• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1120-1124
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• 2007

Recently in the automotive brake industry brake squeal noise has become one of the top automotive quality warranty issues. The contact pressure is used to predict friction coupling in the brake squeal analysis. The formulation of friction coupling has performed by nonlinear static analysis prior to the complex eigenvalue analysis. This paper proposes a validation methodology of squeal analysis using modal testing and contact analysis and examines the effect of predicted contact pressure that leads to the discrepancy between unstable complex mode and squeal frequency. This studies compose a three step validation process : examining the modal characteristics of component and assembly loaded contact pressure using modal testing and FEM analysis and verifying the contact pressure distribution using nonlinear static analysis and experiment. Finally, the unstable modes from complex eigenvalue analysis and realistic squeal frequency from the noise dynamometer are investigated.

• Journal of Korean Physical Therapy Science
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• v.18 no.4
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• pp.59-64
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• 2011

Purpose : The purpose of this study was to evaluate the effects of the stretching of the calf muscles on foot pressure and contact area in young adult. Participants stood on a wedge board that was sloped between 15~25 degree for 15min. After stretching participants stood quietly on force plate, result was recorded. Participants stood on a force plate for 1 min in eye closed condition, and them the foot pressure and area was recorded. The following variables were calculated off-line: anterior and posterior foot pressure and contact area, medial and lateral foot pressure and contact area. Results showed that anterior pressure change due to stretch, but mediolateral was not significant. This result suggested that stretching of the calf muscle has the effect of increasing anterior pressure by flexibility change on calf muscle, so this effects might be effective intervention for reduce of serious problem to neurologic patients in therapy session.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.629-634
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• 1996

Heat generation in machine operating condition makes thermal deformation and thermalstress in the structure, which results in the change the contact characteristics of machine joint such s change of shrinkage fit, contact heat conductance and contact pressure. As the change of contact pressure is related to variation of static, dynamic and thermalcharacteristics, the prediction of transient contact perssure is strongly required. This paper presents some analytical results which will be effective to predict static and dynamic characteristics of the compound cylindrical structure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.244-249
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• 1997

Internal and external heat sources will cause to deform to machine elements in the contact joint of structure,which results in the change of contact pressure distribution different from initial assembly. Heat induced variations of contact pressure will change the static and dynamic properties such as contact stiffness,damping as well as contact heat conduction in the structure. In order to design and control the intelligent machine tool operating in variant conditions more sophisticatedly, the good prediction for the changes of prescribed propeties are strongly required especially in the contact elements adjacent to the rotational or linear bearing This paper presents some computational and experimental results in regard to static and dynamic characteristics of the press-fitted bush and shaft assembly which is a model of the bearing innerrace and shaft assembly. In the condition of heat generation on the outer surface of the bush,the effects of changes in the negative clearance and the heat flux on pressure distribution and dynamic properties are investigated. Results of this study show that the edge effect of the bush and the initial clearance have effects on the transient dynamic characteristics significantiy.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.6
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• pp.666-674
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• 2007

It is very important to estimate static squeezing pressure distributions for lining material of sterntube after bearing at dry dock stage since the maximum squeezing pressure value can be one of the significant characteristics representing coming navigation performances of the propulsion system. Moderate oil film pressure between lining material and propulsion shaft is also essential for safe ship service. In this paper, Hertz contact theory is explained to derive static squeezing pressure. Reynolds equation simplified from Navier-Stokes equation is centrally differentiated to numerically obtain dynamic oil film pressures. New shaft alignment technology of nonlinear elastic multi-support bearing elements is also used in order to obtain external forces acting on lining material of bearing. For 300K DWT class VLCC with synthetic bush of sterntube after bearing, static squeezing pressures are calculated using derived external forces and Hertz contact theory. Optimum partial slope of the after bush is presented by parametric shaft alignment analyses. Dynamic oil film pressures are comparatively evaluated for partially bored and unbored after bush. Finally it is proved that the partial slope can drastically reduce oil film pressure during engine running.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.139-148
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• 1998

Internal and external heat sources will cause to deform to machine elements in the contact joint of structure, which results in the change of contact pressure distribution different from initial assembly. Heat induced variations of contact pressure will change the static and dynamic properties such as contact stiffness, damping as well as contact heat conduction in the structure In order to design and control the intelligent machine tool operating in variant conditions more sophisticatedly, the good prediction for the changes of prescribed properties are strongly required especially in the contact elements adjacent to the rotational or linear bearing. This paper presents some computational and experimental results in regard to static and dynamic characteristics of the press-fitted bush and shaft assembly which is a model of the bearing innerrace and shaft assembly. In the condition of heat generation on the outer surface of the bush, the effects of changes in the negative clearance and the heat flux on pressure distribution and dynamic properties are investigated. Results of this study show that the edge effect of the bush and the initial clearance have effects on the transient dynamic characteristics significantly.

