北京化工大学：《材料导论》课程阅读材料（金属材料）Review_of_warm_forming_of_aluminum agnesium_alloys

PROTEC-12068,No.of Pages 12 ARTICLE IN PRESS JOURNAL OF MATERIALS PROCESSING TECHNOLOGY XXX (2008)XXX-XXX ELSEVIER journal homepage:www.elsevier.com/locate/imatprotec Review Review of warm forming of aluminum-magnesium alloys Serkan Toros,Fahrettin Ozturk',Ilyas Kacar Department of Mechanical Engineering,Nigde University,51245 Nigde,Turkey ARTICLE INFO ABSTRACT ived 31 Octobe r200 ellent high-s ance abilit 112 nrevisedform er,the tor olity and the ality of the final product alloys ar Accepted 31 March 2008 tive body materials recen esults show that the formability of these alloys is increased at temperature range from 20 product has been a f Al-Mg Warm forming 2008 Elsevier B.V.All rights reserved Aluminum-magnesium(Al-Mg) 5XXx series Contents 12 Introduction agnesium sheets S55 The effects of blankholder force and drawbead geometry 33 888 Conclusion cnowl dgements 888 Introduction industry.The advantages of these alloys are lightweight and very good therm roduced and used in many forms such fact tha as casting.sheet plate.bar.rod channels and foreines in some of these alloys can be formed in a soft condition and various areas of industry and especially in the aerospace heat treated to a temper comparable to structural steel make Coe sponding author.Tel:252254. 16/j.jmatprote i68spd,aro,t,Rieowofvam6mingodalminm-nigetmaor1htePoces.Tehpm

Please cite this article in press as: Toros, S., et al., Review of warm forming of aluminum–magnesium alloys, J. Mater. Process. Tech. (2008), doi:10.1016/j.jmatprotec.2008.03.057 PROTEC-12068; No. of Pages 12 ARTICLE IN PRESS journal of materials processing technology xxx (2008) xxx–xxx journal homepage: www.elsevier.com/locate/jmatprotec Review Review of warm forming of aluminum–magnesium alloys Serkan Toros, Fahrettin Ozturk∗, Ilyas Kacar Department of Mechanical Engineering, Nigde University, 51245 Nigde, Turkey article info Article history: Received 31 October 2007 Received in revised form 11 March 2008 Accepted 31 March 2008 Keywords: Warm forming Aluminum–magnesium (Al–Mg) alloys 5XXX series abstract Aluminum–magnesium (Al–Mg) alloys (5000 series) are desirable for the automotive industry due to their excellent high-strength to weight ratio, corrosion resistance, and weldability. However, the formability and the surface quality of the final product of these alloys are not good if processing is performed at room temperature. Numerous studies have been conducted on these alloys to make their use possible as automotive body materials. Recent results show that the formability of these alloys is increased at temperature range from 200 to 300 ◦C and better surface quality of the final product has been achieved. The purpose of this paper is to review and discuss recent developments on warm forming of Al–Mg alloys. © 2008 Elsevier B.V. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 2. Aluminum for passenger vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 3. Formability of aluminum–magnesium sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 3.1. The effects of blankholder force and drawbead geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 3.2. The effects of temperatures and strain rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 3.3. The effects of lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 4. Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00 1. Introduction Aluminum alloys are produced and used in many forms such as casting, sheet, plate, bar, rod, channels and forgings in various areas of industry and especially in the aerospace ∗ Corresponding author. Tel.: +90 388 225 2254. E-mail address: fahrettin@nigde.edu.tr (F. Ozturk). industry. The advantages of these alloys are lightweight, corrosion resistance, and very good thermal and electrical conductivity. The aforementioned factors plus the fact that some of these alloys can be formed in a soft condition and heat treated to a temper comparable to structural steel make 0924-0136/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2008.03.057

