Structural Stress Determination at a Hot-Spot

Abstract

Stress analysis by a finite element analysis program sometimes causes singularities in hot-spots. In a failure assessment, the structural stress, and membrane and bending stress should be determined in a highly stressed spot (hot-spot). When the structural stress at a hot-spot is disturbed by singularities, the stress result not only diverges, by reducing the element size, but also shows a decreased value compared to nominal stress because the stress is substituted into the von Mises equivalent stress equation. In the three-dimensional (3D) finite element model, it is hard to avoid the singularity problem at hot-spots particularly when it is subjected to loads in three axial directions. For the alternative, this study converts the 3D model into two-dimensional (2D) plane models to remove the singularity and to obtain reasonable structural stress values excluding the peak stress. The structural stress-estimating approaches applied in the 2D model were examined for whether they could avoid the structural stress reduction near the hot-spot with mesh insensitivity. The implemented approaches are stress linearization, single point away method, stress equilibrium, stress extrapolation, and the nodal force method. The results computed by each approach are compared and reconstructed to 3D stress by the Cauchy stress matrix. This study found that the difference in structural stress in 2D was eliminated after the 3D stress reconstruction.