【cl9】Characterization of high cycle fatigue behavior of a new generation aluminum lithium alloy

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840D货车车轮CL60钢在300℃下的低周疲劳特性

初期，试样承受的拉压应力幅基本对称；循环末期，拉应力急剧降低，样产生了失稳断裂；了时试终
的循环应力应变曲线反映出了典型的瞬断特征．因此，必要从断口处进一步研究其微观断裂有
机理．
关键词：车车轮；Ｌ０钢；周疲劳；货Ｃ６低断裂中图分类号：Ｇ１．５Ｕ７．３Ｔ１３２；２０３文献标志码：Ａ
ｄｒｇｂａｉｇｐｏｅｓｈｃｅｎｓｔｇ－ｍｅａｕｅｌｗｃｃａｉｕＬＦ．Ｉｈｓｐｐｒｕｉｒｋｎｒｃｓ，ｗｉｂｌｇｏＨｉｈｔｐｒｔｒｙｌｆｔｅ（Ｃ）ｎｔｉａｅ，ｎｈｏｅｏｅｇ
Ｈｉｈｔｍｐｒｔｒｇ —ｅｅａｕｅＬＣＦｅｔｆＣＬ６ｔｅｏｒｉｈｔｔｓｓｏ０ｓｅｌｆｒｆｅｇｗｈｅｒｏｄｕｔｄａ００Ｃ．ｔｗａｏｄｅｌｗｅｅｃｎｃｅｔ３ｏＩｓｆｕｎｔａｈｅｉｅｓｒｓｎｏｒｓｉｅｓｒｓｍｐｉｕｅｒｙｍｍｅｒｃｎｔｅｗｈｏｅｄｒｎｎｔａｈｔｔｅｔｎｓｌｔｅｓａｄｃｍｐｅｓｖｔｅｓａｌｔｄｓｗｅｅｓｔｉａｏｈｌｌｕｉｇｉｉｉｌｓａｅｏｙｌｎｔｇｆｃｃｉｇ，ｗｈｌｈｅｔｎｓｌｔｅｓｄｃｅｓｄｄａｔｃｌｕｒｎｇｆｎｌｓａｅｎｏｌｐｓｕｔｒｉｔｅｉｅｓｒｓｅｒａｅｒｍａｉａｌｄｉｉａｔｇ，ａｄｃｌａｅｒｐｕｅｅｙｏｃｒｄｉｈｅｓｍｐｅ．Ｔｈｅｆｎｙｌｎｔｅｓｓｒｎｃｖｌｏｒｆｅｔｄｔｐｃｌｆａｕｅｆｉｔｎａｃｕｒｅｎｔａｌｉａｃｃｉｇｓｒｓ —ｔａｕｒｅａｓｅｃｅｙｉａｅｔｒｓｏｎｓａｔ ‘ ｌｉｌｎｏｕｔｒｅｎｓｒｐｕｅ．Ｉｓｓｇｅｔｄｔａｕｔｅｅｅｒｈｓｏｌｅｄｎｎｔｒｃｕｅｓｒａｅｔｎｄｏｔｉｕｇｓｅｈｔｆｒｈｒｒｓａｃｈｕｄｂｏｅｏｈｅｆａｔｒｕｆｃｏｆｕｔｉ

基于Ls-Dyna软件2种材料模型的碳纤维复合材料层合板面内剪切有限元仿真

2020年12月第44卷第12期Vol.J4No.12Dec.202() MATERIALS FOR MECHANICAL ENGINEERINGDOI：10.11973/jxgccl202012016基于Ls-Dyna软件2种材料模型的碳纤维复合材料层合板面内剪切有限元仿真孟宪明'，钟正S程从前2,曹铁山S赵杰2,黄亚烽-吴瑶2(1.中国汽车技术研究中心有限公司，天津300300；2.大连理工大学材料科学与工程学院，大连116024)摘要：通过准静态单轴拉伸试验和面内剪切试验获取力学性能参数，采用Ls-Dyna软件中的纤维增强复合材料渐进损伤模型和复合材料层合板连续损伤模型模拟碳纤维复合材料层合板在面内剪切载荷作用下的力学响应和破坏模式，对比了2种模型的适用性。

结果表明：在面内剪切过程中的初始线弹性阶段,2种模型都能较好地模拟出碳纤维复合材料层合板的力学特性。

随着载荷的持续增大，渐进损伤模型的载荷-位移仿真曲线依旧呈线性上升，到达载荷峰值后迅速下降，与试验曲线存在很大偏差；连续损伤模型由于引入了损伤参数，当材料出现损伤后.其载荷-位移仿真曲线呈非线性，与试验曲线吻合良好。

关键词：碳纤维复合材料；连续损伤模型；渐进损伤模型；损伤参数中图分类号：TB332文献标志码：A文章编号：1000-3738(2020)12-0085-06Finite Element Simulation of In-plane Shear of Carbon Fiber ReinforcedPlastic Laminates with Two Material Models of LS-DYNA SoftwareMENG Xianming1.ZHONG Zheng2.CHENG Congqian2,CAO Tieshan2.ZHAO Jie2,HUANG Yafeng*,WU Yao2(1.China Automotive Technology&Research Center Co.,Ltd.,Tianjin300300,China；2.School of Materials Science and Engineering,Dalian University of Technology»Dalian116024,China)Abstract:The progressive failure model of fiber reinforced plastics and the continuous damage model of composite laminate of the Ls-Dyna software were applied to simulate the mechanical response and damage modes of carbon fiber reinforced plastic laminates under in-plane shear loads,with the mechanical parameters obtained by quasi-static uniaxial tensile and in-plane shear tests.The applicability of the two models was compared.The results show that in the initial linear elastic stage during in-plane shearing,the two models could simulate the mechanical characteristics of the carbon fiber r&nforced plastic laminates.As the load continued to increase,the loaddisplacement simulation curve obtained by the progressive failure model still rose linearly,and dropped rapidly after reaching the load peak；the simulation curve had a large deviation from the test curve.When the material was damaged,because of the introduction of damage parameters,the load-displacement simulation curve obtained by the continuous damage model was nonlinear,which was in good agreement with the test curve.Key words:carbon fiber reinforced plastic；continuous damage model；progressive failure model；damage parameter收稿日期：2020-08-05；修订日期：2020-11-27基金项目：国家重点研发计划“新能源汽车”重点专项项目（2O16YFBO1O16O2）作者简介:孟宪明（1980—）,男，山东济南人，高级工程师•博士通信作者:赵杰教授0引言碳纤维复合材料（CFRP）作为一种比强度高、比刚度高、耐腐蚀性能较强的轻量化材料，广泛应用于汽车、航空航天、军工武器、高速动车等方面口切。

