called‘‘modulus effect’’and then proposed and developed a corresponding novel continuum description.Simple tensile experiments of loading and unloading of DP780and DP980 steels showed that the effect was not markedly strain-rate dependent,as would be expected on the basis of classical anelas-ticity.The observed unloading chord modulus was reduced in some cases by30%relative to Young’s modulus.Simple con-siderations rule out damage evolution as the origin of such a large effect;such alloys show very little damage before fracture under sheet forming conditions(Kim et al.,2009).

A new class of strain was identi?https://www.360docs.net/doc/f318176628.html,d‘‘Quasi-Plastic–Elastic(QPE)strain,’’it is recoverable(elastic-like)but energy dissipative(plastic-like).A3-D continuum constitutive law was devised to account for the three types of deformation behav-ior separated by two transition surfaces,one between linear elastic and QPE modes,and one between QPE and plastic modes. The QPE theory reproduced nonlinear loading and unloading curves following stress/strain path changes in a natural and highly accurate way.The magnitude of the QPE strain was found to be proportional to?ow stress or elastic strain.The stress–strain behavior upon unloading depended only on the magnitude of the stress change after plastic deformation.Most surprising,the QPE relationship was found to be identical for two alloys when unloaded from the same?ow stress,Fig.5(a).

Fig.5(b)compares experimental unloading-loading data in tension with various constitutive models.The QPE model cap-tures accurately all known features of the modulus effect whereas elastic or chord models do not.The initial unloading fol-lowing plastic deformation occurs elastically according to the handbook value of Young’s modulus,until some critical stress

(a)

(a)Relationship between dissipated energy and stress at unloading of

approaches for unloading and reloading following tensile deformation for DP

10R.H.Wagoner et al./International Journal of Plasticity45(2013)3–20

Table1

Average draw-bend springback angle simulation errors of DP980for normalized sheet tensions of0.3,0.6,0.8,and0.9.

Elastic(E o),Isotropic hardening Elastic(E o),Chaboche Chord[E(e)],Chaboche QPE,Chaboche Average error18.0o8.5o 5.3o 2.6o

is reached.At that point,a new constitutive behavior representing QPE is entered,with corresponding nonlinear unloading and energy absorption.Reloading follows a similar process,again transitioning from elastic behavior to QPE behavior and ?nally to plastic/elastic/QPE behavior at yielding.

Table1show that springback predictions based on the QPE constitutive behavior are much more accurate than existing representations.A standard Chaboche-type plastic model,even with three component back stress evolution rule,cannot be ?tted to reproduce the QPE effect adequately.However,the plastic work hardening behavior on reloading might be able to be modeled more accurately by introducing additional back-stress tensor.Draw-bend springback simulations using the QPE model agreed with experiments to within3degrees whereas other standard model formulations showed5–18degrees in average error.

5.Through-thickness integration

5.1.2006status

Industrial FE simulation of complex sheet is carried out using shell elements almost exclusively because they make the simulations much faster by reducing the number of degrees of freedom relative to solid elements.This was true in2006and remains so today.For a given number of degrees of freedom,shell elements offer the possibility to treat stress variations through the thickness very accurately by using large number of integration points(IP).(The equivalent treatment with solid elements adds more elements and degrees of freedom,thus making the computation time unrealistically long.)In spite of this advantage,most simulations of industrial sheet forming operations rely on small numbers of integration points through the thickness,typically3or5.Some commercial programs for sheet forming analysis in the past did not make provision for more than7or9integration points.

Reports were made between1999and2002by Li et al.(2002)and Wagoner et al.(1999)that25-to-51IP were required to assure1%numerical accuracy for springback simulations,depending on the bend ratio,R/t,and the magnitude of sheet ten-sion.They recommended use of25IP for general springback analysis.This work set off a?urry of activity on the subject, including con?icting and contrary reports in the literature,particularly among users and developers of commercial software. Examples include reports that there is no difference in simulated springback for3to10IP(Andersson et al.,2002)or7to15 IP(Yamamura et al.,2002),and only marginal differences between5and20IP(Bjorkhaug et al.,2004).Some authors rec-ommended7or9IP(Xu et al.,2004;Yao et al.,2002;Nguyen et al.,2004)and one(Xu et al.,2004)even stated that7IP was optimal and larger number decreased the accuracy!(This would seem to be a mathematical impossibility,as was later ver-i?ed.See below.)

5.2.Advances since2006

In order to address this controversy,Wagoner and Li(2007)conducted analytical and numerical integration of bending moments for bending-under-tension of a beam.This removed numerical uncertainties associated with FE modeling.They evaluated the role of number of integration points(N IP)on the accuracy of the numerical integration alone under various conditions of varying R/t,sheet tension and strain hardening behavior.

The simulations showed that the springback error limit must be considered,not the error for a single,particular simula-tion.The actual integration error is oscillatory in terms of small changes of R/t and sheet tension,which has the appearance of scatter if not computed systematically.This means that it is possible to get a very accurate answer within the limiting envelope,but such a result is purely fortuitous.(This may explain the much better agreement between simulations and experiments when the experimental results are known in advance!)As shown in Fig.6(a),the numerical integration error limit depends on integration scheme and increases with increased sheet tension.No single integration scheme always per-formed best,but Gauss integration is preferred for the higher tension force range,where the interaction errors are largest.

Fig.6(b)and Table2show the effect of N IP and R/t on the accuracy of springback prediction.It was shown that the max-imum error increases with decreasing bending radius and N IP.More IP are required for low-strength steel than for high strength aluminum,because the lower bending moment corresponds to larger fractional errors,and because the stress-strain curve has more curvature.These results con?rmed the original recommendations of Li and Wagoner generally,although the predictions can be re?ned for particular cases.Therefore,reports of the adequacy of small N IP(3–9)for springback analysis should be critically examined before being https://www.360docs.net/doc/f318176628.html,rger N IP can always reproduce a continuous stress distribution,and therefore the post-forming bending moment,more accurately,but at the expense of increased computational time.

Burchitz and Meinders(2008)developed an adaptive through-thickness integration method which showed negligible dif-ference for N IP larger than20–25.Xia et al.(2006)showed that the details of the results can be modi?ed by the boundary conditions adopted.

R.H.Wagoner et al./International Journal of Plasticity45(2013)3–2011

Table2

Number of integration points(N IP)required to limit the springback values for low strength steel

using Gauss integration.

Max error1%5%10%50%

R/t=56826164

R/t=203818134

R/t=100221063

6.Magnesium

6.1.2006Status

Magnesium alloys were being increasingly considered for sheet forming applications because of their low density(lower than aluminum)and high strength(similar to aluminum).The principal problem was the low ductility in tension at room temperature(Roberts,1960;Bettles and Gibson,2005).Therefore,the main areas of research focused on the deformation mechanisms,improving ductility,and possible warm forming applications.

The limited ductility of magnesium alloys made the solution of other application problems moot.For example,springback would be expected to be large because the Young’s modulus of magnesium is less than2/3that of aluminum,which itself exhibits large and problematic springback.A search of the Web of Knowledge(Thomson Reuters)through2005shows only two papers combining‘‘springback’’and‘‘magnesium’’as topics(a third paper found in the search is mostly about alumi-num-magnesium alloys).Chen and Huang(2003)showed that,as expected,forming at higher temperatures(and thus at lower stresses)reduced springback.In the other paper,Boger et al.introduced a large-strain tension-compression test that is particularly suited for revealing the widely differing strain hardening in tension and compression for magnesium alloys (Boger et al.,2005).

6.2.Advances since2006

The number of papers combining‘‘springback’’and‘‘magnesium’’since2006is38,as compared to2for all years previ-ously.Clearly,while still small,interest in the subject is increasing.Most of these more-recent papers focus on the special asymmetric plastic constitutive response of magnesium alloys(Lee et al.,2009a,b,2007;Kim et al.,2011,2009;Hama and Takuda,2011,2012;Supasuthakul et al.,2011;Hama et al.,2011;Tadano,2010),on the effects of elevated temperature or warm forming(Xiao et al.,2011;Greze et al.,2010;Hama et al.,2010;Gao et al.,2010;Ozturk et al.,2009;Palumbo et al., 2009;Kim et al.,2008;Bruni et al.,2006),or on special forming processes to mitigate problems(Kuo and Lin,2012;Gisario et al.,2011;Han and Lee,2011;Bunget et al.,2010;McNeal et al.,2009;Hino et al.,2009,2008;Palumbo et al.,2008).

Lou et al.(2007)measured the continuous,room temperature,large-strain,reverse-path hardening of Mg AZ31B and through metallography and acoustic emission associated the unusual features to twinning,untwining,and their exhaustion at room temperature.That work made use of the Boger tension–compression device(Boger et al.,2005)and the results were incorporated in complex plasticity formulations for FE implementation based on combined hardening models(Li et al.,2008, 2010),on two-surface models(Lee et al.,2007,2008),and on visco-plastic polycrystal models(Choi et al.,2009).From ap-proaches such as these,the room-temperature springback was computed using FE modeling(Lee et al.,2009b)and analytical models(Lee et al.,2008,2009a;Kim et al.,2009).

The two-surface approach(Lee et al.,2008)is based on a modi?ed Drucker–Prager yield function to incorporate the strength differential effect.Simulations based on this approach predict the springback of magnesium at room temperature

12R.H.Wagoner et al./International Journal of Plasticity45(2013)3–20

much better than conventional approaches,including the presence of a knee in the variation of springback angle with back force,Fig.7.

The drawback of conventional hardening model is clear from the comparison between measured and simulated spring-back results shown in Fig.7.Various Armstrong–Frederick type isotropic-kinematic hardening models have been reasonably well applied for the springback prediction of cubic crystals such as aluminum and steels.The evolution of back stress in the AF-type nonlinear hardening model is fundamentally exponential for a monotonic uni-axial loading,which is well suited for the standard plastic?ow stress behavior shown in cubic crystals.However,HCP materials such as magnesium alloys and titanium alloys having strong basal texture show signi?cant strength differential,asymmetric plastic?ow stress between tension and compression.Moreover,the shape of?ow stress curves during twinning(or untwining)dominant deformation such as tension followed by compression is unusually in?ected,which makes the conventional hardening law dif?cult to be directly applicable.

Measurements of the springback of magnesium under controlled draw-bend conditions have been carried out at room temperature(Lee et al.,2009b,2007).Such springback measurements,Fig.8,show the expected large magnitudes corre-sponding to the low Young’s modulus(maximum angles of100–120degrees vs.60degrees for aluminum(Carden et al., 2002),but also some unusual features.In contrast to aluminum alloys(Carden et al.,2002),AZ31B magnesium alloys show an increase or?at aspect of springback for increasing sheet tension at lower values but a more rapid decrease after a critical point,such as was presented in Fig.8.

R.H.Wagoner et al./International Journal of Plasticity45(2013)3–2013 Measurements of springback have also been performed at elevated temperature(Hama et al.,2010).For temperatures above200°C,which coincide with large reductions of?ow stress and ductility increases to practical magnitudes,springback is drastically reduced or eliminated.

The most recent work in the area of springback of magnesium alloys combines several of the aspects noted above.In par-ticular,Piao et al.(2011)developed an elevated-temperature,tension–compression testing capability suitable to for measur-ing the strain hardening under non-proportional loading as a function of temperature(i.e.as twinning disappears and slip becomes easier).A new procedure(Piao et al.,in press)makes use of this procedure in a single test to determine the presence or absence of twinning and a semi-quantitative estimate of the area of fraction of twins.

7.Advanced high-strength steels(ahss)

7.1.2006Status

Springback was known to be one of the major problems limiting their widespread adoption of advanced high-strength steels(AHSS Wagoner,2006.Fig.9compares the springback of traditional high-strength steel and AHSS with nominally the same yield stress.Evidently AHSS’s have more dramatic behavior that needed to be understood.

Advances in plastic constitutive equations for AHSS have been addressed implicitly in earlier sections of this paper and will not be addressed again here.Pertinent to springback,AHSS,and in particular dual-phase(DP)steels,have several aspects that make them distinct from traditional mild and high strength/low alloy steels:

Strength-to-modulus ratios similar to aluminum alloys.

High strain hardening concurrent with high strength.

Very large plastic work products and thus high temperatures developed during deformation.

Very large non-isotropic hardening effects after path reversals.

Very large‘‘modulus’’changes when unloading after large plastic strains.

By2006,steels of the era2had been shown not to exhibit time-dependent springback,even at periods up to7years after forming(Wang et al.,2004).This intriguing phenomenon,?rst reported in1997(Wagoner et al.,1997)for aluminum alloys, refers to the change of a formed part’s shape for up to a year after forming.Results and analysis(Wang et al.,2004)showed that time-dependent springback is caused by room-temperature creep driven by residual stresses in the equilibrated body after forming.Conditions that produce high internal stresses relative to the yield stress favor time-dependent springback.

