【摘要】 用弹塑性有限元 (FEM)方法分析了 C- Mn钢不同缺口夹角 4点弯曲试样(4 PB)缺口前的应力 -应变场分布 .精确测量了解理起裂源距缺口根部的距离和细观解理断裂应力σf.结果表明 :当缺口夹角从 10°增加到 90°时 ,断裂时的高应力、应变分布产生了明显变化 ,而σf 值相对保持不变 ;解理的临界事件也没有变化 ,表现为铁素体晶粒尺寸的裂纹扩展进入邻近基体 .因而 σf 主要由临界裂纹的长度决定 ,缺口夹角及与其相关的高应力体积对σf 的值几乎没有影响更多还原

【Abstract】 An elastic plastic finite element method (FEM) is used to analyze stress and strain distributions ahead of the notches with various opening angles in 4 point bending (4PB) specimens of C Mn steel. By accurately measuring the distances of cleavage initiation sites from notch roots, the local cleavage fracture stress σ f is measured. By increasing the notch opening angle from 10° to 90°, the distributions of high stress and strain at the moment of fracturing show considerable change. However, the σ f keeps relatively constant. The critical fracture event is thus shown to be identical, i.e. the propagation of a ferrite grain-sized crack into the neighboring matrix has taken place. It is concluded that σ f is mainly determined by the length of the critical microcrack, the notch opening angle and its associated stress volume have little effects on the σ f.更多还原