Residual Stresses and Critical Initial Flaw Size Analyses of Welds

An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Constellation Program (CxP) Ares I-X (AIX) Upper Stage Simulator (USS). A series of weld analyses were performed to determine the residual stresses in a critical region of the USS. Weld residual stresses can increase component constraint and the mean stress thereby impacting the fatigue life. The purpose of the USS weld analyses was to model the joining process using a variety of sequences to determine the ‘optimum’ sequence in terms of weld residual stresses and distortions. The factors examined in this study include the A516 Grade 70 steel weld design (single-V, double-V groove), weld sequence, boundary conditions, and material properties. The results of this weld analysis were included with the USS service loads to perform a fatigue and CIFS evaluation.