User friendly assessment of stress intensity factor in thermal shocked cracked structures with finite boundary restraint

Evaluation of thermal shock stress intensity factors is a problem of interest in many industries. Many structures experiencing thermal shock can be accurately idealised to comprise finite length elastically/thermo-elastically restrained plates and finite length elastically/thermo-elastically restrained hollow cylinders. This article describes how a ‘user-friendly‘ Compliance Adjusted Weight Function (CAWF) approach can be used to assess mode I stress intensity factor associated with the creep-free thermal shock of such structure with edge and semi-elliptical surface cracks. Based upon a mechanical weight function philosophy, the CAWF approach utilises a mechanical weight function analysis, available mechanical weight functions/geometry factors attributed to an equivalent semi-infinite cracked structure, a crack-free finite element analysis and an elastic Line-Spring analysis of compliance. The need for deriving different weight functions at each configuration of boundary restraint is therefore removed and the results of several verification exercises highlight that the CAWF approach is suitable for estimates within 5–10% of benchmark fracture mechanics finite element values. This suitability of the CAWF approach is valid for a wide range of cracked plate configurations, cracked hollow cylinder configurations and boundary restraint. An exception to this suitability is observed when examining semi-elliptical surface crack configurations and a free or near free boundary restraint condition. Adjustments to correction for this ‘free boundary effect’ are discussed elsewhere.