PROTEC-12068:No.of Pages 12 ARTICLE IN PRESS JOURNAL OF MATERIALS PROCESSING TECHNOLOGY XXX (2008)XXX-XX) /15073 four digit system.Themajor al USA 2x1 hat c Manganese fo 20253035 uused series for 9XXx are main alloving elements. use ong Fig.1-Av nun application of the aluminum and its alloys this Khare 2000:sch warz et al,2001). use or .For expanding use ofalu u Aluminum alloys are effective materials for the reduction s in many areas of vehicle weight and are expanding their applications.Fig. o overcome.The formability of the aluminum alloys at ratesthe usage of a on to and A emperatures is generally lower than at both cryogenic has recently increased their aluminum alloy usage. xpect that m alloys usage in Japan A alloys especially 5xXX series alloys and is related to the cle production holds steady at around 10 million units.the due o ng.wh at ele ve age around () ing at crvogenic temperatur nging th at high ot forr Ihe dema num a uch as creep mechanisms which m eformation and cavitations at grain boundaries which may nduce premature the by casting such as engines.wheels.exhaust decor how Aluminum for pass nge vehicles ightweight vehicles have become a key targ get for car mar including bumper beams ou and in forgings including suspension parts Fig 2. 5 g the vehicle nerforma the most e comfort and r abil s that minun ty (Cole and S erman, 1995).Aluminum will prob 2kg of stee can lead to a net reduction me ve the ns in the utomotiv industry (Carle ents on co emissions a shown coa emission is uts in arious allo elements n area can also have a big influence on the sustainabilit of a ca ome of the important sign aspects of a ca t and T ates the material has big infl car eight un (300.000km).although i would about 30%mo 0201202020302094·2003 de while incr asing the employment in the short term (Fuhrmann,1979). Miller et al.,2000;Turkish Statistical Institute,2004). s.S.et al..Review of warm forming of aluminum-magnesium alloys.I.Mater.Process.Tech.(2008

Please cite this article in press as: Toros, S., et al., Review of warm forming of aluminum–magnesium alloys, J. Mater. Process. Tech. (2008), doi:10.1016/j.jmatprotec.2008.03.057 PROTEC-12068; No. of Pages 12 ARTICLE IN PRESS 2 journal of materials processing technology xxx (2008) xxx–xxx it very attractive for fabricating various aircraft and missile parts. The present system utilized to identify aluminum alloys is the four digit designation system. The major alloy element for each type is indicated by the first digit, i.e., 1XXX indicates aluminum of 99.00% minimum; 2XXX indicates that copper is the main alloying element. Manganese for 3XXX, silicon for 4XXX, magnesium for 5XXX, magnesium and silicon for 6XXX, zinc for 7XXX, lithium for 8XXX, and unused series for 9XXX are main alloying elements. In industry, low carbon steels have been commonly used for a long time due to their excellent formability at room temperature, strength, good surface finish, and low cost. How￾ever application of the aluminum and its alloys in this field were ranked far behind steels because of cost and formability issues, despite their high-strength-to-weight ratio and excel￾lent corrosion resistance. For expanding use of aluminum alloys or replacing steels in many areas, however, there have been challenging formability problems for aluminum alloys to overcome. The formability of the aluminum alloys at room temperatures is generally lower than at both cryogenic and elevated temperatures. At cryogenic temperatures, the ten￾sile elongation is significantly increased for many aluminum alloys especially 5XXX series alloys and is related to the enhancement of work hardening, while at elevated temper￾atures it is mainly due to the increased strain rate hardening. Forming at cryogenic temperatures is technologically more challenging than at high temperatures. At hot forming tem￾peratures, other issues should also be taken into consideration such as creep mechanisms which may affect the forming deformation and cavitations at grain boundaries which may induce premature failure at low strain rates. 