Damage models are basic elements in numerical simulation materials failure in particular at high strain rates. Many damage models can be found in the literature. However, a few of them such as GNT (Gurson, Tvergaard and Needleman) and Johnson-Cook models have gained wide application in the simulations. The models involve a number of constants to be determined normally by experiment in which void development in the specimen must be considered. This is usually a hard task and the results are always questionable. In this investigation a combined experimental, numerical and optimization technique is employed for identification of the constants of Johnson-Cook material and damage model. The experiments are conducted at low to high strain rate regimes using standard testing devices such Instron and high rate apparatuses such as “Flying Wedge”. The experiments are simulated using the same specimen geometries and the apparatus. The simulations are carried out using the commercial codes, Ls-dyna. The differences between the deformed shapes of the specimens from the experiments and those predicted from the numerical simulations are taken as the objective function for optimization purposes. The optimum constants are obtained using generic algorithm.