New drawbead tester and numerical analysis of drawbead closure force

Abstract

Currently, a great deal of controversy exists regarding the real forces generated in drawbeads during sheet metal forming processes. The present work focuses on the analysis of the uplift force. First, a detailed literature review is carried out to analyse previous experimental procedures used to measure uplift forces. It is found that previous setups do not perfectly replicate the real geometry of industrial drawbeads. In order to obtain reliable forces, an experimental drawbead tester capable of adequately replicating industrial drawbeads is developed. Later, a variety of steels ranging from mild steels to 3rd-generation ultra-high-strength steels are tested and reliable uplift and also restraining force values are obtained. The main purpose of the work is to share with the research community reliable experimental data that allows precise evaluation of the accuracy of current drawbead models and that supports the generation of new numerical and equivalent drawbead models. In parallel to the experimental procedure, a step forward in the understanding of the drawbead closing phenomena is also achieved through a 2D numerical model. The main purpose of the model is to identify the variables that greatly affect uplift force. Going beyond previous studies, in which some variables were analysed, the present work covers, in a holistic manner, the impact that material properties, the geometry of drawbeads and contact behaviour between sheet and drawbead have on the uplift force. It is determined that surprisingly minor geometrical deviations in the drawbead nominal geometry have a large impact on the uplift force.

Analysis of the Frictional Performance of AW-5251 Aluminium Alloy Sheets Using the Random Forest Machine Learning Algorithm and Multilayer Perceptron

“…It was concluded that when a higher force was applied to the draw bead, a higher restraining force was generated. Gil et al [26] proposed a model to identify the main variables affecting the uplift force in the drawbead region. They found that minor geometrical deviations in the drawbead geometry significantly affect the uplift force.…”

Friction Behaviour of 6082-T6 Aluminium Alloy Sheets in a Strip Draw Tribological Test

“…In order to determine the friction and wear of materials, the following types of tests and tribometers may be used: (a) strip drawing test with flat [ 19 , 20 ] and (b) rounded [ 21 ] (c) countersamples, (d) bending-under-tension test [ 22 , 23 ], (e) draw-bead test [ 24 , 25 ], and (f) ball-on-disc [ 26 ], (g) block-on-disc [ 27 ], (h) pin-on-ring [ 28 ], and (i) pin-on-disc tribometers [ 29 , 30 ]. Most of the studies, the results of which can be found in the literature, indicate the susceptibility of aluminium sheets to galling and intensification of the flattening mechanism.…”