Fatigue Life Prediction of Welded Joints—a Re‐assessment

Abstract

Fatigue life prediction of welded joints needs an accurate and exhaustive theoretical Fracture Mechanics characterization of weld toe crack propagation. The method proposed by Albrecht et al. leads rapidly to accurate solutions of the LEFM AK-parameter. However, non-LEFM short crack behavior within the notch (weld toe) plastic zone must be taken into account. Available information on notch fatigue is surveyed, and practical cases where short crack growth is likely to occur are identified. Based on an elastoplastic finite element analysis, the LEFM validity limits and errors resulting from the misuse of LEFM in fatigue life prediction are quantified. NOMENCLATUREcrack length preexisting defect length, final crack length extent of the notch plastic zone plate thickness, stiffener thickness major semi-diameter of a semi-elliptical crack Paris law coefficients crack growth rate size of the crack tip cyclic (monotonic) plastic zone Young's modulus plastic constraint factor plastic modulus stress intensity factor, range of K, effective range of K value of K at crack closure weld leg length correction factors in K-expression fatigue life S~,,iSrn,, nominal stress, range of S value of S at crack closure relative fraction of the nominal stress range for which the crack tip is open stabilized value of U,, outside the notch plastic zone singularity of a V-notch stress field gamma function conventional AK threshold effective AK threshold weld toe angle Poisson-ratio local stress * cyclic yield stress, monotonic yield stress correction factor in K-expression 180"-0 (V-notch angle)

Influence of Welding Residual Stresses on the Closure and Propagation Behavior of Fatigue Cracks Growing at a Fillet Weld Toe

“…Previous investigations were performed on stress relieved joints [2,3]. The stress field around the V-notched weld toe is singular: u _ r-a where a -0.333 for a 450 toe angle.…”

A new model to predict the fatigue life of flux cored arc welded cruciform joints containing LOP defects

“…The important factors, which have more influence on the fatigue life of welded cruciform joints with LOP defects have been identified [4][5][6][7][8] and shown in Fig. 1.…”

“…They are, (i) the ratio between initial LOP length (2a) and fillet width (2W); (ii) the ratio between weld leg length (L) and plate thickness (Tp); (iii) Fillet Angle (0) or weld profile and (iv) stress range (Ac~). The feasible range for the above factors are selected [4][5][6][7][8] cessing the experimental data, the upper and lower limit of the factors are coded as +1 and -1 respectively and the coded values of any intermediate levels can be calculated by the expression [9].…”

Bimodal Concept of High‐cycle Fatigue Life Prediction for Constant and Variable Amplitude Fatigue

“…Verreman et al . [ 17] used this method for the determination of the F G factor of a cruciform‐welded joint and compared it with the accurate solution obtained by Smith [ 18] using high‐order crack tip elements with an inverse square root singularity. They reported differences smaller than 6%, so this method can be considered accurate for engineering purposes.…”