Further enhancing fatigue properties with HFMI by customized edge treatment

Author:  J. Schubnell1, S. Fliegener1 and M. Farajian2
Source:  ICSP14 Milan
Doc ID:  2022045
Year of Publication:  2022
Abstract:  
Free corners and edges are potential weak points for fatigue crack initiation at High Frequency Mechanical Impact (HFMI) treated welded joints even if the treated welded seam itself shows a high fatigue strength. In this study the residual stress state around cutting edges of HFMl-treated notched and welded specimens were investigated. For this, X-ray diffraction (XRD) technique and Finite Element (FE) Analysis were used. It is verified that no compressive residual stresses close to the edges were present. Fatigue tests were performed at notched specimens made of S960QL steel. Some specimens were HFMltreated at the cutting edges with a concave pin. This additional treatment leads to a shift of the crack initiation location from the edge to the center of the specimen and to a significant increase of fatigue life. HFMI edge-treatment of welded joints showed in some cases that the edge treatment may also cause defects that could lead to crack initiation even from treated edges.