Overview of Fatigue Data for High Frequency Mechanical Impact Treated Welded Joints

Abstract

paper provides an overview of published experimental data on the fatigue strength of welded joints by high frequency mechanical impact (HFMI) treatment methods, In total, 414 data points from four specimen types are available,tests were performed using constant amplitude R = 0.1 axial tension fatigue, but some data for other R rations, variable amplitude testing and bending fatigue are also reported. An S-N slope of m = 5 gives a very good description of both individual data sets and of the composite data Design curve recommendations for the four joint types and for the structural stress-based design curve are given. HFMI treated specimens generally follow the same trend as experimental data for hammer peened specimens, but the degree of improvement is better. Data for large structures, at stress ratios other than R=0.1 and for variable amplitude loading are still needed in order to update the IIW guideline for post-weld improvement. There is a general trend for increasing fatigue strength improvement as a function of steel yield strength but this influence needs further study in order to develop guidelines. Quality assurance measures for HFMI treatment methods must also be defined.