Shot Peening Of Welded Joints And Residual Stress Relaxation During Fatigue

Author:  Bignonnet, Lieurade, Picouet, Castex
Source:  Conf Proc: ICSP-3, (p.585-594)
Doc ID:  1987085
Year of Publication:  1987
Abstract:  
Metal structures, the numbers of which increase as the years go by, are often subjected to fatigue loadings, and it is necessary to guard against the risk of failure due to this type ofloading. On the other hand, in order to produce lighter structures, designers now opt for the use of high-strength steels (HSS). The steel producers have learnt how to manufacture such steels. However, the advantages which are obtained by the use of "modern" steels, particularly the HSS steels, can be limited by the fatigue strength of welded joints. We know, in fact, that, for as welded joints (with no final treatment), the major part of the fatigue life is wiped out by the propagation of cracks initiated by defects at the weld toes. Since the propagation characteristics of low- and high-strength steels are not significantly different, the sole means of improving the fatigue life os HSS welded joints lies in extending the time necessary for crack initiation. For this, it is necessary to apply post-weld improvement treatments to the most highly-stressed areas, so as to eliminate defects introduced during the welding (undercuts, etc), or to nullify their harmful effects. The results hereby presented thus concern the use of these final treatment techniques on HSS welded joints formed of such steels, of an improved welding procedure, and of the final treatment of the weld beads by shot-peening.