7.2.Advances since2006

With the exception of time-dependent springback,which will be addressed below,only a few recent key AHSS references will be cited.Through-thickness variations of material properties(‘‘banding’’)in AHSS were associated with signi?cant springback differences(Gan et al.,2006).Constitutive equations for1-D(Sung et al.,2010)and3-D plasticity(Sun and Wag-oner,2011;Sun et al.,2009;Kim et al.,2011;Sun and Wagoner(submitted for publication)were introduced and shown to allow accurate simulation of springback(Kim et al.,2011;Chung et al.,2008)and formability(Kim et al.,2011).Modulus changes were found to?t into a new constitutive framework(Kim et al.,2011)and patterns of multi-axial path hardening were identi?ed and found amenable to interpretation by nonlinear kinematic hardening theories(Sun et al.,2009,submitted for publication).

The remainder of this section will?nish with a closer look at time-dependent springback of AHSS.Contrary to the status in2006,Lim et al.(2012)reported the?rst observations of time-dependent springback of steels,in particular AHSS grades of DP600,DP800,DP980,and TRIP780.Similar to aluminum alloys,but opposite of traditional steels,all AHSS showed a linear increase of the springback angles with log time for the?rst few days to weeks(Fig.10(b)).The magnitude of time-dependent springback decreased with increasing back force and tool radius,consistent with the behavior of aluminum and with a room-temperature creep mechanism.The?nal time-dependent shape change of AHSS was approximately1/3of that observed for aluminum alloys under similar test conditions and was up to18%and6%of the total springback for Al6022-T4and DP600, respectively.

The mechanism of time-dependent springback of AHSS was found to be room-temperature creep,similar to aluminum alloys.The principal alternative,anelasticity,was found to exhibit kinetics more than an order of magnitude faster than time-dependent springback.Details of room temperature creep predictions for DP600was carried out,Fig.11.Although good qualitative agreement was found,simulations over-estimated the time-dependent springback angle.However,pre-dicted time-dependent springback using time hardening and strain hardening creep laws showed better prediction than the model adopting steady-state creep law,by a factor of2–3(Lim et al.,2012).

While the choice of creep law is important(and standard ones from tensile tests do not give perfect predictions),other constitutive effects were minor,in all cases less that2%on initial springback angle,and less than7%on?nal time-dependent 2Steels tested included DQSK(drawing quality,silicon-killed steel),AKDQ(aluminum-killed,drawing quality steel)and HSLA(high strength low alloy steel).

shapes after U-channel forming and springback of an AHSS(DP600)and traditional high-strength steel(HSLA

(b)

AHSS and(b)time-dependent springback angles for DP600(Lim et al.,2012

R.H.Wagoner et al./International Journal of Plasticity45(2013)3–2015 springback angle.Examples that were tested include detailed strain hardening law,plastic anisotropy,strain rate sensitivity and FE mesh size.Deformation-induced heating is another complication for draw-bend springback of AHSS(Sung et al., 2010;Kim et al.,2011).A thermo-mechanical FE model of the DBS test for DP980showed that incorporating the thermal effect changed the springback angle by8%.

8.Concluding remark

Although the capability of the springback prediction has been signi?cantly improved in terms of the elastic–plastic con-stitutive equations and relevant FEM modeling as described in the previous sections,there are still remaining sources of uncertainty that should be considered in the future investigations.The topics that might be further improved in the spring-back analysis are:

(1)Constitutive model considering the effect of different strain paths

(2)Friction

(3)Temperature

(4)New press technology

The?rst subject becomes more important as the emergence of the advanced high-strength steels since the conventional forming technology might not be applicable to successfully form parts within expected shape accuracy.In this case,the mul-ti-stage forming technology might be necessary to improve both formability and shape accuracy,which may be optimized by the?nite element modeling that takes the effect of different strain paths into account.Several plastic constitutive models have been proposed to capture the stress-strain responses under load reversal,cross-loading condition with previous defor-mation histories(Oliveira et al.,2007;Haddag et al.,2007;Thuillier et al.,2010;Barlat et al.,in press).For example,the springback of U-channel type with or without pre-tension was proposed as a benchmark problem of Numisheet2011 (2011),which resulted in signi?cant scatters among participants depending on their applied constitutive models.The work on the stain path effect may be especially needed in areas related to the strain-induced transformation of austenite to mar-tensite and the consequent creation of anisotropic mechanical behavior,and the resultant effect of such anisotropic behavior on springback(Lee et al.,2007).

The second and third topics,friction and temperature,are usually coupled to each other.Besides an understating of con-stitutive behavior of advanced high strength steels,it is also necessary to understand the interaction between material and tool surface,or frictional behavior,and temperature dependency on the springback.Especially for the AHSS,it might be imperative to investigate the change of friction conditions during forming because the sheet materials experience variable deformation rate,temperature and pressure between blank and tool.The in?uence of the temperature in the cold forming was proved to be signi?cant in terms of the temperature dependent plastic?ow curve and friction coef?cient(Barlat et al., 2003;Yoshida et al.,2002).For example,in the real continuous forming conditions the temperature rise might be as high as 60–80°C with the AHSS,which in?uences the?ow stress curves,friction,necking and springback.Therefore,more robust measurements of stress–strain behavior and friction by taking the temperature effect into account will be necessary for bet-ter simulation of springback in the sheet metal forming.

To introduce more?exible control of the forming speed,frictional behavior and materials’temperature during forming of advanced high strength steels,a new generation of presses,so called servo presses,emerged with the capability to control the stroke of all of the moving components of the stamping tool.The advantages of servo press were well documented by the previous articles(Osakada,2010;Tamai et al.,2010).The primary feature of the servo press is able to control slide action independently by a set of powerful servo motors,which is not possible with traditional presses.Therefore with this servo press technology the displacement path can be liberally de?ned with respect to not only the position and speed but also the direction.Another advantage of servo press is that slide velocity can be controlled throughout the forming process.Since the number of achievable slide motions is inde?nite,the computer simulation technology to optimize them is more crucial for the sheet metal forming with servo press.The constitutive equations should be compatible with path dependent mechan-ical behavior,including the effect of strain rate and the friction change as a function of forming speed and temperature. Acknowledgements

This work was supported by the National Science Foundation(Grant CMMI0727641),the Department of Energy(Contact DE-FC26-02OR22910),the Auto/Steel Partnership,and the National Research Foundation of Korea(Grant NRF-2010-220-D00037).Thanks are due the many authors whose work was cited here.Special acknowledgement to collaborators who con-tributed to this work extensively over many years:Kwansoo Chung(Seoul National University),David K.Matlock(Colorado School of Mines),Michael L.Wenner(G.M.Research,retired),James G.Schroth(G.M.Research),James R.Fekete(formerly General Motors,now at NIST Boulder),Sean R.Agnew(University of Virginia),Thomas B.Stoughton(G.M.Research),Fredric Barlat(Pohang University of Science and Technology),and Myoung-Gyu Lee(formerly of Ohio State University,now at Po-hang University of Science and Technology).

16R.H.Wagoner et al./International Journal of Plasticity45(2013)3–20

References

ABAQUS,Reference Manuals,2006,Hibbit,Karlsson,and Sorensen,Inc.

Abdelsalam,U.,Sikorski,A.Karima,M.,1999.Application of one step springback for product and early process feasibility on sheet metal stamplings.In: Proceedings of NUMISHEET’99,Besancon,France.

Andersson,A.and S.Holmberg.Simulation and veri?cation of different parameters effect on springback results.in NUMISHEET2002.2002.Jeju Island, Korea.

Armstrong,P.J.,Frederick,C.O.,1966.A mathematical representation of the multiaxial Bauschinger effect.In:CEGB Report1966,Berkeley Nuclear Laboratories.

Augereau,F.,Roque,V.,Robert,L.,Despaux,G.,1999.Non-destructive testing by acoustic signature of damage level in304L steel samples submitted to rolling,tensile test and thermal annealing treatments.Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing266,285–294.

Baba,A.,Tozawa,Y.,1964.Effects of tensile force in stretch-forming process on the springback.Bulletin of JSME7,835–843.

Barlat,F.,Lian,J.,1989.Plastic behavior and stretchability of sheet metals Part I.International Journal of Plasticity5,51.

Barlat,F.,Maeda,Y.,Chung,K.,Yanagawa,M.,Brem,J.C.,Hayashida,Y.,Lege,D.J.,Murtha,S.J.,Hattori,S.,Becker,R.C.,Makosey,S.,1997.Yield function development for aluminum alloy sheets.Journal of the Mechanics and Physics of Solids45(11/12),1727–1763.

Barlat,F.,Brem,J.C.,Yoon,J.W.,Chung,K.,Dick,E.R.,Lege,D.J.,Pourboghrat,F.,Chu,E.,2003.Plane stress yield function for aluminum alloy sheets–part1: theory.International Journal of Plasticity19,1297–1319.

Barlat,F.,Gracio,J.J.,Lee,M.-G.,Rauch,E.F.,Vincze,G.,2011.An alternative to kinematic hardening in classical plasticity.International Journal of Plasticity 27(9),1309–1327.

Barlat,F.,Ha,J.,Gracio,J.J.,Lee,M.G.,Rauch,E.F.Vincze,G.,in press.Extension of homogeneous anisotropic hardening model to cross-loading with latent effects.International Journal of Plasticity.

Bettles,C.J.,Gibson,M.A.,2005.Current wrought magnesium alloys:strengths and weaknesses.JOM57,46–49.

Bjorkhaug,L.and T.Welo.Local calibration of aluminum pro?les in rotary stretch bending-Anisotropu effects.in Materials Processes and Design:Modeling, Simulation and Applications-NUMIFORM2004.2004.Columbus,Ohio,USA.

Boger,R.K.,Wagoner,R.H.,Barlat,F.,Lee,M.G.,Chung,K.,2005.Continuous,large strain,tension/compression testing of sheet materials.International Journal of Plasticity21,2319–2343.

Boklen,R.,1953.Nomogramm zur bestimmung des spannungsverlaufes bei reiner biegung fur werkstoffe mit linearer verfestigung.Zeitschrift Fur Metallkunde44(8),382–386.

Bouvier,S.,Alves,J.L.,Oliveira,M.C.,Menezes,L.F.,2005.Modelling of anisotropic work-hardening behaviour of metallic materials subjected to strain-path https://www.360docs.net/doc/f318176628.html,putational Materials Science32(3–4),301–315.

Bruni,C.,Forcellese,A.,Gabrielli,F.,Simoncini,M.,2006.Air bending of AZ31magnesium alloy in warm and hot forming conditions.Journal of Materials Processing Technology177(1–3),373–376.

Bunget, C.,Salandro,W.A.,Mears,L.,2010.And Asme,Tribological aspects in electrically-assisted forming.Proceedings of the Asme International Manufacturing Science and Engineering Conference1(2011),723–730.

Burchitz,I.A.,Meinders,T.,2008.Adaptive through-thickness integration for accurate springback prediction.International Journal for Numerical Methods in Engineering75(5),533–554.

Caceres,C.H.,Sumitomo,T.,Veidt,M.,2003.Pseudoelastic behaviour of cast magnesium AZ91alloy under cyclic loading-unloading.Acta Materialia51, 6211–6218.

Carden,W.D.,Geng,L.L.,Matlock,D.K.,Wagoner,R.H.,2002.Measurement of springback.Int.J.Mech.Sci.44,79–101.

Chaboche,J.L.,1991.On some modi?cations of kinematic hardening to improve the description of ratchetting effects.International Journal of Plasticity7(7), 661–678.

Chaboche,J.L.,2008.A review of some plasticity and viscoplasticity constitutive theories.International Journal of Plasticity24,1642–1693.

Chaboche,J.L.,2008.A review on some plasticity and viscoplasticity constitutive theories.International Journal of Plasticity24,1642–1693. Chaboche,J.L.,Nouailhas,D.,1989.A uni?ed constitutive model for cyclic viscoplasticity and its applications to various stainless steels.Journal of Engineering Materials Technology111,424–430.

Chaboche,J.L.,Rousselier,G.,1983.On the plastic and viscoplastic constitutive equations-Part I:Rules developed with internal variable concept.ASME Journal of Pressure Vessel Technology34,153–158.

Chaboche,J.L.,Dang-Van,K.,Cordier,G.,1979.Modelization of the strain memory effect on the cyclic hardening of316stainless steel,in SMIRT-51979, Division L Berlin.

Chaboche,J.L.,1987.Constitutive laws for engineering materials.Theory and Applications.In:Proceedings of the International Conference on Constitutive Laws for Eng.Materials Theory and Application,Tuscon,USA.

Chakhari,M.L.,Jalinier,J.N.,1984.Springback of complex parts.In:13th Biennial Congress of IDDRG1984.pp.148–159.

Chan,K.C.,Wang,S.H.,1999.Theoretical analysis of springback in bending of integrated circuit leadframes.Journal of Materials Processing Technology91 (1–3),111–115.