雅思真题第一册阅读翻译A

雅思真题第⼀册阅读翻译A Workaholic Economy1.FOR THE first century or so of the industrial revolution, increased productivity led to decreases in working hours.因为公元⼀世纪或是那些⼯业发展，增长了⽣产⼒导致⼯作时间的下降。

2.Employees who had been putting in 12-hour days, six days a week, found their time on the job shrinking to 10 hours daily, then, finally, to eight hours, five days a week.那些每天⽤12⼩时⼯作，⼀周⼯作6天的被雇⽤者发现他们⼯作的时间缩短到每天10个⼩时，然后，最终到8⼩时，⼀个星期5天。

3.Only a generation ago social planners worried about what people would do with all this new-found free time.只有上⼀代的社会规划者担⼼⼈们将要如何处理这些新找到的⾃由时间。

4.In the US, at least, it seems they need not have bothered.在美国，⾄少，似乎他们需要不被打扰。

5.Although the output per hour of work has more than doubled since 1945, leisure seems reserved largely for the unemployed and underemployed.尽管每个⼩时⼯作输出都⽐1945年以来的两倍还多，空闲似乎主要都留给失业⼈员和未充分就业的⼈。

复合细化超细晶纯钛的低周疲劳行为

复合细化超细晶纯钛的低周疲劳行为
纯钛的综合性能良好,作为结构材料,由于强度低,限制了其应用, 为了提高纯钛的强度和疲劳寿命,进一步扩大其应用范围,本文采用ECAP+旋锻复合细化工艺制备超细晶纯钛。利用扫描电子显微镜、透射电子显微镜、室温拉伸力学性能测试以及室温低周疲劳试验等方法,研究ECAP+旋锻复合细化超细晶纯钛在总应变幅为0.5%1.1%范围内的室温低周疲劳行为。
主要结论如下:纯钛经ECAP+旋锻复合细化工艺变形后,晶粒显著破碎,获得了平均晶粒尺寸约为200 nm的等轴状超细晶组织,其屈服强度为758 MPa。对ECAP+旋锻复合变形的超细晶纯钛和原始纯钛进行了应变控制的室温低周疲劳试验,结果表明:超细晶纯钛的室温低周疲劳寿命是原始纯钛的23倍。
在低周疲劳过程中,因局部产生宏观塑性变形,故超细晶纯钛的循环应力与应变之间的关系不再呈现直线关系,符合低周疲劳的一般特征。超细晶纯钛的循环应力应变的具体表达式为:Δ σ /2 （28）656.577（7）Δ ε p/2（8） 0.08672超细晶纯钛的低周疲劳变形机理为位错滑移机理,在较低总应变幅下,疲劳断裂类型为混合断裂,在较高的总应变幅下,断裂方式为解理断裂。
而原始纯钛在总应变幅较小时,其低周疲劳变形以位错滑移机理为主导;总应变幅较高时,其低周疲劳变形以孪生变形机理为主导。原始纯钛的疲劳断裂类型为混幅的增加,疲劳寿命减小, 其塑性应变能增大。总应变幅与发生疲劳失效时载荷的反向次数（2Nf）之间的关系符合Manson-Coffin公式。

