Analysis and Research on Mismatch in Tailored Blank Laser Welding

Transcription

1 Analyss and Research on Msatch n Talored Blank Laser Weldng Lng Xn Shenyang Insttute of Autoaton, Chnese Acadey of Scence Graduate School of the Chnese Acadey of Scences Shenyang, Laonng Provnce, Chna lxn@sacn Zhgang Xu,Mngyang Zhao and Tanxu Zhu Shenyang Insttute of Autoaton, Chnese Acadey of Scence Shenyang, Laonng Provnce, Chna {zgxu&yzhao}@sacn Abstract Msatch s an portant qualty evaluaton standard n Talor Welded Blanks The control of satch, especally for thnner blanks, s a dffcult technque n Talored Blank Laser Weldng process In ths paper, the producton and control of satch s studed based on a Talored Blank Laser Weldng syste The orgns of the satch are obtaned after nubers of experents: the deforaton of the blanks before weldng, the ntensty of the clapng force, the unforty of the clapng force, the deforaton of the clapng bea, the flatness error of the based platfor and the weldng process A atheatcal odel s establshed accordng to the analyss of the orgns producng satch Experental results ndcate that the odel provdes an effectve theory n ncreasng weldng qualty predct satch and last experent s carry out to prove the effcency of the odel II STRUCTURE OF THE SYSTEM Fg 1 shows the vew of the Talored Blank Laser Weldng syste whch s ade up of several unts, ncludng load unt, postonng unt, weldng unt, ejector unt, unload unt and control unt Keywords Msatch, Talored Blank Laser Weldng, Orgns of the satch, Matheatcal odel for satch I INTRODUCTION Laser anufacturng s a odern process technque wth the advantages of deep weld penetraton and nzng heat nputs [1-3] Talored laser weldng technology has becoe an portant anufacturng process for autooble ndustry Talor welded blanks are defned as two or ore sheets of blanks wth sae or dfferent echancal propertes or surface coatngs welded together by laser before stapng [4] Wth the developent of ths technque, the focus attenton has been changed nto solvng the probles of reducng autooble weght, ol consupton and ar polluton fro the ntal applcaton of wde blanks wth equal thckness by laser weldng Talor welded blanks has becoe a hot ssue n the autooble ndustry and steel ndustry for ts hgh qualty, hgh proft and low cost of producton[5], [6] Laser weldng s superor to general weld ethod, but t s very strct wth the weldng qualty especally satch Msatch requreents are drven by product requreents as well as process requreents, such as de settngs and weld strength requreents n stapng operatons In order to obtan qualty staped panels, talor welded blanks should be suffcently algned so that no pont along the weld sea s offset by greater than 15 percent below flush or percent above flush of thckness of the thnner eber Msatch wll be studed n detal n ths paper Frst, orgns of satch are analyzed based on several theoretcal analyses and easureents, then Matheatc odel s bult to 1 Load unt Weldng unt 3 Postonng unt 4 Ejector unt 5 Unload unt Fg1 Talored Blank Laser Weldng syste III ORIGINS OF MISMATCH A Defntons Msatch s defned as when two or ore sheets of blanks wth sae or dfferent thckness welded together, the two blanks should be suffcently algned so that no pont along the weld sea s offset by greater than 15 percent below flush or percent above flush of thckness of the thnner eber (Fg) [7] Fg Defne of satch B Analyss of the Orgns Producng Msatch The structure of the clapng set and the deforaton of the blanks are the an reasons for satch There are sx factors affectng the producton of satch: the deforaton of the blanks before weldng, the ntensty of the clapng force, the unforty of the clapng force, the deforaton of /8 /$5 8 IEEE RAM 8