Chen,F.K.,Huang,T.B.,2003.Formability of stamping magnesium-alloy AZ31sheets.Journal of Material Processing Technology142,643–647.

Chen,P.,Ko?,M.,2007.Simulation of springback variation in forming of advanced high strength steels.Journal of Materials Processing Technology190(1–

3),189–198.

Cheng,H.S.,Cao,J.,Xia,Z.C.,2007.An accelerated springback compensation method.International Journal of Mechanical Sciences49(3),267–279. Cho,J.R.,Moon,S.J.,Moon,Y.H.,Kang,S.S.,2003.Finite element investigation on springback characteristics in sheet metal U-bending process.Journal of Materials Processing Technology141,109–116.

Choi,Y.,Han, C.S.,Lee,J.K.,Wagoner,R.H.,2006.Modeling multi-axial deformation of planar anisotropic elasto-plastic materials.Part I:Theory.

International Journal of Plasticity22(9),1745.

Choi,S.H.,Kim,D.H.,Lee,H.W.,Seoung,B.S.,Piao,K.,Wagoner,R.H.,2009.Evolution of the Deformation Texture and Yield Locus Shape in an AZ31B Magnesium Alloy Sheet under Uniazxial Loading.Mat.Sci.Eng.A:Prop.Microstruct.Process.526(1–2),38–49.

Chung,K.,K.H.Chung,W.Lee,D.Kim,K.Okamoto,C.Kim,and R.H.Wagoner.Mechanical Properties and Numerical Simulations of Friction Stir Welded TWB Automotive Sheets.in Mechanics&Mechanisms of Finite Plastic Deformation(Procs.Plasticity2008).2008.Neat Press.

Cleveland,R.,Ghosh,A.,2002.Inelastic effects on springback in metals.International Journal of Plasticity18,769–785.

Crandall,J.R.,Dahl,N.C.,1961.Introduction to the Mechanics of Solids.McGraw-Hill.

Cris?eld,M.A.,1991.Non-linear Finite Element Analysis of Solids and Structures.John Wiley&Sons,Chichester.

Dafalias,Y.F.,Popov,E.P.,1976.Plastic internal variables formalism of cyclic plasticity.Journal of Applied Mechanics98,645–651.

Dongjuan,Z.,Zhenshan,C.,Xueyu,R.,Yuqiang,L.,2006.Sheet springback prediction based on non-linear combined hardening rule and Barlat89’s yielding https://www.360docs.net/doc/f318176628.html,putational Materials Science38(2),256–262.

Duncan,J.L.,Bird,J.E.,1978.Approximate calculations for draw die forming and their application to aluminium alloy sheet.In Proceedings of the Tenth Biennial Conference on IDDRG,Warwick,England.

Eggertsen,P.A.,Mattiasson,K.,2009.On the modelling of the bending-unbending behaviour for accurate springback predictions.International Journal of Mechanical Sciences51(7),547–563.

Eggertsen,P.A.,Mattiasson,K.,2010.On constitutive modeling for springback analysis.International Journal of Mechanical Sciences52,804–818.

ESI/PSI,User manual for PAM-STAMP1995,1994,Paris,France.

R.H.Wagoner et al./International Journal of Plasticity45(2013)3–2017 Fei,D.,Hodgson,P.,2006.Experimental and numerical studies of springback in air v-bending process for cold rolled TRIP steels.Nuclear Engineering and Design236,1847–1851.

Feigenbaum,H.P.,Dafalias,Y.F.,2007.Directional distortional hardening in metal plasticity within thermodynamics.International Journal of Solids and Structures44(22),7526–7542.

Feigenbaum,H.P.,Dafalias,Y.F.,2008.Simple model for directional distortional hardening in metal plasticity within thermodynamics.Journal of Engineering Mechanics134(9),730–738.

Firat,M.,2007.U-channel forming analysis with an emphasis on springback deformation.Materials&Design28(1),147–154.

Firat,M.,Kaftanoglu,B.,2008.Sheet metal forming analyses with an emphasis on the springback deformation.Journal of Materials Processing Technology. Focellese,L.,Fratini,F.,Gabrielli,M.F.,1998.The evaluation of springback in3D stamping and coining processes.Journal of Materials Processing Technology 80–81,108–112.

Francois,M.,2001.A plasticity model with yield surface distortion for non proportional loading.International Journal of Plasticity17,703–717.

Gan,W.,Wagoner,R.H.,2004.Die design method for sheet springback.International Journal of Mechanical Sciences46(7),1097–1113.

Gan,W.,Babu,S.S.,Kapustka,N.,Wagoner,R.H.,2006.Microstructural effects on the springback of advanced high-strength steel.Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science37A(11),3221–3231.

Gao,J.,Yue,Z.,Ruan,L.,2010.Temperature in?uences on springback of AZ31sheet,in Digital Design and Manufacturing Technology,Pts1and2.G.Z.L.C.D.W.D.H.

Chai,Editor,p.484–487.

Gardiner,F.J.,1957.The springback of metals.Transactions of the AIME79,1–9.

Gau,J.T.,Kinzel,G.L.,2001.A new model for springback prediction in which the Bauschinger effect is considered.International Journal of Mechanical Sciences43(8),1813–1832.

Geng,L.M.,Wagoner,R.H.,2002.Role of plastic anisotropy and its evolution on springback.International Journal of Mechanical Sciences44(1),123–148. Geng,L.,Wagoner,R.H.,2000.Springback analysis with a modi?ed hardening model,sheet metal forming.In:Sing Tang65th Anniversary Volume,SP-1536, SAE Publication2000–01-0768.Society of Automotive Engineers.

Ghaei,A.,A.Taherizadeh,and D.E.Green.The effect of hardening model on springback prediction for a channel draw process.in NUNISHEET.2008.

Interlaken,Switzerland.

Ghaei,A.,Green,D.E.,Taherizadeh,A.,2010.Semi-implicit numerical integration of Yoshida–Uemori two-surface plasticity model.International Journal of Mechanical Sciences52(4),531–540.

Gisario,A.,Barletta,M.,Conti,C.,Guarino,S.,2011.Springback control in sheet metal bending by laser-assisted bending:Experimental analysis,empirical and neural network modelling.Optics and Lasers in Engineering49(12),1372–1383.

Gomes,C.,Onipede,O.,Lovell,M.,2005.Investigation of springback in high strength anisotropic steels.Journal of Materials Processing Technology159(1), 91–98.

Greze,R.,Manach,P.Y.,Laurent,H.,Thuillier,S.,Menezes,L.F.,2010.In?uence of the temperature on residual stresses and springback effect in an aluminium alloy.International Journal of Mechanical Sciences52(9),1094–1100.

Guo,Y.Q.,Gati,W.,Naceur,H.,Batoz,J.L.,2002.An ef?cient DKT rotation free shell element for springback simulation in sheet metal https://www.360docs.net/doc/f318176628.html,puters& Structures80(27–30),2299–2312.

Haddadi,H.,Bouvier,S.,Banu,M.,Maier,C.,Teodosiu,C.,2006.Towards an accurate description of the anisotropic behavior of sheet metals under large plastic deformation:modelling,numerical analysis and identi?cation.International Journal of Plasticity22,2226–2271.

Haddag,B.,Balan,T.,Abed-Meraim,F.,2007.Investigation of advanced strain-path dependent material models for sheet metal forming simulations.

International Journal of Plasticity23,951–979.

Halilovic,M.,Vrth,M.,Stok,B.,2009.Prediction of elastic strain recovery of a formed steel sheet considring stiffness degradation.Meccanica44,123–148. Hama,T.,Takuda,H.,2011.Crystal-plasticity?nite-element analysis of inelastic behavior during unloading in a magnesium alloy sheet.International Journal of Plasticity27(7),1072–1092.

Hama,T.,Takuda,H.,2012.Crystal plasticity?nite-element simulation of work-hardening behavior in a magnesium alloy sheet under biaxial tension.

Computational Materials Science51(1),156–164.

Hama,T.,Kariyazaki,Y.,Ochi,K.,Fujimoto,H.,Takuda,H.,2010.Springback Characteristics of Magnesium Alloy Sheet AZ31B in Draw-Bending.Materials Transactions51(4),685–693.

Hama,T.,Fujimoto,H.,Takuda,H.,2011.Prediction of Yield Loci for a Magnesium Alloy Sheet using Crystal-Plasticity Finite-Element Method,in8th International Conference and Workshop on Numerical Simulation of3d Sheet Metal Forming Processes.K.H.H.N.H.H.B.F.L.M.G.Chung,Editor,p.314–321.

Han,S.S.,Lee,M.Y.,2011.Finite element analysis of roll forming process for AZ31B magnesium alloy tube.Materials Research Innovations15,S270–S273. Han,S.S.,Park,K.C.,1999.An investigation of the factors in?uencing springback by empirical and simulative techniques.In:Proceedings of NUMISHEET’99, Besancon,France.

Haruff,J.P.,Hylton,T.A.,Matlock,D.K.,1993.Frictional response of electrogalvanized sheet steels.The Physical Metallurgy of Zinc coated steel.

He,N.,Wagoner,R.H.,1996.Springback simulation in sheet metal forming.in NUMISHEET96.1996.The Ohio State University.

Hill,R.,1948.Theory of yielding and plastic?ow of anisotropic metals.In:Proceedings of the Royal Society of London,pp.193–281.

Hill,R.,1950.The Mathematical Theory of Plasticity.Clarendon Press.

Hino,R.,Goto,Y.,Shirashi,M.,1999.Springback of sheet metal laminates subjected to stretch bending and the subsequent unbending.Advanced Technology of Plasticity,1077–1082.

Hino,R.,F.Yoshida,N.Nagaishi,and T.Naka.Incremental sheet forming with local heating for lightweight hard-to-form material.in International Journal of Modern Physics B.2008.

Hino,R.,F.Yoshida,N.Nagaishi,and T.Naka.Incremental sheet forming with local heating for lightweight hard-to-form material.in Engineering Plasticity and Its Applications:from Nanoscale to Macroscale.2009.

Hodge,P.G.,1957.A general theory of piecewise linear plasticity based on maximum shear.Journal of the Mechanics and Physics of Solids5,242–260. Holmedal,B.,Houtte,P.V.,An,Y.,2008.A crystal plasticity model for strain-path changes in metals.International Journal of Plasticity24,1360–1379. Hosford,W.F.,Caddell,R.M.,1993.Metal Forming Mechanics and Metallurgy.Prentice-Hall,Inc.

Hu,Y.,Du,C.,1999.Quasi static?nite element algorithms for sheet metal stamping springback simulation.In:Proceedings of NUMISHEET’99,Besacon, France.

IISI,Advanced high strength steel(AHSS)application guidelines.2006.

Jeunechamps,P.P.,Ho,K.C.,Lin,J.,Ponthot,J.P.,Dean,T.A.,2006.A closed form technique to predict springback in creep age-forming.International Journal of Mechanical Sciences48(6),621–629.

Jiang,Y.,Kurath,P.,1996.Characteristics of the Armstrong–Frederick type plasticity models.International Journal of Plasticity12,387–415.

Jiang,Y.,Sehitoglu,H.,1996.Modeling of cyclic ratchetting plasticity.Part I:Development of constitutive relations.Journal of Applied Mechanics63,720–725.

Kara?llis,A.P.,Boyce,M.C.,1996.Tooling and binder design for sheet metal forming processes compensating springback error.International Journal of Machine Tools&Manufacture36(4),503–526.

Khan,A.S.,Huang,S.,1995.Continuum theory of plasticity.

Kim,H.J.,Choi,S.C.,Lee,K.T.,Kim,H.Y.,2008.Experimental determination of forming limit diagram and springback characteristics of AZ31B Mg alloy sheets at elevated temperatures.Materials Transactions49(5),1112–1119.

Kim,H.,A.R.Bandar,Y.-P.Yang,J.H.Sung,and R.H.Wagoner.Failure Analysis of Advanced High Strength Steels(AHSS)during Draw Bending.in Proc.IDDRG: Mat.Prop.Data for More Effective Num.Anal.2009.Colo.School Mines.

18R.H.Wagoner et al./International Journal of Plasticity45(2013)3–20

Kim,J.H.,Lee,M.-G.,Kim,S.-J.,Chung,K.,Wagoner,R.H.,2009.Reverse effect of tensile force on sidewall curl for materials with tensile/compressive strength difference.Metals and Materials International15(3),353–363.

Kim,D.,Kim,J.H.,Lee,M.G.,Lee,Y.S.,Kang,S.H.,2011.Experimental investigation into effect of annealing treatment on springback of magnesium alloy sheets.Materials Research Innovations15,S183–S186.

Kim,J.,Lee,W.,Chung,K.H.,Kim,D.,Kim,C.,Okamoto,K.,Wagoner,R.H.,Chung,K.,2011.Springback Evaluation of Friction Stir Welded TWB Automotive Sheets.Metal.Mater.Int17(1),83–98.

