{"title":"Friction Properties of Journal-bearing-like Conformal Contacts in Microgravity Environment","authors":"Shujia Wan, Bing Han, Li He, Ruiting Tong, Jingyan Wang, Baobao Qiang, Menghe Zhou","doi":"10.1007/s12217-024-10096-x","DOIUrl":null,"url":null,"abstract":"<div><p>Friction is a primary failure mode in micro-nano electromechanical systems due to the high surface-to-volume ratio. Microgravity further complicates this issue in journal-bearing-like conformal contacts by promoting irregular disturbances. This paper aims to gain insights into the anti-friction design of journal-bearing-like devices through molecular dynamics simulation. A molecular dynamics model was proposed and the calculation method of the friction force was derived. In the absence of disturbance, the proposed model was compared with a non-conformal model which unfolded the bearing as a plane, and the influence of initial radial clearance and axis inclination on the friction force was investigated. The results showed that the proposed model could present more accurate friction forces than the non-conformal model. The friction force was inversely proportional to the initial clearance, and the axis inclination could reduce the friction force. Regarding disturbances as the superposition of two vibrations perpendicular to each other, in which case the trajectory of the journal was a Lissajous curve, the effects of frequency, stiffness coefficient, amplitude ratio, and frequency ratio were investigated. The results showed that the average friction force increased with the rising frequency in the range of 0.8 ~ 4.8 GHz, then decreased with the further increase of frequency. The average friction force was lowered when the stiffness coefficient increased from 100N/m to 1000N/m. For two representative frequencies, the average friction force exhibited different trends with the amplitude ratio. Except for the case of 1.25, increasing the frequency ratio could reduce the friction force. It seemed that applying a well-designed Lissajous route was a promising way to reduce friction.</p></div>","PeriodicalId":707,"journal":{"name":"Microgravity Science and Technology","volume":"36 2","pages":""},"PeriodicalIF":1.3000,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Microgravity Science and Technology","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s12217-024-10096-x","RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, AEROSPACE","Score":null,"Total":0}
引用次数: 0
Abstract
Friction is a primary failure mode in micro-nano electromechanical systems due to the high surface-to-volume ratio. Microgravity further complicates this issue in journal-bearing-like conformal contacts by promoting irregular disturbances. This paper aims to gain insights into the anti-friction design of journal-bearing-like devices through molecular dynamics simulation. A molecular dynamics model was proposed and the calculation method of the friction force was derived. In the absence of disturbance, the proposed model was compared with a non-conformal model which unfolded the bearing as a plane, and the influence of initial radial clearance and axis inclination on the friction force was investigated. The results showed that the proposed model could present more accurate friction forces than the non-conformal model. The friction force was inversely proportional to the initial clearance, and the axis inclination could reduce the friction force. Regarding disturbances as the superposition of two vibrations perpendicular to each other, in which case the trajectory of the journal was a Lissajous curve, the effects of frequency, stiffness coefficient, amplitude ratio, and frequency ratio were investigated. The results showed that the average friction force increased with the rising frequency in the range of 0.8 ~ 4.8 GHz, then decreased with the further increase of frequency. The average friction force was lowered when the stiffness coefficient increased from 100N/m to 1000N/m. For two representative frequencies, the average friction force exhibited different trends with the amplitude ratio. Except for the case of 1.25, increasing the frequency ratio could reduce the friction force. It seemed that applying a well-designed Lissajous route was a promising way to reduce friction.
期刊介绍:
Microgravity Science and Technology – An International Journal for Microgravity and Space Exploration Related Research is a is a peer-reviewed scientific journal concerned with all topics, experimental as well as theoretical, related to research carried out under conditions of altered gravity.
Microgravity Science and Technology publishes papers dealing with studies performed on and prepared for platforms that provide real microgravity conditions (such as drop towers, parabolic flights, sounding rockets, reentry capsules and orbiting platforms), and on ground-based facilities aiming to simulate microgravity conditions on earth (such as levitrons, clinostats, random positioning machines, bed rest facilities, and micro-scale or neutral buoyancy facilities) or providing artificial gravity conditions (such as centrifuges).
Data from preparatory tests, hardware and instrumentation developments, lessons learnt as well as theoretical gravity-related considerations are welcome. Included science disciplines with gravity-related topics are:
− materials science
− fluid mechanics
− process engineering
− physics
− chemistry
− heat and mass transfer
− gravitational biology
− radiation biology
− exobiology and astrobiology
− human physiology