2. Aluminum for passenger vehicles Lightweight vehicles have become a key target for car man￾ufacturers due to increasing concerns about minimizing environmental impact and maximizing fuel economy without sacrificing the vehicle performance, comfort, and marketabil￾ity (Cole and Sherman, 1995). Aluminum will probably play an important role in the future car generations. Its material properties give some advantages and open the way for new applications in the automotive industry (Carle and Blount, 1999). As a result of the developments in the aluminum indus￾try, improving the mechanical properties of the aluminum alloys by adding various alloying elements increased the application area of these alloys in automotive and aerospace industries (Richards, 1900). Design of aluminum structures can also have a big influence on the sustainability of a car. Some of the important design aspects of a car which influence the environment are weight, aerodynamic and roll-resistance. DHV Environment and Transportation Final Report indicates that the material has a big influence on the car weight. (DHV Environment and Transportation Final Report, 2005). Lightweight car consumes less material resources in the long run (300,000 km), although it would cost about 30% more than the conventional car. Therefore, its production would decrease employment in the car industry by about 4% over a decade while increasing the employment in the short term (Fuhrmann, 1979). Fig. 1 – Average use of aluminum (International Aluminum Institute (IAI), 2002; Martchek, 2006; Mildenberger and Khare, 2000; Schwarz et al., 2001). Aluminum alloys are effective materials for the reduction of vehicle weight and are expanding their applications. Fig. 1 illustrates the usage of aluminum for European and Ameri￾can vehicles over years. In addition to USA and Europe, Japan has recently increased their aluminum alloy usage. Analysts expect that the aluminum alloys usage in Japan Automotive Industry will reach 1.5 million tons by 2010. Assuming vehi￾cle production holds steady at around 10 million units, the average yearly growth will be around 2.5% (McCormick, 2002). As shown in Fig. 1, the amount of aluminum used in 1960 is substantially low. The main reasons are forming difficul￾ties of aluminum alloys at that time and the smaller range of alloys available. The demand for aluminum alloys as light weight materials has increased in recent years. Fig. 2 demon￾strates the amount of produced aluminum products in the world. In the past, the main aluminum products were produced by casting such as engines, wheels, exhaust decor; how￾ever nowadays wrought aluminum products are finding more applications in sheets including exterior panels such as hoods and heat insulators, in extrusions including bumper beams, and in forgings including suspension parts Fig. 2. One of the most important benefits of using aluminum alloys in automotive industry is that every kg of aluminum, which replaces 2 kg of steel, can lead to a net reduction of 10 kg of CO2 equivalents over the average lifetime of a vehi￾cle (Ungureanu et al., 2007). In Fig. 3, the effects of the car components on CO2 emissions are shown. CO2 emission is Fig. 2 – Aluminum products for automobile over years (Cole and Sherman, 1995; Inaba et al., 2005; Patterson, 1980; Miller et al., 2000; Turkish Statistical Institute, 2004)

