1

TRNG I HC K THUT CNG NGHIP KHOA C KH

B MN K THUT C KH

BI GING HC PHN

CHI TIT MY Theo chng trnh 150 TC

S dng cho nm hc: 2009-2010 S tn ch: 03

(Lu hnh ni b)

Bin son: TS V Ngc Pi

TS Nguyn Vn D Ths Nguyn Th Quc Dung Ths Nguyn Th Hng Cm

THI NGUYN 2009

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LI GII THIU

p ng yu cu v ging dy v o to ti Trng i hc K thut Cng

nghip, B mn K thut C kh Khoa C kh tin hnh bin son bi ging mn hc Chi tit my.

Mn hc Chi tit my nghin cu cc vn c s l thuyt nhm xy dng phng php tnh ton thit k hp l cc chi tit truyn ng (bnh rng, ai, xch, trc vt-bnh vt), cc chi tit ni (trc, ), v cc mi ghp (ren, hn, inh tn..) theo cc ch tiu v kh nng lm vic c tin cy, tnh cng ngh v tnh kinh t chp nhn c.

Ni dung ca mn hc c chia thnh 5 ni dung chnh nh sau: Phn I: Nhng vn c bn v thit k my v chi tit my. Phn II: Truyn ng c kh, gm:

- Nhng vn chung v truyn ng c kh ; - Truyn ng ai.

- Truyn ng bnh rng. - Truyn ng trc vt - bnh vt. - Truyn ng xch. Phn III: Cc tit my ni, gm: - Trc. - ln. - trt. Phn IV: Cc tit my ghp, gm:

- Mi ghp then v then hoa. - Mi ghp inh tn. - Mi ghp ren. - Mi ghp hn.

Cun bi ging ny do nhm cc ging vin gm c TS V Ngc Pi, TS Nguyn Vn D, Ths. Nguyn Th Quc Dung v Ths. Nguyn Th Hng Cm ca Khoa C kh, trng i hc K thut Cng nghip bin son. Nhm tc gi rt mong nhn c cc kin ng gp ca cc thy c gio v cc bn sinh vin.

Xin trn trng cm n.

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MC LC Phn I ..................................................................................................................................18 Nhng vn c bn trong thit k my .............................................................................18 Chng 1: i cng v thit k my v chi tit my .......................................................18

1.1. Nhp mn.................................................................................................................18 1.1.1 Khi nim v nh ngha v chi tit my ............................................................18 1.1.2. Nhim v, ni dung v tnh cht ca mn hc ..................................................18 1.1.3. Lch s mn hc v phng hng pht trin...................................................19

1.3 Ni dung, c im v trnh t thit k my v chi tit my....................................20 1.3.1. Ni dung v trnh t thit k my ......................................................................20 1.3.2. Ni dung v trnh t thit k chi tit my ..........................................................20 1.3.3. c im tnh ton thit k chi tit my ............................................................21

1.4. Ti trng v ng sut ...............................................................................................21 1.4.1. Ti trng.............................................................................................................21 1.4.2. ng sut .............................................................................................................22 1.4.3. Quan h gia ti trng v ng sut ....................................................................25

Chng 2: Cc ch tiu ch yu v kh nng lm vic ca chi tit my ............................26 2.1. bn.......................................................................................................................26

2.1.1. Khi nim...........................................................................................................26 2.1.2. Phng php tnh ton bn ...........................................................................26 2.1.2. Tnh bn th tch ...........................................................................................26 2.1.2. Tnh bn b mt .........................................................................................31

2.2. cng.....................................................................................................................32 2.2.1. Khi nim...........................................................................................................32 2.2.2. Tm quan trng ca cng .............................................................................32 2.2.3. Phng php tnh ton cng .........................................................................32 2.2.4. Cc bin php nng cao cng .......................................................................32

2.3 bn mn...............................................................................................................33 2.3.1. Khi nim...........................................................................................................33 2.3.2. Tc hi ca mn.................................................................................................33 2.3.3. Qu trnh mn ....................................................................................................33 2.3.4. Bin php gim mi mn ...................................................................................34 2.2.5. Phng php tnh ton bn mn ...................................................................34

2.4 chu nhit.............................................................................................................34 2.4.1. Khi nim...........................................................................................................34 2.4.2. Tc hi ca nhit ................................................................................................34 2.4.3. Phng php tnh ton v nhit .........................................................................34

2.5 chu dao ng.......................................................................................................35 2.5.1. Khi nim...........................................................................................................35 2.5.2. nh hng ca dao ng n kh nng lm vic ca CTM..............................35 2.5.3. Phng php tnh ton v dao ng v bin php gim dao ng ....................35

Chng 3: tin cy, tnh cng ngh v tnh kinh t ........................................................37 3.1. tin cy..................................................................................................................37

3.1.1. Khi nim v tin cy .....................................................................................37 3.1.2. Cc ch tiu nh gi tin cy.........................................................................37 3.1.3. Phng hng nng cao tin cy...................................................................38

3.2 Tnh cng ngh v tnh kinh t .................................................................................38 Chng IV: Chn vt liu ca chi tit my .........................................................................40

4.1. Yu cu i vi vt liu ............................................................................................40 4.2. Nguyn tc s dng vt liu.....................................................................................40 4.3. Vt liu thng dng trong ch to my .................................................................40

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4.3.1. Kim loi en.......................................................................................................40 4.3.2. Kim loi mu v hp kim ca chng .................................................................40 4.3.3. Kim loi gm .....................................................................................................41 4.3.4. Vt liu phi kim loi ..........................................................................................41

Chng V: Vn tiu chun ha.......................................................................................42 5.1. Khi nim v ngha ................................................................................................42 5.2. Nhng i tng c tiu chun ha trong ngnh ch to my .............................42 5.3. Cc tiu chun hin hnh ..........................................................................................42

Chng VI: Truyn ng ai...............................................................................................43 6.1. Khi nim chung.......................................................................................................43

6.1.1. Khi nim v cu to ........................................................................................43 6.1.2. Phn loi ...........................................................................................................43 6.1.3. u nhc im v phm vi s dng.................................................................44

6.2 Kt cu truyn ng ai ............................................................................................45 6.2.1. Dy ai ...............................................................................................................45 6.2.2. Bnh ai .............................................................................................................46

6.3 C s tnh ton truyn ng ai................................................................................46 6.3.1. Quan h hnh hc chnh .....................................................................................46 6.3.2. Lc tc dng trong truyn ng ai...................................................................48 6.3.3. ng sut trong dy ai.......................................................................................50 6.3.4. Kh nng ko, ng cong trt v ng cong hiu sut ...............................52

6.4 Tnh ton truyn ng ai .........................................................................................53 6.4.1. Ch tiu tnh ton................................................................................................53 6.4.2. Tnh ai dt ........................................................................................................54 6.4.3. Tnh ai thang ....................................................................................................54

6.5 Trnh t thit k ...................................................................................................55 6.5.1. Khi thit k ai dt.............................................................................................55 6.5.2. Khi thit k ai thang.........................................................................................55

Chng 7: Truyn ng bnh rng......................................................................................56 7.1. Khi nim chung.......................................................................................................56

7.1.1. Khi nim..........................................................................................................56 7.1.2. Phn loi ...........................................................................................................56 7.1.3. u nhc im v phm vi s dng.................................................................57

7.2. c im n khp v kt cu ca b truyn bnh rng ............................................57 7.2.1. Cc thng s c bn...........................................................................................57 7.2.2. Cp chnh xc ca b truyn bnh rng.............................................................59 7.2.3. Kt cu bnh rng ..............................................................................................59

7.3. C s tnh ton thit k .............................................................................................60 7.3.1. Ti trng trong truyn ng bnh rng ..............................................................60 7.3.2. Cc dng hng v ch tiu tnh ton...................................................................64 7.3.3. Vt liu, nhit luyn v ng sut cho php........................................................65

7.4. Tnh sc bn b truyn bnh rng tr .......................................................................68 7.4.1. Tnh sc bn b truyn bnh rng tr rng thng ..............................................68 7.4.2. Tnh sc bn b truyn bnh rng tr rng nghing ..........................................72

7.5. Tnh sc bn b truyn bnh rng cn......................................................................74 7.5.1. c im kt cu tnh ton ................................................................................74 7.5.2. Tnh sc bn b truyn bnh rng cn...............................................................75

7.6. Trnh t thit k ...................................................................................................77 Chng 8: Truyn ng trc vt bnh vt ............................................................................79

8.1. Khi nim chung.......................................................................................................79 8.1.1. Khi nim..........................................................................................................79

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8.1.2. Phn loi ...........................................................................................................79 8.1.3. u nhc im v phm vi s dng.................................................................80

8.2. c im n khp v kt cu ca b truyn .............................................................80 8.2.1. Cc thng s hnh hc........................................................................................80 8.2.3. Hiu sut ............................................................................................................82 8.2.4. chnh xc ch to..........................................................................................83 8.2.5. Kt cu b truyn...............................................................................................83

8.3. C s tnh ton b truyn trc vt-bnh vt ...............................................................84 8.3.1. Ti trng trong truyn ng trc vt-bnh vt ....................................................84 8.3.2. Cc dng hng v ch tiu tnh ton...................................................................85 8.3.3. Vt liu v ng sut cho php............................................................................86

8.4. Tnh bn b truyn trc vt-bnh vt ....................................................................89 8.4.1. Tnh bn tip xc ..........................................................................................89 8.4.2. Tnh bn un .................................................................................................90 8.4.3. Tnh kim nghim qu ti ..................................................................................90

8.5. Trnh t thit k ........................................................................................................91 Chng 9: Truyn ng xch ...............................................................................................92

9.1. Khi nim chung.......................................................................................................92 9.1.1. Khi nim..........................................................................................................92 9.1.2. Phn loi ...........................................................................................................92 9.1.3. u nhc im v phm vi s dng.................................................................92

9.2. Cc loi xch truyn ng v a xch.......................................................................93 9.2.1. Cc loi xch truyn ng ..................................................................................93 9.2.2. a xch..............................................................................................................94

9.3. C s tnh ton thit k b truyn xch.....................................................................95 9.3.1. Ti trng tc dng trong b truyn xch ............................................................95 9.3.2. Vn tc v t s truyn .......................................................................................95 9.3.3. S rng a xch .................................................................................................97 9.3.4. Khong cch trc v s mt xch .......................................................................98

9.4. Tnh thit k b truyn xch......................................................................................98 9.4.1. Cc dng hng v ch tiu tnh...........................................................................98 9.4.2. Tnh xch v bn mn ...................................................................................99 9.4.3. Kim nghim xch v qu ti ...........................................................................100

9.5. Trnh t thit k ......................................................................................................100 Phn III .............................................................................................................................101 Chng 10: Trc...............................................................................................................101

10.1. Khi nim chung...................................................................................................101 10.1.1. Cng dng.....................................................................................................101 10.1.2. Phn loi .......................................................................................................101

10.2. Kt cu trc...........................................................................................................101 10.2.1. Kt cu trc....................................................................................................101 10.2.2. Cc bin php nng cao sc bn mi ca trc ...............................................102

10.3. C s tnh ton thit k trc..................................................................................103 10.3.1. Ti trng tc dng ln trc.............................................................................103 10.3.2. ng sut trn cc tit din trc ......................................................................103 10.3.3. Cc dng hng v ch tiu tnh ton...............................................................104 10.3.4. Vt liu trc ...................................................................................................105

10.4. Tnh trc v bn ...............................................................................................105 10.4.1. Tnh trc v bn mi .................................................................................105 10.4.2. Tnh trc v bn tnh.................................................................................108

10.5. Tnh trc v cng.............................................................................................108

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10.6. Trnh t thit k ....................................................................................................109 Chng 11: ln...............................................................................................................110

11.1. Khi nim chung...................................................................................................110 11.1.1. Cng dng v cu to....................................................................................110 11.1.2. Phn loi .......................................................................................................110 11.1.3. u nhc im v phm vi s dng..............................................................111 11.1.4. Cc loi ln thng dung............................................................................111 11.1.5. Vt liu ln..................................................................................................112 11.1.6. K hiu ln..................................................................................................112 11.1.7. Cp chnh xc ln........................................................................................113