2 the clapng bea, the flatness error of the based platfor and the weldng process Fg 3 s the clapng set of the Talored Blank Laser Weldng achne It has two functons: guaranteeng the poston precson of the blanks and controllng the deforaton of the blanks Fg 3 Clapng set 1) Deforaton of the Blanks The deforaton of the blanks s the drect factor for satch The blanks to be welded ay be defored partally durng feed preparaton, storage and transportaton The deforaton of the thn blank sheet has the characterstcs of coplexty and plurals There are two typcal basc deforatons shown n Fg 4 after nvestgaton: defored around X and Y axs respectvely All the deforatons of the blank sheets can be coposed of two basc deforatons The deforaton of the weldng edge wll not dsappear, because there s about 1 projectng edge of the blank sheet when claped, the deforaton of the weldng edge wll produce satch We can use atheatcal ethod to obtan the deforaton around X axs, and fnte eleent analyss ethod to fnd the deforaton around Y axs Fg 5a shows the deforaton around X axs before claped Fro Fg 5b we can see that the deforaton n claped area dsappears, but the deforaton of the projectng edge of the blank sheet stll exsts The deforaton can be descrbed as: h = R R l (1) where h s the deforaton of the blanks around X axs, R s the radus of the deforaton, and l s the length of the projectng edge Msatch produced by deforaton of the blanks can be descrbed as: bd bdx bdy x x M = M = R R l weldng edge Y X Fg 4 Two typcal basc deforatons bdy () a Before claped b After claped Fg 5 Deforaton around X axs before and after claped ) Intensty of the Clapng Force The ntensty of the clapng force s an portant factor n controllng satch Sall clapng force can not ake the deforaton of the blank under requreent The rgdty of the clapng set should be hgher If the clapng force s too bg, t wll ake the work uch ore dffcult and other unknown probles ay coe up Sutable ntensty of the clapng force s very portant n controllng the satch Fg 6 shows the satch of the two blanks wth the thckness of 7 and 16 Fro the nspected results obtaned by Servo-Robot, we can see that the satch turns saller when the clapng force becoes bgger, but when the force s too bg the satch turns bad Too uch clapng force leads to the deforaton of the clapng bea whch can affect the unforty of the clapng force The deforatons wth clapng force can be obtaned usng the ethod whch s presented n [8] The clapng forces are to counteract the deforatons of the blanks and these deforatons can be assued to result fro the condton that the blanks wth dfferent edges fxed receve deforatons under the unfor load q Here the analyss wll be taken based on the deforaton around Y axs We can get the deforaton of an arbtrary pont on the blanks accordng to the flexng dfferental equaton of thn plate [9-11]: 3 Eδ 4 w = q (3) 1(1 ν ) The sybols shown n the equaton are: w : The deforaton of an arbtrary pont on the blanks q : The unfor load E : Young s odulus of the blanks δ : Thckness of the blanks ν : Posson s rato, here ν = 3 The deforatons can be abstract as the blanks wth two opposte edges fxed whose length are b defor under the unfor load q Based on the edge condtons, the flexvty f s: f = [ Ach + B sh + C sh = 1 a a a a + D ch + f ( y)]sn (4) a a a The coeffcent of A, B, C and D can be obtaned fro the edge condtons, and f (y) s the partcular soluton Fro the actual deforatons of the blanks, q can be obtaned h R

3 Then the deforatons wth the clapng force can be gven usng CATIA Then, satch produced wth dfferent clapng forces can be descrbed as: M F = M (F) (5) MPa 3MPa 55MPa 4MPa Fg 6 Msatch wth dfferent clapng forces 3) Unforty of the Clapng Force The unforty of the clapng force whch contans the unforty between clapng plates and each plate s another portant factor for satch Fg 7a shows the structure of the clapng set whch claps by sprngs The dfferent decreents of the sprngs lead to the non-unfor clapng forces whch ean clapng plate wth sall decreent doesn t have a good effect on controllng satch One clapng plate whch contans two sprngs wll lean f the two sprngs have dfferent forces whch ay ake satch (Fg 7b) l 1 = l = l (=1, n) (6) when claped, the botto of the plates on the sae level: l1 f1 = l f = l f = h (=1, n) (7) the decreent of the sprng s x = l l (=1, n) (8) Where l = h + f (=1, n) (9) f s the deforaton of the pont whch can be obtaned fro (1) EIf = [ M ( x) dx] dx + Cx + D (1) here, E s Young s odulus, I s nerta, M s the oent at pont, C and D are ntegral constant there s also: F = k x (11) Fro (5)-(11), we can get the expresson of F There are two ways to nze the non-unforty produced by the deforaton of the clapng bea One s to ncrease the stffness of the bea whch s an arduous task; another s to adjust the ntal length of the sprng to ake the forces unfor (Fg 9b) Next, the second ethod s descrbed n detal Frst, calculate f accordng to (1) wth the assupton that the clapng forces are unfor When claped, the bottos of the plates are on the sae level: l1 f1 = l f = l f = h (=1, n) (1) Because each clapng force s the sae, the decreent of the sprng s also equal: x1 = x = x (=1, n) (13) The ntal length of each sprng can be descrbed as (14) accordng to (1), (1) and (13) l = l + x = f + h + x (14) The unforty of the forces can be guaranteed by adjustng the ntal length of the sprng accordng to the result obtaned above Fg 8 Deforaton when clapng a Clapng set b Clapng plate Fg 7 Msatch produced by non-unfor clapng forces 4) Deforaton of the Clapng Bea The clapng bea wll defor durng clapng (Fg 8) The axu of the deforaton whch wll ake the clapng force dfferent s about n the center of the bea The non-unfor forces produced by the deforaton of the bea wll be coputed Fg 9a s the scheatc dagra of the clapng bea Each clapng plate contrbutes F Before clapng, each sprng has the sae length: 1 3 n 1 3 n a Before adjust b After adjust Fg 9 Scheatc dagra of the clapng process 5) Flatness Error of the Based Platfor

