On the interaction of viscoelasticity and waviness in enhancing the pull-off force in sphere/flat contacts
Motivated by roughness-induced adhesion enhancement (toughening and strengthening) in low modulus materials, we study the detachment of a sphere from a substrate in the presence of both viscoelastic dissipation at the contact edge, and roughness in the form of a single axisymmetric waviness. We show that the roughness-induced enhancement found by Guduru and coworkers for the elastic case (i.e. at very small detachment speeds) tends to disappear with increasing speeds, where the viscoelastic effect dominates and the problem approaches that of a smooth sphere. This is in qualitative agreement with the original experiments of Guduru’s group with gelatin. The cross-over velocity is where the two separate effects are comparable. Viscoelasticity effectively damps roughness-induced elastic instabilities and makes their effects much less important. Graphical Abstract: [Figure not available: see fulltext.].
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Open access funding provided by Politecnico di Bari within the CRUI-CARE Agreement. AP and MC acknowledge the support by the Italian Ministry of Education, University and Research under the Programme Department of Excellence Legge 232/2016 (Grant No. CUP-D94I18000260001). A.P. acknowledges support from “PON Ricerca e Innovazione 2014-2020-Azione I.2” - D.D. n. 407, 27/02/2018, bando AIM (Grant No. AIM1895471).