An Inverse Identification Technique Of Friction Coefficient In Sheet Metal Forming

In sheet metal forming, friction is one of the key factors to influence product quality (both geometry and surface finish) and tool wear. The frictional properties in sheet metal forming are complex and the coefficient of friction is difficulty to be measured directly. In numerical simulation of sheet metal forming, the accuracy of analysis is limited by the knowledge of friction. Therefore, how to model the friction properties and measure the friction coefficient in sheet metal forming processes are concerned seriously.In this paper, an inverse technique has been suggested to identify the friction coefficient in metal forming processes. A tensile test is employed to measure the displacement of the specimen. On the other hand the computed displacement of specimen can be calculated by FEM software. Genetic algorithm is adopted as the inverse procedure in this technique to find the friction coefficient which minimize the difference between measured displacements and computed ones.A tensile test has been developed to obtain the relation between displacement of specimen and force. The test is carried out in a tensile testing machine. The FEM software LS-DYNA is used as the forward solver to calculate the dynamic displacement response of specimen. Coulomb friction principle is used to calculate frictional force. Because of the excellent performance of convergence, intergeneration project genetic algorithm is adopted to identify friction coefficient in this paper.The sensitivity and stability to noise contamination in the input displacement response data are also investigated in detail. Some parameters in genetic algorithm has been considered. It is found that the present inverse procedure is very efficient for identifying the friction coefficient between specimen and die.