Welding residual stresses as needed for the prediction of fatigue crack propagation and fatigue strength

Short fatigue crack growth in welded joints described by the effective cyclic J-integral

“…At lower stress amplitude, the stress relieved specimens lead experimentally to shorter fatigue lives compared to the as-welded specimens. This can be explained by the fact that according to residual stress measurements [23], the as-welded specimens exhibit compressive residual stresses, which lead to longer fatigue lives. At higher stress amplitude, both experimental and numerical results show almost no influence of welding residual stresses on the fatigue life.…”

“…The specimen geometry, material parameters, boundary conditions (including the gradual definition of contacts between the crack faces) and applied loads are needed here. If residual stresses are to be considered, they are inserted by using a procedure described by the authors in [18,23].…”

“…Only two load cycles were applied for every crack length configuration in order to restrict the FEcalculation time. In addition, two load cycles were applied before the first node release so that the residual stress relaxation/redistribution can be taken into account [18,23]. The crack extension was done at positive nominal stress (in order to satisfy the physical requirement that only an opened crack can propagate) and the increase in crack depth ∆ was chosen to be 0,05 mm for semi-circular cracks (3D calculations) and 0,01 mm for continuous cracks (modelled by using 2D models) respectively.…”

Numerical and experimental validation of residual stresses of laser‐welded joints and their influence on the fatigue behaviour

“…Lap joint by laser welding is a joining technique widely used in aerospace and automotive structures because this technique requires less restrictive joint dimensional tolerances and joins two components most easily and effectively; however, the structure with lap joint is subjected frequently to fatigue failures. The fatigue strength of these structures is influenced by crack‐like defects such as gas pores and lack of penetration at weld root that produce high stress concentration; moreover, the presence of residual stresses caused by complex thermal cycles in the weld produced by transient thermal stress and changes in the microstructure of the heat‐affected zone can reduce the performance of welded structures; in fact, high tensile residual stress distribution, reaching the yield magnitude in areas near the weld, can affect the fatigue behaviour of welds.…”

Pattern and Direction of Microstrain in Q&T Steel Weld Joint

“…Meanwhile, the residual stresses are the most manufacturing processes involving the deformation of a material [8]. The residual stress of welding has an impact on the performance of welded structures, fracture resistance, resistance to fatigue crack propagation, fatigue strength and fatigue period [9]. The residual stress has a strong effect on the performance of the product.…”