11.2. C s tnh ton la chn ln ..............................................................................113 11.2.1. S phn b lc trn cc con ln .....................................................................113 11.2.2. ng sut tip xc trong ln.........................................................................114 11.2.3. Cc dng hng v ch tiu tnh ton...............................................................115 11.2.4. Kh nng ti ca ln....................................................................................115

11.3. Tnh ton ln ......................................................................................................116 11.3.1. Tnh ln theo kh nng ti ng..................................................................116 11.3.2. Tnh ln theo kh nng ti tnh ...................................................................119

11.4. Trnh t tnh ton la chn ln ..........................................................................119 Chng 12: trt...........................................................................................................120

12.1. Khi nim chung...................................................................................................120 12.1.1. nh ngha.....................................................................................................120 12.1.2. Phn loi .......................................................................................................120 12.1.3. u nhc im v phm vi s dng..............................................................120

12.2. Cc phng php bi trn ma st t...................................................................121 12.3. C s tnh ton trt ..........................................................................................121

12.3.1. Kh nng ti ca trt bi trn thy ng.............................................121 12.3.2. Kt cu trt ...............................................................................................122 12.3.3. Cc dng hng v ch tiu tnh.......................................................................124 12.3.4. Vt liu lt ..................................................................................................124

12.4. Tnh ton trt ...................................................................................................125 12.4.1. Tnh trt bi trn ma st t.....................................................................125 12.4.2. Tnh quy c trt ......................................................................................126

12.5. Trnh t thit k ....................................................................................................127 Phn IV .............................................................................................................................128 Chng 13: Ghp bng then v then hoa..........................................................................128

13.1. Mi ghp then .......................................................................................................128 13.1.1. Cng dng, phn loi ....................................................................................128 13.1.2. Then lp lng ................................................................................................128 13.1.3. S lc v then lp cng................................................................................130 13.1.4. Tnh sc bn then lp lng.............................................................................131

13.2. Mi ghp then hoa ................................................................................................132 13.2.1. Gii thiu, cng dng, phn loi....................................................................132 13.2.2. Cc phng php nh tm mi ghp then hoa .............................................133

Chng 14: Ghp bng inh tn ........................................................................................134 14.1. Khi nim chung...................................................................................................134

14.1.1. Gii thiu, phn loi .....................................................................................134 14.1.2. u nhc im v phm vi s dng..............................................................135

14.2. C s tnh ton mi ghp inh tn........................................................................135 14.2.1. Nguyn tc truyn ti trng ...........................................................................135 14.2.2. S phn b ti trng.......................................................................................136

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14.2.3. Cc dng hng v ch tiu tnh ton...............................................................136 14.3. Tnh mi ghp chc...............................................................................................137

14.3.1. Tnh mi ghp chng mt dy inh chu lc ngang ......................................137 14.3.2. Tnh mi ghp nhiu dy inh chu lc ngang ..............................................138 14.3.3. Tnh mi ghp chu m men nm trong mt phng tm ghp .......................138 14.3.4. Tnh mi ghp chu lc v m men nm trong mt phng tm ghp ............139 14.3.5. ng sut cho php .........................................................................................139

Chng 15: Ghp bng ren................................................................................................140 15.1. Khi nim chung...................................................................................................140

15.1.1. Gii thiu, phn loi .....................................................................................140 15.1.2. Cc thng s hnh hc chnh ca mi ghp ren .............................................141 15.1.3. u nhc im v phm vi s dng..............................................................141

15.2. Cc chi tit trong mi ghp ren.............................................................................141 15.3. Tnh mi ghp ren.................................................................................................144

15.3.1. Cc dng hng v ch tiu tnh ton...............................................................144 15.3.2. Tnh bu lng lp lng chu lc dc trc.........................................................144 15.3.3. Tnh bu lng vn cht khng chu lc ngoi..................................................145 15.3.4. Tnh bu lng chu lc ngang ..........................................................................145 15.3.5. Tnh bu lng chu lc lch tm ......................................................................146

15.4. Tnh mi ghp nhm bu lng chu ti trng trong mt phng vung gc vi trc ca bu lng.....................................................................................................................147

Chng 16: Ghp bng hn ...............................................................................................150 16.1. Khi nim chung...................................................................................................150

16.1.1. Gii thiu, phn loi .....................................................................................150 16.1.2. u nhc im v phm vi s dng..............................................................151

16.2. Kt cu mi hn v cch tnh bn ....................................................................151 16.2.1. Mi hn gip mi: kt cu v cch tnh ton bn .....................................151 16.2.2. Mi hn chng: kt cu v cch tnh ton bn..........................................152 16.2.3. Mi hn gc: Kt cu v cch tnh ton.........................................................155

16.3. bn mi hn v ng sut cho php..................................................................157 16.3.1. bn ca mi hn .......................................................................................157 16.3.2. ng sut cho php .........................................................................................157

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CHNG TRNH GIO DC I HC NGNH O TO: CC NGNH K THUT

CHUYN NGNH: CC NGNH KHI NGNH C KH

CNG CHI TIT HC PHN CHI TIT MY Ngi bin son: TS. V Ngc Pi

1. Tn mn hc: Chi tit my (m s MEC306). 2 . S tn ch: 3 3. Trnh cho sinh vin nm th 4 4. Phn b thi gian:

- Ln lp l thuyt: 36 tit - Tho lun: 18 tit

5. Cc hc phn hc trc: Hnh ha v k thut; C hc l thuyt; Sc bn vt liu; Nguyn l my. 6. Hc phn thay th, hc phn tng ng: Hc phn ny thay th cho 2 hc phn Chi tit my 1 v 2 ca chng trnh 180 tn ch. 7. Mc tiu ca hc phn: Mn hc nhm trang b cc kin thc c bn v cu to, nguyn l lm vic v cch tnh ton thit k hp l cc chi tit my c cng dng chung. 8. M t vn tt ni dung mn hc:

Mn hc Chi tit my nghin cu cc vn c s l thuyt nhm xy dng phng php tnh ton thit k hp l cc chi tit truyn ng (bnh rng, ai, xch, trc vt-bnh vt), cc chi tit ni (trc, ), v cc mi ghp (ren, hn, inh tn..) theo cc ch tiu v kh nng lm vic c tin cy, tnh cng ngh v tnh kinh t chp nhn c. 9. Nhim v ca sinh vin:

- D lp 80% tng s thi lng ca hc phn. - T hc v lm bi tp nh - Chun b v tham gia tho lun

10. Ti liu hc tp: - Sch, gio trnh chnh: 1. Bi ging Chi tit my ca B mn K thut c kh, cp nht hng nm.

I HC THI NGUYN TRNG I HC

K THUT CNG NGHIP

CNG HO X HI CH NGHA VIT NAM c lp - T do - Hnh phc

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2. Nguyn Vn D, V Ngc Pi, Nguyn Th Quc Dung, Chi tit my, Trng i hc KTCN Thi nguyn, 2009.

3. V Ngc Pi, Trn Th, Nguyn Th Quc Dung, Nguyn Th Hng Cm, C s thit k my v chi tit my, Trng H K Thut Cng Nghip Thi nguyn, 2001.

4. Trnh Cht, C s Thit k my v Chi tit my, NXB Khoa hc k thut, H ni, 1998.

- Sch tham kho: 1. Nguyn Trng Hip, Chi tit my, T.1 v 2, NXB i hc v Gio dc

chuyn nghip, H ni, 1994. 2. Nguyn Hu Lc, C s thit k my, NXB H Quc gia Thnh ph H Ch

Minh, 2004. 3. Nguyn B Dng, L c Phong, Phm Vn Quang, Bi tp Chi tit My,

NXB i hc v Trung hc chuyn nghip, H ni, 1971. 4. Richard G. Budynas, J. Keith Nisbett, Shigleys Mechanical Engineering

Design, Mc Graw-Hill, 2008. 5. Robert L. Norton, Machine Design, Pearson International Edition, 2006 6. B.. , , 1980. 7. .. , , e

1984. 11. Tiu chun nh gi sinh vin v thang im: *Tiu chun nh gi sinh vin:

- Chuyn cn; - Tho lun; - Kim tra gia hc phn - Thi kt thc hc phn

*Thang im: - Chuyn cn: D lp: 80% tng s gi mn hc mi c thi kt thc hc phn. - Tho lun, bi tp: 20%. - Kim tra gia hc phn: 20%. - Thi kt thc hc phn: 60 %.

12. Ni dung chi tit hc phn: Phn I: Nhng vn c bn trong thit k my v chi tit my

Chng I i cng v thit k my v chi tit my

1.1. Nhp mn 1.1. Khi nim v nh ngha v chi tit my 1.2. Nhim v, ni dung v tnh cht ca mn hc

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1.3. Lch s mn hc v phng hng pht trin 1.2. Khi qut cc yu cu i vi my v chi tit my 1.3 Ni dung, c im v trnh t thit k my v chi tit my. 1.3.1. Ni dung v trnh t thit k my

1.3.2. Ni dung v trnh t thit k chi tit my 1.4 Ti trng v ng sut 1.4.1. Ti trng 1.4.2. ng sut

Chng II Cc ch tiu ch yu v kh nng lm vic ca chi tit my

2.1. bn 2.1.1. Khi nim 2.1.2. Phng php tnh ton bn 2.1.2. Tnh bn th tch 2.1.2. Tnh bn b mt 2.2 cng 2.3 bn mn 2.4 chu nhit 2.5 chu dao ng

Chng III tin cy, tnh cng ngh v tnh kinh t

3.1. tin cy 3.1.1. Khi nim v tin cy 3.1.2. Cc ch tiu nh gi tin cy 3.1.3. Phng hng nng cao tin cy 3.2 Tnh cng ngh v tnh kinh t

Chng IV Chn vt liu ca chi tit my

4.1. Yu cu i vi vt liu 4.2. Nguyn tc s dng vt liu 4.3. Vt liu thng dung trong ch to my

Chng V Vn tiu chun ha

5.1. Khi nim v ngha 5.2. Nhng i tng c tiu chun ha trong ngnh ch to my

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5.3. Cc tiu chun hin hnh Phn II: Truyn ng c kh

Chng VI Truyn ng ai

6.1. Khi nim chung 6.1.1. Khi nim v cu to 6.1.2. Phn loi 6.1.3. u nhc im v phm vi s dng

6.2 Kt cu truyn ng ai 6.2.1. Dy ai 6.2.2. Bnh ai

6.3 C s tnh ton truyn ng ai 6.3.1. Quan h hnh hc chnh 6.3.2. Lc tc dng trong truyn ng ai 6.3.3. ng sut trong dy ai 6.3.4. Kh nng ko, ng cong trt v ng cong hiu sut

6.4 Tnh ton truyn ng ai 6.4.1. Ch tiu tnh ton 6.4.2. Tnh ai dt 6.4.3. Tnh ai thang

6.5 Trnh t thit k Chng VII

Truyn ng bnh rng 7.1. Khi nim chung

7.1.1. Khi nim 7.1.2. Phn loi 7.1.3. u nhc im v phm vi s dng

7.2. c im n khp v kt cu ca b truyn bnh rng 7.2.1. Cc thng s c bn 7.2.2. Cp chnh xc ca b truyn bnh rng 7.2.3. Kt cu bnh rng

7.3. C s tnh ton thit k 7.3.1. Ti trng trong truyn ng bnh rng 7.3.2. Cc dng hng v ch tiu tnh ton 7.3.3. Vt liu, nhit luyn v ng sut cho php

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7.4. Tnh sc bn b truyn bnh rng tr 7.4.1. Tnh sc bn b truyn bnh rng tr rng thng 7.4.2. Tnh sc bn b truyn bnh rng tr rng nghing

