Fracture toughness approach to steel castings quality assurance

Abstract

Factors of safety are discussed in relation to the design of steel castings. The adoption of more critical design policies is important to the marketfor steel castings, and a fracture mechanics approach to design arzdflaw acceptance is described. A sensitivity analysis has shown that a large majority of K_IC results for cast steels should be correct to ±1MN/m^3/2 at K_IC values of about 50 and ±1.5MN/m^3/2 at K ^IC values of about 100 MN/m^3/2 Calculations are made for critical flaw sizes in cast steels of wide-ranging K _IC values, although it is emphasized that these are under idealized conditions and the relationship to foundry-type flaw sizes has yet to be demonstrated. Furthermore, although the application of non-destructive testing to the sizing of flaws is sufficiently accurate to allow the application of basic fracture mechanics principles, refined or new techniques for accurate flaw sizing must be developed. Nevertheless. sufficient data are available for the broad principles to be applied, and these are discussed in relation to specifications and quality assurance.