14th International Conference on Shot Peening

Analysis of the residual stress stability of high frequency mechanical impact (HFMI)-treated transverse stiffeners of mild steel (S355) and high strength steels (S700) under p (1/3) and straight-line shaped spectrum loading

D.Löschner, R. Schiller, P. Diekhoff,

I. Engelhardt, Th. Nitschke-Pagel, K. Dilger

Laboratory for Steel and Lightweight Structures, Institute for Material and Building Research, University of Applied Science Munich, Munich, Germany

Institut für Füge- und Schweißtechnik, Technische Universität Braunschweig

Langer Kamp 8, D-38106 Braunschweig, Germany

Abstract

Despite numerous studies on the effectiveness of high-frequency mechanical impact treatment (HFMI) the application of HFMI treatment and the associated increase in fatigue resistance is still being discussed. This reservation is based primarily on the assumption that the residual compressive stresses induced by HFMI treatment are reduced by variable amplitude loading (VAL) and may therefore lose their initial effect. This study analyses further results for the sequence effect of VAL of a p (1/3) and straight-line shaped spectrum loading on the fatigue strength as well as the residual stress behavior of HFMI-treated transverse stiffeners (TS) of mild steel (S355) and high strength steels (S700). Fatigue test results with Random and High-Low loading for the two states as-welded (AW) and HFMI-treated joints together with in-situ residual stress measurements will be presented. The effect of VA loading on the residual stress behavior of as-welded (AW) and HFMI-treated joints and on the