• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.575-578
• /
• 2000

Die design to minimize the die wear in the cold forging process is very important as it reduce the production cost and the increase of the production rate. The quantitative estimation for the die wear is too hard because the prediction of the die wear is determined with many process variables. So, in this paper, the optimal shape of the backward extrusion punch is newly designed through the FE-analysis considering the surface expansion and Archard's wear model in order to reduce the rapid wear rate that is generated for the backward extrusion product exceeding the forming limit. The main shape variables of the backward extrusion punch are the flat, angle, and round of the punch nose part. As the flat and angle of the punch nose are larger, the surface expansion is reduced. and, the wear rate is decreased according to the reduction of the punch round. These results obtained through this study are applied to the real manufacturing process, it is implemented the reduction of the wear rate.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.6
• /
• pp.930-937
• /
• 2001

The friction and wear behavior of short carbon fiber reinforced polyetheretherketone was studied experimentally under dry sliding conditions against SCM440(AISI 4140) disks with different surface roughness and hardness at the low sliding speeds and the high pressures on a pin-on-disk apparatus. Under the low disk surface roughness value the earsplitting noise and stick-slip were occurred. The increased adhesion friction and wear factor with stick-slip made the friction and wear behavior worse. Under the high disk surface hardness the break and falling-off of carbon fibers were accelerated. The carbon fibers fallen off from the matrix were ground into powder between two wear surfaces and this phenomenon caused abrasive friction and wear factor to increase. So the friction and wear behavior became worse. With the transfer film made of wear particles formed on a disk, the carbon powder film formed on a pin lowered a friction coefficient.

• Design & Manufacturing
• /
• v.16 no.3
• /
• pp.28-33
• /
• 2022

The recent increasing application rate of advanced high-strength steel(AHSS) for automotive parts makes it difficult to ensure the durability of forming tools. Significant load and friction generated during the piercing process of AHSS increase the wear rate and the damage degree to dies. These harsh process conditions also yield product failures, such as dimensional inconsistency of pierced holes and insufficient quality of hole's sheared edge. This study analyzed the effect of punch wear on the sheared surface of pierced parts and the forming load during the piercing process. Wear-shaped punches showed approximately 20% higher piercing load than normal-shaped punches, and the rollover ratio of the sheared surface also increased. It is considered that the dull edge of wear-shaped punches does not penetrate directly into the material but shears after tensioning it in a piercing direction. In addition, wear-shaped punches experienced compressive load even after completing the piercing process during the down-stroke and tensile load during the up-stroke. This load variation is related to the smaller diameter piercing holes produced by wear-shaped punches compared to normal-shaped punches. Thus, we demonstrated the predictability of the wear level of dies through a comparative analysis of the piercing load pattern.

• Tribology and Lubricants
• /
• v.22 no.3
• /
• pp.144-148
• /
• 2006

The experimental investigation was performed to find the associated changes in characteristics of fretting wear with various water temperatures. The fretting wear tests were carried out using the zirconium alloy tubes and the grids with increasing the water temperature. The tube materials in water of $20^{\circ}C,\;50^{\circ}C\;and\;80^{\circ}C$ were tested with the applied load of 20 N and the relative amplitude of $200{\mu}m$. The worn surfaces were observed by SEM, EDX analysis and 2D surface profiler. As the water temperature increased, the wear volume was decreased, but oxide layer was increased on the worn surface. The abrasive wear mechanism was observed at water temperature of $20^{\circ}C$ and adhesive wear mechanism occurred at water temperature of $50^{\circ}C,\;80^{\circ}C$. As the water temperature increased, surface micro-hardness was decreased, but wear depth and wear width were decreased due to increasing stick phenomenon. Stick regime occurred due to the formation of oxide layer on the worn surface with increasing water temperatures

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.05a
• /
• pp.99-104
• /
• 2003

