Papers by Author: Yao Dai

Abstract: The anti-plane crack problem is studied in functionally graded piezoelectric materials (FGPMs). The material properties of the FGPMs are assumed to be the exponential function of y. The crack is electrically impermeable and loaded by anti-plane shear tractions and in-plane electric displacements. Similar to the Williams solution of homogeneous material, the high order asymptotic fields are obtained by the method of asymptotic expansion. This investigation possesses fundamental significance as Williams solution.

Abstract: The theory for plate and shell with Reissners effect is adopted to analyze the circumferential crack problem for FGMs cylindrical shell by using the asymptotic expansion method. The eigen-solution of the crack tip field for circumferential power type FGMs cylindrical shell which is similar to Williams solution is given.

Abstract: Reissner’s plate bending fracture theory with consideration of transverse shear deformation effects is adopted for the crack problem of power-law functionally graded materials (FGMs) plates. Assume that the crack is parallel to the material property gradient. By applying the asymptotic expansion method, the crack-tip higher order asymptotic fields which are similar to Williams’ solutions of homogeneous materials are obtained.

Abstract: The Reissner’s plate bending theory with consideration of transverse shear deformation effects is adopted to study the fundamental fracture problem in functionally graded materials (FGMs) plates for a crack perpendicular to material gradient. The crack-tip higher order asymptotic fields of FGMs plates are obtained by the asymptotic expansion method. This study has fundamental significance as Williams’ solution.

Abstract: An arbitrarily oriented anti-plane crack with its tip at the physical weak-discontinuous line of the structure which is made up of homogeneous material and functionally graded materials (FGMs) is studied. The analytic solution of the higher order crack tip fields (similar to the Williams’ solution of homogenous material) is obtained by applying the asymptotic series expansion. When non-homogeneous material parameters are degenerated, the solutions become the same as the asymptotic crack tip fields of the homogeneous material. Therefore, the solutions are the basic results of non-homogeneous fracture mechanics, and provide a theoretical basis for solving the fracture problems of one common structure with physical weak-discontinuity.

Abstract: The higher order discontinuous asymptotic fields which are similar to the Williams’ solutions of homogenous material are obtained by the displacement method and asymptotic analysis for a plane crack at the physical weak-discontinuous interface in non-homogeneous materials. The results provide a theoretical basis for the numerical analysis, experimental investigation and the engineering application of physical weak-discontinuous fracture.

Abstract: For homogeneous material plates and non-homogeneous material plates, the crack-tip field plays an important role in the research of fracture mechanics. However, the governing equations become the system of the sixth order partial differential ones with the variable coefficients when the material gradient is perpendicular to the thickness direction of plates. In this paper, they are derived first. Then, the crack-tip fields of the plates of radial functionally graded materials (FGMs) are studied and the higher order crack-tip fields are obtained based on the Reissner’s plate theory. The results show the effect of the non-homogeneity on the crack-tip fields explicitly and become the same as solutions of the homogeneous material plates as the non-homogeneous parameter approaches zero.

Abstract: The exponential and power material functions are often applied to functionally gradient materials (FGM). Obviously, it is of fundamental significance to study FGM with arbitrary material function. Because an arbitrary function can be treated as finite linear segments approximately, it is essential to research FGM with a linear material function. Crack-tip higher order stress and displacement fields for an anti-plane crack perpendicular to the direction of property variation in a FGM with a linear shear modulus along the gradient direction are obtained through the asymptotic analysis. The asymptotic expansions of crack tip stress fields bring out explicitly the influence of non-homogeneity on the structure of the stress field. The analysis reveals that only the higher order terms in the expansion are influenced by the material non-homogeneity. Moreover, it can be seen from expressions of higher order stress fields that at least three terms must be considered in the case of FGM in order to explicitly and theoretically account for non-homogeneity effects on crack tip stress fields.

Abstract: The high order discontinuous asymptotic fields similar to the Williams’ solutions to crack problems in homogeneous materials are obtained by asymptotic analysis for an anti-plane problem in non-homogeneous materials and the crack at the physical weak-discontinuous interface. These results provide a theoretical basis for engineering application of weak-discontinuity fracture.

Abstract: Analytical expressions for crack-tip higher order stress functions for a plane crack in a special functionally graded material (FGM), which has an variation of elastic modulus in 1 2 power form along the gradient direction, are obtained through an asymptotic analysis. The Poisson’s ratio of the FGM is assumed to be constant in the analysis. The higher order fields in the asymptotic expansion display the influence of non-homogeneity on the structure of crack-tip fields obviously. Furthermore, it can be seen from expressions of higher order stress fields that at least three terms must be considered in the case of FGMs in order to explicitly account for non-homogeneity effects on the crack- tip stress fields. These results provide the basis for fracture analysis and engineering applications of this FGM.