土木工程建筑機械外文翻譯外文文獻英文文獻高強度鋼在U彎曲變形中的彎曲性和成型過程

1、Bendability and Forming Behaviour of High Strength Steel in U Bending OperationP. Knewtatip1, N. Prasitkhetkhnn A. Khantachawana1, V. Premanond1, R Hato B. Sresomreonlt N” Koga2king Mongkuls Lhiiversily of Technology Tlionbitri. Hiuiland, Nippon IiisliUrte of JechnolQgy, JapanSummanin this work, the

2、 bend ability and fbnning behaviour of high strength steels m U bending were studied. The sheet materials used in the experiments are (JIS) SAFE 1440 (thickness 2 mm), SPFH590 (thickness 2 imn) and 3PFC78UY (thickness 1.2 mm), binlly, mininiuni bend radius uf each material was invetitigated. N亡xt, t

3、he experim ents to comjfare three different methods of minimizing springback were earned out. The first method is, so called; bottoming that is the redutliun uf sheet thickness at thu bottom of th年 workpiece or at bended pngk by 1(5%. The second one is bottom overbending, i.e., the in ethod to overb

4、end the workpiec亡 at bottom by 6. For this method, the punch having a conGave bottom surface and the bottom pad having corresponded convex upper surface have been used. The lost one 悅 flupge overbending, i c. the method to overbend lhe flange of workpiece by 6a. This can be don亡 by using the punch h

5、aving side relief angle (taper punch). The punches and dies edge radii are 5 mm. The clearance between punch and die tire determined to be (he same material thickness. Two kinds of fiheet layoutt； were experiinenteil i.e.r the sheets were placed in order that their rolhng directions were (1 parallel

6、 and (2) perpyidiculcir to the bend Jine. Ihe results revealed thill the spnngtmck angle increased with the strength of sheet material!. The bottom and flang亡 overhending methods are more effective to reduce springbsck than bottoming method. In addition, for bottoming luethod, the force required was

7、 about 8 limCJi higher than cunvcntioniil bending forct.L IntroductionNowadays, hih strength steel sheets have been widely used in aulumobi industry in order lo reduce weight of the vehicles which is strongly related to dieir Luel consumption rate 14. How aver, tt is generally known tliat tile stren

8、gth of the sheets, which is lelatively higher than that of the cctB entiotial carbon steel sheets. Leads to tlieir low fbmiability and high spiingback of ttie defbmied parts. Many works proposed to reduce springback of the high strength steel. For examples, Mori 2 propcsml to cunlrcl the springbuck

9、of the V bunded part by utilizing CNC servo press to reduce the sheet diickness at bend angle. Next. Yamano 3 has been studied to rexluce side wall curl of the cl raw- bcndixl L-shapc pnrt by using so cnllcd ovcirun inducing-punch. Yoshida J4J studied a crash forming method to rcdiicu springback of

10、the pari made of high strength steel sheet. Yanaaimolo 巧6 sliowcd that sprinsback-fiee forming of high strength steel sheets could be achieved by fcmiing the sheet at elasted teniperature in tlie range of warm working temperature (higher than 750 K but considetably lower than hot working temperature

11、), lilt methods to leduce spiitLgback used in tlie pievious work*i Arc mostly basted on bottoming and overbending principles. In thifi work, the cxpcriincnts to compare the results of this dJTcrent Tnulliuds of minimizing springback were carried out in order to vcrifjr their effectiveness in elimina

12、lion the springbuck of high strength steel sheet. Those methods are bottom)flange overbunding and bottom ovcibcndinj respectively. In atklidon the bendability which is represented by minimum bend radius was also invesboated lor the shes( having Qie strertgdi ranged from 440 to 780 NfPa,2* Expciimenh

13、*l setup und MctliitdologjThree kinds of sheet niatcriahf ; iitf/pii-/)：f Hij，WjWpnui蝕窗(q)syt?f?j 塔wpgq/； /octotjituoj 何ypaiq yv uoijcSnop jc sStejusoij :血 qitSumis qisuai 叩仃:sin Quails 卩赳人:曹人陽 StB691So06AOHiDddS(3iip put? ssiudo.id 申j屮甘ip合內:j iqviqound 燈屮 punoic daiAV O aStn2| 0屮 0SIW3 11!譏 qound o