TiN coated films show a good mechanical properties, high thermal properties and wear, erosion and corrosion resistance and are widely used as a coating materials in tools, ornaments, parts and semiconductors. In spite of these good properties, the fracture of TiN coated films occur during use. The fracture of TiN thin films is related to their microstructure. Especially, the life of TiN coated layer is related to the texture of the TiN films. One researcher suggested that the corrosion and erosion resistance of the TiN thin films is related to a uniform and dense structure of films. In this study, we studied the relationships between textures and friction coefficient, erosion and corrosion in TiN coated films. The flatness of (115) texture surface of TiN thin films is flatter than that of (111) texture surface. The friction coefficient of (115) texture surface of TiN thin films is similar with that of (111) texture surface. The wear resistance of (115) texture surface of TiN thin films is better than that of (111) texture surface. The erosion and corrosion resistance of (115) texture surface of TiN thin films is better than that of (111) torture surface. As well as texture, the wear, erosion and corrosion of TiN thin films has to consider defects such as pinholes, cracks, surface roughness and open columnar structure. The life of TiN coated products is influenced by the properties of wear, erosion, and corrosion resistance of TiN thin films and is related to texture of TiN coated films, density of pinholes and cracks, density of structure, and surface flatness.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.199-200
• /
• 2002

Three-body abrasive wear resistance of mild steel, low alloy steel (Bisalloy) and 27%Cr white cast iron was investigated using a ball-cratering test. Glass beads, silica sand, quartz and alumina abrasive particles with sizes larger than $100{\mu}m$ were used to make slurries. It was found that the wear rates of all three materials tested increased with time when angular abrasive particles were used and were rather constant when round particles were used. This increase in wear rates was mainly due to the gradual increase in ball surface roughness with testing time. Abrasive particles with higher angularity caused higher ball surface roughness. Mild steel and Bisalloy were more affected by this ball surface roughness changes than the hard white cast iron. Generally, three-body rolling wear dominated. The contribution of two-body grooving wear increased when the ball roughness was significant. More grooves were found when round particles were used or the size of the particles was decreased.

• Journal of Korea Foundry Society
• /
• v.11 no.6
• /
• pp.482-490
• /
• 1991

This study presents the wear characteristics of Ti alloys (Pure Ti, Ti-6Al-4V, Ti-5Al-2.5Sn) fabricated by centrifugal precision casting in an Ohara dental titanium casting machine. It was found that the hardness of the surface region is higher than that of the interior region. It is considered that the oxygen adsorption in the surface region during casting, leads to the interstitial solid solution hardening. Wear resistance incerases in the order of pure Ti, Ti-6Al-4V, Ti-5Al-2.5Sn alloys. The interior hardness value increases in the same order. The specific wear rate increases with applied load and increases monotonously with sliding speed. The Fe transfer from the counterpart material was observed on the worn surface of the Ti-5Al-2.5Sn alloy. Oxidative wear occurs at low sliding speeds and mechanical fracture wear occurs at high sliding speeds.

• Tribology and Lubricants
• /
• v.25 no.1
• /
• pp.66-72
• /
• 2009

Al-based composites reinforced with SiC particulate were fabricated using a thermal spray process, and dry sliding wear behavior of the composites was investigated. Pre-mixed Al and SiC powders were sprayed on an A16061 substrate by flame spraying, and dry sliding wear test were performed under various sliding speed and applied load conditions against ${Al_2}{O_3}$ ball. Wear behavior of the composites was studied by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). And build-up mechanism of MML on the worn surface of the composites was examined. It was revealed that these MML was formed of debris from the contact surface of the composites and effected to wear behavior of the composites protecting the contact surface of the composites.

• Elastomers and Composites
• /
• v.55 no.4
• /
• pp.339-346
• /
• 2020

We functionalized a wear-resistant carbon-based MoS2 filler to solve its limited wear condition problem. The filler exhibits excellent lubricative properties. The surface modification of MoS2 was carried out using a (3-glycidyloxypropyl)trimethoxysilane (GPTMS) silane coupling agent to improve the low compatibility and dispersibility of the filler that generally degrade the performance of composites. A silane coupling agent was employed for the functionalization of MoS2, and its effect on the wear resistance of MoS2/Polyamide-6,6 was investigated. The silanization of MoS2 was identified by contact angle analysis and Fourier-transform infrared, energy dispersive X-ray, and X-ray photoelectron spectroscopies. The wear resistance of the composite was found to be improved significantly by the surface functionalization of MoS2.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.357-361
• /
• 1997

In this work surface damage of head and disk of head disk drive was analysed using an Atomic Force Microscpoe. The initial damage of the disk occurred by generation of extermely small wear particles. Also it was show that wear particles tend to pile up near the front side of the slider. The surface damage mechanism of drag test and contact-start-stop test was found to be quite similar.