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A Static Approach for Determination of Bending Force and Spring-Back during Punching Process

Manar Abdelhakim Eltantawie1 and Eldesoky Elsayed Elsoaly2
Higher Technological Institute-Mechanical Engineering Department, PO Box.4, 6th of October-Giza-12585, Egypt.

Abstract—Bending is a common metal working process used in sheet-metal forming, such as parts of automobiles, aircraft and ships. In addition, bending is used in many sheet metal forming, such as deep drawing and stamping processes. Bending process is usually followed by some elastic recovery upon unloading, called spring-back. A static approach is described to determine new formulas for the bending force, the shift of neutral-axis and the value of spring-back, in V-die bending process. Due to friction force between the sheet-metal and the die edge, a variable neutral-axis shift is deduced in the elastic zone of the bending length. The amount of shift is, rapidly, decreased with the distance starting from the die edge, along the bending length. Based on the reflexive action in elastic zone, and the residual stresses, in elastic-plastic zone, the amount of spring-back is derived. As a case study, the obtained expressions are applied to compare the values of bending force and the spring-back in, previously, published experimental study on V-die bending conducted on two different die-angles 90° and 120°. The comparison shows that the values of bending force and the spring-back, obtained by the present work, are, in general slightly under-estimating.

Index Terms—Statics, Punching, Spring-back, Neutral axis, Yield, Elasto-plastic, Residual stress

Cite: Manar Abdelhakim Eltantawie and Eldesoky Elsayed Elsoaly, "A Static Approach for Determination of Bending Force and Spring-Back during Punching Process," International Journal of Mechanical Engineering and Robotics Research, Vol.1, No.3, pp. 192-202, October 2012.