Transcript
Page 1: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

1

Lect

ure

Not

e 5

Ben

ding

of T

hin

Plat

es

Firs

t Sem

este

r, A

cade

mic

Yea

r 201

2D

epar

tmen

t of M

echa

nica

l Eng

inee

ring

Chu

lalo

ngko

rn U

nive

rsity

Obj

ectiv

es

A

naly

ze b

endi

ng o

f thi

n pl

ates

A

naly

ze fo

r stre

ss a

nd d

efor

mat

ion

in p

late

s su

bjec

ted

to

bend

ing

and

twis

ting

bend

ing

and

twis

ting

A

naly

ze fo

r stre

ss a

nd d

efor

mat

ion

in p

late

s su

bjec

ted

to

dist

ribut

ed tr

ansv

erse

load

s

Ana

lyze

for s

tress

and

def

orm

atio

n in

pla

tes

subj

ecte

d to

co

mbi

ned

load

s

Des

crib

e en

ergy

met

hod

for a

naly

zing

thin

pla

tes

2

Topi

cs

Th

in p

late

s su

bjec

ted

to b

endi

ng, t

wis

ting,

dis

tribu

ted

trans

vers

e an

d in

-pla

ne lo

adin

g

Ben

ding

ofth

inpl

ates

with

asm

alli

nitia

lcur

vatu

re

Ben

ding

of t

hin

plat

es w

ith a

sm

all i

nitia

l cur

vatu

re

Ene

rgy

met

hod

C

hara

cter

istic

sS

ht

fthi

ti

l

3

S

heet

s of

thin

mat

eria

ls

Res

ist m

embr

ane

forc

es a

nd b

endi

ng

Pure

Ben

ding

Des

crip

tions

Th

ene

utra

lpla

nedo

esno

tdef

orm

and

isus

edas

the

4

Th

e ne

utra

l pla

nedo

es n

ot d

efor

m a

nd is

use

d as

the

refe

renc

e pl

ane.

P

lane

s re

mai

n pl

anes

Stra

ins

can

be d

eter

min

ed in

term

s of

z a

nd th

e ra

dii o

f cu

rvat

ure

r.

Dire

ct s

tress

es v

ary

linea

rly a

cros

s th

e th

ickn

ess.

Page 2: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

2

Pure

Ben

ding

Str

ain

5

1(

xx

yz

xzE

2

1)

()

11

(

xx

y

yy

xz

y

Ez

zE

2

1)

()

1y

yx

Ez

Pure

Ben

ding

App

lied

boun

dary

Mom

ents

/2

2/2 /2

2/2

11

()

()

11

1(

)(

)1

t

xx

xt

xy

xy

t

yy

yt

Ez

My

zydz

Mdz

D

Ez

Mx

zxdz

Mdz

D

6

1y

xy

x

3

2Fl

exur

al ri

gidi

ty

12(1

)Et

D

1(

)

1(

)

xx

y

yy

x

MD

MD

Pure

Ben

ding

Def

lect

ion

22

2

22

2

22

2

22

2

11

()

()

11

()

()

xx

xy

y

ww

wM

DD

xx

y

ww

wM

DD

yy

x

7

22

2

22

22

If 0

:

11

1If

:(1

)

yy

yx

y xy

xy

yy

x

ww

My

xM

MM

MD

Ben

ding

& T

wis

ting

Des

crip

tion

8

Page 3: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

3

Ben

ding

& T

wis

ting

Equi

libriu

m

0

cos

sin

sin

cos

nn

xy

xyxy

FMAC

MAB

MBC

MAB

MBC

9

22

co

ssi

nsi

n2

0

sin

cos

cos

sin

sin

2co

s22

0 0

nx

yxy

tt

xy

xyxy

x

n

yt

txy

MM

MM

FMAC

MAB

MBC

MAB

F F

MBC

MM

MM

Ben

ding

& T

wis

ting

Prin

cipa

l Mom

ents

sin

2co

s22

0

Prin

cipa

l mom

ents

and

cur

vatu

res

xy

txy

t

MM

MM

M

10

2ta

n2

xy

xy

MM

M

Ben

ding

& T

wis

ting

Shea

r #1

xyxy

My

yzdz

Mx

xzdz

11

/2 /2

/2 /2

xyxy

t

xy x

xyt

t

yxy

t

Mx

xzdz

Mzdz

Gzdz

M

Ben

ding

& T

wis

ting

Shea

r #2

,

ww

uzv

zx

yv

u

2

2

x xyyx

y wzxy

12

23

2/2

/22

/2/2

32

2

26

(1)

12(1

)

tt

xyxy

tt

wGt

wM

Gzdz

Gz

dzxy

xy

Et

ww

Dxy

xy

Page 4: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

4

Tran

sver

se L

oad

Des

crip

tion

13

She

ar s

train

s ar

e ig

nore

d.

