鋼材種類(lèi)和變形的基礎(chǔ)知識(shí)

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1、Basic Knowledge of Steel and Plastic Mechanics基礎(chǔ)鋼和塑性變形知識(shí)2Contents1. Steel Mechanical properties Worldwide steel grades Advanced high strength steel (AHSS)2. Plastic mechanics Sheet deformation modes Forming limits Yield criteria3Introduction to elasticity and plasticity1.固體材料受外力作用產(chǎn)生變形，從變形開(kāi)始到破壞一般要經(jīng)歷兩

2、個(gè)階段：彈性變形(elastic deformation)和塑性變形(plastic deformation)。2.外力卸載后，彈性變形能夠完全消失，而塑性變形不能消失。3.彈性變形和塑性變形的機(jī)理：材料原子之間的作用力平衡。4.位錯(cuò)(dislocation)理論。5.強(qiáng)化機(jī)制(work hardening mechanism)。Dislocation movement4Uniaxial tensile testGB/T228 金屬材料室溫拉伸試驗(yàn)方法EN10002-1 Metallic materials - Tensile test - Part 1 : test method (in a

3、mbient temperature)Typical tensile test piece5Engineering stress-strain curve6Engineering stress-strain curve7Strength and DuctilityStrength parametersEngineering stressEngineering strainElongationReduction of areaDuctility8True stress-strain curveTrue stress True strain9Working hardening (strain ha

4、rdening)Strain hardening exponent (n-value)10Influence of strain-hardening exponent n3 n2 n111Anisotropy (R-value) Width strain: w=ln(w/w0)Thickness strain: t=ln(t/t0)R= w/tPlanar anisotropy ratioNormal plastic anisotropy ratio12Strain rate sensitivity Strain rateStrain rate sensitivity exponentStra

5、in rate sensitivity has a crucial influence on the research of crash resistance and high-speed stamping formability.13Worldwide steel grades14Worldwide steel grades15Common steel types and evolving AHSS types Interstitial free (IF) steels Mild steels Bake hardenable (BH) steels Isotropic (IS) steels

6、 Carbon-manganese (CM) steels High-strength low-alloy (HSLA) steels Dual phase (DP) steels Transformation induced plasticity (TRIP) steels Complex phase (CP) steels Martensitic (Mart) steels16Strengthening mechanism17HSLA steel18Grades of HSLA steel in EU19Application of HSLA steel20Dual phase (DP)

7、steel21EU steel gradesComparison European steel grades (Mild steel, HSLA, Dual-Phase)01002003004005006007008009001000Tensile strength; Yield strength MPaRm max 350 400 410 440 450 480 510 530 550 600 620 620 650 700 760 700 900Rm min. 270 270 270 270 340 370 390 400 430 430 460 480 510 550 600 600 7

8、80Re min. 140 140 140 170 240 280 315 320 355 360 400 420 460 500 550 320 450Re max. 210 330 280 360 310 360 410 460 500 400 550DC04 DD14 DC01 DD11 H240 LA H280 LA S315 MC H320 LA S355 MC H360 LA H400 LA S420 MC S460 MC S500 MC S550 MC DP590/ DP60 DP780/ DP80Legend:Cold RolledHot RolledDual Phase co

9、ld rolled(values from ARCELOR)Not for new productsFrom Claus Unruh22Dimension availabilityAvailability check materials Europe versus US update Nov 2006(only acc. my information; must be checked and confirmed by Purchasing department) Material availibility of standard materials is given.Material avai

10、libility of S460 MC is decreasing even in Europe.Material availibility of Dual Phase and other special grades must checked for each dimensions MILD STEEL 01 MILD STEEL 04Europe DC01 DC04 H280 LA H320 LA S315 MC H360 LA S355 MC H400 LA S420 MC S460 MC S500 MC S550 MC0.60.70.81.01.21.51.82.02.53.03.54

11、.04.55.0 HSLA 460HSLA 340 HSLA 380HSLA 300 HSLA 420 HSLA 500 HSLA 550HR CRLegend: Available in the market Available in the marketAvailable from individual steel producer Available from individual steel producerAvaibility not clear Avaibility not clearMILD STEEL 01 MILD STEEL 04US ASTM 1008 CS ASTM 1

12、008 DDS SAE J2340 CR 300 X SAE J2340 HR 300 X SAE J2340 CR 340 X SAE J2340 HR 340 X SAE J2340 CR 380 X SAE J2340 HR 380 X SAE J2340 CR 420 X SAE J2340 HR 420 X SAE J2340 CR 490 X SAE J2340 HR 490 X SAE J2340 CR 550 X SAE J2340 HR 550 X0.60.70.81.01.21.51.82.02.53.03.54.04.55.0 HSLA 380 HSLA 420 HSLA

