Experimental study on the material dynamic fracture properties by Instrumented Charpy Impact test with single specimen method

摘要

With the determination of load-time curve recorded by Amsler/Roell RKP 450 Instrumented Charpy Impact test and based on the Newton's Second Law, Impact character of a single standard V-notch specimen of X70 pipeline steel under the low temperature-70 ℃ was investigated by studying the impact energy distribution. It was revealed that maximum load point (F_m point) was not exact the dynamic crack initiation, which was detected somewhere prior and very close to F_m point by using Compliance Changing Rate method. This fact was also confirmed by Dynamic CTOD method. That is to say, Impact energy related to the F_m point (i.e. E_m) consists not only the crack initiation energy E_i, but a small part of crack extension energy as well. Ratio of E_i/E_m was found to be 0.90 just applicable to the material used here. Dynamic fracture toughness J_(1d) was then estimated by modified Rice equation. Crack extension behavior and dynamic crack growth resistance curve (J-Δa) during stable crack propagation period was carefully analyzed by Key Curve method. Finally, methods for evaluating tearing module T_(mat) and CTOD curve under the impact test were also briefly introduced in the paper.