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Abstract: This paper conducts thermal shock case studies for three typical thermal shock specimens that are important in thermal shock tests: a ceramic layer under a hot shock, a ceramic layer under a cold shock and a ceramic coating under a cold shock. All material properties are assumed to be functions of temperature. The temperature field without cracking is obtained by using the finite element/finite difference method. Time-varied thermal stress intensity factors are obtained by using the weight function method for various parameters of the problem. The thermal shock resistance curves are obtained and the critical size parameters, which control the applicability of the stress-based criterion and the fracture-mechanics-based criterion for the determination of the thermal shock resistance of ceramics, are explored. The studies demonstrate the significance of incorporating temperature-dependent material properties on the thermal shock resistance of ceramic materials for high-temperature applications. The dominant property change responsible for the improvement is the significant reduction in Young’s modulus with increasing temperature. As a result, the thermal stress level is reduced considerably and the thermal shock resistance of the ceramic material is improved greatly. [ABSTRACT FROM AUTHOR]

Abstract: The paper establishes a methodology for the study of thermal shock resistance behavior of ceramic coating/metal substrate systems, based on multiple cracking analysis. The stress criterion and the toughness criterion are used to predict the failure behavior of the system. Multi-scale analysis of the thermal shock resistance of the system is made and variations of the thermal shock resistance of the system with crack density are displayed for different values of coating to substrate thickness ratio. Some critical size parameters, which control the applicability of the stress-based criterion and the fracture mechanics-based criterion for the determination of the thermal shock resistance of the coating/substrate systems, are explored. [Copyright &y& Elsevier]

Abstract: Most magnetoelectroelastic composites were developed in the form of a composite laminate by alternating the ferromagnetic layers and ferroelectric layers during stacking. Presence of interfacial crack may influence the magneto-electro-mechanical coupling behavior of magnetoelectroelastic materials considerably. This paper describes a method to analyze the transient response of a layered magnetoelectroelastic medium of finite size with an interface crack. Based on Fourier and Laplace transforms, the boundary value problem is reduced to a system of generalized singularity integral equations in the Laplace transform domain. By utilized numerical Laplace inversion, the time-dependent full field solutions are obtained in the time domain. Effects of medium size, crack-face electric and magnetic boundary conditions on the dynamic crack tip fields are studied. By investigating an interface notch of finite gap thickness, the electric and magnetic properties of the medium inside the notch are included in the analytical model so that the applicability of crack-face electric and magnetic boundary conditions on the transient response of the magnetoelectroelastic medium can be investigated. [Copyright &y& Elsevier]

Abstract: This paper investigates the fracture problem of a piezoelectric cylinder with a periodic array of embedded circular cracks. An electro-mechanical fracture mechanics model is established first. The model is further used to the thermal fracture analysis of a piezoelectric cylinder subjected to a sudden heating on its outer surface. The temperature field and the associated thermal stresses and electric displacements are obtained and are added to the crack surface to form a mixed-mode boundary value problem for the electro-mechanical coupling fracture. The stress and stress intensities are investigated for the effect of crack spacing. Strength evaluation of piezoelectric materials under the transient thermal environment is made and thermal shock resistance of the medium is given. [Copyright &y& Elsevier]

Abstract: Multiple cracking is a common phenomenon for a medium subjected to a sudden temperature change. In this paper, a multiple surface cracking analysis is carried out to investigate the thermal shock resistance behavior of functionally graded materials (FGMs). The FGM is taken to be a ceramic/metal composite with its gradation characterized by the local volume fractions of metal and ceramic phases. The finite element method is used to obtain the solution of the crack problem. The crack tip field intensity factors as well as the stress are computed as functions of the crack spacing, the normalized time, and the crack depth. Crack initiation behavior is discussed. It is found that the thermal shock resistance of the FGM is significantly enhanced by multiple cracking. That is, the thermal shock resistance is a monotonically increasing function of the crack density (crack density is the number of cracks per unit length; crack density increases with decreasing crack spacing). A single crack represents the lower bound solution for the thermal shock resistance of FGMs. It is also found that the gradation of the FGM has little influence on the crack tip thermal stress intensity factors but has a strong influence on the thermal shock resistance. Multiscale behavior of the thermal shock resistance of FGMs is discussed. Two critical size parameters, which control the applicability of the stress-based criterion and the fracture mechanics-based criterion to the determination of the thermal shock resistance of FGMs, are explored. [Copyright &y& Elsevier]

Abstract: The electro-elastic problem for a periodic array of cracks in a piezoelectric medium subjected to coupled electro-mechanical loads is investigated. The mixed boundary value problem, which is formulated directly in terms of the crack surface displacements and electrical potentials, results in a system of hyper-singular integral equations in which the unknown functions are the crack surface displacement and electric potential. Numerical results include the crack surface displacement and the stress and electric intensity factors for the entire range of possible periodic crack spacing and medium size. The central contribution of this paper is the development of an analytical model that predicts crack-spacing effect. The resulting model is validated by a 2D finite element analysis. [Copyright &y& Elsevier]

Abstract: This paper considers the magneto-electro-mechanical coupling between an inclusion and matrix, which are both of magnetoelectroelastic materials. The general cases including the mode I, mode II and mode III are studied. Analytical solutions for an elliptical cylinder inclusion inside an infinite magnetoelectroelastic medium under combined mechanical–electrical–magnetic loadings are formulated via the Stroh formalism. Crack problem is also investigated and the stress, electric and magnetic fields in the vicinity of the crack tip are determined by a complex vector of intensity factors. Various special cases, including an impermeable inclusion, a permeable crack, a rigid and permeable inclusion, a rigid and permeable line inclusion, a permeable cavity, and an impermeable cavity are discussed. [Copyright &y& Elsevier]