• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1217-1222
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• 2002

The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamically propagating behavior of the interface crack. This paper investigates the effects of the hole (existed along the path of the crack propagation) shape on the dynamic interface crack propagation behavior by comparing the experimental isochromatic fringes to the theoretical stress fields.

• Applied Microscopy
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• v.36 no.spc1
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• pp.41-46
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• 2006

Interfacial atomic structure (chemical structure) of a Pd/ZnO hetero junction was investigated by atomic resolution high voltage transmission electron microscopy (ARHVTEM). A misfit dislocation did not work as a stress accommodation mechanism in the ZnO(0001)/Pd (111) interface. But the periodic stress localization occurred in the ZnO($10\bar{1}0$)/(200) interface. The periodicity of the local strain coincided with that of misfit dislocation. Atomic structure image of the ARHVTEM showed that an atomic arrangement across the interface was in the order of O-Zn-Pd. It was shown that mechanical weakness of the ZnO(0001)/Pd(111) interface against cyclic heating is attributable to the absence of the periodic stress localization of the misfit dislocation.

• Computational Structural Engineering
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• v.10 no.3
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• pp.185-193
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• 1997

The order of the stress singularity that occurs at the termination of an interface between materials exhibiting bilinear stress-strain response under plane strain conditions has been calculated, The governing equation of elasticity together with traction-free boundary condition and interface continuity condition defines a two-point boundary value problem. The stress components near the free edge are assumed to be proportional to r/sup s-1/, with solutions existing only for certain values of s. Finding these values entails the solution of an eigenvalue problem. Because it has been impossible to integrate the differential equations analytically, the integration has been performed numerically with a shooting method coupled with a Newton improvement scheme.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.143-154
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• 1999

In this study, the load transfer mechanism of tendon-grout interface of rock anchors has been examined through a series of static pull-out tests conducted on the model rock anchors constructed in the natural and artificial rock masses of granite and concrete, respectively. Several rock masses with horizontal discontinuities have been prepared to study the effects of weak planes on the shear stress distribution in tendon-grout interface. As a result, for the rock anchors constructed in the rock mass without discontinuities, stress concentration occurs on the upper part of the tendon-grout interface. On the contrary, as the frequency or the number of discontinuities increases, the shear stress distribution along the depth tends to be uniform. Also, an experimental equation about shear stress distribution between tendon-grout interface can be made by the regression of test results. The shear stresses computed from the experimental results between the rock surface and the depth of 2~3 times the tendon diameter are smaller than those from theory. Below the depth, the reverse can be observed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2087-2096
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• 1996

Recentrly advantages in composite and light weight material techniques have led to the increased use of bonded dissimilar materials such as ceramics/metal bonded joints, IC package, brazing, coating and soldering in the various industries. It is required to analyze the evaluation method of fracture strength and design methodology of bonded joints in dissimilar materials. Stress singularity according to changes of scarf angles for bonded scarf joints in dissimilar materials was investigated by the boundary element method and static experiments. In this paper, effect of the stress singularity factors at the interface edges of scarf joints on various dissmilar materials combinations were investigated by analysis of its stress and stress singularity index using 2-dimensional elastic program of boundary element method. And the variations of stress singularity index by changes for Young's modulus ratios of materials and scarf angles were investigated. Also, it is found that stress singularities at bonded interface edges are disappeared for certain combination of scarf angle in a pair of bonded dissimilar materials. As the results, it is proposed that the strength evaluation by using stress singularity factors, $\Gamma$, considering stress singularity at the interface edges of bonded dissimilar materials, is very useful.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.337-346
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• 1996

Debonding of cement-femoral stem interface has been suggested as a initial focus of loosening mechanism in many previous studies of cemented total hip replacement. The purpose of this study was to investigate the effect of debonding of cement-femoral stem interface to the bone-cement interface by using three-dimensional non-liner finite element analysis. Three cases of partial debonded, full debonded, full bonded cement-bone interface were modelled with partial bonding of distal 70mm from the tip of femoral stem. Each situation was studied under loading stimulating one-leg stanced gait of 68kg patient. The results showed that under partial and full debonded cement-stem interface condition the peak von Mises stress(3.1 MPa) were observed at the cement of bone-cement interface just under the calcar of proximal medial of femur, and sudden high peak stresses(3.5MPa) were developed at the distal tip of femoral stem at the lateral bone-cement interface in all 3 cases of bonding. The stresses were transfered very little to the cement of upper lateral bone-cement interface in partial and full debonded cases. Thus, once partial or full debonded cement-femoral stem interface occured, 3 times higher stress concentration were developed on the cement of proximal medial bone-cement interface than full bonded interface, and these could cause loosening of cemented total hip replacement. Clinically, preservation of more rigid cement-femoral stem interface may be important factor to prevent loosening of femoral stem.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.105-108
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• 2004

In general, the nonlinear behavior of composite structures composing of steel and concrete is analyzed on the basis of the assumption of the perfect bond actions in steel-concrete interface in which the interface slip or separation is not allowed. The assumption is based on the fact that the full interface bond behavior is provided with the mechanical connectors of studs. However, since the number and spacing of the studs are determined by the stress resultants calculated in the interface area, the interface analysis is required to evaluate the stress resultants. This paper describes the nonlinear steel-concrete interface behavior considering the two interface failure mechanisms of slip and separation. Elastoplastic constitutive relation is developed. thru the formulation framework using the two energy dissipation mechanisms. As the result, the steel plate push-out tests sandwitched between concrete blocks are analyzed and compared with the test results with which the good agreements are observed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1500-1508
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• 2004

Stress and displacement fields for a crack propagating along interface between isotropic material and functionally gradient one with linear property gradation along X direction are developed. The stress and displacement fields are obtained from the complex function of steady plane motion for isotropic and functionally gradient material (FGM). The stresses and displacement in isotropic material of bimaterial are not influenced by nonhomogeneity, however, the fields in FCM are influenced by nonhomogeneity in the terms of higher order, n$\geq$3. When the nonhomogeneous parameter in FGM is zero, or in area close to crack tip, the fields are identical to those of isotropic-isotropic bimaterial. Using these stress components, the effects of nonhomogeneity on stresses are discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.631-635
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• 1996

Stress singularities appear at the interface edge in dissimilar materials also under thermal loading. First, these singularities then an interface meets a free side surface with an arbitrary angle are studied for a two-dimensional problem. The singular properties under thermal loading are made clear and the concrete singular field are obtained. Secondly, the dependence of stress field on elastic constants in axisymmetric dissimilar materials are. discussed. That is, it is shown that three elastic constants mutually independent are necessary, in general, to characterize the stress field of axisymmetric dissimilar materials, although Dunders' parameters defined for two-dimensional dissimilar materials have been often applied correspondingly also to axisymmetric problems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.547-553
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• 1990

With alumina ceramics to copper brazement of cylindrical shape, the thermal stress analysis was carried out by finite element method. Elastic and plastic behaviour was considered to copper, but only elastic behaviour was considered to alumina. Also material properties of alumina and copper were considered in not constant values but variable functions dependent on temperature. The result of analysis is shown that maximum tensile longitudinal stress is occurred at perimeter of alumina side interface and maximum compressive radial and tangential stresses are occurred at center of alumina side interface. Because of bending effect, tensile raidial and tangential stresses are occurred at near bottom of alumina, far from interface.