Particle erosion on CNF coated CF composites

Particle erosion on carbon nanoﬁber paper coated carbon ﬁber/epoxycompositesNa Zhang a ,b ,1,Fan Yang a ,1,2,Changyu Shen b ,Jose Castro c ,L.James Lee a ,⇑aDepartment of Chemical and Biomolecular Engineering,The Ohio State University,OH 43210,USA bDepartment of Materials Science and Engineering,Zhengzhou University,Zhengzhou 450052,China cDepartment of Integrative Systems Engineering,The Ohio State University,OH 43210,USAa r t i c l e i n f o Article history:Received 2October 2012Accepted 1May 2013Available online 15May 2013Keywords:A.Carbon ﬁberB.WearC.Finite element analysis (FEA)D.Electron microscopya b s t r a c tCarbon ﬁber (CF)woven fabric (52%by weight)reinforced epoxy composite and carbon nanoﬁber (CNF,12%by weight)paper coated on the surface of the CF/epoxy composite were fabricated by resin transfer molding (RTM).The surface erosion characteristics of molded CF composites were investigated by sand erosion test using silica particles with a size around 150l m as the erodent.The eroded surfaces were examined by scanning electron microscopy (SEM)and weight loss.The CNF paper was able to provide a much stronger erosion resistance compared to the CF reinforced epoxy composites,which is attributed to the high strength of CNFs and their nanoscale structure.Finite element (FE)computer simulations were used to qualitative interpret the underlying mechanisms.Ó2013Elsevier Ltd.All rights reserved.1.IntroductionPolymer composite materials often exhibit poor erosion resis-tance [1–6].Improving erosion resistance of light weight compos-ite materials is crucial for many industrial applications such as wind turbine blades [7–9].Tilly [3–5,10]presented a thorough analysis of various parameters affecting erosion,including particle properties,impact parameters,particle concentration,type of rein-forcement and temperature.For erosive wear resistance,materials can be classiﬁed into ductile and brittle categories according to their behavior with respect to the impinging angle and erosion process [12].In brittle erosion,the weight loss increases linearly with time,while in a ductile type the particles may be embedded in the target surface causing a weight gain initially,followed with a linear weight loss as a function of time by further impingement.The maximum weight loss was found at about 90°and 30°impact angles for brittle and ductile erosions,respectively [10–12].Both glass ﬁber and carbon ﬁber reinforced epoxy composites show brittle characteristics [12–15].In this study,we present a new approach for improving the erosive resistance of composites using a thin protective layer of paper made of carbon nanoﬁbers (CNFs)on the composite surface.A series of sand erosion experiments were carried out to compare the particle erosion performance of CF based composites with and without surface protection by the CNF puter simulations of ﬁnite element (FE)meth-od were used to explain the underlying mechanisms for the ob-served performance difference between the two composites made of microscale CFs and nanoscale CNFs.2.Experimental 2.1.MaterialsThe CNF used in this study was a vapor grown carbon nanoﬁber,Pyrograf Ò-III (PR-24-XT-HHT),obtained from Applied Sciences Inc.(Cedarville,OH).The length of CNFs is about 30–100l m and the average diameter is about 100nm.The carbon ﬁber woven fabric used in this work was an IM7-12k,5harness,370g/m 2fabric obtained from Textile Industries,Inc.An epoxy resin,EPIKOTETM RIM 135with an epoxy equivalent weight (EEW)of about 166–185,and a diamine curing agent,EPIKURETM RIM H 137with an amine value of about 400–600mg [KOH]/g,were provided by Hexion Specialty Chemicals (Houston,TX).This is a low tempera-ture and low viscosity resin designed for manufacturing wind tur-bine blades.Silica sand,blocky,sharp edged green particles with a size about 150l m and a hardness of 2600Knoop were selected as the erodent.A scanning electron micrograph of the silica sand is shown in Fig.1.1359-8368/$-see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/positesb.2013.05.003Corresponding author.Address:The Ohio State University,125A Koffolt Laboratories,140West 19th Avenue,Columbus,OH 43210,USA.Tel.:+16142922408;fax:+16142923769.E-mail addresses:zhangna163163@ (N.Zhang),yangyangyang99@ (F.Yang),shency@ (C.Shen),castro.38@ (J.Castro),lee.31@ (L.J.Lee).1These authors contributed equally to this work.2Present address:Department of Mechanical and Industrial Engineering,Univer-sity of Toronto,Toronto,ON,Canada M5S 3G8.2.2.Fabrication of CNF nanopaper and CNF nanopaper coated glass ﬁber/epoxy compositesA vacuum ﬁltration technique was used for preparing the nano-paper.In this set up,a 90mm diameter glass ﬁlter holder with a stainless steel screen membrane support was placed over a conical ﬂask.Once the hydrophilic polycarbonate membrane ﬁlter with a pore size of 0.4l m (Millipore Inc.)was placed plain ﬂat in the set up and clamped,it was connected to a vacuum aspirator pump.The nanoparticle solution was prepared as follows:the CNF parti-cles were dispersed in deionized (DI)water and sonicated using a Branson Digital Soniﬁer [(S450D),75%amplitude]for 30min.The resulting suspension was cooled down for 30min in a refrigerator and sonicated for 30sec again,then ﬁltered through the ﬁltration set up previously described under a pressure of $400kPa.Vacuum was applied for about 20min after all the water was ﬁltered away.The CNF nanopapers were dried overnight at room temperature.The thickness of CNF nanopapers was 0.28±0.02mm with a poros-ity of 94%.Vacuum assisted resin transfer molding (VARTM)was used to impregnate the CF and CNF nanopaper coated CF preforms,which consisted of three layers of CF fabrics with andwithout a single layer of CNF nanopaper.The performs were placed and sealed a vacuum bag.Before mold ﬁlling,vacuum was applied to force the bag to press tightly against the ﬁber stack.The epoxy mixture was degassed in a vacuum chamber for 15min,and the resin was introduced into the ﬁber preforms.The samples were cured room temperature (around 25°C)for 24hr and post-cured 80°C for an additional 15hr.The CF and CNF nanopaper contents in the composites were controlled at 52and 12wt.%,respectively,measured by a thermo-gravimetric analyzer (TGA).2.3.Particle erosion testRectangular samples of size 12.5Â80mm molded composite plaques for the erosion epoxy and CNF/epoxy composites showed brittle with the maximum erosion rate at normal impinging angle was chosen as 90°in this frame with a rectangular opening was placed the test specimens to keep the eroded area The conditions under which the erosion are listed in Table 1.A standard test procedure each erosion test.Before testing,the samples were burnished to re-move the pollutants from the sample surface.After each test,spec-imens were degreased with acetone,dried in a jet of cold air and weighted with a precision balance (Explore,ep214C).The weight loss by sand abrasion (with an accuracy of 0.1mg)was used to quantify the erosion resistance.Each data point was obtained from the average value of ﬁve measurements.Scanning electron microscopy (SEM)images were collected using a ﬁeld emission scanning electron microscope,Hitachi S-4300(Tokyo,Japan).The samples were gold-sprayed to reduce charging of the surface.3.Finite element simulationTo investigate the mechanisms of particle erosion,Finite ele-ment (FE)simulations were carried out for CF/epoxy composites with and without CNF nanopaper coating.It is difﬁcult to track the actual erosion process which involves a large number of colli-sion events.Most of the existing work simulated only one or a few particle collision events [16–20].However,the trend can still be obtained for the erosion rate as a function of various parameters