Papers by Hüseyin Selçuk HALKACI
In this paper, an improved approach is proposed to determine the optimal profiles of two control... more In this paper, an improved approach is proposed to determine the optimal profiles of two controllable process parameters (hydraulic pressure and blank holder force), which improve the forming condition and/or make better use of forming limits in hydromechanical deep drawing (HMD) process. A method based on adaptive finite element analysis coupled with fuzzy control algorithm (aFEA-FCA) was developed using LS-DYNA to determine the optimal loading profiles and thus to maximize the limiting drawing ratio (LDR). Maximum thickness reduction, maximum wrinkle height in the flange region of the sheet metal blank, and position of the nodes in the unsupported portion of the sheet metal blank between punch and die were used as criteria in the fuzzy control algorithm. Different rule-based matrices were compared by considering the maximum thinning occurred in the sheet metal blank, and thus, the most accurate matrices were determined for the control algorithm. The optimal loading profiles could be determined in a single FEA, thus reducing the computation time. The proposed approach enables determining the optimal loading profiles and also could be applied to complex parts easily. In addition, effects of initial blank diameter and coefficient of friction between the sheet-blank
holder and sheet-die on the optimal loading profiles were investigated. An attainable LDR of 2.75 for AA 5754-O sheet material in hydromechanical deep drawing process was proven experimentally using the optimal loading profiles determined by adaptive FEA.
Rubber pad stamping process is mostly used in aerospace and automotive applications and is conven... more Rubber pad stamping process is mostly used in aerospace and automotive applications and is convenient for small-scale production of sheet metal parts. Simulation of this process requires a lot of processing time since rubber parts cannot be modelled utilizing shell elements. This deficiency was eliminated by considering 2D axisymmetric approach in LS-DYNA explicit finite element software. Inconel 625 and DX56D galvanized sheet metal blanks were used with the support of four rubber pads. There are many simulation parameters for successful modelling of the process. In this study, all the parameters needed for an accurate finite element analysis of this process are determined. Consequently, the blanks were successfully formed in simulations with a gain of approximately 50% in CPU time as compared to 3D analyses.
Warm hydroforming is an innovative forming technology in which sheet metals or tube materials are... more Warm hydroforming is an innovative forming technology in which sheet metals or tube materials are formed by pressurized fluid at warm forming temperatures. Warm hydroforming ensures an additional formability increase and decreasing the necessary fluid pressure and closing force according to hydroforming. Besides the parts manufactured by warm hydroforming shows more strength then hydroforming. There are two types of warm sheet hydroforming as in sheet hydroforming. If the used tool is punch the process named as warm hydromechanical deep drawing (WHDD) and if it is die the name is warm sheet hydroforming with die (WSHF-D). If it is desired to manufacture deeper cups, warm hydromechanical deep drawing process is suitable but if the cups are shallow warm sheet hydroforming with die can be applied. WHDD process is complex than WSHF-D. Because it is necessary that the blank should have a temperature gradient in order to achieve a successful forming and the fluid pressure and blank holder force should have a path according to position of the punch in WHDD process. But in WSHF-D all areas of the sheet metal blank are heated to same temperature and the pressure is increased linearly up to maximum pressure. So implementation of WSHF-D more easy. But transition height of the cups from WSHF-D to WHDD was not reported and if a cup can be manufactured by both process, which process ensures good forming not known. Therefore in this study manufacturing of a cup having 40 mm diameter and 20 mm in depth from AA 5754 blank having 1 mm thickness were simulated by Finite Element Analysis for both of the processes. Then obtained cups were compared in terms of accuracy of geometry, maximum thinning and necessary fluid pressure and closing force. Consequently it was found that maximum thinning was lesser and thickness distribution was more uniform in WHDD process. So it was concluded that WHDD process serve better forming in terms of manufactured cups. But as the part could be manufactured with non-defect with WSHF-D and WHDD process rather complex, the choice of WSHF-D for simplicity of the process wouldn't be wrong.
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Papers by Hüseyin Selçuk HALKACI
holder and sheet-die on the optimal loading profiles were investigated. An attainable LDR of 2.75 for AA 5754-O sheet material in hydromechanical deep drawing process was proven experimentally using the optimal loading profiles determined by adaptive FEA.
holder and sheet-die on the optimal loading profiles were investigated. An attainable LDR of 2.75 for AA 5754-O sheet material in hydromechanical deep drawing process was proven experimentally using the optimal loading profiles determined by adaptive FEA.