TWI Industrial Member Report Summary 278/1985
By M G Dawes
This report reviews the objectives, development and limitations of the crack tip opening displacement (CTOD) design curve approach to the avoidance of brittle fracture. Attention is drawn to the fact that, although the existing design curve was based on a consideration of gross-section strains that might exceed yield, the general application of the curve to such high strains should be limited to small cracks in elastically contained yielding situations, i.e. regions of high local strains in design situations where the nominal or gross-section stresses are less than the yield strength of the material concerned. To overcome some of these limitations, a simple modification to the CTOD design curve approach is proposed. This allows an assessment of through-thickness crack length to plate width ratios of up to 0.5, and avoids any need for separate assessments of failure by tear instability or plastic collapse. A review and recommendations are made concerning material properties, and the various assumptions that may be necessary when applying the CTOD design curve approach to plain materials and welded structures.