一、前言由于宇航、造船等工业的迅速发展,对结构材料的强度和韧性提出了越来越高的要求。随着材料强度的提高,难于予测的低应力脆性破坏倾向性就增大了。但过去防止脆性破坏的研究工作仅限于传统的韧性和塑性指标(如α_k、δ％,ψ％等等)。这些指标常被看做保证不发生脆断的安全因素;但却不能定量的用于强度设计。而只能根据经验积累,人为的规定一些相对数值做参考,所以,具有很大的盲目性。一系列的災难性破坏分析证明了这点。这些传统的韧性指标不适于评定高强度和超高强度材料抗脆性破坏的要求。这是由于结构材料在经过冶炼、加工等存在不可避免的缺陷(如气孔、夹杂、裂 I. Preface Due to the rapid development of industries such as aerospace and shipbuilding, higher and higher requirements have been put on the strength and toughness of structural materials. As material strength increases, the unpredictability of low stress brittle fracture tendencies increases. However, in the past, the research on preventing brittle failure was limited to the traditional toughness and plasticity indexes (such as α_k, δ%, ψ%, etc.). These indicators are often seen as security factors that will ensure no brittle fracture; however, they are not quantitatively used for strength design. But only based on the experience of accumulation, artificial relative to some of the provisions of the reference, therefore, has great blindness. A series of catastrophic damage analysis proved this point. These traditional toughness indicators are not suitable for assessing the resistance to brittle failure of high-strength and ultra-high-strength materials. This is due to the structural material after smelting, processing and other inevitable defects (such as porosity, inclusions, cracks