Analysis Interface
Finite element model partitioning allows the detailed investigation of highly localized stress fields by isolating a region of interest from a larger assembly model. The geometric interface that separates this refined region from the main model is the submodeling cut boundary. It receives displacement or temperature data interpolated from the coarse global run to drive the local high-density mesh analysis.
Boundary Condition
Displacement fields calculated from the initial global run are mapped directly onto the nodes along this interface. The accuracy of the submodeling cut boundary interpolation depends on the proximity of the boundary to high stress gradients. It must be positioned far enough from the localized feature to ensure that Saint-Venant’s principle holds, meaning the boundary stress remains undisturbed by the local modification.
Verification Method
Engineers compare the stress and displacement results along the boundary in both the global and submodel runs to verify the interpolation. Any significant mismatch indicates that the submodeling cut boundary was placed too close to the stress concentration or that the global mesh was too coarse to capture the overall displacement field. This step guarantees that the local stress peaks are driven by valid boundary conditions.
Mesh Refinement
The local submodel can utilize a highly refined mesh, complex material models, and detailed geometric features without the prohibitive computational cost of a globally refined model. This efficiency allows designers to run multiple design iterations on a critical weld or solder joint. The submodeling cut boundary remains fixed throughout these iterations, ensuring that the local changes do not feed back and alter the global structural response.
By isolating the analysis in this manner, fine-scale fatigue evaluations can be completed in minutes rather than days, improving both the speed and the quality of the structural optimization process.
