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UNDERSTANDING CONTACT MECHANICS AND FRICTION ON ROUGH SURFACES

Dalvi, Siddhesh Narayan
http://orcid.org/0000-0002-0527-3302
http://rave.ohiolink.edu/etdc/view?acc_num=akron158957808488289

Abstract Details

2020, Doctor of Philosophy, University of Akron, Polymer Science.
Understanding the mechanism of adhesion and friction in soft materials is critical to the fields of transportation (tires, wiper blades, seals etc.), prosthetics and soft robotics. Most surfaces are inherently rough and the interfacial area between two contacting bodies depends largely on the material properties and surface topography of the contacting bodies. Johnson, Kendall and Roberts (JKR) derived an equilibrium energy balance for the behavior of smooth elastic spherical bodies in adhesive contact that predicts a thermodynamic work of adhesion for two surfaces in contact. The JKR equation gives a reversible work of adhesion value during approach and retraction. However, viscoelastic dissipation, surface roughness and chemical bonding result in different work of adhesion values for approach and retraction. This discrepancy is termed adhesion hysteresis. Roughness is undermined as a cause of hysteresis in adhesion studies. Recently, a continuum mechanics model has been developed that predicts the work of adhesion on rough surfaces with known roughness in the form of power spectral density (PSD) function. To test the above mentioned theoretical model, we have conducted JKR experiments between highly cross-linked smooth polydimethylsiloxane (PDMS) of four different elastic moduli and diamond surfaces of four different crystal sizes and roughness.The rough diamond surfaces are characterized for topography using stylus profilometry, atomic force microscopy and in-situ transmission electron microscopy combined to give a comprehensive PSD. Results suggest that the observed work of adhesion during approach is equivalent to energy required to stretch the PDMS network at the surface and in the bulk to form the real rough contact area. However, in retraction work of adhesion is found to be proportional to the ratio of excess energy spent in the loading-unloading cycle and the true contact area obtained from topography indicating conformal contact matching fracture mechanics behavior. Thus, the study resolves adhesion hysteresis discrepancy on rough surfaces. It is known that adhesion hysteresis increases interfacial friction on rough surfaces. However, an experimentally proven quantitative model is still missing. Previous studies on smooth surfaces have shown that shear stress increases with velocity initially, reaching a maximum and then either plateaus out or decreases depending upon the modulus of the sliding elastomer. We have performed shear measurements with velocities ranging from nm/sec to cm/sec between PDMS elastomers and diamond surfaces. Data suggests higher shear stresses at lower velocities for rough surfaces and thus a shift for the peak previously observed on smooth surfaces. Additionally, there are states such as steady-state sliding, stick-slip and detachment waves with increasing stress in the same order. These states are found to occur at a critical stress and their onset is linearly proportional to the elastic modulus of the sliding rubber. The stress predictions using existing theories do not decouple adhesion and deformation energy losses during friction observed ex- perimentally on rough surfaces and further investigation is required in order to obtain a better friction model.
Ali Dhinojwala, Ph. D. (Advisor)
Mesfin Tsige, Ph. D. (Committee Chair)
Tevis Jacobs, Ph. D. (Committee Member)
Jutta Luettmer-Strathmann, Ph. D. (Committee Member)
Hunter King, Ph. D. (Committee Member)
143 p.
Engineering; Mechanics; Physics; Polymers; Science Education
roughness; adhesion; friction; contact mechanics; rubber elasticity

Recommended Citations

Citations

  • Dalvi, S. N. (2020). UNDERSTANDING CONTACT MECHANICS AND FRICTION ON ROUGH SURFACES [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron158957808488289

    APA Style (7th edition)

  • Dalvi, Siddhesh. UNDERSTANDING CONTACT MECHANICS AND FRICTION ON ROUGH SURFACES. 2020. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron158957808488289.

    MLA Style (8th edition)

  • Dalvi, Siddhesh. "UNDERSTANDING CONTACT MECHANICS AND FRICTION ON ROUGH SURFACES." Doctoral dissertation, University of Akron, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron158957808488289

    Chicago Manual of Style (17th edition)

akron158957808488289
140
© 2020, some rights reserved.Creative Commons License UNDERSTANDING CONTACT MECHANICS AND FRICTION ON ROUGH SURFACES by Siddhesh Narayan Dalvi is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Akron and OhioLINK.