Improvement of a Testing Method of Cold Forging Performance of Steel Wires

A testing method to determine the flow stress of wire material and the friction coefficient of solid lubricant coating proposed by authors is improved using the simulations. Finite element analyses with the elastic tools are compared with those with the rigid tools to develop the method to eliminate the effect of the elastic deformation of the tools on the punch stroke. The modification method of the parameters of the flow curve is developed to accurately predict the flow stresses for large strain range from 0 to 3 despite of the maximum strain in the specimen during testing is approximately 0.5. The temperature increase during testing by the friction between the specimen and tools and plastic work of the specimen is simulated and then change of the friction coefficient which is a function of the temperature at the coating is evaluated to determine the appropriate testing speed to minimize the predictive error of the friction coefficient.