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RESEARCH PRODUCT

An approach to evaluation of sheet bending force under successive multiaxial stress condition

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A new bending under tension test is presented in this paper. This method tries to evaluate bending forces in sheet under successive multiaxial stress condition. This test is carried out in only one step with a pinned cylinder over a material that has been previously deformed to pure shear condition. Due to that, the bending process is made under higher back tension forces than the ones involved in the common methods previously studied in the literature. This entails high pressure values in the sheet-bending tool contact that affects the corresponding friction process. Material is strongly strengthened as a consequence of the deformation practiced in it, and as a result of that, bending forces have higher values if compared with the ones considered in traditional assays. Then, in order to reproduce die radius conditions in deep drawing processes, this test establishes more real results than BUT tests commonly used. We have tried out electrogalvanized DDQ steel as an application of the test. Moreover, apparent pressure in bending tool has been determined by direct measures, that has been added to the traditional methods. Taking into account the apparent pressure values, friction has been evaluated in bending tool and finally the bending force has been obtained from the experimental data. Three bending angles and three tool radii have been experimented and their influence has been evaluated. It has been proved that bending force depends on bending angle to a great extent. Finally, we have shown that die radius has a minor effect on the bending force.