Systematic studies had shown that welding residual stresses might lead to a significant reduction in fatigue strength of welded components. However the effects of residual stress are not sufficiently reflected in corresponding codes and regulations for fatigue assessments. The objective of the study described in this paper is to identify the residual stress distribution and relaxation in specimens with welded longitudinal attachment and welded panel which represents large scale model of ship structural detail, and compare results of experimental and numerical analyses. The ultrasonic measurements of residual stress were performed using the UltraMARS system developed at ITL Inc. (Markham, Canada) within Lloyds Register/DSME (DAEWOO Shipbuilding and Marine Engineering CO., LTD) Joint Project. A numerical simulation of residual stress relaxation under fatigue load was carried out at INHA University, South Korea. This study is considered as a first stage of a program focused on the analysis of residual stresses and their redistribution in welded elements under the effect of cyclic loading. The obtained data will be used for fatigue analysis of welded joints at different conditions of cyclic loading.
Residual stresses can significantly affect engineering properties of materials and structural components, notably fatigue life, distortion, dimensional stability, corrosion resistance, brittle fracture (Handbook, 2005). Such effects usually lead to considerable expenditures in repairs and restoration of parts, equipment and structures. For that reason, the residual stress analysis is an important stage in the design of parts and structural elements and in the estimation of their reliability under real service conditions. Systematic studies had shown that, for instance, welding residual stresses might lead to a drastic reduction in fatigue strength of welded elements. In multi-cycle fatigue (N>106 cycles of loading), the effect of residual stresses can be compared with the effect of stress concentration (Trufyakov, V, et al, 1995).
