The fracture of the atomic-scale contact should be investigated for understanding the mechanism of the mechanical processing. Using a combination of the scanning probe microscope (SPM) with possible high space resolution and the acoustic emission (AE) with high sensitivity for fracture is one of the possible way of investigating the fracture mechanism. When using the SPM, the AE signal might be detected with receiving the AE wave by the piezoelectric tube scanner of the SPM receiving the AE wave, where by the piezoelectric effect the electric signal due to the AE wave is superimposed on the scan signal. Based on that, in this study, a novel method to detect AE signal from the scan signal is proposed. With this method, without changing the SPM body, the AE could be detected, and a two-dimensional AE source location could be possible by using four divided electrodes of the piezoelectric tube scanner. By a simple experiment using the AE wave simulator, the AE signal seems to be detected by the piezoelectric scanner of the SPM. Also, one of the typical data from the experiment suggests the AE source location might be possible. In the experiment of the indentation using atomic force microscope (AFM), which is one of the SPM, the AE signal is observed reproducibly.

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The present study investigated friction and wear of polyetheretherketone (PEEK) resin filled with Rice Bran (RB) ceramics particles (PEEK/RBC composites) under water lubricated condition. RB ceramics particles with mean diameter of 3 μm were compounded with PEEK resin. Mass fraction of RB ceramics particles α was 10, 20, 30, and 40 mass%. As a comparison, monolithic PEEK resin and RB ceramics were prepared. Ball on disk friction testing was carried out using an austenitic stainless steel (JIS SUS304) ball with a diameter of 8 mm under water lubricated condition. Sliding velocity ranged from 0.1 m/s to 2.0 m/s, and normal load ranged from 0.98 N to 9.8 N. PEEK/RBC composites (α = 10-40 mass%) showed significantly lower friction coefficient and specific wear rate under a wide range of normal load and sliding velocity conditions as compared with monolithic PEEK and RB ceramics. It was suggested on the basis of sliding surface observation and surface roughness analysis that the low friction was achieved for PEEK/RBC composites due to an increased hydrodynamic lubrication effect compared with monolithic PEEK and RB ceramics.

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Volume and issue: Vol.11, No.1 (2016)
Page: pp.13-23
Title: Improvement in Mixed Lubrication Characteristics of Electromagnetic Clutch Coated with DLC-Si Film by Controlling Surface Roughness and Providing Micro-groove
Author(s): Junji Ando, Takeshi Yamaguchi and Kazuo Hokkirigawa

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Measuring and estimating the traction coefficient is necessary to improve transmitting efficiency and design compact, lightweight toroidal continuously variable transmissions (T-CVTs). However, few attempts have been made to measure and estimate the traction coefficient of T-CVTs under practical usage conditions, and the design of T-CVTs has used extrapolated values from traction coefficients measured under low-power conditions. Therefore, we developed a high-power two-roller traction tester to clarify variation trends in traction curves under operating conditions similar to a T-CVT. The results showed a nearly linear relation between the maximum traction coefficient and the roller surface temperature. Furthermore, the change rate of the maximum traction coefficient with respect to roller surface temperature was dependent on the maximum contact pressure. This paper also compares several traction models under practical operating conditions. A viscoelastoplastic model was constructed and compared with a conventional elastoplastic model. In a wide range of operating conditions, the viscoelastoplastic model showed small differences in the maximum traction coefficient between measured and calculated curves compared with the elastoplastic model. The traction tester and the traction model contribute to building a traction curve database to make T-CVTs more compact, lightweight, and efficient.

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The tribological behavior of cast iron was investigated by sliding a disk against a bearing steel pin in ethanol, with and without oleic acid, using a pin-on-disk machine. The addition of oleic acid resulted in decreased friction in ethanol. The profile of the wear track was measured using a surface texture and contour measurement instrument. Microstructural observations and chemical analysis of the worn surface were performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The results indicated that mechanical wear such as plowing and adhesion occurred on the sliding surface of the cast iron in ethanol. In addition, galvanic corrosion was identified as a possible main cause for the removal of the cast iron material by sliding in ethanol with oleic acid.

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