• Tribology and Lubricants
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• v.16 no.1
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• pp.1-8
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• 2000

Friction and wear tests have been performed on nylon, acetal resin, and PTFE (polytetrafluoroethylene), in reciprocating dry sliding conditions against steel discs. According to the results, acetal resin showed the lowest wear rates and PTFE exhibited the lowest friction coefficient. The prominent wear mechanisms found were adhesion and abrasion.

• Tribology and Lubricants
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• v.10 no.3
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• pp.29-38
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• 1994

The friction and wear of mild steel at dry sliding surfaces under different vacuum conditions have been investigated to understand the wear mechanisms. For the test, a ball-ondisk typed wear-rig has been built and implemented, allowing control of sliding speed, load and vacuum. Results show that, at a high sliding velocity, friction of low carbon steel (SS41) under a high vacuum is much higher than that of ambient condition and wear is much severer. It is due to lack of effective oxidation film formation on which steel surfaces could protect themselves against the severe wear. It has been shown, however, that there is a critical regime with contact conditions (at a low sliding velocity, a low load, and under a medium vacuum) at which effective, protective films of low carbon steel have been built on the surfaces in a friction process with a self-regulating way, resulting in both very low coefficients of friction (about 0.3) and mild wear. In order to investigate the protective films on steel surfaces, the worn surfaces and the wear debris have been experimentally analyzed with SEM, AES/SAM and XRD. A theoretical analysis of frictional heating at sliding surfaces, and an experimental analysis of the influence of oxidation wear under various vacuum conditions are described. The important variables on which self-formations of protective films at dry sliding surfaces depend, and the wear mechanisms are also investigated.

• Tribology and Lubricants
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• v.16 no.5
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• pp.324-331
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• 2000

Wear characteristics of Plastic and Nylon pinions against steel gear were studied to gain a better understanding of their tribological behaviors. Wear tests were conducted with power circulating gear test rig under dry contact conditions. Specific wear rates were measured as a function of applied load and the number of revolution. The worn teeth surfaces were examined with a profile projector and a camera. Nylon pinion showed lower specific wear rates than acetal pinion, but suffered teeth breakage under high load per unit tooth width. The dominant wear mechanisms found were adhesion and abrasion.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.2
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• pp.204-209
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• 2017

In order to use PUR/CuO Composites as the sealing materials for ships equipment, this research has been performed. PUR/CuO composites are produced by using ultrasonic waves. The increase of CuO leads to increase in the tensile strength and shore hardness. The cumulative wear volume shows a tendency to increase in proportional to sliding distance. As the CuO particles of these composites indicated, the friction coefficient was slightly increased. The major failure mechanisms were lapping layers, deformation of matrix, plowing, debonding of particles and microcracking by scanning electric microscopy photograph of the wear tested surface.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2052-2060
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• 2006

The wear of engine valve and seat insert is one of the most important factors which affect engine performance. Because of higher demands on performance and the increasing use of alternative fuel, engine valve and seat insert are challenged with greater wear problems than in the past. In order to solve the above problems, a simulator was developed to be able to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focuses on the different degrees of wear at three different singular test speeds (10 Hz, 25 Hz & multi-Hz). For this study, the temperature of the outer surface of the seat insert was controlled at 350$^{\circ}C$, and the test load was 1960 N. The test cycle number was $6.0{\times}10^6$. The mean ($\pm$standard error) wear depth of the valve at 10 Hz and 25 Hz was 45.1 ($\pm$3.7)$\mu$m and 81.7 ($\pm$2.5)$\mu$m, respectively. The mean wear depth of the seat insert at 10 Hz and 25 Hz was 52.7 ($\pm$3.9)$\mu$m and 91.2 ($\pm$2.7)$\mu$m, respectively. In the case of multi-Hz it was 70.7 ($\pm$2.4)$\mu$m and 77.4 ($\pm$3.8)$\mu$m, respectively. It was found that higher speed (25 Hz) cause a greater degree of wear than lower speed (10 Hz) under identical test condition (temperature, valve displacement, cycle number and test load). In the wear mechanisms of valves, adhesive wear, shear strain and abrasive wear could be observed. Also, in the wear mechanisms of seat inserts, adhesive wear, surface fatigue wear and abrasive wear could be observed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2581-2589
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• 2002

