Formability Analysis of Crca-IS2 Sheet to Eliminates the Defects during Deep Draw

Transcription

1 Journal of Graphc Era Unversty ISSN: (Prnt), (Onlne) Formablty Analyss of Crca-IS2 Sheet to Elmnates the Defects durng Deep Draw Satpal Sngh 1, Gurmeet Sngh 2*, Smardeep Sngh 3 1 hapar Polytechnc College, Patala, Punjab Inda *2 hapar Insttute of Engneerng and echnology Unversty, Patala, Punjab Inda 3 Honda Motorcycles and Scooters Inda Pvt. Ltd, Gurgaon, Inda Correspondng author: gurmeet.sngh@thapar.edu (Receved August 9, 2016; Accepted November 17, 2016) Abstract Metal formng operatons n ndustres are performed by the sheet metal processes. In sheet metal work deep drawng plays a major role to form the desred shapes. Improper desgn process leads to defected parts whch are not acceptable due to ergonomcs as well as aesthetcs. Enormous defects durng drawng have been dscussed n the lterature. FEA of sheet metal drawng was performed by usng a blank. Durng the drawng operaton wrnklng and tearng were observed expermentally. FEA as an effectve tool has been concluded for ths technque. he results wll help n optmzng the process by changng the nput parameters and help the ndustry to perform ht and tral on smulator rather than vrtual envronment. Keywords- Fnte Element Analyss (FEA), Sheet Metal Bendng, Drawng, Smulaton, Wrnklng. 1. Introducton Sheet metal s a metal formng process n whch a sheet s transformed nto preferred shape by means of de and punch. Sheet metal parts are used n numerous applcatons where aesthetc look s more domnant compared to propertes of materals for example panels, bonnet, etc. So, any knd of defects lke wrnkles or tearng are unacceptable. Varous mportant parameters whch are the ntegral part of drawng operaton are blank holder force, punch de clearance, draw bead desgn, corner radus, de entry radus, coeffcent of frcton, etc. (Yang et al., 2008; Sngh and Agnhotr, 2015). In sheet metal deep drawng s an ntegral part of the metal formng to produce axs symmetrcal drawng (Sen and Kurgan, 2016) or axsymmetrcal rectangular drawng (Kang et al., 2010). An optmze de desgn s requred so that the deep drawng operaton can be executed successfully. Certan equatons are avalable to calculate the blank holder force requred, but for some parts the exact classfcaton cannot be done because of some complex desgn. It has been detected from lterature that the blank holder force plays a major role on the metal dstrbuton durng the deep draw. If blank holder of large value s gven to blank metal resst flowng wherever low forces support the flow of metal. A smlar knd of pattern s observed n the case of frcton coeffcent (Ramezan and Rpn, 2012; Reddy et al., 2012a). he de entry radus, corner radus and the punch de clearance are some parameters whch further 52

2 Journal of Graphc Era Unversty ISSN: (Prnt), (Onlne) affect the flow of metal (Özek and Bal, 2009; Aln et al., 2013). Complex shapes of the draw bead have a large mpact on the dstrbuton of metal. Optmal values of the parameters are mportant to properly desgn the de as well as the process for the successful drawng operaton (We et al., 2008). A proper draw must be excluded from the wrnkles nor should t tear out durng formng. An optmum sze of blank can be used to produce a part wth mnmum of materal (Wang et al., 2009; Reddy et al., 2012b). In a nutshell, f the desgn of the de s properly made and the process s studed before the formng can result nto a defect free part. For the analyss of the drawng operatons FEA s an mportant tool (Altnbalk and onka, 2012). o reduce the computatonal cost and expenses n the smulatons sx sgma approach has been used on the bass of CAE (Madake et al., 2013; Mayavan and Karthkeyan, 2013). Some other expert systems have also desgned to valdate feasblty of the producton and the de desgn. (Vosnakos and Gannakaks, 2013; Wf and Mosallam, 2007). 2. Materal and Model An ndustral panel whch s small bumper was taken for case study of sheet metal drawng process. he specfcaton of the materal of sheet blank was Extra Deep Draw grade Cold Rolled Closed Annealed IS(2): 440x380x4.00 mm he flow curve defnng the materal was taken as σ = max [S, C(ε) N ] where σ s flow stress, S & C are constants, ε s stran and N s stran exponent. he Coulomb frcton model F =μn, s used where F s the frctonal force, μ s the coeffcent of frcton and N s the normal load n contact. hs model defnes the frcton n mechancal contacts. 3. Fnte Element Model FEA works on the bass of quantum mechancs and n case of sheet metal; t s a non-lnear problem. o formulate the proper functonng of the problem varatonal approach s appled and t depends on specfc equatons. It s a necessty of the admssble veloctes and the compatblty, ncompressblty and boundary condtons. he most basc form of consttutve equaton s descrbed n terms of vrtual dsplacement vector δu. pu udv Ku udv f f dv f udv f uds b s f u ds (1) V V V V S C c Inerta force s defned by V pu u dv where ρ s the mass densty of sheet and µ s acceleraton vector over volume V. Dampng force defned by V Ku u dv 53

