Deep dent defects on the automobile parts produced by hot die forging have become problems because the dents were disadvantageous to the strength of these parts. The dents may have been probably caused by scales of hot billets. The behaviour of these thick scales in hot die forging was experimentally analyzed in this paper. The dents gradually grew bigger and changed the shapes every forging shot before the scales periodically transferred to the workpiece. The deep dent defects frequently formed at the part of the workpiece with large plastic deformation. Additionally, it was found the scales consisted of the oxide/non-oxide layers derived from the hot billet materials by microscope observation and electron probe micro analysis. It was estimated that the thicker scales were formed by layered pick-up and adhesion under severe tribological conditions. Adjusting preform shape and controlling lubrication were proposed to decrease the defects.
In the compressor housing of a turbocharger with oil mist atmosphere, soft semi-solid deposit could be observed even at the lower temperatures below 200°C. Sticky or hard deposit at higher temperatures above 300°C is well-known, which can be demonstrated by standard test such as the Panel Coker Test. However, the semi-solid deposit formation has not been reported and understood. In this research, the deposit in the compressor housing was analyzed and the formation mechanism was presumed basing on the composition of the deposit. To validate the presumption, the deposit formation was demonstrated using newly designed test method. Furthermore, the dependence of conditions on the formation and the countermeasure to prevent from deposit formation are also considered.
Hard solid deposit formation has been inevitable problem in marine use turbocharger, and many engineers have struggled with it for years. It is due to low quality fuel, and the deposit results in the deterioration of the performance. In addition, the deposit is hard so that it is difficult to be removed at periodical maintenance. However, hard solid deposit formation has not been reported and understood. In this study, the deposit in actual service turbocharger was analyzed, and the dependency of operation condition on the deposit formation was investigated. And the deposit formation was demonstrated using newly designed test method, vapor phase coking deposit evaluation test. Furthermore, the countermeasure to prevent from deposit formation is considered, and it was found the deposit formation is largely influenced by ingredient of metal.
Oil film thickness in rubber piston seals is measured by interferometry. Optimized optics and fluids enable clear interferograms. The oil film thickness on the contact area is measured during reciprocating motion. When the oil film formed on the contact area is sufficiently thick, monochromatic interferometry is applied to measure the variations in oil film profile. Under sealing condition, where the oil film is thin and even, the mean oil film thickness is measured by means of white light interferometry. The measurement results of oil film thickness correlate with the friction force.
The D-4OH adsorbed film structure is investigated as a function of film thickness and of molecular weight via surface energy measurements, terraced flow profiles, and ellipsometric imaging for film dewetting. The D-4OH monolayer thickness on a carbon surface exhibited a power law dependence on molecular weight, where the exponent was determined to be 0.70. With decreasing film thickness, the in-plane component of the radius of gyration, normalized to the bulk radius of gyration, increased to ~ 1.5, consistent with an ellipsoidal conformation on the carbon surface. Confinement effects increased with increasing molecular weight.
The Japanese Society of Tribologists is pleased to announce that the 2013 Paper Award of Tribology Online was awarded to:
“Effect of Environmental Gas on Surface Initiated Rolling Contact Fatigue,” by Hiroyoshi Tanaka, Tatsuhiko Morofuji, Kakeru Enami, Masaaki Hashimoto, Joichi Enami, Vol. 8, No. 1(2013) 90-96.
“Effects of Surface Chemical Properties on the Frictional Properties of Self-Assembled Monolayers Lubricated with Oleic Acid,” by Koji Miyake, Takamasa Kume, Miki Nakano, Atsushi Korenaga, Koji Takiwatari, Ryo Tsuboi, Shinya Sasaki, Vol. 7, No. 4 (2012) 218-224.
The Award Medals were presented to the authors by Prof. Masabumi Masuko, the President of the Japanese Society of Tribologists, at the JAST Annual Meeting on 20th May, 2014.
The Paper Award of Tribology Online is given annually to the author(s), either the JAST members or non-members, of the paper(s) judged as the best paper(s) published in Tribology Online (TROL) for the previous three years. All papers that appeared in TROL for the three years are reviewed by the JAST Awards Committee.
The aluminium matrix composites, particularly with hybrid reinforcements are the advanced materials that have been widely used as a substitute material in the transport sector, to manufacture lighter-weight and higher-performance components. As these components are often subjected to sliding wear under working conditions, therefore several of these applications require enhanced frictional and wear resistance. The purpose of the current review is therefore aimed at highlighting the focus of the current research scenario, in the field of tribological behaviour of aluminium based hybrid composites, to explore the materials for automotive applications. A significant experimental data has been reported in this area, and it has been revealed that the materials possessing high wear resistance are associated with formation of a stable tribolayer on the wear surface and the fine equiaxed wear debris. The operating variables such as applied load, sliding distance and sliding speed, temperature, wearing surface hardness, reinforcement contents and morphology have been found as critical parameters in relation to the wear regime, encountered by the material during operation. An attempt has been made to present and review the various aspects relevant to sliding wear behaviour of aluminium alloys and the hybrid composites, with different combinations of reinforcements. Further, it has been found that the cost and the weight of the aluminium matrix composites can be considerably controlled, by addition of hybrid reinforcements, without compromising the tribological properties.
The application of DLC coatings in the automotive industry has increased significantly both in terms of production volume and the kinds of applications involved. However, elucidation of the fundamental evaluation and mechanism of friction and wear properties for DLC coating are still far from sufficient level. This article discusses recent topics concerning the application of DLC coatings to automotive engine components and the related research for tribological issues of DLC coating. For the application to engine components, several typical examples are described. As an advanced one, the ta-C coated piston ring which has been applied recently to both the compression ring and the oil ring of a new mass-produced inline 3-cylinder compact gasoline engine is shown. The ta-C coated piston ring can reduce engine friction substantially compared with the conventional Cr plating ring. Additionally, the a-C:H coated aluminum piston which can be accomplished by shot-peening aluminum alloy substrate with fine tungsten particles shows exellent wear resistance. For the research, three issues of the super-low friction, the evaluation of adhesion strength and wear resistance and the rolling fatigue are discussed.