ABSTRACT
Conventional engineering design is based on avoidance of failure by general plastic collapse. The material property specified in design codes is the flow stress: usually the yield stress or 0.2% proof stress, but occasionally, in older codes, the tensile strength. The higher safety factors applied for castings, as compared with wrought material, stem from fears that the castings might contain more inherent defects, which could lead to fast crack propagation at or the applied design stress. The prime aim of the safety factor is to take account of any extra stresses imposed during erection, fabrication, or service, which may raise the applied stress to the value required to cause plastic collapse and failure. In service, the stress concentrators of importance are crack-lire defects, particularly if these are situated in regions of high background stress, such as those around fillets, keyways, nozzle openings or hatchways.
