Stress analysis of the LHA-1 class superheater header by finite element method.

Abstract

Numerous cracks and leaks in the superheater header tube attachment welds in the LHA-1 class of amphibious assault ships have prompted an investigation by the Naval Sea Systems Command (NAVSEA). This thesis describes the stress analysis of the superheater header tube attachment region using a three dimensional axisymmetric Finite Element model. The SAP 80 structural analysis program was utilized to conduct the analysis. Both pre and post processors were employed to obtain graphical representations of the model as well as the results of the stress analysis. This thesis focuses primarily on thermally induced stresses produced in the header. Some results obtained for a nominal 100 Degree F temperature drop across the thickness of the superheater header wall yielded a maximum hoop stress of 19.01 (Ksi) and a maximum in plane stress of 1.58 (Ksi).