Improvement of Formability for Multi-point Bending Process of AZ31B Sheet Material Using Elastic Cushion

다국어 초록 (Multilingual Abstract)

On multi-point forming process, one of the most obvious limitations is the need for a pliable interpolating material such as elastic cushion between punch element tips and sheet metal to prevent the formation of dimples on the surface of final part.
In this study, numerical simulations of multi-point bending process in case of different thicknesses of elastic cushion are performed to obtain a specified final shape as a cylindrical surface with curvature radius of 434.65mm and centre angle parameter of 52.73° by using initial blank with length of 800mm, width of 600mm, and thickness of 2mm, respectively. To find the suitable thickness of the elastic cushion, four evaluating indicators including plastic dissipation energy, stress components, shape error and maximum ductile damage are introduced and analyzed. As the results, each value of four evaluating indicators is decreased, and their distributions become more uniform on the deformed blank by adopting the elastic cushion. Resultantly, it is summarized that the formability of AZ31B magnesium alloy can be improved by using the elastic cushion, and the most proper thickness of the elastic cushion is 4 mm for the multi-point bending process of AZ31B sheet with thickness of 2mm.

참고문헌 (Reference)

1 Zhang,Q, "The Mechanics of Multi-Point Sandwich Forming" 48 (48): 1495-1503, 2008

2 Yang,Y.B, "Plastic deformation mechanisms of AZ31 magnesium alloy under high strain rate compression" 18 (18): 1043-1046, 2008

3 Li,L, "Numerical Simulations on Reducing the Unloading Springback with Multi-Step Multi-Point Forming Technology" 48 (48): 45-61, 2010

4 Cai,Z.Y, "Numerical Simulation for the Multi-Point Stretch Forming Process of Sheet Metal" 209 (209): 396-407, 2009

5 Cai,Z.Y, "Multi-Point Forming of Threedimensional Sheet Metal and the Control of the Forming Process" 79 (79): 289-296, 2002

6 Li,M.Z, "Multi-Point Forming Technology for Sheet Metal" 129 (129): 333-338, 2002

7 Ye,D, "Further Investigation of Neuber’s Rule and the Equivalent Strain Energy Density(ESED)Method" 26 (26): 447-455, 2004

8 Cai,Z.Y, "Finite Element Simulation of Multi-Point Sheet Forming Process Based on Implicit Scheme" 161 (161): 449-455, 2005

9 Kysar,J.W, "Energy Dissipation Mechanisms in Ductile Fracture" 51 (51): 795-824, 2003

10 김기주, "Development of Application Technique of Aluminum Sandwich Sheets for Automotive Hood" 한국정밀공학회 10 (10): 71-75, 2009

11 Wei,T, "Assessment of the Fracture Toughness of 6061 Aluminium by the Small Punch Test and Finite Element Analysis" 30 : 39-44, 2006

12 허성찬, "Application of flexible forming process to hull structure forming" 대한기계학회 24 (24): 137-140, 2010

13 Ragai,I, "Anisotropy and springback in draw-bending of stainless steel 410:experimental and numerical study" 166 (166): 116-127, 2005

14 Al-Qureshi,H.A, "Analysis of Simultaneous Sheet Metal Forming Operations Using Elastomer Technique" 125 (125): 751-755, 2002

15 Heo,S.C, "A study on thick plate forming using flexible forming process and its application to a simply curved plate" SPRINGER LONDON LTD 51 (51): 103-115, 201011

16 Mediavilla,J, "A Nonlocal Triaxiality-Dependent Ductile Damage Model for Finite Strain Plasticity" 195 (195): 4617-4634, 2006

17 Mkaddem,A, "A New Procedure Using the Microhardness Technique for Sheet Material Damage Characterisation" 178 (178): 111-118, 2006

18 Ozturk,F, "A New Methodology for Ductile Fracture Criteria to Predict the Forming Limits" 16 (16): 224-228, 2007