The methods of estimating the creep-fracture mechanics parameter C[t] proposed by Riedel, Webster, Ainsworth, and their respective co-workers have been reviewed and extended. Quantitative estimates for C[t] have been obtained for the infinite centre cracked plate (CCP) and compact tension (CT) specimens using uniaxial creep strain and rupture data for 1 CrMoV steel at 565°C. It has been shown that the estimates substantially differ for each method and on the assumed state of stress.
The creep material parameters for 1CrMoV at 565°C are shown to be different for stresses above and below 200 MPa. In selecting the appropriate material parameters for estimating C[t] the reference stress technique is used. At high stresses the greatest estimate of C[t] is obtained from Webster's method, the lowest obtained from Ainsworth's approach and an intermediate estimate obtained using methods proposed by Riedel. At low stresses, where stress redistribution from an initial elastic condition dominates, it has shown that Ainsworth's method is the largest estimate.
For industrial components, containing small cracks and subjected to predominantly tension loading, simple estimates of C[t] can be obtained from the results given in this paper.
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