Applicability

Because it is often computationally intensive, use of the nonlinear flexible body should be applied wisely. The best types of problems for it are those in which the nonlinear behavior of some part(s) and the motions and loads of the rest of the multibody dynamics (MBD) model influence each other and, therefore, accurate results are impossible or impractical through separate MBD and FEA analyses.

One should also consider the type of structure being modeled and the type of nonlinearity deemed important. For problems where only geometric nonlinearity (that is, large deformation) is of interest and the structure in question can be considered beam-like, one might consider using a discrete flexible link approach (series of rigid parts connected by massless beam forces) or the Adams FE Part (Adams native geometrically nonlinear body). Another common approach here is the so-called "multi-MNF" method whereby users connect a series of linear flexible bodies together with fixed joints. This method, however, is typically labor intensive from a pre-processing standpoint and can sometimes suffer artificial peaks in the modal stress recovery at the "seams" (points where MNF's are joined together). So, here, the nonlinear flexible body may be an attractive alternative.

Large-deformation problems where the geometry of the flexible body is not beam-like and cases where material nonlinearity is important would be good candidates for the Adams nonlinear flexible body.

While large deformation is supported, it should be noted that post-buckling types of problems are likely not well suited to the Adams nonlinear flexible body or even MSC Nastran implicit nonlinear FEA standalone.

More details regarding limitations of the Adams nonlinear flexible body can be found in "Appendix B: Limitations of Adams MaxFlex."

For full-vehicle analysis in Adams Car, one should be advised that when driving over any kind of obstacle or rough road use of the Adams Tire PAC2002 3D enveloping tire model or an F-Tire model is recommended. This is true generally speaking, but especially so when the vehicle includes nonlinear flexible bodies. The higher fidelity tire models will provide more accurate road loads for the high fidelity nonlinear flexible body and not introduce unrealistically sharp load changes which can cause model convergence issues in addition to result inaccuracy. And, it comes at little, if any, cost to the overall simulation time since that will be dominated by the nonlinear flexible body, not the tire model.