A numerical study on establishing the forming limit curve and indicating the formability of complex shape in incremental sheet forming process

In order to obtain a final sound product by the incremental sheet forming (ISF) process for complex shape using cold rolled steel material, the limit curve based on the maximum wall angle versus maximum deformed height was established utilizing finite element method (FEM) simulations for several square shapes with various wall angles. The forming limit diagram (FLD) obtained from modified maximum force criterion (MMFC) was first used to predict ductile fracture of ISF simulation test and shown the inaccuracy when comparing with corresponding experimental results. The FLC at fracture (FLCF) curve regarding to tool dimension effects was then proposed, inputted to FEM simulation and approved in good agreement with experiment results. After that wall angle of square shapes was changed to verify its effect on fracture height of the square shapes and obtain the forming limit curve. Finally, wall angles with corresponding maximum deformed height of complex shapes were put into the obtained forming limit to investigate “fail” or “safe” shapes and validated by corresponding experiments.

[1]  Dorel Banabic,et al.  A new formulation of the modified maximum force criterion (MMFC) , 2010 .

[2]  Stuart P. Keeler,et al.  Determination of Forming Limits in Automotive Stampings , 1965 .

[3]  R. Hill,et al.  On discontinuous plastic states, with special reference to localized necking in thin sheets , 1952 .

[4]  Duc-Toan Nguyen,et al.  Finite element method study of incremental sheet forming for complex shape and its improvement , 2010 .

[5]  Julian M. Allwood,et al.  A structured search for applications of the incremental sheet-forming process by product segmentation , 2005 .

[6]  Fabrice Morestin,et al.  Experimental and analytical necking studies of anisotropic sheet metals , 2001 .

[7]  Duc-Toan Nguyen,et al.  Ductile Fracture Prediction in Rotational Incremental Forming for Magnesium Alloy Sheets Using Combined Kinematic/Isotropic Hardening Model , 2010 .

[8]  Heung Nam Han,et al.  A ductile fracture criterion in sheet metal forming process , 2003 .

[9]  H. W. Swift.  Plastic instability under plane stress , 1952 .

[10]  Dong-Won Jung,et al.  Finite element method study to predict spring-back in roll-bending of pre-coated material and select bending parameters , 2012, International Journal of Precision Engineering and Manufacturing.

[11]  Young-Suk Kim,et al.  Prediction of forming limits for anisotropic sheets containing prolate ellipsoidal voids , 2003 .

[12]  J. C. Gerdeen,et al.  Effect of strain gradient and curvature on forming limit diagrams for anisotropic sheets , 1991 .

[13]  Dong-Yol Yang,et al.  Improvement of formability for the incremental sheet metal forming process , 2000 .

[14]  Nguyen Duc-Toan,et al.  Incremental Sheet Metal Forming: Numerical Simulation and Rapid Prototyping Process to make an Automobile White‐Body , 2011 .

[15]  S. Clift,et al.  Fracture prediction in plastic deformation processes , 1990 .

[16]  Do-Sik Shim,et al.  Optimization of forming steps in the incremental forming of twisted shapes using a line array roll set (LARS) , 2010 .

[17]  Beom-Soo Kang,et al.  Improvement of formability for multi-point bending process of AZ31B sheet material using elastic cushion , 2011 .