講義課件教程subs-l09submodeling

1、Lesson content:Fundamental Assumptions Submodeling TechniquesNode-based Implementation Surface-based ImplementationLesson 9: Submodeling in Abaqus30 minutesFundamental Assumptions (1/2)Saint-Venants Principle applies:The boundary of the submodel is sufficiently far from the region within the submode

2、l where the response changes.Thus:The global model solution defines the response on the submodel boundary.Detailed modeling of the local region has negligible effect on the global solution.Solution in local area of interest is not changed by end (far field) effects as long as end loads remain static

3、ally equivalent.Fundamental Assumptions (2/2)Warning: The user must ensure that the submodeling approach will provide physically meaningful results.There are no default protections when submodelingit is a matter of the users judgment that the submodeling is done correctly.Examine contour plots of im

4、portant variables near the boundaries of the submodeled region. If the contour plots are created with the same contour range, the results will be valid if contour values coincide at the boundary of the submodeled region.Submodeling Techniques (1/5)Abaqus offers two techniques for submodelingNode-bas

5、ed submodelingNodal results field is interpolated onto submodel nodesSurface-based submodelingStress field is interpolated onto submodel surface integration points Of these two techniques, node-based is more general and more common. Either technique, or a combination of both can be used in an analys

6、isSubmodeling Techniques (2/5)Choosing a techniqueAre you performing a solid-to-solid submodeling analysis? Is it a static analysis?Surface-based submodeling is only available for solid-to-solid and static analyses For all other procedures, use node-based submodelingSubmodeling Techniques (3/5)Choos

7、ing a technique in a static analysisIs there a significant difference in the average stiffness in the region of the submodel? If so, and the global model is subject to force-controlled loading, the surface-based technique will generally yield more accurate stress results. When the stiffness is compa

8、rable, node-based submodeling will provide similar results to surface-based, but with less chance of numerical issues (caused by rigid-body modes).Differences in the stiffness of the two models may arise from additional detail in the submodel (such as a fillet or a hole), or from minor geometric cha

9、nges which do not warrant re-running the global analysisSubmodeling Techniques (4/5)Choosing a technique in a static analysis (contd)Is the model subject to large displacements or rotations?Node-based submodeling will result in more accurate transmission of large displacements and rotations in the s

10、ubmodelWhat output results are of most interest?Node-based submodeling will provide a more accurate transmission of the displacement field in the submodelSurface-based submodeling will provide a more accurate transmission of the stress field, resulting in more accurate determination of reaction forc

11、es in the submodelThe two techniques can be combined in the same modelOne boundary driven by displacements Another boundary driven by a surface tractionSubmodeling Techniques (5/5)Choosing a techniqueLoad-controlledStiffness changesYesNoNode-basedSubmodelingSurface-basedSubmodelingYesNoThe global mo

12、del is primarily loaded by displacement boundary conditionsThe global model is primarily loaded by applied forces and pressuresThe submodel has significant differences in material properties or geometry (additional holes, fillets etc.)The submodel is simply a more refined model of an assembly detail

13、Node-based Implementation (1/4)The following types of node-based submodeling are provided:Solid-to-solidShell-to-shellMembrane-to-membraneShell-to-solidAcoustic-to-structureNode-based Implementation (2/4)The transfer of solution variables from the global model to the submodel is based on the positio

14、n of the submodel boundary nodes.Submodel boundary nodes need not align with mesh lines in the global model. Abaqus will use spatial interpolation of the global solution to calculate the values for the submodel boundary nodes.Global model of a circular hole in a square plateSubmodel boundariesNodes

15、where global model solution must be stored for interpolationSymmetryyxNode-based Implementation (3/4)Magnified submodel with a crack in the plateBoundary nodes of the submodel driven by global model solutionyxNode-based Implementation (4/4)Element types that are different from those used in the glob

16、al model can be used in the submodel.Second-order elements can be used in the local model and first-order elements can be used in the global model, or vice versa.Solid elements can be used in the local model and shell elements can used in the global model, but not vice versa.Materials in the submode

17、l can be different from those in the global model.Metal plasticity can be used in the local model, and linear elasticity can be used in the global model.Procedures in the submodel can be different from those in the global model.The static response of the local model is based on the dynamic response

18、of the global model.The submodeling implementation modates both linear and nonlinear analyses.Both the submodel and the global model can follow sequences of analysis procedures (multistep analysis), and the sequences can be different for the local and global models.Submodeling can be repeated for an

19、y number of levels.Surface-based Implementation (1/2)The surface-based technique is limited to solid-to-solid submodeling for general static procedures in Abaqus/Standard. This method applies a surface traction on the surface of the submodel based on a stress field interpolated from the global model

20、.The stress field is interpolated to the surface facet integration points of the elements forming the driven surface.Submodel showing driven surfacesBoundary surface of the submodel driven by global model solutionSurface-based Implementation (2/2)Element types that are different from those used in the global model can be used in the submodel.Second-order elements