• Structural Engineering and Mechanics
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• v.41 no.6
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• pp.751-758
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• 2012

We study thickness-shear (TSh) free vibrations of an unbounded, laminated elastic plate with three layers of different materials. One of the two interfaces is slightly weakened as described by the shear-lag model that allows the displacement to be discontinuous across the interface. A frequency equation is obtained from the linear theory of elasticity. A perturbation solution of the frequency equation is obtained from which the frequency shifts of TSh modes due to the weakened interface can be calculated. It is shown that the frequency shifts of TSh modes of different orders are different, and they satisfy different conditions when different interfaces are weakened. These conditions are obtained which can potentially be used as criteria for determining specifically which interface is weakened.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.441-444
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• 2007

This paper presents a part of micormechanics-based elastic modeling (Lee and Pyo, 2007) of particle-reinforced composites containing slightly weakened interfaces. The Eshelby's tensor for a damaged ellipsoidal inclusion to model particles with slightly weakened interfaces is incorporated into a micormechanical formulation by Ju and Chen (1994). A damage model in accordance with the Weibull's probabilistic function is also developed to simulate the progression of weakened interface in the composites.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.51-58
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• 2008

A constitutive model based on a combination of a micromechanics-based weakened interface elastic model (Lee and Pyo, 2007) and a crack nucleation model (Karihaloo and Fu, 1989) is proposed to predict the effective elastic behavior of particle-reinforced composites. The model specifically considers imperfect interfaces in particles and microcracks in the matrix. To exercise the proposed constitutive model and to investigate the influence of model parameters on the behavior of the composites, numerical simulations on uniaxial tension tests were conducted. Furthermore, the present prediction is compared with available experimental data in the literature to verify the accuracy of the proposed constitutive model.

• Advances in materials Research
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• v.8 no.4
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• pp.295-311
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• 2019

In this study, a three-dimensional Finite Element Model has been developed to estimate the size of the weakened zone in a bi-material a ceramic bonded to metal. The calculations results were compared to those obtained using Scanning Electron Microscope (SEM). In the case of elastic-plastic behaviour of the structure, it has been shown that the simulation results are coherent with the experimental findings. This indicates that Finite Element modeling allows an accurate prediction and estimation of the weakening effect of residual stresses on the bonding interface of Alumina. The obtained results show us that the three-dimensional numerical simulation used by the Finite Element Method, allows a good prediction of the weakened zone extent of a ceramic, which is bonded with a metal.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.56-59
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• 2008

This paper presents results of a parametric study for a constitutive model (Lee et ai, 1989) for particle-reinforced composites considering weakened interfaces and crack nucleation. Eshelby's tensors for particles with imperfect interfaces (Ju and Chen, 1994) and microcracks (Sun and Ju, 2004) are incorporated into a micromechanical formulation. A parametric study for the microcrack nucleation parameter ${\phi}_{{\upsilon}0}$ and ${\epsilon}^{th}$ is conducted to investigate the sensitivity of the parameter to the constitutive model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1667-1675
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• 2001

Numerical simulations are carried out for the liquid encapsulant Czochralski(LEC) by imposing a magnetic field. The use of a magnetic field to the crystal growth is to suppress melt convection and to improve the homogeneity of the crystal. In the present numerical investigation, we focus on the range of 0-0.3Tesla strength for the axial and cusped magnetic field and the effect of the magnetic field on the melt-crystal interface, flow field and temperature distribution which are the major factors to determine the quality of the single crystal are of particular interest. For both axial and cusped magnetic field, increase of the magnetic field strength causes a more convex interface to the crystal. In general, the flow is weakened by the application of magnetic field so that the shape of the melt-crystal interface and the transport phenomena are affected by the change of the flow and temperature field.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.415-421
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• 2018

A location determining method is proposed for critical sliding surface in the stability analysis of the filling materials in karst caves. First, a preliminary location of the sliding surface is determined based on simulation results which includes displacement contour and plastic zone. The sliding surface will locate on the bottom contact interface when the friction angle is relative small. However, a weakened contact interface always becomes the critical sliding surface no matter what the friction angle is. Then when the friction angle becomes larger, the critical sliding surface inside fillings can be determined by a parabola, the coefficient of which increases linearly with the friction angle under the same cohesion. Finally, the critical sliding surface approximately remains unchanged with friction angle. The influence of cohesion is similar to that of friction angle. Although affected by shape, size or position of the karst cave, the critical sliding surface mainly depends on both friction angle and cohesion. Thus, this method is always useful in determining the critical sliding surface.

• Journal of Welding and Joining
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• v.20 no.4
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• pp.517-524
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• 2002

An overlaying of the seating surfaces of engine valves by OAW, GTAW or PTA weldings are common practice. The OAW method of a lower torch energy density compared to GTAW and PTA methods produces smoother deposits but the pain size at the vicinity of the interface is increased remarkably up to $30~50{\mu\textrm{m}}$ (that of base metal is about $10\mu\textrm{m}$). It's grain coarsening and the solute dilution are related to the decarburizing during OAW could be minimized by reducing the preheating temperature and by maintaining the carbide precipitates in base metal prior to welding. The formation of columnar structures and carbide precipitation zone in the vicinity of the GTAW welded interface, because of the high heat concentration, causes weakened zone on the valve seat face. The width of the reaction boundary zone is about $50\mu\textrm{m}$ for PTA and GTAW overlaying, and about $150\mu\textrm{m}$ for OAW welding. The smaller width of the reaction boundary zone is the less the solute-dilution rate. Thereby PTA welding may be recommended for overlaying of the seating surfaces.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1543-1548
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• 2007

This paper reports a study on determination of the adequate location of 100 MVA STATCOM regarding the transfer capability enhancement on the metropolitan interface as well as the economy in system operation. The base case in the study was established considering a scenario of the energy support to North Korea from the KEPCO (Korea Electric Power Corporation) system through a HVDC interconnection. In the base case, the energy support was approximately modeled with a load of 1500 MW, and by the load addition, the system was weakened in terms of voltage stability and transfer capability. After a thorough investigation on the case, the location of the STATCOM was decided to compensate the reactive deficit of the modified system and to maximize the operational benefit which can be estimated by FV analysis.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.152-163
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• 1995

This experiment was performed to observe the adhesion pattern and microleakage in the gingival margin according to variation in the resin cement thickness which results from thickness of Die spacer. which is considered to effect the adaptability of the composite resin inlays. Clearfil CR inlays were fabricated on stone models with CR Sep applicated once and Nice fit twice, 4 times, and 6 times each. After 2nd curing within the CRC-100 oven, CR inlays were cemented with CR inlay cement. Dye(2% methylene blue) penetration and adhesion pattern were evaluated after sectioning of gingival margin into :3 pieces. The results were as follows ; 1. The thickness of resin cement showed unevenchanging pattern with that of die spacer, namely, it was increased until 4 times' application of Nice-Fit but was decreased with 6 times' application of that. 2. The degree of dye penetration wasn't affected by cement thickness within a limited value. 3. Most of dye penetration was shown through the interface between cement and enamel rather than the interface between cement and CR inlay. This shows that the affinity of resin cement for CR inlay was superior to the adhesive strength with tooth structure. 4. No gap was found at the interface between enamel and cement but some showed separation between dentin and cement. It is concidered that the contraction force of cement was less than the bond strength with the enamel. 5. Lots of voids were found in the CR inlay and resin cement. There was a pooling tendency of bonding agent and cement in the axiogingival line angle portion. 6. In some specimens, cracks were shown in enamel margin. From this it could be considered that cavity preparation and surface treatment weakened the tooth structure.