Journal of Manufacturing Processes 32 (2018) 513–521 Contents lists available at ScienceDirect Journal of Manufacturing Processes j ourna l h o me page: www.elsevier.com/locate/manpro Effect of the forming method on part shape quality in cold roll forming high strength Ti-6Al-4V sheet Ossama Mamdouh Badr a , Bernard Rolfe b , Matthias Weiss a,∗ a Institute for Frontier Materials, Deakin University, Waurn Ponds, Pigdons Road, VIC, Australia b School of Engineering, Deakin University, Waurn Ponds, Pigdons Road, VIC, Australia a r t i c l e i n f o Article history: Received 5 June 2017 Received in revised form 16 March 2018 Accepted 18 March 2018 Keywords: Ti-6Al-4V Roll forming Springback Longitudinal bow a b s t r a c t High strength titanium alloy sheet, in particular Ti-6Al-4V, is used for structural applications; roll forming has been found to be an appropriate cold forming process for the manufacture of long components in Ti-6Al-4V. Roll forming Ti-6Al-4V at room temperature requires extensive FEA-assisted process develop- ment and optimisation to keep springback and part shape defects to a minimum. Currently the material behaviour of Ti-6Al-4V in the roll forming process is not well understood. Two major roll forming approaches, the constant bend radius and the constant arc length method, are used in roll forming but the effect of each approach on springback or final part shape in high strength sheet materials such as Ti-6Al-4V is not well documented. A fundamental understanding of this will enable rapid and reliable process design for the cold roll forming of high strength titanium alloys. The primary aim of this study is to explore the potential use of different roll forming methods to reduce springback and part shape defects in the cold roll forming of Ti-6Al-4V sheet and to develop a deeper understanding of the material behaviour of Ti-6Al-4V in the process. For this, experimental roll forming trials and their simulation are performed and a novel constitutive material model based on the homogeneous anisotropic hardening (HAH) approach is used to represent the forming behaviour of Ti- 6Al-4V under cold forming conditions. The experimental and numerical results indicate that the constant radius forming method leads to fewer shape defects in the process and reduced springback. A detailed discussion is provided explaining in part the observed trends. © 2018 Published by Elsevier Ltd on behalf of The Society of Manufacturing Engineers. 1. Introduction High strength titanium sheet such as Ti-6Al-4V offers desirable characteristics such as high specific strength and structural stiff- ness with excellent heat and corrosion resistance [1]. Ti-6Al-4V is increasingly used in aerospace [2], marine [3] and automotive industries [4] but given its high strength and limited formability it generally has to be formed at elevated temperature which results in high manufacturing costs [5]. Recently Badr et al. [6] experimen- tally showed that Ti-6Al-4V sheet could be cold roll formed; in this process, a metal strip is gradually formed into the required profile by passing it through a series of contoured rolls. The same study also revealed that roll forming Ti-6Al-4V at room temperature creates challenges in the controlling of springback and part shape defects. At present, there is only a limited understanding of the behaviour of Ti-6Al-4V in cold roll forming. ∗ Corresponding author. E-mail address: matthias.weiss@deakin.edu.au (M. Weiss). Springback in roll forming has been found to be lower compared with that in simple bending operations and this has been linked to the incremental nature of the process [7] and to the effect of redundant deformation [8]. Springback in roll forming increases with material strength [9], the ratio of the bend radius to the sheet thickness [10] and decreasing elastic modulus of the material [11]. There is also an effect of the process and tooling design and recent studies suggest that springback in roll forming decreases with the number of forming passes used [12]. In roll forming, the material fibers at the strip edges travel a longer distance than those in the web leading to longitudinal edge strain [8]. If this strain exceeds the elastic limit of the material, shape defects such as edge ripple, bow and twist result. Previous studies suggested that the likelihood of permanent longitudinal deformation in the strip edge reduces with increasing material strength; this leads to reduced forming defects in form of bow when forming higher strength steels [13,14] or high strength Ti- 6Al-4V titanium compared with softer sheet metal. Additionally, longitudinal edge strain depends heavily on the component geom- etry and generally decreases with increasing flange length of the https://doi.org/10.1016/j.jmapro.2018.03.022 1526-6125/© 2018 Published by Elsevier Ltd on behalf of The Society of Manufacturing Engineers.