• Structural Engineering and Mechanics
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• v.15 no.4
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• pp.477-493
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• 2003

Masonry is not a simple material, the influence of mortar joints as a plane of weakness is a significant feature and this makes the numerical modelling of masonry very difficult especially when dynamic (seismic) analysis is involved. In order to develop a simple numerical model for masonry under earthquake load, an analytical model based on Distinct Element Method (DEM) is being developed. At the first stage, the model is applied to simulate the in-plane shear behaviour of an unreinforced masonry wall with and without opening where the testing results are available for comparison. In DEM, a solid is represented as an assembly of discrete blocks. Joints are modelled as interface between distinct bodies. It is a dynamic process and specially designed to model the behaviour of discontinuities. The numerical solutions obtained from the distinct element analysis are validated by comparing the results with those obtained from existing experiments and finite element modelling.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.642-651
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• 1988

The present paper develops finite element procedures to calculate displacements, strains and stresses in initially stressed elastic solids subjected to static or time-dependent loading conditions. As a point of departure, we employ Hamilton's principle to obtain nonlinear equations of motion characterizing the displacement in a solid. The equations of motion reduce to linear equations of motion if incremental stresses are assumed to be infinitesimal. In the case of linear problem, finite element solutions are obtained by Newmark's direct integration method and by modal analysis. An analytic solution is referred to compare with the linear finite element solution. In the case of nonlinear problem, finite element solutions are obtained by Newton-Raphson iteration method and compared with the linear solution. Finally, the effect of the order of Gauss-Legendre numerical integration on the nonlinear finite element solution, has been investigated.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.111-129
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• 2019

Recently, all-solid-state batteries (ASSBs) have attracted increasing interest owing to their higher energy density and safety. As the core material of ASSBs, the characteristics of the solid electrolyte largely determine the performance of the battery. Thus far, a variety of inorganic solid electrolytes have been studied, including the NASICON-type, LISICON-type, perovskite-type, garnet-type, glassy solid electrolyte, and so on. The garnet Li₇La₃Zr₂O₁₂ (LLZO) solid electrolyte is one of the most promising candidates because of its excellent comprehensively electrochemical performance. Both, experiments and theoretical calculations, show that cubic LLZO has high room-temperature ionic conductivity and good chemical stability while contacting with the lithium anode and most of the cathode materials. In this paper, the crystal structure, Li-ion transport mechanism, preparation method, and element doping of LLZO are introduced in detail based on the research progress in recent years. Then, the development prospects and challenges of LLZO as applied to ASSBs are discussed.

• Journal of Korean Neurosurgical Society
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• v.60 no.6
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• pp.611-619
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• 2017

Objective : In addition to bone bridging inside a cage or graft (intragraft bone bridging, InGBB), extragraft bone bridging (ExGBB) is commonly observed after anterior cervical discectomy and fusion (ACDF) with a stand-alone cage. However, solid bony fusion without the formation of ExGBB might be a desirable condition. We hypothesized that an insufficient contact area for InGBB might be a causative factor for ExGBB. The objective was to determine the minimal area of InGBB by finite element analysis. Methods : A validated 3-dimensional, nonlinear ligamentous cervical segment (C3-7) finite element model was used. This study simulated a single-level ACDF at C5-6 with a cylindroid interbody graft. The variables were the properties of the incorporated interbody graft (cancellous bone [Young's modulus of 100 or 300 MPa] to cortical bone [10000 MPa]) and the contact area between the vertebra and interbody graft (Graft-area, from 10 to $200mm^2$). Interspinous motion between the flexion and extension models of less than 2 mm was considered solid fusion. Results : The minimal Graft-areas for solid fusion were $190mm^2$, $140mm^2$, and $100mm^2$ with graft properties of 100, 300, and 10000 MPa, respectively. The minimal Graft-areas were generally unobtainable with only the formation of InGBB after the use of a commercial stand-alone cage. Conclusion : ExGBB may be formed to compensate for insufficient InGBB. Although various factors may be involved, solid fusion with less formation of ExGBB may be achieved with refinements in biomaterials, such as the use of osteoinductive cage materials; changes in cage design, such as increasing the area of polyetheretherketone or the inside cage area for bone grafts; or surgical techniques, such as the use of plate/screw systems.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.881-889
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• 2010

A volume integral equation method (VIEM) is introduced for solving the elastostatic problems related to an unbounded isotropic elastic solid; this solid is subjected to remote uniaxial tension, and it contains multiple interacting isotropic inclusions. The method is applied to two-dimensional problems involving long parallel cylindrical inclusions. A detailed analysis of the stress field at the interface between the matrix and the central inclusion is carried out; square and hexagonal packing of the inclusions are considered. The effects of the number of isotropic inclusions and different fiber volume fractions on the stress field at the interface between the matrix and the central inclusion are also investigated in detail. The accuracy and efficiency of the method are clarified by comparing the results obtained by analytical and finite element methods. The VIEM is shown to be very accurate and effective for investigating the local stresses in composites containing isotropic fibers.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.1
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• pp.55-62
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• 1985

This study modeled in axisymmetric solid elements and analyzed the neighbourhood of the contact surface zone between liner and block in a diesel engine. The results of finite element analysis show that this model is deformed by bolt jointed load and pressure load and that stresses can vary much due to major dimensional changes in the joint area. Guidelines have been developed for selecting fillet radii and for the width of the contact area between liner and block.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.244-248
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• 2001

A solid modeller was developed in this paper. Representation scheme of modelling is nonmanifold B-rep. While many B-rep modelers use edges as basic element of modelling, this modeller is triangle-based. New modelling element, split triangle that is composed of 3 pure half-edges and has no information about the adjoining triangles, was defined to enlarge the range of representation. Corresponding algorithms for Boolean set operations were also developed.

• Tribology and Lubricants
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• v.14 no.1
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• pp.28-36
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• 1998

This paper presents the thermal behaviours of a solid type disk brake for a high-speed train. The thermal behaviours of a brake disk with 50mm thickness shows good performance compared with 45mm thickness of a disk because of a high specific heat capacity. The FEM results show that the thickness of the disk with a same weight of the brake disk should be increased for a good flexibility of the contact thermal problems. Therefore, the ratio between the pad and disk in diameter may be reduced and the thickness of a disk increased.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.207-212
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• 1993

In the construction of underground structures, it is critical to accurately predict the ground deformations during excavation. In this paper, a finite element procedure for the computation of solid displacement and fluid pore pressure during incremental excavation is presented based on Biot's theory. The numerical formulation is done using the virtual work principle. The proposed procedure is applied to some example problems with different excavation rates and permeabilities.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.39-44
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• 2002

A three node triangular element with drilling rotations incorporating Improved Layerwise Zig-zag Theory(HZZT) is developed to analyze the vibration of spinning pretwisted composite blades with embedded damping layer. Matching conditions at the interfaces between the damping material and the border material are enforced by setting the shear forces matched and different shear strains along the interfaces. The natural frequencies and modal loss factors of cantilevered pretwisted composite blade with damping core are calculated with the present triangular element enforcing the matching conditions and compared to experimental results and MSC/NASTRAN results using a layered combination of plate and solid elements.