such as impinging angle,velocity,and target properties [16,19].In this study,one collision event with periodically distributed par-ticles was simulated.Qualitative comparisons were made between the experiments and the simulations.This study aims at providing insights into the mechanisms underlying the particle erosion per-formance of CF and CNF reinforced epoxy composites.Three-dimensional simulations were carried out using the gen-eralized FE codes ABAQUS/EXPLICIT version 6.9.Fig.2illustrates the conﬁguration for the simulation of CF/epoxy composite.The eroding particles were simpliﬁed as spheres which were projected to the target surface in periodic arrays.The CF woven fabric has an Fig.1.Scanning electron micrograph of silica sand particles.Table 1Erosion test conditions.Impingement angle (°)90Impingement area (mm 2)600Impingement time (s)15Erodent feed rate (g/min)453.4Test temperature (°C)20Nozzle to sample distance (mm)25.4Nozzle diameter (mm)8Air pressure (MPa)0.47Fig.2.FE conﬁguration of the particle erosion on surface of CF/epoxy composite.Part B 54(2013)209–214Fig.3a.The diameter of the eroding particle is0.15mm according to the experiments.The diameter of the CFs is adjusted so that the carbon content is52%by weight,consistent with experiment mea-surements.The model contained117,153linear solid elements with reduced integration(type C3D8R).Fig.3b shows the RVE for the CNF nanopaper.The dimensions are the same as the CF/epoxy case except the coating thickness,for which a smaller value of 0.05mm was applied.Utilizing the geometric symmetry,the RVE for CNF nanopaper only needs to contain one fourth of the conﬁg-uration of that for CF/epoxy composite.The right graph in Fig.3b is a magniﬁcation of theﬁber skeleton for a small portion of the CNF nanopaper model.Since the randomly interweavedﬁber conﬁgura-tion in experiments cannot be easily constructed in meshing,a uni-formly distributed orthogonal frame of beams is used instead to represent the highly interlaced CNF network.A square cross sec-tion instead of a circular section is used for CNF for simplicity. Theﬁber diameter of CNF in simulation is chosen as0.5l m which is larger than that observed in the experiments.This is because thinner CNFs would needﬁner mesh and hence more computa-tional expense.In spite of this,a large number of elements are needed due to the huge difference between the CNF diameter and the dimension of simulation RVE which depends on the size of eroding particles.The CNF inter-space is chosen as2.82l m so that the carbon content would be12%by weight in the nanopaper, consistent with our experiments.The obtained model contains 1,060,428C3D8R elements,corresponding to more than100CPU hours for a typical run on a2.6GHz computer for3l s of simula-tion time.Although this simpliﬁed model is different from the actual composites,we expect that it can provide qualitative inter-pretation of the experimental observations.Periodic boundary conditions are applied on the lateral bound-aries by coupling the degrees of freedom of the corresponding nodes on the opposite faces using the linear equations for CF/epoxy version2.1.For all conﬁgurations the mesh is reﬁned near theimpinging location so that the eroded mass could be accuratelycaptured.The silica particles are modeled using the linear elastic constitu-tive law.While epoxy,CF and CNF are modeled using the elastic–plastic constitutive law with linear isotropic hardening.The mate-rial parameters are listed in Table2[22–25],where q is the density, E is the Young’s modulus,v is the Poisson’s ratio,r y is the yield stress,E is the Young’s modulus,E p is the hardening modulusand r s is the material strength.The physical meaning of the parameters can be revealed by the stress–strain(r–e)relation for uni-axial stretch deformation in small deformation range as in Eq.(1).e¼rE;r<r yrþrÀr yp;r P r y(ð1ÞIt can be seen from Table2that the plastic strain set is very small,reﬂecting the brittle property of these materials.In order to model the erosion of the target materials,a criterion is needed for the element removal.For the brittle erosion,the mass removal is caused by the spalling mechanism involving the evolu-tion of micro-cracks,which is very difﬁcult to model by the FE method.Some researchers used Johnson–Holmquist model and the corresponding equation of state to model the failure behavior of the brittle materials[21].However,the large amount of ele-ments and the multi-phase properties of composites would cause huge computational expense if complex models are applied.There-fore a simpliﬁed criterion based on equivalent stress is applied here for the element removal.The element is removed once the equivalent stress r at its integration point reaches the critical value r cri as in Eq.(2).Here r0is the deviatoric stress tensor, r cri is cho-sen as the material strength r s.This criterion can be simply imple-mented in the dynamic shear failure option available in ABAQUS/Computational RVEs with mesh for(a)CF/epoxy composite and(b)CNF nanopaper.The inset graph shows the enlarged view of the skeleton of CNFs in portion indicated by the square.N.Zhang et al./Composites:Part B54(2013)209–214211r ¼ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ3r 0:r 0r ¼ rcri4.Results and discussionsImages of the CF woven fabric and CNF Fig.4a and b,respectively.After uniformly stream impacting for a given time,the CF/epoxy was severely eroded while the surface protected by paper coating did not show much erosion.The inspected by SEM (Fig.4c and d).As can be seen,sists of the removal of matrix materials in the resin that the exposed ﬁbers are no longer bonded to when the epoxy matrix fails to support the ﬁbers.ﬁbers could easily break into fragments,removal during erosion.The failure mode in process involving surface matrix removing,surface micro-cracking,ﬁber/matrix debonding,ﬁber breakage and material removal [10–12].As shown in Fig.4c,many micro-cracks caused by the im-pact of erodent particles can be seen in carbon ﬁbers,and many small fragments of ﬁbers also can be seen on the eroded surface.For the surface protected by the CNF nanopaper coating,there are few exposed segments of carbon nanoﬁbers after particle ero-sion as shown in Fig.4d.many CNFs can partake the impact force and the ﬁber network be-haves as a whole shielding during particle collision.While for CF/epoxy composites,the ﬁber spacing is comparable or even larger than the size of the eroding particles,therefore,the resin matrix is not well protected.The pure epoxy plaque shows a better parti-cle erosion resistance than its CF/epoxy composite,but the resis-tance is not as good as the CNF nanopaper coating.Our FE simulation results further interpret the experimental served differences between CF/epoxy composite with and without nanopaper during particle erosion.The eroded volume is calcu-as the amount caused by the single impingement.The eroded volume for CF/epoxy is about three times as that for CNF nanopaper.addition,the erosion results are more sensitive to the impinging location for CF/epoxy composite than for CNF pares the eroded volume at different impinging positions CF/epoxy composite and CNF nanopaper.The eroded volume plotted versus a surface distance of several times of the REV range utilizing periodicity.Five representative positions A,B,C,D,and investigated for CF/epoxy composites while two positions woven fabric,(b)SEM image of CNF nanopaper,(c)SEM images of eroded CF/epoxy composite surface,composite surface.Fig.5.Mass loss of different materials after 15sec erosion test.212N.and G are investigated for CNF nanopaper as indicated in Fig.6b.For CF/epoxy composite the eroded volume at position E is nearly40% smaller than that at position A.While for CNF nanopaper the rela-tive difference for eroded volume between the two positions is below10%.The largest erosion rate occurs when particle impinges at the resin rich position in both cases.The simulation results pro-vide qualitative explanation to the fact that the eroded surface of CNF nanopaper is much smoother than that of CF/epoxy composite.Comparison of the effect of impinging positions on the eroded volume for CF/epoxy composite and CNF nanopaper.