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18、juoQ |euGieuja)Li| 斗桁 aqx) g。己日JJDIICTP 2008 (The 9th nternabonal Conference on Techno agy of Plasticity(a)(b) Flange overbending(c) Boffotn overbendingF咯 3: Three different methods of elimination springbaek used m the experiments3. Results and discussions3,1+ Benda bi htics (minimum bend radius)The

19、 ratio of bending force required and sheet thickness tor each material are shown in Fig, 4. It is clearly shown that larger forces are required tor the materia having higher strength and for the punch ilaving smaller edge radius. In eases of using the punch with sharp edge (Rp = 0)* the required thr

20、ees are largest which are 1.871.90 times of those when using the punch having RP = 5 mm” The results of mininium beiid radius arc shown in Table 2. The cielortned parts ere ohsened by both Aisuat methtxl and optical microscope. Pour different symbols were used to distinguish lhe quality of parts. Th

21、e dellnilion of each symbol is indiGciled below (lie same Piibk. The saniple pictures, in the cuses()T usiri呂 shaqi-edge punch, corresponded to each symbol arc shown in Tiiblw 3一 As the results；. lt)r all three kinds of sheet materials, bending perpendicular to rolling di recti on is easier than ben

22、ding parallel to rolling direction, as generally known. Benda bi li ties, which arc represented by mintinum bend radius, became worse with increasing of strength oi materials. For SAPH40. the workpieces without tract urc could be obtained although using the puticli with sharp edge (Rp = 0) when bend

23、ing perpendicular to rolling direction. Oil the other hand, SPFH59O could be succcssfiilly bended if the ratio of punch radius and sheet thickness was larger than 0.50. Moreover, the same ratio should be larger than 0.83 in the case oT SPFC7R0Y sheet. These mighl be explained by lhe diiTcrent values

24、 oT the ductility of the sheet materials, lhe minimum bend radius is smaller for the tnaterial having higher ductility (dongalion at brefik as sh(mn in Table I).3.2. Comparison of different methods of spniibstck eliminnti(mThe Ibrce-travel diagrams of ibmiing SAPTT440 workpieces by conventioiwl U be

25、nding, boUoming. lliinge (iverbtnding anil botlom overbt:tiding are shown in 】ig. 5. The maximum Ibrces required lorFig. 4: Farces required for l - bending of each mate rials-UVKeCAM*=?plql 4 中申一72譏rTPK 雷I able 2: Results of minimum bend radiusHuliiio nip punch rC7S0Y1II丄II1II0OAAX0 500o0O0.83oO1.00

26、oo0Q1.67o02.50oo0O47o0丄：Bending perpendicular to rolling direction, | : Bending parallel to railing directionX: Visible fracture along the comer of the workpiece； A: Visible fracture only at the comer of the front and the bick sitlc of the workpiece. : :,raclurti only at the comer of the front ;ind

27、the b;ick side of the workpiece, chwcrvud by the micrnficopc, O No (raclurc foundlable 3: Sample pictures of Lhe deibmietl pails cor re spend e1 to Lhe symbols usetl lo distinguish part quality (R/t - 0)SAPIN40SPFI1590Rmding pSPhrTKOVMaterialsbending the workpieces wene apjyroxtmately 15 kN for a me

28、thods and occmred at about 10 mm of pivwh b aveliins，I lowcvei； in bottoming operation, tlie bottom irig force of about 110 kN 陰% recjuired at the end of the stroke in order to reduce the sheet thickness, likes coining operation, by 10心 of the initial Uiivkness. In EKklition, llic forces re(|Uin;d t

29、o ovcrbctu,! the workpkcefi eiI Ihv cikI of the stroke for tlange and bottom oveibending wei首 abowl 2$ nd 15 kN, respwtively, lhe required forces per sheet Lhiickns lor all kinds of sheet makrkds arc sliown in Fig. 6. The rcsull reveals that Uic lorccs required for bottoming and flange overbetidtng

