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Modeling friction between shearing brittle surfaces with a discrete element method

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Authors
Kiiskinen, Sampsa
Date
2018
Discipline
FysiikkaPhysics

 
Hauraiden materiaalien murtuminen on eräs materiaalifysiikan peruskysymyksistä. Sille ei ole vieläkään olemassa täydellistä teoreettista selitystä, joten ennusteiden tekeminen nojaa vahvasti kokeisiin ja niihin perustuviin numeerisiin malleihin. Tässä työssä suunnittelemme ja toteutamme diskreettielementtimenetelmän sellaisen fysikaalisen systeemin tutkimiseen, jossa kaksi haurasta pintaa leikkaavat toisiaan. Keskitymme erityisesti siihen kuinka erilaiset voimamallit sisäiselle kitkalle vaikuttavat materiaalin ulkoiseen kitkaan. Käyttämällä graniittia koemateriaalina huomaamme, että sen ulkoinen kitka riippuu voimakkaasti sen sisäisestä kitkasta, kun ulkoinen paine on lähellä materiaalin puristuslujuutta. Muutoin ulkoisen kitkan määräävät pääasiallisesti leikkauspintojen karkeus tai niiden väliin muodostuneen sirpalekerroksen paksuus. Toisaalta, riippumatta ulkoisesta paineesta, sisäinen kitka vaikuttaa voimakkaasti sirpalekerroksen sisäiseen mekaniikkaan.
 
The fracture of brittle materials is a fundamental problem in material physics. It still lacks a complete theoretical description, so making predictions relies heavily on experiments and numerical models based on them. In this work we design and implement a discrete element method to study the physical system of two brittle surfaces as they are sheared across each other. Our focus is specifically how different force models for internal friction affect the dry friction of the material. By using granite as our reference material, we find that the dry friction depends strongly on the internal friction when the pressure is around the ultimate strength of the material. Otherwise the dry friction is primarily determined by the roughness of the surfaces or the thickness of the fragment layer between the them. Still, regardless of the pressure, the presence of internal friction strongly influences the mechanics inside the fragment layer.
 
Keywords
material physics geophysics computational physics discrete element methods geofysiikka
URI

http://urn.fi/URN:NBN:fi:jyu-201803271855

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