Residual Stresses Management: Measurements, Fatigue Analysis and Beneficial Redistribution

Abstract

Residual stresses (RS) can significantly affect engineering properties of materials and structural components, notably fatigue life, distortion, dimensional stability, corrosion resistance. RS play an exceptionally significant role in fatigue of welded elements. The influence of RS on the multi-cycle fatigue life of butt and fillet welds can be compared with the effects of stress concentration. Even more significant are the effects of RS on the fatigue life of welded elements in the case of relieving harmful tensile RS and introducing beneficial compressive RS in the weld toe zones. The results of fatigue testing of welded specimens in as-welded condition and after application of ultrasonic peening showed that in case of non-load caring fillet welded joint in high strength steel, the redistribution of RS resulted in approximately two-fold increase in the limit stress range. A concept of residual stress management (RSM) and a number of engineering tools were proposed recently that address major aspects of RS in welds and welded structures. According to the concept, three major stages, i.e. RS determination, RS analysis and RS redistribution are considered and evaluated, either experimentally or theoretically to achieve the optimum performance of welded elements and structures. The main stages of RSM are considered in this paper. A number of new engineering tools such as ultrasonic computerized complex for RS measurement, software for analysis of the effect of RS on the fatigue life of welded elements as well as a new technology and, based on it, compact system for beneficial redistribution of RS by ultrasonic peening are introduced. Examples of industrial applications of the developed engineering tools for RS analysis and fatigue life improvement of welded elements and structures are discussed.