Papers by Keyword: Interface Crack

Abstract: A laminated beam containing an initial delamination subjected to thermal gradient is analyzed on the basis of classical beam theory. The axial forces are induced in the parts of the constituent beams above and below the delamination. For the case where crack faces are open, a nonlinear equation for determining the in-plane forces is derived by modeling the delaminated part as two lapped beams hinged at both ends, and by imposing the compatibility condition of the deformations of the two beams. Numerical solutions are obtained for some model beams. It is shown that the relative displacement at the center of the delamination increases gradually with the increase very rapidly, i.e., local delamination buckling occurs. Energy release rate is small for temperature gradient below the critical value, but it takes a large value when the temperature gradient is increased beyond the critical value.

Abstract: The problem of crack path stability along the interface between two orthotropic elastically dissimilar materials under the presence of in-plane residual stresses is analyzed using the concept of Finite Fracture Mechanics and matched asymptotic procedure. An energy based fracture criterion is introduced for this problem and it is investigated whether and how is the criterion for the prediction of crack kinking from the interface affected by residual stresses. The complex stress intensity factor and the T-stress characterizing the stress state at the crack tip are calculated both for the thermal (residual stresses) and mechanical loading using the two-state integral. The matched asymptotic procedure together with FEM is used to derive the change of the potential energy induced by the crack growth by crack increment of finite length.

Abstract: Mathematical modeling of thermal fracture of functionally graded/homogeneous bimaterial structures with a system of arbitrarily located cracks is performed and based on the previously suggested theoretical approach [1-which used the integral equation method. It is supposed that the structure is subjected to thermal loading (a thermal flux) and mechanical loading (a tension). The properties of the functionally graded material (FGM) are described by a continuous exponential function. The main fracture characteristics (stress intensity factors and fracture angles) are presented as functions of the geometry of the problem and special inhomogeneity parameters of FGMs. Some typical crack patterns for FGM/homogeneous bimaterial structures resulting from experiments available in literature are studied in detail. Thermal fracture of actual material combinations of FGMs such as: ceramic/ceramic, e.g., TiC/SiC, MoSi₂/Al₂O₃ and MoSi₂/SiC, and also ceramic/metal FGMs, e.g., zirconia/nickel and zirconia/steel, is investigated.

Abstract: In the paper, the crack parallel to and lying on the interface in the hard cladding material structure is regarded as the research object, theoretical model of the stress intensity factor (SIF) of the interface crack under the mechanical impact load is built. Based on it, the SIF of the crack parallel to and lying on the interface in the cermet cladding material structure under the mechanical impact load is investigated by using finite element analysis method. The influences of the cladding thickness ratio and mechanical impact stress amplitude on the interface SIF are investigated. The research results show that, at a certain moment, the interface SIFs decrease with increasing cladding thickness ratio when the mechanical impact stress amplitude is a constant and increase as the mechanical impact stress amplitude increases when the cladding thickness ratio is a constant.

Abstract: This paper presents a new numerical method for obtaining the complex stress intensity factor with an interface crack in bi-materials using photoelastic isochromatic fringe numbers N. The theoretical solution of stress field at the crack tip was deduced from Muskhelishvilis stress function and an undetermined term σ₀ which is a function of material properties was added to this theoretical solution. A partial differential iterative equation with fast convergence was formed by applying the photoelastic theory. The complex stress intensity factor K=K₁+iK₂ and σ₀ were obtained by Newton-Raphson iteration method and K domain was discussed. The simulant photoelastic isochromatic fringe pattern could be generated through image processing and numerical calculation according to K and σ₀. The simulant isochromatic fringe pattern accords with experimental photoelastic isochromatic fringe pattern, so it is practicable for this numerical method of obtaining the complex stress intensity factor.

Abstract: The problem of crack deflection from the interface between two orthotropic materials is analyzed using the concept of Finite fracture mechanics and matched asymptotic procedure. A fracture criterion based on the energy approach is introduced for this problem. The main input for such criterion is the complex stress intensity factor calculated e.g. using the two-state integral. However for more precise predictions of the crack propagation also higher order terms of the asymptotic expansion are advisable to involve in the fracture criterion. To this end a T-stress term will be calculated and considered as the second input parameter. The matched asymptotic procedure together with FEM is used to derive the change of the potential energy induced by the incremental crack growth.

Abstract: The bimaterial disc specimen with central interface crack under diametric compression loading was simulated using the finite element method (FEM). The mode mixity for the interface crack was controlled by varying the compression angle. The consistent mode mixity independent of the assumed crack-extension size was obtained using the virtual crack closure technique (VCCT) by introducing an arbitrary normalizing length l_G. The relations of the compression angle and the oscillation index ε to the consistent mode mixity were discussed with the simulation results. It found that the critical compression angles corresponding to pure mode ΙΙ got closed to 25⁰ as the absolute value of ε was very small and a fitted formula of the critical compression angle and the absolute value of ε was also obtained.

Abstract: An interface crack problem in two nonhomogeneous plates under thermal loading is investigated. The interaction energy integral method (IEIM) is developed for obtaining the mixed-mode thermal stress intensity factors (TSIFs) of interface crack. The domain-independence of the present IEIM is verified. Numerical examples are presented and the results show good agreement with the analytic ones. Numerical results show that the method is very effective for the thermal interface crack of nonhomogeneous plate.

Abstract: This paper studies the thermal flow concentration near an interface crack in a layered medium. Solution method for the thermal flow intensity factor is established. Both the Griffith crack and the penny-shaped crack are studied. Limiting cases of the current problem include (1) the solution of crack problem associated with classical Fourier heat conduction, (2) the solution of an interface crack in an infinite layered medium, and (3) the solution of a crack in a homogeneous medium.

Abstract: Maximum normal stress criterion can be used to determine the cracking angle in the uniform and non-uniform zone. According to this theory, the propagating process of the crack in non-uniform composite material is simulated based on the finite element method. The results show that the crack advances wave-like and basically along the direction perpendicular to the maximum normal stress, which is of great guiding significance for the fracture resistance of such kind of structure.