Increased accuracy of calculated fatigue resistance of welds through consideration of the statistical size effect within the notch stress concept

Abstract

AbstractThe notch stress concept has been established for fatigue life calculations of welded components. One of its advantages is that the S-N curve is not based on an S-N curve catalog in which the user has to identify a suitable FAT class; instead, a single S-N curve (based on modeling, failure location, and material) is used for different weld geometries. In return, however, the weld needs to be modeled in a detailed manner for finite element analysis. The evaluation of experimental fatigue results collected in a database shows a relatively high degree of scattering (low accuracy) of the strengths calculated according to the notch stress concept. With fatigue tests on different specimen geometries manufactured from the same welded base plates, a correlation between the highly stressed weld seam length and the experimentally determined notch stress strength can be observed. The fatigue strength decreases with the increasing length of the highly stressed weld seam area. The latter quantity can be calculated using the finite element simulations that are needed to determine the notch stress. The presented results are used to describe the statistical size effect as a qualitative influence and quantitative support factor that can be used within the notch stress concept to increase its accuracy.