The Local Plastic Stress And Strain Computation Of Some Motor Shaft Under Preheating Condition Based On ANSYS

Following with the expanding development of computer technology, computer plays a more and more important role in improving the social productivity;and with the CAD/CAE/CAM more and more mature and widely applied, the industrial design and production efficiency is widely increased. Especially with development the Finite Element Analysis (FEA) technology and the optimization technology based on FEA, the design parameter can be optimized and a most feasible design can be obtained. When the FEA technology is applied in the new product design and the old product modification, It can provide the technology support and theory guidance in analysis the strength and stress distribution. In this paper, the research is based on an enterprise project and the static stress, displacement is analysised of motor shaft under the thermal assembly, which can provide an reliable reference for the next design.In the first chapter, the author introduces that with the rapid development of computer technology, the following revolutionary change in engineering, science and even the whole society. Computer Aid Engineering (CAE ) represented by virtual prototyping simulation is the specific representation of the technology revolution in engineering analysis and design. CAE provides a extremely importance which makes it a inevatively aspect in the competitively modern industrial world. Also in this chapter, the author introduces the basic knowledge of the CAE analysis software ANSYS, which is used to perform the whole analysis procedure in the paper.In the second chapter, the author introduces the basic conception of Finite Element Analysis (FEA), including the brief introduction of the development history of FEA and the analysis process, which contains the six procedure: (1) discrete the continuous body;(2)select a feasible displacement function;(3)establish the element stiffness matrix and analysis the element mechanics properties;(4)derive the global stiffness matrix and establish the balance equation of the structure;(5)solve the algebra equation set and obtain the node displacement component;(6)postprocess the computation result.In the third chapter, the material nonlinearity and the nonlinear equation solution are presented. Material nonlinearity means that the material constitutive equations are nonlinear and the deformation gradient is very small, which means the effect of the deformation to the balance equations can be ignored. Thus the balance equations can be simplified to be linear and the relation of strain and displacement is also linear. In this chapter we mainly focus on the case that the material nonlinearity caused by the plastic deformation, eq. the elastic and plastic analysis. Plasticity refers to a material property which produces a permanent deformation under some given load. The stress and strain relation of plasticity is nonlinear. In the process of a plastic analysis, the three laws are followed: yield law, flow law, strengthening law. In the enterprise project, we adopt the linear strengthening elastic-plastic model(eq. biliearity material model ) to simulate the material for the motor shafL guard ring and the welded seam.In the forth chapter, the boundary condition nonlinearity, eq. the contact analysis is presented. In the contact problems, the two objects must meet the constraint condition that the boundaries do not penetrate. There are three main methods to apply the boundary conditions: Lagrange multiplierfunction % penalty function and the direct constraint based on the solver. The first two methods have some limitations and are not adopted in the paper. The direct constraint method deals the contact problems by tracing the motion process. Once the contact is founded, the motion constraint and node force as the boundary conditions, are applied on the node where the contact is occurred. So the computation precision is high and it has general adaptability. In the contact analysis, we first assume a given contact condition (initial contact condition), and form the global stiffness matrix. Then, after the displacements and contact forces are obtained, re-form the stiffness matrix and re-solve the equation. The iteration is looped until the convergence condition is met, and the finite element analysis solution is obtained. In the process of elastic-plastic contact problem, all the iterations are needed for the contact nonlinearity and material nonlinearity. Often the effect of global stiffness matrix change is used to reflect the effect the material nonlinear. In every plastic modification iteration process, contact iteration computation is performed according to the contact state.In the fifth chapter, the author perform a nonlinear analysis of a engineering case based on the CAE software ANSYS. In order to enhance the design accuracy of the motor shaft, a series of mechanical problems are to be investigated. According to those requirements, the following works are accomplished.(l)The whole FEA model of the motor shaft is created (including model simplifying).(2) Simulation computing is processed with the double nonlinear afection of elastic-plastic material properties and contact problem taken into account. The intensity and rigidity of the motor shaft is calculated. (3) Post-processing. The stress and displacement of the motor shaft are worked out.