The Crack-Arrest Properties of 9% Ni steel and its Weldment (4th Report)

Abstract

The objective of this paper is to clarify the mechanism of crack arrest behavior using surface-notched double tension test proposed in previous papers.The static and dynamic deformation behavior of the system measured were compared with the results of numerical analysis on centre crack model and single-edge crack model. The full thickness dynamic tear test was carried out to observe fracture phenomena associated with the crack initiation, propagation and arrest. The surface-notched Dynamic Tear test using the specimen with the sharp surface notches located in the crack initiation part and the crack propagation part was also performed to clarify the effect of the deformation at the surface portion of the specimen on the behavior of the crack initiation and propagation.It is noted that the test results obtained could deny the evaluation of the crack arrest toughness based on the K concept. According to the full thickness Dynamic Tear test, the main factor affecting the crack arrest should be considered the macroscopic plastic deformation and the resulting ductile fracture. The significance of the crack arrest was also confirmed by the surface-notched Dynamic Tear test.Many similarities in the fracture appearances were observed between in the surface-notched double tension test and in the Dynamic Tear test. It can be clearly seen that there was a close relationship between both test results.As a result, the full thickness Dynamic Tear test would be a convenient engineering test method in order to evaluate the crack arrest properties of materials.