• Journal of Power System Engineering
• /
• v.21 no.6
• /
• pp.21-30
• /
• 2017

This study deals with the characteristics of degraded stainless steel. Stainless steel is heat treated to ensure mechanical properties when designing or manufacturing machinery parts or equipment. In this study, the mechanical properties and wear characteristics of three kinds of stainless steels after artificially heat-treated at 753 K~993 K, where chrome depletion occurs near the grain boundary, were evaluated. The microstructure and fracture surface were also observed. From the results, friction coefficient and wear loss decreased with increasing the heat treatment temperature regardless of the type of stainless steel. Also, as the tensile strength increased, the friction coefficient and wear loss decreased. Wear loss showed proportional to a tendency to increase with increasing friction coefficient.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1473_1474
• /
• 2009

To develop electrically reliable high voltage apparatuses, the experimental study on the electrical breakdown field strength is needed, as well as theoretical approach. In this paper, lightning impulse breakdown characteristics considering utilization factors are investigated for the establishment of insulation design criteria of an high voltage apparatus. The utilization factors are represented as the ratio of mean electric field to maximum electric field. Dielectric experiments are performed by using five kinds of sphere-plane electrode systems made of stainless steel. As a result, it is found that dielectric characteristics are affected by not only gap length but also utilization factor of electrode systems. The results are expected to be applicable to the design of high voltage apparatuses.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.6
• /
• pp.130-141
• /
• 2000

The virbration characteristics of a passenger car steering column are studied by using a modal test and a finite element (FE) analysis. To verify the FE model and the results, an experiment using the impact exciting method is performed. Two types of the steering column in this study are considered as follows; (ⅰ) the non-tilt type steering column and (ⅱ) the upper-tilt type steering column. The experimental results are compared with those o the FE analysis, and it ti shown that the results agree with each other. The effects of various design parameters such as the bracket thickness, the column diameter on the natural frequencies are also investigated by FE analysis.

• Tribology and Lubricants
• /
• v.23 no.1
• /
• pp.29-36
• /
• 2007

It necessarily follows that wear particles are generated through a friction and wear in a mechanical moving system. The wear particles are relative to the failure and the life of machine elements directly. To analyze the wear particle, its shape characteristics were calculated quantitative values such as diameter, roundness and fractal parameters by digital image processing. In this study, the histograms of shape parameters of wear particles were used for the purpose of analyzing the distribution of wear particles in various conditions. We consider that the histogram of shape parameter can be effectively represented to study a wear mechanism.

• International Journal of Fluid Machinery and Systems
• /
• v.7 no.1
• /
• pp.7-15
• /
• 2014

In the present study, a computational analysis of the flow in a centrifugal blower is carried out to predict a performance and to explain noise characteristics of the blower. Unsteady, 3D Navier-Stokes equations were solved with k-${\varepsilon}$ turbulence model using CFX software. CFD results were compared with the experimental data that is acquired from an experiment conducted with the same blower. The pressure fluctuation in the blower was transformed into the frequency domain by Fourier decomposition to find the relationship between flow behaviors and noise characteristics. Sound pressure level (SPL) which is obtained from wall pressure fluctuation at impeller outlet represents relative overall sound level of the blower well. Sound spectra show that there are some specific peak frequencies at each mass flow rate and it can be explained by flow pattern.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.10a
• /
• pp.207-210
• /
• 2003

Vacuum hot pressing has been used for the development of Ti-MMCs using foil-fiber-foil method, and subsequent micro-mechanical characteristics of the composites are evaluated by means of several experimental processes. As shown by the results, fiber strength degradation occurs during the consolidation, and particularly residual stresses results from the thermal expansion mismatch between fiber and matrix materials during cooling process are incorporated in the changes of mechanical properties of the composites. In industrial applications, the processing conditions avoiding micro-material failures are important together with the properties of finished products, and therefore should be included in the assesment of the material characterization.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.5
• /
• pp.1534-1542
• /
• 1996

Gear vibration is caused by the mesh stiffness, gear accuracy, and assembling errors. For these reasons, helical gear has the azial, radial, and rotational vibrations. In this study, the mesh stiffness is calculated by considering the tooth bending, contact, and foundation deformations. Rotational vibration of helical gear with tooth error is modeled by the nonlidear equation of motion with single degree of freedom and is anlyzed numerically. Also, by a specially designed experimental set-up, the analysis are cross-checked and the vibration characteristics of helical gear are discussed.

• Journal of Mechanical Science and Technology
• /
• v.15 no.12
• /
• pp.1639-1646
• /
• 2001

It is often necessary that the joints characteristics should be determined in the early stage of the vehicle body design. The researches on identification of joints in a vehicle body have been performed until the recent year. In this study, the joint characteristics of vehicle structure were expressed as the condensed matrix forms from the full joint stiffness matrix. The condensed joint stiffness matrix was applied to typical T-type and Edge-type joints, and the usefulness was confirmed. In addition, it was applied to the real center pillar model and the full vehicle body in order to validate the practical application.

• Journal of Mechanical Science and Technology
• /
• v.20 no.7
• /
• pp.1051-1058
• /
• 2006

The steady aerodynamic characteristics of a wing flying over a channel are investigated using a boundary-element method. The present method is validated by comparing the computed results with the measured data. Compared with a flat ground surface, the channel fence augmented the lift increase and induced drag reduction. When the fence is lower than the wing height, the gap between the wingtip and the fence does not affect the aerodynamic characteristics of the wing much. When the fence is higher than the wing height, the close gap increased the lift. The induced drag is reduced when the wing is placed near the ground or at the same height as the fence. It is believed that present results can be used in the conceptual design of the high-speed ground transporters flying over the channel.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.08a
• /
• pp.137-144
• /
• 2004

The drawbead is one of the most important factors in sheet metal forming for automotive parts. So clarifying the friction characteristics between sheets and drawbead is essential to improve the formability of sheet metal. Therefore in this study, drawbead friction test was performed at circular shape bead and rectangular shape bead. The results show that the tendency of drawing force for rectangular bead is nearly similar with circular bead and the drawing force is nearly proportional to friction coefficient.