On the Degree of Irreversibility of Friction in Sheared Soft Adhesive Contacts

Abstract

A number of authors have experimentally assessed the influence of friction on adhesive contacts, and generally the contact area has been found to decrease due to tangential shear stresses at the interface. The decrease is however generally much smaller than that predicted already by the Savkoor and Briggs 1977 classical theory using “brittle” fracture mechanics mixed mode model extending the JKR (Griffith like) solution to the contact problem. The Savkoor and Briggs theory has two strong assumptions, namely that (i) shear tractions are also singular at the interface, whereas they have been found to follow a rather constant distribution, and that (ii) no dissipation occurs in the contact. While assumption (ii) has been extensively discussed in the Literature the role of assumption (i) remained unclear. We show that assuming entirely reversible slip at the interface with a constant shear stress fracture mechanics model leads to results almost indistinguishable from the Savkoor and Briggs model (and further in disagreement with experiments), hence it is assumption (ii) that critically affects the results. We analyze a large set of experimental data from Literature and show that the degree of irreversibility of friction can vary by orders of magnitude, despite similar materials and geometries, depending on the velocity at which the tangential load is applied.

First yield in the Maugis‐adhesive contact of elastic spheres

“…Papangelo and Ciavarella [30] demonstrated the sensitivity of the problem to the concrete superposition functions of different crack modes ( [31], [32]). Also, it has been shown [33] that, of the two main assumptions of the LEFM treatment of frictional adhesion-namely the singularity of shear stresses and the absence of dissipation in the contact-only the second plays a relevant role for the physical description. Lengiewicz et al [34] successfully attributed the shear-induced contact area reduction in soft elastic materials to contact lifting due to finite deformations and non-linear elasticity.…”

Влияние Адгезии На Трение Качения И Скольжения: Эксперимент

“…8, a и b показаны зависимости силы трения F x и ее отношения к нормальной силе F x /F N от величины тангенциального смещения индентора x при наличии адгезии между индентором и эластомером. Известно, что тангенциальный сдвиг в адгезионном контакте уменьшает площадь контакта [14,24]. С другой стороны, в процессе нормального индентирования в адгезионном контакте площадь контакта больше, чем в контакте без адгезии, хотя используемые нами материалы в фазе вдавливания показывают незначительный рост площади контакта за счет адгезии (рис.…”

“…Позже в работе [10] был продемонстрирован переход между этими двумя предельными случаями при изменении характерного расстояния убывания адгезионных сил. В настоящее время адгезионный контакт активно исследуется различными научными группами как экспериментально [6,[11][12][13], так и теоретически [14][15][16]. Экспериментальные работы по изучению прочности адгезионного контакта на отрыв показывают, что в системах, имеющих совершенно различные масштабы, существуют общие закономерности [6,12].…”

Incipient sliding of adhesive contacts

“…The withdrawal of adhesive balls has been addressed analytically by several authors using models based on linear elastic fracture mechanics (LEFM) [4,[10][11][12][13][14][15][16][17]. These authors successfully replicated most experimental observations in which adhesion is strong, including the power law decay of the contact area with increasing tangential load, and its shape transformation from circular to elliptical [13].…”