PROTEC-12068 No.of Pages1 ARTICLE IN PRESS JOURNAL OF MATERIALS PROCESSING TECHNOLOGY XXX (2008)XXX-XXX P9tao8Rgent1gegon oengine ico Motorheating Fuel Quality <%1-3 Meogeagnt<%tio Woton te Loses<%10 Fig.3-Effect of technical measures on the CO2 emission(Mordike and Ebert,2001). Table 1-Saving in fuel consumption(Mordike and Ebert,2001) Measure taken Potential saving (%fuel Importance innovative materials Short-medium term Long term 35 10-15 Motor\gear control 5 Resistance to rolling Motor preheating +士士 Equipment critical in terms of environmental pollution.Schwarz et al. alloy 5017.In their study,they focused on changes in the d that the change in the iron content does not lead to a dramatic degen- by using lightweight materials such as aluminum in new eration in the performance of the material. transportation designs.Weight reduction of the car's compo- Aluminum alloy sheets are widely used in the car,ship nents influences fuel consumption considerably.In Table 1 building and aerospace industries as substitutes for steel the effect of weight reduction on fuel savings is s sheets and fiber reinforced plastic(FRP)pa nels,due to their econom ents of aro 16-8%or as exeper gallon can be realized for every1weigh s high- tyCaka et al 2001)T atur of suc on resis we reduction(Mordike and Ebert,2001). the most used aluminum-magnesium alloys in automotive Recyclability of alloys has also become an important issue application were summarized in Table 2.Figs.4 and 5 illus- in view of energy and resource conservation.For example trates aluminum and other materials usages in automotive recycling potential of the aluminum products is much bet and aerospace industry,respectively. ter than the ferrous metals.Martchek (200)and Mildenb of the mo st effective and widely used and Khare (2000)investigated the recycling potential essary energy to reproduce the aluminum products.According in the 5XXX series alloys.These alloys often contain smal to Martchek(2006),increasing the recycled metal usage in the additions of transition elements such as chromium or man- aluminum production consumes less energy and emits less ganese,and less frequently zirconium to control the grain or greenhouse gas to produce the aluminum ingots.Sillekens et subgrain structure and iron and silicon impurities that are al.(1997)investigated the formability of recy cled aluminum usually present in the form of intermetallic particles(ASM Table 2-Comparison of several Al-Mg alloys Strength Formability Resistance to corrosion Weldability Excellen 5454,5652 5454,5652 545e 5083.5456 5154,5254 5005,5050,5083 5005,5050.5083,5254,5652 5154,5254,5557

Please cite this article in press as: Toros, S., et al., Review of warm forming of aluminum–magnesium alloys, J. Mater. Process. Tech. (2008), doi:10.1016/j.jmatprotec.2008.03.057 PROTEC-12068; No. of Pages 12 ARTICLE IN PRESS journal of materials processing technology xxx (2008) xxx–xxx 3 Fig. 3 – Effect of technical measures on the CO2 emission (Mordike and Ebert, 2001). Table 1 – Saving in fuel consumption (Mordike and Ebert, 2001) Measure taken Potential saving (%) fuel Importance innovative materials Short-medium term Long term Light constructions 3–5 10–15 ++ Cw value 2 4–6 + Motor\gear control 5 10 ± Resistance to rolling 1–2 3 + Motor preheating 2 4–6 ± Equipment 2 4 ± critical in terms of environmental pollution. Schwarz et al. (2001) inspected that the relationship between the usage of the aluminum products in new designs and the CO2 emission and emphasized that the CO2 emission ratio could be reduced by using lightweight materials such as aluminum in new transportation designs. Weight reduction of the car’s compo￾nents influences fuel consumption considerably. In Table 1, the effect of weight reduction on fuel savings is seen. Fuel economy improvements of around 6–8% or as much as 2.5 extra miles per gallon can be realized for every 10% in weight reduction (Mordike and Ebert, 2001). Recyclability of alloys has also become an important issue in view of energy and resource conservation. For example, recycling potential of the aluminum products is much bet￾ter than the ferrous metals. Martchek (2006) and Mildenberger and Khare (2000) investigated the recycling potential and nec￾essary energy to reproduce the aluminum products. According to Martchek (2006), increasing the recycled metal usage in the aluminum production consumes less energy and emits less greenhouse gas