REEVALUATION OF THERMAL-SHOCK EXPERIMENT RESULTS BASED ON THE VTT APPROACH FOR STATISTICAL TREATMENT OF FRACTURE-TOUGHNESS DATA

One important step in fracture mechanical research has been thermal sh ock experiments (TSE). The TSEs are exceptional because many of them h ad extremely long crack fronts. As a trend, the TSE initiation fractur e toughness results form a lower bound to the small specimen data used for material characterization. Presently, work is under way to produc e an ASTM testing standard for fracture toughness testing in the trans ition region. The standard is based on the VTT approach for statistica l treatment of fracture toughness data. Key components in the VTT appr oach are statistical expressions for describing the data scatter and f or predicting a specimens size effect, and an expression for the fract ure toughness temperature dependence. In order to examine the validity of the statistical size effect assumption, the TSEs were reevaluated with the VTT approach. For all the TSEs investigated, the application of the statistical size correction has had the effect of bringing the material characterization data in agreement with the actual TSE result s. Furthermore, the application of a statistically defined size-correc ted lower bound toughness estimate, based on the small specimen materi al characterization data and the master curve, yield a conservative, b ut realistic, estimate of the TSE failure behaviour. (C) 1997 Elsevier Science S.A.