7.5. Tnh sc bn b truyn bnh rng cn 7.5.1. c im kt cu tnh ton 7.5.2. Tnh sc bn b truyn bnh rng cn 7.5.3. Trnh t thit k

Chng VIII Truyn ng trc vt bnh vt

8.1. Khi nim chung 8.1.1. Khi nim 8.1.2. Phn loi 81.3. u nhc im v phm vi s dng

8.2. c im n khp v kt cu ca b truyn 8.2.1. Cc thng s hnh hc 8.2.2. Vn tc v t s truyn 8.2.3. Hiu sut 8.2.4. chnh xc ch to 8.2.5. Kt cu b truyn

8.3. C s tnh ton b truyn trc vt-bnh vt 8.3.1. Ti trng trong truyn ng trc vt-bnh vt 8.3.2. Cc dng hng v ch tiu tnh ton 8.3.3. Vt liu v ng sut cho php

8.4. Tnh bn b truyn trc vt-bnh vt 8.4.1. Tnh bn tip xc 8.4.2. Tnh bn un 8.4.3. Tnh kim nghim qu ti 8.4.4. Trnh t thit k

Chng IX Truyn ng xch

9.1. Khi nim chung 9.1.1. Khi nim 9.1.2. Phn loi 9.1.3. u nhc im v phm vi s dng

9.2. Cc loi xch truyn ng v a xch

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9.2.1. Cc loi xch truyn ng 9.2.2. a xch

9.3. C s tnh ton thit k b truyn xch 9.3.1. Ti trng tc dng trong b truyn xch 9.3.2. Vn tc v t s truyn 9.3.3. S rng a xch 9.3.4. Khong cch trc v s mt xch

9.4. Tnh thit k b truyn xch 9.4.1. Cc dng hng v ch tiu tnh 9.4.2. Tnh xch v bn mn 9.4.3. Kim nghim xch v qu ti

9.5. Trnh t thit k Phn III: Cc tit my ni

Chng X TRC

10.1. Khi nim chung 10.1.1. Cng dng 10.1.2. Phn loi

10.2. Kt cu trc 10.2.1. Kt cu trc 10.2.2. Cc bin php nng cao sc bn mi ca trc

10.3. C s tnh ton thit k trc 10.3.1. Ti trng tc dng ln trc 10.3.2. ng sut trn cc tit din trc 10.3.3. Cc dng hng v ch tiu tnh ton 10.3.4. Vt liu trc

10.4. Tnh trc v bn 10.4.1. Tnh trc v bn mi 10.4.2. Tnh trc v bn tnh

10.5. Tnh trc v cng 10.6. Trnh t thit k

Chng XI LN

11.1. Khi nim chung 11.1.1. Cng dng

14

11.1.2. Phn loi 11.1.3. u nhc im v phm vi s dng 11.1.4. Cc loi ln thng dung 11.1.5. Vt liu ln 11.1.6. K hiu ln 11.1.7. Cp chnh xc ln

11.2. C s tnh ton la chn ln 11.2.1. S phn b lc trn cc con ln 11.2.2. ng sut tip xc trong ln 11.2.3. Cc dng hng v ch tiu tnh ton 11.2.4. Kh nng ti ca ln

11.3. Tnh ton ln 11.3.1. Tnh ln theo kh nng ti ng 11.3.2. Tnh ln theo kh nng ti tnh

11.4. Trnh t thit k Chng XII TRT

12.1. Khi nim chung 12.1.1. nh ngha 12.1.2. Phn loi 12.1.3. u nhc im v phm vi s dng

12.2. Cc phng php bi trn ma st t 12.3. C s tnh ton trt

12.3.1. Kh nng ti ca trt bi trn thy ng 12.3.2. Kt cu trt 12.3.3. Cc dng hng v ch tiu tnh 12.3.4. Vt liu lt

12.4. Tnh ton trt 12.4.1. Tnh trt bi trn ma st t 12.4.2. Tnh quy c trt

12.5. Trnh t thit k Phn IV: Cc tit my ghp

Chng XIII GHP BNG THEN V THEN HOA

13.1. Mi ghp then

15

13.1.1. Cng dng, phn loi 13.1.2. Then lp lng 13.1.3. S lc v then lp cng 13.1.4. Tnh sc bn then lp lng

13.2. Mi ghp then hoa 13.2.1. Gii thiu, cng dng, phn loi 13.2.2. Cc phng php nh tm mi ghp then hoa

Chng XIV GHP BNG INH TN

14.1. Khi nim chung 14.1.1. Gii thiu, phn loi 14.1.2. u nhc im v phm vi s dng

14.2. C s tnh ton mi ghp inh tn 14.2.1. Nguyn tc truyn ti trng 14.2.2. S phn b ti trng 14.2.3. Cc dng hng v ch tiu tnh ton

14.3. Tnh mi ghp chc 14.3.1. Tnh mi ghp mt dy inh chu lc ngang 14.3.2. Tnh mi ghp nhiu dy inh chu lc ngang 14.3.3. Tnh mi ghp chu m men nm trong mt phng tm ghp 14.3.4. Tnh mi ghp chu lc v m men nm trong mt phng tm ghp

14.3.5. ng sut cho php Chng XV

GHP BNG REN 15.1. Khi nim chung

15.1.1. Gii thiu, phn loi 15.1.2. Cc thng s hnh hc chnh ca mi ghp ren 15.1.3. u nhc im v phm vi s dng

15.2. Cc chi tit trong mi ghp ren 15.3. Tnh mi ghp ren

15.3.1. Cc dng hng v ch tiu tnh ton 15.3.2. Tnh bu lng lp lng chu lc dc trc 15.3.3. Tnh bu lng vn cht khng chu lc ngoi 15.3.4. Tnh bu long chu lc ngang 15.3.5. Tnh bu long chu lc lch tm

16

15.4. Tnh mi ghp nhm bu lng chu ti trng trong mt phng vung gc vi trc ca bu lng.

Chng XVI GHP BNG HN

16.1. Khi nim chung 16.1.1. Gii thiu, phn loi 16.1.2. u nhc im v phm vi s dng

16.2. Kt cu cc mi hn v cch tnh bn 16.2.1. Mi hn gip mi: kt cu v cch tnh ton bn 16.2.2. Mi hn chng: kt cu v cch tnh ton bn 16.2.3. Mi hn gc: Kt cu v cch tnh ton.

16.3. bn mi hn v ng sut cho php 16.3.1. bn ca mi hn 16.3.2. ng sut cho php 13. Lch trnh ging dy

Tun Ni dung Ti liu Ghi ch

1 Phn I: Nhng vn c bn trong thit k my v chi tit my Chng I: i cng v thit k my v chi tit my Chng II: Cc ch tiu ch yu v kh nng lm vic ca chi tit my

[1], [2], [3], [4], [6]

Ging (5 tit)

2 Chng III: tin cy, tnh cng ngh v tnh kinh t Chng IV: Chn vt liu ca chi tit my

[1], [2], [3], [4], [6]

Ging (5 tit)

3 Tho lun: Phn I Nhng vn c bn khi thit k my v chi tit my

[1], [2], [3], [4], [6]

Tho lun (5 tit)

4 Chng VI: Truyn ng ai Chng VII: Truyn ng bnh rng

[1], [2], [3], [4], [6]

Ging (5 tit)

5 Chng VIII: Truyn ng trc vt bnh vt Chng IX: Truyn ng xch

[1], [2], [3], [4], [6]

Ging (5 tit)

17

6 Tho lun: Chng VI, VII, VIII v IX. Bi tp chng VII v VIII.

[1], [2], [3], [4], [6]

Tho lun (5 tit)

7 Kim tra gia k

8 Chng X: Trc Chng XI: ln

[1], [2], [3], [4], [6]

Ging (4 tit)

9 Chng XII: trt Chng XIII: Ghp bng then, then hoa

[1], [2], [3], [4], [6]

Ging (4 tit)

10 Tho lun: Chng X, XI, XII v XIII. Bi tp chng XI

[1], [2], [3], [4], [5], [6]

Tho lun (4 tit)

11 Chng XIV: Ghp bng inh tn Chng XV: Ghp bng ren

[1], [2], [3], [4], [6]

Ging (4 tit)

12 Chng XV: Ghp bng ren (tip) Chng XVI: Ghp bng hn

[1], [2], [3], [4], [6]

Ging (4 tit)

13 Tho lun: Chng XIV, XV, XVI Bi tp chng XIV, XV v XVI

[1], [2], [3], [4], [5], [6]

Tho lun (4 tit)

18

Phn I

Nhng vn c bn trong thit k my

v chi tit my

Chng 1: i cng v thit k my v chi tit my

1.1. Nhp mn 1.1.1 Khi nim v nh ngha v chi tit my

Chi tit my (hay tit my, vit tt l CTM) l phn t cu to hon chnh ca my m n c ch to ra khng km theo mt nguyn cng lp rp no. Cc chi tit my thng c lp ghp c nh vi nhau thnh nhm chi tit my. thun tin lp ghp, thay th, bo qun v s dng, ngi ta lin kt nhiu chi tit my v nhm chi tit my theo mt chc nng no to thnh cm chi tit my hay b phn my.

Theo quan im s dng, chi tit my c chia thnh hai nhm: - Cc chi tit my c cng dng chung: l cc chi tit my c dng ph bin trong

nhiu loi my khc nhau vi cng dng hon ton ging nhau nu chng cng mt loi. V d nh trc, bnh rng, bu lng, vt, ai c...

- Cc chi tit my c cng dng ring: l cc chi tit my ch c dng trn mt s my nht nh. V d nh pit tng, trc khuu, cam ...

1.1.2. Nhim v, ni dung v tnh cht ca mn hc Chi tit my l mn khoa hc nghin cu cc phng php tnh ton thit k hp l

my v chi tit my c cng dng chung. Mn hc ny nhm trang b cho ngi hc nhng kin thc c bn v cu to, nguyn l lm vic v phng php tnh ton thit k cc CTM c cng dng chung, to c s vng chc vn dng vo vic thit k, s dng, khai thc cc loi my v thit b c kh.

y l mn hc va mang tnh l thuyt va mang tnh thc nghim. L thuyt tnh ton c xy dng trn c s nhng kin thc v ton hc, vt l hc, c hc l thuyt, nguyn l my, sc bn vt liu..., v c xc minh, hon thin qua th nghim v thc tin sn xut.

y cng l mn hc k thut c s mang tnh bn l chuyn t k thut c s sang k thut chuyn mn ca cc ngnh c kh.

Ni dung mn hc gm bn phn chnh sau y: - Phn I - C s tnh ton thit k my v chi tit my. - Phn II - Truyn ng c kh: phn ny gii thiu v cc b truyn c kh bao gm

b truyn ai, b truyn bnh rng, b truyn trc vt-bnh vt v b truyn xch. - Phn III - Cc tit my ni: gii thiu v cc tit my trc, ln v trt. - Phn IV - Cc tit my ghp: gii thiu v mi ghp then v then hoa, mi inh tn,

mi ghp ren v mi ghp hn. hc tt mn hc chi tit my, ngi hc phi bit vn dng sng to l thuyt vo

thc tin; bit phn tch, tng hp, so snh cc phng n nhm gii quyt tt nht cc vn lin quan n thit k, s dng, khai thc my v chi tit my.

19

1.1.3. Lch s mn hc v phng hng pht trin Chi tit my v my c t rt sm v khng ngng pht trin

- Hnh tng v cc chi tit my gin n xut hin t thi c xa trong cc dng c v v kh, trc ht l n by v chm.

- T xa xa loi ngi bit s dng cnh cung, l phi thai ca l xo. - Hn 4000 nm trc, ngi ta dng con ln trong vn chuyn; dng bnh xe, ,

trc trong cc loi xe; dng ti, puli trong cc cng trnh xy dng thp, nh th. - 550 nm trc cng nguyn, Hy lp , bnh rng, trc khuu, pa lng c s

dng. - Hn 200 nm trc cng nguyn, Acsimet s dng vt trong my ko nc. - Hp gim tc truyn ng bnh rng, trc vt s dng rng ri th k th 3. - Di thi trung c nhiu thnh tu khoa hc k thut b mai mt. Sang thi k phc

hng, khoa hc k thut c khi phc, xut hin thm mt s my mi. Bnh rng tr cho, ln, xch, ai, cp, vt nng v khp ni c dng rt ph bin.

