Fracture Toughness Evaluation From Instrumented Sub-Size Charpy-Type Tests

Abstract

The possibilities to derive fracture toughness from small specimens are naturally limited due to constraint requirements which are especially restrictive in toughness testing. In this paper two possible ways are explored theoretically and experimentally to use instrumented sub-size Charpy tests to evaluate fracture toughness related data that are essentially size independent (and can be compared with the ones obtained from larger specimens, e.g. standard Charpy specimens). The first way is to adapt a J-R-curve estimation procedure for analyzing instrumented Charpy tests that has proven to deliver conservative fracture toughness data. The second is to scale-up the characteristic values of the instrumented sub-size tests, which are determined to be the total fracture energy and the energy consumed up to maximum load, and then use the evaluation procedure for standard Charpy specimens mentioned above. The corresponding scaling laws are derived analytically, using simplified mechanical models. The results are compared with experimental data obtained from different specimen sizes.