【摘要】 本文企图从宏观和微观相结合的观点分析和讨论K_1c的物理意义及其影响因素。对于脆性断裂,通过表面能密度、裂纹尖端凝聚力场以及点阵“捕捉”作用说明K_1c的意义。用热力学原理分析了K判据的必要性和充分性,指出只有在裂纹尖端半径小于临界尺寸时,K判据才是必要和充分条件。 对于小范围屈服,裂纹尖端的钝化是通过尖端放射位错和吸引周围异号位错而形成的,这是最可能的物理过程。同时,着重指出Vitek的理论结果。 在弹塑性连续理论中,采纳了Orowan—Irwin有效断裂能密度的概念。用这概念及能量原理,本文建议要从试样塑性变形功中抽出属于K_1c组成部分的裂纹尖端塑性功。可以导出K_1c的表达式,形式上和陈篪的结果以及Hahn—Rosenfield的结果相似。影响K_1c的主要因素有:硬化率,杨氏樸量,抗拉强度,平面应变断裂真应变和一个适当的长度参数,其意义随断裂机制而异。其它冶金因素,例如晶粒度,可能通过断裂真应变影响K_1c。更多还原

【Abstract】 The paper is written with the hope to correlate the macroscopic andmicroscopic viewpoints in order to reveal the physical meaning of K_1c andits significant influential factors. In brittle fracture phenomena, the meaning of K_1c is discussed in termsof specific surface energy, cohesive force field at the crack tip and also thelattice trapping effect. It is pointed out that the K criterion can be a su-fficient condition as well as a necessary condition only under the case thatthe crack tip remains sharper than a critical size. For small scale yielding, the blunting of crack tip through the emissionof dislocations and the attraction of opposite dislocations around the tip isbelieved to be the most probable physical picture, with the emphasis beingput on the theoretical results of Vitek. In the continuum theory, it is suggested that the effective fracture energymay be calculated at least semi-quantitatively. This leads to an expressionof K_1c similar in form to the results of Chen- Chih and Hahn- Rosenfield.It is concluded that the following quantities are of prime importance thatmay affect K_1c: index of strain hardening rate, younsg’ modulus, tensilestrength, plane strain fracture strain and a suitable length parameter, theexact meaning of which depends upon the fracture mechanism.更多还原