4 Based platfor for both thn blank sheet (front based platfor) and thck blank sheet (rear based platfor) akes up the whole based platfor The satch of the two platfors caused by flatness error can also contrbute to the satch Measureents and experents are taken to fnd how the flatness of the based platfor affects the satch Mcroeter gauge s used to easure the satch of the two based platfor The easurng prncple s to easure the relatve postons between the platfor and the standard ruler, then deduce the satch of the two platfors (Fg 1) The precson of the ruler s under 1 The ruler oves fro poston 1 to n wth the spacng of 5, and the croeter oves on the ruler and easures sx ponts each poston The sx ponts wth the spacng can generate two lnes whch have two crossng ponts wth the central lne The dstance between the crossng ponts s the satch of each poston The easurng results are shown n Table I Fg 11 shows the satch curve An experent s taken to fnd how uch the satch of the platfor affects the satch of the blank The experent s conducted on a selected secton of the based platfor fro to 6 The szes of the blanks tested are and , and the weldng edge s 4 n length The satch s detected usng Servo Robot (Fg 1) Fro Fg 11 and Fg 1, we can fnd that the trend of the platfor satch deterne the trend of the blank to a certan extent Then, satch produced by the Flatness error of the based platfor can be descrbed as: M p = p(x) (15) where p(x) s the satch of the based platfor TABLE I MEASURING RESULTS OF THE MISMATCH OF THE BASED PLATFORM NO Poston () Msatch (1) NO Poston () Msatch (1) Mcroeter gauge 1 n a1 a b1 b Front based c1 c platfor Standard ruler d1 d e1 Rear based e platfor Msatch of the platfpr() f1 f Fg 1 Scheatc dagra of the easurng prncple Msatch of the the based platfor an bn cn dn en fn Center lne Standard ruler a1 b1 c1 d1 e1 f1 Front based Rear based platfor platfor Msatch of the platfor Based platfor() Fg 11 Msatch curve of the based platfor Fg 1 Msatch detected usng Servo Robot 6) The Weldng Process Analyss of the satch curves before and after weldng (Fg 13) ndcates that weldng process also contrbutes to the satch Durng weldng process, the teperature dstrbutons of the blanks are unbalanced; the aterals near weld zone experence dfferent rate of expansblty and shrnkage whch akes the aterals n coplex 3D resdual stress status and produce teporary or peranent deforaton However, lttle knowledge of the weldng deforaton has been obtaned [1] Although, nueral odellng ethod for weldng deforaton have been provded wth the developent of coputer technque, there are stll several dffcultes n the odellng precson for lttle knowledge of the aterals n hgh teperature and coplex coputaton Ths paper ntroduces an eprcal agnfcaton functon to descrbe the satch produced by weldng process M after = k( h1, h ) M before (16) where M after s the satch after weldng, M before s the satch before weldng and k(h 1,h ) s the eprcal agnfcaton functon Fg 13 Msatch before and after weldng

