Starved elastohydrodynamically lubricated contact is described as deviation from fully flooded contact due to insufficient lubricant supply. This insufficiency causes thinner lubricant film compared to fully flooded regime. Thinner lubricant film means that rolling surfaces are closer together. Each surface has its own roughness, which is created by machining of the surface and is composed by many individual asperities. These asperities are elastically deformed while passing through the contact area of the EHL contact as well as whole contact surface. It is important to know the magnitude of the deformation. Especially in the starved contact where is increased risk of surface wear due to mutual contact of asperities on the opposite surfaces. This paper presents experimental work on the topic of the surface roughness deformation, which is passing by contact. Analytical method called amplitude attenuation theory was used to predict deformation of the artificial asperity (ridge) under starved conditions. Deformations provided by predictions were compared with the experiments and from both method is clear that roughness deformation is increasing with the progressing starvation - thinning the lubricant film. Magnitude of the deformation however depends on the asperity profile.

Volume and issue: Vol.11, No.2 (2016)

Page: pp.81‐87

Title: Development of a New Tapping Tool Covered with Nickel/Abrasive Particles Composite Film for Preventing Chip Snarling and Tool Service Life Extension

Author(s): Yasuyoshi Saito, Takeshi Yamaguchi, Kei Shibata, Yuki Kadota, Takeshi Kubo, Wataru Watanabe, and Kazuo Hokkirigawa

A new concept was proposed as biomimetic tribological (BMT) system by using three-dimensional (3D) printing process. The BMT had a lubricant supply path (LSP) beneath the sliding surface. The tribological properties could be actively controlled by directly supplying lubricant additives (anti-wear additive and friction modifier) alone to the sliding surface through the LSP during a friction process. To confirm the effectiveness of the LSP surface for improving the tribological performance under boundary lubrication, friction tests were conducted on a plate specimen with a lubricant supply path that was manufactured by a 3D metal printer. Experimental results suggest that the LSP surface system was more effective for friction reduction than a conventional system, and it offered an effective way to actively control the tribological performance under boundary lubrication.

We use a Cu/MoS₂ composite to provide a new approach to control the consolidation of materials by compression–shearing at room temperature. Cu/MoS₂ samples were formed under several shearing distances and the resulting microstructures were observed and compared with pure Cu samples. The microstructural change related to the decrease in applied shearing force is discussed. The structural observations indicate that the reason for the decrease in shearing force appears to be the slip of the sample on the lower plate because of MoS₂ lubrication. The internal structure of the Cu/MoS₂ samples appears to be interrupted midway through the consolidation process by dissipating the applied shearing force. In contrast, particle bonding and grain refinement occurred only on the sample surface, as for the friction process, and extended gradually to the inside of the sample when the shearing distance increased. We controlled the metal consolidation by compression shearing at room temperature by dispersing MoS₂ into a Cu matrix. The shearing force appears to be more effective in metal consolidation by compression shearing at room temperature than the shearing distance.