Tran

sver

se L

oad

Equi

libriu

m #

1

/2 /2 /2 /2 0

t

xxz

t t

yyz

t

Qdz

Qdz

F

14

0

()

()

0

0

z

yx

xx

yy

yxF

QQ

Qxy

Qy

Qy

xQ

xqxy

xy

QQ

qx

y

Tran

sver

se L

oad

Equi

libriu

m #

2

/2 /2 /2 /2

t

xx

t t

yy

t

Mzdz

Mxdz

/2 /2

22

2

0

()

()

t

xyyx

xyt

x

xyy

xyxy

yy

MM

xdz

M

MM

Mxy

My

My

xM

xx

yQ

Qy

yy

15

()

()

02

22

0 0

yx

yx

x

xyy

y

xyx

x

QQ

yy

yQ

yxy

Qx

Qqx

yx

MM

Qx

yM

MQ

yx

Tran

sver

se L

oad

Equi

libriu

m #

3

22

20

0xy

yxy

yy

y

MM

MM

QQ

xy

yx

yy

22

2

22

22

00

From

xyxy

xx

xx y

x

xyy

xyx

xy

yx

yy

MM

MM

QQ

yx

xy

xx

QQ

qx

yM

MM

M

16

22

22

2

22

2

xyy

xyx

xyy

x

qxy

yx

xy

MM

Mq

xy

xy

Page 5: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

5

Tran

sver

se L

oad

Dis

plac

emen

t #1

22

22

2

22

22

(),

(

),

(1)

xy

xyw

ww

ww

MD

MD

MD

xy

xy

yx

22

2

22

22

22

22

22

22

22

22

42

4

From

2

()

2(1

)(

)

()

2(1

)

xyy

x

yy

yM

MM

qxy

xy

ww

ww

wD

DD

qxy

xy

xx

yy

yx

ww

w

4

4

()

ww

q

17

42

22

()

2(1

)x

xy

x

24

22

44

4

42

24

()

2

Dy

yxy

ww

wq D

xxy

y

22

22

2(

)q

wD

xy

Tran

sver

se L

oad

Dis

plac

emen

t #2

2

2M

Mw

w

22

22

22

()

()

xyx

x

yxy

y

MM

ww

QD

xy

xx

yM

Mw

wQ

Dy

xy

xy

18

Tran

sver

se L

oad

BC

#1:

Sim

ple

Supp

ort

Free

to ro

tate

, no

defle

ctio

nA

long

aned

gex

2

2

22

22

Alo

ng a

n e

dge

0,

0

M(

)0

BC BC

x ww

wy

yw

wD

xy

19

2

20,

()

0BC

BC

ww

x

Tran

sver

se L

oad

BC

#2:

Bui

lt-in

No

toro

tatio

n,no

defle

ctio

nN

o to

rota

tion,

no

defle

ctio

nA

long

an

edg

ex

0,

0

BC

ww

x

20

Page 6: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

6

Tran

sver

se L

oad

BC

#3:

Fre

e

No

bend

ing

mom

ents

, tw

istin

g m

omen

ts o

r ver

tical

she

arin

g fo

rces

Alo

ng a

n e

dge

()

0(

)0

()

0x

MM

Q

33

32

22

()

0, (

)0,

()

0

()

0

((2

))

0

xBC

xyBC

xBC

xyx

BC

BC

MM

Q

MQ

yw

wx

xy

ww

21

22

()

()

0xBC

BC

ww

Mx

y

Tran

sver

se L

oad

BC

#3:

Fre

e

No

bend

ing

mom

ents

, tw

istin

g m

omen

ts o

r ver

tical

she

arin

g fo

rces

Alo

ng a

n e

dge

()

