Crack significance evaluation with special reference to welded structures

Abstract

Fracture mechanics parameters (stress intensity factor K-I and its critical value K-Ic, crack opening displacement, and the contour J integral) are originally defined for static and quasistatic loading conditions. On the basis of theoretical background, standard test methods for the experimental determination of their specific values were developed. Structural integrity analysis requires the extension of application of these parameters to other types of loading. We propose new parameters for stress corrosion (stress corrosion cracking threshold K-Isco), for cyclic loading (stress intensity factor range Delta K and fatigue-threshold Delta K-th), and for creeping at elevated temperatures (C* and C-t integrals). The structural integrity of welded structures is mainly affected by cracks in welded joints. We demonstrate the practical application of fracture mechanics parameters to the evaluation of structural integrity under the above-mentioned loading conditions.