• Journal of the Korean Geotechnical Society
• /
• v.32 no.12
• /
• pp.5-13
• /
• 2016

In this study, Coupled Eulerian-Lagrangian (CEL) analysis, which is one of the large deformation analyses, was incorporated to investigate excavation damage zone (EDZ) under TBM advancement. Considering the quasi-static condition, the dynamic analysis was performed to simulate the real TBM advancement and subsequently a case study on mesh and TBM excavation rate was carried out for satisfying a balance of accuracy and economic computational time. Based on this, a series of parametric studies were performed for different rock types and tunnel diameters. From the numerical analysis results, it is found that EDZ was taken to range within 0.4D(D=tunnel diameter) for most rocks. It is also found that the EDZ tends to increase as the tunnel diameter increases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.244-249
• /
• 2002

Rubber seat is extensively used to reduce the vibration of machine or structure. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material for design function. However, there are still a lot of difficulties to analyze static characteristics of rubber components with hyper elasticity and nonlinear large deformation. In this paper material property is obtained by strain-stress curve using a tension test. Mooney-Rivlin Coefficients are gotten by fitting strain-stress curve. The visco-elastic characteristics of refrigerator rubber mount is determined by using ANSYS. And to minimize the rubber stiffness, the rubber seat shape optimization is performed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.330.1-330
• /
• 2002

Elastomer is extensively used to reduce of vibration machine or structure. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material fur design function. However, there are still a lot of difficulties to analyze static characteristic of rubber components with hyper elasticity and nonlinear large deformation. In this paper material property is obtained by strain-stress curve using a tension test. (omitted)

• Journal of Korean Association for Spatial Structures
• /
• v.1 no.2 s.2
• /
• pp.85-92
• /
• 2001

The structural behaviors of anisotropic laminated shells are quite different from that of isotropic shells, Also, the classical theory of shells based on neglecting transverse shear deformation is invalid for laminated shells. Thus, to obtain the more exact behavior of laminated shells, effects of shear deformation should be considered in the analysis. As the length of x-axis or y-axis is increase, the effects of transverse shear deformation are decrease because the stiffness for the axis according to the increasing of length is large gradually. In this paper, the governing equations for anisotropic laminated shallow shell including the effects of shear deformation are derived. And then, by using Navier's solutions for shallow shells having simple supported boundary, extensive numerical studies for anisotropic laminated shallow shells were made to investigate the effects of shear deformation for 3 typical shells. Also, static analysis is carried out for cross-ply laminated shells considering the effects of various geometrical parameters, e,g., the shallowness ratio, the thickness ratio and the ratio of a(length of x-axis)-to-b(length of y-axis). The results are compared with existed one and show good agreement.

• Journal of the Korean Society for Railway
• /
• v.13 no.1
• /
• pp.84-91
• /
• 2010

We built multi-purpose large triaxial testing system that can test and evaluate various geotechnical design parameters such as shear strength, deformation modulus and stress-strain behaviour for large diameter granular materials, which are the most commonly used construction materials in the railway, road embankments. The details of the built testing system and the results obtained from static triaxial test carried out for gneiss ballast material are discussed within the scope of this paper. Ballast is hardly saturated and is confined at low overburden pressure, since the depth is shallow and the permeability is very high. Herein we ascertained that the confining pressure can effectively be controlled by vacuum. The rational trend could be checked up through triaxial test results such as shear strength, deformation, and particle breakage. And the shear strength envelope could be non-linearly represented with the parent rock strength, confining pressure of the triaxial test and proper parameters.

