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Abstract: This paper theoretically proposed a series of formulae for a novel tensile testing method to extract the residual stress in the surface film on metallic substrates. Finite element calculations were conducted to verify the accuracy and reliability of the proposed formulae. From the tensile stress–strain curves of metallic substrates with and without a surface film, one can evaluate the residual stress in the film using these formulae. A tarnish film on a brass substrate formed after immersion in Mattsson’s solution was tested to demonstrate these methods, and the obtained residual stress showed a low difference below 6.8%. [Copyright &y& Elsevier]

Abstract: It is well known that residual stresses influence the ductile fracture behaviour. In this paper, a numerical study was performed to assess the effect of residual stresses on ductile crack growth resistance of a typical pipeline steel. A modified boundary layer model was employed for the analysis under plane strain, Mode I loading condition. The residual stress fields were introduced into the finite element model by the eigenstrain method. A sharp crack was embedded in the center of the weld region. The complete Gurson model has been applied to simulate the ductile fracture by microvoid nucleation, growth and coalescence. Results show that tensile residual stresses can significantly reduce the crack growth resistance when the crack growth is small compared with the length scale of the tensile residual stress field. With the crack growth, the effect of residual stresses on the crack growth resistance tends to diminish. The effect of residual stress on ductile crack growth resistance seems independent of the size of geometrically similar welds. When normalized by the weld zone size, the ductile crack growth resistance collapses into one curve, which can be used to assess the structural integrity and evaluate the effect of residual stresses. It has also been found that the effect of residual stresses on crack growth resistance depends on the initial void volume fraction f 0, hardening exponent n and T-stress. [Copyright &y& Elsevier]

Abstract: Residual stresses play a crucial role in structural integrity assessment. In this study, a large cracked cylinder with a weld in the center is applied to investigate the effect of residual stresses on the crack-tip constraint. A modified boundary layer model with a remote displacement-controlled elastic K-field and T-stress under small scale yielding has been used to simulate the problem. A two-dimensional tensile residual stress field due to the weld is introduced into the model by the so-called eigenstrain method. It has been shown that the residual stresses can significantly elevate the crack-tip constraint and thus increase the probability for cleavage fracture. The constraint parameter R introduced by the authors can be used to rank the crack-tip constraint induced by the bi-axial residual stresses. The R value decreases with the increase in the applied J-integral. The residual stress-induced constraint is also coupled with the T-stress. The R value becomes smaller with larger T-stress. [Copyright &y& Elsevier]

Abstract: This paper studies the effect of welding residual stresses on the near tip stress field in single edge notched bending and tensile specimens. A combined effect of mechanical stresses by the applied load and residual stress on the crack tip constraint is analyzed. Three initial residual stress distributions were considered. It has been shown that the crack tip stress field is strongly influenced by the residual stresses and a new parameter, R, is proposed to characterize the residual stress induced crack tip constraint. The results therefore suggest a three-parameter approach (CTOD, Q and R) to characterize the crack tip stress field in the presence of residual stress where CTOD sets the size scale over which large stresses and large strains develop, and the geometry constraint parameter Q and the new residual stress induced constraint parameter R control the actual crack tip constraint level. For the cases analyzed, R is in general positive, which indicates that residual stress can enhance the crack tip constraint. However, the results also indicate that the R decreases towards zero and the effect of residual stress on crack tip constraint can be neglected when a full plastic condition is approached in the specimen. [Copyright &y& Elsevier]

Abstract: This paper addresses the residual stresses and their effect on microcracking in polycrystalline ceramic materials. Residual stresses at microstructural level in titanium diboride ceramics, as a result of thermal expansion anisotropy, were analyzed by finite element method using Clarke’s model. Damage mechanics based cohesive zone model was applied to study grain boundary microcracking, propagation and arrest. Quantitative relations between temperature variation, grain boundary energy, grain size, final microcrack length as well as microcracking temperature are established. [Copyright &y& Elsevier]

Abstract: Materials constitutive behaviour at high temperature is dependent on both temperature and microstructure. This paper presents a method to retrieve the temperature and microstructure dependent apparent yield strength of 6XXX aluminium alloys from the reaction force–temperature curves measured at the centre of the gauge length of a cylindrical specimen. The specimen is clamped at both ends and subjected to a controlled thermal history via induction heating. The experimental procedure is based on the test setup proposed by Satoh to determine residual stresses in welds. Various effects on the accuracy of the method have been investigated, including the effect of heating rate, hardening and testing frame stiffness. Examples have been shown for the aluminium alloy 6082 in T6 temper condition. [Copyright &y& Elsevier]