In this research, fretting tests were conducted in air to investigate the wear characteristics of fuel cladding materials with the fretting parameters such as normal load, slip amplitude, frequency and the number of cycles. A high frequency fretting wear tester was designed for this experiment by KAERI. After the experiments, the wear volume and the shape of wear contour were measured by the surface roughness tester. Tribologically transformed structures(TTS) were analysed by means of optical and scanning electron microscopes to identify the main wear mechanisms. The results of this study showed that the wear volume were increased with increasing slip amplitude, and the shape of wear contour was transformed V-type to W-type. Also, it was found that the critical slip amplitude was 168${\mu}{\textrm}{m}$. These phenomena mean that wear mechanism transformed partial slip to gross slip to accelerate wear volume. The wear depth increased with an increase of friction coefficient due to increase of normal load and frequency. The fretting wear mechanisms were believed that, after adhesion and surface plastic deformation occurred by relative sliding motion on the contact between two specimens, TTS creation was induced by surface strain hardening and wear debris were detached from the contact surface which were produced by the micro crack propagation and creation.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.540-547
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• 2001

This study has evaluated the wear behavior of PTA (Plasma Transferred Arc) Inconel 625 and Stellite 6 overlays on Nimonic 80A substrate. Nimonic 80A alloy was also included for comparison. In order to evaluate the wear performance, three-body abrasive wear test and pin-on-disk dry sliding wear test were performed. Microstructural development during the solidification of deposits is also discussed. Wear test results show that the wear rate of Stellite 6 deposit is lower than that of Inconel 625 deposit and Nimonic 80A. The sliding wear resistance of overlay deposits follows a similar trend to the abrasive wear resistance, but for Nimonic 80A. The main wear mechanisms were abrasive wear for Inconel 625 deposit, adhesive wear and delamination for Stellite 6 deposit in pin-on-disk dry sliding wear test and ploughing in three-body abrasive wear test. Cross sectional examinations of the worn surface of pin specimens after pin-on-disk dry sliding wear test implies that the plastic deformation near worn surface has occurred during the wear testing.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.124-130
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• 1998

The wear characteristics and wear mechanisms of dental composite resins were investigated. Composite resins such as Metalii, Silux Plus, Heliomolar and Palfique Estelite were selected as specimens and contents of filler in specimens in order to analyze the effect of Prepolymerized Particle Fillers in friction and wear characteristics. Ball on flat wear tester was used for a wear test. Friction and wear tests are carried out at room temperature. The friction coefficient of Metafil was quite high relatively, and the wear resistance of Silux Plus and Palfique Estelite was better than that of Metafil and Hellomolar at the same experimental condition. The main wear mechanism is plastic flow and abrasive wear by crack propagation.

• KSTLE International Journal
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• v.10 no.1_2
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• pp.27-32
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• 2009

In this study, fretting wear tests of nuclear fuel rods have been performed by using two kinds of spacer grid springs with a concave and a convex shape in room temperature dry and distilled water conditions. The objectives were to examine the variation of the wear mechanism with increasing fretting cycles and to evaluate the difference of the wear debris detachment behavior at each test environment. From the test results, the wear volume of each spring condition increased with increasing fretting cycles regardless of the test environments. However, the wear rate did not show a regular tendency and apparently changed with increasing fretting cycles. This is because the formation of the wear particle layer and/or the variation of the contact condition between the fuel rod and spring surfaces could affect a critical plastic deformation for detaching the wear debris. Based on the test results, the relationship between the wear behavior of each spring shape and test environment condition, and the variation of the surface characteristics are discussed in detail.

• Tribology and Lubricants
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• v.5 no.1
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• pp.36-43
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• 1989

Scanning electron microscopic observations were carried out on the worn surface and the wear debris of ceramic materials to investigate the wear mechanism of those in dry rolling contact. It was found from the scanning electron microscopic observations that the wear in ceramic materials is related to brittle fracture and has two types of wear mechanisms, small scale wear and larvae scare wear. Plate-like wear debris were created from the initial surface cracks and defects. The small scale wear was related to real contact area and large scale wear was related to HertzJan contact area. A wear model was proposed on the basis of scanning electron microscopic observations.