Development of fatigue life evaluation technique using strain gradient parameters

Abstract

We developed a new technique for evaluating the fatigue life of welding using strain gradient parameters. These parameters are composed of two parameters. One of them H_ε shows the magnitude of the strain concentration points, and the other parameters λ_ε shows the gradient of strain concentration points. These parameters can arrange the fatigue life of welding N in an equation called as face fatigue life. The equation’s basic form is logN=alogH_ε+bλ_ε+c (a,b,c are constant). In this report, we considered how to use the equation for the design process and showed two efficient use cases. One is the use of logN-logH_ε with constant λ_ε. This relationship shows the load tolerance and required plate thickness. The other is the use of logN-λ_ε with const H_ε. This relationship shows the crack length tolerance and required a radius of curvature of the strain concentration points of welding.