• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.117-126
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• 1998

For investigating rubber pad sheet metal forming process, the rubber pad deformation characteristics as well as the contact problem of rubber pad-sheet metal has been analyzed. In this paper, the behavior of the rubber deformation is represented by hyper-elastic constitutive relations based on a generalized Mooney-Rivlin model. Finite element procedures for the two-dimensional responses, employing total Lagrangian formulations are implemented in an implicit form. The volumetric incompressibility condition of the rubber deformation is included in the formulation by using penalty method. The sheet metal is characterized by elasto-plastic material with strain hardening effect and analyzed by a commercial code. The contact procedure and interface program between rubber pad and sheet metal are implemented. Inflation experiment of circular rubber pad identifies the behaviour of the rubber pad deformation during the process. The various form dies and scaled down apparatus of the rubber-pad forming process are fabricated for simulating realistic forming process. The obtaining experimental data and FEM solutions were compared. The numerical solutions illustrate fair agreement with experimental results. The forming pressure distribution according to the dimensions of sheet metal and rubber pads, various rubber models and rubber material are also compared and discussed.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.3
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• pp.221-232
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• 2017

In this study, bipolar plates in fuel cells are formed using rubber forming process. The effects of important parameters in rubber forming such as hardness and thickness of rubber pad, speed and pressure of punch that compress blank, and physical property of materials on the channel depth were analyzed. In the soft material sheet Al1050, deeper channels are formed than in materials STS304 and Ti-G5. Formed channel depth was increased when hardness of rubber pad was lower, thickness of rubber pad was high, and speed and pressure of punch were high. It was found the deepest channel was achieved when forming process condition was set with punch speed and pressure at 30 mm/s and 55 MPa, respectively using rubber pad having hardness Shore A 20 and thickness 60 mm. The channel depths of bipolar plates formed with Al1050, STS304 and Ti-G5 under the above process condition were 0.453, 0.307, and 0.270 mm, respectively. There were no defects such as wrinkle, distortion, and crack found from formed bipolar plates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.111-120
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• 1998

This paper is the first one of two-parted research efforts focusing on the modeling of rubber pad forming process. The rubber pad, driven by the pressurized fluid during the forming process, pushes the sheet metal to solid tool half and forms a part to final shape. In this part of the paper, a numerical procedure for the FE analysis of the rubber pad deformation is presented. The developed three-dimensional FE model is based on the total Lagrangian description of rubber maerial characterized by nearly incompressible hyper-elastic behavior under a large deformation assumption. Validity of the model as well as effects of different algorithms corresponding to incompresibility constraints and time integration methods on numerical solution responses are also demonstrated.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.4
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• pp.175-181
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• 2018

Stamping process and rubber pad forming process were performed to manufacture the bipolar plate for fuel cells. For that, a vacuum die casting process and a semi-solid forming process wherein liquid-state materials were used were adopted. After preparing the blank with the stainless steel thin plate having a thickness of 0.1 mm, the bipolar plate channel was formed with the stamping process and rubber pad forming process. The depth of the bipolar plate channel prepared by the stamping method was 0.45 mm and the depth of the bipolar plate channel prepared by the rubber pad forming process was 0.41 mm. Meanwhile, with the vacuum die casting and semi solid forming, the bipolar plate having a channel depth of 0.3 mm, same as the size of the die, could be formed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.148-151
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• 2009

This paper presents an experimental study of deep-drawing and rubber-pad forming process using titanium alloy sheet. The process and results of the work carried out to investigate the capability of the process and to optimize th process parameters to ensure a sound forming. Room and high temperature tensile tests were carried out at various process conditions and microstructural evaluation was investigated. The experimental investigation was done using 150 ton hydraulic press to produce a deep-drawn part. Both graphite lubricant and polyethylene sheet were essential for defect-free product. Regarding the rubber-pad forming, reasonable formability was obtained only for pure-Ti not for Ti-6Al-4V.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.121-131
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• 1998

This paper applies the FE analysis procedure, developed in the Part I of the companion article, to the three-dimensional rubber pad deformation during rubber-pad forming process. Effects of different algorithms corresponding to incompressibility constraint and time integration methods on numerical solution responses are investigated. Laboratory scale experiments support the validity of the developed FE procedure an demonstrate the accuracy of the numerical models. Full scale model responses are also predicted using the reasonable method and parameters obtained in laboratory modeling.

• Elastomers and Composites
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• v.43 no.3
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• pp.173-182
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• 2008

Rubber-pad forming process for materials such as metal in which portions of the die which act upon the material is composed of a natural or synthetic rubber or elastomer material. This makes the rubber pad forming process relatively cheap and flexible, high accuracy for small product series in particular. In this study, we carried out the physical test and finite element analysis of elastomer such as natural rubber and urethane for steel rack rube forming. The non-linear property of elastomer which are described as strain energy function are important parameter to design and evaluate of elastomer component. These are determined by material tests which are uni-axial tension and bi-axial tension. This study is concerned with simulation and investigation of the significant parameters associated with this process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.06a
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• pp.87-97
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• 1994

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.279-284
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• 2007

Elasto-forming has been dedicated to specific and limited production. Today, using enhanced pad materials, it has become an efficient and economical process alternative for low and medium volume metal-forming production. The non-linear properties of elastomer which are described as strain energy function are important parameter to design and evaluate of elastomer component. These are determined by material tests which are uni-axial tension and bi-axial tension. In order to investigate the design paramerer, Finite element analysis was carried out for elasto-forming process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.549-556
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• 2010

In general, materials that can be used to form elastic pads, such as urethane and rubber, are often used in flexible forming processes by inserting the pads between a blank and flexible die for smoothing the forming surface that is formed by a reconfigurable die. In this study, the effects of the elastic pad on formability in the flexible forming process for sheet metals are investigated by performing numerical simulations. In the simulation, the hyperelastic material model is used, where the urethane elastic pads serve as elastic cushions. Case studies are carried out for elastic materials with different hardness values and thicknesses. The results are used to evaluate formability by comparing the configuration of the deformed blank and its major cross-sectional profiles. It is verified that the elastic pad used in the flexible forming process for sheet materials should be hard and that its thickness should be chosen appropriately.