- Cui th k 18 u 19 my hi nc ra i, mi ghp inh tn c s dng rng ri.

- Cng t n nay, nhiu my mi ra i; nhiu chi tit my mi xut hin v thay i nhiu lnh vc nh hn, tn, ren vt, truyn ng bnh rng...

L thuyt tnh ton chi tit my xut hin rt sm, khng ngng pht trin v ngy cng hon thin

- L thuyt tnh ton xc nh t s truyn v lc tc dng ra i t thi c Hy lp. - Th k th 3 c ghi chp v hp gim tc truyn ng bnh rng, trc vt. - Thi k phc hng c nhng cng trnh nghin cu v bnh rng tr cho, ln,

xch , bn l, ai, cp, vt nng, khp ni... - Cui th k 19 u th k 20, vi s pht trin mnh ca KHKT, lnh vc C hc

tch thnh nhiu ngnh khoa hc. Cng t y Chi tit my tr thnh mn khoa hc c lp.

- Nhiu nh bc hc ni ting c nhng ng gp xut sc cho khoa hc Chi tit my nh Lna Vanh xi, le, Ptrop, Rynol, Misen, Vilt ...

Phng hng pht trin - Cng nghip pht trin i hi ngy cng nhiu thit b my mc vi trnh t

ng ho cao, i hi khoa hc chi tit my phi c s pht trin ng b. - Ngoi cc phng php tnh ton kinh in, vic ng dng tin hc trong tnh ton

ti u v t ng ho thit k chi tit v b phn my , ang v s ng vai tr ht sc quan trng, nht l trong thi i cng ngh thng tin hin nay.

1.2. Khi qut cc yu cu i vi my v chi tit my

1- Kh nng lm vic Kh nng lm vic l kh nng ca my v chi tit my c th hon thnh cc chc

nng nh. Kh nng lm vic bao gm cc ch tiu: bn, cng, bn mn, chu nhit, chu dao ng, tnh n nh. y l yu cu hng u v cng l yu cu c bn i vi my v chi tit my. 2- Hiu qu s dng

My phi c nng sut, hiu sut cao, tiu tn t nng lng, c chnh xc hp l, chi ph thp v thit k, ch to,vn hnh, s dng, ng thi phi c kch thc v trng lng nh gn. 3- tin cy cao

20

tin cy l tnh cht ca my, b phn my v chi tit my m n m bo cho chng thc hin c chc nng nh, ng thi vn m bo cc ch tiu v hiu qu s dng trong sut thi gian lm vic no hoc trong sut qu trnh thc hin khi lng cng vic nh .

Khi mc c kh ho v t ng ho cng cao th tin cy cng c ngha quan trng. V trong trng hp ch mt c cu hay mt b phn no b hng th c th lm nh tr hot ng ca c dy chuyn sn xut. 4- An ton trong s dng

My v chi tit my c coi l an ton trong s dng khi trong iu kin lm vic bnh thng chng khng gy tai nn nguy him cho ngi s dng hoc khng gy h hi cho cc thit b v cc i tng khc xung quanh. 5/ Tnh cng ngh v tnh kinh t

My v chi tit my c tnh cng ngh v tnh kinh t khi trong iu kin sn xut no chng c ch to ra tn t cng sc nht, c gi thnh thp nht. t c iu cn phi:

- Kt cu ca my, chi tit my phi n gin, hp l, ph hp vi iu kin v quy m sn xut,

- C phng php ch to phi hp l, - Cp chnh xc v nhm ng mc...

1.3 Ni dung, c im v trnh t thit k my v chi tit my. 1.3.1. Ni dung v trnh t thit k my

- Xc nh nguyn tc hot ng v ch lm vic ca my c thit k. - Lp s chung ton myv cc b phn ca my tho mn cc yu cu cho trc. - Xc nh ti trng tc dng ln cc b phn my v c tnh thay i ca chng. - Chn vt liu ch to cc chi tit my. - Tnh ton ng hc, ng lc hc, xc nh hnh dng, tnh ton kt cu s b ca

chi tit my, b phn my tho mn kh nng lm vic; kt hp vi cc yu cu v tiu chun ho, lp ghp, cng ngh v cc yu cu khc xc nh kch thc ca chi tit my, b phn my v my.

- Lp thuyt minh my (bao gm hng dn s dng, vn hnh v sa cha my).

1.3.2. Ni dung v trnh t thit k chi tit my Thit k chi tit my l mt b phn ca thit k my. Ni dung thit k my c

th hin qua trnh t sau: - Lp s tnh ton: v kt cu ca tit my kh phc tp phi c s ho, k c s ti trng. - Xc nh ti trng tc dng ln chi tit my. - Chn vt liu thch hp vi iu kin lm vic ca chi tit my, d kin kh nng gia cng, xem xt cc yu t kinh t lin quan. - Tnh ton cc kch thc ca chi tit my theo theo cc ch tiu ch yu v kh nng lm vic.

- Da theo tnh ton v cc iu kin ch to, lp rp... xc nh kt cu c th ca chi tit my vi y cc kch thc, dung sai, nhm b mt, cc yu cu v cng ngh. - Tnh ton kim nghim theo cc ch tiu ch yu v kh nng lm vic theo kt cu thc v iu kin lm vic c th. Nu thy khng tho mn cc quy nh th phi thay i kch thc kt cu v kim tra li.

21

1.3.3. c im tnh ton thit k chi tit my Trong thc t, vic tnh ton thit k chi tit my thng gp mt s kh khn nh hnh dng chi tit my kh phc tp, kh xc nh chnh xc ti trng, khun kh kch thc, trng lng, gi thnh ch to ph thuc nhiu thng s cha hon ton xc nh. Do vy, khi tnh ton thit k chi tit my cn phi quan tm cc c im sau y:

-Va s dng cng thc l thuyt, va phi s dng cc h s thc nghim thng qua cc th, hnh v v bng biu.

- Tnh ton xc nh kch thc ca chi tit my thng tin hnh qua hai bc: tnh thit k v tnh kim nghim, trong bc tnh kim nghim s quyt nh ln cui cc thng s v kch thc c bn ca chi tit my.

- Trong tnh ton s n s thng nhiu hn s phng trnh. Do , thng phi cn c vo quan h gia lc v bin dng, cn c vo quan h kt cu hoc kt hp vi v hnh gii quyt.

- C th c nhiu gii php cho cng mt mc tiu thit k nn cn phi chn c phng n ti u. Vn ny c gii quyt tt khi s dng cc chng trnh ti u ho v t ng ho thit k chi tit my v thit b c kh trn my vi tnh.

1.4. Ti trng v ng sut 1.4.1. Ti trng

a- Khi nim Ti trng c hiu l tc dng bn ngoi t ln chi tit my trong qu trnh lm

vic. Trong thit k c kh, ti trng l lc v mmen tc dng ln chi tit my. b- Phn loi

Ti trng lm vic: l ti trng thc s tc dng ln chi tit my trong qu trnh lm vic .

Theo tnh cht thay i theo thi gian, ti trng c chia thnh : - Ti trng tnh (hay ti trng khng i) (Hnh 1.1a): l ti trng c phng, chiu, tr s khng thay i hoc thay i khng ng k theo thi gian. - Ti trng thay i (Hnh 1.1b): l ti trng c hoc tr s, hoc phng chiu thay i theo thi gian. y l loi ti trng ph bin trong thc t, trong c ti trng va p (l ti trng t ngt tng mnh ri gim ngay trong khonh khc).

Ti trng thng c biu din di dng biu Q(t) (v d hnh 1.1).

Hnh 1.1: S ti trng Trong tnh ton thit k, ngi ta s dng cc khi nim ti trng danh ngha, ti

trng tng ng v ti trng tnh ton:

Q Q Q1

Q2

Q3

t t t1 t2 t3

Q

0

a) b)

0

22

-Ti trng danh ngha Qdn : l ti trng chn trong s cc ti trng tc dng ln my trong ch lm vic thay i n nh. N dng lm i din cho ch ti tc dng ln my hoc chi tit my. Ngi ta thng chn ti trng danh ngha l ti trng ln nht hoc ti trng tc dng trong thi gian lu nht. V d: Ch ti thay i Qi (t) = Q1 (t1), Q2 (t2), Q3 (t3) nh trn hnh 1.1b c th chn Qdn = Q1= Qmax hoc Qdn = Q2 (t2 = tmax).

-Ti trng tng ng Qt : l ti trng quy c khng i, c tc dng tng ng vi ch ti cho theo mt ch tiu no . Ti trng tng ng c xc nh t ti trng danh ngha thng qua h s tnh ton. V d: Khi tnh theo iu kin bn v kh nng lm vic th ti trng tng ng Qt c xc nh theo cng thc: Qt = QdnKL trong , KL l h s tui th, ph thuc vo mc thay i ti trng v vic chn ti trng danh ngha.

- Ti trng tnh ton Qtt: l ti trng dng tnh ton xc nh kch thc ca chi tit my. Tr s ca n ph thuc vo ti trng tng ng v mt s nhn t nh s tp trung ti trng, ti trng ng, iu kin vn hnh... Ti trng tnh ton thng c biu din d dng:

Qtt = QtKttK Kk Qtt = Qdt KL Ktt K Kk

trong , Ktt l h s tp trung ti trng, phn nh s phn b khng u ca ti; K l h s ti trng ng, phn nh mc ng lc tc dng ln chi tit my; Kk l h s iu kin vn hnh, phn nh iu kin lm vic ca chi tit my v phng thc truyn ti. t K = KL Ktt K Kk vi tn gi h s ti trng, ta c:

Qtt = KQdn Ch : ti trng danh ngha, ti trng tng ng, ti trng tnh ton l cc khi nim ti trng mang tnh quy c dng trong tnh ton v thit k.

1.4.2. ng sut a- Khi nim, phn loi Ti trng tc dng ln chi tit gy nn ng sut trong n. ng sut l cng phn

b ni lc trn n v din tch. n v o ng sut l MPa (1 MPa = 106Pa = 1 N/mm2). Tu theo iu kin lm vic c th, ti trng tc dng ln chi tit my c th gy ra

cc loi ng sut nh: ng sut ko (nn), ng sut un, ng sut ct, ng sut tip xc... Theo c im ph thuc thi gian, ng sut c phn thnh: - ng sut khng i (hay ng sut tnh): l ng sut m chiu, tr s khng thay i

hoc thay i khng ng k theo thi gian. V d ng sut trong dy cp khi treo vt tnh, ng sut trong bu lng sau khi vn cht khng chu lc ngoi. Ni chung, loi ng sut ny t gp trong thc t.

- ng sut thay i : l ng sut c tr s hoc chiu hoc c hai yu t thay i theo thi gian. y l loi ng sut ph bin trong cc chi tit my. b- Chu trnh ng sut, cc thng s c trng ca chu trnh ng sut, phn loi chu trnh ng sut

ng sut thay i c c trng bng chu trnh ng sut. l mt vng thay i ng sut t tr s ban u qua tr s gii hn ny sang tr s gii hn khc ri tr v gi tr ban u. Thi gian thc hin mt chu trnh ng sut gi l chu k ng sut .

Chu trnh ng sut c c trng bng 3 thng s: - Bin ng sut: a = (max - min)/2; - ng sut trung bnh : a = (max + min)/2; - H s tnh cht chu trnh : r = min / max .

Trong , max , min l gi tr max, min ca ng sut.

23

Ch : Khi tnh ton cho ng sut tip, ta thay cc k hiu bng . Phn loi chu trnh ng sut: +Phn loi theo gi tr ca h s tnh cht chu trnh r (hnh 1.2): - Khi r = -1 : chu trnh i xng; - Khi r = 0 : chu trnh mch ng dng, lc ny min= 0; khi r = - : chu k mch

ng m, lc ny max= 0. - Khi r < 0 v r -1: chu trnh khng i xng khc du; khi r > 0 : chu trnh khng i xng cng du (m hoc dng). C th xem chu trnh mch ng l trng hp c bit ca chu trnh khng i xng cng du, trong mt gii hn ca ng sut c gi tr bng 0.

