Patent ID: 8649985

Claim:
A method of performing fatigue evaluation of a fatigue prone location of a tangible structure by converting multi-axial loading data of the fatigue prone location of the tangible structure to a set of equivalent constant amplitude loading data for the tangible structure, the method comprising: subjecting the fatigue prone location of the structure to one-time or repeated multi-axial variable amplitude loading; producing multi-axial loading data from the multi-axial variable amplitude loading to which the fatigue prone location is subjected; generating a multi-axial load locus representing the tangible structure by mapping load parameters of the multi-axial loading data into an equivalent space of dimension n, where n represents the number of independent stress or strain components used in the mapping; identifying a maximum range between two points on the load locus to define a loading path along at least a portion of the load locus, the loading path extending from a point of origin P to a point of termination Q; identifying any time-dependent interior turning points R and any corresponding projected turning points R* along the loading path from the point of origin P to the point of termination Q; counting half cycles in the loading path by referring to the interior and projected turning points R, R* along the loading path and to the point of origin P and the point of termination Q on the load locus; determining a stress range Δσ e , loading path length L, and virtual path length for each of the counted half cycles; determining additional stress ranges Δσ e , loading path lengths L, and virtual path lengths recursively for half cycles counted in additional loading paths on the load locus; transforming data representing the counted half cycles, the stress ranges Δσ e , the loading path lengths L, the virtual path lengths or combinations thereof, to a tangible set of equivalent constant amplitude loading data representing the tangible structure; and displaying the tangible set of equivalent constant amplitude loading data as a representation of the tangible structure.