CHAOS IN JERKY FLOW - EXPERIMENTAL-VERIFICATION OF A THEORETICAL PREDICTION

Sometime ago Ananthakrishna and coworkers had predicted the existence of chaos in jerky flow based on a nonlinear dynamical model consisting of the time evolution equations for three types of dislocations and a n equation for the evolution of the stress. Our main focus here is to report the verification of this prediction by analysing the stress sig nals obtained from samples of AlCu alloys subjected to a constant stra in rate test. The analysis of the stress signals is carried out by usi ng several methods. The analysis shows the existence of a finite corre lation dimension and a positive Lyapunov exponent. We also carry out a surrogate analysis of the time series to ascertain that the signals a re not from a power law stochastic process. From the analysis we find that the minimum number of variables required for a dynamical descript ion of the jerky flow appears to be four or five, consistent with the number of degrees of freedom envisaged in the model.