Size effects on residual stress and fatigue crack growth in friction stir welded 2195-T8 aluminium – Part II: Modelling

Abstract

The use of residual K (K res) approaches for prediction of fatigue crack growth rates in residual stress fields was studied. Finite element models of the samples were built and the measured residual stress data put into the model. The virtual crack closure technique (VCCT) was used to calculate res K (stress intensity factor from residual stress) together with its changes with crack length using data from the part I paper. Local K res values were used to calculate effective R values. K op and ΔK eff values throughout the crack path in the weld were calculated. The master curve approach was used to relate these to corresponding values for crack growth rates. Predicted crack growth rates were compared with experimental results. Changes in crack growth rate found as the crack grows through the weld can successfully be predicted via application of this closure based model. Agreement between predictions and experimental data was best for tensile residual stress fields and was not as exact in compression. Possible reasons for this discrepancy are discussed.

Aluminum friction stir welds: Review of fatigue parameter data and probabilistic fracture mechanics analysis

“…While the residual stress distribution through the thickness is normally self-equilibrating, most of the fatigue life is spent during near surface small crack growth, so the residual stress at the surface is the most important from the point of view of fatigue behavior. Although Mahoney [80] found compressive stresses, the data obtained in this work show that they can be tensile and compressive [81][82][83][84][85][86][87], as Fig. 9 presents.…”

Recovery of fatigue life using laser peening on 2024‐T351 aluminium sheet containing scratch damage: The role of residual stress

“…The effect on fatigue crack growth of the residual stress field was modelled using two approaches to calculation of ∆K eff ; namely, modified superposition (M.SP) and the Newman crack closure equation . The modified superposition method is equivalent to the well‐known superposition approach for K tot,max and when K tot,min is greater than zero.…”

Studies on Quasi-Static and Fatigue Crack Propagation Behaviours in Friction Stir Welded Joints Using Peridynamic Theory

“…Furthermore, cracks in the samples are parallel to the weld. In this case, the effect of residual stress can be ignored [51]. Any differences in crack path and growth rate observed can be ascribed to material fracture toughness and load effects [9].…”