(a)The eroded volume versus curve for CNF nanopaper and right for CF/epoxy;(b)Top view of the different impinging positions,where L is the distance betweenﬁberContour plot of von Mises stress for(a)CF/epoxy and(b)CNF nanopaper at maximum erodent indentation,(c)von Mises stress versus the distance from position along the x axis on the target surface.The horizontal dash lines in(c)indicate the critical stresses for CNF/CF and epoxy,respectively.The much smaller erosion rate of CNF nanopaper can be attrib-uted to its nano-sized structure.For CF/epoxy composite theﬁber spacing is larger or comparable to the eroding particle size and the relative weak resin cannot be effectively protected.While for the nanopaper theﬁber spacing is much smaller,a large number of in-ter-connectedﬁbers can partake the impact force of the particle to-gether at the impinging position.This effect can be demonstrated by comparing the stress distribution for the two target materials. Fig.7a and b plot the contour of von Mises stress at maximum ero-dent indentation for CF/epoxy composite and CNF nanopaper, respectively.For both targets the erodent impinges at the positions corresponding to the largest erosion,i.e.position A for CF/epoxy composite and F for CNF nanopaper.It shows that for CNF nanopa-per the stress endured by the CNFs is much higher than that by the epoxy resin while for CF/epoxy composite the stresses inﬁber and resin do not differ much.In both cases,the resin is the main source for eroded volume due to its much lower strength than theﬁbers. The stress distribution can be more clearly seen in Fig.7c where the von Mises stress on the target surface is plotted against the dis-tance from the initial impinging position along the x axis.For Fig.7c the erosion criteria is switched off in the simulations for comparison convenience.The peaks and valleys on the curve of CNF nanopaper correspond to the high stresses on CNFs and low stresses on epoxy.It can be seen from Fig.7c that although the nanoﬁbers in CNF nanopaper experience very high stress near the impinge location,the epoxy resin actually experiences a lower stress than that in CF/epoxy composite because the stress is mainly endured by the CNFs for CNF nanopaper as indicated by the dark strips in Fig.7b.The intensely distributedﬁbers play an important role in partaking the impacting force,leading to smaller stress in the weak resin.While for CF/epoxy composite theﬁber may be far away from the impinge location due to the largeﬁber inter-space.The impact force is mainly endured by the weak resin. Fig.7c represents the instantaneous stress distribution for a case study.The nanopaper may not lose any weight at this time point because the endured stresses by both CNF and epoxy are lower than the critical CNF/CF and epoxy stresses marked on Fig.7c.On the other hand,some epoxy near the impinging point of the CF/ epoxy composite may be ablated away because the endured stress there reaches the critical value.Although qualitative,this simpli-ﬁed analysis provides an explanation for the observed differences of particle resistance between the two composite materials.5.ConclusionsIn this study,carbon nanoﬁber(CNF)nanopaper was prepared by theﬁltration method and used to protect the carbonﬁber (CF)/epoxy composites through vacuum assisted resin transform molding(VARTM)process.The CNF nanopaper can achieve much better particle erosion resistance than the conventional CF/epoxy composites.Ourﬁnite element simulations of the particle erosion experiments,although highly simpliﬁed,are able to provide qual-itative insight regarding the underlying mechanisms.The CNF nanopaper is indicated as a good protective coating material for wind turbine blades and other related applications in aerospace and transportation industries.AcknowledgementsTheﬁrst author would like to acknowledge the China Scholar-ship Council for theirﬁnancial support to enable the author to study at The Ohio State University.The authors would like to thank NSF and Nanomaterial Innovation Ltd.for partialﬁnancial support of this work.Carbonﬁber mats were donated by Textile Industries, Inc.and the epoxy resin was donated by Hexion.References[1]Miyazaki N,Takeda N.Solid particle erosion ofﬁber reinforced plastics.JCompos Mater1993;27(1):21–31.[2]Tsiang TH.Sand erosion ofﬁber composites:testing and evaluation.In:ChamisCC,editor.Test Methods and Design Allowables for Fibrous Composites,vol.2.ASTM STP1989:1003;55–74.[3]Tilly GP.Sand erosion of metals and plastics:a brief review.Wear1969;14:241–8.[4]Tilly GP.Erosion caused by airborne particles.Wear1969;14:63–79.[5]Tilly GP,Sage W.The interaction of particles and material behaviour in erosionprocess.Wear1970;16:447–65.[6]Miyazaki N,Hamao T.Effect of interfacial strength on erosion behavior of FRPs.J Compos Mater1996;30(1):35–50.[7]<>.Last accessed on September262012.[8]Dalili N,Edrisy A,Carriveau R.A review of surface engineering issues critical towind turbine performance.Renew Sust Energy Rev2009;13(2):428–38. [9]Barkoula NM,Karger-Kocsis J.Review processes and inﬂuencing parameters ofthe solid particle erosion of polymers and their composites.J Mater Sci 2002;37(18):3807–20.[10]Tilly GP.A two stage mechanism of ductile erosion.Wear1973;23(1):87–96.[11]Pool KV,Dharan CKH,Finnie I.Erosive wear of composite materials.Wear1986;107(1):1–12.[12]Patnaika A,Satapathyb A,Chandc N,Barkoulad NM,Biswasb S.Solid particleerosion wear characteristics ofﬁber and particulateﬁlled polymer composites:a review.Wear2010;268(1–2):249–63.[13]Zhou G,Movva S,Lee LJ.Preparation and properties of nanoparticle and long-ﬁber-reinforced unsaturated polyester composites.Polym Compos 2009;30(7):861–5.[14]Palmeri MJ,Putz KW,Ramanathan T,Brinson LC.Multi-scale reinforcement ofCFRPs using carbon nanoﬁpos Sci Technol2011;71(2):79–86. [15]Cai ZQ,Movva S,Chiou NR,Guerra D,Hioe Y,Castro JM,et al.Effect ofpolyaniline surface modiﬁcation of carbon nanoﬁbers on cure kinetics of epoxy resin.J Appl Polym Sci2010;118(4):2328–35.[16]ElTobgy MS,Ng E,Elbestawi MA.Finite element modeling of erosive wear.Int JMach Tool Manu2005;45(11):1337–46.[17]Grifﬁn D,Daadbin A,Datta S.The development of a three-dimensionalﬁniteelement model for solid particle erosion on an alumina scale/MA956substrate.Wear2004;256(9–10):900–6.[18]Takaffoli M,Papini M.Finite element analysis of single impacts of angularparticles on ductile targets.Wear2009;267(1–4):144–51.[19]Shimizu K,Noguchi T,Seitoh H,Okadab M,Matsubara Y.FEM analysis oferosive wear.Wear2001;250(1–12):779–84.[20]Bielawski M,Beres W.FE modelling of surface stresses in erosion-resistantcoatings under single particle impact.Wear2007;262(1–2):167–75.[21]Wang YF,Yang ZG.Finite element model of erosive wear on ductile and brittlematerials.Wear2008;265(5–6):871–8.[22]Martienssen W,Warlimont H.Springer handbook of condensed matter andmaterials data.Berlin:Springer;2005.[23]Low KH,Wang Y.Modeling of multi-layer circuit boards by using a model ofbi-phase and elasto-plastic plies.Circuit World2007;33:9–20.[24]Tibbetts GG,Beetz JCP.Mechanical properties of vapour-grown carbonﬁbres.JPhys D:Appl Phys1987;20(3):292–7.[25]Grace NF,Ragheb WF,Sayed GA.Development and application of innovativetriaxially braided ductile FRP fabric for strengthening concrete pos Struct2004;64(3–4):521–30.214N.Zhang et al./Composites:Part B54(2013)209–214。

