Patent ID: 7623973
Filing Date: 2009-11-24
Classification: G01M,G06F

Abstract:
1. A method of predicting fatigue life for an aluminum based casting where at least one fatigue crack initiation site is presumed or determined to be present therein, said method comprising: using extreme value statistical methods to estimate an upper bound initiation site size expected to occur in the casting; and calculating on a computer said fatigue life based on said initiation site size using multiscale fatigue equations wherein a choice of which of said multiscale fatigue equations is selected is based upon at least one of a predominant form of said upper bound initiation site and a mean free path through an aluminum matrix of said aluminum based casting, wherein said predominant form of said upper bound initiation site comprises at least one of a casting flaw, a second phase particle and a persistent slip band, wherein said calculating comprises: using the equation in situations where said upper bound initiation site predominantly comprises said casting flaw such that a maximum flaw size of said casting flaw is larger than a critical size, whereas in situations where said maximum flaw size is smaller than said critical size, using the equation using the equation in situations where said upper bound initiation site predominantly comprises said second phase particle and where a mean free path through an aluminum matrix associated with transgranular crack propagation is present and evidence of at least one of cracking and debonding of said second phase particle is present or anticipated, whereas in situations where said mean free path through said aluminum matrix associated with intergranular crack propagation is present and evidence of at least one of cracking and debonding of said second phase particle is present or anticipated, using the equation using the equation in situations where said upper bound initiation site predominantly comprises said persistent slip band and where a size of said persistent slip band is constrained by a mean free path through said aluminum matrix that is smaller than a grain size is present and evidence of at least one of cracking and debonding of said second phase particle is not present or anticipated, whereas in situations where said initiation site predominantly comprises said persistent slip band and where a size of said persistent slip band is unconstrained by a mean free path through the aluminum matrix that is smaller than a grain size is present and evidence of at least one of cracking and debonding of said second phase particle is not present or anticipated, using the equation wherein C