Fracture Analysis of the High-Frequency Sail Array Projector's Titanium Mounting Bolts Subjected to UNDEX Shock.

摘要

The installation of the High-Frequency Sail Array (HFSA) projector is subject to tight alignment tolerances. Any installation modifications necessitate the use of a machined shim positioned within the projector housing-to-ship foundation joint. Because this shim increases the stresses within the titanium mounting bolts, subsequent fractures must be evaluated for survivability. A linear elastic fracture analysis was performed on the HFSA mounting bolts for the following reasons: (1) to predict the critical crack size, (2) to ensure that crack growth for a specified shock loading case would not occur, and (3) to determine the minimum mode-l fracture toughness required for the mounting bolts. Electric Boat Corporation's global shock model of the projector, called the Dynamic Design Analysis Method, was used to predict the maximum bolt shear stress for a specific underwater explosion. Localized bolt bending stresses caused by joint eccentricity were then determined using a closed-form solution. After the relevant stress data were determined, the NASGRO Fracture and Fatigue Prediction Program was invoked to assess failure by fracture. The mode-l stress intensity factor was computed and compared to the fracture toughness of the recommended bolt material.