A Spectrum Truncation and Damage Tolerance Study Associated with the C-5A Outboard Pylon Aft Truss Lugs.

摘要

A simplified lug specimen configuration is subjected to two load spectra derived from the same exceedance data: (1) a 17level block loading program,and (2) a 14-mission flight-by-flight loading program. Crack growth data from the two spectra for this PH 13-8Mo material are compared on a life basis;each spectrum contained an equal number of Ground Air Ground (GAG) cycles per lifetime. An analysis of the effect associated with the degree of truncation to which the flight spectrum could be subjected was performed using the conservative no retardation -no load interaction crack growth model and the Willenborg crack growth retardation model. The stress intensity factor calibration developed using finite element techniques is supplemented with stress intensity factor values obtained using the Anderson -James inverse approach. Additional tests on 7075-T6aluminum are described which investigate the importance of load redundancy. (Author)