钛合金BT9和08X18H10T不锈钢多轴低周疲劳损伤的微观机理

材料研究文章编号:100321545(2006)0120001203钛合金BT9和08X18H10T 不锈钢多轴低周疲劳损伤的微观机理于海生1,丰崇友1,王兴国1,舒卡耶夫谢.尼.2(1.佳木斯大学材料科学与工程学院,黑龙江佳木斯　154007;2.乌克兰国立技术大学2基辅工业大学机械工程学院,基辅　03056)摘要:研究了钛合金BT 9和08X 18H10T 不锈钢在比例和非比例载荷下的低周疲劳特性,非比例载荷下钛合金BT 9附加强化程度很小,08X 18H10T 不锈钢则产生了明显的附加强化,而二者的疲劳寿命均降低明显。

采用透射电镜(TE M )对钛合金BT 9及08X 18H10T 不锈钢的疲劳位错亚结构进行了对比分析,结果表明:非比例载荷下,钛合金BT 9中局部高密度位错,以及08X 18H10T 不锈钢面塑性变形方式从平面状滑移向波纹状滑移转化,是其低周疲劳损伤程度加剧及寿命降低的主要原因。

关键词:低周疲劳;钛合金BT 9;08X 18H10T 不锈钢;附加强化;亚结构中图分类号:TG 146.2+3;TG 113.25+5 文献标识码:A收稿日期:2005208202基金项目:黑龙江省骨干教师科研基金研究资助项目(1055G 047)作者简介:于海生,1966年生,男,教授,博士后,主要从事材料疲劳与断裂方面的研究。

在实际工作环境中,大多数工程零部件常常承受多轴循环载荷作用,其疲劳破坏都是在多轴疲劳应力2应变状态下发生的。

在多轴循环加载条件下,由于存在多向应力或应变,循环特性与单轴情况相比会发生很大变化。

特别是在多轴非比例加载条件下,无论在宏观力学分析、试验研究、还是损伤机理方面都更加复杂,因此,为了全面认识疲劳损伤机理,应该深入研究多轴疲劳。

近20年来,国内外学者对800H 镍合金、316不锈钢、Z r 24合金等材料的比例和非比例载荷疲劳特性进行了研究[1～3],但对其疲劳损伤微观机理缺乏系统认识,这方面有待进一步研究,以便准确地估算材料在多轴载荷下的疲劳寿命并描述损伤微观机理。

蠕变疲劳载荷下9-12%Cr汽轮机转子钢亚晶粒演变规律研究

蠕变疲劳载荷下9-12%Cr汽轮机转子钢亚晶粒演变规律研究在全球提倡节能减排的大环境下,越来越多的新能源并网发电,这就造成了电力输出的波动性。

因此,传统的火力发电在未来的能源结构中不仅是最主要的电力输出,同时还肩负着调峰的职责。

调峰过程中机组频繁启停,其设备在产生蠕变损伤的同时会叠加疲劳损伤,两者的叠加交互大大缩短了机组使用寿命。

发电企业为实现效益的最大化,会在定价策略中主动找到调峰所带来高额利润和机组寿命损耗的平衡点。

9-12%Cr马氏体耐热钢以其优越的抗疲劳、蠕变抗氧化性能成为了新一代超超临界汽轮机组的首选钢。

本文以9-12%Cr钢的典型代表X12CrMoWVNbN10-1-1为研究对象,对其进行大气环境下的高温低周疲劳实验,探究温度、载荷对其使用寿命、力学性能的影响。

并在特定工况下进行不同寿命分数的高温疲劳中断实验,研究该耐热钢不同寿命阶段的损伤、微观组织结构演变等。

同时,建立亚晶结构与塑性应变之间的关系,为后续优化、完善寿命预测模型提供一定的理论支持。

试验结果表明:9-12%Cr马氏体耐热钢在高温低周疲劳载荷下表现出典型的循环软化特征,温度的升高和载荷的增大会显著缩短其使用寿命;随着循环载荷的进行,第二相颗粒发生变化并削弱了其对亚晶结构的钉扎作用、马氏体板条结构逐渐粗化、亚晶粒尺寸变大、位错密度逐渐减小;建立了亚晶粒大小与塑性应变之间的数学模型,两者呈近似指数关系。

ASTM A234-10中温与高温下使用的锻制碳素钢及合金钢管配件

3 For referenced ASTM standards, visit the ASTM website, , or contact ASTM Customer Service at service@. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.
5 Available from Manufacturers Standardization Society of the Valve and Fittings Industry (MSS), 127 Park St., NE, Vienna, VA 22180-4602, .
Suitable for Fusion Welding, for High-Temperature Service A217/A217M Speciﬁcation for Steel Castings, Martensitic Stainless and Alloy, for Pressure-Containing Parts, Suitable for High-Temperature Service A960/A960M Speciﬁcation for Common Requirements for Wrought Steel Piping Fittings 2.3 ASME Standards:4 B16.9 Steel Butt-Welding Fittings B16.11 Forged Steel Fittings, Socket Welding and Threaded 2.4 ASME Boiler and Pressure Vessel Code:4 Section V Nondestructive Examination Section VIII, Division 1, Pressure Vessels Section IX Welding Qualiﬁcations 2.5 MSS Standards:5 MSS-SP-25 Standard Marking System for Valves, Fittings, Flanges, and Unions MSS-SP-79 Socket Welding Reducer Inserts MSS-SP-83 Steel Pipe Unions, Socket-Welding and Threaded MSS-SP-95 Swage(d) Nipples and Bull Plugs MSS-SP-97 Integrally Reinforced Forged Branch Outlet Fittings—Socket Welding, Threaded and Buttwelding Ends 2.6 ASNT Standard:6 SNT-TC-1A Recommended Practice for Nondestructive Testing Personnel Qualiﬁcation and Certiﬁcation