3 Journal of Graphc Era Unversty ISSN: (Prnt), (Onlne) where k s dampng factor and u s velocty vector over volume V. Internal nodal force vector s the vrtual work done by stresses and s gven by V dv f f where σj s Cauchy stress tensor and s the vrtual stran vector due to vrtual dsplacement vector u. External nodal force p dv K dv F ) U fb dv fs ds ( fc ds (2) V V V S C where M s the mass matrx, C s the dampng matrx, F s the nternal node force vector, Fe s the external node force vector and Fc s the contact force vector. he speed of the sheet metal operaton s hgh so the nerta and the dampng effect can be cancelled out. he complex partal dfferental equatons are dscretzed nto large sparse lnear systems, whch can be solved for solutons. Marc solver was utlzed takng nto consderaton the nonlnearty of the system. It uses Updated Lagrangan formulaton to gve the ncremental form of soluton because of the large deformaton nvolved n the sheet metal formng operaton. 4. Numercal Smulaton For smulaton on smulator, the des and the sheet blank models were desgned n sold works 2012 and then saved n the form of parasold fle. he sheet was meshed usng sheet mesh element wth 3 mm element sze. Automatc contact procedure n ANSYS 15.0 LS DYNA was assumed for the complex nteracton between the punch, blank and de. For rgd-flexble (tool set-blank) contact, 3D 8-node quadrlateral target element (ARGE 17.0) was used to represent 3D target (tool set) surface whch was assocated wth the deformable body (blank) represented by 3D 8-node contact element (CONA174). Conventonal shell elements have to be appled wth the specal care where n sgnfcant devaton from plane-stress behavour s expected. he sheet mesh element automatcally detects the thckness of sheet and dvdes t nto optmal mesh wth 3D elements whch gves accurate results and a good predcton of thckness varatons. he followng table (able 1) gves the values of other parameters consdered for drawng operaton. After the materal propertes, meshng and loadng condtons, the analyss was performed. In analyss the total deformaton and total stran effects s to be analysed. Usng the actual loadng values was also assgned.e. when the mpact loadng rate s appled on the punch the wrnkles generate. he velocty wth whch the punch moves down towards the blank holder and the pressure on the blank as measured was also assgned. Velocty 75 mm/sec and rate of loadng 470 MPA was assgned. he analyss shows the wrnkles on the same area. Fgure 1, 2, 3 and 4 shows the analyss of the mpact loadng condtons. he results of smulaton are gven 54

4 Journal of Graphc Era Unversty ISSN: (Prnt), (Onlne) below. By changng the loadng condtons, punch velocty was assgned as 15 mm/sec and load on the blank holder was assgned as 470 MPa. So the analyss was performed and the wrnkles were elmnated and draw was properly seen. he speed of the punch s changed and found that the proper draw was obtaned. It was observed n Fgure 4 that the thckness dstrbuton of the metal was farly gradual at most of the regons. But, the local thckenng of metal at the corners mpled that the pressure from the punch s mportant part. he effectve stress was maxmum when the speed of the punch was more than requred. When the speed of the punch was optmzed the wrnkles dsappeared and the part can be easly drawn. So the smulaton can save tme of the producton and also expendture of the de changes. So, t may be concluded that the smulaton results are vald. 5. Concluson It can be analysed that the compressve forces produced durng the drawng operaton were unstable whch resulted n wrnkles. hs mples that the materal was not properly draw due to mproper pressure on the part. he materal dstrbuton durng drawng could be controlled through a proper pressure on the sheet. he parameters can be vared to prevent the thckenng or thnnng of the materal n any part of the panel. Further, the ansotropy of the materal has not been taken nto consderaton. FEA has successfully smulated the drawng operaton and can be used for the optmzaton of the process savng a lots of tme, money and labour expendture. S.No. Parameters Value used 1 Blankholder Force 150 KN 2 Frcton Coeffcent De Entry Radus 8 mm 4 Drawbead Heght 4 mm 5 De Punch Clearance 2 mm 6 Corner Radus 20 mm able 1. Value of parameters usng durng the deep draw operaton Wrnkles on the part Fgure 1. Shows the wrnkles on the part 55

