Papers by Keyword: Interface Element

Abstract: The paper presents a mathematical model of a finite element for modeling imperfect interface conditions for two contacting surfaces. The element is used in the numerical implementation of the Asymptotic Averaging Method (AAM) for the determination of effective elastic properties of composite materials under investigation. Numerical experiments are carried out to calculate the elastic properties taking into account the adhesion layer using a displacements field jump condition at the phase boundary. Results are compared with adhesion modeling using an additional bulk phase.

Abstract: In this paper, a viscoelastic-damage cohesive zone model is formulated and discussed. The interface element constitutive law has two elastic and damage regimes. Viscoelastic behaviour has been assumed for the shear stress in the elastic regime. Three element Voigt model has been used for the formulation of relaxation modulus of the material. Shear Stress has been evaluated in the elastic regime of the interface with integration over the history of the applied strain at the interface. Damage evolution proceeds according to the bilinear cohesive constitutive law up to the complete decohesion. Numerical examples for one element model has been presented to see the effect of parameters on cohesive constitutive law.

Abstract: As examples of the most typical methods to determine the shear strength of SiC/SiC composite joints, the asymmetrical four point bending test of a butt-joined composite, the tensile test of a lap-joined composite, and the compression test of a double-notched composite joint were analyzed by using a finite element method with the interface element. From the results, it was found that the shear strength in the asymmetrical bending test was controlled by both the surface energy and the shear strength at the interface regardless of their combination while the strength in the tensile test or the compression test was governed by the surface energy when both the surface energy and the shear strength were large. In addition, the interface element was employed in order to examine the influence of the specimen geometry on the microstructural fracture morphology in nanoSiC/SiC composite during a miniaturized Double Notch Shear (DNS) test. From the serial computations, it is revealed that a relationship between the inter-laminar shear strength and the yield stress seems to be very important for selecting appropriate specimen geometry of the miniaturized DNS test.

Abstract: The paper adopts the interface element to simulate the joints so as to systematically and quantitatively study the deformation around tunnel, the mechanic state of lining and the stability under different inclining angles of joints. The result shows that the deformation around tunnel deteriorates mainly along the joint during the inner convergence effects of surrounding rock. When the inclining angle α=45°, the deformation around the tunnel is most serious, followed by that when α=90°, α=60°, α=30° and α=0°. At the same time, the influence of inclining angle on the distribution of the axial force of lining is comparatively small. But the distribution of bending moment and shear change obviously where the joints penetrate the tunnel. The tunnel stability of surrounding rock is the poorest when α=90° and the tunnel is most stable when α=0°. The stability of surrounding rock changes little when α is between 30° and 60°. The research result provides an effective calculation method for the forecast of deformation, the design of structure and the stability analysis of jointed tunnel. It is also helpful for the monitoring of construction and calculation of jointed tunnel in the future.

Abstract: A new interface element method was proposed to calculate the strain energy release rates(SERR) based on the virtual crack closure technique (VCCT). A Lagrange multiplier was introduced between the node pair at crack tip to obtain the internal forces. Then from the VCCT, the SERR was solved by using the forces and displacements near the crack tip. Examples for stationary cracks under the two typical cases are given. Meanwhile, the relationship curves between crack energy release rate and the length of crack, plate depths were plotted respectively.The example shows that the interface element used to calculate the SERR is simple, efficient, and highly accurate in analysis of 2D crack growth problems, and without requiring the special singularity element or collapsed element at crack tip.

Abstract: As a numerical tool for examining the microstructural fracture behavior in the smart and intelligent materials, a finite element method with the interface element was developed and the applicability of this method was studied through the serial computations using virtual polycrystalline models. As the results assuming the influence of grain orientation on the grain boundary, it was found that the anisotropic mechanical property of grain boundary (interaction between opening and slipping deformations) would be a dominant factor of the fracture process. Also, by employing the theory of crystal plasticity for the mechanical property of grain, it was revealed that the stress concentrations caused by both the mismatch between neighbor grains and the slipping at grain boundary could be demonstrated by using this method.

Abstract: The ability of mortarless wall to restrain/sustain lateral load become important aspect to be consider in the design of wall. Therefore, this paper presents analyses of mortarless wall subjected to in-plane combined loading using finite element programs. The developed 2D finite element program is used in this research. The finite element models are developed based on micro modelling approach where each constituent of masonry (block and dry joint) connected each other by joints at their actual position. Eight nodded isoparametric plane element and six nodded zero thickness isoparametric interface element are used to represent block unit and dry joint respectively. The developed models are analysed under nonlinear environment. The most relevant results concern the strength response of the dry joint masonry walls subjected to in-plane combined compressive and shear loading. The results of finite element analysis compared with corresponding experimental results and its show good agreement. Parametric study also performed to consider the important parameters that effect the design of wall under combined loading. Significant features of the structural behaviour, ultimate capacity and observed failure mechanisms are addressed and discussed.

Abstract: In spite of a vast background on cohesive constitutive law and its use for various analyses such as delamination in composite laminates, some numerical aspects of that have been less explored and reported in the literature. The aim of this paper is to study the phenomenon of spurious stress oscillation and also dominant process zone (where damage has its most significant evolution) in delamination modeling. For this purpose, distribution of normal stress and damage parameter of different DCB specimen are analyzed. Distribution of stress around the process zone indicates spurious oscillation just ahead of the delamination tip where damage parameter is zero and no effect of this phenomenon is seen on results of applied load versus opening displacement. Additionally, it is shown that larger values of penalty stiffness lead in smaller length of dominant process zone and very large values of penalty stiffness pushes the distribution of damage parameter to become step-like function. Authors believe that this effect is in fact the main reason of un-converged solution of models with too large penalty values.

Abstract: The present study involves an experimental and analytical investigation of the Mode II delamination propagation and the fibre bridging effects incorporated in the Fracture Process Zone (FPZ). End Notch Flexure (ENF) specimens from a unidirectional glass/epoxy composite material have been fabricated and tested. In order to construct the fracture resistance curve (R-curve) of the ENF tests, three different data reduction schemes have been utilized. The fibre bridging effects in the FPZ have been addressed with the use of traction-separation laws, as extracted from the corresponding calculated R-curves. These laws can be used to describe the constitutive relationship in interface finite elements, for the numerical modelling of delamination growth in laminated composite structures.

Abstract: The present work involves a numerical modelling of the Embedded Process Zone (EPZ) by utilizing the elastoplastic Mode I and Mode II fracture models for the simulation of plastically deforming adhesive joints. A traction-separation law was developed separately for Mode I and Mode II. For the analysis of the mixed-mode fracture processes, the cohesive zones in Mode I and Mode II fracture were assumed uncoupled. The experimental programme involved the fabrication and testing of Double Strap Joints (DSJs) and Single Lap Joints (SLJs). By fitting the numerical results to the experimental ones, the basic cohesive parameters of the problem were defined.