G0301401 Method for Fatigue Life Evaluation in Aluminium Alloy Welding using Strain Singularity Parameters

Abstract

Welded structures are widely used for construction machines, automobiles, railway vehicles, etc. In these structures, the welded parts are generally the weakest points. In particular, the toes of welded and the tops of non-welded and welded cracks become causes of welding fractures because these are stress concentration points. Thus, a method for fatigue life evaluation that can evaluate these stress concentration points in a lump is required. In this study, a new evaluation method for welded parts using strain singularity parameters was developed. The conclusions are as follows: (a) Comparing strain approximation equation Δε = H_εr^<-λε> (Δε: Amplitude of elastic strain, r: Distance from stress concentration part, H_ε: Magnitude of strain singularity, λ_ε: Broadening of strain singularity) to the strain distribution of test specimens calculated using elastro-plastic analysis, the strain singularity parameters H_ε and λ_ε were derived. Using the parameters and fatigue life data that was obtained from the fatigue testing of V-groove specimens (Simulated crack length: 3-8 mm, non-offsetted), a fatigue-life surface was derived. The equation of the surface was logN=-5.3146logH_ε-4.3048λ_ε+21.6888. (b)After comparing the fatigue life calculated by the fatigue-life surface equation and the fatigue life derived by all types of specimens fatigue testing, the calculated fatigue life had approximately good agreement with the fatigue life derived in the test.