Hnh 1.2: Phn loi chu trnh ng sut theo h s tnh cht chu trnh

+Phn loi theo tnh cht thay i ca ca bin v ng sut trung bnh:

- Chu trnh ng sut n nh: Khi c ng sut trung bnh v bin ng sut u khng thay i theo thi gian. - Chu trnh ng sut bt n nh: Khi ng sut trung bnh, hoc bin ng sut, hoc c hai u thay i theo thi gian.

Ch rng, my c th lm vic n nh ( ch bnh n) hoc khng n nh ( ch khng bnh n) do ng sut trong chi tit my c th thay i n nh hoc thay i bt n nh.

c- ng sut tip xc ng sut tip xc l ng sut sinh ra trn b mt tip xc chung khi cc chi tit my trc tip tip xc nhau v c tc dng tng h i vi nhau. Cn phn bit hai trng hp: tip xc trn din tch tch rng v tip xc trn din tch hp. Khi hai vt th tip xc vi nhau trn din tch tng i rng, ng sut sinh ra vung gc vi b mt tip xc v c gi l ng sut dp hoc p sut. n gin, coi p sut phn b u trn b mt tip xc. Chng hn ti bn l (hoc trt) ng knh d, chiu di l, chu ti hng knh F gy ra p sut po phn b u trn na mt tr i ng vi lc F (hnh 1.3). T iu kin cn bng lc:

r > 0

r =1(0)

r < 0r =- 1

r = 0

r = -

24

ldpddlpF 00 cos22 ==

ng sut dp s c xc nh nh sau:

ldFpd == 0 (1.1)

Khi hai vt th tip xc vi nhau trn mt din tch rt nh: khi mi bt u tip xc l ng -hay gi l tip xc ng- nh khi p hai hnh tr hay hnh tr vi mt phng; hoc khi mi bt u l im - hay gi l tip xc im - nh khi p hai hnh cu hay hnh cu vi mt phng. ng sut php tuyn vng ny phn b theo hnh parabon trong mt ct ngang ca di tip xc. Gi tr ln nht ca ng sut nn ny c gi l ng sut tip xc, k hiu l H v c xc nh theo l thuyt ca Hc. Vic p dng cc cng thc ca Hc i hi vt th (tit my) phi tho mn cc iu kin sau: - Vt liu ng nht v ng hng; - Vt liu lm vic trong vng gii hn n hi, bin dng tun theo nh lut Hc; - Din tch tip xc rt nh so vi b mt vt th; - Lc tc dng c phng php tuyn chung ca hai b mt tip xc. Trng hp tip xc ng (hai hnh tr tip xc nhau - hnh1.4a):

- Vng tip xc c dng hnh ch nht. - ng sut tip xc tnh theo cng thc

Hc:

2qZ HMH = (MPa) (1.2)

Trong , ZM hng s n hi ca vt liu cc vt th tip xc:

)]1(E)1(E[

EE2Z 221

212

21M += ,

Vi, E1, E2 v 1 , 2 l m un n hi v h s Poat xng ca vt liu hnh tr 1 v 2 (MPa); l bn knh cong tng ng:

12

21

= (mm);

Trong , 1 , 2 l bn knh cong ti ng tip xc ban u ca vt th th 1 v th 2 (mm). Cng thc trn ly du + khi tip xc ngoi, ly du khi tip xc trong.

Vi vt liu l kim loi (gang, thp, ng thanh...) h s Pot xng = 0,25 0,35, nu ly trung bnh = 0,3 th cng thc (1.2) c dng :

EqHH 418,0= ( MPa) (1.2.3)

vi, E l m un n hi tng ng, c xc nh theo cng thc sau:

21

21

EEEE2E +=

Trng hp tip xc im (hai hnh cu tip xc (hnh.1.4b) hoc hnh cu tip xc vi mt phng):

- Vng tip xc c dng hnh trn; - ng sut tip xc tnh theo cng thc Hc:

Hnh1. 4: S tnh ton ng sut tip xc

a) Ttip xc ng b) Tip xc im

Fn

Hnh 1.3: S tnh ng sut dp

25

32

2

388,0 EFn

H = (MPa) (1.4) Ch : Cng thc (1.4) s dng khi vt liu ca hai chi tit l kim loi.

1.4.3. Quan h gia ti trng v ng sut Trong iu kin lm vic c th ca chi tit my, cng mt loi ti trng tc dng

(khng i hoc thay i) c th gy nn cc loi ng sut rt khc nhau: ng sut c th l khng i, c th l thay i theo thi gian; c th gy ra ng sut trn b mt, c th gy ra ng sut bn trong chi tit. V vy, khi tnh ton phi xem xt phn tch cho tng trng hp c th.

Cc yu t ti trng v ng sut c tc dng quyt nh i vi kh nng lm vic ca chi tit my. Do vy nh gi ng ti trng v ng sut l vn rt quan trng trong tnh ton thit k v s dng chi tit my v my.

26

Chng 2: Cc ch tiu ch yu v kh nng lm vic ca chi tit my

2.1. bn 2.1.1. Khi nim

bn l kh nng tip nhn ti trng ca chi tit my m khng b ph hng (khng b bin dng d qu mc cho php hoc khng b ph hu). bn l ch tiu quan trng nht i vi phn ln cc chi tit my.

Ngi ta phn bit hai dng ph hng l ph hng tnh v ph hng mi m chng lin quan n bn tnh v bn mi. Ph hng tnh xy ra khi ng sut lm vic vt qu gii hn bn tnh ca vt liu v thng l do qu ti t ngt gy nn. Ph hng mi l do tc dng lu di ca ng sut thay i c gi tr vt qu gii hn bn mi ca vt liu.

Tu theo dng hng xy ra trong th tch hay trn b mt chi tit my, ngi ta phn bit hai loi bn ca chi tit my: bn th tch v bn b mt. trnh bin dng d ln hoc gy hng, chi tit my cn c bn th tch. trnh ph hng b mt lm vic, chi tit my phi c bn b mt.

Khi tnh ton bn th tch cng nh bn b mt, ta ch n tnh cht thay i ca ng sut sinh ra trong chi tit my. Nu ng sut l khng thay i, ta tnh theo bn tnh, nu ng sut l thay i ta tnh theo bn mi.

2.1.2. Phng php tnh ton bn Phng php tnh bn ph bin nht hin nay c tin hnh theo cch so snh

ng sut tnh ton khi chi tit my chu ti (k hiu vi ng sut php v vi ng sut tip) vi ng sut cho php ([] v []).

iu kin bn c vit nh sau: [] hoc [] (2.1)

vi [] = lim /s hoc [] = lim / s (2.2) Trong : lim , lim l ng sut php v tip gii hn, khi t n tr s ny vt liu chi tit my b ph hng; s l h s an ton. Cng c khi tnh bn xut pht t iu kin m bo h s an ton ln hn hoc bng h s an ton cho php:

s [s] (2.3) 2.1.2. Tnh bn th tch 2.1.2. 1. Trng hp ng sut khng i

Tnh ton theo iu kin bn (2.1) vi ch l lim , lim l gii hn bn (i vi vt liu dn) hoc gii hn chy (i vi vt liu do). 2.1.2.2. Trng hp ng sut thay i a) Hin tng ph hng v mi

Khi chi tit my lm vic vi ng sut thay i t ti s chu k ln, n c th b ph hng mt cch t ngt. S ph hng ny xy ra ngay c khi ng sut sinh ra trong n cn nh hn rt nhiu so vi gii hn bn tnh ca vt liu. Hin tng ny thng bt

27

u t nhng vt nt rt nh (vt nt t vi) sinh ra ti vng chu ng sut ln, theo thi gian cc vt nt ny pht trin theo c b rng v b su, lm cho CTM b hng t ngt. Vt hng do mi gy ra trn CTM thng gm hai vng: vng ngoi cha cc ht nh, mn v vng trong cha cc ht th hoc cc th kim loi. b) ng cong mi - Gii hn mi th ng cong mi: Cc nghin cu cho thy gia ng sut ph hng CTM vi s chu k lp li tng ng ca ng sut c quan h xc nh. S chu k ng sut cng ln th ng sut ph hng CTM cng b v ngc li. Bng nhiu th nghim v thng k ton hc, ngi ta thit lp c th biu din quan h gia ng sut (bin ng sut hoc ng sut ln nht) v s chu k ng sut tng ng m mu th c th chu c cho ti khi b ph hu (hnh 2.1). th ny c tn l ng cong mi (hay cn gi l ng cong Vle).

th ng cong mi gm 2 phn: -Phn ng cong c phng trnh:

constNm = (2.4) Trong , l ng sut ph hng (gii hn mi ngn hn) ca CTM; m l bc ca ng cong mi; N l s chu k ng sut ng vi .

-Phn ng thng: Khi gim n tr s r th c th tng N kh ln m mu th vn khng b hng v mi. Quan h ny tng ng vi phn ng thng song song vi trc honh i qua im (r , N0) v c biu din bng phng trnh: r = const. (2.5)

r gi l gii hn mi di hn; N0 l s chu k c s ca vt liu (cc loi thp thng thng c N0 = 106 - 108).

Ch : - a s kim loi mu v hp kim ca chng khng c gii hn mi di hn, tc l

ng cong mi khng c nhnh nm ngang. Nh vy, khi tnh ton chi tit my lm bng kim loi v hp kim mu (v d bnh vt), ngi ta da vo gii hn mi ngn hn. Tuy nhin thc nghim chng t rng kim loi mu d lm vic vi ng sut thp vn b hng sau khi s chu k ng sut kh ln (N > 108).

- Mi vt liu ch nhit luyn nht nh c mt bn mi nht nh. th ng sut gii hn

th ng cong mi Vle c dng ph bin khi tin hnh cc th nghim mi, nhng n khng cho php xc nh cc gi tr ln nht v nh nht ca ng sut trong chu trnh ng sut thay i khng i xng. Chnh hai tr s ny mi xc nh r tr s ng sut thay i lm CTM hng hay khng hng v mi. V vy, khi nghin cu v mi ngi ta thng s dng th biu din mi quan h gia ng sut ln nht v nh nht so vi ng sut trung bnh, v gi l th ng sut gii hn (hnh 2.2). Min nm gia hai nhnh AB v CD l nhng tr s ng sut khng lm hng chi tit.

c) Cc nhn t nh hng ti gii hn mi

Nk N0

k

r

N

m.N=const

Hnh 2.2: th ng sut gii hn

Hnh 2.1: th ng cong mi

28

Gii hn mi c xc nh bng thc nghim. Tuy nhin, trong thc t CTM c nhng sai khc v hnh dng, kch thc, tnh cht c l, c tnh ti trng, trng thi ng sut vv... V vy, khi tnh ton cn k n cc nh hng ny vo gii hn mi c xc nh cho mu th:

-nh hng ca hnh dng kt cu: Hnh dng kt cu c nh hng ln n bn mi ca CTM. Di tc dng ca ti trng, nhng ch c tit din thay i t ngt (nh vai trc, rnh then, l khoan vv... ) c s tp trung ng sut lm cho ng sut thc t ln hn ng sut danh ngha. nh hng c k n bng h s tp trung ng sut:

H s tp trung ng sut l thuyt v xc nh theo cng thc: = max / , = max /

Trong , max , max l ng sut ln nht sinh ra ti ni c tit din thay i; , l ng sut danh ngha ti tit din .

Trn thc t, vic s dng trc tip cc tr s v vo tnh ton nhiu khi khng thch hp. Th nghim chng t rng ti ch tp trung ng sut xut hin trng thi cng khi v do nh hng ca bin dng do nn cc nh nhn ng sut cc b c san bng mt phn tu theo iu kin chu ti. Bn cnh , hiu ng tng bn do hin tng cng ngui trn lp b mt khi gia cng c cng c nh hng n bn mi. Do vy, phi dng h s tp trung ng sut thc t (nh hn so vi h s tp trung ng sut l thuyt) nh gi s tp trung ng sut.

