• Composites Research
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• v.13 no.4
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• pp.11-18
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• 2000

This study is mainly concerned with friction and wear properties for the piston ring of non-lubricating air compressor which made of PTFE-polyimide composites. At the PTFE and polyimide alone mixture specimens, PTFE80%-polyimide20%, which shows the lowest mean friction coefficient and specific wear rate at 0.94m/s sliding speed. In case of the specific wear rate, copper30% specimen shows the lowest value of 2.537-5(mm3/Nm) in all specimens. It considered that the friction coefficient is affected by generating speed and quantity of wear film. In case specific wear rate, it is attributed to the fact that the surface hardness of wear film is proportioned to specific wear rate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.245-250
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• 2003

This research conducted milling tests to study effects of cutting environment conditions of ball end mills on the characteristics of hard milling process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAIN coated were utilized in the cutting tests. Dry cutting without coolant and semi-dry cutting using botanical oil coolant were conducted and MQL (Minimum Quantity Lubricant) device was used to spray coolant. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that dry cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than MQL spray cutting did.

• Transactions of Materials Processing
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• v.13 no.1
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• pp.45-52
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• 2004

This research conducted milling tests to study effects of cutting environment conditions of ball end mills on the characteristics of hard milling process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAlN coated were utilized in the cutting tests. Dry cutting without coolant and semi-dry cutting using botanical oil coolant were conducted and MQL(Minimum Quantity Lubricant) device was used to spray coolant. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that dry cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than MQL spray cutting did.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1010-1015
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• 2008

The rapid wear rate of cutting tools due to high cutting temperature is a critical problem to be solved in machining of hardened steel. Application of cutting fluid influences the performance of machining because of its lubrication and cooling actions. But, the environmental concerns call for the reduced use of cutting fluids in machining operations. Near-dry machining such as minimum quantity lubrication is regarded as one of the solutions to this difficulty. In the present work, cutting fluid was applied as a high velocity jet at the machining zone continuously at an extreme low rate using a fluid application system developed namely Electro Static Lubrication (ESL) during drilling of hardened steel. The performance of ESL has been compared with that of dry and MQL (minimum quantity lubrication) machining.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.238-244
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• 2004

This research conducted milling tests to study effects of cutting environment conditions of ball end milts on the characteristics of high speed milling cutting process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAIN coated were utilized in the cutting tests. Dry cutting without coolant and semidry cutting using botanical oil coolant by the MQL(Minimum Quantity Lubricant) device were conducted. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that MQL spray cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than dry cutting did.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.105-113
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• 2001

The effect of silver particle introduction on the rolling friction of AISI 52100 steel pairs has been investigated. Experiments were performed in dry conditions using a thrust bearing-type rolling test rig at a load range of 12 - 960 N and a sliding velocity range of 8 - 785 mm/sec with pure(99.99%) silver particles. Results showed that the introduced silver particles formed transfer layer, which protected virgin bearing surfaces and resulted in low rolling friction. By changing the quantity of silver particles, transitions in the rolling friction wear found. Results also showed that the variations in normal load and rolling speed also affected the rolling friction behavior. Analyses using SEM and EPMA showed that tile formation of transfer layer was mainly governed by the silver particle quantity, normal load and rolling speed, and this resulted in the different behavior of rolling friction. In this study, it was found that the low and stable rolling friction was resulted from the shakedown phenomena occurred at the silver transfer layer.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.968-973
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• 2003

As environmental restrictions have continuously become more strict, it has emphasized development of environment-friendly technologies. In cutting technology, it has been well recognized that cutting fluids might have undesirable effects on worker's health and working environment and, hence, recently there have been numerous attempts to minimize harmful effects of cutting fluids on environments. To minimize the use of cutting fluids in machining, conventional cutting fluids have been replaced with the technologies of pressurized cold air and minimum quantity lubrication(MQL). Compared with milling, turning is a continuous cutting process, where tools are continuously heated up and lack of lubricity could lead to tool wear and deteriorated surface roughness. In this study, it has been investigated how tool wear and surface roughness could be affected by cutting conditions, supply and cooling methods. The experimental results show that MQL technology is able to minimize harmful effects of conventional cutting fluids.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.221-226
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• 2002

As environmental restriction has continuously become more strict, machining technology has emphasized on development of environment-friendly technologies. In cutting technology, it has been well recognized that cutting fluids might have undesirable effects on workers health and working environment and, hence, recently there have been numerous attempts to minimize harmful effects of cutting fluids on environments. To minimize the use of cutting fluids in machining, conventional cutting fluids have been replaced with the technologies of pressurized cold air and minimum quantity lubrication (MQL). Compared with milling, turning is continuous cutting process, where tools are continuously heated up and lack of lubricity could lead to tool wear and deteriorated surface roughness. In this work, it has been investigated how tool wear and surface roughness could be affected by cutting conditions, supply and cooling methods. The experimental results show that MQL technology is able to minimize conventional cutting fluids.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.453-459
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• 2002

In this paper. the correlation among vibration. wear and temperature are experimentally investigated when rubbing is caused by static and dynamic forces. Each measurement reflects the characteristics of the system and is useful in detecting and diagnosing the current status of rotating machinery. For experiment, the rotor system with lubricating equipment such as trochoid pump, oil tank and wear detecting sensor is implemented to simulate the rubbing condition. Experimental results show that significant change in wear quantity can be notified when vibration signal is changed by rubbing. The results can be applied to system monitoring and fault diagnosis in rotating machinery.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.1069-1075
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• 1994

When ceramics are used as the parts of an engine and a machine, the tribological properties are very important. For the preparation of the resistance material for wear applications by the method of Reaction-Bonded Sintering, metal silicon and carbon black are mixed up into SiC powder, and Al2O3 and Fe2O3 are put as an additive. As the general properties, the bending strength and water absortion are measured in the normal temperature and the phase changies are investigated with XRD. The property of the resistance for wear applications is measured with the amount of friction and wear, friction coefficient and maximum asperties. And, the surface of wear is observed with SEM. With the results of this study, the optimal mol ratio of Si : C and the suitable quantity of the mixture of SiC are 7 : 3 and 40 wt%, respectively. In the case of the addition of Al2O3 (2 wt%), the resistance for friction and wear applications is prominent. The bending strength showed the highest peak when Al2O3 (4 wt%) and Fe2O3 (4 wt%) were added. The properties of friction and wear were related with the propagation velocity of crack rather than the bending strength.