Kim,J.H.,Sung,J.H.,Piao,K.,Wagoner,R.H.,2011.The shear fracture of dual-phase steel.International Journal of Plasticity27,1658–1676.

Kim,J.H.,Kim,D.,Barlat,F.,Lee,M.G.,2012.Crystal plasticity approach for predicting the Bauschinger effect in dual-phase steel.Materials Science and Engineering A539,259–270.

Krieg,R.D.,1975.A practical two surface plasticity theory.Journal of Applied Mechanics47,641–646.

Kubli,W.,A.Krasovskyy,and M.Sester.Advanced modeling of reverse loading effects for sheet metal forming processes.in NUMISHEET2008.Interlaken, Switzerland.

Kuo,C.-C.,Lin, B.-T.,2012.Optimization of springback for AZ31magnesium alloy sheets in the L-bending process based on the Taguchi method.

International Journal of Advanced Manufacturing Technology58(1–4),161–173.

Kuwabara,T.,Takahashi,S.,Akiyama,K.,Miyashita,Y.1995.2-D Springback Analysis for Stretch-Bending Processes Based on Total Strain Theory. Kuwabara,T.,Takahashi,S.,Ito,K.,1996.Springback analysis of sheet metal subjected to bending-unbending under tension part I(theory and results of numerical analysis).In:Advanced Technology of Plasticity(Proceedings of5th ICTP).1996.Columbus,Ohio.

Kuwabara,T.,Seki,N.,Takahashi,S.1999.A rigorous numerical analysis of residual curvature of sheet metals subjected to bending-unbending under tension.In:Advanced Technology of Plasticity.Springer-Verlag,Berlin.

Lee,S.W.,2005.A study on the bi-directional springback of sheet metal stamping.Journal of Materials Processing Technology167(1),33–40.

Lee,S.W.,Yang,D.Y.,1998.An assessment of numerical parameters in?uencing springback in explicit?nite element analysis of sheet metal forming process.

Journal of Materials Processing Technology80–81,60–67.

Lee,M.-G.,Kim,D.,Kim,C.,Wenner,M.L.,Wagoner,R.H.,Chung,K.,2005.Spring-back evaluation of automotive sheets based on isotropic-kinematic hardening laws and non-quadratic anisotropic yield functions.International Journal of Plasticity21(5),883–914.

Lee,M.-G.,Kim,D.,Wagoner,R.H.,Chung,K.,2007a.Semi-analytic hybrid method to predict springback in the2D draw bend test.Journal of Applied Mechanics74(6),1264.

Lee,M.G.,Kim,D.,Kim,C.,Wenner,M.L.,Wagoner,R.H.,Chung,K.,2007b.A practical two-surface plasticity model and its application to spring-back prediction.International Journal of Plasticity23(7),1189–1212.

Lee,M.G.,J.G.Choi,H.Y.Kim,R.H.Wagoner,and J.K.Lee,Experimental Study of Springback in Draw Bend Test of AZ31B Magnesium Alloy Sheet.Advanced Materials and Processing,2007.26–28:p.389-+.

Lee,M.G.,Wagoner,R.H.,Lee,J.K.,Chung,K.,Kim,H.Y.,2008.Constitutive Modeling for Anisotropic/Asymmetric Hardening Behavior of Magnesium Alloy Sheets.Int.J.Plasticity24(4),545–582.

Lee,M.G.,Kim,J.H.,Chung,K.,Kim,S.J.,Wagoner,R.H.,Kim,H.Y.,2008.Analytical model for prediction of springback in magnesium alloy sheet.In The9th International Conference on Technology of Plasticity,Hotel Hyundai,Gyeongu,Korea,pp.1083-1088.

Lee,M.G.,Kim,J.H.,Chung,K.,Kim,S.J.,Wagoner,R.H.,Kim,H.Y.,2009a.Analytical springback model for lightweight hexagonal close-packed sheet metal.

International Journal of Plasticity25(3),399–419.

Lee,M.,Kim,S.,Wagoner,R.,Chung,K.,Kim,H.,2009b.Constitutive modeling for anisotropic/asymmetric hardening behavior of magnesium alloy sheets: application to sheet springback.International Journal of Plasticity25(1),70–104.

Lee,J.W.,Lee,M.G.,Barlat,F.,2012.Finite element modeling using homogeneous anisotropic hardening and application to spring-back prediction.

International Journal of Plasticity29,13–41.

Lee,J.Y.,Lee,M.-G.,Barlat,F.,in press.An application of homogeneous anisotropic hardening to springback prediction in pre-strained U-draw/bending.

International Journal of Solids and Structures.

Li,K.P.,Wagoner,R.H.,1998.Simulation of springback,in Simulation of materials processing.Huetink,J.,.Baaijens,F.P.T(Eds.),Rotterdam,pp.21–32. Li,G.Y.,Tan,M.J.,Liew,K.M.,1999.Springback analysis for sheet forming processes by explicit?nite element method in conjunction with the orthogonal regression analysis.International Journal of Solids and Structures36(30),4653–4668.

Li,K.P.,Geng,L.M.,Wagoner,R.H.,1999a.Simulation of springback:choice of element.In:Geiger,M.(Ed.),Advanced Technology of Plasticity.Springer-Verlag,Berlin,pp.2091–2098.

Li,K.P.,Geng,L.M.,Wagoner,R.H.,1999b.Simulation of springback with the draw/bend test.In:IPMM‘99,Vancouver,BC,Canada,IEEE.

Li,X.,Yang,Y.,Wang,Y.,Bao,J.,Li,J.,2002.Effect of the material-hardening mode on the springback simulation accuracy of V-free bending.Journal of Materrials Processing Technology123,209–211.

Li,K.P.,Carden,W.P.,Wagoner,R.H.,2002.Simulation of springback.International Journal of Mechanical Sciences.

Li,S.,Hoferlin,E.,Van Bael,A.,Van Houtte,P.,Teodosiu,C.,2003.Finite element modeling of plastic anisotropy induced by texture and strain-path change.

International Journal of Plasticity,647–674.

Li,M.,X.Y.Lou,S.R.Agnew,and R.H.Wagoner.Constitutive Modeling of Slip,Twinning,and Untwinning in HCP Alloys,in Mechanical Properties and Numerical Simulations of Friction Stir Welded TWB Automotive Sheets,Mechanics&Mechanisms of Finite Plastic Deformation(Procs.Plasticity2008).

2008.Neat Press.

Li,M.,Lou,X.Y.,Wagoner,R.H.,2010.An ef?cient constitutive model for HCP polycrystals.Int.J.Plsticity26,820–858.

Lim,H.,Lee,M.G.,Sung,J.H.,Wagoner,R.H.,Kim,J.H.,2012.Time-Dependent Springback of Advanced High Strength Steels.Int.J.Plasticity29,42–59. Lingbeek,R.,Huetnik,J.,Ohnimus,S.,Petzoldt,M.,2005.The development of a?nite elements based springback compensation tool for sheet metal products.

Journal of Materials Processing Technology169,115–125.

Liu,Y.C.,1988.The effects of restraining force on shape deviations in?anged channels.Journal of Engineering and Material Technology110,389–394. Liu,G.,Lin,Z.Q.,Xu,W.L.,Bao,Y.X.,2002.Variable blankholder force in U-shaped part forming for eliminating springback error.Journal of Materials Processing Technology120(1–3),259–264.

Livatyali,H.,Altan,T.,2001.Prediction and elimination of springback in straight?anging using computer aided design methods Part1.Experimental investigations.Journal of Materials Processing Technology117(1–2),262–268.

Lou,X.,Li,M.,Boger,R.,Agnew,S.,Wagoner,R.,2007.Hardening evolution of AZ31B Mg sheet.International Journal of Plasticity23(1),44–86. Lubahn,J.D.,Felgar,R.P.,1961.Plasticity and Creep of Metals.John Wiley&Sons Inc,New York,London.

Luo,L.M.,Ghosh,A.K.,2003.Elastic and inelastic recovery after plastic deformation of DQSK steel sheet.Journal of Engineering Materials and Technology–Transactions of the Asme125,237–246.

Marciniak,Z.,Duncan,J.L.,1992.Mechanics of Sheet Metal Forming.Edward Arnold,London.Available at:.

Mattiasson,K.,Strange,A.,Thilderkvist,P.,Samuelsson,A.,1995.Simulation of springback in sheet metal forming.In:5th International Conference on Numerical Methods in Industrial Forming Process.New York.

McNeal,T.A.,Beers,J.A.,Roth,J.T.,2009.And Asme,Microstructural effects on magnesium alloy AZ31B_O while undergoing an electrically-assisted manufacturing process.Proceedings of the Asme International Manufacturing Science and Engineering Conference1,641–650.

Mellor,P.B.,Parmar,A.,1978.Plasticity analysis of sheet metal forming.In:Koistinen,D.P.,Wang,N.M.(Eds.),Mechanics of Sheet Metal Forming.Plenum Press,New York.

Mickalich,M.K.,Wenner,M.L.,1988.Calculation of springback and its variation in channel forming operations.Advances and Trends in Automotive Sheet Metal Stamping.Society of Automotive Engineering,Warrendale,PA,In.

R.H.Wagoner et al./International Journal of Plasticity45(2013)3–2019 Mkaddem,A.,Saidane,D.,2007.Experimental approach and RSM procedure on the examination of springback in wiping-die bending processes.Journal of Materials Processing Technology189(1–3),325–333.

Montmayeur,N.,Staub,C.,1999.Springback prediction with OPTRIS.In:Proceedings of NUMESHEET’99,Besancon,France.

Moon,Y.H.,Kang,S.S.,Cho,J.R.,Kim,T.G.,2003.Effect of tool temperature on the reduction of the springback of aluminum sheets.Journal of Materials Processing Technology132,365–368.

Moon,Y.H.,Kim,D.W.,Van Tyne,C.J.,2008.Analytical model for prediction of sidewall curl during stretch-bend sheet metal forming.International Journal of Mechanical Sciences50(4),666–675.

Morestin,F.,Boivin,M.,1996.On the necessity of taking into account the variation in the Young’s modulus with plastic strain in elasti-plastic software.

Nuclear Engineering and Design162,107–117.

Narasimhan,N.,Lovell,M.,1999.Predicting springback in sheet metal forming:an explicit to implicit sequential solution procedure.Finite Elements in Analysis and Design33,29–42.

Nguyen,V.T.,Z.Chen,and P.F.Thomson.Prediction of spring-back in anisotropic sheet metals.in Proceedings of Institution of Mechanical Engineers.Part C, J.Mech,Eng.Sci.2004.

Noels,L.,Stainier,L.,Ponthot,J.P.,https://www.360docs.net/doc/f318176628.html,bined implicit/exp licit time-integration algorithms for the numerical simulation of sheet metal forming.

Journal of Computational and Applied Mathematics168(1–2),331–339.

Numisheet2011,Benchmark4:Pre-straineffect on spring-back of2D drawbending,K.Chung,H.Huh,H.N.Han,F.Barlat,M.G.Lee(Eds.),The8th International Conference and Workshop on Numerical Simulation of3D Sheet Metal Forming Processes,Seoul,Korea(2011),pp.171–175.

Ohno,N.,Wang,J.D.,1991.Transformation of a nonlinear kinematic hardening rule to a multisurface form under isothermal and nonisothermal conditions.

International Journal of Plasticity7,879–891.

Ohno,N.,Wang,J.D.,1993.Kinematic hardening rules with critical state of dynamic recovery,Parts I and II.International Journal of Plasticity9,375–403. Oliveira,M.C.,Alves,J.L.,Chaparro,B.M.,Menezes,L.F.,2007.Study on the in?uence of work-hardening modeling in springback prediction.International Journal of Plasticity23,516–543.

Oliveira,M.C.,Alves,J.L.,Chaparro,B.M.,Menezes,L.F.,2007.Study on the in?uence of work-hardening modeling in springback prediction.International Journal of Plasticity23,516–543.

Osakada,K.,2010.Application of Servo Presses to Metal Forming Processes.J.Iron Steel Res.Int.81,9–16.

Ozturk,F.,Toros,S.,Kilic,S.,Bas,M.H.,2009.Effects of cold and warm temperatures on springback of aluminium-magnesium alloy5083–H111.Proceedings of the Institution of Mechanical Engineers Part B-Journal of Engineering Manufacture223(4),427–431.

Padmanabhan,R.,Sung,J.H.,Lim,H.,Oliveira,M.C.,Menezes,L.F.,Wagoner,R.H.,2008.In?uence of draw restraining force on the springback in advanced high strength steels.In:Proceedings of the11th ESAFORM2008Conference on Material Forming.Springer.

Palumbo,G.,Sorgente,D.,Tricarico,L.,2008.Numerical-experimental analysis of thin magnesium alloy stripes subjected to stretch-bending.Journal of Materials Processing Technology201(1–3),183–188.

