• Tribology and Lubricants
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• v.11 no.5
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• pp.31-39
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• 1995

The surface integrity of a machined surface is an important factor that dictates several performance characteristics of a metal part. In this paper, the surface integrity aspects are presented specifically with respect to the tribological properties of steel. Test specimens were prepared under varying conditions to induce different levels of surface deformation and hardness. Sliding and rolling experiments were performed to assess the friction and wear characteristics of these specimens using a pinon-disk type tribotester and a plate-on-ball type set-up. It is reaffirmed that heat treated steels possess superior sliding and rolling fatigue resistance than raw steel. However, for the case of raw steels machined under varying conditions, the harder specimen resulted in higher wear. This result is attributed to the presence of surface cracks that were induced during machining. The results of such findings will aid in the optimization of surface preparation process for tribological applications of steel.

• Tribology and Lubricants
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• v.11 no.5
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• pp.144-149
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• 1995

Use of high-quality basestocks is increasing to produce high-performance lubricants. However, their tribological characteristics have not been understood clearly yet. In this study, a newly developed basestock from a fuel hydrocracker and a poly-alpha-olefin are selected and investigated on the properties of lubricants formulated with them. The Lubricants are prepared by blending the basestocks with typical additives such as a zinc dialkyldithiophosphate, a dispersant, a detergent and a dispersant-inhibitor package. Frictional and wear-preventing properties are investigated using an oscillating-type wear-testing machine. The contact is a ball-on-disk mode and the testing temperature is varied from room temperature to 200$^{\circ}$C. The results show that their frictional property is varied significantly and that the non-conventional oils result in lower friction and lower wear compared with conventional lubricants, especially at the higher temperatures.

• Tribology and Lubricants
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• v.11 no.5
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• pp.55-58
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• 1995

The effects of Ni contents in Cu base sintered friction material were studied. The contents of Ni were increased up to 9 wt% in the Cu-Sn matrix. The microstincture and tribological behavior of the friction material were examined. Pin on disk type of constant speed friction test rig were used to measure the friction and the wear rates. The results show that Ni addition increased the friction coefficients and decreased the wear rates of the materials. Relations between microhardness of the matrix and friction properties have been discussed. In addition optimum Ni content is recommended through the analysis of wear debris.

• Tribology and Lubricants
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• v.24 no.6
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• pp.338-342
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• 2008

Tensile test results using three kinds of steel structure specimens are measured and compared. Slip coefficient between shot blasted steel plates was greater than 0.6. For the case of the plates coated with Super zinc, it revealed that the coefficients were greater than 0.5. On the other hand, Super epoxy coating decreased its slip coefficient less than 0.25. Steel plates coated with Super zinc are proved to be practically applicable to the steel structures with anti-corrosion characteristics and clean surfaces.

• Tribology and Lubricants
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• v.25 no.3
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• pp.171-175
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• 2009

One of the critical issues associated with the 40mm long hollow cylinder's development and maintenance is the prediction of cylinder erosion. The actual firing test is the most accurate method to measure the cylinder erosion rate. But it costs a great deal and requires a long measurement time. Hence many empirical methods have been proposed to predict the erosion rate and life span of long hollow cylinders. An EFC formula is calculated. An approximate erosion formula for the ammunition type A is derived to interpolate 16 observation values up to 4,000 rounds. A new erosion equation and muzzle velocity formula are also suggested. Several numerical results are presented.

• Tribology and Lubricants
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• v.25 no.4
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• pp.265-269
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• 2009

The wear of the contact in the tappet accounts for the greatest portion of entire friction loss of an engine, leading to the occurrence of abnormal wear. The coated specimens for earn-tappet wear test were producted by using PVD-Sputtering coating method. It examined the friction characteristics occurring between the earn and the tappet by using the dedicated wear tester and found that the friction torque value was reduced through comparison testing with the existing part when the low friction coating was applied. So application of the low friction coating to actual vehicles will reduce the fuel economy and occurrence of noise-vibration.

• KSTLE International Journal
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• v.9 no.1_2
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• pp.31-35
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• 2008

DLC (Diamond Like Carbon) films have predominant tribological properties like a high hardness, low friction and high chemical resistance; therefore, DLC films are applied in a wide range of industrial fields. This paper evaluated the characteristics of DLC films deposited on bearing steel with different hardness by RF-PECVD (Radio Frequency - Plasma Enhanced Chemical Vapor Deposition) method. Si-interlayer was deposited on bearing steel to improve adhesion strength by RF-Sputtering method. The DLC film structures were analyzed with Raman spectra and Gaussian function. Adhesion strength of DLC films was measured with a scratch tester. Friction and wear test were carried out with a ball-on -disc type to investigate the tribological characteristics. Experimental results showed that DLC films deposited on bearing steel under same deposition condition have typical structure DLC films regardless of hardness of bearing steel. Adhesion strength of DLC film is increased with a hardness of bearing steel. Friction coefficient of DLC film showed lower at the high hardness of bearing steel.

• KSTLE International Journal
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• v.9 no.1_2
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• pp.10-12
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• 2008

Silicon micro-patterns were fabricated on Si (100) wafers using photolithography and DRIE (Deep Reactive Ion Etching) fabrication techniques. The patterned shapes included micro-pillars and micro-channels. After the fabrication of the patterns, the patterned surfaces were chemically modified by coating Z-DOL (perfluoropolyether, PFPE) thin films. The surfaces were then evaluated for their micro-friction behavior in comparison with those of bare Si (100) flat, Z-DOL coated Si (100) flat and uncoated Si patterns. Experimental results showed that the chemically treated (Z-DOL coated) patterned surfaces exhibited the lowest values of coefficient of friction when compared to the rest of the test materials. The results indicate that a combination of both the topographical and chemical modification is very effective in reducing the friction property. Combined surface treatments such as these could be useful for tribological applications in miniaturized devices such as Micro/Nano-Electro-Mechanical-Systems (MEMS/NEMS).

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.50-55
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• 2003

Tribological testing of DLC films was conducted using a rotating type ball on a disk friction tester in a dry chamber. This study made use of four kinds of mating balls that were made with stainless steel but subjected to diverse annealing conditions in order to achieve different levels of hardness. In all load conditions using martensite mating balls, the test results demonstrated that the friction coefficient was lower when the mating materials were harder. The high friction coefficient found in soft martensite balls appeared to be caused by the larger contact areas. The wear track on the mating balls indicated that a certain amount of material transfer occurs from the DLC film to the mating ball during the high friction process. Raman Spectra analysis showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.

• Tribology and Lubricants
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• v.18 no.2
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• pp.147-152
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• 2002

The morphological analysis of wear particle is a very effective means fur machine condition monitoring and fault diagnosis. In order to describe morphology of various wear particle, the wear test was carried out under friction experimental conditions. And fractal descriptors was applied to boundary and surface of wear particle with image processing. These descriptors to analyze shape and surface of wear particle are shape fractal dimension and surface fractal dimension. The boundary fractal dimension can be derived from the boundary profile and surface fractal dimension can be determined by sum of intensity difference of surface pixel. The morphology of wear particles can be effectively obtained by two fractal parameter.