04ANSYS13.0Workbench结构非线性培训一般过程课案.ppt

In this chapter, we will present an overview of the basics of nonlinear finite-element analysis: We will start by answering a basic but very important question: What is “Nonlinear” Behavior? We will then present the strategy used in the ANSYS code for solving a nonlinear solution using linear solvers and discuss the details of exactly what this means. Three general types of nonlinearities will be introduced. Issues unique to Structural Nonlinearities will be discussed. Finally general procedures will be presented for use in nonlinear analysis. The purpose is to give you an understanding of the fundamental nature of nonlinear finite element analysis. To answer this question, first consider, What is different about building a nonlinear model? Problem dependencies affect how a nonlinear model will differ from a linear one: In some cases, there will be no difference! In other cases, you must include special nonlinear features: Such as material test data (plastic stress vs strain). And special elements (such as contact elements). Later Chapters will provide case-by-case details of modeling tips for different nonlinear situations. Simulation meshes in ANSYS: The “Shape Checking” toggle is SHPP,LSTET,ON Use of Jacobian tests at integration points is the “Standard” or SHPP,LSTET,ON method, suitable for linear analyses Use of Jacobian tests at corner nodes is the “Aggressive” or SHPP,LSTET,OFF method. This is generally a more conservative approach and may be preferred for nonlinear analyses. This is because elements which undergo distortion during solution should have a good quality shape to begin with. Because Simulation uses its own criteria for shape tests, SHPP,OFF is set when exporting a mesh to ANSYS. Also, even if SHPP,ON is set, the criteria used for warning/error elements differs between Simulation and ANSYS ANSYS Details: In Simulation, the following elements are used: Solid bodies are meshed with 10-node tetrahedral or 20-node hexahedral elements SOLID187 a