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NHM 5CC PHNG PHP TH NGHIM VT LIU

Nguyn Anh QuangV1002583THNH VINTrng Quc TnK1002917Phm Minh Thun 41003294Bi Quan Hng 91001302 Phng Minh Phc V1002474

Tng quanNI DUNG CHNHPhng php koPhng php nnPhng php xonCc phng php khc

Tng quan

ng sut v bin dng

ng sut v bin dng th v mi quan h gia ng sut v bin dng trn thc t v theo k thut nh hnh sau:

ng sut v bin dng

Gii hn chy doc xc nh bng cch dng ng i qua im trn trc honh c = 0.2% song song vi ng OA cho ct th ( ). Tung ca giao im thu c cho ta gii hn chy do.

Quan h gia nhit v bin dng

II. PHNG PHP KOPhng php ko l mt trong nhng phng php c bn nht trong xc nh c tnh ca vt liu trong gia cng k thut.Nhn chung khi nhc n l thuyt v ko, ta c th chia lm 2 nhm l thuyt chnh: ko khi v ko tm.

II. PHNG PHP KO1.L thuyt v ko khi Phng php tin hnh th nghim l iu khin chuyn v (load controlled) Mu th nghim ko Ngun: http://bainite.wordpress.com/2007/05/29/blue-steel/

II. PHNG PHP KO1.L thuyt v ko khi Kt qu o c trong th nghim s cho ta ng cong k thut ng ng sut-bin dng k thut Ngun: [3]

II. PHNG PHP KO1.L thuyt v ko khi ng cong trn c xy dng t 2 cng thc c bn: ng sut :z = P/A0 (Lc / din tch ban u). Bin dng di tng i: e = L/L0 ( bin dng di/ chiu di ban u)

II. PHNG PHP KO1.L thuyt v ko khi *ng sut chu ko ti a (Ultimate tensile stress): thng c s dng nh gi kh nng chu lc ko ca vt liuGii hn chy do (ng sut chy do), thng c ly mc ngoi lc P sao cho bin dng do tng ng mc 0.10.2%, t ta c

II. PHNG PHP KO1.L thuyt v ko khi *ng cong ng sut-Bin dng thc Bin dng ca vt liu khi chu ko nhm tho iu kin v bo ton vt chtNgun:http://www1.us.elsevierhealth.com/books.elsevier/companionsites/JenkinsKhanna/mmd/axial-tension/axial_tension_2a.html

II. PHNG PHP KO1.L thuyt v ko khi T , ngi ta ra mt cng thc khc, c tnh n s thay i din tch mt ct ngang nh sau:*ng cong ng sut-Bin dng thc

II. PHNG PHP KO1.L thuyt v ko khi *ng cong ng sut-Bin dng thc S khc bit gia ng cong k thut v ng cong thcNgun:http://oregonstate.edu/instruct/engr322/Homework/AllHomework/S07/ENGR322HW2.html

II. PHNG PHP KO1.L thuyt v ko khi *ng cong ng sut-Bin dng hiu chnh Kt qu th nghim ng vi 2 loi vt liu khc nhauNgun:http://www.hsc.csu.edu.au/engineering_studies/application/lift/3210M phng s hnh thnh nt tht th nghim koNgun:http://www.schenectady.k12.ny.us/users/pattersont/IBDT%20Website/year1.html

II. PHNG PHP KOKhi thc hin tnh ton v ng sut nu c s hnh thnh v nt tht, Bridgman a n cc cng thc sau :

trong a l bn knh ca mt ct ngangR l bn knh nt thtx l gi tr ng sut thc1.L thuyt v ko khi *ng cong ng sut-Bin dng hiu chnh

II. PHNG PHP KO1.L thuyt v ko khi *ng cong ng sut-Bin dng hiu chnh 3 ng cong m ta xy dng v s khc bit gia chngNgun: http://www.studyblue.com/notes/note/n/chapter-7-mechanical-properties/deck/3929258

II. PHNG PHP KO2.L thuyt v ko tm Mt mu th nghim dng tm dng trong th nghim koCc thng s c lu s l w=w-w0 v l=l-l0

II. PHNG PHP KO2.L thuyt v ko tmMt v d v ng Lc-Bin dng ca vt liu dng tm.* gin di ti a ETot (Total Elongation): c tnh bng cng thc sau

II. PHNG PHP KO2.L thuyt v ko tmng cong ng sut-Bin dng k thut v thc ca th nghim ko tm *ng cong k thut-ng cong thc:

II. PHNG PHP KO2.L thuyt v ko tmH s bn (strength coefficient) H s bin cng ca vt liu tm (strain hardening index) : n.

Biu din ng sut v bin dng theo hm log n l h s gc ca on bin dng do log K l hng s ban u ca ng thng

II. PHNG PHP KO2.L thuyt v ko tm*Tnh bt ng hng ca dng tm phng M phng qu trnh cn v s bt ng hng ca vt liu dng tm Chnh qu trnh to hnh lm cho sn phm dng tm c tnh bt ng hng.

