Abstract: Rigid-plastic Finite Element Method (RFEM) is non-linear,so it is necessary to give a good initial velocity field and to ensure for evaluation. Ori K. I. proposed "function G" to determine the initial velocity field, but he didn't make a through analysis. Newton-Raphson method is generally used in RFEM, but it has some drawbacks:
1) it is possible to deverge during itterating;and 2) the step is difficult to determine, so that the calculating time is increased.
In order to Overcome the drawbacks above mentioned,we advanced a new method-penality method of function G and carried on a detail analysis. As iteration method the Gill-Murrary mothod (improved Newton method) is used instead of Newton-Raphson method and the linear search is made by 0.618 method.
The RFEM program is worked out for calculating parameters of plastic working processes. The calculating results obtained in studying roll-ing process coincide with the experimental data. The research shows clearly that the improved RFEM method is satisfactory for analysing plastic working problems.