Global Analysis Method of Friction Parameters in Strip-Drawing Tests

Numerous works have been recently carried out to describe friction and lubrication in the tool-sheet interface. This phenomenon is of great importance for all forming processes, particularly, in the deep drawing operations where the rapid progress in the field of computing requires the predictive knowledge of friction coefficient behaviors. The present paper considers the dynamical modeling by a global approach of the tangential force evolution. All measurements come from a tribometer equipped for strip-drawing tests on lubricated steel sheets and aluminum sheets, as a function of applied normal load. Models are obtained from serial, parallel, or closed-loop association structures for linear transfer functions. Numerical values of delays, time constants, and gain are identified for each test order; complexities and structures are determined with a double optimization. For all situations, a stop criterion is defined to achieve the optimal model, which is reached for the steel sheets.