Meaning
Two-step structural analysis techniques interpolate global displacement field solutions onto localized high-density mesh regions to resolve steep stress gradients. Applications of finite element submodeling isolate critical details such as cooling plate fillet radii, braze joints, or mounting tabs from large pack-level simulation models. Engineering teams utilize this method to calculate accurate peak stresses and fatigue life estimates without incurring excessive computational costs.
Techniques stop applying when structural stiffness changes in the localized refined region significantly alter overall global displacement fields, violating Saint-Venant’s principle. Verification guidelines require driven boundary displacement checks between global and local submodel interfaces. Computer-aided engineering procedures mandate submodeling for all high-cycle fatigue evaluation locations.
Boundary Interpolation
Node positions along the cut boundary of the submodel extract displacement vectors from the coarse global mesh solution. Shape function interpolation calculates field values for submodel boundary nodes that do not coincide with global mesh nodes. Thermal fields and body forces transfer from global models to submodels to maintain consistent environmental loading.
Cut boundaries must lie sufficiently far from local geometric discontinuities to prevent artificial stress disturbances from affecting high-gradient zones. Structural reaction forces across the cut boundary verify static force equilibrium between coarse global models and refined submodels. Linear and quadratic interpolation schemes map displacement fields across solid element faces.
Submodel mesh refinement increases node density around stress risers until stress results converge within specified numerical tolerances. Material non-linearities, including plasticity and creep, execute within the submodel domain using driven boundary displacements. Thermal expansion mismatches between localized components generate internal stress fields under temperature loads.
Verification of boundary displacement profiles ensures seamless transition between global displacement solutions and local submodel boundaries. Elastoplastic material models in the submodel calculate localized plastic strain ranges for low-cycle fatigue assessment. Computational speed gains allow rapid design iteration of local bracket geometries and braze bead profiles.
Discrepancies between global and local force balances indicate improper cut boundary placement near high stiffness gradients. Automated submodeling scripts streamline boundary extraction and submodel execution across multi-load case simulation workflows.
Stress Resolution
Refined solid element meshes resolve stress concentrations at sharp geometric transitions with high spatial accuracy. Peak von Mises and principal stress values converge as element size decreases below critical geometric radii. Stress gradient accuracy enables reliable application of strain-life fatigue prediction algorithms.
Computational Efficiency
Global model run times remain manageable by maintaining coarse mesh densities across large structural housing volumes. Computational resources concentrate exclusively on small volume domains containing critical mechanical interfaces. Efficient solver execution enables extensive design optimization studies within practical engineering schedules.
