Effect of Notch Size on Brittle Fracture Initiation (Second Report)

On Type of Notch and Fracture Initiation

Abstract

In this paper the brittle fracture initiation characteristics of base metal for a mild steel plate with a semi-elliptical surface notch, which was produced mechanically, were investigated. The notch depth varied systematically. The brittle crack initiated at the tip of semi-elliptical notch, and propagated initially in the direction of plate thickness even when the notch depth varied widely. The phenomenon was different from that for welded joint as mentioned in the previous paper, since the brittle crack propagated in the direction of specimen width for t₁/t≤0.6 in the latter case.
In this case the theoretical formula for semi-elliptical notch on the plate surface was proposed by Irwin can be applied for t₁/t=0.10.9.
Next, the phenomenon of brittle crack initiation for internal notch specimen with welded joint which were deposited by using two kinds of electrode for mild steel and stainless steel was investigated.
It was concluded that Irwin's formula could be applied only for the case where the brittle crack propagated initially into the direction of plate thickness, and, on the other hand, the fracture stress was approximately constant for the case where the brittle crack propagated initially into the direction of plate width.