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In this work, the correlation between ductile fracture toughness and a new unified constraint parameter Ad* for bi‐material interfaces with different mechanical mismatches (strength and hardening mismatches) has been investigated based on finite element analysis and experimental data validation. The results show that with increasing crack depth (geometric constraint) and mechanical mismatch level (increasing undermatch or overmatch level), the J–R curves and fracture toughness JC of bi‐material interfaces decrease. The constraint parameter Ad* values of bi‐material interface cracks are basically independent of the strength and hardening mismatches. A general correlation equation between fracture toughness JC and constraint parameter Ad* has been obtained, which may be applied to prediction of fracture toughness of any specimens or components with different geometric constraints and material properties mismatches (including homogeneous materials). The prediction capability of the correlation equation has been validated by experimental fracture toughness data of cracks with different strength and hardening mismatches in dissimilar metal welded joints. Highlights: Correlation between fracture toughness and constraint of bi‐material interfaces is studied.The constraint parameter Ad* of bi‐material interface is independent of the mismatches.A general correlation equation between fracture toughness and parameter Ad* is obtained.Prediction capability of the equation for fracture toughness is validated by experimental data. [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]

Extensive finite element analyses of cracked pipes with different crack sizes and orientations have been conducted to investigate effects of creep properties of materials on the unified creep constraint parameter Ac. The results show that the constraint parameter Ac is independent on Norton's coefficient A, and it is only affected by the creep exponent n of materials. For a given crack size, with increasing n, Ac decreases and constraint level increases. The Ac of lower constraint cracks is more sensitive to n. The unified correlation equations between Ac and n have been obtained for cracked pipes with a wide range of crack sizes and constraint levels. They may be used to estimate the constraint parameter Ac at different positions along the crack fronts in cracked pipes made of materials with different n values. The two-parameter C*-Ac approach for assessing creep life of cracked pipes has also been discussed. [ABSTRACT FROM AUTHOR]

We embed the fractional Allen-Cahn equation into a Galerkin variational framework and thus develop its corresponding finite element procedure and then prove rigorously its mathematical and physical properties for the finite element solution. Combining the merits of the conjugate gradient (CG) algorithm and the Toeplitz structure of the coefficient matrix, we design a fast CG for the linearized finite element scheme to reduce the computation cost and the storage to O(M log⁡ M ) and O(M), respectively. Numerical experiments confirm that the proposed fast CG algorithm recognizes accurately the mass and energy dissipation, the phase separation through a very clear coarse graining process, and the influences of different indices r of fractional Laplacian and different coefficients K,η on the width of the interfaces. [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]

Abstract: The 3D growth behaviour of pits initiated at MnS inclusions for A537 steel under cyclic load condition has been investigated by confocal scanning laser microscope and finite element analysis. The results indicated the growth of pit for cyclic-stressed samples showed anisotropic behaviour. Significant higher growth rate was found in the direction perpendicular to load axis. Finite element analysis indicated that localized plastic strain played an important role on pit growth. The growth kinetics of pit in width direction is dominated by plastic deformation. Coalescences of pits further increase the growth rate of pit as predicted by finite element analysis. [Copyright &y& Elsevier]