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Process Simulation and Springback Control in Plane Strain Sheet Bending
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Abstract
Plane strain bending (e.g. bending about a straight line) is a major sheet forming operation and it is practiced as brake bending (air bending, U-die, V-die and wiping-die bending). Precise prediction of springback is the key to the design of the bending dies and to the control of the process and press brake to obtain close tolerances in bent parts. In this paper, reliable mathematical models for press brake bending are presented. These models can predict springback, bendability, strain and stress distributions, and the maximum loads on the punch and die. The elasto-plastic bending model incorporates the true (nonlinear) strain distribution across the sheet thickness, Swift's strain hardening law, Hill's 1979 nonquadratic yield criterion for normal anisotropic materials, and plane strain deformation mode. The formulations and procedure have been programmed to simulate air bending and die bending process with U-die, V-die, and wiping-die, and simulation results compare well with experimental data. Air bending simulations show that the springback angle is proportional to the bending moment and the bent arc length between the punch and die. The bending moment and springback increase with strength, strain hardening, and normal anisotropy. Decreasing the bend arc length by reducing the die opening or die clearance is an effective way to reduce the springback. In air bending, springback can be compensated by overbending through a deeper punch stroke. The necessary ram stroke can be preset in the press controller using the predicted curve of springback vs. stroke. Based on the proposed model for springback, a number of new techniques to reduce springback are discussed, and an optimal bending die design with tractrix profile is suggested to reduce the sensitivity of the bending angle to the variations in press setup and stroke and to control the springback and tolerance in bent parts.
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Wang, C., Kinzel, G., and Altan, T., "Process Simulation and Springback Control in Plane Strain Sheet Bending," SAE Technical Paper 930280, 1993, https://doi.org/10.4271/930280.Also In
References
- Altan (Kadioglu), T. 1962 Approximate Analysis of Press Brake Bending and Springback Technical University of Hanover West German 1962
- Bressan, J.D. 1983 Williams, J.A. The Use of a Shear Instability Criterion to Predict Local Necking in Sheet Metal Deformation Int. J Mech. Sci. 25 1983 155 168
- Crafoord, R. 1970 Plastic Sheet Bending Chalmers University of Technology Gothenburg, Sweden
- Duncan, J.L. 1978 Bird, J.E. Approximate Calculations for Draw Die Forming and Their Application to Aluminum Alloy Sheet Proc. 10th Cong. IDDRG Warwick, England 45 42
- Finckenstein, E. 1988 Fait, J. Rothstein, R. Modeling and Simulation of U-Die Bending Annals of the CIRP 37 1 281 284
- Hill, R. 1948 A Theory of the Yielding and Plastic Flow of Anisotropic Metals Proc. Roy. Sci. London 1948 281 297
- Hill, R. 1950 The Mathematical theory of Plasticity Oxford 1950
- Hill, R. 1979 Theoretical Plasticity of Textured Aggregates Mathematical Proceedings of Cambridge Philosophical Society 85 1979 179 191
- Levy, B.S. 1984 Empirical Derived Equations for Predicting Springback in Bending J. Applied MetalWorking 3 2 1984 135 141
- Liu, Y.C. 1984 Springback Reduction in U-Channel - “Double-Bend” Technique J. Applied MetalWorking 3 2 1984 148 156
- Lowery, P.A. 1977 Computer-Aided manufacturing (CAM) Architecture - Task III - Sheet Metal Fabrication Technology Boeing Military Airplane Development Seattle, Washington Final Technical Report Nov. 1977 Report No. D6-45043-1
- Magnusson, C. 1990 Tan, Z. Mathematical Modeling of V-Die Bending Process Proc. 16th Biannual IDDRG Cong May 17 -22 1990 Stockholm, Sweden 363 370
- Michalich, M.K. 1988 Wenner, M. Calculation of Springback and Its Variation in Channel Forming Operations SAE Paper No. 880526
- Nagai, Y. Makinouchi, A. 1986 Finite Element Simulation of Bending-Restriking Process of Steel Sheets, in Advanced Technology of Plasticity 1 247 255
- Nagpal, V. Subramanian, T.L. Altan T. “Mathematical Modeling of Sheet Metal Formability Indices and Sheet Metal Forming Presses” Final Report AFMI-TR-79-4168 Air Force Materials Laboratory Wright-Patterson Air Force Base, Ohio 1979
- Ragab, A.R. 1986 Abbas, A.T. Assessment of Work-Hardening Characteristics and Limit Strains of Anisotropic Aluminum Sheets in Biaxial Stretching J. of Engineering Materials and technology 108 1986 250 255
- Raghupathi, P.S. 1983 Karima, M Akgerman, N Altan, T. A Simplified Approach To Calculate Springback In Brake Bending Proc. NAMRC XI May 1983 165 171
- Tozawa, Y. 1990 Forming Technology for Raising the Accuracy of Sheet-Formed Products J. Materials Processing Technology 22 1990 343 351
- Wang, C.T. 1992 Kinzel, G. Altan, T. Plane Strain Sheet Bending - Fundamentals and Applications: Part I - Elementary Bending Theory, and Part II - Advanced Topics Report No. ERC/NSM-S-15-92 NSF Engineering Research Center for Net Shape Manufacturing, The Ohio State University
- Wang, N.-M. 1984 Predicting the Effect of Die Gap on Flange Springback Proc. 13th IDDRG Cong. Melbourne, Australia 1984 133 147
- Yang, M 1990 Shima, S. Development of an Intelligent V-Bending Process with a Feedforward Control System, in Advanced Technology of Plasticity 3 1483 1488
- Yang, M 1991 Shima, S. Development of New Bending Die - Development of an Intelligent Bending System Journal of JJSTP 32 370 1376 1382