Papers by Keyword: Interfacial Crack

Abstract: This paper investigated the performance of single-lap joints with interfacial crack through the finite element method. The finite element method was validated by the G-R solutions at first. And then the influence of geometric parameter of the joint as well as the length of the interfacial crack were discussed. Results showed that the presence of a spew fillet can reduced the stress intensity factors (SIF).The relationship of the crack length ratio and SIF, adhesive thickness ratio and SIF were built.

Abstract: A theoretical analysis is followed to calculate the dynamic stress intensity factors (DSIFs) in transversely isotropic piezoelectric bi-materials, due to existence of a permeable interfacial crack, near the edge of a circular cavity. The model is subjected to dynamic incident anti-plane shearing (SH-wave) and the formulation based on Green's function method. Conjunction and crack-simulation techniques are applied to obtain DSIFs at the crack’s outer tip. Calculations are prepared based on FORTRAN language program. A comparison is accomplished between the present model and another model with a crack emerging from the cavity edge to calibrate the program. Calculating results showed the influences of the physical parameters, the structural geometry and the wave frequencies on the dimensionless DSIFs and how those affected the efficiency of piezoelectric devices and materials.

Abstract: In transversely isotropic piezoelectric bi-materials, a theoretical analysis is followed to calculate the dynamic stress intensity factors (DSIFs) due to existence of a permeable interfacial crack, near the edge of a circular cavity. The model is subjected to dynamic incident anti-plane shearing (SH-wave) and Green's function method is the base of formulation. Conjunction and crack-simulation techniques are applied to obtain DSIFs at the crack’s inner tip. Calculations are prepared based on FORTRAN language program. For calibration of program, a comparison is accomplished between the present model and another with a crack emerging from the cavity edge. Calculating results clarified the influences of the physical parameters, the structural geometry and the wave frequencies on the dimensionless DSIFs and how those affected the efficiency of piezoelectric devices and materials.

Abstract: The higher order crack-tip fields for an anti-plane crack situated in the interface between functionally graded piezoelectric materials (FGPMs) and homogeneous piezoelectric materials (HPMs) are presented. The mechanical and electrical properties of the FGPMs are assumed to be linear functions of y perpendicular to the crack. The crack surfaces are supposed to be insulated electrically. By using the method of eigen-expansion, the higher order stress and electric displacement crack tip fields for FGPMs and HPMs are obtained. The analytic expressions of the stress intensity factors and the electric displacement intensity factors are derived.

Abstract: The problem of an anti-plane crack situated in the interface of functionally graded piezoelectric materials (FGPMs) and homogeneous piezoelectric materials (HPMs) is considered under the impermeable assumption of crack surfaces. The mechanical and electrical properties of the FGPMs are assumed to be exponential functions of y perpendicular to the crack. The higher order crack tip stress and electric displacement fields for FGPMs and HPMs are obtained by the eigen-expansion method. The stress intensity factor and electric displacement intensity factor are obtained explicitly.

Abstract: A coupled method between the Scaled Boundary Finite Element Method (SBFEM) and Finite Element Method (FEM) for evaluating the Stress Intensity Factors (SIFs) is presented and achieved on the platform of the commercial finite element software ABAQUS by using Python as the programming language. Automatic transformation of the finite elements around a singular point to a scaled boundary finite element subdomain is realized. This method combines the high accuracy of the SBFEM in computing the SIFs with the ability to handle material nonlinearity as well as powerful mesh generation and post processing ability of commercial FEM software. The validity and accuracy of the method is verified by analysis of several benchmark problems. The coupled algorithm shows a good converging performance, and with minimum additional treatment can be able to handle more problems that cannot be solved by either SBFEM or FEM itself. For fracture problems, it proposes an efficient way to represent stress singularity for problems with complex geometry, loading condition or certain nonlinearity.

Abstract: In this study, the effects of interfacial crack on thermal mechanical behavior of solder bump only induced by current for flip-chip package are investigated by numerical analysis. In the numerical model, the properties of solder bump are dependent on temperature. First, the crack length effects on thermal mechanical behavior of solder bump is examined, with the parameters of temperature, von Mises stress, shear stress and plastic strain. Second, the influence of current density is also numerically examined. It is demonstrated that the increasing current density and the crack length will induce more plastic strain in the solder bump. This study may be helpful for the fabricated technique of the die-solder bump-substrate system.

Abstract: The physical weak-discontinuous problem of an interfacial crack between homogeneous material and functionally graded materials (FGMs) is studied based on Reissner’s plates considering transverse shear deformation effect. The crack-tip higher order asymptotic fields of homogeneous materials and FGMs regions are obtained by the asymptotic expansion method, respectively. Finally, the whole crack tip high order fields are assembled and given. The results provide a theoretical basis for solving interfacial crack problems of FGMs plates and their engineering application.

Abstract: Considering the concrete as a three-phase composite material composed of aggregate, interface and cement matrix, an octagon unit cell is constructed based on ellipse, and the numerical solution of concrete chloride diffusion coefficient considering the aggregate shape is obtained using the finite element method. The validity of the proposed algorithm is preliminary verified after compared with the available test results, and the effect of interfacial crack opening angle and aggregate shape on the concrete chloride diffusion coefficient is quantitatively evaluated. Through numerical calculation, it is found that the chloride diffusion coefficient of concrete increases with the increase of interfacial crack opening angle and decreases with the increase of aggregate shape coefficient.

Abstract: An explicit extrapolating formula for a general case of the interfacial crack plane lying with an angle to the poling axis in transversely isotropic piezoelectric (TIP) materials is derived, which is very feasible to determine the intensity factors for numerical methods such as FEM or BEM. Additionally, a more concise extrapolating formula for the typical state of the interfacial crack plane lying perpendicular to the poling axis is also presented in this paper.