Palumbo,G.,Sorgente,D.,Tricarico,L.,2009.Tangential bending and stretching of thin magnesium alloy sheets in warm conditions.Materials&Design30

(3),653–660.

Papeleux,L.,Ponthot,J.P.,2002.Finite element simulation of springback in sheet metal forming.Journal of Materials Processing Technology125,785–791. Park,D.W.,Kang,J.J.,Hong,J.P.,1999.Springback simulation by combined method of explicit and implicit FEM.In:Proceedings of NUMISHEET‘99. Peeters,B.,Kalidindi,S.R.,Van Houtte,P.,Aernoudt,E.,2000.A crystal plasticity based work-hardening/softening model for b.c.c.metals under changing strain paths.Acta Materialia48,2123–2133.

Piao,K.,Lee,J.K.,Kim,J.H.,Kim,H.Y.,Chung,K.,Barlat,F.,Wagoner,R.H.,2012.A Sheet Tension/Compression Test for Elevated Temperature.Int.J.Plasticity 38,27–46.

Piao,K.,Chung,K.,Lee,M.G.,Wagoner,R.H.,2012.Twinning-Slip Transitions in Mg AZ31B.Metall.Mater.Trans.A43(9),3300–3313.

Pourboghrat,F.,Chu,E.,1995.Springback in plane strain stretch/draw sheet forming.International Journal of Mechanical Sciences36(3),327–341. Pourboghrat,F.,Chung,K.,Richmond,O.,1998.A hybrid membrane/shell method for rapid estimation of springback in anisotropic sheet metlas.Journal of Applied Mechanics-Transaction of the ASME65,671–684.

Queener,C.A.,De Angelis,R.J.,1968.Elastic springback and residual stresses in sheet metal formed by bending.Transactions of the AIME61,757–768. Ragai,I.,Lazim,D.,Nemes,J.A.,2005.Anisotropy and springback in draw-bending of stainless steel410:experimental and numerical study.Journal of Materials Processing Technology166(1),116–127.

Ristinmaa,M.,1995.Cyclic plasticity model using one yield surface only.International Journal of Plasticity11(2),163–182.

Roberts,C.S.,Magnesium and Its Alloys1960:Wiley,New York/London.

Sanchez,L.,Robertson,R.D.,Gerdeen,J.C.,1996.Springback of sheet metal bent to small radius/thickness ratios.SAE Paper960595.

Song,J.H.,Huh,H.,Kim,S.H.,2007.A simulation-based design parameter study in the stamping process of an automotive member.Journal of Material Processing Technology189,450–458.

Sudo,C.,Kojima,M.,Matsuoka,T.,1974.Some investigations on elastic recovery of press formed parts of high strength steel parts.In:8th Biennial Congress of IDDRG.

Sun,L.,Wagoner,R.H.,https://www.360docs.net/doc/f318176628.html,plex unloading behavior:Nature of the deformation and its consistent constitutive representation.International Journal of Plasticity27(7),1126–1144.

Sun,L.,J.H.Kim,and R.H.Wagoner,Non-Proportional Loading of Dual-Phase Steels and its Constitutive Representation.Proc.IDDRG2009,Proc.IDDRG:Mat.

Prop.Data for More Effective Num.Anal,2009:p.119-130.

Sun,L.and R.H.Wagoner,Constitutive Modeling of Proportional and Non-Proportional Hardening of Dual-Phase Steels.J.Mater.Proc.Technol.,Submitted for publication.

Sung,J.H.,Kim,J.H.,Wagoner,R.H.,2010.A plastic constitutive equation incorporating strain,strain-rate,and temperature.International Journal of Plasticity 26(12),1746–1771.

Sunseri,M.,Cao,J.,Kara?llis,A.P.,Boyce,M.C.,1996.Accommodation of springback error in channel forming using active binder force control:numerical simulations and experiments.Journal of Engineering Materials and Technology–Transactions of the Asme118(3),426–435.

Supasuthakul,J.,Hodgson,P.D.,Yang,C.,2011.Analytic Study on Pure Bending of Metal Sheets,in8th International Conference and Workshop on Numerical Simulation of3d Sheet Metal Forming Processes.K.H.H.N.H.H.B.F.L.M.G.Chung,Editor,p.541–548.

Tadano,Y.,2010.Polycrystalline behavior analysis of pure magnesium by the homogenization method.International Journal of Mechanical Sciences52(2), 257–265.

Takahashi,S.,Kuwabara,T.,Ito,K.1996.Springback analysis of sheet metal subjected to bending unbending under tension.Part2(experimental veri?cation).In:Advanced Technology of Plasticity,?ìProceedings of the5th ICTP,vol.2.The Ohio State University,Columbus,OH.

Tamai,Y.,Yamasaki,Y.,Yoshitake,A.,Imura,T.,2010.Improvement of Formability in Stamping of Steel Sheets by Motion Control of Servo Press.J.Iron Steel Res Int.81,686–689.

Tang,S.C.,1987.Analysis of springback in sheet forming operation.Advanced Technology of Plasticity I,193–197.

Tekaslan,O.,Seker,U.,Ozdemir,A.,2006.Determining springback amount of steel sheet metal has0.5mm thickness in bending dies.Materials&Design27

(3),251–258.

Tekiner,Z.,2004.An experimental study on the examination of springback of sheet metals with several thicknesses and properties in bending dies.Journal of Materials Processing Technology145(1),109–117.

Teodosiu,C.,Hu,Z.,1998.Microstructure in the continuum modeling of plastic anisotropy.In:Cartensen,J.V.,Leffers,T.,Lorentzen,T.,Pedersen,O.B., S?rensen,B.F.,Winther,G.(Eds.),Proceedings of the Ris?International Symposium on Material Science.Modelling of Structure and Mechanics of Materials from Microscale to products,Roskilde,Denmark,Ris?National Laboratory,pp.149–168.

20R.H.Wagoner et al./International Journal of Plasticity45(2013)3–20

Thuillier,S.,Manach,P.Y.,Menezes,L.F.,2010.Occurence of strain path changes in a two-stage deep drawing process.Journal of Materials Processing Technology210,226–232.

Tozawa,Y.,1990.Forming technology for raising the accuracy of sheet-formed products.Journal of Materials Processing Technology22,343–351. Ueda,M.,Ueno,K.,Kobayashi,M.,1981.A study of springback in the stretch bending of channels.Journal of Mechanics Working Technology5,163–179. Valente,M.,Traversa,D.,1999.Springback calculation of sheet metal parts after trimming and?anging.In:Proceedings of NUMISHEET‘99.

Vallance,D.W.,Matlock,D.K.,1992.Application of the bending-under-tension friction test to coated sheet steels.Journal of Materials Engineering and Performance1,685–694.

Verma,R.K.,Haldar,A.,2007.Effect of normal anisotropy on springback.Journal of Materials Processing Technology190(1–3),300–304.

Vrh,M.,Halilovic,M.,Stok,B.,2008.Impact of Young’s modulus degradation on springback calculation in steel sheet drawing.Strojniski Vestnik-Journal of MEchanical Engineering54,288–296.

Wagoner,R.H.,2004.Sheet springback.In:Raabe,D.et al.(Eds.),Continuum Scale Simulations of Engineering Materials,Fundamentals–Microstructures–Press Applications.Wiley-VCH,Weinheim,pp.777–794.

Wagoner,R.H.,2006.Report:Advanced High Strength Workshop.Arlington,Virginia.

Wagoner,R.H.,Li,M.,2007.Simulation of springback:Through-thickness integration.International Journal of Plasticity23(3),345–360.

Wagoner,R.H.,Carden,W.D.,Matlock,D.K.,1997.Springback after drawing and bending of metal sheets.In:Proceedings of IPMM’97,Intelligent Systems Applications.University of Wollongong.

Wagoner,R.H.,Geng,L.M.,Li,K.P.,1999.Simulation of springback with the draw/bend test.In:The Second International Conference on Intelligent Processing and Manufacturing of Materials,Honolulu,HI,USA.

Wagoner,R.H.,Geng,L.,Balakrishnan,V.,2000.Springback simulation with non-isotropic hardening.In:3rd Esaform Conference on Material Forming,pp.

VII-3–VII-6.

Wagoner,R.H.,Wang,J.F.,Li,M.,2006.Springback.ASM Handbook.ASM,Materials Park,OH,pp.733–755.

Wagoner,R.H.,Li,M.,Gan,W.,2007.Sheet springback:prediction and design.HSIMP2007:high speed industrial manufacturing processes,Cetim,pp.1–7. Wang,J.,Wagoner,R.H.,2005.A practical large strain solid?nite element for sheet forming.International Journal for Numerical Methods in Engineering63, 473–501.

Wang,J.F.,Wagoner,R.H.,Carden,W.D.,Matlock,D.K.,Barlat,F.,2004.Creep and anelasticity in the springback of aluminum.International Journal of Plasticity20(12),2209–2232.

Wenner,M.L.,1983.On the work hardening and springback in plane strain draw forming.J.Appl.Metalworking2,277–287.

Wenzloff,G.J.,Hylton,T.A.,Matlock,D.K.,1992.A new procedure for the bending under tension friction test.Journal of Material Engineering and Performance1,609–613.

Woo,D.M.,Marshall,J.,1959.The Engineer208,135–136.

Xia,Z.C.and D.Zeng,Understanding through-thickness integration in springback simulation.SAE Technical Paper2006–01-0147SAE,Warrendale,PA 15096,2006.

Xiao,H.,Liu,J.,Zhang,S.,Zhang,X.,Wang,Q.,2011.Research on a New Process:Warm Tension-Rotation Bending of AZ31Extruded Pro?le.Advanced Science Letters4(3),1002–1006.

Xu,W.L.,Ma,L.,Li,C.H.,Feng,W.J.,2004.Sensitive factors in springback simulation for sheet metal forming.Journal of Materials Processing Technology151 (1–3),217–222.

Yamamura,N.,T.Kuwabara,and A.Makinouchi.Springback simulations for stretch-bending and draw-bending processes using the static explicit FEM code, with an algorithm for canceling non-equilibrated forces.in NUMISHEET2002.2002.Jeju Island,Korea.

Yang,M.,Y.Akiyama,and T.Sasaki,Evaluation of change in material properties due to plastic deformation.Journal of Materials Processing Technology,2004. Yao,H.,Liu,S.-D.,Du,C.,Hu,Y.,2002.Techniques to improve springback prediction accuracy using dynamic explicit FEA codes.SAE Transactions111,100–106.

Yeh,H.Y.,Cheng,J.H.,2003.NDE of metal damage:ultrasonics with a damage mechanics model.International Journal of Solids and Structures40,7285–7298.

Yoshida,F.,Uemori,T.,2002.A model of large-strain cyclic plasticity describing the Bauschinger effect and workhardening st.International Journal of Plasticity18,661–686.

Yoshida,F.,Uemori,T.,Fujiwara,K.,2002.Elastic–plastic behavior of steel sheets under in-plane cyclic tension-compression at large strain.International Journal of Plasticity18,633–659.

Yu,H.Y.,2009.Variation of elastic modulus during plastic deformation and its in?uence on springback.Materials&Design30,846–850.

Yu,T.X.,Johnson,W.,1983.Cylindrical bending of metal strips.Material Technology10,439–447.

Yu,T.X.,Zhang,L.C.,1996.Plastic Bending,Theory and Applications.World Scienti?c.

Yuen,W.Y.D.,1990.Springback in the stretch-bending of sheet metal with non-uniform deformation.J.Mater.Process.Technol.22,1–20.

Zang,S.,Liang,J.,Guo,C.,2007.A constitutive model for spring-back prediction in which the change of Young’s modulus with plastic deformation is considered.International Journal of Machine Tools and Manufacture47(11),1791–1797.

Zener,C.,Elasticity and anelasticity of metals,1948,The University of Chicago,Illinois:Press Chicago.

Zhang,Z.T.,Lee,D.,1995.Effects of process variables and material properties on the springback behavior of2D-draw bending parts.Automotive Stamping Technology,SAE,p.11–18.

Zhang,Z.T.,Hu,S.J.,1997.Mathematical modeling in plane strain bending.SAE Technical publication,970439.

Zhang,D.,Cui,Z.,Ruan,X.,Li,Y.,2007a.An analytical model for predicting springback and side wall curl of sheet after https://www.360docs.net/doc/f318176628.html,putational Materials Science38,707–715.

Zhang,D.,Cui,Z.,Chen,Z.,Ruan,X.,2007b.An analytical model for predicting sheet springback after V-bending.Journal of Zhejiang University Science A8

(2),237–244.

Zhou,A.G.,Barsoum,M.W.,2010a.Kinking nonlinear elasticity and the deformation of magnesium.Metallurgical and Materials Transaction A-Physical Metallurgy and Materials Science40A,1741–1756.

