外文翻译-利用有限元法预测夹具系统的工件形.doc

1、毕 业 设 计（论 文）外 文 参 考 资 料 及 译 文译文题目： Prediction of workpiece deformation in a fixture systemusing the finite element method 利用有限元法预测夹具系统的工件变形 学生姓名： 学 号： 专 业： 所在学院： 指导教师： 职 称： 20xx年 2月 27日 Prediction of workpiece deformation in a fixture system using the finite element method1. Introduction Methods for

2、 analyzing fixtures are essential to the practice and economics of machining. In particular, the ability to model and accurately predict workpiece deformation induced by fixturing loads and/or predict the unknown fixtureworkpiece contact forces are crucial for designing functional fixtures. The most

3、 common modeling and analysis approaches used for fixtureworkpiece systems include the rigid body approach, thecontact mechanics based approach and the finite element modeling approach. Of these approaches, the rigid body modeling approach 13 is by definition incapable of predicting workpiece deform

4、ations and is therefore unsuitable for analysis of the impact of fixturing on part quality. The contact mechanics approach, although attractive from astandpoint of computational effort, is limited to parts that can be approximated as elastic half-spaces. Models derived fromthis approach are capable

5、of accurately predicting unknown locator reaction forces and localized contact deformations 46. However, they are not applicable for thin, compliant parts. Finite element models on the other hand are very powerful and are capable of accounting for all compliances and nonlinearities present in the sy

6、stem. Although use of finite element models has been widely reported in the literature and employed in practice, a clear understanding of the role of the different fixture compliances on the prediction accuracy of workpiece deformation is lacking. Also knowledge of the effects of different finite el

7、ement model parameters on workpiece deformation is lacking. A common assumption in application of Finite Element Analysis (FEA) to analyze a fixtureworkpiece system is that the fixture is completely rigid since it is much stiffer than the workpiece in many applications. In most such cases, the workp

8、iece is modeled and nodes at the location of fixture contact are completely restrained. This formulation is commonly referred to as a single-point contact 712. Omitting fixture elements does not allow for the model to account for compliance in the fixture and neglects frictional contact effects betw

9、een the fixture and workpiece. Other researchers 1316 have utilized linear springs to approximate the stiffness of the fixture components. However, such an approach requires the stiffness to be measured or approximated, adding time and introducing potential error into the analysis.Recent work 1719 h

10、as explored the use of surface-tosurface contact elements. Such an approach allows frictional effects to be modeled. This methodology was used for the work reported in this paper. Liao et al. 17 used FEA with contact elements to model a multiple-contact fixture system. They, however, did not investi

11、gate the effects of friction and meshing parameters on the results. Satyanarayanas 18,19 work was limited to a single fixtureworkpiece contact. More importantly, these studies did not analyze the contribution of fixture body compliance to the overall deformation. This paper investigates the effects

12、of various finite element modeling parameters, such as friction and mesh density, on workpiece deformation. In addition to modeling the workpiece and fixture tips, as is common, the effect ofcompliance of other fixture components such as support blocks, base plate, etc. on workpiece deformation is a

13、lso examined. The FEA predictions of workpiece deformation and locator reactions are experimentally verified. 2. Model development Finite element models were constructed using ANSYSw Version 5.7. Solid models were assembled of the prismatic block and fixture tips. All components in the system were m

14、odeled as isotropic elastic bodies. The fixture tips, shown in Fig. 2, were modeled as cylinders with either planar (clamp and locator circular contact areas 60 and 127 mm2,respectively) or spherical (35 mm radius of curvature) end caps. The axial lengths of the planar and spherical tips were 6.4 an

15、d 10.2 mm, respectively. The 10-node tetrahedral element Solid92 was used to mesh all solid bodies. Contact between the workpiece and fixture was simulated using the quadratic surface-to-surface contact elements Targe170 and Conta174. A constant static coefficient of friction was used to establish contact properties at the interfaces. To simulate the locators being rigidly fixed in place, the surface of each locator tip opposite to thecontact was restrained in all three translational degrees of freedom. A un