21. On Improving Thermoelastic Stress Analysis Data Near Edges of Discontinuities

The most serious stresses are often at the edges of geometric discontinuities, and thereby influencing the overall performance of a structure. Under adiabatic and reversible conditions, thermoelastic stress analysis (TSA) provides nondestructive full-field information of the first stress invariant in a cyclically loaded structure. However, TSA measurements at and near the edges of discontinuities, the regions of prime interest, are often unreliable due to the adverse influence of the surrounding ambient temperature as well as the movement associated with the cyclic loading. Moreover, TSA data at such locations are susceptible to nonadiabaticity because of high stress gradients, thus further supporting the need to predict stresses at edges. A method is presented here for correctly quantifying the often disregarded TSA data at the edges of a structure by making use of the linear elastic conditions of equilibrium and compatibility as well as applying the appropriate boundary conditions. The method is hybrid in the sense that experimental TSA data (excluding disregarded edge measurements) are combined with an analytical expression of the first stress invariant. The achieved improvement in thermoelastic data near discontinuities is demonstrated here for a tensile aluminum structure containing a central irregularly shaped cutout.