Numerical and experimental analysis of wrinkling during the cup drawing of an AA5042 aluminium alloy

Abstract

The recent trend to reduce the thickness of metallic sheets used in forming processes strongly increases the likelihood of the occurrence of wrinkling. Thus, in order to obtain defect-free components, the prediction of this kind of defect becomes extremely important in the tool design and selection of process parameters. In this study, the sheet metal forming process proposed as a benchmark in the Numisheet 2014 conference is selected to analyse the influence of the tool geometry on wrinkling behaviour, as well as the reliability of the developed numerical model. The side-wall wrinkling during the deep drawing process of a cylindrical cup in AA5042 aluminium alloy is investigated through finite element simulation and experimental measurements. The material plastic anisotropy is modelled with an advanced yield criterion beyond the isotropic (von Mises) material behaviour. The results show that the shape of the wrinkles predicted by the numerical model is strongly affected by the finite element mesh used in the blank discretization. The accurate modelling of the plastic anisotropy of the aluminium alloy yields numerical results that are in good agreement with the experiments, particularly the shape and location of the wrinkles. The predicted punch force evolution is strongly influenced by the friction coefficient used in the model. Moreover, the two punch geometries provide drawn cups with different wrinkle waves, mainly differing in amplitude.

An analytical investigation on the wrinkling of aluminium alloys during stamping using macro-scale structural tooling surfaces

“…The dimensions of tools were consistent with experimental setups. The mesh of blank is extremely important for guaranteeing the accuracy of simulation [28]. In this study, the mesh of test-piece material was selected as shell element, Belytschko-Tsay, with a fixed size at 4 mm.…”

Prediction of wrinkling and springback in sheet metal forming

“…Since the prediction of wrinkling phenomena in sheet metal forming simulation requires a fine mesh [6], a regular mesh is adopted in the Oxy plane (element size of 1.0 mm in the central region), as shown in Figure 5. The discretization of the blank comprises two layers of finite elements through the thickness, which enable an accurate prediction of the forming forces and the springback [13].…”

“…Nevertheless, these material are more prone to develop geometrical defects, namely springback [5]. Another important geometrical defect arising in sheet metal forming is the wrinkling behaviour, which results from the instability under compressive stresses [6].…”

“…Despite the many advances in the numerical simulation tools development, the accurate prediction of geometrical defects still represents a challenge for the simulation [12]. For instance, it is known that wrinkling prediction is strongly affected by the finite element discretization [6]. Also, springback prediction is influenced by the model selected to describe the material kinematic hardening behaviour [13].…”

Uncertainty analysis of deep drawing using surrogate model based probabilistic method

“…The main defects in deep drawing are wrinkling, fracture (or tearing), earring, and surface scratches. Generally, wrinkling occurs due to compressive stress in the circumferential direction, fracture occurs because of high tensile stresses that cause thinning and failure of the metal in the cup wall [3], earring caused by materials anisotropy [4] which is due to the directionality of plastic properties produced by rolling and other primary working process, and surface scratches can be seen on the drawn part if the punch and die are not smooth or if the lubrication of the process is poor. Therefore, in order to achieve drawn parts in desired shape and without defects, process parameters should be appropriately chosen and set, which can be obtained through simulation and optimization strategy [5].…”