The presence of residual stresses affects the fatigue response of welded components. In the present study of a thick welded cantilever specimen, residual stresses were measured in an as-welded A36 steel sample and in a sample subjected to a long history of bending loads where minimal local plasticity is expected at the fatigue hot-spot weld toe. Extensive XRD measurements describe the residual stress state in a large region in front of the weld toe both in an untested as-welded sample and in a sample subjected to a long load history that generated an estimated 0.001 strain amplitude at the stress concentration zone at the weld toe. The results show that such a test will moderately alter the welding induced residual stresses. Fatigue life prediction methods need to be aware that such alterations are possible and incorporate the effects of such cyclic stress relaxation in life computations.
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Themes: Residual Stress in Fatigue and Fracture
UNCERTAINTY QUANTIFICATION IN RESIDUAL STRESS AFFECTED FATIGUE CRACK GROWTH LIFE
In recent years a number of studies have been performed in which the impact of residual stress on structural performance, especially fatigue performance, has been evaluated both experimentally and analytically. These efforts are leading to an emerging paradigm in which residual stresses are represented explicitly in structural design, analysis, manufacturing and sustainment calculations. In order for this new approach to be become minimally viable, it is necessary to be able to quantify both the residual stresses in the structural component in question, and the impact that those residual stresses have on component strength and life. However, to achieve general acceptance, especially for critical applications in which the presence of the residual stress directly impacts whether or not the component will meet its design requirements, deterministic quantification alone may not be sufficient; it may be necessary to quantify the uncertainties in both the residual stresses and the resulting fatigue lives.
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