to produce the aluminum ingots. Sillekens et al. (1997) investigated the formability of recycled aluminum alloy 5017. In their study, they focused on changes in the amounts of alloying elements (particularly iron) to see how they affect the formability of products. It is observed that the change in the iron content does not lead to a dramatic degen￾eration in the performance of the material. Aluminum alloy sheets are widely used in the car, ship￾building and aerospace industries as substitutes for steel sheets and fiber reinforced plastic (FRP) panels, due to their excellent properties such as high-strength, corrosion resis￾tance, and weldability (Naka et al., 2001). The features of the most used aluminum–magnesium alloys in automotive application were summarized in Table 2. Figs. 4 and 5 illus￾trates aluminum and other materials usages in automotive and aerospace industry, respectively. Magnesium is one of the most effective and widely used alloying elements for aluminum, and is the principal element in the 5XXX series alloys. These alloys often contain small additions of transition elements such as chromium or man￾ganese, and less frequently zirconium to control the grain or subgrain structure and iron and silicon impurities that are usually present in the form of intermetallic particles (ASM Table 2 – Comparison of several Al–Mg alloys Strength Formability Resistance to corrosion Weldability Excellent 5454, 5652 – – 5454, 5652 Highest 5052 – – – High 5456 – 5456 5083, 5456 Good 5154, 5254 5005, 5050, 5083 5005, 5050, 5083, 5254, 5652 5154, 5254, 5557

le 3-Prop of Al-Mg alloysi 99:Boyd et materials (IMUA,2006;Wendt and Weis,2004;Beer and Johnston,1992;Talbot and Talbot,1998; p (kg/m o-(Mra E(GPa) G(GPa) CTE (20C) Hardness Appic Prices 009 124 45925.9 25.9 23.8 BS:28 148 5051 72014.9 25.9 23.8 8547 or panels an No.of Pages 12 5182 103773.6 69.6 23.9 8574 s,load floors (sheet 线 tanks 23.8 OF MATERIALS PROCESSING TECHNOLOGY XXX (2008 ARTICLE IN PRESS 340 567 1200 8 AM6OB- WES4-T S:8 ZK60A- 85792.3 1140 6578g.5 28 595

doi: Please cite this article in press as: Toros, S., et al., Review of warm forming of aluminum–magnesium alloys, J. Mater. Process. Tech. (2008), 10.1016/j.jmatprotec.2008.03.057 ARTICLE IN PRESS 4 PROTEC-12068; No. of Pages 12 journal of materials processing technology xxx (2008) xxx–xxx Table 3 – Properties of Al–Mg alloys in automotive structures and other materials (IMUA, 2006; Wendt and Weiß, 2004; Beer and Johnston, 1992; Talbot and Talbot, 1998; Material Property Data, 1996–2007; Shernaz, 1991; Boyd et al., 1995) Material (kg/m3) a (MPa) Strenght/density (Pa/(kgm3)) E (GPa) G (GPa) CTE (20 ◦C) εb Hardness Applications in automotive Prices Aluminium 5005 2700 124 45925, 9 68, 9 25, 9 23, 8 25 BS: 28 Trim, nameplates, appliques´ 1486 5052 2680 193 72014, 9 70, 3 25, 9 23, 8 25 BS: 47 Interior panels and components, truck bumpers and body panels 5182 2650 275 103773, 6 69, 6 26 23, 9 21 BS: 74 Inner body panels, splash guards, heat shields, air cleaner trays and covers, structural and weldable parts, load floors (sheet) 5252 2670 180 67455, 7 69 26 23, 8 23 BS: 46 Trim 5454 2690 248 92193, 3 70, 3 26 23, 6 22 BS: 62 Various components, wheels, engine accessory brackets and mounts, welded structures (i.e. dump bodies, tank trucks, trailer tanks) 5457 2690 131 48698, 9 68, 9 26 23, 8 22 BS: 32 Trim 5657 2690 110 40892, 2 69 26 23, 8 25 BS: 28 Trim 5754 2670 230 86142, 3 68 22.6 HV: 55 Inner body panels, splash guards, heat shields, air cleaner trays and covers, structural and weldable parts, load floors Magnesium AZ80A-F 1800 340 188888, 8 45 17 26 7 BS: 67 Headlight housing, wheels and tires 1200 AZ31B-F 1770 260 146892, 7 45 17 26 15 BS: 49 Seats, passenger restraints instruments and controls, case of seat belt AZ91D-F 1810 230 127071, 8 45 17 26 3 BS: 63 Treadle of Bicycle AM50A-F 1770 228 128813, 5 45 17 26 15 BS: 60 Exhaust decor, exhaust system AM60B-F 1800 241 133888, 9 45 17 26 13 BS: 65 transmission or transaxle, clutch (if manual), drive line (rear-wheel drive) WE54-T6 1850 280 151351, 4 45 17 26 4 BS: 85 Differential, transfer case subframes, engine block ZK60A-F 1830 340 185792, 3 45 17 26 11 BS: 75 Fuel storage system Plastics Nylon 6/6 1140 75 65789, 5 2, 8 – 144 50 BS: 95 320

