An algorithm and a method to search bifurcation points in non-linear problems

This paper is devoted to a numerical method able to help the determination of the bifurcation threshold in non-linear time-independent continuum mechanic problems. First, some theoretical results about uniqueness are recalled. In the framework of the large-strain assumption, the di erences between the classical nite-step problem and the rate problem are presented. An iterative algorithm able to solve the rate problem is given. Using di erent initializations, it is seen in some numerical experiments that it is possible with this algorithm to get di erent solutions when the underlying mathematical problem solved does not enjoy a uniqueness property. The constitutive equations used have been chosen to be simple enough to deduce some theoretical knowledge about the corresponding uniqueness problems. Finally, a method is given which is able in some case to give an upper bound of the bifurcation threshold