高温含缺陷结构与时间相关的失效评定图

针对高温含缺陷结构的稳态蠕变情况,在裂纹扩展控制参量JT积分的基础上建立了一个与时间相关的失效评定图,给出了与之相关的参量Kr、Lr、Lr^max,σ0.2^3以及等时应力应变曲线的定义和确定方法,详细讨论了材料的蠕变断裂韧性Kmat^c的试验测定方法、参数估算法以及图算法,并据此建立了2．25CrlMo钢—系列的高温失效评定曲线研究结果表明：当环境温度低于材料蠕变温度时．服役时间对2．25CrlMo钢的高温失效评定曲线影响不大,可以采用R6的通用失效评定曲线进行粗略评定;当环境温度高于材料蠕变温度时,服役时间越长、温度越高高温失效评定曲线与R6通用失效评定曲线相比变化越大．这时必须采用与时间相关的失效评定图。

Time-dependent Failure Assessment Diagram for Integrity Assessment of Defective Structure at Elevated Temperature

On the basis of the crack initiation and growth control parameterJT integral estimation, a time-dependent failure assessment diagram (TDFAD) for the steady creep condition of defective structure at elevated temperature was investigated in this work. The definition and calculation approach of parameters Kr, Lr, Lrmax, s0.2c as well as isochronous stress-strain curve, related to the TDFAD, were presented. Three methods for determining the material creep fracture toughness Kmatc, i.e., experimental measuring method, parameter estimating approach and graphic solution, were discussed in detail. Several families of failure assessment curves (FAC) for 2.25Cr1Mo at elevated temperature were constructed according to the presented procedure. The research results indicate that the effect of serve-time on the FAC is not much evident under the condition of environmental temperature lower than the material creep temperature, and the general FAC offered in R6 at ambient temperature can be applied in the engineering practices to give a rough assessment for high temperature structure. Whilst for the structure operated at temperature higher than the material creep temperature, the changes of the FACs compared to the general FAC in R6 will increase with serve-time prolonging and operating temperature elevating, and the TDFAD should be adopted in this case. The effect of service-time and environmental temperature on structure failure can be imaged rationally by the TDFAD proposed in this work.