基于数字散斑相关技术与有限元仿真相结合方法研究0Cr18Ni9不锈钢的断裂行为

基于数字散斑相关技术与有限元仿真相结合方法研究0Cr18Ni9不锈钢的断裂行为王亚军;王儒文;贺启林;周浩洋;王宇宁【摘要】依据GB/T 21143—2014,对0Cr18Ni9不锈钢板紧凑拉伸试样进行了断裂试验,结合扫描电镜(SEM)观察其钝化线,采用数字散斑相关技术和有限元仿真相结合的方法得到了裂纹区域的应变和应力场.结果表明:0Cr18Ni9不锈钢钝化线斜率约为 GB/T 21143—2014推荐经验钝化线斜率的2倍;该材料呈现出高韧性断裂特征,试样在发生较大范围屈服时,裂纹才明显张开,试样启裂时,韧带区域已全面屈服;断裂力学有限元仿真验证了数字散斑相关技术的适用性,数字散斑相关技术能够比较准确地表征裂尖"奇异区"外的结构应变场.%According to GB/T 21143 —2014,the fracture test was carried out on the compact tensile specimens of 0Cr18Ni9 stainless steel,the blunting line was observed by scanning electron microscope (SEM),and the strain and stress fields in the crack area were obtained by the combination method of digital speckle test technique and finite element simulation.The results show that the slope of the blunting line of 0Cr18Ni9 stainless steel was about double of that of the recommended experience blunting line of GB/T 21143—2014;the material exhibited high toughness fracture characteristics,and the crack was opened when the specimen was yielding in a large range,and the ligament area had already yielded completely when the specimen cracked;the applicability of the digital speckle correlation technique was verified by the finite element simulation of fracture mechanics,and thedigital speckle correlation technology could accurately characterize the structural strain field outside the crack tip'singular region'.【期刊名称】《理化检验-物理分册》【年(卷),期】2018(054)005【总页数】8页(P309-316)【关键词】0Cr18Ni9不锈钢;断裂试验;钝化线;数字散斑相关技术;有限元仿真【作者】王亚军;王儒文;贺启林;周浩洋;王宇宁【作者单位】北京宇航系统工程研究所深低温技术研究北京市重点实验室,北京100076;北京宇航系统工程研究所深低温技术研究北京市重点实验室,北京100076;北京宇航系统工程研究所深低温技术研究北京市重点实验室,北京100076;北京宇航系统工程研究所深低温技术研究北京市重点实验室,北京100076;航天材料及工艺研究所,北京100076【正文语种】中文【中图分类】O346.10Cr18Ni9不锈钢具有良好的耐蚀和低温性能，广泛应用在运载火箭管路结构部件中。

镁合金疲劳1

高频载荷作用下镁合金AZ91的疲劳性能研究窦秋芳，王清远*（四川大学土木工程及力学系，成都，610065）摘要：镁合金由于具有质量轻，比强度和比刚度高以及良好的铸造性能等特点，在理论研究和实际应用中引起了人们的极大关注.超声疲劳试验技术应用于疲劳断裂研究领域具有省时、省力、省钱等优点，适用于材料的长寿命疲劳和低速率裂纹的扩展研究。

该试验技术不仅适用于材料疲劳学和断裂力学的基础研究，而且其成果已应用到航空、航天等工业领域和医学领域。

本文利用20kHz超声疲劳实验方法，对镁合金AZ91疲劳性能进行了研究,获得了镁合金AZ91的S-N曲线。

利用扫描电镜（SEM）对镁合金AZ91在室温下疲劳断口的形貌进行观察，研究了疲劳裂纹的起始与扩展特征。

关键词：超声疲劳；长寿命疲劳；疲劳断口；S-N曲线Study on Gigacycle Fatigue Behavious of Magesium Alloy AZ91DOU Qiu-fang1 W ANG Qing-yuan1(Department of Civil Engineering and Mechanics, Sichuan University, Chengdu 610065, China)Abstract: Magnesium alloys are very attractive as structural materials because of their low density and their rather high strength-to-weight ratio and high rigidity-to-weight ratio. Ultrasonic fatigue test is time saving and effective method to investigate the long life fatigue and very slow crack growth behaviors of metals. Besides scientific investigations in laboratory, ultrasonic fatigue is also used for industrial and medicine applications. The long life fatigue of AZ91 Magnesium alloy is tested with 20 kHz ultrasonic fatigue method. The fatigue fracture surface is observed by means of SEM. The characteristic of fatigue crack initiation and propagation has been studied.Keywords: Ultrasonic fatigue，Long life fatigue，Fracture surface，S-N curve1引言由于重量轻，比强度和比刚度高，耐腐蚀，铸造及机械加工性能好，镁合金被视为重要的工程材料之一，广泛应用于汽车、电子通讯、军工、航空、航天等领域。

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Characterizationofhighcyclefatiguebehaviorofanewgenerationaluminumlithiumalloy

P.S.Dea,R.S.Mishraa,⇑,J.A.BaumannbaCenterforFrictionStirProcessing,DepartmentofMaterialsScienceandEngineering,MissouriUniversityofScienceandTechnology,

Rolla,MO65409,USAbTheBoeingCompany,St.Louis,MO631666,USA

Received10February2011;receivedinrevisedform1June2011;accepted2June2011Availableonline5July2011

AbstractThehighcyclefatiguelifecharacteristicsofanAl–Lialloywerestudiedasafunctionofmicrostructure.Whilefortheparentmicro-structurefatiguelifedecreasedasgrainsizeincreased,nosucheﬀectwasnotedathighstresses.Thisdecreaseinfatiguelifewascorrelatedwithlowercrackinitiationlifeduetosmallcrackeﬀect.Undermultiaxialstressconditions,thealloyexhibitedintergranularcracking.Thecross-linkingofintergranularcracks(intheT8condition)causedafurtherdeteriorationinfatiguelife.Additionally,planarslipmovements(intheT3condition)instageIcrackpropagationwereobserved.Slipplanaritydependedonboththesampletextureandthenatureoftheprecipitates.Fractographicandtexturalevidenceispresented.Ó2011ActaMaterialiaInc.PublishedbyElsevierLtd.Allrightsreserved.

