Numerical Study on Weld Magnification Method for a Semi-Circular Surface Crack Under an Arbitrary Stress Distribution

Marine structures are mainly constructed using welded components, and cyclic loadings trigger the fatigue cracks, mostly at the joints. Precise assessment of fatigue crack propagation (FCP) depends on the accuracy of stress intensity factors (SIFs) solutions. Magnification factors (M_k) have been proposed and widely employed in the calculation of SIFs for welded joints as a proven method to obtain SIFs accurately and efficiently. However, no previous study has reported the M_k equations for SIF solutions under arbitrary stress distributions. It is needed to derive such M_k equations so that arbitrary stress distributions can be considered in the estimation of SIFs and complications of analysis procedures can be reduced to some extent. In this report, M_k^IFM equations for T-butt joints with semi-circular surface cracks under arbitrary stress distributions are developed. The M_k^IFM and numerical results are achieved by employing the Influence Function Method (IFM) and the equations are developed using the Regression Analysis. The proposed M_k^IFM equations are validated for SIF evaluations under membrane loading and also for welding residual stress distributions. The validity of the proposed M_k^IFM equations is demonstrated against numerical solutions.