30、ojxsration were about 8 and 2 times larger than those of conventional U ltending? res卩鈕竹匕時. While? the forces required for bottom overbenditig were almost the same 屈 those of conventional U bending. Hit laiger is the force leads to the larger of the press m achine needed. Frotn this vi卍wpcitit, die

31、bottotn ov亡liiendttiin method jirovided the best result amctig the methods iJstxl in this work.The results of springbuck angk of Lhc 卩戲冷 bended perpend ecu I ar and paralJel lo rolling dirtxlion aru Bhown in Fig. 7 and S? re%pectively. As the rsults+ springbok aigle incraAsed with incruising 0f the

32、strength of the materia as generally known. Ry using bottotning method the springback angle decreased ispproKimatelycompared to die con vent ion al U bending operation. Cot 出岡 Henily*in order to eliminate spingback, the sheet diicknes should be reduced by more than 10no, leadirtg to unacccptEihk lli

33、inning in sumt：Tlic upnngbEitk ang was reduced by 75-88% by using bottomoverbending method一 The overlienditig ang3e larger than 6 is necessary to obtain die parts without s卩ringback. Howcver? by using this mclhotL lhe bollom of the dclormcd part was nol compJclcly fhL Its shape became a circular cur

34、ve corresponded to die punch and the pad surface. 3 or flange_5ICTP 2008 (The Sth International Conference on Technology of Plasticity)overbending method, the parts nearly without spruigback were obtain亡日 for SPFC7S0Y；. while die parts with spriiig-go were obtained for the other two materials. Since

35、 in this method, the fixed plate w as used uistead of moving pad in ordr to allow some of die material kfl Linder die pinch surface duiing the beginning of bending. 丁hi2 extia material was pressed at the end of the mm stroke, causing the flange of the parts wrap araund tlie punch. In order to obtain

36、 tJie parts with acciuate sliaie dimension., ttie overbending angle sluould be adjusted to be lower Ilian 6. Filially, bending perpendicular and parallel to rolling direction provided similar results. However the spriiigback Euigles in the cases of bending pai迫I亡1 to rolliiig direction were sliglitl

37、y greater.BottomingFlange overbendingConvejitional U bendingBottom overbending-6 ；124 -19S.2CnnvenUnnal U bentiiiig24.2Boltomin BottomFlanoverbending overbendingF毎.5: Porce-travel diagram for bending SAPH440 sheet： SAPH4J0 SPFH590 SPFC7B0YEig. 6: Comparison of forces required for various bending ope

38、rationsConY?nLion；ilBottoming BottomFhngeU bendingoverbending overbeudiiigFi環(huán) 7: Spring ack angle of the paris bended petpendicular to the rolling directianICTP 2008 (The 9th International Conference on Technology of Plasticity)Convent iotiiil bottoming BottomFkingeU bindingttverttentliiig overbendi

39、ngFig. 8: Springbuck angle qf the parts bended parallel to the rolling direction4. CondusioiisTlie U bending opeiations of three kinds of high strength steel were carried out in ordeip to investigate tlieir bendabilities and fipringback behaviours. From the results, it can be concluded as follows;(a

40、) The minimum bend radius af the maturijl decreased wiih an incrcain of die ma(urial strength.(b) Th forces required in bottoming and flange overbending methods were approximately 8 and 2 timvs higher than those rtquirml in eunvuntiunai l.T bending op Million. While no cstra Ibruc was required ler t

41、he bottom ovt;rbuiling method.(c) For bottoming metho(L the reduction of thickness at 10% is insufficient to eliminate tlie springback of all ty 卩 of the *heet tiiateriak used,(4) Parts obtained from bottom overbending methods liad a curved bottom corresponded to the shape of the punch jnd pud used.

