{"title":"摩擦动力学:滑动摩擦时的位移波动。","authors":"R. Xu, F. Zhou and B. N. J. Persson","doi":"10.1039/D5SM00617A","DOIUrl":null,"url":null,"abstract":"<p >We have investigated the fluctuations (noise) in the positions of rectangular blocks, made from rubber or polymethyl methacrylate (PMMA), sliding on various substrates under constant driving forces. For all systems the power spectra of the noise exhibit large low-frequency regions with power laws, <em>ω</em><small><sup>−<em>γ</em></sup></small>, with the exponents <em>γ</em> between 4 and 5. The experimental results are compared to simulations and analytical predictions using three models of interfacial interaction: a spring-block model, an asperity-force model, and a wear-particle model. In the spring-block model, small sub-blocks (representing asperity contact regions) are connected to a larger block <em>via</em> viscoelastic springs and interact with the substrate through forces that fluctuate randomly in both time and magnitude. This model gives a power law with <em>γ</em> = 4, as also observed in experiments when no wear particles can be observed. The asperity-force model assumes a smooth block sliding over a randomly rough substrate, where the force acting on the block fluctuates in time because of fluctuations in the number and size of contact regions. This model predicts a power law with the exponent <em>γ</em> = 6, which disagrees with the experiments. We attribute this discrepancy to the neglect of load redistribution among asperity contacts as they form or disappear. The wear-particle model considers the irregular dynamics of wear particles of varying sizes moving at the interface. This model also predicts power-law power spectra but the exponent depends on two trapping-release probability distributions. If chosen suitably it can reproduce the exponent <em>γ</em> = 5 (which corresponds to 1/<em>f</em> noise in the friction force) observed in some cases.</p>","PeriodicalId":103,"journal":{"name":"Soft Matter","volume":" 39","pages":" 7594-7609"},"PeriodicalIF":2.8000,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/sm/d5sm00617a?page=search","citationCount":"0","resultStr":"{\"title\":\"Friction dynamics: displacement fluctuations during sliding friction\",\"authors\":\"R. Xu, F. Zhou and B. N. J. Persson\",\"doi\":\"10.1039/D5SM00617A\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p >We have investigated the fluctuations (noise) in the positions of rectangular blocks, made from rubber or polymethyl methacrylate (PMMA), sliding on various substrates under constant driving forces. For all systems the power spectra of the noise exhibit large low-frequency regions with power laws, <em>ω</em><small><sup>−<em>γ</em></sup></small>, with the exponents <em>γ</em> between 4 and 5. The experimental results are compared to simulations and analytical predictions using three models of interfacial interaction: a spring-block model, an asperity-force model, and a wear-particle model. In the spring-block model, small sub-blocks (representing asperity contact regions) are connected to a larger block <em>via</em> viscoelastic springs and interact with the substrate through forces that fluctuate randomly in both time and magnitude. This model gives a power law with <em>γ</em> = 4, as also observed in experiments when no wear particles can be observed. The asperity-force model assumes a smooth block sliding over a randomly rough substrate, where the force acting on the block fluctuates in time because of fluctuations in the number and size of contact regions. This model predicts a power law with the exponent <em>γ</em> = 6, which disagrees with the experiments. We attribute this discrepancy to the neglect of load redistribution among asperity contacts as they form or disappear. The wear-particle model considers the irregular dynamics of wear particles of varying sizes moving at the interface. This model also predicts power-law power spectra but the exponent depends on two trapping-release probability distributions. If chosen suitably it can reproduce the exponent <em>γ</em> = 5 (which corresponds to 1/<em>f</em> noise in the friction force) observed in some cases.</p>\",\"PeriodicalId\":103,\"journal\":{\"name\":\"Soft Matter\",\"volume\":\" 39\",\"pages\":\" 7594-7609\"},\"PeriodicalIF\":2.8000,\"publicationDate\":\"2025-08-05\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://pubs.rsc.org/en/content/articlepdf/2025/sm/d5sm00617a?page=search\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Soft Matter\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://pubs.rsc.org/en/content/articlelanding/2025/sm/d5sm00617a\",\"RegionNum\":3,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"CHEMISTRY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Soft Matter","FirstCategoryId":"92","ListUrlMain":"https://pubs.rsc.org/en/content/articlelanding/2025/sm/d5sm00617a","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
Friction dynamics: displacement fluctuations during sliding friction
We have investigated the fluctuations (noise) in the positions of rectangular blocks, made from rubber or polymethyl methacrylate (PMMA), sliding on various substrates under constant driving forces. For all systems the power spectra of the noise exhibit large low-frequency regions with power laws, ω−γ, with the exponents γ between 4 and 5. The experimental results are compared to simulations and analytical predictions using three models of interfacial interaction: a spring-block model, an asperity-force model, and a wear-particle model. In the spring-block model, small sub-blocks (representing asperity contact regions) are connected to a larger block via viscoelastic springs and interact with the substrate through forces that fluctuate randomly in both time and magnitude. This model gives a power law with γ = 4, as also observed in experiments when no wear particles can be observed. The asperity-force model assumes a smooth block sliding over a randomly rough substrate, where the force acting on the block fluctuates in time because of fluctuations in the number and size of contact regions. This model predicts a power law with the exponent γ = 6, which disagrees with the experiments. We attribute this discrepancy to the neglect of load redistribution among asperity contacts as they form or disappear. The wear-particle model considers the irregular dynamics of wear particles of varying sizes moving at the interface. This model also predicts power-law power spectra but the exponent depends on two trapping-release probability distributions. If chosen suitably it can reproduce the exponent γ = 5 (which corresponds to 1/f noise in the friction force) observed in some cases.
期刊介绍:
Soft Matter is an international journal published by the Royal Society of Chemistry using Engineering-Materials Science: A Synthesis as its research focus. It publishes original research articles, review articles, and synthesis articles related to this field, reporting the latest discoveries in the relevant theoretical, practical, and applied disciplines in a timely manner, and aims to promote the rapid exchange of scientific information in this subject area. The journal is an open access journal. The journal is an open access journal and has not been placed on the alert list in the last three years.