5 IV MATHEMATICAL MODEL OF THE MISMATCH Matheatcal odel of the satch can be gven as (17) accordng to the analyss n part III M = M bd F equ cbd p (17) w where M s the total satch, M bd the satch produced by deforaton of the blanks, M F the satch produced by the clapng force, M equ the satch produced by the unforty of the clapng force, M cbd the satch produced by the deforaton of the clapng bea, M p the satch produced by flatness of the based platfor, M w the satch produced durng weldng process M equ can erge nto M F, then (17) can be splfed as the followng: M = M (18) bd F cbd V EXPERIMENT AND SIMULATION Experent s done on the Autoatc Talored Blank Laser Weldng achne n dsplaced n part II The blanks to be test are and , and the weldng edge s 4 n length The easurng equpent s Servo Robot A Deforaton of Blanks The deforaton curvatures of the 7 blank round X and Y axs s and And the deforaton curvatures of the 16 blank round X and Y axs s and 1 4 B Clapng Force The clapng force s 1N/, and t s 1 dstance fro the weldng edge C Msatch of the Based Platfor The experent s conducted on a selected secton of the based platfor fro to 6 Table I gves the nuercal value of the satch of the based platfor D Weldng Process The weldng paraeters are as follows: laser power: 4kw, weldng speed: 68/s, defocus: 6, offset: 8 E Sulaton and Analyss The satch of the blanks can be obtaned accordng to (18) Frst, the deforatons of the blanks around X axs after claped are as followngs accordng to (1) f f bd1 fbdx 1 = Rx 1 Rx 1 l =, bd = fbdx = Rx Rx l The deforaton curve s shown n Fg 14 The clapng forces are consdered to be unfor after the ntal lengths of the sprngs adjusted Fg 15 gves the deforaton of the blanks around Y axs after claped based on the fnte eleent analyss Fg 16 shows the satch of the selected secton of the based platfor fro to 6 Then, the specfc expresson of the eprcal agnfcaton functon s descrbed as (19) under the weldng paraeters entoned above k h, h ) 4/3 (19) ( 1 = p w Fnally, the total satch whch s shown n Fg 17 s the su of the satch obtaned above Fg 18 s the satch detected by Servo Robot whch s a laser vson syste for weld nspecton The coparson between Fg 17 and Fg 18 ndcates that the satch gotten by the atheatcal odel has a good agreeent wth the result detected by Servo Robot Msatch of the platfpr() Msatch() Deforaton() Deforaton() Deforaton of the 7 blank Weldng edge() Deforaton of the 16 blank Weldng edge() Fg 14 Deforatons of the blanks around X axs after claped Fg 15 Fnte eleent analyss result Msatch of the the selected secton of the based platfor Based platfor() Fg 16 Msatch of the selected secton of the based platfor Msatch Sea length() Fg 17 Msatch Obtaned by sulaton

6 Fg 18 Msatch detected by Servo Robot VI CONCLUSION The research on satch of Talored Blank Laser Weldng syste s conducted n ths paper Analyss and atheatcal odelng ethod for the satch are brefly descrbed Experent s carred out to exane the precson of the odel Based on the analyses and experents present n ths paper, the followng conclusons ay be ade: 1) Analyses and experents suggest that there are nuerous orgnals affect satch n Talored Blank Laser Weldng ) The specfc expresson of eprcal agnfcaton functon s obtaned based on a large nuber of experents 3) The coparsons between experent and sulaton results ndcate that atheatcal odel for satch has a good effect n predctng satch REFERENCES [1] L Xn, et al, Analyss and Desgn of a Novel Four-axs Plane Laser Weldng Syste IEEE Internatonal Conference on Mechatroncs and Autoaton Harbn, Chna, pp-5, 7 [] X Lang, YZ Zhang, Applcaton of Laser Technology to Autooble Industry, Mechancal Engneer, no6, pp -3, June 6 [3] ZG Peng, The status quo and developent trends of the weldng technology n autootve anufacturng, Modern Weldng Technology, vol 44, no8, pp 5-9, August 6 [4] Ghoo B Y,Keu Y T and K Y S Evaluaton of the Mechancal Propertes of Welded MetaI n Talored Steel Sheet Welded by CO Laser Journal of Materals Processng Technology, pp , 1 [5] Q Yan, The Applcaton of Talor Welded Blanks n the Autooble Industry, Appled Laser, vol 4, no 6, pp , Deceber 4 [6] Knsey B,Lu Zhhong and Cao J A novel forng technology for Talor-welded Blanks Journal of Materals Processng Technology, vol 99, no 1, pp , [7] ISO , Weldng electrons and laser bea welded jonts gudance on qualty levels for perfectons [8] L Xn, et al, Analyss and Desgn of a Novel Four-axs Plane Laser Weldng Syste IEEE Internatonal Conference on Mechatroncs and Autoaton Harbn, Chna, pp-5, 7 [9] Z Wang, Clapng fxture n weldng and shft achne, Bejng: Chna achne Press, 1 [1]Z Xa, L, Jang and S Tang, Elastc Mechancs and Nuercal Method, Shangha: Tongj Unversty Press, 1997, pp [11]L Yang, Elastc Mechancs and Fnte-eleent Method, Hangzhou: Zhejang Unversty Press,, pp [1]H Chen, et al, The present stuaton of nuercal sulaton for deforaton of the thn weldent, Weldng Technology, vol 35, no 3, pp 4-7, 6