一、前言 在构件安全评定中,经常采用的方法有转变温度方法和断裂力学方法。前者是确定构件的临界温度,且据此来评定构件的安全工作性能。显然,这种准则难于适应设计需要,因为设计者最为关心的是既定结构在其特定工作温度下的抗断裂性能,而不是其随温度的变化情况。断裂力学准则注意了这一事实,因而采用特定条件下的允许裂纹尺寸这一概念来评定构件的 First, the preface In component safety assessment, the methods often used are temperature transformation methods and fracture mechanics. The former is to determine the critical temperature of the component, and accordingly evaluate the safe working performance of the component. Obviously, this guideline is difficult to adapt to design needs because designers are most concerned with the fracture resistance of a given structure at its specific operating temperature, not its change with temperature. The fracture mechanics guidelines take note of this fact and therefore adopt the concept of allowable crack size under specific conditions to assess the component’s