H s tp trung ng sut thc t k v k l t s gia gii hn mi ca mu nhn khng c tp trung ng sut (r , r ) v gii hn mi ca CTM c hnh dng tp trung ng sut (rc , rc ) c ch to cng vt liu v kch thc tit din nh mu:

k = r / r c , k = r / r c Cc gi tr h s ni trn c cho trong cc s tay tnh ton CTM.

- nh hng ca kch thc tuyt i: Kch thc tuyt i ca CTM cng tng th gii hn mi cng gim. Nguyn nhn

l do khi kch thc tng ln th s khng ng u v c tnh vt liu tng ln, CTM c th c thm nhiu khuyt tt. Ngoi ra, khi kch thc CTM tng ln, t l gia chiu dy lp b mt c tng bn nh nhit luyn hoc gia cng c so vi kch thc tng s gim xung.

nh hng ca kch thc tuyt i c c trng bi h s nh hng kch thc . l t s gia gii hn mi ca chi tit c ng knh d v gii hn mi ca mu c ng knh d0 ( thng thng d0 = 7 10 mm):

= r d / r do , = r d / r do Cc h s ny c trong cc s tay tnh ton CTM. - nh hng ca cng ngh gia cng b mt: Lp b mt ca chi tit my sau khi gia cng ct gt (tin, phay, mi...) v gia cng

tng bn (ln p, phun bi v.v...) c nh hng rt ln n gii hn mi. Nguyn nhn l do: - C cc yu t tp trung ng sut nh cc nhp nh, cc vt xc sau gia cng c

hoc pht sinh trong qu trnh s dng; - C cha nhng tinh th b ph hu lm gim sc bn vng b mt; - ng sut khi chu ti un, xon, tip xc u ln hn ng sut lp bn trong; - L ni trc tip chu nh hng ca mi trng. nh gi nh hng ca lp b mt n bn ca chi tit my ngi ta dng h

s trng thi b mt , l t s gia gii hn bn mi ca mu c trng thi b mt nh ca chi tit my (c mi, nh bng hoc tin .., c gia cng tng bn hay khng) vi gii hn mi ca mu c b mt mi m khng c gia cng tng bn.

Ch : b mt chi tit c tng bn th > 1, nu khng c tng bn th 1. - nh hng ca trng thi ng sut:

29

Tnh trng thay i ca ng sut (gi tr ca a , m ) nh hng n gii hn mi trong bin ng sut l thnh phn ch yu gy nn ph hu v mi. Tuy nhin, thc nghim cho thy rng tr s ca ng sut trung bnh cng c nh hng n bn mi ca chi tit my.

T hnh 2.2 ta thy, khi ng sut trung bnh m > 0 , m cng ln th gii hn bin ng sut a cng nh. iu c ngha, khi m tng th a tuy nh cng c th gy nn ph hu mi. Khi ng sut trung bnh m = 0 , gii hn ca bin ng sut bng gii hn mi chu k i xng -1 . Khi ng sut trung bnh m < 0 , a cao hn gii hn bn mi trong chu k i xng -1 . d) Cc bin php nng cao bn mi

trnh cho CTM khng b hng v mi hoc ko di tui th ca n, ngi ta c th dng cc bin php kt cu hoc cc bin php cng ngh.

Cc bin php kt cu: Dng hng v mi l do CTM chu ng sut thay i. Nhng vt nt do mi thng sinh ra nhng ch c tp trung ng sut. Do vy, khi nh kt cu ca CTM cn ch dng cc bin php lm gim tp trung ng sut. C th nh sau: - B tr cc ch gy tp trung ng sut xa cc phn chu ng sut cao ca CTM (nu c th c). - Ti ch ln chuyn tip gia cc bc ca CTM, cn to hnh dng hp l nh dng gc ln trn c bn knh ln nht c th, hoc dng ch ln c cung e - lip. - Dng rnh gim tp trung ng sut. - Khi c rnh then bng, nn dng rnh then ch to bng dao phay a. - Dng then hoa rng thn khai thay cho then hoa rng ch nht. - i vi mi ghp bng di phi vt mp may hoc tng mm ca may p sut gia trc v mp may gim xung, dn n ng sut trong mi ghp phn b u hn v.v...

Cc bin php cng ngh: - Dng cc bin php nhit luyn v ho nhit luyn nh ti b mt, thm than, thm nit v.v... - Dng bin php bin cng ngui nh ln nn, phun bi... - Dng cc bin php gia cng tinh b mt nh nh bng, mi nghin v.v... gim nhm b mt.

e) Cch tnh bn khi chi tit my chu ng sut thay i n nh Tnh ton theo iu kin bn (2.1). Khi CTM lm vic ch di hn, tc khi s chu k chu ti N ln hn hoc bng s chu k c s N0, ng sut gii hn ly theo gii hn mi di hn:

lim=r KhiCTM lm vic ch ngn hn, tc N

30

m 0L N

NK = l h s tui th, k n nh hng ca thi hn phc v v ch ti trng n gii hn mi.

f- Cch tnh bn khi chi tit my chu ng sut thay i bt n nh Gi s CTM chu cc ng sut

thay i 1, 2 ... ng vi cc chu k ng sut tng ng N1, N2...

Khi chu ng sut 1 vi chu k N1 th CTM b ph hng v mi, nhng cng vi ng sut , m ch chu s chu k N1

31

do : m'i

mi

td NN

= (2.6) v tnh ton c a v ch ng sut thay i n nh, c ng sut td xc nh theo (2.6) vi s chu k N = Ni . Nu N N0 th lim=r , nu N < N0 th m 0rlim N

N

= .

Cch tnh ny thng dng tnh chn ln. Ch : C trng hp ngi ta tnh ton tn tht mi thng qua gi tr ti trng [Qi]. Lc , s m m c thay bng m tu theo quan h ti trng vi ng sut. V d, ti gy ng sut ko, nn, un th m= m , ti gy ng sut tip xc ng th m = m/2.

2.1.2. Tnh bn b mt Phng trnh c bn c dng:

H [H] (2.7) Trong , H l ng sut tip xc sinh ra; [H] l ng sut tip xc cho php. a- Khi ng sut tip xc khng i

Tnh ton theo (2.7) vi: ng sut tip xc tnh theo cng thc Hc; ng sut tip xc cho php xc nh bng thc nghim theo iu kin bn tnh trnh bin dng do v gy dn lp b mt. Tnh ln chu ti tnh theo cch tnh ny.

b- Khi ng sut tip xc thay i c c s tnh bn khi CTM chu ng sut thay i, trc tin phi nghin cu dng trc r b mt v mi.

c- Dng hng trc r b mt v mi Xt trng hp hai hnh tr tip xc chu ti v quay trong du bi trn (hnh 2.4).

Bnh dn 1 quay vi vn tc gc 1 , bnh b dn 2 quay vi vn tc gc 2 . Tng im trn b mt cc bnh ln lt chu ti v thi ti, ng sut tip xc cc im ny thay i theo chu trnh mch ng gin on (hnh 2.4d).

ng sut tip xc thay i gy nn hin tng mi lp b mt ca chi tit my. Trn b mt s sinh ra cc vt nt nh. Thc nghim chng t rng km theo chuyn ng ln cn c c trt. Khi b trt cc vt nt nh khng pht trin theo hng vung gc vi b mt tip xc m hng nghing theo chiu ca lc ma st, v l hng ca b mt chu ng sut (tng hp) ln nht (hnh 2.4a). Du bi trn s chui vo cc vt nt. Trn bnh dn 1, du trong cc vt nt s chy ra ngoi khi cc vt nt ny i vo vng tip xc (v b p t chn v pha nh vt nt). Trn bnh b dn 2, do b p v dn t ming v pha chn vt nt nn du khng thot ra ngoi c. p lc du s thc y vt nt pht trin v n mt lc no (sau mt s chu k nht nh) s lm trc ra nhng mnh kim loi nh. Hin tng ny gi l trc r b mt v mi.

Trc r s khng xy ra nu tr s ng sut tip xc khng vt qu tr s ng sut tip xc cho php. d- Tnh bn tip xc - Gii hn mi b mt cng tun theo ng cong mi. - Cch tnh mi b mt theo ng sut tip xc cng tng t nh tnh bn th tch khi ng sut thay i.

Hnh 2.4: C ch trc v mi

1

32

2.2. cng 2.2.1. Khi nim cng ca CTM l kh nng chng li bin dng n hi hoc thay i hnh dng ca n khi chu ti.

Cn phn bit cng th tch v cng b mt. cng th tch lin quan n bin dng ca ton b khi vt liu chi tit cn cng b mt lin quan n bin dng ca lp b mt ca chi tit.

2.2.2. Tm quan trng ca cng cng l mt trong nhng ch tiu quan trng v kh nng lm vic ca CTM. Trong nhiu trng hp, cht lng lm vic ca my c quyt nh bi cng ca CTM. V d trc chnh ca my ct kim loi khng cng s lm tng sai s ca cc sn phm gia cng. Cc trc trong hp gim tc khng cng s b bin dng qu mc cho php, gy tp trung ti trng trn cc bnh rng, gy mn, thm ch lm kt ... Trong thc t, cng c khi kch thc CTM c xc nh theo bn th kh nh, song vn phi ly tng ln nhiu tho mn yu cu v cng, chng hn nh thn my ct kim loi. Yu cu v cng c quyt nh bi: - iu kin bn ca CTM, v d nh tit my quay cn cn bng, tit my chu nn dc trc...

- iu kin tip xc u gia cc CTM: cc bnh rng n khp vi nhau, ngng trc vi trt vv... - iu kin cng ngh, c ngha ln trong sn xut hng lot: ng knh trc cn nh theo kh nng gia cng vv...

- Yu cu m bo cht lng lm vic ca my: v d cng ca cc CTM trong my cng c c nh hng rt ln n chnh xc gia cng.

2.2.3. Phng php tnh ton cng a. Tnh ton cng th tch Trong trng hp cn phi m bo CTM c cng th tch cn thit, tnh

ton v cng nhm gii hn bin dng n hi ca CTM trong mt phm vi cho php. Cc phng trnh tnh ton c bn l:

- Khi chu ko (nn): l [l] (2.8) - Khi chu xon : [] (2.9) - Khi chu un: f [f]; ][ (2.10)

Cch xc nh tr s ca chuyn v khi ko (nn) l, vng f v gc xoay khi un, gc xon khi chu xon c xc nh theo cc cng thc ca Sc bn vt liu.

b. Tnh ton cng tip xc Bin dng tip xc ca cc vt th nhn, ng nht, tip xc ban u theo im

hoc ng c tnh theo l thuyt Hc v Bliap. Bin dng tip xc ca cc vt th c din tch tip xc ln (v d bn trt vi sng my tin vv...) c xc nh bng th nghim.

2.2.4. Cc bin php nng cao cng i vi cng th tch, c th tng cng bng cc bin php sau: - Gim chiu di chu ko (nn), chu xon, chu un (rt ngn khong cch gi;

thm gi ta; trnh dng dm cng xn); - Tng tit din khi chu ko (nn), tng mmen qun tnh tit din khi chu un,

xon; - Dng vt liu c mun n hi ln.

33

i vi cng tip xc, c th tng cng bng cch: - Tng din tch b mt tip xc n mc cn thit; - Dng vt liu c mun n hi ln.

Ch : Khi s dng thp hp kim bn tng nhiu nhng cng hu nh khng tng (do m un n hi hu nh khng thay i) nn phi ch kim tra cng.

Trong thc t, mt s trng hp li yu cu phi gim cng ca CTM. V d, dng bu lng c cng thp, gim cng ca rng v vnh bnh rng vv... s lm tng bn mi ca chng.

2.3 bn mn 2.3.1. Khi nim bn mn l kh nng chng li s suy gim chiu dy lp b mt tip xc ca CTM. Mn l kt qu tc dng ca ng sut tip xc hoc p sut khi cc b mt tip xc trt tng i vi nhau trong iu kin khng c bi trn ma st t.

