Evaluation of dynamic fracture toughness parameters by instrumented Charpy test

This paper presents methods to determine two fracture mechanics parameters using load-deflection curve obtained from instrumented Charpy test. Two fracture mechanics parameters are dynamic fracture toughness (Jsub(d)) and material tearing modulus (Tsub(mat)). Jsub(d) is fracture resistance at crack initiation and it is necessary to detect the crack initiation point on the load-deflection curve for measurement of this value. On the other hand, Tsub(mat) is a parameter to characterize a stable crack growth and it is necessary for this to estimate an amount of crack extension. In this study, it is attempted, for the measurement of Jsub(d), to detect the crack initiation point by calculating the compliance change rate from a loaddeflection curve. Next, J-Δa curve is estimated by using a key curve method and Tsub(mat) is determined from its slope. In addition, Tsub(mat) is evaluated by combining KAISER's rebound compliance with PARIS-HUTCHINSON's Tsub(app) equation. The above results are compared with the ones of stop block test (which is a multiple specimens technique), and are discussed about those validity; a rather good agreement is ascertained. (author)