An efficient inverse approach for material hardening parameter identification from a three-point bending test

The cyclic three-point bending test has been frequently used for the determination of material hardening parameters. The advantage of this test is that it is simple to perform, and standard test equipment can be used. The disadvantage is that the material parameter identification requires some kind of inverse approach. The current authors have previously, successfully been utilizing a method, in which computed force-displacement relations have been fitted to corresponding experimental results. The test has been simulated by means of the Finite Element code LS-DYNA, and the material parameters have been determined by finding a best fit to the experimental results by means of the optimization tool LS-OPT, based on a response surface methodology. A problem is, however, that such simulations can be quite time consuming, since the Finite Element model has to be analyzed numerous times. In the current paper, an alternative numerical methodology will be described, in which instead calculated moment-curvature relations are fitted to experimental ones. This optimization procedure does not involve any solution of the FE problem. The Finite Element problem needs only to be solved a limited number of times in an outer iteration loop. This fact results in a considerable reduced computational cost. It is also demonstrated that the parameters determined by this new method correspond excellently to the ones determined by the conventional method.