• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.261-268
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• 2004

For cam and roller-follower contacting surfaces, the effect of tangential loading on the subsurface stress field at an elaso-hydrodynamic lubrication condition has been studied numerically. As tangential load increases, the subsurface stress field extended more widely to the direction of the tangential load. The positions of the maximum shear stress and the maximum effective stress are getting closer to the surface with the increasing tangential load. The tangential load at the elasto-hydrodynamic lubrication condition is of little consequence to the subsurface stress field.

• Tribology and Lubricants
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• v.16 no.2
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• pp.138-143
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• 2000

The sealing performance of an elastomeric O-ring seal with a temperature gradient has been analyzed for the contact stress behaviors that develop between the O-ring seal and the housing surfaces with which it comes into contact in the dovetail groove. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry (grooved), are investigated using the finite element method. The FE analysis includes material hyperelasticity and axisymmetry The computed FEM results show that the contact stress behaviors are related to a compression rate and a temperature gradient between the vacuum chamber with a dovetail groove and the contacting plate with a cooling jacket.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.55-62
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• 1994

For theoretical estimate of closed-die forging pressure, upper-bound method is applied to the involute tooth profile. In the analysis, the deformation regions have been divided into several zones. A constant frictional stress has been assumed on the contacting surfaces. Utilizing the formulated velocity fields, numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth and friction factor, on the forging of spur gears. Very close agreement was found between the predicted values of forging load and those obtained from experimental results.

• Structural Engineering and Mechanics
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• v.23 no.3
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• pp.309-323
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• 2006

In this paper, seismic response of a free-standing ship located in a dry dock and supported by an arrangement of n keel blocks due to base excitation is addressed. Formulation of the problem including derivation of governing equations in various modes of motion as well as transition conditions from one mode to another is given in Moghaddasi and Bargi (2006) by same authors. On the base of numerical solution for presented formulation, several numbers of analyses are conducted to study sensitivity of system's responses to some major contributing parameters. These parameters include friction coefficients between contacting surfaces, block dimensions, peak ground acceleration, and the magnitude of vertical ground acceleration. Finally, performance of a system with usual parameters normally encountered in design is investigated.

• Tribology and Lubricants
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• v.25 no.2
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• pp.114-119
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• 2009

Fretting occurs wherever short amplitude reciprocating sliding between contacting surfaces is sustained for a large number of cycles. The fundamental characteristic of fretting is the very small amplitude of sliding and combination of different wear mechanism. Predicting wear is important to enhance reliability of the parts. The objective of this paper is to predict fretting wear by using a contact analysis considering wear process. This construction will give us important information to know a property of fretting wear.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.329-336
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• 2009

A fretting wear test rig for cross contacting tube specimens, which employs a piezoelectric actuator, has been developed. Along with the simple loading scheme using dead weights, the rig is very simple to be used also. The accuracy was found acceptable. Inconel 690 tubes were tested in room temperature and ambient condition. Normal load and sliding amplitude range up to 35N and $100{\mu}m$, respectively. The sizes of wear scar and the wear volumes were measured, and wear coefficients have been calculated based on those. A study on the fretting wear mechanism of the tubes has been attempted via microscopic observation. Rugged wear surfaces are induced by the separation and adhesion of particles and formation and subsequent fracture of surface layers. Lapped specimens were also tested and abrasive wear seems to be playing a dominant role.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.52-56
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• 1992

A kinematically admissible velocity field for closed-die forging of spur gear is proposed. The velocity field is divided into three regions of deformation. In the analysis, the involute curve is approximated to be straight line and the upper-bound method is used to calculate energy dissipation rate. A constant frictional factor has been assumed on the contacting surfaces. The effects of root diameter relative pressure is independent of root diameter for the same number of teeth, but increases with the number of teeth on a given root diameter. In the presence of friction, relative forging pressure increases with increasing root diameter at the start of forging, but decreases with increasing root diameter in the processing of forging.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.293-298
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• 1998

In surface grinding, the conditions of the grinding wheel give a significant effect on the ground workpieces comparing with other metal removal processes. In this paper, to assist the development, a non-contacting optical method is introduced to make in-process measurements of scattering intensities from laser beam during surface grinding processes. This show indications of changes in surface texture of wheel working surfaces. Also, in order to determine the dressing time monitoring method of grinding wheel in surface grinding, a three-dimensional computer simulation of the grinding operation has been attempted based on the contact mechanism and surface-shaping system between the grinding wheel and the workpiece. The optical dressing time is determined based on the amount of the grain wear and work surface roughness.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.283-288
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• 1999

The sealing performance of an elastomeric O-ring seat with a temperature gradient has been analyzed for the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry (grooved), are investigated using the finite element method. The analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to a compression rate and a temperature gradient between the vacuum chamber with a groove and the contacting plate with a cooling jacket.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.160-165
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• 1999

In surface grinding, the conditions of the grinding wheel give a significant effect on the ground workpieces comparing with other metal removal provesses. In this paper, to assist the development, a non-contacting optical method by the laser beam is introduced. The in-process measurement of scattering intensities has been made during surface grinding processes and the surface textures of wheel working surfaces are captured. Also, in order to determine the dressing time monitoring method of a grinding wheel, a three-dimensional computer simulation of the grinding operation has been attempted based on the contact mechanism and the surface-shaping system between the grinding wheel and the workpiece. The optimal dressing time is determined by the amount of the grain wear and work surface roughness.