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Short communication Wrinkling behaviour of interstitial free steel sheets when drawn through tapered dies R. Narayanasamy a,*, C. Sathiya Narayananb a Department of Production Engineering, National Institute of Technology, Tiruchirappalli 620 015, Tamilnadu, India b Department of Production Engineering, J.J. College of Engineering and Technology, Tiruchirappalli 620 009, Tamilnadu, India Received 4 January 2005; accepted 8 July 2005 Available online 2 September 2005 Abstract Wrinkling is a mode of failure commonly observed in the forming of sheet metals during deep draw operation. An experimental study on wrinkling behaviour of interstitial free (IF) steels through conical and tractrix dies is discussed in this paper. Mechanical properties and drawability parameters of these IF steels were determined and they were correlated with the wrinkling behaviour. The limiting draw ratio (LDR) of these steel sheets were related to the sheet thickness, the ratio of punch diameter to sheet thickness, the normal anisotropy and the non-dimensional parameter (which involves punch diameter, sheet thickness, normal anisotropy and strain hardening exponent). The above study of wrinkling behaviour was carried out under two diff erent conditions namely lubri- cated and non-lubricated and they were compared. From the study, it is clear that the LDR could be related to the above-mentioned parameters. ? 2005 Elsevier Ltd. All rights reserved. Keywords: IF steel; Wrinkling; Conical die; Tractrix die 1. Introduction Wrinkles are often observed in sheet metal forming processes. The presence of wrinkles is unacceptable for the fi nal product. In the recent years, the thinner guage sheets with high strength are used in order to reduce the weight of the products which leads to the formation of buckles and wrinkles during the forming operations. The researchers aim to avoid such wrinkles during sheet metal forming. Hill?s 1 bifurication criterion can be used to predict the formation of wrinkles. The onset of fl ange wrinkling was analysed by Needleman 2 by using Swift cup test. Several theoretical and experimen- tal works have been carried out on the wrinkling behav- iour of diff erent materials under diff erent conditions. Kim and Son 3 evaluated wrinkling limit diagram (WLD) of anisotropic sheet by numerical analysis. Joao Pedro de Magalhaes Correia and Gerard Ferron 4 investigated the infl uence of plastic anisotropy on the onset of wrinkling. Narayanasamy and Sowerby 5 examined the wrinkling behaviour of stainless steel 304 grade, dual phase steel and aluminium killed drawing quality steel. In this work, the wrinkling behaviour of interstitialfree(IF)steelswiththickness0.6 mm, 0.85 mm coated and non-coated, 0.9, 1.2 and 1.6 mm have been studied using conical die and tratrix die using a double action hydraulic press of capacity 2000 kN. Interstitial free steels are newly developed steels having verymuchlessamountofcarbonandnitrogen. Although aluminium alloys are used for automobiles applications due to their lightweight, which contributes 0261-3069/$ - see front matter ? 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2005.07.005 * Corresponding author. Tel.: +91 0431 2501801; fax: +91 0431 2500133. E-mail addresses: (R. Narayanasamy), csathiya narayananyahoo.co.in (C.S. Narayanan). Materials and Design 28 (2007) 254259 Materials 6:23649. 2 Triantafyllidis N, Needleman A. An analysis of wrinkling in the Swift cup test. J Eng Mater Technol 1980;102:2418. 3 Kim Y, Son Y. Study on wrinkling limit diagram of anisotropic sheet metals. J Mater Process Tech 2000;97:8894. 4 de Magalhaes Correia JP, Ferron G. Wrinkling predictions in the deep drawing process of anisotropic metal sheets. J Mater Process Technol 2002;128:17890. 5 Narayanasamy R, Sowerby R. Forming behaviour of some sheet steel materials when drawn through a conical die. J Mater Process Technol 1993;39:4353. 6 Uenishi A, Teodosiu C. Constitutive modelling of the high strain ratebehaviourofinterstitialfreesteel.IntJPlasticity 2004;20:91536. 7 Uenishi A, Teodosiu C. Solid solution softening at high strain rates in Si and/or Mn added interstitial free Steels. Acta Mater 2003;51:443746. 8 Feliu Jr. S, Perez-Revenga, ML. Eff ect of alloying elements (Ti, Nb, Mn and P) and the water vapour content in the annealing I.F. Steels y = 2E-05x2 + 0.0136x - 0.2873 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 507090110130150170190210230250 Initial Blank Diameter / Sheet Thickness - Plastic Strain Increment ratio (dr /d ) FORD INDIA LTD. TISCO. CONICAL DIE DEEP DRAW WRINKLING AREA SAFE AREA Fig. 11. Variation of plastic strain increment ratio with (dp/t0) in conical die. I.F. Steels y = -0.0007x2 + 0.117x - 3.5284 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 556065707580859095100 Initial Blank Diameter / Sheet Thickness - TISCO. TRACTRIX DIE DEEP DRAW ( PRESTRAINED ) WRINKLING AREA SAFE AREA Plastic Strain Increment ratio (dr /d ) Fig. 13. Variation of plastic strain increment ratio with (dp/t0) for prestrained condition sheet in tractrix die. I.F. Steels y = -0. 0001 x2 + 0. 0325x - 0. 6541 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 507090110130150170190210230250 Initial Blank Diameter/ Sheet Thickness - FORD INDIA LTD. TISCO. TRACTRIX DIE DEEP DRAW WRINKLING AREA SAFE AREA Plastic Strain Increment ratio (dr /d ) Fig. 12. Variation of plastic strain increment ratio with (dp/t0) in tractrix die. 258R. Narayanasamy, C.S. Narayanan / Materials and Design 2