J. Phys. IV France
Volume 110, September 2003
Page(s) 551 - 557

J. Phys. IV France
110 (2003) 551
DOI: 10.1051/jp4:20020751

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

F. Jian, D. Fulian and W. Chengzhong

Baosteel Research Institute, Baoshan Iron & Steel Co. Ltd., 201900 Shanghai, P.R. China

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  $^{\circ}$C was investigated by studying the impact energy distribution. It was revealed that maximum load point (F $_{\rm m}$ point) was not exact the dynamic crack initiation, which was detected somewhere prior and very close to F $_{\rm m}$ 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 $_{\rm m}$ point (i.e. E $_{\rm m}$) consists not only the crack initiation energy E $_{\rm i}$, but a small part of crack extension energy as well. Ratio of E $_{\rm i}$/E $_{\rm m}$ was found to be 0.90 just applicable to the material used here. Dynamic fracture toughness J $_{\rm Jd}$ was then estimated by modified Rice equation. Crack extension behavior and dynamic crack growth resistance curve (J- $\Delta$a) during stable crack propagation period was carefully analyzed by Key Curve method. Finally, methods for evaluating tearing module T $_{\rm mat}$, and CTOD curve under the impact test were also briefly introduced in the paper.

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