• Physical Therapy Rehabilitation Science
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• v.11 no.4
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• pp.421-429
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• 2022

Objective: The purpose of this study was to compare and analyze the effects of arch support taping on static balance, static/dynamic foot contact area, and ground reaction force during walking according to the types of elastic tapes with mechanical elasticity differences. Design: Cross-sectional study Methods: Twenty-six participants selected for flexible flat feet through the navicular drop test were randomly assigned to non-taping, Dynamic-taping, and Mechano-taping conditions. Static balance and foot contact area were compared in the standing posture according to arch support taping conditions, and foot contact area and ground reaction force were compared during walking. Results: There was no significant difference in static balance according to the taping condition in the standing position, but the foot contact area in the Mechano-taping condition showed a significant decrease compared to the non-taping condition (p<0.05). The foot contact area during walking significantly decreased in the Dynamic-taping and Mechano-taping conditions (p<0.05), but there was no significant difference between the ground reaction force. Conclusions: Based on the results of this study, it was confirmed that among the types of elastic taping, arch support taping using dynamic taping and Mechano-taping has the effect of supporting the arch with high elastic recovery. Any type of elastic tape can be used for arch alignment in flexible flat foot.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.2
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• pp.31-36
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• 2001

Teflon-like fluorocarbon thin film was deposited by using difluoromethane$(CH_2F_2$) added with Ar, $O_2$, and $CH_4$ on Si, $SiO_2$, TEOS, and Al substrate. The deposited thin film was characterized by static contact angles for measuring hydrophobicity in various additive gas ratio. temperature, and working pressure. In case of addition with Ar, the static contact angles decreased as additive gas ratio and power increased. But the static contact angles increased as working pressure increased. Specially, super-hydrophobic surface was obtained using the powder-like fluorocarbon thin film above 2 Torr. Added with $O_2$, the static contact angles decreased as the $O_2$ ratio and working pressure increased. And the static contact angles did not change in 100W, but hydrophilic surface was obtained at 200W. In case of addition of CE$_4$, static contact angles dramatically increased in $CH_4/CH_2F_2$ ratio 5. And continuous static contact angles obtained above ratio 5. As compare with previous experiments by thermal evaporation, the fluorocarbon thin film by plasma polymerization was obtained very low hysteresis. This results shows more homogenous surface by plasma polymerization than thermal evaporation process.

• Structural Engineering and Mechanics
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• v.72 no.5
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• pp.557-568
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• 2019

Accurate modeling of contact interface in bolted joints is crucial in predicting the dynamic behavior for bolted assemblies under external load. This paper presents a contact pressure distribution based non-uniform virtual material method to describe the joint interface of assembly structure, which is connected by sparsely distributed multi-bolts. Firstly, the contact pressure distribution of bolted joints is obtained by the nonlinear static analysis in the finite element software ANSYS. The contact surface around bolt hole is divided into several sub-layers, and contact pressure in each sub-layer is thought to be evenly. Then, considering multi-asperity contact at the micro perspective, the relationship between contact pressure and interfacial virtual material parameters for each sub-layer is established by using the fractal contact theory. Finally, an experimental platform for the dynamic characteristics testing of a beam lap structure with double-bolted joint is constructed to validate the efficiency of proposed method. It is found that the theoretical results are in good agreement with experimental results by impact response in both time- and frequency-domain, and the relative errors of the first four natural frequencies are less than 1%. Furthermore, the presented model is used to examine the effect of rough contact surface on dynamic characteristics of bolted joint.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.707-710
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• 2001

Brakes are one of the important safety parts in cars. The requirements of brakes in performance, in comfort, and working lifetime are high. This paper presents the static analysis on the stress and temperature of a automotive drum brake. The particular interest is the distribution of the contact pressure between brake lining and drum. The problems to be solved are the effects of friction coefficient, actuation force, temperature, and brake component's stiffness. The contact problem includes friction, and is solved using the ABAQUS.