Zhou,A.G.,Barsoum,M.W.,2010b.Kinking nonlinear elastic deformation of Ti3AlC2,Ti2AlC,Ti3Al(C-0.5,N-0.5)(2)and Ti2Al(C-0.5,N-0.5).Journal of Alloys and Compounds498,62–70.

Zhou,A.G.,Basu,S.,Barsoum,M.W.,2008.Kinking nonlinear elsticity,damping and microyielding of hexagonal close-packed metals.Acta Materialia56,60–

67.

文档管理系统可行性研究

文档管理系统可行性研究报告 The Report of Feasibility Studies 专业：计算机科学与技术班级：姓名：报告日期：

文档管理系统——可行性研究报告 1.引言 1.1 编写目的随着计算机的普及、网络越来越便捷，现在无论公司、学校还是政府机构都将他们的各种文档资料保存在计算机上。如果不好好管理这些文档资料，时间长了，各种各样的资料越来越多，将造成保存困难，查找、使用不方便。本课程设计主要是为实现文档管理，主要包括文件的制作、修改、传递、签定、保存、销毁、存档等功能的程序设计。通过本系统能够实现文档管理自动化管理的目标，为企业提供了安全、可靠、开放、高效的文档管理功能，不仅方便了文档管理的日常操作，而且必免了手工管理中的一系列错误的发生，提高了企业的办公效率和企业文件管理的综合水平。 1.2 背景 1. 软件系统的名称：文件管理系统 2. 任务提出者：文档管理系统开发小组 3. 开发者：文档管理系统开发小组 4. 实现完成的系统实施地点：小组成员个人机、学校机房和客户方计算机 1.3 定义管理系统：是指利用计算机、网络、数据库等现代信息技术，处理组织中的数据、业务、管理和决策等问题，并为组织目标服务的综合系统。 1.4 参考资料 [1]张海藩.软件工程导论（第四版）[M].北京：清华大学出版社，2003 [2]W atts S.Humphrey《软件工程规范》第1版.清华大学出版社.2004年 2.可行性研究的前提 2.1 要求它将满足用户对资源的管理：增加，删除，修改，搜索及查看资源。具体说来，该系统将具备下面的功能：（1）增加资源——用户能够添加一个资源，该资源可以是电子资源（比如PC上某个目录下的一张图片）或者是非电子资源（例如书桌上的本书）。添加该资源后，用户将可以通过该系统直接管理和使用该资源。

档案管理系统软件方案及主要功能

档案管理系统软件方案及主要功能电子档案管理系统既可以自成体系，提供用户完整的电子档案管理和网络查询利用，也可以与本单位的OA办公自动化或MIS信息管理系统相结合，形成更加完善和高效的现代化信息管理网络，从而高效、完整地实现人们对各种类型的档案资料进行电子化、网络化集中管理，并对其流转过程进行实时的监控。使用乾坤档案管理系统，可全面管理电子档案资料，从电子档案的收集、入库、整理、发布、归档、查询、借阅、销毁等方面进行全过程控制和管理，实现档案信息管理传输的自动化、档案资料一体化、标准化、规范化和共享化。乾坤档案管理系统广泛应用于以下行业：国家政府机关、能源部门（电力、石油石化、煤炭）、水利部门、冶金部门、铁路部门、通信行业、机电兵船行业、交通、金融保险、建设行业、图书馆、档案馆以及中大型企业。可管理各类形式档案：文书档案、

人事档案、照片档案、实物档案、会计档案、基建档案、工程档案、客户关系档案等等。符合国家档案局发布的《归档文件整理规则》(最新标准)。档案管理一体化系统主要功能主要包括收文管理、行文管理、合同管理、档案管理、查询管理、用户管理、系统维护等七大模块。可以存储并读取各种格式的电子文档。内置完备的打印格式，并可自定义打印格式，各类登记簿实现了流水、满页打印。可设置为网络版，实现局域网或广域网上多台计算机数据库的共享。支持打印、读取条形码，支持读取员工卡，为档案文件的借阅登记提供了更多方便。提供完美的解决方案经验出发，从管理领先角度思考如何优化图文管理效益，从而针对各大企业的管理需求，设计出乾坤DMS图文管理系统。「乾坤图文管理系统」透过计算机化接口，提供用户可以关键词或编号索引快速轻松搜寻档案，并结合管理人员的文件调阅权限，审阅签核流程；再者，透过电子化的档案集中存放，不仅保障文件安全性，可防止非经授权的图文数据流出，同时也能视需求调阅不同版本，管理经验得以传承，企业知识也可妥善保存应用。

文件管理系统设计方案和对策

文件管理系统设计方案传统的管理和保存文件的方式是人工生成和保管文件（包括：生成、传阅、审批、进入受控状态等），文件通常是保存在文件柜中的。由于文件数量多，版本复杂，在实际使用中经常出现问题，例如：文件版本不一致、文件查找困难、文件管理处理历史记录报表工作量过大等。本方案旨在解决单位对大量工程和技术文件的管理，达到并确保工作人员手中文件版本的一致性、文件更改的可追溯性，同时以实现电子公告、电子通知、电子邮件、公文收发等功能来提高单位日常办公及管理的自动化。一、文件管理系统的建设目标和意义目标：满足企业对文件信息进行集中管理、查询的需要通过文件的集中管理，使企业实现资料共享，资料同步更新企业重要文档的使用权限设置，一方面节约了资本，另一方面自动化管理，保证了资料的保密性和安全性简化了员工查找和使用资料的工作步骤，使员工把时间放在其他更有价值的工作上，减少重复劳动，提高工作效率，为企业争取更多利润把无纸化办公和自动化办公结合起来，实现了无纸化和物理化文档管理的有机组合把先进的数据库技术运用于文档管理，促进企业信息化管理的进步文件管理系统建设意义： 1、分类、管理企业文件文件管理系统通过数据库管理，对企业纷杂的文件内容进行分门别类的管理，按照不同的介质（图片、影音、word、excel、ppt、pdf等）进行存放管理。文件管理系统通过权限管理，对不同的员工开放不同级别的文件库，最大程

度保证企业的文件安全。 2、共享、学习企业文件文件管理系统通过内部网络将文件资本进行共享，让更多的人分享到企业文件资本，拓宽部门和员工的知识范围。 3、应用、增值文件资本文件管理平台构建面向企业业务流程的文件管理系统，使得工作过程中显形知识结构化，隐形知识显形化。通过文件的不断重复应用，实现文件增值。有效的规避了人员升迁流动所造成了关键业务领域的损失，让业务运行不辍。 4、提升企业竞争力创造企业新竞争价值，增加企业利润，降低企业成本，提高企业效率。建立企业新文化，鼓励思想自由，培育创新精神。通过减少反应时间来提高为客户服务的水平，通过快速向市场提供产品和服务来增加收入。二、文件管理系统的建设要求首先是支持的文件内容要全面，从文件管理的内容角度，至少应该包括： ?对信息的发布，比如直接发布各种内容 ?对文档的管理，如各类DOC、XLS、PPT等文件 ?对数据信息的管理，如各类报表等等有利于充分利用文件： ?对链接的处理：在内容中可以互相链接，它是有效利用文件的非常重要的环节 ?强有力的索引能力，特别是全文检索 ?对于动态数据的强有力查询能力，比如可以根据各种条件进行查询

企业文档管理系统的基本功能

企业文档管理系统的基本功能建立一套规范的文档管理系统在企业信息化建设的过程中是必不可少的，是企业规范化管理的重要一步。随着科技的不断进步，文档管理系统可以提供的功能已不再局限于单纯的文档集中管理，文档管理系统可以帮你做什么，都搞清楚了吗？企业文档管理系统的含义：企业文档管理系统提供给企业一个易用，安全，高效的文档管理软件。通过该系统软件，企业可以集中存储和管理海量的文档和各类的数字资产（如Office文档，视频，音频，图片，等等），系统提供了严谨和灵活的权限管理机制和文档共享机制。当前，市面上的各类文档管理系统多种多样，但其实概括起来，常用功能基本包含以下五项：

1、集中存储：文档管理系统通过集中存储的形式，将企业原先散乱存放在员工个人办公设备上的文档统一存储在一个地方，实现文档的集中管理以及合理共享。 2、快速检索：方便快捷的让用户在海量的文档中搜索到急需的文档。 3、文档编辑：用户可以直接在文档管理系统中编辑文档，依据软件产品的不同，还可细分为支持在线编辑或需要下载到本地后再编辑。但总体上，一款优秀的文档管理系统，其编辑模式都不需要用户改变原有的操作习惯。 4、权限管理：系统必须支持权限控制，系统管理员可根据员工所属岗位、部门设置不同的文档使用权限，普通用户仅可在其权限范围内执行相关的操作。 5、文档保护：系统须对文档进行必须要加密保护，无轮是存储或是传输过程中，确保企业文档的安全。除了上述常用的基本功能之外，像云盒子这类的基于企业私有云环境下的文档管理系统，还集成了即时通讯、客户端多平台漫游、移动办公等多项功能。如此，企业不仅仅可对内部的文档进行规范化管理，更可利用其它功能来提高日常办公效率。

文档管理系统的功能及优势介绍-中文

一、文档管理解决方案的优势面对竞争激烈的市场，最快地研发产品并投入市场成为企业竞争的重要手段，随着企业ERP系统的建设，使得最快地将产品投入市场成为可能，而因此带来的生产的进程加快，产品的研究速度加快，对相关的技术文档的管理提出了越来越高的要求，产品的相关文档（如：设计图、像片、相关技术文档等）的增长正在急速增加。因此高质有效的文档管理变得越来越重要。 DMS系统通过提供一个大范围的文档管理功能，支持不同应用程序之间的文档和数据交换。并且通过R/3集成各种应用程序模块内的文档管理来实现企业范围内各种文档的管理。你还可以裁剪文档管理功能来满足个别用户的需要。各种选项包括权限规定，指定文档号、选择信息记录的数据字段。 DMS （文档管理）模块与R/3中的各功能模块配合，为企业提供管理范围内文档管理的功能，使得财务凭证、生产业务文档和人员档案附件从创建到存储都得到完善的管理。二、文档管理系统（DMS） SAP-DMS是集档案管理与计算机辅助设计于一体的大型应用系统。完备周密的档案管理功能，对档案进行分类建库管理，提供内部保密机制、控制对文档库的读写及提供档案库内部的级别限制，严格的保密性和可靠性等功能。采用SAP-DMS文档管理系统解决方案，您可以获得支持企业业务过程中的实时文档数据，它还有助于您规范企业档案的管理。 SAP-DMS通过提供一个大范围的文档管理功能，支持不同应用程序之间的产品文档和数据交换。并且通过R/3集成各种应用程序模块内的文档管理来实现企业范围内各种文档的管理。你还可以裁剪文档管理功能来满足个别用户的需要。各种选项包括权限规定，指定文档号、选择信息记录的数据字段。系统相关功能介绍如下：概述文档管理系统将文档在SAP系统中更紧密的集成。为了集成SAP系统中不同用户的需要和不同应用模块数据整理的文档，将不同时间、区域产生的相同数据保存在文档管理系统中，通过不同的用户授权，查看到自己需要的文档。

图书管理系统需求分析文档

图书管理系统需求分析文档一、概论 1、系统背景（1）背景1 大学图书管理系统，图书借阅作为学生教育的培养的重要的一部分，目前越来越多的学校考虑图书馆图书借阅管理，因为图书借阅工作培养模式会让学生学到很多知识以及经验。因此图书借阅的管理也是非常重要且有必要的。所谓21世纪什么都离不开计算机，用自己所学知识，结合身边生活，来完善生活，解决生活问题，这是一个很好的想法。经小组的讨论思考及老师的指导，小组决定建立一个大学图书管理系统网站。（2）背景2 目前图书馆图书借阅的管理很不完善，比如：就如江西师大软件学院为例：学校每天都需要相关值日老师管理图书借阅的工作，工作人员只知道借阅图书的大概情况，许多相关的图书管理等等一系列需要改善的例子。因为已经有学生做出来图书管理系统，但是主要功能是以工作室选方向功能和工作室出勤点到功能为主。因此我们需要一个更为完善的系统网站。二、目标与规划 1、现状分析大家都知道大学的学习对步入大学的学生来说是很重要的一个阶段。学生们的书刊阅读量反映了学生们的学习态度。对于目前学校图书馆的管理，还是存在很多缺陷。就如江西师大软件学院为例：学校每天都需要相关值日老师管理图书借阅的工作，工作人员只知道借阅图书的大概情况，许多相关的图书管理等等一系列需要改善的例子。因为已经有学生做出来图书管理系统，但

