Collective effects at frictional interfaces

We discussed the role of the long-range elastic interaction between the contacts inside an inhomogeneous frictional interface. The interaction produces a characteristic elastic correlation length lambda(c) = a (2) E/k (c) (where a is the distance between the contacts, k (c) is the elastic constant of a contact, and E is the Young modulus of the sliding body), below which the slider may be considered as a rigid body. The strong inter-contact interaction leads to a narrowing of the effective threshold distribution for contact breaking and enhances the chances for an elastic instability to appear. Above the correlation length, r > lambda(c), the interaction leads to screening of local perturbations in the interface, or to appearance of collective modes-frictional cracks propagating as solitary waves.