| Defect is one of the main reasons that caused high temperature component failure and even lead to catastrophic accidents. The life prediction of high temperature components containing defects need to obtain accurate crack propagation rate. At present C*correlation method is widely used in the creep crack growth rate analysis. Reference stress method and EPRI engineering estimation method are mainly included. Common methods of calculating C*are evaluated based on the previous research work. This paper mainly includes the following work.1. The currently widely used reference stress methods of calculating C*are evaluated. The C*that obtained by reference stress method based on the R6local solutions, R6global solutions and Kim optimization limit load solutions are safe. But each solution has prodigious difference. The accuracy of each solution needs to be improved.2. In view of the above question, the feasibility of EPRI-C*engineering estimation method is described from the principle and finite element analysis aspects. EPRI-C*engineering estimation method can be used as a more accurate method.3. The key point of EPRI-C*engineering method is hc solution. The existing h1solution is less and not accurate. High temperature solution hc under different crack size and creep index combination are given using finite element software. High temperature solution hc calculating creep crack parameter in engineering estimation method are enriched.4. hc solution used in the EPRI-C*engineering estimation method is a parameter that related with material, structure and defect geometry. The dimensions of hc form are more. So hc solution is cumbersome to use. Therefore, improved EPRI-C*estimation method is set up according to simplified theory and process method in the h1coefficient of normal temperature J integral by Sun Liang. Improved EPRI-C*engineering estimation method is convenient and the accuracy is the same with the original EPRI-C*engineering estimation method. |
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