是主要功能是以工作室选方向功能和工作室出勤点到功能为主。因此我们需要一个更为完善的系统网站。目前图书管理系统管理网站已有学生做出来了，但系统的侧重点是图书借阅功能。对于此类功能并不能满足用户的其他需求，但是对于已选工作室方向的同学们来说却并不实用。因为该系统未对已选工作室的学生进行需求分析。而我们的网站是针对已经选好方向的学生来说的，它能够更方便的让已选工作室方向的学生和老师进行沟通，更方便的让学生们知道其他工作的进展情况，能够很好的督促大家努力的去学习。 2、建设目标我们的系统旨在方便学生们的借阅、在线阅读和学生们对各个阅读进度的了解以及老师对学生阅读情况的了解和老师对其他安排进度的了解等。一个工程的完成，一个是不能够做到很完善的，则就需要小组一起完成，一起学习沟通合作，要让我们大家感到小组的快乐合作。并完成任务。具体建设目标如下： a．减少对图书管理工作的人力与费用； b．提高处理图书的速度； c．提高图书管理的精度； d．促进教务工作信息化管理。 3、系统拓展系统网站拓展至全省各大高校学院三、系统功能需求功能分析 1、系统可行性分析（1）、技术可行性:技术人员有c#语言做基础，学习采用语言，

文档管理系统详细设计书

档案管理软件子系统模块详细设计说明书

版本历史记录

目录 1.引言 (4) 1.1编写目的 (4) 1.2文档范围 (4) 1.3读者对象 (4) 1.4参考文献 (4) 1.5术语与缩写解释 (4) 2.子系统N详细设计 (4) 2.1子系统概述 (4) 2.2子系统依赖关系 (5) 2.3子系统总体结构 (5) 2.4模块N设计说明 (6) 2.4.1模块描述 (6) 2.4.2功能 (6) 2.4.3*性能 (7) 2.4.4关键算法 (7) 2.4.5模块构成 (7) 2.4.5.1Class 关系图 (8) 2.4.5.2Class构成说明 (8) 2.4.6主要数据结构 (10) 2.4.7界面设计 (10) 2.4.8*尚未解决的问题 (12)

1.引言 1.1编写目的本详细设计说明书是针对档案管理系统而编写的，目的是为开发项目小组提供软件设计需求详细说明，系统功能说明。 1.2文档范围本详细设计说明书只针对档案管理系统有效，是提供档案管理的管理软件。 1.3读者对象预期读者： (1)、项目开发人员。 (2)、软件测试人员。 (3)、软件维护人员。 1.4参考文献 1.5术语与缩写解释 2.子系统N详细设计 2.1子系统概述（1）本软件属于文档管理软件子系统。（2）主要功能是：用户文档查询，文档上传、下载，文档资料共享。

（3）子界面的布局视图： 2.2子系统依赖关系 (1)、子系统依赖于数据库。 (2)、子系统依赖于网络服务。 (3)、子系统依赖于文档信息系统。 2.3子系统总体结构包引用关系图如下所示： ?ui：系统界面部分，负责接受用户输入，显示系统输出，负责其他模块功能的协调调用，并含有站内搜索功能，即在用户指定的已打开的ftp站点中搜索用户需要的资源。ui部分调用common 部分的功能读取xml文件中保存的界面元素属性信息，用户最近访问过的10个ftp信息，用户选择的下载的ftp内容列表及其他需要通过xml文件保存的信息。 ?client：实现ftp客户端的功能，ftp连接，ftp上传及下载：上传或下载用户指定的资源，并返回相应的信息。 ?search:资源实时检索部分，根据用户输入的资源名称关键字，资源类型和选择的检索方式检索用户需要的资源，并验证资源的可用性，返回可用资源及其大小，速度等相关信息。 ?preview：资源预览部分，显示用户选择的资源的部分内容，以使用户决定是否需要该资源。 preview部分调用common部分读取属性文件的内容亦显示预览资源内容的显示格式。逻辑图（组件结构图）如下所示：

ERP、OA、文档管理系统对于企业的主要作用.doc

ERP、OA、文档管理系统对于企业的主要作用7 随着信息技术的不断发展和我国企业改革的不断深入，企业管理方式正在向创新管理和知识管理转变。为适应新时期企业管理方式的变革，企业必须加强管理信息化建设。企业管理信息化建设是一场革命，在提高企业管理水平，促进管理现代化，转换经营机制，建立现代企业制度，有效降低成本。加快技术进步，增强市场竞争力，提高经济效益等方面都有着现实和深远的意义。随着企业建设需求的不断升级，更为简化员工的工作，避免重复工作的，提高办公效率，企业也要对信息化不断升级。首要任务是制定适合我们企业的OA（办公系统）、ERP（业务财务系统）、CRM（客户关系管理系统）、伟创HR（人事系统）、EIP（考勤系统），这些项目管理系统等管理软件在企业内部承担着不同的重任，这些系统可能是在不同时期引入和构建的，一般都来源于不同的软件提供商。尽管我们的企业有这样那样的系统，但随着应用的深入，多系统之间的数据不统一，数据之间缺乏关联性，多系统之间的数据重复维护管理等，成了企业信息化新的困扰，特别是对财务人员的困扰。（当前没有哪家的一个软件就能把企业的所有问题都解决了的，这需要多系统并存，并对多系统进行规划，这也是当前我们很多企业面临的问题）因此，企业系统集成与整合的问题也成很多企业用户必须解决的重要问题。解决这个问题首要的思路是要做到数据的统一性与系统平台的可扩展性，只有这样才利于财务人员的核算和企业

领导的可控性管理。一个ERP系统，动辄上百万，便宜的也要几十万。一些几万块钱所做出的ERP系统，则是漏洞百出，白白浪费企业资金。而且每年高额的维护费，也让一些小企业捉襟见肘。OA虽然相对便宜一些，但是OA的作用更加偏向于管理人员。使人员工作规范化。对于企业运作和办公优化则无太大实质性改变。其实与ERP和OA同为管理系统的，还有一种，叫做文档管理系统。这种系统最大的优点是通用性。它的通用性体现在两方面。一方面是行业的通用，每个行业都可以应用。另一方面是企业发展时期的通用性。不管是刚成立的小公司或是跨国大集团。这个系统都会起到关键的作用。而且全部采用B/S架构，方便企业办公，价格较低，每个企业都可以选择。与OA、ERP并列为当今企业管理的“三大杀手锏”。企业管理可分为管人、管事、管物。OA系统针对于对人员进行约束和管理。在企业中负责管人。ERP系统是整合单位各种流程，使其信息化、电子化。增加工作效率。在企业中管事。剩下的企业资料、信息文档等数据，则是由文档管理系统负责管理。听完朋友的介绍，我私下对文档管理系统进行了了解。文档管理系统发展到2013年，基于B/S架构的文档管理系统已经出现。通过上传到服务器中进行集中存储，管理更加方便，查找更快，而且只要有互联网的地方，就可以通过浏览器直接访问系统。功能众多，包括文档的权限管理、全文搜索、存储加密、审批流程、文档审计、版本管理、规则应用、在线编辑和统计报表等。反观ERP系统。其实是一个流程系统。把企业经营多年的

文档管理系统需求分析

文档管理系统需求分析引言文档管理实际就是文件的制作、修改、传递、鉴定、保存、销毁、存档等一系列操作。文档管理系统是部门经营管理中不可缺少的部分。通过文档信息管理系统，可以实现文档自动化管理的目标，为部门提供了安全、可靠开放、高效的文档管理功能，不仅方便了文档管理系统的日常操作，而且避免了手工管理中的一系列错误的产生，提高了部门的办公效率和部门文件管理的综合测评。目前，大多数文档管理系统在实现了各部门日常文件管理的功能之外，还增设了很多的新功能用以满足文档管理系统电子化、标准化的新要求，例如功能强大的档案查询模块，大大方便了管理者日常文档的查找工作，解决了传统管理中查找困难、耗时等问题。使用现代化的文档管理系统满足了部门的“无纸化”办公的要求，实现了通过计算机对文档管理全程跟踪的目标。文档管理系统的全面应用，克服了部门传统文档管理方法的缺点，提高管理部门的日常办公效率，增强了部门内部协同合作的能力；文档管理系统的应用，方便管理者有效管理文档的同时，大大提高了文档查找效率，进而提高了部门的综合效率。需求分析根据市场需求，要求系统具有以下功能。 ◆处理大量的复合文档型的数据信息。 ◆通过系统查看文档内容和属性。 ◆通过系统可以完成对文档一系列的日常操作。 ◆保证系统的安全性、可靠性。 ◆由于操作人员的计算机操作能力普遍较低，因此要求系统具有良好的人机交互界面。 ◆完全人性化设计，无需专业人士指导，即可操作本系统。 ◆系统具有数据备份及数据还原功能，能够保证系统数据的安全性。主要功能文档管理系统由基本信息、文档管理、系统设置等几个功能模块组成，规划系统功能模块如下。 ?系统设置

文档知识管理系统背景及功能简介

凌峰科技中小企业免费软件应用平台https://www.360docs.net/doc/f318176628.html,完全免费的在线应用软件文档知识管理系统背景及功能简介关键字：文档管理，知识管理，知识档案管理文档知识管理系统,通过建立统一的标准，规范整个文件管理，包括规范各业务系统的文件管理；构建完整的档案资源信息共享服务平台，支持档案管理全过程的信息化处理，包括：采集、移交接收、归档、存储管理、借阅利用和编研发布等等，同时逐步将业务管理模式转换为服务化管理模式，以服务模型为业务管理基础，业务流和数据流建立在以服务为模型的系统平台之上。文档知识管理系统，为企事业单位的文档知识现代化管理，提供完整的解决方案，档案管理系统既可以自成系统，为用户提供完整的文档知识管理和网络查询功能，也可以与本单位的OA办公自动化和DPM设计过程管理，或者与MIS信息管理系统相结合，形成更加完善的现代化信息管理网络。作为一套完整的文档知识管理系统，必须具备以下功能： (1) 文档管理：文档维护、我的待提、文档审核、文档删除、文档回收站、文件归档、版本更新 (2)知识管理：知识管理、我的待提、知识审核、知识删除、知识回收站 (3)文档浏览统计：按分类浏览、按人员浏览、文档库浏览、分类统计、人员统计、状态统计 (4)知识浏览统计：按分类浏览、按人员浏览、知识库浏览、分类统计、人员统计、状态统计 (5)基础设置：文档库设置、知识库设置 (6)权限设置：知识库管理权限、文档库管理权限具备上述功能的文档知识管理系统，可以满足日常管理的需要，为此，我们参考的很多的管理软件。其中一些系统是CS结构，在BS软件大行其道的今天，CS软件的弊端也日趋呈现，BS的优势也备受用户的青睐，例如地址为https://www.360docs.net/doc/f318176628.html,的凌峰科技文档知识管理系统。采用BS结构，一次部署则所有客户端均可使用。更新方便，不会存在有些客户端遗漏更新的问题。您的企业，还在进行纯手工的文档知识管理吗？那您已经落后了很大一步。根据自己的业务需求，购买或定制一套适合自己的管理软件，替代人工是最佳选择。而且，计算机软件具有存档清晰，查询方便，管理简单，节省人工等优势，在计算机管理大行其道的今天，当即决策，迅速融入时代发展的大潮才是一个企业可持续发展的必然选择。参考百度百科：https://www.360docs.net/doc/f318176628.html,/view/7792063.htm 免费软件平台,免费人力资源管理系统,免费活动日历管理系统,免费客户关系管理系统,免费日常办公OA 系统,免费知识档案管理系统,免费低值易耗管理系统,免费设备管理系统,免费网上报销系统

文档管理系统

文档管理系统一、实验目的面向对象分析与设计课程其目的在于促进学生复习和巩固计算机软件设计知识，加深对软件设计方法、软件设计技术和设计思想的理解，并能运用所学软件设计知识和面向对象技术进行综合软件设计，提高学生的综合应用能力。通过这次综合题目，要掌握UML（统一建模语言），并能运用UML在Viso中建模。二、实验要求面向企业用户，研制开发一套文档管理系统，实现企业文档的存储、分类、维护、检索、授权等过程的全面管理。为用户主要提供如下功能： 1）登陆：用户通过浏览器登陆到系统，输入用户名和密码，登陆到系统，看到本用户所能看到的各类信息，包括文档分类树、文档的基本信息等。 2）人员组织角色管理与授权管理：创建和维护企业的人员、组织和角色，人员具有登陆名、名称、密码、邮件、手机等一些基本的属性，人员从属与一个或多个组织，具有一个或多个角色，组织间具有层次关系。提供文档按照人员与角色两种方式的授权模式。 3）文档分类管理：用户可以增删改文档的分类，文档分类间可以建立层次关系。 4）文档维护：用户可以增删改文档，文档包括基本的描述信息（如文档编号、文档名、文档创建时间、创建人、大小等）及文档对应的文件列表。 5）文档检索：用户可以方便的按照文档的名称、编号、创建时间、创建人等信息进行检索。三、实验内容（1）结构化分析准则，需求分析过程应该建立3种模型 1、实体-联系图，描绘数据对象及数据对象之间的关系，是用于建立数据模型的图形。

