IMPACT OF ELASTIC SPHERES WITH AND WITHOUT ADHESION

The paper considers the load-displacement behaviour at the contact of two adhered elastic spheres under combined normal and tangential loading. The first part of the paper deals with computer simulated oblique impact of two elastic spheres with friction. The normal and tangential contact stiffnesses are modelled according to the theories of Hertz, see Johnson (Contact Mechanics, Cambridge University Press, Cambridge, 1985) and Mindlin and Deresiewicz, (J. Appl. Mech., Trans. ASME, 20 (1953) 327) and the results show excellent agreement with the experimental work of Maw et al. (J. Lubrication Tech., Trans., ASME, 103 (1981) 74). The paper then considers impact in the presence of adhesion using the theory developed by Johnson et al. (Proc. Roy. Soc. Lond., A, 324 (1971) 301) for colinear impact. A new theory, combining the previous work of Savkoo and Briggs (Proc. Roy. Soc. Lond., A. 356 (1977) 103) and Mindlin and Deresiewicz (J. Appl. Mech. Trans. ASME, 20 (1953) 327), is presented to describe the tangential behaviour. The new theory differs from the previous models in that a new sliding criterion is proposed. Experimental observations for polyethylene-terephthalate monofilaments, Briscoe and Kremnitzer, (J. Phys. D: Appl. Phys., 12 (1979) 505) show good agreement with the proposed sliding criterion. Finally, the results of computer simulated oblique impact of elastic spheres with and without adhesion are compared.