• Smart Structures and Systems
• /
• v.20 no.2
• /
• pp.151-162
• /
• 2017

In practical engineering, the friction damper is a widely used energy dissipation device because of its large deformation capacity, stable energy dissipation capability, and cost effectiveness. While based on conventional friction dampers, the double-sliding friction damper (DSFD) being proposed is different in that it features two sliding friction forces, i.e., small and large sliding friction forces, rather than a single-sliding friction force of ordinary friction dampers. The DSFD starts to deform when the force sustained exceeds the small-sliding friction force, and stops deforming when the deformation reaches a certain value. If the force sustained exceeds the large sliding friction force, it continues to deform. Such a double-sliding behavior is expected to endow structures equipped with the DSFD better performance in both small and large earthquakes. The configuration and working mechanism of the DSFD is described and analyzed. Quasi-static loading tests and finite element analyses were conducted to investigate its hysteretic behavior. Finally, time history analysis of the single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) systems were performed to investigate the seismic performance of DSFD-equipped structures. For the purpose of comparison, tests on systems equipped with conventional friction dampers were also performed. The proposed DSFD can be realized perfectly, and the DSFD-equipped structures provide better performances than those equipped with conventional friction dampers in terms of interstory drift and floor acceleration. In particular, for the MDOF system, the DSFD helps the structural system to have a uniform distributed interstory drift.

• Journal of Biomedical Engineering Research
• /
• v.24 no.3
• /
• pp.233-239
• /
• 2003

Falling related injuries are categorized as the most serious and common medical problems experienced by the elderly, hip joint fracture, one of the most serious consequences of falling in the elderly, occurs in only about 1% of falling. Nevertheless, hip fracture accounts for a considerable part of the disability, death, and medical costs associated with falling. In this study, we considered the impact angle and displacement rate in falling as another factor affecting femoral strength. Using a fresh-frozen human femur, we developed system to simulate the falling condition and then conducted the experiments changing the impact angle (0$^{\circ}$, 15$^{\circ}$, 30$^{\circ}$) of proximal femur. Also, in order to analyze the relative risk due to falling to normal situation in proximal femur, we did the static test simulating the two-legged stance condition. The results showed that the change in impact angle affected the strain distribution in proximal femur, and that a large deformation in femoral neck than in other sites. Furthermore despite low impact velocity, a large deformation in proximal femur occurred in the impact test and different strain distribution was observed compare to the static case.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1335-1340
• /
• 2007

The media transport systems, such as printers, copy machines, facsimiles, ATMs, cameras, etc. have been widely used and being developed rapidly. In the development of those sheet-handling machineries, it is important to predict the static and dynamic behavior of the sheet with a high degree of reliability because the sheets are fed and stacked at such a high speed. Flexible media are very thin, light and flexible, so they behave in geometric nonlinearity with large displacement and large rotation but small strain. In the flexible media analysis, aerodynamic effect from the surrounding air must be included because any small force can make large deformation. In this paper, surrounding air was modeled by incompressible Navier-Stokes flow and an arbitrary Lagranigan-Eulerian(ALE) finite element method with automatic mesh-updating technique was formulated for large domain changes. In the numerical simulations, the results with consideration of the air fast decayed and converged into static results while the results without considering air oscillated continuously.

• Proceedings of the KSR Conference
• /
• 2005.05a
• /
• pp.115-122
• /
• 2005

This study analyzed the characteristics of four kinds of bridge rubber pads and suggested how to determine the stiffness the pads. The stiffness of rubber pads can be estimated by a direct static test. In the procedure to estimate the stiffness of a pad, the dead load(preload) of a bridge and live load of a vehicle are considered. The polyurethane rubber pads have larger hardness than natural and chloroprene rubber pads and thus carry larger load bearing capacity. In addition, they showed higher stiffness with the same shape factor than the others and thus are more avaliable as for bridge bearings. Although natural and chloroprene rubber pads are elongated to large deformation in horizontal direction due to vertical loads, polyurethane rubber pads almost do not generate horizontal deformation due to vertical loads regardless to the thickness and hardness of the pads. Therefore, they do not need reinforced plate to restrict horizontal deformation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.8
• /
• pp.760-766
• /
• 2009

In the manufacturing process of HDD, ball swaging method is commonly used to joint the Head Gimbal Assembly(HGA) with the arm of the actuator. The hub on the HGA is placed into the hole of the actuator arm, and the hub and arm is bonded by the pressure of steel ball. The pressure for plastic deformation on the baseplate causes the undesirable deformation on HGA, such as tilting, flying height change of head. After obtaining the key parameters that have large sensitivity on the swaging process, the optimal shape of baseplate is proposed to increase the static performance during swaging process. Contribution of the proposed design for the swaging performance is verified by contact simulation with elasto-plastic deformation.