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In the CCG life assessment for defective structures based on the two-parameter method with considering constraints, the establishment of a correlation equation between the constraint parameter and the CCG rate for a material at a temperature is very important, but it is difficult and costly. For engineering applications, it is desirable to have a unified correlation equation for different materials. In this work, based on a large amount of experimental CCG rate data of different specimens from the literature, combining with the finite element (FE) calculations of a new unified creep constraint parameter Ac ,, a unified correlation equation has been obtained. In the CCG life evaluation for cracked structures based on the C*-Ac two-parameter method, this correlation equation may be used to estimate the constraint-dependent CCG rates for any materials at different temperatures. The correlation equations of eleven materials are also summarised in this paper. [ABSTRACT FROM AUTHOR]

In order to predict and assess creep life for plate structures with semi‐elliptic surface cracks under high temperature condition, the accurate calculation of the creep fracture mechanics parameter C* is a critical step. In this paper, the effects of crack sizes, plate geometries, and material creep properties on the parameter C* have been investigated under tensile and bending loads by extensive finite element analyses. Based on the results, the creep influence functions Hc for calculating C* values were obtained and fitted into equations for surface cracks in plates under both loads. The equations have been verified by finite element calculations. The C* solutions were obtained through these equations which are suitable for wide ranges of crack sizes, plate geometries, and materials. [ABSTRACT FROM AUTHOR]

In this paper, the equivalent creep strain distributions ahead of crack tips in SEN(B), SEN(T) and M(T) specimens with different in-plane and out-of-plane constraints were calculated by extensive finite element analyses, and the creep crack growth (CCG) rates of these specimens were simulated over a wide range of C* by using stress dependent creep ductility and strain rate model in a ductility exhaustion based damage model. The capability and applicability of the constraint parameter A c based on crack-tip equivalent creep strain for characterizing both in-plane and out-of-plane creep crack-tip constraints and establishing a unified correlation with CCG rate of a steel were investigated. The results show that with increasing constraints, the CCG rate increases, and the effect of out-of-plane constraint on CCG rate is more obvious than that of in-plane constraint. The CCG rate of high constraint specimen geometry (such as SEN(B)) is more sensitive to the out-of-plane and in-plane constraints than that of low constraint specimen geometry (such as M(T)). The parameter A c is a unified characterization parameter of in-plane and out-of-plane creep constraints for the different specimen geometries. Base on the parameter A c , the unified correlation formulas of in-plane and out-of-plane constraints with CCG rate of the steel have been obtained, and they are independent on the choices of the standard specimen. The unified correlation formulas may be used in constraint-dependent CCG life assessments of high-temperature components (such as pressure vessels and pipes) with any in-plane and out-of-plane constraint levels. [ABSTRACT FROM AUTHOR]