Showing papers by "Taylan Altan published in 2019"
TL;DR: In this article, the effect of post stretching, applied by the use of a servo hydraulic cushion, on reduction of residual stresses and springback at the wall is investigated, and the benefit of using a hydraulic cushion for reducing springback and residual stresses has been demonstrated experimentally.
Abstract: The increasing use of aluminum alloys in automotive industry brings new challenges regarding formability and springback. Servo presses and servo hydraulic cushions can accurately control ram motion and blank holder force during the forming process, reducing the difficulties encountered in forming Al alloys. This study presents an experimental and numerical analysis of springback and residual stresses induced during the U-channel drawing of Al 5182-O. During the U-channel drawing, the draw-in of the sheet material into the die cavity is controlled by blank holder force. So, the material is under stretch bending condition when it slides around the die corner radius. When the material passes the die corner radius it unbends. The reverse loading resulted from the unbending process provides heterogeneous stress distribution through the sheet thickness in the wall section. The effect of post stretching, applied by the use of a servo hydraulic cushion, on reduction of residual stresses and springback at the wall is investigated. The benefit of using servo hydraulic cushion for reducing springback and residual stresses has been demonstrated experimentally. Results illustrate a significant reduction of residual stresses and springback when post stretching is applied.
9 citations
TL;DR: In this article, the authors used finite element simulations and experimental measurements to determine the interface temperature in an industrial ironing operation, where severe process parameters lead to lubricant film breakdown and galling after several strokes.
5 citations
02 Apr 2019
TL;DR: In this paper, the edge stretchability in collar forming is related to the strain hardening along the pierced edge; thus, Finite Element simulations can be used to reduce the number of experiments required to improve cutting settings for a given material and thickness.
Abstract: Edge fracture is a common problem when forming advanced high strength steels (AHSS). A particular case of edge fracture occurs during a collar forming/hole extrusion process, which is widely used in the sheet metal forming industry. This study attempts to relate the edge stretchability in collar forming to the strain hardening along the pierced edge; thus, Finite Element (FE) simulations can be used to reduce the number of experiments required to improve cutting settings for a given material and thickness. Using a complex-phase steel, CP-W 800 with thickness of 4.0 mm, a single-stage piercing operation is compared with a two-stage piercing operation, so called shaving, in terms of strains along the pierced edge, calculated by FE simulation. Results indicated that strains were reduced along the pierced edge by shaving. These results are correlated with experimental observations made at the Technical University of Munich (TUM) where better hole expansion ratios (HERs) were obtained using shaving as opposed to single-stage piercing. Moreover, in this study, the combination of cutting parameters that would generate the least edge strain hardening is evaluated based on simulation results. This approach could reduce the need for hardness measurements along the pierced edge as well as the number of experiments required to improve the shaving process.
2 citations