42、 For this mctlioL the overbending iinglc larger tliiin 6Q is required lo eliminate springback(e) The flange ovcrbcnling method provided the parts wilh minimum springback lor SPFC780Y? but gave the parts with spring-go for 占APII440iinl SPFC59O. The overbending angle slightly lower than 6 is riecessar

43、? in order to obtain the parts having accurate shape dimension.Atkn owl ed gem cn tsrhe authors would like to give our attitude to The Moukl and Die Industry DevrelopTtient Pfoject? under eonliollcd by Thai-Gunnany Institute ( Tliuihnl) Ibr supporting tliv research fund.References1 Nki(sumura4 T. an

44、d Kitao4 M.: Introduction of WG Activity in th* Jupnn Shwl Mjctal Forming Research Groii卩，I of the J叩目n Society for Technology7 of Plasticity (in Japanese 2003* Vol. 46 ,534.65-62.2 Mori. K Akib. K. and Abe, Y.: Springbuck Behavior in Bending Ulfra-High-Strength Sheets Using CNC Servo Press, hit. J.

45、 of Machine Took & Manufacture, 2007S Vol.斗7, 321-325.3 YamanOj T. and Iv*aya, ,L: Study of Countcrmuisurc of Sidu Wall Curl Using Ovcrrun-Lnducing Punch. J of lhe Japan Society for Technology ol Plasticity, 2005t Vol 46 No亦34# 630-635.4- Yosliida, Th, Isogai, E- Hasliiiroto, K.? Katayama, T. and Ku

46、i iyama. Y.: Reduction of Sprtnghack lor Hiyji-Slrungth Steel Sheets by Crash Formings J of the Japan Society lor Technology of Plasticity, 2005, Vol. 46 No.5S4. pp. 6560.5| Yanagimoto, T. and Oyamada, K/ Spingback of high-strength steel after hot and warm sheet ibnnin, Annals of die ORP, 2005, 54(1

47、),213-21676 Yanagimoto. J. and Oyainada. K.: Meehan is m of S|jringback-Free Bcnditig of High-Strength Steel Sheets under Waim Forming Conditions. /XiukiJs of the CIRP, 2007, 56 (1). 265 268.7高強度鋼在U彎曲變形中的彎曲性和成型過程P. Kaewtatipl, N. Prasitkhetkha n1, A. Kha ntachawa na1, V.Prema nondl, R.Hatol, B. Sres

48、omreo ngl, N. Koga21、泰國吞武里孟克皇家科技大學 2、日本科技研究所摘要在這項工作中，研究的是高強度鋼在 彎曲變形中的彎曲性和成形過程。實驗過程中所用的鋼材料是 SAPH44C0厚度為2mm和SPFC780Y(厚度為1.2 mm。首先，各材料的最小彎曲半徑都調查過了。其次， 進行實驗比較了三種不同的減少會彈的方法。第一種方法是這樣的：打底工件的底部或彎曲角度減少了 10%第二種方法是過度彎曲底部，這方法過度彎曲底部6。通過這種方法，沖壓就有沖底部凹面和底部墊一樣的凸面就被用到了。最后一個方法是凸緣過度彎曲，就是過度彎曲工件凸緣6。這個可以通過 邊上有圓角的凹模來完成(卷邊凹

49、模)來完成。凹模圓角和凸模圓角半徑為5mm凹模和凸模之間的最小 間隙要和材料的厚度一致。兩種鋼布置的方法都實驗過了，比如，鋼材被放置為使它們的滾動方向平行 和垂直于彎曲線方向。結果表明回彈角度隨著鋼材強度的增加而增加。在減小回彈方面，過度彎曲和翻 遍的方法比壓底的方法更有效。此外，對于壓底方法，在壓力發(fā)面要求高于傳統(tǒng)彎曲力的8倍。1簡介如今，高強度鋼板已經在汽車工業(yè)領域廣泛應用，因為減少車輛重量和降低燃油消耗率密切相關。但是，眾所周知的，高強度鋼板的強度相對普通碳鋼板較高，這是導致其低成型性和高回彈性的因素。許多工 作用來減小高強度鋼的回彈性。例如，Mori提出利用數(shù)控伺服壓力機來減小鋼 V型