2.3.2. Tc hi ca mn - Lm gim chnh xc ca my, c bit l dng c o; - Gim hiu sut ca my, c bit l cc thit b ng lc vi h thng pt tng xi

lanh; - Gim bn do cht lng lp b mt mt hiu lc (v d lp nhit luyn, phun

ph, tng bn); - Lm tng khe h ca cc lin kt ng, dn ti ti trng ng tng v gy n; - Mn nhiu c th lm mt hon ton kh nng lm vic ca CTM.

2.3.3. Qu trnh mn Qu trnh mn ni chung c chia lm 3

giai on (hnh 2.5): Giai on I (giai on chy r): s tip xc xut hin ch yu cc im nhp nh li sau gia cng c. Cc im ny s b ct gim chiu cao hoc b bin dng do. Giai on ny kt thc khi chiu rng cc phn tip xc ln hn chiu rng chn cc vt lm. Giai on ny lm phn b u ti trng v thng din ra kh ngn so vi tui th ca CTM. Trn thc t, giai on ny thng do con ngi ch ng tin hnh. mn M (ng 1) tng nhanh v vn tc mn vM (ng2) gim nhanh, nn trong giai on ny cn ch c ch ti, bi trn v lm mt thch hp. Giai on II (giai on mn n nh): mn tng bc nht vi thi gian, tc

mn thp v khng i (on nm ngang ca ng 2): tgdt

dMvM == . Giai on ny l giai on lm vic ca CTM. Trong giai on ny cn ch nh k thay du v bo dng my. Giai on III (giai on mn khc lit): Chi tit my mn rt nhanh. n giai on ny th tui th ca CTM ht, cn thay th hoc phc hi n.

Hnh 2.5: Qu trnh mn (G/- giai on)

G/ II G/ I G/ III

M vM

34

2.3.4. Bin php gim mi mn V mn v tc mn ph thuc vo nhiu yu t, m ch yu l ng sut tip

xc hoc p sut, vn tc trt, h s ma st, chng mn ca vt liu, bi trn . Do , bin php gim mi mn c th l: - Chn vt liu v phi hp vt liu cc b mt i tip hp l gim ma st, thot nhit v chng dnh tt. - Chn ch cng ngh gia cng hp l, thay i c tnh b mt nh nhit luyn, phun ph tng bn, m... - Vn hnh my ng ch , bi trn v che kn tt.

2.2.5. Phng php tnh ton bn mn Tnh ton bn mn xut pht t iu kin bo m ch bi trn ma st t. iu c ngha l khi lm vic, hai b mt tip xc lun lun c ngn cch bi mt lp cht bi trn. Trng hp khng th to thnh bi trn ma st t th phi tnh ton gii hn p sut (hoc ng sut tip xc) gia hai b mt tip xc m bo cho CTM c tui th quy nh.

Gia p sut (hoc ng sut tip xc) v qung ng ma st c quan h: pm. s = const (2.11)

trong , p l p sut (hoc ng sut tip xc); s l qung ng ma st; m l s m, (thng m = 1 3; trng hp ma st t v na t m 3; trng hp ma st kh, na kh v ti ln m =12; trng hp c ht mi, hoc p sut thp, ma st na kh m 1). Biu thc (1.2.14) chng t nu p sut p cng gim th tui th v mn cng tng, c bit khi tr s m cng ln.

C nhiu nhn t nh hng n qu trnh mn. Vic tnh ton n rt phc tp nn hin nay vn cha c phng php tnh chnh xc v bn mn ca CTM. hn ch mn thng quy c tnh theo cch kim nghim iu kin p sut p hoc tch s pv ti b mt lm vic khng c vt qu tr s cho php tng ng:

p [p] (2.12) pv [pv] (2.13)

bn mn (v c bn mi) ca CTM b gim i rt nhiu nu b mt ca n b g. trnh g, c th ph sn chng g, m, phun ph ln b mt chi tit, hoc ch to CTM bng cc vt liu thch hp. Cn c bit ch chng g cho cc CTM lm vic ch m t, c axit hoc baz v.v...

2.4 chu nhit 2.4.1. Khi nim chu nhit ca CTM l kh nng lm vic bnh thng ca n trong mt phm vi nhit cn thit. Trn thc t nhit sinh ra thng l do ma st trong cc c cu v my, c bit l nhng ch chi tit tip xc b trt nhiu, bi trn km.

2.4.2. Tc hi ca nhit - Lm gim kh nng ti ca CTM;

- Lm gim nht ca du bi trn, tng mn v d gy dnh; - Bin dng nhit gy ra cong vnh v lm gim khe h gia cc chi tit ghp; - Lm sai lch chnh xc ca my v dng c o.

2.4.3. Phng php tnh ton v nhit Tnh ton nhit thng kim nghim theo iu kin nhit trung bnh n nh tot b ca my hoc CTM khng c vt qu tr s cho php [tot b]:

35

tot b [tot b] (2.14) Nhit [tot b] c xc nh bng thc nghim tu theo iu kin lm vic c th ca my v CTM hoc xc nh theo nhit cho php ca du bi trn c s dng .

Nhit tot b c xc nh t phng trnh cn bng nhit. Nhit lng sinh ra v nhit lng truyn i trong cng mt n v thi gian l bng nhau:

= (2.15) V d, vi mt b truyn lm vic trong du c th tnh t cng sut mt mt Pm (kW) trong 1 gi bin thnh nhit nng:

= 3600Pm (KJ/h) = )h/Kcal(P18,43600

m 860Pm (kcal/h) (2.16)

Nhit lng truyn i cng trong 1 gi: = At kt ( t - t0 ) (2.17)

Trong : At - din tch b mt thot nhit ra mi trng xung quanh (m2); kt - h s thot nhit (kcal/m2 h 0C ), thng ly kt = 7,5 15 (kcal/m2 h 0C), tu theo tc lu thngca mi trng to nhit; t - nhit ca du (thng khng c qu 75-90oC); t0 - nhit ca mi trng xung quanh (thng ly t0 = 200 C ). Thay (2.16), (2.17) vo phng trnh (2.15) ta c:

860 Pm = At kt (t - t0) (2.18) T cng thc (2.18), khi bit At c th xc nh c nhit t kim nghim iu kin (2.14), hoc vi t cho trc c th xc nh din tch cn lm ngui At . Nu din tch v hp truyn ng c tr s nh hn At tm c th phi tng thm din tch v hoc lm thm gn, cnh tn nhit, hoc dng qut gi vv... Trng hp CTM lm vic nhit cao, khi thit k cn ch chn vt liu v nhit luyn thch hp.

2.5 chu dao ng 2.5.1. Khi nim chu dao ng ca CTM l kh nng lm vic bnh thng ca n trong iu kin c th no m khng b rung ng qu mc cho php. Trn thc t, dao ng thng sinh ra do cc nguyn nhn nh my lm vic c chuyn ng kh hi, vt quay khng cn bng, CTM khng cng, hoc do ngun dao ng t bn ngoi.

2.5.2. nh hng ca dao ng n kh nng lm vic ca CTM - Gy ti trng ng ph c chu k v km theo ng sut thay i lm CTM d b hng v mi. - Lm gim chnh xc ca my, lm gim chnh xc v nhn b mt ca chi tit gia cng. Lm gim tui th ca my v dng c ct. - Gy ting n, nht l b truyn bnh rng v ln.

2.5.3. Phng php tnh ton v dao ng v bin php gim dao ng C th ni dao ng l yu t thng trc, tim n trong qu trnh s dng v khai thc my v CTM. Ni chung, tr cc my s dng dao ng vo qu trnh cng ngh, ngi ta u tm cch loi b hoc gim dao ng. Bin php tt nht kh b dao ng l trit tiu nhng ngoi lc gy nn dao ng, nh cn bng vt quay, nhng ni chung l khng th loi b hon ton. C th gim dao ng bng cch thay i tnh cht ng lc hc ca h thng nh thay i khi lng, mmen qun tnh ca h thng, dng cc thit b gim rung. V vy, vic tnh ton dao ng tp trung theo 2 hng: - Th nht l xc nh tn s ring ca my trnh cng hng sao cho:

f n [f] (2.19)

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trong , f tn s ring ca my; [f] l tn s dao ng cng bc; n l s t nhin (thng n =1; 2 ; 3).

- Th hai l xc nh bin dao ng trnh vt qu mc bin dao ng cho php:

a [a] (2.20) trong : a - bin dao ng tnh ton ca my hoc CTM; [a] - bin dao ng cho php.

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Chng 3: tin cy, tnh cng ngh v tnh kinh t

3.1. tin cy 3.1.1. Khi nim v tin cy tin cy l kh nng sn phm (chi tit my, my, thit b cng trnh...) thc hin chc nng nhim v ca mnh v duy tr chc nng nhim v trong sut thi gian nh ng vi cc iu kin vn hnh bo dng c th. Nh vy, tin cy v kh nng lm vic ca my v chi tit my lin quan cht ch vi nhau. tin cy khng nhng bao hm ni dung chc nng nhim v m cn mang ngha xc sut duy tr kh nng trong sut thi gian quy nh.

3.1.2. Cc ch tiu nh gi tin cy a. Xc sut lm vic khng hng: l xc sut m chi tit my hoc my khng xy ra hng hc trong thi hn nh. Gi s c NC CTM ging nhau, lm vic trong nhng iu kin nh nhau. Sau t gi c NC h chi tit b hng v Nt = NC - NC h chi tit tt th xc sut lm vic khng hng s l:

R(t) = )(1 tQN

NNNN

c

chc

c

t == (3.1) trong , Q(t) = Nc h / Nc l xc sut chi tit hng. Vi mt h thng gm n phn t th xc sut lm vic khng hng R(t) ca h thng s l:

R(t) = R1(t). R2(t)... Rn(t) = )(1

tRin

i= (3.2) T cng thc ny ta thy: - tin cy ca h thng lun lun nh hn tin cy ca phn t t tin cy nht. Do khng cho php tn ti trong h thng mt phn t yu km no m nn gm cc phn t c tin cy nh nhau.

- Cng nhiu yu t, tin cy ca h thng cng thp. Chn hn mt h thng c 10 phn t c xc sut khng hng nh nhau R(t) = 0,96 th xc sut lm vic khng hng ca h thng l : R10(t) = 0,9610 = 0,66. - Nu c 100 phn t th R100(t) = 0,96100 = 0,37. b. Cng hng

Cng hng (t) ti mt thi im t no l t s gia s hng hc trong n v thi gian v tng s Nt tit my c s dng ti thi im . Nu trong khong thi gian kh nh t c Nt h chi tit b hng th cng hng (t) ti thi im t l :

tN

Nt

t

th

=)( (3.3)

Mt cch gn ng, c th coi cng hng l s hng hc trn mt n v thi gian v mt n v sn phm.

t t2 t1

(t)

II III I 0

Hnh 3.1: Quan h gia cng hng v thi gian

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th (t) ( hnh 3.1) chia thnh ba vng ng vi 3 giai on: Vng I: ng vi giai on chy mn; vng II: ng vi giai on s dng bnh thng; vng III: ng vi giai on mn tng cng. c. Tui th Tui th ca CTM l khong thi gian lm vic tnh t khi bt u hot ng cho ti khi t trng thi ti hn (tc l n lc b hng cn sa cha phc hi). Tui th thng tnh theo thi gian hot ng thc t (khng k thi gian khng hot ng) ca CTM.

Trong tnh ton ngi ta cn quan tm n tui th gamma phn trm. l tui th m CTM (i tng nghin cu) lm vic cha t ti trng thi gii hn vi xc sut %. Gia v R(t) c quan h:

= 100 R(t) (3.4) Thng thng trong sn xut hng lot = 90%. Chng hn tui th ca 90% ca mt lot ln l 8000 h, cn 10% c tui th thp hn. d. H s s dng H s s dng l t s gia thi gian lm vic trong mt thi k hot ng no ca CTM v tng thi gian (bao gm c thi gian lm vic, thi gian bo dng v thi gian sa cha phc hi):

pblv

lv

h

lvs ttt

tttK ++== (3.5)

H s s dng KS thng c p dng cho cc CTM c th phc hi c.

