Statistical Analysis on the Plane Bending Fatigue Life of Butt and Cruciform Fillet Welded Joints

Abstract

Reversed plane bending fatigue tests were carried out in intermediate and high cycle ranges using Schenk type testing machines. Types of specimens were plane, butt welded joint and cruciform fillet welded joint and their material was mild steel (SM 41 B) of 6 mm thickness. For each type of specimens, 35 to 50 pieces were tested at the same stress level and three different of stress amplitudes were imposed. Test results were examined by a statistical analysis. The main conclusions obtained are as follows: 1. Statistical distribution of fatigue life for plane specimen, butt welded joint and fillet welded joint fitted fairly well in logarithmic normal and Weibull distribution rather than normal distribution. 2. The scatter range of fatigue life of welded joints had little correlation with the shape of reinforcement and was the same order as that of plane specimen. 3. The ratio of crack initiation life to fracture life for welded joints was nearly equal to 0.7. 4. Statistical distribution of flank angle θ and toe radius ρ of welded joints was represented by logarithmic normal distribution, and that of bead height h and bead length l of joints was represented by normal distribution.