Size effects in adhesive contacts of viscoelastic media

Is the maximum force required to detach a rigid sphere from viscoelastic substrate dependent on initial value of contact radius? Experimental and theoretical investigations reported in literature have given opposite responses. Here, we try answer above question by exploiting fully deterministic model which adhesive interactions are described Lennard-Jones potential behaviour with standard linear solid model. When approach retraction phases performed under quasi-static conditions, behaves as an elastic medium and, expected, pull-off Fpo (i.e., tensile force) is found be independent radius amax reached at end loading. Size-dependent effects instead observed changes amax) when transient occur larger area, greater size bulk volume involved dissipation. Results also discussed light crack Persson's theory, modified capture related amax.