3.1.3. Phng hng nng cao tin cy - Gim s lng chi tit, kt cu n gin; tin cy ca tng chi tit phi xp x nhau. - Gim cng chu ti, s dng cc loi vt liu c c tnh cao, dng cc bin php cng ngh tng bn. - Bi trn bo dng tt. - S dng cc h thng tnh nh nhm phn b hp l ti trng. - Cn c thit b an ton. - S dng nhiu cc chi tit tiu chun.

3.2 Tnh cng ngh v tnh kinh t y l mt trong nhng yu cu c bn i vi my v chi tit my. tho mn yu cu v tnh cng ngh v tnh kinh t, chi tit my c thit k phi c hnh dng, kt cu v vt liu ch to chng ph hp vi iu kin sn xut c th, m bo khi lng v kch thc nh nht, tn t vt liu. Chi tit my c ch to tn t cng sc nht v kt qu cui cng l gi thnh thp. Ni cch khc, mt chi tit my c tnh cng ngh cao mt mt phi tho mn cc ch tiu v kh nng lm vic, mt khc trong iu kin sn xut sn c phi d ch to, tn t thi gian v nguyn vt liu nht. Nhng yu cu ch yu ca tnh cng ngh: -Kt cu phi ph hp vi iu kin v quy m sn xut; -Kt cu phi n gin v hp l; -Cp chnh xc v nhm ng mc; -Chn phng php to phi hp l. c khi nim v tnh cng ngh ca mt chi tit my, v d trng hp thit k trc: -ng knh phi nn ly gn st ng knh trc gim khi lng gia cng. -S lng cc bc trn trc cng t cng tt.

39

-Bn knh gc ln nn ly bng nhau. -Chiu di cc on trc c ng knh khc nhau nn ly bng nhau ( c th gia cng nhiu dao ng thi). -Cc rnh then nn b tr trn cng mt ng sinh. -Chiu rng cc rnh then nn c gng ly bng nhau. -Gia cc bc nn c rnh thot ...

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Chng IV: Chn vt liu ca chi tit my Chn vt liu l mt cng vic quan trng, bi v cht lng ca CTM ni ring v ca c my ni chung ph thuc phn ln vo vic chn vt liu c hp l hay khng. Mun chn c vt liu hp l, cn nm vng cc tnh cht ca cc loi vt liu v nm vng cc yu cu m iu kin lm vic ca CTM v iu kin ch to i hi i vi vt liu.

4.1. Yu cu i vi vt liu - Tho mn cc ch tiu ch yu v kh nng lm vic ca CTM nh bn, cng,

bn mn v.v... - m bo cc yu cu v khi lng v kch thc ca CTM. - m bo cc yu cu lin quan n iu kin s dng nh tnh cht chng n mn,

gim ma st, cch in, chu nhit,... - C tnh cng ngh thch hp vi hnh dng v phng php gia cng CTM (c,

hn, dp, ct gt, nhit luyn... - R v d cung ng.

4.2. Nguyn tc s dng vt liu Trong s dng vt liu c 3 nguyn tc c bn sau: - Nguyn tc so snh mt s phng n chn: ch trn c s tin hnh so snh mt s phng n, ta mi c th chn vt liu mt cch hp l. Cc ch tiu so snh la chn c th l: gi thnh thp nht hay khi lng nh nht m vn m bo bn tnh, bn mi hoc cng v.v... cho. Thng thng ngi ta hay ch nhiu n ch tiu v khi lng ca chi tit my v i vi nhiu loi my, n l nhn t quan trng, c trng cho hiu qu ca kt cu, hn na kt hp vi gi mi n v khi lng, ch tiu khi lng cho ta hnh dung r rng v khi lng ca vt liu v gi vt liu ca c kt cu. lm c iu khi chn vt liu v nhit luyn cn ch trng phn tch quan h gia ng sut cho php (hoc c trng c hc) vi khi lng G ca chi tit hay cm my (xem thm [1], [3]). - Nguyn tc cht lng cc b: Chn cht lng tng ng cho tng b phn, trnh s dng vt liu qu him trn lan. - Nguyn tc hn ch s chng loi vt liu: V s chng loi vt liu (cng nh chng loi CTM) cng nhiu th vic cung cp, bo qun, thay th cng phc tp.

4.3. Vt liu thng dng trong ch to my 4.3.1. Kim loi en Kim loi en (gm gang v thp) c dng rng ri nh bn, cng cao v tng i r. Ngoi ra, kim loi en c th nng cao c tnh nh thm cc nguyn t hp kim, nh nhit luyn hoc ho nhit luyn. Nhc im ch yu ca kim loi en l khi lng ring ln (nng n), tnh chng g km.

4.3.2. Kim loi mu v hp kim ca chng Kim loi mu (ng, ch, nhm, thic...) c dng rng ri di dng hp kim mu nh ng thanh, ng thau, babit, uya ra ... u im ca kim loi mu v hp kim ca chng l c kh nng gim ma st, gim mi mn, chng g tt. Mt s hp kim mu c khi lng ring nh. Nhc im ca chng l t v him. Do vy, ch nn dng kim loi mu khi rt cn thit.

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4.3.3. Kim loi gm Kim loi gm l loi vt liu ch to bng cch p nung v nung bt kim loi vi cc cht ph gia p sut cao v nhit cao. N c u im l bn cao, c c tnh c bit (nh kh nng t bi trn...), nhng c kch thc b hn ch bi iu kin ch to, gi thnh t.

4.3.4. Vt liu phi kim loi Vt liu phi kim loi c nhiu loi nh g, da, cao su, aming, cht do... Chng c u im l nh, d to hnh, c tnh cch in, cch nhit, chng n mn ... Tuy nhin, nhc im ca chng l d thay i c tnh theo thi gian (lo ho), nhit lm vic thng thp, d chy.

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Chng V: Vn tiu chun ha

5.1. Khi nim v ngha Tiu chun ho l s quy nh nhng tiu chun, quy cch v hnh dng, loi, kiu, cc thng s c bn, yu cu k thut, mc cht lng... ca sn phm. Trong ngnh ch to my, tiu chun ho c ngha kinh t k thut rt quan trng, v: - Tiu chun ho hn ch c nhiu chng loi v kch thc ca sn phm cng loi cng tn, nh c th s dng cc phng php tin tin nht ch to hng lot CTM tiu chun, gim c sc lao ng, tit kim nguyn vt liu, gim bt u t thit b v cui cng l h gi thnh sn phm. - To iu kin nng cao cht lng sn phm, kh nng lm vic v tui th ca CTM. - m bo c tnh i ln ca CTM, nh to thun li cho vic sa cha thay th cc CTM b hng. - Gim c thi gian nghin cu, tnh ton thit k v ch to. Nh vy, tiu chun ho l mt bin php rt quan trng nng cao cc ch tiu kinh t v cht lng ca my v c nh gi theo mc tiu chun ho: mc TCH = (s chi tit tiu chun)/ (s lng ton b chi tit ca my). 100%

5.2. Nhng i tng c tiu chun ha trong ngnh ch to my - Cc vn chung: cc dy s v kch thc, tc quay trong mt pht, cn, cc k hiu v quy c trn bn v. - Cc thut ng, cc k hiu. - n v o lng. - Cp chnh xc,cht lng b mt CTM. - Hnh dng, kch thc cc CTM thng dng, cc tit my ghp, xch, ai, ln, khp ni, l xo, cc thit b bi trn,... - Cc yu t cu to CTM: ren, mun v dng sinh ca bnh rng, ng knh v chiu rng bnh ai v.v... - Cc thng s, cc ch tiu v cht lng ca my, thit b. - Cc ti liu thit k, ti liu cng ngh.

5.3. Cc tiu chun hin hnh nc ta s dng 4 cp tiu chun: - Tiu chun nh nc Vit nam, k hiu TCVN km theo th t tiu chun v nm ban hnh. Tnh n 31/12/1998, danh mc TCVN bao gm 4440 TCVN. V d TCVN 2247-77 l tiu chun v ng knh ren v bc ren h mt, ban hnh nm 1977. - Tiu chun ngnh, k hiu TCN km theo ngnh tng ng v ni dung. - Tiu chun vng (tnh, thnh ph), k hiu TCV km theo vng tng ng v ni dung. - Tiu chun c s, k hiu TC...y l nhng quy nh ring ca c s sn xut. Trong qu trnh ho nhp vi kinh t th gii, nhiu tiu chun th gii v khu vc v ang c nh hng v c tc dng trc tip vo nc ta, nh trc y tiu chun GOST ca Lin x (c) v tiu chun quc t ISO hin nay.

43

Phn II:

Truyn ng c kh

Chng VI: Truyn ng ai

6.1. Khi nim chung 6.1.1. Khi nim v cu to Truyn ng ai thc hin vic truyn chuyn ng v cng sut gia cc trc nh ma st sinh ra trn b mt tip xc gia cc dy ai vi bnh ai.

Hinh 6.1: Truyn ng ai Dng n gin nht ca truyn ng ai c cu to gm bnh ai ch ng 1, bnh ai b ng 2 v dy ai 3 (hnh 6.1a). Trong mt s trng hp ngi ta dng thm bnh cng ai (hnh 6.1e) nhm tng gc m trn bnh ai v gim nh thit b cng ai.

6.1.2. Phn loi Theo hnh dng tit din dy ai phn ra: - Truyn ng ai dt: tit din dy ai l hnh ch nht, bnh ai hnh tr trn (Hnh 2.2.1a); - Truyn ng ai thang: tit din dy ai hnh thang cn (Hnh 6.1c); - Truyn ng ai lc: tit din ai hnh lc (Hnh 6.1d);

a) b)

c)

d)

e)

f)

1 2

3

44

- Truyn ng ai trn: tit din ai l hnh trn (Hnh 6.1e); - Truyn ng ai rng: truyn lc nh s n khp ca cc rng ca ai vi cc rng trn bnh ai (Hnh 6.1f); Theo v tr tng i v chiu quay ca cc bnh ai phn ra: - Truyn ng ai thng: Truyn ng gia hai trc song song v quay cng chiu (Hnh 61a); - Truyn ng cho: Dy ai bt cho dng truyn ng gia hai trc song song v quay ngc chiu nhau (Hnh 6.2b); - Truyn ng na cho: Dy ai bt na cho dng cho hai trc cho nhau (Thng cho nhau mt gc 900 (Hnh 6.2c); - Truyn ng gc: Dng cho hai trc ct nhau (thng vung gc vi nhau); khi ny cn c bnh i hng (Hnh 6.2d). Trong cc truyn ng k trn, truyn ng ai thng dng ph bin hn c.

Hnh 6.2: Cc s truyn ng ai

6.1.3. u nhc im v phm vi s dng a- u im - C kh nng truyn chuyn ng v c nng gia cc trc xa nhau; - Lm vic m v khng n; - Gi c an ton cho cc chi tit my v ng c khi b qu ti nh hin tng trt trn; - C th truyn chuyn ng cho nhiu trc (h.6.2f); - Kt cu n gin, bo qun d, gi thnh h. b- Nhc im - Khun kh v kch thc ln (vi cng mt iu kin lm vic, ng knh bnh ai ln hn ng knh bnh rng khong 5 ln);

a) b)

d) c)

e) f)

Q

Bnh cng ai

Bnh b dn

Bnh dn

45

- T s truyn khng n nh, hiu sut thp do c trt n hi; - Lc tc dng ln trc v ln do phi cng ai (so vi truyn ng bnh rng ln gp 2 3 ln); - Tui th ca dy ai thp. c- Phm vi s dng - Do thch hp vi vn tc cao nn thng lp u vo ca hp gim tc; - Thng dng khi cn truyn ng trn khong cch trc ln, cng sut truyn dn khng qu 40 50 kw, vn tc vng t 5 n 30 m/ s; - T s truyn u U 5 vi ai dt v u U 10 vi ai thang. 6.2 Kt cu truyn ng ai 6.2.1. Dy ai Yu cu v vt liu dy ai l bn mn, bn mi, h s ma st ln v c tnh n hi cao (m un n hi thp). a- Dy ai dt - Thng dng cc loi vt liu nh si tng hp , vi cao su, si