PROTEC-12068.No.of Pages 12 ARTICLE IN PRESS JOURNAL OF MATERIALS PROCESSING TECHNOLOGY XXX (2008)XXX-X 景属8另88宝8：1 Fig.4-Alalloys and its application for automotive industry (Sherman,2000;White,2006). 0%5-cunetmtealuagesfcBoing7S7AMosconih 的始88始兽片3设8：总8 Metal Handbook.1988).When magnesium is used as the maio ength,no y.Aloy tance even in marine applications.Selection of g所g8 alloys,for several primarily,mechanical properties.Table 3summarizes feature 首程窗 Formability of aluminum-magnesium sheets 8份好份导9景尽员于的员可 The effects of blankholder force and drawbead 8星品品品品品 made from a metal sheet,the deep drawing process or the suitable pre mal to the sheet are us ted.Two important failure modes limit the applicabil of thec p dra wing and s tretching process:necking and to accurately predict the occurrence of wrinkling is critical 8i5pd5,ao,stl,ioawofvamfomingodahmnum-mgneumaoys1ateocsTdhpocgl

Please cite this article in press as: Toros, S., et al., Review of warm forming of aluminum–magnesium alloys, J. Mater. Process. Tech. (2008), doi:10.1016/j.jmatprotec.2008.03.057 PROTEC-12068; No. of Pages 12 ARTICLE IN PRESS journal of materials processing technology xxx (2008) xxx–xxx 5 Polycarbonate 1200 65 54166, 7 2, 4 – 122 110 BS: 115 400 Polyester, PBT 1340 55 41044, 8 2, 4 – 135 150 Shore D:65 380 Polyester elastomer 1200 45 37500, 0 0, 2 – 130 500 Shore D: 30–82 520 Adhesives 1030 55 53398, 1 3, 1 – 125 2 – 250 Rubber, PVC 1440 40 27777, 8 3, 1 – 135 40 Shore D: 74–88 120 Rubber 910 15 16483, 6 0, 5 – 162 600 Shore A: 30–90 130 Ti–6Al–4Vc 4730 900 190274, 8 120 235 9, 5 10 BS: 334 5845 Cu extruted 8910 390 43771, 1 120 44 16.9 4 BS: 90 2323 Epoxy/glass SMC 1600 260 162500, 0 – – 3, 65 – – – H254 polyester laminate 1600 41 25625, 0 – – 0, 29 – Barcol:30 – Thermoset polyester 1820 55 30219, 8 – – 1, 2 – Barcol:32 – Epoxy/glass SMC 1600 260 162500, 0 – – 3, 65 – – – H254 polyester laminate 1600 41 25625, 0 – – 0, 29 – Barcol:30 – a Yield point. b Elongation at break %. c Heat-treatment. Fig. 4 – Al alloys and its application for automotive industry (Sherman, 2000; White, 2006). Fig. 5 – Current material usages for Boing 757 (Moscovitch, 2005). Metal Handbook, 1988). When magnesium is used as the major alloying element or combined with manganese, the result is a moderate to high-strength, non-heat-treatable alloy. Alloys in this series are readily weldable and have excellent resis￾tance to corrosion, even in marine applications. Selection of suitable aluminum alloys, for several applications, requires a basic knowledge of heat treatment, corrosion resistance, and primarily, mechanical properties. Table 3 summarizes features and applications of Al–Mg alloys. Three different material groups, their properties and applications were compared for material selection. 3. Formability of aluminum–magnesium sheets 3.1. The effects of blankholder force and drawbead geometry Typical sheet metal forming processes are bending, deep drawing, and stretching. If a doubly curved product must be made from a metal sheet, the deep drawing process or the stretching process is used. The deep drawing process can reach production cycles of less than 10 s, and is hence a suitable process for mass production. In deep drawing and stretching, the stresses normal to the sheet are usually very small compared to the in-plane stresses and are therefore neglected. Two important failure modes limit the applicabil￾ity of the deep drawing and stretching process: necking and wrinkling. Both are closely related to the material properties. The ability to accurately predict the occurrence of wrinkling is critical in the design of tooling and processing parame￾ters (Xi and Jian, 2000) like sheet thickness, blankholder force