EVIDENCE OF NONLINEAR DISLOCATION MOTION IN INTERNAL FRICTION EXPERIMENTS H.-J. KAUFMANN, P.P. PAL-VAL, V.M. CHERNOV and D.A. KAMAJEV J. Phys. Colloques, 48 C8 (1987) C8-113-C8-117 DOI: 10.1051/jphyscol:1987813