Running a nonlinear finite element analysis can be a very challenging task. The large deformations and complex constitutive models can make it very difficult to obtain a converged solution. There are many causes for nonconvergence, ranging from element inversions, material instability, failure to enforce contact constraints and many more. Sometimes it is possible that FEBio gives you a converged solution, but the solution is meaningless or at least not what was expected.
Fortunately, many of these issues can be prevented or solved with little effort. This chapter discusses some strategies to prevent common problems and to troubleshoot a problematic run. It offers some sanity checks before you run your model which can save you a lot of frustration down the road. And when things do go bad, we hope that the strategies suggested here may prove helpful.
However, keep in mind, that the finite element method cannot solve all problems. It is a very powerful numerical method, but with limitations. Understanding these limitations and how they affect your modeling work is crucial in becoming a good analysist.
Table of contents
- Section 8.1 Before You Run Your Model
- Section 8.2 Debugging a Model
- Section 8.3 Common Issues
- Section 8.4 Guidelines for Contact Problems
- Section 8.5 Cautionary Note for Steady-State Biphasic and Multiphasic Analyses
- Section 8.6 Guidelines for Multiphasic Analyses
- Section 8.7 Guidelines for Fluid Analyses
- Section 8.8 Understanding the Solution
- Section 8.9 Guidelines for Using Prestrain
- Section 8.10 Limitations of FEBio
- Section 8.11 Where to Get More Help