13、 500 HSLA 550HSLA 460HSLA 340HSLA 300 From Claus Unruh23Dimension availabilityAvailability check materials Europe versus China update Nov 2006(only acc. my information; must be checked and confirmed by Purchasing department) MILD STEEL 01 MILD STEEL 04EuropeDC01 DC04 H280 LA H320 LA S315 MC H360 LA

14、S355 MC H400 LA S420 MC S460 MC S500 MC S550 MC0.60.70.81.01.21.51.82.02.53.03.54.04.55.0HSLA 460HSLA 340 HSLA 380HSLA 300 HSLA 420 HSLA 500 HSLA 550HR CRLegend: Available in the market Available in the marketAvailable from individual steel producer Available from individual steel producerAvaibility

15、 not clear Avaibility not clearMILD STEEL 01 MILD STEEL 04China DC01 DC04 H280 LA H320 LA S315 MC H360 LA S355 MC H400 LA S420 MC S460 MC S500 MC S550 MC0.60.70.81.01.21.51.82.02.53.03.54.04.55.0 HSLA 380 HSLA 420 HSLA 500 HSLA 550HSLA 460HSLA 300 HSLA 340Material availibility of standard materials

16、is given.Material availibility of S460 MC is decreasing even Europe.Material availibility of Dual Phase and other special grades must checked for each dimensions From Claus Unruh24Standard thickness China vs. JapanNot available for the materials whose Re=400MPaNot frequently used in ChinaNOTEFor the

17、 materials with non-standard thickness, Chinese steel companies can produce them according to the customers requirement if the volume is not less than 20 tons per batch. If the volume is less than 20 tons per batch, the steel companies will probably not produce them. 0,5 0,6 0,8 1,0 1,2 1,5 1,6 1,82

18、,0 2,2 2,5 3,0 3,2 3,5 4,0Standard thickness of steel sheets & strips for automobile structures 1,6 1,8 2,0 2,3 2,5 2,6 2,8 2,93,2 3,6 4,0 4,5 5,0 5,6 6,00,6 0,7 0,8 0,9 1,0 1,2 1,4 1,61,8 2,0 2,3Standard thickness of hot rolled high strength steel sheets for automobile structures Standard thickness

19、 of cold rolled high strength steel sheets for automobile structures ChinaJapan25HSLA steel grades overviewOverview steel grades: HSLA (high strength low alloyed) Steel familycold rolledhot rolledLegend:Existing grades after standardisation Use only standard HSLA steel (worldwide available)H240 LA a

20、nd S460 MC was cancelled caused by sourcing problems worldwide !EN 10268EN 10149-2SAE J2340SAE J2340 420 X 490 X 550 X300 X 340 X 380 X 420 X 490 X 550 X300 X 340 X 380 X S420 MC S500 MC S550 MCS315 MC S355 MC H400 LAH280 LA H320 LA H360 LAValid national and international standardsHSLA 420 HSLA 500

21、HSLA 550HSLA 300 HSLA 340 HSLA 380From Claus Unruh26Mild steel grades overviewOverview steel grades: Mild steelSteel family cold rolled hot rolledLegend:EN 10130EN 10111ASTM 1008ASTM 1011SAE J2340SAE J2340JIS G3135JIS G3134Q/BQB 419(Bao-steel)Q/BQB 310(Bao-steel)NF A 36-410NF A 36-401NF A 36-301DIN

22、1623DIN 1614-2 280 A 250 A 210 A 180 ACS DSMS01 MS03DSDC01 DC03DD11 DD13 MS04 MS05St 14DD14STW 22 STW 24C E ESSt 12 RRSt 13SPCCbrand name:St 12 brand name:St 14SPCEN1C 3C 3CTCS DC05DC04invalid former national standardsValid international and national standardsDDS EDDSExisting grades before standardi

23、sation Existing grades after standardisation Only 2 grades are allowed:DC01/ CS: soft steel for simple low strength press parts DC04/ DDS: soft steel with good deep drawing properties; for complex low strength press parts Brand names and other material designations will not be accepted.EN 10130ASTM

24、1008Valid international and national standardsMS01 MS04CS DDSDC01 DC04From Claus Unruh27DP steel grades overviewOverview steel grades: Dual-Phase steel Steel familycold rolledhot rolledLegend: (*) Japanese grades not exactly comparableDP400 and DP 500 are not relevant for seat structures. DP1400 in

25、development.Standardisation of Dual Phase grades is difficult, caused by missing European standard.Availability has to be clarified for each grade and dimension.Purchasing department must support the process.From Claus Unruh28Products from Bao Steel for automobile structuresMild steels29Products fro

