• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.79-86
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• 2000

The effects of recirculated exhaust gas on the wears of piston and piston rings were investigated by the experiment with a two-cylinder, four cycle, indirect injection diesel engine operating at an engine load of 75% and an engine speed of 1600 rpm. For the purpose of comparison between the wear rates of two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot contenets in exhaust emissions were removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors(A water injector has 144 nozzles of 1.0 mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out on the fuel injection timing fixed at 15.3$^{\circ}$ BTDC. It was found that the wear rate of piston skirt with EGR increased a little bit, but the piston head diameter increased, rather than decreased, owing to soot adhesion and erosion wear, and especially larger with EGR, and that the wear rates of the top and second piston ring(compression ring)thickness with EGR were more than twice the wear rate of top ring in case of no EGR, but the wear rate of oil rings thickness without EGR increased greater than that with EGR.

• Journal of the Korean Society for Heat Treatment
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• v.20 no.2
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• pp.72-77
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• 2007

Abrasive wear between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. Wear by abrasion are forms of wear caused by contact between a particle and solid material. Abrasive wear is the loss of material by the passage of hard particles over a surface. From the pin-on-disk test, particle dent test and scuffing test, abrasive wear characteristics of diesel engine cylinder liner-piston ring have been investigated. Pin-on-disk test results indicate that abrasive wear resistance is not simply related to the hardness of materials, but is influenced also by the microstructure, temperature, lubricity and micro- fracture properties. In particle dent test, dent resistance stress decreases with increasing temperature. From the scuffing test by using pin-on-disk tester, scuffing mechanisms for the soft coating and hard coating were proposed and experimentally confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1125-1131
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• 2009

O-rings are commonly used in machines as a seal. Due to prolonged use the surface of an O-ring can degrade which can lead to leakage as well as contamination. Damage of O-rings used in vacuum applications such as sputter is caused by various mechanisms. Particles detached from the O-ring may cause significant problems on the performance of the system in the vacuum chamber. Therefore, understanding the tribological behavior of O-rings is important to tackle the damage caused by repeated contact. In this work, FKM rubber was used for friction and wear tests conducted to investigate the tribological behavior of O-rings. A reciprocating type of a tribo-tester was used for the tests. The friction coefficient between the steel ball and the FKM specimen was quite high. Also, in order to identify the wear behavior, the surface of the FKM specimen was characterized using both optical and scanning electron microscopes. Evidence of wear due to adhesion and extrusion could be found. The results of this work will aid in improving the durability of O-rings.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.75-80
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• 2014

In previous study, make an attempt to estimate exhaust valve seat and seat-ring wear acceleration factor for engine durability test with measuring and consideration of wear mechanism. But found abnormal initial wear rate in exhaust valve seat-ring. And have to improve exhaust valve seat-ring wear rate for reliability reason, because next GDI/Turbo engine is based on this engine and GDI/Turbo engine have higher combustion pressure and higher thermal load. In this study, Trying to find the cause of abnormal wear factor, improve valve-train durability by change specification & design of parts and verify variant parts for improving durability of valve-train. And then I would like to propose a design guide line of valve-train system in a reliability point of view, besides make a complement of previous study.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.827-835
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• 1998

The effects of recirculated exhaust gas on the wear of cylinder liner piston and piston rings have been investigated by the experiment with a two-cylinder four cycle indirect injection diesel engine operating at 75% load and 1600 rpm speed For the purpose of comparison between the rates of two cylinders with and without EGR the recirculated exhaust gas is sucked into one of two cylinders after the soot among exhaust emissions is removed by an intntionally designed cylinder-type scrubber equipped with 6 water injectors(A water injector has 144 nozzles of 1.0 mm diame-ter) while only the fresh air into another cylinder. These experiments are carried out on the fuel injection at a fixed $15.3^{\circ}$ BTDC timing. It is found that firstly the mean wear amount of cylinder liner with EGR is more increased in the measurement positions of the second half than of the first half and the mean wear amount without EGR is almost uniform regardless of measurement posi-tions secondly the wear rates of the first and second piston ring(compression ring)thickness with EGR are more than twice but the wear rate of oil ring thickness without EGR is more increased than that with EGR and finally the wear rate of piston skirt with EGR is a little bit increased but the piston hed diameter is rather increased owing to soot adhesion and corrosion wear and espe-cially larger with EGR.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.89-102
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• 1993

In this experimental investigation, various plasma-sprayed zirconia contained coatings and a kind of alumina-zirconia coating were studied to gain a better understanding of their tribological behaviour under dry contact condition in a reciprocating motion at temperature of 200℃. Particular attention was made for finding appropriate coatings in cylinder liner/piston ring application with an emphasis on the antiwear property. In order to identify the wear mechanism, SEM(Scanning Electron Microscope), optical micrograph, and roughness tester were used. Alumina-zirconia and 8% yttria-zirconia were found to be most appropriate for the application to the cylinder liner/piston ring and, especially, alumina-zirconia exhibited highest wear-resistance and also showed good friction characteristics. Wear mechanisms of ceramic coatings identified.

• Tribology and Lubricants
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• v.11 no.5
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• pp.108-113
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• 1995

Wear and friction behavior of plasma-sprayed coatings in Mo- and Co-based alloy were studied for the application of piston-ring automobile engine. The plasma-sprayed coatings were varied with gun current density, gas flow, and distance. The surface roughness, microhardness, and wear volume were measured depending on the spray distances. The high temperature hardness value were also measured as a function of temperature. Ball-on-disc geometry configuration tribometer was utilized in air. The wear tests were performed in the temperature ranges from room temperature to 825$^{\circ}$C to investigate the tribological trend of the piston-ring materials in the lack of lubricant. The cross sections of wear track were investigated, using microscopy.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.766-771
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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 men friction coefficient and specific wear rate at 0.94m/s sliding speed. At each of carbon, copper and oxide lopper mixed with PTFE80%-polyimide20%. In case of copper10%, at 0.94m/s sliding speed, the mean friction coefficient shows 0.087, which is the lowest value in all specimens. In case of the specific wear rate, copper30% specimen shows the lowest value of $2.537E-5(mm^3/Nm)$ in all specimens.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.40-46
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• 2001

An integrated analysis for the thermo-elastic deformation, fatigue, wear and brittle damage evolution of the shrink-fitted die with multi stress-ring of dissimilar materials is presented. A simple numerical algorithm for the moving elastic boundaries characterizing the contacts of the insert and multi stress-rings is presented. The initial stress distribution in the die due to shrink-fit is considered and the traction at the die surface contacting with the work piece is obtained by analyzing the elasto-plastic deformation of work piece. Elastic analysis of the separate-type die is performed and then the evolution of brittle damage, wear and fatigue life are predicted. This integrated analysis is applied to the extrusion die with two layers of stress-rings and the results are discussed in detail.

• Tribology and Lubricants
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• v.22 no.6
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• pp.314-319
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• 2006

In this paper, the friction and wear characteristics of contact type sealing unit far a water turbine have been presented. The sealing unit for a small hydropower generation is to stop a leakage of circulating water from an outside of an impeller to an inside of a rolling bearing. The friction heating between a seal ring and a seal seat may radically increase a surface temperature in which increase a power loss and wear on the rubbing surface. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Victors hardness and the hardness of silicone carbide of SiC is 714.1 in Victors hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces are a dry friction, a water film friction and a mixed friction that is contaminated by a dust, silt, and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat in primary sealing unit. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components.