Prediction of Earing of Aluminium Sheets from {111} Pole Figures
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HYSICAL PROPERTIES OF CRYSTALS
Prediction of Earing of Aluminium Sheets from {111} Pole Figures M. Benkea,* a
Institute of Physical Metallurgy, Metalforming and Nanotechnology, University of Miskolc, Miskolc, Hungary *e-mail: [email protected] Received May 18, 2020; revised May 28, 2020; accepted June 2, 2020
Abstract—Crystallographic texture causes anisotropic formability of metal sheets, which results in the formation of uneven cup heights during deep drawing, called earing. Over the past decades, several methods had been developed to predict the earing behaviour of aluminium alloys. These methods are rather complex and can only be applied within strict sheet thickness ranges. Recently, a simple method has been presented and successfully applied on different sheet thicknesses. The method relies solely on {h00} type pole figure data. However, it is desired to be able to predict earing from other reflections as well. In this manuscript, a method which predicts the type and magnitude of earing only from the data of {111} pole figure measurements, is presented. The method was applied on a series of 0.3 and 3 mm thick cold rolled and annealed aluminium sheets, exhibiting rolling and recrystallization textures and the combination of these. It is shown that the proposed method gave similar results to those of deep drawing tests. It is concluded that using the presented method, the earing of aluminium sheets can be characterized solely from {111} pole figure measurement data. DOI: 10.1134/S1063774520060061
INTRODUCTION Mechanical anisotropy of aluminium sheets is governed by crystallographic texture. If the texture is strong, mechanical properties such as formability will have a strong dependence on the direction of inspection. This is usually characterized by deep drawing tests during which circular samples, called blanks are forced in the shape of cups. Strong texture results uneven cup heights, where height maximums, called ears, and throughs follow each other. In case of fourfold earing, ears appear in the 45° + (n × 90°) (n = 0, 1, 2, 3) with respect to in the rolling direction (RD) if the sheet exhibits cold rolling texture, while in the RD + (n × 90°) directions if recrystallization texture is developed [1, 2]. It is impossible to achieve a complete absence of ears, but by the combination of annealing texture and deformation texture, an optimal case with minimal earing can be achieved [2–5]. The simplified picture of this optimal case is the idealized earing-free case. Besides deep drawing tests, several calculation methods had been developed to predict earing. These methods require input data which either originates from mechanical tests [6, 7] or texture examinations [8, 9]. Nowadays, finite element methods are preferred to reduce costs [10–13]. Most of these methods are based on idealized theoretical material behaviour, or the combination of some of those. Thus, the calculation process is quite complex, and, in most cases,
their applicability is limited to certain geometries. Recently, a new approach w
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