  Solid contacts involving soft materials are important in mechanical
engineering or biomechanics. Experimentally, such contacts have been shown to
shrink significantly under shear, an effect which is usually explained using
adhesion models. Here we show that quantitative agreement with recent high-load
experiments can be obtained, with no adjustable parameter, using a non-adhesive
model, provided that finite deformations are taken into account. Analysis of
the model uncovers the basic mechanisms underlying shear-induced area
reduction, local contact lifting being the dominant one. We confirm
experimentally the relevance of all those mechanisms, by tracking the
shear-induced evolution of tracers inserted close to the surface of a smooth
elastomer sphere in contact with a smooth glass plate. Our results suggest that
finite deformations are an alternative to adhesion, when interpreting a variety
of sheared contact experiments involving soft materials.
