The energy requirements and environmental impacts of sheet metal forming: An analysis of five forming processes

Production of low-volume aviation components using disposable electromagnetic actuators

The flexforming process is a sheet metal forming method that uses hydraulic fluid pressure and a rubber diagram to form sheet metal with a die. This study, for the first time, experimentally investigates the factors affecting the springback resulting from the bending of copper and brass sheet metal materials in V-bending dies using the flexforming process. Additionally, the formability during the V-bending method was experimentally investigated by using thin, high-pressure-resistant rubber membranes instead of the thick ones commonly used in the flexforming processes. The process parameters in the experimental studies were determined to be: holding time (0, 5 and 10 s), bending angle (\(15^{\circ }, 30^{\circ }, 45^{\circ }, 60^{\circ }, 75^{\circ }\) and \(90^{\circ })\) and fluid pressure (10, 12 and 14.4 MPa). Sheet metals were formed in V-bending dies by both flexforming and conventional bending processes to compare the performance of the flexforming process against the conventional bending process. Springback values in the parts formed using the flexforming process for copper and brass sheet metals were determined to be 39.06 and 41.42% less, respectively, than those formed by the conventional bending method. Surface flaws occurring in the parts formed by the conventional bending method were not observed in the parts formed using the flexforming process. The springback was also estimated by using fuzzy logic based on unexecuted break-test parameters. When the outputs of the fuzzy logic system were compared with the experimental results, it was observed that the results were substantially similar.

The Experimental Investigation of Springback in V-Bending Using the Flexforming Process

One of the most significant problems in bending sheet metals is the springback behavior caused by the elastic stress formed after the bending process. In this study, the effects of forming pressure, die angle and holding time on the springback behavior were experimentally investigated for V-bending using the flexforming process. Furthermore, springback behavior was predicted using a fuzzy logic system based on unexecuted break-test parameters. The study was carried out using a thin rubber membrane instead of the thick ones normally used in flexforming processes. During the flexforming process, it was observed that springback were 60.57% and 41.92% less than those formed by a conventional die for AL1050-0 and AL5754-0 sheet metal materials, respectively. It was determined that an increase of 15 degree in the die angle increased springback values on average by 0.12 degree and 0.23 degree for AL1050-0 and AL5754-0, respectively. It was also found that an increase of 10 seconds in the holding time decreased springback values on average by 0.14 degree and 0.19 degree for AL1050-0 and AL5754-0, respectively. It was determined that there were no forming defects on the surfaces of the parts bent through the flexforming process.

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The Evaluation of Process Parameters on Springback in V-bending Using the Flexforming Process

Electromagnetic forming is a process used to produce high strain rates that improve the formability of sheet metal. The objective of this paper is to discuss the feasibility of the use of disposable actuators during electromagnetic forming of two aluminum components: an industry part whose main feature is a convex flange with two joggles, and a simple part with a one-dimensional curve throughout. The main forming complications after the parts were formed using conventional methods were the presence of wrinkles and excessive springback. The goal of this work is to use large, controlled electromagnetic impulses to minimize the springback of these components from a roughformed shape, with the end result being a dimensionally correct part. The optimum test protocols for electromagnetic calibration of the components were determined by optimizing parameters such as design of the actuator, tool material, and capacitor discharge energy. The use of disposable actuators for electromagnetic calibration of the parts showed significant reductions in springback compared to the parts which were only preformed using conventional techniques (hydroforming and rubber-pad forming). Springback was decreased in the curved component by up to 87%. For the flanged component, the wrinkles were eliminated, the joggles were formed properly, and the average bending angle of the part was improved from 95.3° to 90.3°, very near the target bending angle of 90°. This study demonstrates that these forming techniques can be used to improve current sheet metal production processes. * The authors would like to thank Cutting Dynamics, Inc. for providing financial support, materials, and tooling for this study. Thanks to Geoffrey Taber for his support for the experiments. Thanks to the Martin-Schmeiβer Foundation for providing financial support for this study.

Agile Production of Sheet Metal Aviation Components Using Disposable Electromagnetic Actuators

In this paper, the flexforming process is modeled by finite element method in order to investigate the operation window of the problem. Various models are established using explicit approach for the forming operation and implicit approach for the unloading one. In all analyses the rubber diaphragm has been modeled revealing that the modeling of this diaphragm is essential. Using the material Aluminum 2024 T3 alclad sheet alloy, three basic experiments are conducted: Bending of a straight flange specimen, bending of a contoured flange specimen and bulging of a circular specimen. By these experiments the effects of blank thickness, die bend radius, flange length and orientation of the rolling direction of the part have been investigated. Experimental results are compared with finite element results to verify the computational models.

Modeling Flexforming (Fluid Cell Forming) Process with Finite Element Method

In this study, it is aimed to determine the friction coefficient between die surface and blank in flexforming (fluidcell forming) process in which a pressurized rubber diaphragm is used to form the sheet. An aluminum square pan is chosen for the workpiece and it is drawn at various pressures and friction conditions (with lubricant, without lubricant, etc.). Numerical models of the process are established with different friction coefficients and results are then compared with the experiments in order to determine the corresponding coefficients of the friction conditions. The displacement of the flange edge is used for comparison.

H. Ali Hatipoğlu

Papers

Modeling Flexforming (Fluid Cell Forming) Process with Finite Element Method

A Methodology to Determine the Friction Coefficient in Flexforming (Fluidcell Forming) Process