26、m Bao Steel for automobile structuresDP steels Hot rolled mild & HSLA steels30Products from Bao Steel for automobile structuresCold rolled HSLA steels Hot rolled HSLA steels31VHSS category at Arcelor32Metallurgy of VHSS at Arcelor33Application of VHSS34Application of VHSS35Engineering stress-strain

27、curve of DP steel Higher tensile strength of DP steel (larger n-value) Better stamping formability and crash resistance performance of DP steel36n-value of DP steel37Application of DP steel38FEA results of DP steel39FEA results of DP steel40Sheet metal forming processesblanking & piercingbending(a)

28、Bending in a folding machine(b) Bending in a vee-die(c) Section of a set of rolls in a roll former(d) Wiping down a flange41Sheet metal forming processesflanging stretching(a) A shrink flange with buckling(b) A stretch flange with cracking(c) Flanging a curved sheet Section bending(a) Stretching a d

29、ome in a sheet(b) A domed punch and die set for stretching a sheet42Sheet metal forming processeshole-extrusionstamping (drawing)(a) Typical part formed in a stamping or draw die showing the die ring, but not the punch or blankholder(b) Section of tooling in a draw die showing the punch and blankhol

30、der43Sheet metal forming processesTooling for deep drawing a cylindrical cup Tooling for forward redrawing a cylindrical cupTube forming(a) Expanding the end of a tube with a flaring tool(b) Reducing the diameter of a tube by pressing it through a sinking die44Sheet metal forming processesHydroformi

31、ng a shallow part Expanding a round tube to a square section by hydroformingUsing combined axial force and fluid pressure to form a T-joint Thinning a sheet locally using a coining tool45Sheet metal deformation modes - stretchingstretching塑性變形局限在某一固定區(qū)域內(nèi)。成形依靠材料表面積增大實(shí)現(xiàn)，因此變形區(qū)域材料厚度變薄。變形區(qū)域的應(yīng)力狀態(tài)是雙向拉伸。材料不起

32、皺，變形區(qū)域表面質(zhì)量好。Strain status: biaxial tension試驗(yàn)方法：杯突評(píng)估指標(biāo)：IE試驗(yàn)方法：極限拱頂高評(píng)估指標(biāo)：LDH046Sheet metal deformation modes - drawingdrawing (cup drawing)坯料外部環(huán)形區(qū)域是變形區(qū)，坯料內(nèi)部圓形區(qū)域不變形。在徑向的應(yīng)力是拉應(yīng)力，在切向的應(yīng)力是壓應(yīng)力。因此，坯料在徑向可能出現(xiàn)破裂（拉裂），在切向可能出現(xiàn)起皺（壓縮）。Strain statusRadial: tensionTangential: compression試驗(yàn)方法：圓筒拉深評(píng)估指標(biāo)：LDR47Sheet metal d

33、eformation modes - bendingbending曲率發(fā)生變化的區(qū)域是變形區(qū)。坯料圓角和直邊部分參與變形，變形過(guò)程和卸載過(guò)程很復(fù)雜。卸載后零件容易發(fā)生回彈，導(dǎo)致達(dá)不到尺寸精度。試驗(yàn)方法：V形彎曲評(píng)估指標(biāo)：Rmin/t48Sheet metal deformation modes - flanging(a) Shrink flanging(b) Stretch flanging試驗(yàn)方法：擴(kuò)孔評(píng)估指標(biāo)：(a)圓錐沖頭(b)平底沖頭49Principal strain status during deformationdrawing plane strain stretching50

34、Forming limitsTest procedure of material forming limits (forming limit curve, FLC) Forming limit diagram (FLD)51Application of FLDAnalysis of sheet metal forming process based on FLD52Yielding in plane stressPlane stress 1, 20, 3=0Maximum shear stress and maximum shear stress planesThere are on shea

35、r stresses on the faces of the principal element. On a face inclined at any other angle, both normal and shear stresses will act. On faces of different orientation it is found that the shear stresses will locally reach a maximum for three particular directions. They are inclined at 45 to the princip

36、al directions.53Yielding in plane stressYielding condition can be expressed asMohr circle of stress54Tresca yield criterion The Tresca yield criterion in plane stressHypothesis: yielding would occur when the greatest maximum shear stress reaches a critical value.1=2, 1=3, 3=0max=1If 20, min= 3=0If 2

37、0, min= 2In plane stress Note:1. Application only to isotropic materials.2. Not considering material work hardening.55Von Mises yield criterionThe von Mises yield criterion in plane stressNote:1. Application only to isotropic materials.2. Not considering material work hardening.Hypothesis: yielding would occur when the root-mean-square value of the maximum shear stresses reaches a critical valueIn plane stress56Thank you!