FRICTION EVALUATION METHOD FOR METAL FORMING BY A COMPRESSION-TWIST TYPE TESTING MACHINE Carlos Eddy Valdez Salazar Laboratório de Engenharia de Fabricação – Dept. de Engenharia Mecatrônica e de Sistemas Mecânicos - Escola Politécnica da Universidade de São Paulo – Av. Prof. Mello Moraes, 2231 – 05508.900 S. Paulo – SP. carlos.salazar@poli.usp.br Marco Stipkovic Filho Laboratório de Engenharia de Fabricação – Dept. de Engenharia Mecatrônica e de Sistemas Mecânicos - Escola Politécnica da Universidade de São Paulo – Av. Prof. Mello Moraes, 2231 – 05508.900 S. Paulo – SP. kovic@osite.com.br Gilmar Ferreira Batalha Laboratório de Engenharia de Fabricação – Dept. de Engenharia Mecatrônica e de Sistemas Mecânicos - Escola Politécnica da Universidade de São Paulo – Av. Prof. Mello Moraes, 2231 – 05508.900 S. Paulo – SP. gfbatalh@usp.br Abstract. This work presents the development of a mechanical systems acting as a new compression twist type friction testing machine in order to simulate frictional conditions prevailing in flat contact for sheet metal forming conditions. Its main objective was to allow for obtaining data for model simulations of the tool-workpiece interface. As a specific objective the operational capacity of the developed system was evaluated trough fundamental friction tests carried out with laser textured surface specimens of an aluminum alloy AA 6016 T4 sliding against an ABNT 1045 steel indenter in order to investigate the friction behavior at an interface (steel – aluminum alloy) Keywords.: Manufacturing, metal forming, friction, twist-compression. 1. INTRODUCTION A better control for sheet metal forming is still a great challenge. After reducing the scattering of some effects like mechanical properties, surface defects and lubrication conditions, the surface topography and its effects stands as characteristic with great potential for a process optimization as well as of the formed part. This reinforces the developments needs for new process and test improving sheet metal surface tribological characterization (Batalha 1995,1998, 1999, 2000 and 2001). Concerning the improving of new models used sheet metal forming simulation, some efforts has been made in order to develop new improved test and methods for friction evaluation. In this sense, the conception and construction of new devices and/or equipments for friction evaluation under conditions nearer to the sheet metal forming industry reality represents an important research field, as the both experimental and theoretical modeling approaches, analytical or numerical, need an quantitative evaluation the more accurate as possible for the boundary conditions, specially for a local friction coefficient or factor, acting on the tool-workpiece interface (Schey, 1983, Kawai, 1984, Kalpakjian, 1985 and Budinski, 1992). All tests aiming to evaluate the friction in the toolworkpiece interface need to regard the surface characteristics of this interface, keeping in mind that they change during the forming contact and deformation processes.