5 Journal of Graphc Era Unversty ISSN: (Prnt), (Onlne) Wrnkles Fgure 2. Shows the wrnkles durng smulaton Wrnkles Fgure 3. Shows the wrnkles durng smulaton Wrnkles elmnated Fgure 4. Shows the wrnkles removed 56

6 Journal of Graphc Era Unversty ISSN: (Prnt), (Onlne) References Aln, P., Ioan, M., Ioan, R., & Florn, B. (2013). Parameters nfluence on wrnklng n deep drawng cylndrcal cups. Revsta de ehnolog Neconventonale, 17(3), Altnbalk,., & onka, A. (2012). Numercal and expermental study of sheet thckness varaton n deep drawng processes. Internatonal Journal of Modern Manufacturng echnologes, 4(2), Kang, B. S., Song, W. J., & Ku,. W. (2010). Study on process parameters and ts analytc applcaton for nonaxsymmetrc rectangular cup of multstage deep drawng process usng low carbon thn steel sheet. he Internatonal Journal of Advanced Manufacturng echnology, 49(9), Madake, M. A. D., Nak, D. V. R., & Kulkarn, M. S. S. (2013). Development of a sheet-metal component wth a formng de usng CAE software tools (Hyper form) for desgn valdaton and mprovement. Internatonal Journal of Modern Engneerng Research, 3(3), Mayavan,., & Karthkeyan, L. (2013). Expermental and fnte element studes on formablty of low carbon steel sheets usng deep drawng. Internatonal Journal of Engneerng and echnology, 5(1), Özek, C., & Bal, M. (2009). he effect of de/blank holder and punch raduses on lmt drawng rato n angular deep-drawng des. he Internatonal Journal of Advanced Manufacturng echnology, 40(11), Ramezan, M., & Rpn, Z. M. (2012). Analyss of deep drawng of sheet metal usng the marform process. he Internatonal Journal of Advanced Manufacturng echnology, 59(5), Reddy, R. V., Reddy, D.. J., & Reddy, D. G. (2012). Effect of varous parameters on the wrnklng n deep drawng cylndrcal cups. Internatonal Journal of Engneerng rends and echnology, 3(1), Reddy, R. V., Reddy,. A., & Reddy, G. C. M. (2012). Optmzaton of blank holder force to control wrnklng and fracture of cylndrcal cups n deep drawng. Internatonal Journal of Engneerng rends and echnology, 3(5), Sen, N., & Kurgan, N. (2016). Improvng deep drawablty of HC300LA sheet metal by warm formng. Internatonal Journal of Advanced Manufacturng echnology, 82(5), Sngh, C. P., & Agnhotr, G. (2015). Study of deep drawng process parameters: a revew. Internatonal Journal of Scentfc and Research Publcatons, 5(2), Vosnakos, G. C., & Gannakaks,. (2013). A knowledge-based manufacturng advsor for press worked sheet metal parts. Journal of Intellgent Manufacturng, 24(6), Wang, J., Goel, A., & Yang, F. (2009). Blank optmzaton for sheet metal formng usng mult-step fnte element smulatons. he Internatonal Journal of Advanced Manufacturng echnology, 40(7), We, D., Cu, Z., & Chen, J. (2008). Optmzaton and tolerance predcton of sheet metal formng process usng response surface model. Computatonal Materals Scence, 42(2), Wf, A., & Mosallam, A. (2007). Some aspects of blank-holder force schemes n deep drawng process. Journal of Achevements n Materals and Manufacturng Engneerng, 24(1), Yang, L., Mor, K., & suj, H. (2008). Deformaton behavors of magnesum alloy AZ31 sheet n cold deep drawng. ransactons of Nonferrous Metals Socety of Chna, 18(1),