2、数据流图，描绘当数据在软件系统中移动时被变换的逻辑过程，指明系统具有的变换数据的功能，因此，数据流图是建立功能模型的基础。 3、状态图，指明了作为外部事件结果的系统行为。为此，状态转换图描绘了系统的各种行为模式和在不同状态间转换的方式。状态转换图是行为建模的基础。 1)文档分类信息状态图

系统文档管理的意义

系统文档管理的意义是什么？在管理信息系统开发的整个过程中会形成很多的文档资料，包括工作文档和技术文档。这些文档资料是未来进行系统维护或升级所必须的。文档管理是管理信息系统项目管理中非常重要的一部分工作。在文档管理方面，目前还没有统一的标准。但是，在实践过程中，人们已经认识到了管理信息系统文档管理的重要意义，并且已开始体现在管理信息系统的项目管理工作中。 ERP的发展历程是什么？ ERP是Enterprise Resource planning的缩写，意为企业资源管理计划信息系统。简而言之， ERP是面向电子商务对企业的产、供、销、存、人、财、物各系统资源进行全面管理的管理信息系统。ERP是管理信息系统在20世纪90年代的最新发展。ERP的发展经历了MRP，MRPⅡ和 ERP三个阶段。这三个发展阶段相互之间不是孤立的，而是呈一个向上发展的趋势，前一个阶段是后一阶段的基础，后一个阶段是前一阶段的深化和发展，ERP汇总了MRP和MRPⅡ的优点，又结合了最新的Internet技术，从而发展为功能更为完善的管理信息系统，换言之，ERP在MRP和MRPⅡ的基础上，实现了通过网络信息面向供需链的管理信息集成。 U/C矩阵的作用是什么？ “U/C”矩阵用于划分子系统，也用于数据分析中，检查数据与业务功能的匹配情况。U/C矩阵：是描述企业过程和数据之间关系的一种矩阵。每一行为一个企业过程，每一列为一种数据类，若某过程产生某数据类，则矩阵中标记为“C”；若某过程使用某数据类，则矩阵中标记为“U”。业务流程图的特点是什么？表明系统内各单位、人员之间业务关系、作业顺序和管理信息流动的流程图。特点：形象地表达了管理信息中的流动和存储过程，但仍没有完全脱离一些物质要素（如货物、产品等）〃

酒店管理系统功能模块介绍

酒店管理系统功能模块简介实时房态 Δ直观显示房间状态，并且可以对房间直接进行登记、结账等操作。 1 、将预定、收银、接待、咨询工作整合在一起，实现一站式服务。接待人员可轻松解决客人需求，有效的提高工作效率2 、预定时提供准确的房间状态，可轻松预知未来房态，大幅度提高客房使用率 3、客户入住时如果是熟客自动调出客户资料，轻松快捷的实现客人入住 4、特殊的黑名单管理机制，可及时提醒接待人员在黑名单用户入住时采取有效的措施 5、配套身份证、门锁接口，开房仅需20秒(登记客人信息、打印押金单、发房卡) 预定管理管理散客或团体客户的预订信息接待管理接待散客或团体入住。并可以进行预订转接待、入住状态变更等操作。收银结账灵活准确的结算方式 1、收押金、结账退房，支持多种支付、结算方式(现金、会员卡、银行卡、免单、挂账签单、) 2、客房商品部分结算、反结、走结

查询报表对预订、入住、商品销售、客人信息、客人账务等等数据明细、汇总查询账务管理账务核查、实现前台数据的统计，如营业日报表、交班对帐数据统计、收银查询 , 当日结帐查询 , 催帐报表等等会员管理设置会员参数，建立会员卡号以及会员卡的基本操作(支持积分、短信、积分兑换礼品等) 1、支持市场上所有常见的卡类和卡设备 2、会员积分、折扣、储值三卡合一 3、支持会员卡状态管理，轻松解决卡挂失、卡作废、补卡、退卡等操作协议客户管理办理签订协议，对协议客户帐务查询管理，对客户挂帐进行结算 ◇系统提供协议客户管理功能，可根据实际业务设置相应的协议客户，并可针对不同的协议客户设定不同的协议价格。同时不同的协议客户在不同的时期可灵活地设置不同的协议价格和挂帐限额，确保系统能更有效的与实际业务相结合客房管理设置客房状态，处理客房内基本物品营销管理提供出租率、房型、房价销售分析，时间段开房率等数据分析，为酒店提供营销活动最终端有效数据库存管理小型进销存管理系统，与客房无缝对接，电脑自动冲减库存，帮您实时了解库存情况，知道明天要进什么，又该进多少。茶吧营业

文档管理系统设计(综合)

文档管理信息系统设计题型：选择题、填空题、名词解释、综合题（简答、论述、画图、编程） 1、E-R图概念设计： 2、根据E-R图写出关系表逻辑设计： 1）档案条目关系表档号分类号题名主题词责任者密级… 11.23.7.4 AC02 xxxxxx xx …… 2）档案管理员关系编号姓名性别职务 G01 xxxxx 男档案处副处长 …… 3）档案利用者关系用户号姓名性别职务单位借阅时间 Y01 xxxx 男工程师设计院2000.7.26 …… 4）档案主题词关系表代号主题词同义词词间关系拼音注释 M1 计算机电脑代用jsj

5）档案分类法关系表类号类别参照类注释 M12 机械 6）档案管理员-档案条目联系表编号档号 G01 11.23.7.4 ……. 7）档案利用者-档案条目联系表用户号档号 Y01 11.35.7.4 ……. 8）档案主题词-档案条目联系表代号档号 M1 11.35.7.4 9）档案分类法-档案条目联系表类号档号 M12 11.21.5.3 …… 3、典型档案管理系统菜单设计（一级菜单、二级菜单）（1）、数据：文件、案卷、字典、退出（2）、检索：组合、提要、分级（3）、借阅：借阅登记、打印调卷单、查询催还、打印催还单、归还登记、登记表修改（4）、统计：文献分类、文献借阅、案卷目录、收文发文（5）、立卷：立卷整理预处理、按组织机构立卷、按有关问题立卷、按用户定义立卷（6）、编目：分类号编目、责任者编目、主题词编目、自定义编目（7）、打印：案卷目录打印、案卷封面打印、卷内目录打印、著录卡片打印、专题目录打印、借阅目录打印、收文发文打印（8）、维护：数据库备份、数据库恢复、系统设置、系统修复、初始化设置、数据库索引（9）、其它：数据转存、数据补充、文档扫描、系统帮助 4、自动著录标引（主程序、子程序）（试编程实现：根据题名提取主题词的功能）（1）、j_ztc.prg set defa to d:\abc sele 1 use maincopy.dbf sele 2 use dict_ztc sele 1 do while .not. eof()=j_ztc_a(maincopy.tm) sele maincopy skip 1 enddo

电子档案管理系统基本功能规定

电子档案管理系统基本功能规定第一章总则第一条为推动电子档案科学管理，规电子档案管理系统建设，明确电子档案管理系统基本功能，确保电子档案真实、完整、可用与安全，按照国家有关法律法规和标准规，制定本规定。第二条本规定所称电子档案管理系统，是指档案机构运用信息技术手段对电子档案进行接收、整理、保存和提供利用的计算机软件系统。第三条本规定明确了电子档案管理系统（以下简称系统）必备的功能。系统建设应依据先进、实用、安全、发展的原则。第四条本规定适用于国家各级各类档案馆，机关、团体、企事业单位可参照执行。第二章系统总体要求第五条系统结构应具备开放性，可实现与其他系统的功能集成、数据共享与交换。第六条系统功能应具备可扩展性，应满足当前及可预见的时间的业务

需求，可方便地进行功能扩展。第七条系统实现应具备灵活性，支持电子档案管理的业务模式、工作流程和数据结构等的灵活定义与部署。第八条系统运行应安全可靠，保存电子档案管理关键业务过程记录，根据需要采取电子签名、数字加密和安全认证等技术手段，保障电子档案安全，防止非授权访问。第九条系统应依据电子档案保存和利用的业务要求分别建立相应数据库。第十条系统应能够管理符合国家、行业标准规定的多种门类、多种格式的电子档案。第十一条系统应具备对实体档案进行辅助管理的功能。第三章档案接收第十二条系统应具备电子档案接收功能，支持在线和离线的批量接收与处理，保存移交接收处理记录。第十三条系统应具备对电子档案的数量、质量、完整性和规性等进行

检查的功能，对不合格的进行标注。第十四条系统应具备对检查合格的电子档案进行登记的功能，支持电子档案数量的清点、容和元数据有效性的验证，赋予电子档案唯一标识。第十五条系统应具备对征集档案进行管理的功能。第四章档案整理第十六条系统应具备电子档案的自动归类与排序等功能，支持分类与排序的调整处理。第十七条系统应具备电子档案的著录、标引等功能，形成电子档案目录，并与电子档案相关联。第十八条系统应具备电子档案批量格式转换的功能，生成符合国家、行业相关标准的用于长期保存和提供利用的电子档案。第十九条系统应具备维护电子档案各组成部分及相关数据信息之间、电子档案与电子档案之间的关联功能。

企业文档管理系统

编号：审定成绩： *********学院2011届毕业设计（论文）题目：企业文档管理系统分院：软件工程分院学生姓名：********* 专业：软件设计与开发班级：********* 学号：********* 指导教师：********* 填表时间：2010年10月 *********学院

摘要本文所研究和设计的制造企业技术文档管理系统，是根据当前我国国内制造业行业发展的需求，吸取国外成功应用的经验，在经过充分的对制造业行业情况的调查研究和分析，设计了这个管理系统，其中主要包括技术专利子窗口，技术标准子窗口，文献子窗口，通过对这三部分信息的有效管理，从而为各制造业组织在技术发展和革新方面提供更快更新的信息，使之能及时改进生产线，跟进生产标准，提高生产效率，并迅速提升组织管理层的管理效率。《文档管理毕业设计》是采用VISAUL BASIC6.0开发的一个数据库管理毕业设计?本设计说明书主要讲述了VISAUL BASIC6.0的基本功能及设计方法?紧接着以本毕业设计为例,逐一介绍开发本毕业设计毕业设计的步骤:毕业设计分析?毕业设计设计?毕业设计实现?毕业设计维护?在毕业设计分析中先后用数据流图?数据字典?毕业设计的功能结构图分析了毕业设计所需的各种数据?在毕业设计的设计中,详细的展现了毕业设计的各个功能模块?所需的数据库表及表字段?菜单的设计等?在毕业设计的实现中,给出了实现表单中相应的功能控件的事件及代码?以及菜单实现的方法?文章的最后则给出了本毕业设计的主要功能源代码? 本毕业设计具有数据输入,数据存储,信息查询,报表打印等功能,毕业设计的人机对话界面友好?毕业设计功能全面,用户操作方便是本设计的一个特色? 关键词：技术文档管理系统、技术专利子窗口、技术标准子窗口、文献子窗口ABSTRACT、面向对象、文档、管理毕业设计、VB

文档管理系统-安全控制功能

安全控制严格的权限管理任何一份文档都会有一定的使用范围和不同用户的使用权限。对此，易度文档管理系统提供委托管理、成组授权、权限继承、负授权、四层6级别查看人的权限。根据用户的不同等级、所属部门进行严格的权限划分，分别控制用户的文件查看、下载、上传、修改、复制、移动、删除、发布等权限，从而保证文档在使用过程中的安全。授权委托管理系统支持授权委托管理。可单独针对各个文件夹，指定文件夹管理员，文件夹管理员在该文件夹下拥有全部管理权限，可实现真正的权限委托管理，分离内容管理员和系统管理员，减轻管理员的负担，增强系统的可管理性。

权限继承易度文档管理系统提供权限继承机制，保证用户在拥有父文件夹管理权限的同时，也将拥有所有子文件夹的管理权限。成组授权可针对某个部门、某个岗位进行授权。这样新人到岗，只需指定所在岗位，便可自动得到相应的文档访问权限。成组授权操作简单，只需在权限操作中按群组进行权限设置即可，大大减轻管理的负担，也可做到控制文档的安全。

负授权系统支持“负授权”，也就是可以禁止某个人的权限。这个技术结合成组组授权，可实现如下的逻辑：开发部除了张三都能够查看某个文件。“负授权”技术，使授权更灵活，更实用。充分保障知识文档在共享、使用过程中的安全性。四层6级别查看人系统支持四层6级别查看人角色权限，通过不同的角色权限，可以控制文档预览、添加、编辑、移动、复制、下载等权限。

不同级别查看人拥有不同的权限。如下表所示文档的保密性控制系统具备文档保密性控制功能，保护核心文档。文档设置保密后，一般人员将无权进行查看，保证文档的安全性，只有文件夹的管理人、超级查看人、文件的订阅人才可以看到相应的文档。同时支持在文件上传过程中根据用户需要选择是否对文档进行保密操作。