Keywords:Aluminumalloys;Fatigue;Fracture

1.IntroductionTheuniquecombinationoflowdensityandhighstrengthofaluminum–lithiumalloyssuggeststhatsuchmetallicmaterialhasattractiveapplicationsintheaero-spaceindustry.However,themicrostructuralcomplexityofthesealloysandcorrespondingdeleteriouseﬀectsonmechanicalpropertieshavepreventeditswidespreaduse.Consequentresearchtoimprovemechanicalpropertieshasresultedinnewercompositionalmodiﬁcationsforthisgroupofalloys,yetnodetailedfatiguebehaviorevaluationforsuchnewalloysexistsincurrentliterature.Thepresentworkthereforecharacterizesthehighcyclefatigueandduc-tilitybehaviorofaleadingedgecommerciallyavailablealuminum–lithiumalloy.ThenextsubsectionprovidesabriefbackgroundoftheprecipitatetypeanditsinﬂuenceondeformationindiﬀerentAl–Lialloys.

1.1.PrecipitatesinAl–LialloysPrecipitationhardening(PH)constitutestheprincipalstrengtheningmechanisminAl–Lialloys;therefore,thenatureandtypeofprecipitatesareofprimeinterest.Con-sideringtheAl–Liphasediagramﬁrst,binaryAl–Lialloysconsistofgrainboundaryd(AlLi)phasewithcoherentorderedd0(Al3Li)phasedistributedwithinthematrix.

DependingontheLicontent,ternaryAl–Cu–Lialloysareclassiﬁedintotwotypes.IntheﬁrsttypeofalloywithlowLicontent(e.g.1.15%Liand5.15%Cu),partiallycoherenth0plates(thetransitionphaseofAl2Cu),T1

(Al2CuLi)andTB(Al7.5Cu4Li)aretheprincipalstrength-

eningphases[1].ForalloyswithhighLi(e.g.2.7%Cuand2.25%Li),h0,T1andcoherentorderedd0phasesform.InaternaryAl–Li–Mgsystem(e.g.5.5%Mgand2%Li),incoherentAl2LiMgandcoherentd0aretheprincipal

phases[1].ForAl–Li–Cu–Mgalloys,precipitationissimi-lartoternaryAl–Cu–LiandisafunctionofitsCu:Liratio.Thus,forlowCu:Li(<1.5)S0(Al2CuMg),T1andordered

d0aretheprincipalprecipitatingphases[2–4].Athigher

1359-6454/$36.00Ó2011ActaMaterialiaInc.PublishedbyElsevierLtd.Allrightsreserved.doi:10.1016/j.actamat.2011.06.003

⇑Correspondingauthor.

E-mailaddress:rsmishra@mst.edu(R.S.Mishra).

www.elsevier.com/locate/actamatAvailable online at www.sciencedirect.comActaMaterialia59(2011)5946–5960Cu:Liratios(>2–3),precipitationisrestrictedtotheS0andT1phasesonly[2–4].1.2.EﬀectofprecipitatesonslipanddeformationcharacteristicsTheabovediscussionindicatesthattheAl–Licomposi-tionleadstoawidevarietyofprecipitatingphases.Thispre-cipitate-typevariationsigniﬁcantlyaltersthedislocationslipmechanisms.Dependingonslipbandappearanceordislocationstructurepresent(intransmissionelectronmicroscopy(TEM)experiments),slipinface-centeredcubic(fcc)alloysisclassiﬁedintotwotypes:(i)wavyand(ii)planar.Forawavyslipmetal,slipbandsexhibitahomoge-neousstructure.Foraplanarslipsituation,aheterogeneousstructureisseen[5].TEMobservationofmonotonicallystretchedwavyslipmetalischaracterizedbydislocationbundles.Amultipolardislocationstructurewithextendeddislocationpile-upshasbeennotedforplanarslipmetals[6].Althoughexactlywhysuchdiﬀerencesexistisnotunderstoodfully,short-rangeorderingandclusteringarebelievedtobedeterminingfactors[6].Variablessuchasstackingfaultenergyandyieldstress(controllingscrewdis-locationannihilationdistance)weredeemedtobeofsec-ondaryimportance[6].Thus,binaryAl–Lialloywithcoherentorderedprecipi-tates(d0)exhibitsaplanarsliptendency[7].Thegrainboundarysecondphaseandprecipitate-freezonescontrib-utetoadditionalstrainlocalization[7].Suchslipheteroge-neitieshavebeenassociatedwithlowfatiguecrackinitiationresistance[7].Similarly,d0andgrainboundarysecondphases(h0,T1,T2,b0)reducethefracturetoughnessvaluesinanAl–Li–Cu–Zralloy[8].Identically,d0precipi-tatesinAl–Li–Cu–Mg–ZralloyofthelowCu:Lityperesultedinstrainlocalizationduringlowcyclefatigue[9].Thus,planarslipinAl–Lialloysisassociatedwithcoherentorderedd0phaseandresultsinoverallpropertydegrada-tion.Asanexception,Khireddineetal.[10]howeverpro-posedthatslipplanarity-inducedcrackbifurcationcanresultinimprovedfracturetoughnessvalues.Conversely,T/SphasespresentinAl–Lialloyspromotesliphomogeni-zationwhichleadstowavyslipcharacteristics,resultinginimprovedmechanicalproperties[9].Animportantobserva-tionofthisstudyisthattextureiscriticalinenhancingthisslipplanarity.Theeﬀectisdiscussedinmoredetaillaterinthispaper.1.3.EﬀectoftextureondeformationduringfatigueTheﬁrstdetailedexaminationoftexture(predominantly{110}h112iand{100}h011itype)andgrainsizeeﬀectonthecyclicstressstrain(CSS)lifeofAl–Li–Cu–MgalloyswasdonebyKhireddineetal.[10].Intheabove-mentionedwork,samplesextractedfromthesurfaceofanextrudedbarshowedalowerCSSlifecomparedtothosemachinedfromthecore.ThisCSSlifechangewithsamplelocationwasattributedtoanincreased{111}poledensityinthesurfacesamplescomparedtothosefromwithinthecore[10].AnadditionaldecreaseinCSSlifewithsampleorien-tationchange(fromthelongitudinaltoatransversedirec-tionofrolling)wasalsoreported.Thevariationwasattributedtoagrainsizeeﬀect[10].AsimilardeformationtextureeﬀectonAA2090alloycausedareducedhighcyclefatiguelifeatanorientation45󰀂totherollingdirection[9].