ansys静力分析

The Finite Element Analysis of a Shaft

Guangwei Zhang 1, a

, Li You 2,b and Zhao Li 3,c

1

School of Mechanical Engineering, Xi'an Shiyou University, China 2CNOOC Information Technology Co., Ltd. Shanghai Branch, China

3

School of Mechanical Engineering, Xi'an Shiyou University, China a zhang-guangwei@https://www.360docs.net/doc/1417282611.html,, b eimeng@https://www.360docs.net/doc/1417282611.html,, c lizhao0125@https://www.360docs.net/doc/1417282611.html,

Keywords: controllable bend sub, variation cardan shaft, finite element analysis

Abstract. Finite element method is a kind of method with the aid of computer engineering analysis of discretization numerical calculation. In the rotary steering drilling during the process of practical work, there was a great drilling pressure torque, space size limit strictly and requires a high efficiency and reliability .The working conditions are complex when drillings work underground and the working environment is harsh, there may has many unpredictable situations, the drilling tool may encounter the loose soil, or may be a hard rock, and these changes force is transmitted through the variation cardan shaft, so it is very necessary to check the strength of the variation cardan shaft. This article analyze the variation cardan shaft by ANSYS and provide a reference for actual use. Introduction

The software ANSYS is the product of the American company ANSYS, it is a large-scale general-purpose finite element analysis software, a powerful, flexible design analysis and optimization software. It has powerful computational analysis capabilities with the preprocessor and postprocessor and has been widely used in civil engineering, automotive engineering, machinery, water conservancy and hydropower engineering, mining, nuclear industry, shipbuilding and other industries and fields.

Establish Finite Element Model of the Variation Cardan Shaft

Establish geometry model of the variation cardan shaft. This paper is transmitted entity model which created in the Solidworks to the ANSYS for finite element analysis, In order to facilitate the finite element analysis of variation cardan shaft; we could make the appropriate simplification on variation cardan shaft, in the premise of no influence on the analysis results. The main simplification is to remove some chamfers. The controlled bent sub oriented institutions assembly drawing shown in Figure 1，the section view is shown in Figure 2 and the import ANSYS geometric model is shown in Figure3.

Fig. 1 Assembly drawing of the controllable bend sub

Fig. 2 The section view of the controllable bend sub Fig. 3 The geometry model Fig. 4 The meshed model Setting Unit Attribute. The system of units of ANSYS analysis will affect the input model size, material properties, real constants and load. As used herein, the unit is: m, kg, N, Pa. Variation cardan shaft material for 40CrNiMo alloy, the elastic modulus is 2.07 × 1011 N/m 2, Poisson's ratio is 0.296, the density of 7.85 × 103 kg/m 3, the yield limit of 835 MPa, ultimate tensile strength of 980 Mpa. In the finite element analysis of variation cardan shaft, the material is taken as a linear isotropic elastic material.

Setting Unit Type. Choice of unit types in finite element analysis significantly affects the speed and accuracy of the analysis. The choice depends on the structure of the geometric shape ，type of load calculation accuracy requirements and the number of independent spatial coordinates that needed to describe the problem, ANSYS provides 180 different types and categories of the unit. This article defines the element type as Solid185，the unit consists of eight node definition, each node has three degrees of freedom, this element has plasticity, hyperelastic, stress intensification, creep, large deformation and large strain and other functions, used to create a three-dimensional solid structure model.

Meshing. When meshing, in this paper, use the free meshing, using the SmartSizing meshing operation. Set the classification accuracy as 6, the whole model is divided into 45,201 units and 10,115 nodes. After meshing, the generation model is shown in Fig.4.

Applied Loads

Load includes boundary conditions and internal and external environment of multiple objects. It can be divided into freedom constraints, concentrated load, surface loads, body loads and inertia loads. Boundary conditions: Fixed constraint is applied in the variation cardan shaft near the bit face. Shown in Fig. 5.

When working in the borehole, in the case without taking into account the friction of the drill string and the borehole wall, the torque delivered by the thrust bearing is approximately equal to the provided torque of the turntable, ignoring the gravity of the rotary steerable drilling tool and drill bit, variation cardan shaft by axial pressure approximately equal to the drilling pressure. Because the

pressure of drilling in the drilling process is different and changes with the soft and hard stratum, resulting in maintaining design angle along different drilling pressures, and adjust the biasing mechanism of the eccentric displacement real-timely, and it increases the difficulty of controlling. So consider transmitting drilling pressure by rotating outer sleeve, bypassing the variation cardan shaft control section, transmitting to the variation cardan shaft through the thrust bearing. All of the loads that the variation cardan shaft bearing is: internal pressure 60 Mpa, torque 10 Nm, Axial pressure 300 kN. When applied loads, the variation cardan shaft are seen as the rod, in finite element analysis, we must equivalent some force: (1) Internal pressure load is equivalent to uniform distributed force of inner surface of the variation cardan shaft. Shown in Fig.6.

Fig. 5 Applied a fixed constraint Fig. 6 Applied the internal pressure (2) Variation cardan shaft axial pressure is equivalent to nearly balls fossa the ladder surface of uniform distribution force Q 1, it is shown in Fig.7.

Q 1=A F =26310125.88310

300m

N ?××=0.34×109 Pa (1) F—drilling pressure;

A—variability cardan shaft near the ball fossa ladder area.

(3) Variation cardan shaft suffered torque is equivalent to cardan shaft nearly balls fossa stepped surface cross section circle nodes concentrated force N 1,as shown in Fig. 8.

N 1=28

105.571010.23311××?×=?m m N n d M =6.211×103 Pa (2) M—torque ；

1d —variation cardan shaft the step face cross-section of the proximal fossa circle

diameter ；

1n —The number of nodes in the cross-sectional circle.

Fig. 7 Applied an axial force Fig. 8 Applied the torque

Solve

After preprocessing, select the ANSYS solver to solve

The Results of Finite Element Analysis. ANSYS solving result of data is stored in the Jobname.RST file, post-processing will read the data from these results file, then output graphics and list of results. The deformation, stress and Von Mises equivalent stress nephogram of the variation cardan shaft through post processing are shown in Figures 9, 10, 11.

As can be seen from the calculation results, affecting by the described loads before, the maximum deformation of the variation cardan shaft is 0.103mm, Stress in the range of 16.8 - 467Mpa, The maximum stress occurs in the upper part of the variation cardan shaft. Because the yield limit of 40CrNiMo is 835Mpa, 79.1max

=σσs ，safety coefficient is greater than 1.5, meet the requirements of strength and have a certain margin of safety.

Fig. 9 The deformation nephogram Fig. 10 Variation cardan shaft strain contours

(a) (b)

Fig. 11 Variation cardan shaft stress contours

Conclusions As can be seen from the deformation and stress cloud, the maximum deformation and stress appears in the far bit end of the variation cardan shaft, that is the place connecting to the control shaft, this requires the design personnel to consider carefully from the aspects of processing technology, connection mode and material performance during design process, meeting the requirements of working condition.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (51174164).

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