Theoretical Study on Touchdown Vibration of Subnanometer Flying Head Slider and Molecularly Thin Liquid Film Lubrication

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06039
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Design engineering/Machine functional elements/Tribology
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Ono Kyosuke 東京工業大学, 工学院, 名誉教授 (40152524)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: ヘッド・ディスクインタフェース / 表面力 / 分子間力 / ヘッドタッチダウン / 分離圧式 / 希薄液膜拡散方程式 / 弾性メニスカス接触理論 / 高粘度境界潤滑方程式

Outline of Final Research Achievements

By measuring the surface textures of magnetic disk and considering the vdW force of Diamond-like-carbon layer, bonded and mobile lubericant layers, and asperity meniscus force, I established a theory of surface force between head and disk surface. Then, by using this surface force, I analyzed microwaviness (MW)-excited vibration of the head slider during touchdown and found that the experimental complex touchdown behaviors are caused by the MW-excited vibration in relation to the static instability of surface force. Next I derived the strict disjoining pressure equation by integrating molecular forces based on Rennard-Jones potential. Then by using the strict disjoining pressure, I newly derived rigorous diffusion equation for sub-monolayer and multi-layer liquid films. The validity of sub-monolayer diffusion equation was confirmed by experimental data. Moreover, as an extension of this thery, I developed a new Reynolds equation used for high viscosity boundary layer lubrication.

Free Research Field

機械力学，トライボロジー

Academic Significance and Societal Importance of the Research Achievements

磁気ディスク装置の浮上ヘッド・ディスク間すきまは分子間引力が支配する1 nm以下になっており，分子間力を考慮した解析理論が必要である．本研究により，近接・接触二面間の表面力を定量的に評価できる統計的な力学理論を確立すると共に，これによりヘッドスライダの近接・接触時の動的現象を始めて理論的に明らかにした．また従来経験的に用いられてきた液膜と固体面との引力式やこれに基づく液膜の拡散現象に関する厳密理論を確立し，分子間力に起因する現象を連続体力学で効率よく評価できることを始めて明らかにした．さらに従来から実験的に評価されてきた添加剤による境界潤滑機構を理論的に評価できる潤滑方程式を開発した．