Patent ID: 9513200
Filing Date: 2016-12-06
CPC Classification: G01N

Claim Text:
1. A method comprising: determining a fatigue crack length and a fatigue crack angle of a fatigue crack of a machine component, wherein the fatigue crack angle is measured as an angle between a normal to a plane defined by the fatigue crack and a direction of the anticipated cyclic load force to be applied to the machine component; determining a component threshold stress intensity factor for the fatigue crack, wherein the component threshold stress intensity factor is determined from a dataset formed by at least conducting an asymmetric four point bend test on a test specimen having an initial notch, wherein the dataset includes at least one respective threshold stress intensity factor and at least one mixed-mode phase angle, wherein each respective threshold stress intensity factor of the at least one respective threshold stress intensity factor is associated with a corresponding mixed-mode phase angle of the at least one mixed-mode phase angle, and wherein the component threshold stress intensity factor is based at least in part on a threshold stress intensity factor associated with a mixed-mode phase angle that corresponds to the fatigue crack angle; determining a threshold crack length for the component threshold stress intensity factor based on the following equation: where a th is the threshold crack length, ΔK th is the component threshold stress intensity factor, Δσ is the anticipated stress cycle to be applied to the machine component, β is a geometry correction factor, and a′ is a small-crack correction factor; and categorizing a condition of the machine component based at least in part on a comparison between the threshold crack length and the fatigue crack length of the fatigue crack in the machine component.