50、彎曲時的回彈角度。其 次, Yaman已被研究用以通過名為超限引導沖壓來減低側壁卷曲 U型部分。Yoshda研究了破環(huán)成型法以減 少高強度鋼板部分的回彈。Ya nagimoto表明可以通過在適宜的高溫工作溫度(高于 750K但比熱處理溫度 低很多)范圍內成形鋼板實現(xiàn)沒有回彈的高強度鋼板成形。以前的工作中該用來減少回彈的方法是基于 觸底和過度彎曲的原則。這項工作中，用來比較三種不同的減少回彈的方法都使用了，用以驗證其在消 除高強度鋼板回彈的有效性。這幾個方法分別是：觸底，過度彎曲法蘭和過度彎曲底部。另外，最小彎 曲半徑代表的彎曲性還考察了強度介于 440和 780之間的鋼板。2.實驗裝置與方法表

51、1中所列的三種板材都用在實驗中。鋼板被裁成形狀為120X 50m的長方形。工件已經被圖1(a)中的工具變形為如圖2(b)中所示的U形尺寸。模具如圖2中所示。側間隙用來調整沖床和模具之間的厚度以適合 板材的厚度。通過所有實驗，將間隙定為和板材厚度一樣大小。實驗中的液壓力為1500KN沖壓速度設為50m/s。稱重傳感器和差動變壓器已安裝用于實時監(jiān)測行程圖。測試中沒使用潤滑油。沖頭具有各種圓 角半徑，比如，使用0、1、2和5mr圓角的沖頭來確定每種物料的最小彎曲半徑凸模半徑定位RD。其次，相比于傳統(tǒng)的使用U彎曲工具的情況，三種不同的工具也都有用于測試消除回彈的成效。這些工具在圖 3 中都有列出。分別

52、是沖底、過度彎曲底部和過度彎曲邊緣。在觸底過程中，通過如圖3(a)所示的有圓角的沖頭工件圓角處的厚度可以減少10滋形后的初始值。對于過度彎曲邊緣和底部，沖壓機和沖模準備比 工件在邊緣和底部方面預期形狀過度彎曲 6度，分別如圖3(b)和(c)所示。更進一步，為了材料留在沖模 表面之下，將固定板用于替代移動過度彎曲邊緣的方法。通過這種方法，沖床下多余的材料會導致邊緣 包住凸模。表1機械性能和工件材料的厚度1550 mmYS屈服強度，UTS:拉伸極限強度，IE:伸長斷裂率Shed materials (JIS)Tesriug ditctiou rehfive to rolling dlmtion)T

53、bickufss; t (mtn)YS (MPa)UTS (MHa)%E1(a) 常規(guī)的U形彎曲工具(b)成形件圖1:常規(guī)I形彎曲工具和成形件圖2:U形彎曲模具（a） 觸底(b)過度彎曲凸緣(c)過度彎曲底部3結果與討論彎曲壓力和每種材料的板材厚度的比值如圖4所示。圖中清楚的顯示出高強度材料的鋼板和有較小圓角半徑的凸模要求有更大的壓力。在使用尖銳圓角（半徑=0 ）的凸模案例中，其所需的最大壓力是使用半徑 =5mm圓角半徑的沖模的1.87 - 1.90倍。取最小彎曲半徑的結果如表2中所示。變形的部分通過目測和光學顯微鏡兩種方法一起觀察。四種不同的符號用以區(qū)分不同部位的質量。每個符號的意義如以下同一個表所示。使用無圓角凸緣的的樣例圖片對應著表3中的每個符號。一般人都知道，結果會是，所有三種材料鋼板垂直于軋制方向的彎曲會比平行于軋制方向的彎曲更簡單。隨著材 料強度地增大，最小彎曲半徑所代表的彎曲性能變得更差。對于SHPH440材料，當彎曲方向垂直于軋制方向時，盡管使用的是無圓角沖模（半徑 =0），但工件可以不發(fā)生斷裂。令一方面，如果沖模半徑和板材的厚度比大于0.5，那么可以用SPFH590材料進行彎曲。此外，如果換成SPFC780Y同樣的比例應該大于 0.83。這個可能是板材延展性能不同的原因導致的。延展性能