Patent ID: 8532941

Claim:
A method for fatigue life estimation of a component operable under cyclic stress, comprising: obtaining, from strain controlled low cycle fatigue test data of the component or representative specimen of the component, a first set of data samples comprising measured stress amplitude values for varying test strain levels, and a second set of data samples comprising a plurality of measured cycles to crack initiation for varying test strain levels, and operating a processing device for: fitting a first low cycle fatigue material curve on the first set of data samples and a second low cycle fatigue material curve on the second set of data samples, the first curve and the second curve are defined respectively by a first and a second set of curve parameters, wherein the values of the first and said second set of curve parameters are determined so as to maximize a likelihood function defined as L := ∏ j = 1 n ⁢ ⁢ f σ ⁡ ( σ a , j ❘ θ C ⁢ ⁢ 1 , ɛ a , j ) · ∏ k = 1 m ⁢ ⁢ f N ⁡ ( N i , k ❘ θ C ⁢ ⁢ 2 , ɛ a , k ) , wherein f σ and f N are probability distribution functions, ε a,j and ε a,k represent test strain levels in the first and second sets of data samples respectively, σ a,j represents measured stress amplitude values in the first set of data samples N i,k represents the plurality of measured cycles to crack initiation in the second set of data samples, θ C1 and θ C2 represent the first set and second set of curve parameters respectively; and determining an estimated fatigue life of the component using the first and second low cycle fatigue material curves.