ABSTRACT:Springback is an implicit phenomenon in most forming processes and needs to be accounted for in the design of forming tools. This is essential in order to limit the number of iterations required during the design and fabrication of forming tools and dies. This work presents a closed form solution for predicting springback in bending including hardening effect. Springback was also determined using experimental testing. The results obtained are compared with analytical results and the influence of hardening on springback is analysed. INTRODUCTIONSheet metal forming is one of the most important manufacturing processes for mass production in industry. Several sheet-forming processes include bending. In these processes, plastic deformation is followed by some elastic recovery upon unloading. This change in shape is known as springback and its extent depends on material properties, geometry and tooling dimensions. Springback can be particularly significant in structures, panels and components formed into large radii.Springback results in the deviation of a component from a desired shape after the forming load is removed. This means that additional geometric adjustments have to be made to account for it in the design of forming tools and dies. The phenomenon has been analysed using different procedures over the last few decades. Early works by researchers developed correction curves using empirical relations based on experimental testing [1-2]. Many analytical solutions have subsequently been derived [3][4][5][6]. A good review of these previous works can be found in references [7][8][9]. Other workers have used the finite element method [10][11].The earliest attempt to find an analytical solution for springback correction was started by Sturm and Fletcher [3] in the aircraft industry in the early 1940s. The solution developed was however cumbersome to apply. It requires explicit determination of distances from the neutral plane to beam surfaces as well as surface stresses. Schroeder [5] presented another analytical solution in 1943 but this was also rather complex to implement. It was not until the late 1950s when by examining narrow beams of an elastic-perfectly plastic material that Gardiner [6] developed a solution for determining springback after bending that was far simpler to use. Gardiner's formula has been embraced by the metals forming community for decades as a very good approximation for the calculation of springback.As highlighted in the foregoing, Gardiner's solution assumes elastic perfectly plastic material behaviour. Most engineering materials however exhibit strain hardening with significant increase in strength in the post yield regime. It will therefore be helpful to obtain a more general and accurate closed form equation for predicting springback that account for this factor. This work presents a closed form solution for predicting springback in bending including hardening effect. Springback was also determined by experimental testing and the results obtained are compared with analytical...

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In the present study the stress concentration factor by the finite element method in a round bar grooved axially under tension, a stepped flat plate subjected to bending and a stepped round bar subjected to torsion can be found. The stress concentration factor was obtained in the simulation laboratory through the commercial software ANSYS Workbench® version 19 and Autodesk Inventor 2016® and they were compared with the experimental curves enunciated in Peterson book, finding similarities up to 0.02% between simulation and experimental methods; and 0.3% between both pieces of software.