Springback Estimation in the Hydroforming Process of UNS A92024-T3 Aluminum Alloy by FEM Simulations

Abstract

The production of metal parts manufactured through the hydroforming process is strongly affected by the difficulty in predicting the elastic recovery (springback) of the material. In addition, the formation of wrinkles and crack growth should be avoided. Manual cold work is widely employed in industry to obtain the final shape of the manufactured parts. Therefore, an accurate springback estimation is of high interest to reduce the overall time of manufacturing and also to decrease the manual rectification stage. A working procedure based on finite element simulations (FEM) was developed to estimate the elastic recovery and predict the final morphology of UNS A92024-T3 aluminum alloy pieces after forming. Experimental results of real hydroformed parts were compared with the results obtained in simulations performed with PAM-STAMP software. The influence of different experimental parameters on the forming processes was also analyzed, such as the material properties, the rolling direction of sheet metal, or the hardening criteria employed to characterize the plastic region of the alloy. Results obtained in the present work show an excellent agreement between real and simulated tests, the maximum morphology deviations being less than the thickness of parts (2.5 mm). FEM simulations have become a suitable and mature tool that allows the prediction of the pieces springback, a precise material characterization being required to obtain reliable results.This process has the main advantage of being relatively quick, being also carried out at room temperature. These two factors make it a relatively cheap and convenient process. However, it also presents several inherent technical disadvantages, such as the development of defects (cracks or wrinkles) in areas with high plastic deformation, and the elastic recovery (springback) after the application of pressure. The elastic recovery must be estimated and taken into account, as the final shape of the formed part should be as close as possible to the design part [1]. Therefore, in order to manufacture parts with curved shapes, the dies used must have a more pronounced morphology than the design part, with the aim of compensating the springback. In many cases, the dies geometry is estimated taking into account the intuition and practical experience of the operators, or by means of trial-error tests, which constitute significant losses of time and material, decreasing the overall production rate.As stated before, the hydroforming process involves the generation of residual stresses, high elastic recovery, and the possibility of defects formation, such as wrinkles and cracks. The uncertainty associated with the low precision in the springback estimation usually generates critical variations between machined and design parts, which leads to subsequent manual adjustment of the geometry of the workpiece/part. Most of the studies working on this topic are focused on flange forming [2-4]. One of the emerging methodologies to reduce the possible defects caused in the manufacture of part...

A 3D Non-Linear FE Model and Optimization of Cavity Die Sheet Hydroforming Process

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Springback Analysis of AA5754 under Warm Stamping Conditions

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