II. PHNG PHP KO2.L thuyt v ko tmCc v tr khc nhau ca mu th trong ko vt liu tm v s khc bit ca chngGi tr R (R-value) dnh cho vt liu bt ng hng

II. PHNG PHP KO2.L thuyt v ko tmH s bt ng hng phng

Gi tr R trung bnh, cn gi l t s bt ng hng cng c tnh theo cng thc

II. PHNG PHP KO3. Cc phng php th nghim ko*Phng php thng thngMc ch:Thc hin th nghim ko nhm thu c biu ng sut bin dng, xc nh cc thuc tnh ko v nh vy thu c thng tin v cc ng x c hc ca vt liu.H thng th nghim: Mt thit b th nghim ko

II. PHNG PHP KO3. Cc phng php th nghim ko*C xt ti nh hng ca nhit :Thit b ko c nghin cu tc ng ca nhit H thng kim tra Gleeble:

II. PHNG PHP KO3. Cc phng php th nghim ko*C xt ti nh hng ca nhit :Mc tiuVt liu ng x khc nhau nhit khc nhau. i vi mt s vt liu gin, to hnh c bng phng php ko l mt vic kh khn nhit thng. Do , phng php th nghim ny cho ta mt gi tr nhit ca cc vt liu m ti ta c th to hnh chng theo mong mun tuy nhin s khng hon ton lm mt i c tnh ca vt liu sau khi lm ngui.

II. PHNG PHP KO3. Cc phng php th nghim ko*C xt ti nh hng ca nhit : nh hng ca nhit n qu trnh ko ca 1 vt liu

II. PHNG PHP KO3. Cc phng php th nghim ko*C xt ti nh hng ca nhit :nh hng ca gia nhit n s thay i nhit tch mt ct ngang

Tng quanNI DUNG CHNHPhng php koPhng php koPhng php xonCc phng php khcPhng php nn

III.Phng php nn 1.Mc chXc nh phn ng ca vt liu bng cch o cc thng s.

=>m t cc thuc tnh ca vt liu, kh nng hot ng ca sn phm

Cc lnh vc ng dng :

2. ng x ca vt liu v cc cng thc tnh ton

Cc thng s c bn:Ni lc :

Bin dng di tng i:

ng sut:

Nng lng bin dng:

Thit b th nghim

3.Phng php th nghim v thit b th nghim

Phng php Ring Compression TestCc phng php nn nng (Hot-Compression Test)Kt qu th nghim

Plain-Strain Compression TestKhi m ma st b mt kh cao, phng php ny thch hp i i mu dng tm hoc a mng. B rng nn gp 6-10 ln b ngang

IV. PHNG PHP XON

C 2 loi th nghim vt liu bng phng php xon: phng php xon thng thng v phng php xon nng

1.C s l thuyt ca phng php xona.Phng php xon thng thngC 2 loi ph hy:+ Ph hy phn b (Fracture-controlled failures): bin dng phn b tng i ng u trc khi xy ra h hng+ Ph hy tp trung (Flow-localization-controlled failures) : bin dng tp trung trong mt khu vc c th ca mu vt bng kim loi hoc phi trc khi qu trnh nt gy xy ra

Kim loi mi thng c ch to trong mi trng c nhit cao. Vic la chn nhit bao nhiu c th lm cho cu trc vi m v tnh cht vt liu khng t c kh nng cao nht ca vt liu.Phng php xon nhit l mt phng php th nghim vt liu di mt mi trng c nhit cao nhng kim sot c.

