ANSYS工程分析.ppt

1、Chapter 16,非線性分析的收斂性探討 Convergence of Nonlinear Analysis,2/50,Contents,16.1何謂非線性分析？ What Are Nonlinear Analyses? 16.2解題方法 Solution Methods 16.3收斂性控制的一些重要觀念 Important Concepts for Convergence Controls 16.4收斂性控制的基本參數 Basic Solution Options 16.5收斂性控制的進階參數 Advanced Solution Options 16.6練習題：橡膠密封墊分析 Exerc

2、ise: Hyperelastic Planar Seal,3/50,第16.1節,何謂非線性分析？ What Are Nonlinear Analyses?,4/50,16.1.1 What is a Nonlinear Structure,5/50,16.1.2 Causes of Nonlinearities,Geometric Nonlinearity Material Nonlinearity Status Nonlinearity,6/50,Geometric Nonlinearity,7/50,Material Nonlinearity,8/50,Status Nonlinear

3、ity,9/50,16.1.3 Consequences of Nonlinearities,Principle of superposition no longer applicable Solution may depend on loading history,10/50,第16.2節,解題方法 Solution Methods,11/50,16.2.1 Equations for a Nonlinear Structure,12/50,16.2.2 Incremental Method,13/50,16.2.3 Newton-Raphson Method,14/50,16.2.4 Co

4、nvergence Criteria in ANSYS,15/50,第16.3節,收斂性控制的一些重要觀念 Important Concepts for Convergence Controls,16/50,16.3.1 Radius of Convergence,17/50,16.3.2 Consistent Stiffness Matrix,Tangent stiffness Additional stiffness due to deformation (geometric change) Additional stiffness due to stress stiffening Add

5、itional stiffness due to change of loading direction.,18/50,16.3.3 Load Steps, Substeps, and Equilibrium Iterations,19/50,16.3.4 Concepts of Time,The ends of load steps or substeps can be identified by time. For dynamic problem, time is used as a real-world clock. For static problem, time is used as

6、 a counter.,20/50,16.3.5 Automatic Time Stepping,For nonlinear problem, the user-input Dt is used as initial incremental time. ANSYS adjusts Dt automatically according to the convergence behavior of the solution.,21/50,16.3.6 Text Output Information,1,2,3,4,5,22/50,16.3.7 Graphical Output Informatio

7、n,23/50,16.3.8 Automatic Nonlinear Solution Control,SOLCONTROL command can be used to activate automatic nonlinear solution control algorithm. The default is ON.,24/50,第16.4節,收斂性控制的基本參數 Basic Solution Options,25/50,Basic Solution Options,26/50,16.4.1 Analysis Type (ANTYPE),For nonlinear analysis, on

8、ly two analysis types applicable: STATIC and TRANS.,27/50,16.4.2 Nonlinear Geometry (NLGEOM),NLGEOM turns ON/OFF the effects of geometric nonlinearity.,28/50,16.4.3 Load Step Time (TIME),TIME specifies the time at the end of the following load step.,29/50,16.4.4 Number of Substeps (NSUBST, DELTIM),N

9、SUBST specifies number of substeps for the following load step. DELTIM specifies time for each substep for the following load step. The two commands are equivalent, i.e.,30/50,16.4.5 Automatic Time Stepping (AUTOTS),AUTOTS turns ON/OFF the functions of auto time stepping.,31/50,16.4.6 Ramped/Stepped

10、 Loading (KBC),32/50,16.4.7 Output Controls (OUTRES),OUTRES controls the amount of data stored in Jobname.RST.,33/50,16.4.8 Monitor File (MONTOR),34/50,第16.5節,收斂性控制的進階參數 Advanced Solution Options,35/50,Advanced Solution Options,36/50,16.5.1 Equation Solver (EQSLV),EQSLV lets you choose the algorithm

11、 solving the equations.,37/50,16.5.2 Time Step Prediction Based on Contact Status (SOLCONTROL),The second key of SOLCONTROL command is to ask ANSYS to adjust time steps according to contact status.,38/50,16.5.3 Number of Equilibrium Iterations (NEQIT),NEQIT specifies the number of iterations beyond

12、which ANSYS would start another “attempt”.,39/50,16.5.4 Convergence Criteria (CNVTOL),CNVTOL overrides the default convergence criteria.,40/50,16.5.5 Newton-Raphson Option (NROPT),(a) Full Method,(b) Modified Method,(c) Initial Method,41/50,16.5.6 Line Search (LNSRCH),LNSRCH turns ON/OFF the “line s

13、earch” algorithm in ANSYS.,42/50,16.5.7 Predictor (PRED),43/50,16.5.8 Adaptive Descent (NROPT),44/50,16.5.9 Stress Stiffening (SSTIF, PSTRES),SSTIF/PSTRES turns ON/OFF the computation of stress stiffness (Ks) and storing on file.,45/50,16.5.10 Cutback Control (CUTCONTROL),CUTCONTROL specifies the co

14、nditions in which ANSYS would decrease time step during auto time stepping.,46/50,16.5.11 Time Integration Effects (TIMINT, TINTP),TIMINT turns ON/OFF transient effects. The parameter GAMMA of TINTP command can be used to introduce a “numerical damping”.,47/50,16.5.12 Stop Control (NCNV),NCNV specifies