Abstract
AbstractResidual stresses affect the fatigue strength of welded structures and components. A common sample type used for studies on residual stress effects is the fillet-welded longitudinal gusset. This sample type shows in fatigue tests significant residual stress effects. But the mechanisms of residual stress generation are not clarified for this sample type yet. High tensile residual stresses in the surface layer near the weld toe could not be proven by experimental methods but are generally assumed. Here presented are results from experimental and numerical investigations on welding residual stress generation. Specimens with single and multilayer fillet welds have been produced as well as simplified curved multilayer deposition welds studying residual stress build-up. Temperature measurements have been conducted during welding examining the influence of austenite phase transformation. Residual stresses have been determined by means of X-ray diffraction at the surface as well as by neutron diffraction over specimen thickness. Further, the mechanisms of residual stress build-up have been evaluated by finite element calculations. It could be shown that the austenite phase transformation has significant effect on the residual stresses near the weld toe also for this sample type.
Highlights
Welding is common in all engineering fields and is often used for steel structures that are loaded by vibration loading
The results presented here are from measurements made with the E3 experiment at Helmholtz Zentrum Berlin für Materialien und Energie (BER II)
Low tensile or even compressive residual stresses can be expected in the heat-affected zone (HAZ)
Summary
Welding is common in all engineering fields and is often used for steel structures that are loaded by vibration loading. The fatigue strength of welded structures and components is influenced by many parameters which characterize the loading itself or the weld. Among the parameters affecting the fatigue strength are welding-induced residual stresses. Apart from allowable stress levels, the knee point position of design S-N curves is suspected to be affected by residual stresses. [4] observed a shift of the knee point position for steel plates with fillet-welded longitudinal stiffeners to a lower number of load cycles by thermal stress relief. This was explained by relieving high tensile residual stresses. Residual stresses affect the brittle fracture behavior, the crack propagation rate and they must always be considered in combination with welding distortion
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