1.C s l thuyt ca phng php xon b.Phng php xon nng

2.Cc thng s c th xc nh ca.Phng php xon thng thng

iu kin hnh thnh nn s ph hy tp trungTc bin dngng sut bnng sut n hi do ca vt liu

iu kin hnh thnh nn s ph hy tp trungTc bin dngng sut bnng sut n hi do ca vt liuNhit ph hy

2.Cc thng s c th xc nh cb.Phng php xon nhit

Thit b th nghim

3.Phng php v thit b th nghima.Phng php xon thng thng

Thit b th nghim

3.Phng php v thit b th nghimb.Phng php xon nng

Thit b th nghim

3.Phng php v thit b th nghimb.Phng php xon nhit

Tng quanNI DUNG CHNHPhng php nnPhng php koPhng php xonCc phng php khc

C 5 phng php:1. Phng php Cupping Test2. Phng php LDH Test3. Phng php Hydraulic Bulge Test4. Phng php thc nghim o h s ma st5. Phng php C nhit

V.Mt s phng php th nghim vt liu khc

1.Phng php Cupping TestDng xc nh gii hn ko (gin) ca mt vt liuKt qu th nghim c hnh dng nh mt chic tch nn c tn gi nh trn. Thc t, phng php ny cng c chia thnh nhiu phng php th nghim khc nhau, c th l Erichsen chu u, Olsen M, sau ny cn c phng php Fukui.

1.Phng php Cupping Testhttp://thelibraryofmanufacturing.com/sheetmetal_basics.html

1.Phng php Cupping Test

1.Phng php Cupping TestS khc bit gia 3 phng php [3]

2.LDH Test khc phc s thiu chnh xc khi xc nh bn knh cong, ngi ta ra thm mt thng s khc cng lin quan n th nghim ny l gii hn chiu cao nh nn LDH (Limit Dome Height)Ta s o chiu cao ln nht ca hnh nn ta to thnh, qua tm ra gi tr di tng thm ca mu vt.

So snh kt qu tm c bng LDH Test vi cc l thuyt khc [3] (Phn mi tn l gi tr LDH o c ca cc loi vt liu)

3.Hydraulic Bulge Test

Kim tra mi quan h gia ng sut v bin dng, c xt n s thay i b dy ca mu vt dng tm phng, khng c h s ma st gia vt nng v mu, qua cho kt qu chnh xc hn cc phng php thng thng khc.

4.Phng php thc nghim o h s ma st

5.Phng php C nhit (THERMOMECANICHAL PROPERTIES TEST)Cc phng php c nhit dng o lng, c lng cc gi tr c trng ca vt liu c nh hng trong qu trnh gia cng v to hnh: nhit dung ring, h s gin n v nhit, h s khuch tn nhit , khi lng ring.

a.Nhit dung ring Enthalpy (H): tng nhit lng ( hay nng lng) khi ng p. T cho ta khi nim v nhit dung ring ng p Cp l s thay i ca Enthalpy theo nhit

5.Phng php C nhit (THERMOMECANICHAL PROPERTIES TEST)

DSC cho ta kt qu chnh xc hn, tuy nhin quy trnh th nghim v thit b li phc tp hn.


b.Khi lng ring v h s nhit gin n H s nhit gin n (CTE) cho ta kh nng gin n di ca vt liu vi mi n v nhit thay i. 3 phng php chnh xc nh CTE l s dng Quartz Dilatometer, Vitreous Silica Dilatometer v Interferometer.


c.H s truyn nhit H s ng x nhit Vi K l h s ng x nhit, D l h s truyn nhit, Cp l nhit dung ring ng p v l khi lng ring ca vt liu, ta c


C 2 phng php thng c s dng xc nh cc h s ny l phng php o dng nhit vi cc a (Heat Flow Meter and Guarded Plate Method) v phng php laser (Laser Flash Technique).


Vi h s truyn nhit, phng php n gin v hiu qu nht c s dng l o c s khc bit v nhit ca mu vt ti nhng v tr khc nhau theo tng khon thi gian khc nhau. T xy dng m hnh truyn nhit v tnh ra thng s ta cn. Ngoi ra, khi c y cc yu t trn, vic tnh ton h s truyn nhit l u hon ton c th thc hin c.


Thanks for your attention

References*Cc ti liu tham kho chnh[1] Improvement of the characterisation method of the johnson-cook model- MAXIME JUTRAS[2] Mechanics of Sheet Metal Forming-Z. Marciniak , J.L. Duncan, S.J. Hu[3] _2011. Metal_Forming__Mechanics_and_Metallurgy- William F.Hosford, Robert M.Caddell[4] Handbook of Workability and Process Design- George E.Dieter, Howard A.Kuhn, S.Lee Semiatin[5] C hc ph hu -Trng Tch Thin[6] DETERMINATION OF FLOW STRESS BY THE HYDRAULIC BULGE TEST - J. SLOTA, E. SPISK

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