Dimpling process in cold roll metal forming by finite element modelling and experimental validation

Abstract

(2014) Dimpling process in cold roll metal forming by finite element modelling and experimental validation. Journal of Manufacturing Processes, 16 (3). pp. 363-372. ISSN 1526-6125 This version is available from Sussex Research Online: http://sro.sussex.ac.uk/48964/ This document is made available in accordance with publisher policies and may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the URL above for details on accessing the published version. Copyright and reuse:Sussex Research Online is a digital repository of the research output of the University.Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable, the material made available in SRO has been checked for eligibility before being made available.Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. AbstractThe dimpling process is a novel cold-roll forming process that involves dimpling of a rolled flat strip prior to the roll forming operation. This is a process undertaken to enhance the material properties and subsequent products' structural performance while maintaining a minimum strip thickness. In order to understand the complex and interrelated nonlinear changes in contact, geometry and material properties that occur in the process, it is necessary to accurately simulate the process and validate through physical tests. In this paper, 3D non-linear finite element analysis was employed to simulate the dimpling process and mechanical testing of the subsequent dimpled sheets, in which the dimple geometry and material properties data were directly transferred from the dimpling process. Physical measurements, tensile and bending tests on dimpled sheet steel were conducted to evaluate the simulation results. Simulation of the dimpling process identified the amount of non-uniform plastic strain introduced and the manner in which this was distributed through the sheet. The plastic strain resulted in strain hardening which could correlate to the increase in the strength of the dimpled steel when compared to plain steel originating from the same coil material. A parametric study revealed that the amount of plastic strain depends upon on the process parameters such as friction and overlapping gap between the two forming rolls. The results derived from simulations of the tensile and bending tests were in good agreement with the experimental ones. The validation indicates that the finite element analysis was able to successfully simulate the dimpling process and me...

Experimental and numerical study on crashworthiness of cold-formed dimpled steel columns

“…In reality, the thickness of dimpled plate slightly varies at different locations around the dimple valley [24]. However, it was assumed that the thickness was uniform across the entire plate.…”

“…The process uses a pair of rollers with rows of specially shaped teeth that form the dimple shapes from both sides of the plain sheet, as shown in Figure 1 [24]. The dimpled sheet can then be progressively formed into a desired profile by passing through a series of rolls, arranged in tandem, or by press braking.…”

“…The dimpled sheet can then be progressively formed into a desired profile by passing through a series of rolls, arranged in tandem, or by press braking. It has been reported through experimental tests and numerical simulations that the strength of dimpled samples was significantly greater than plain samples originating from the same coil material [24][25][26][27][28][29]. The greater strength of dimpled samples is caused mainly by the work hardening of the material during the dimpling process.…”

“…1. The UltraSTEEL process and dimpled steel sheet [24] This paper aims to investigate the finite element modelling method to accurately predict the energy absorption characteristics of dimpled thin-walled columns under dynamic axial crushing loads, as well as analyse the effect of the dimple forming parameters in the UltraSTEEL ® process. To achieve this aim, both numerical and experimental studies were carried out on plain and dimpled open-section thin-walled columns under two different impact velocities.…”

Behaviour of cold-formed dimpled columns under lateral impact

“…Dimpled sheets are then formed into desired profiles by passing through a series of rolls or press braking. Several previous numerical and experimental research has revealed that the strengths of dimpled steel sheets are significantly greater than those of the original plain steel sheets [21][22][23][24][25][26][27]. The increase in strength is mainly due to work hardening developed throughout the forming process.…”