0(

)0

()

0x

MM

Q

33

32

22

()

0, (

)0,

()

0

()

0

((2

))

0

xBC

xyBC

xBC

xyx

BC

BC

MM

Q

MQ

yw

wx

xy

ww

22

22

()

()

0xBC

BC

ww

Mx

y

Exam

ple

Tran

sver

se L

oad

#1

A si

mpl

y su

ppor

ted

plat

e of

dim

ensi

on a

×b

is s

ubje

cted

to a

un

iform

tran

sver

se lo

ad q

. Det

erm

ine

the

defle

ctio

n an

d be

ndin

g m

omen

t dis

tribu

tions

.

23

Exam

ple

Tran

sver

se L

oad

#2

44

4

42

24

The

defle

ctio

n m

ust s

atis

fy

2w

ww

q Dx

xy

y

2

2

2

2

Bou

ndar

y co

nditi

ons

0 an

d a

t 0

and

0 an

d a

t y0

and

y

Dx

xy

y

ww

xx

ax w

wb

y

24

11

11

Thus

sin

sin

sin

sin

mn

mn

mn

mn

mx

ny

wA

ab

mx

ny

qa

ab

Page 7: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

7

Exam

ple

Tran

sver

se L

oad

#3

00

sin

sin

ab

ab

mx

ny

qdxdy

ab

mx

ny

mx

ny

00

11

0

sin

sin

sin

sin

4

For

sin

sin

ab

mn

mn

mn

a

mx

ny

mx

ny

adxdy

ab

ab

aba

mx

mx

fdx

aa

a

25

00 w

hen

and

w

hen

2

For

sin

sin

0 w

hen

and

w

he2

b

af

mm

fm

m

ny

ny

gdy

bb

bg

nn

f

n n

n

Exam

ple

Tran

sver

se L

oad

#4

44

4

42

24

20

ww

wq D

xxy

y

42

24

24

22

()

2()

()

()

0

()

()

0

1

mn

mn

mn

mn

am

mn

nA

aa

bb

D

am

nA

ab

D

26

42

22

11

11

1si

nsi

n(

/)

(/

)

sin

sinmn

mn

mn

mn

amx

ny

wa

bD

ma

nb

mx

ny

qa

ab

Exam

ple

Tran

sver

se L

oad

#5

20

0

416

sin

sin

ab

mn

qmx

ny

qa

dxdy

aba

bmn

62

22

1,3,5

1,3,

5

max

62

22

1,3,

51,3

,5

16si

n(/

)sin

(/

)

(/

)(

/)

16si

n(/2

)sin

(/2

)at

/2

,/2

(/

)(

/)

mn

mn

aba

bmn

qmxa

nyb

wD

mnma

nb

qm

nw

xa

yb

Dmnma

nb

27

,,

,,

max

(/

)(

/)

0.04

43

mnma

nb

wq

4 3

if

,0.

3a

ab

Et

Exam

ple

Tran

sver

se L

oad

#62

2

42

22

1,3,

51,

3,5

22

(/

)(

/)

16si

nsi

n(

/)

(/

)

(/

)(

/)

xm

n

ma

nb

qmx

ny

Ma

bmnma

nb b

22

42

22

1,3,5

1,3,

5

,max

,max

,max

,max

(/

)(

/)

16si

nsi

n(

/)

(/

)

at

/2,

/2

0

ym

n

xy

xy

ma

nb

qm

xny

Ma

bmnma

nb

MM

xa

yb

MM

2.0

479

if

,0.

312

12y

x

qaa

b

Mz

Mz

28

33

,max

,max

22

2

,max

,max

2

,

66

, a

t 2

0.28

71 if

,

0.3

yx

xy

yx

xy

xy

ttM

Mt

zt

t aq

ab

t

Page 8: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

8

Com

bine

d Lo

adin

gs D

escr

iptio

ns

Com

bine

d lo

ads

Tl

d

Tran

sver

se lo

ads

In

-pla

ne fo

rces

29

Com

bine

d Lo

adin

gs E

quili

briu

m #

1

0yx

xN

N xy

0xy

yN

Nx

y

30

2

20

()

cos(

)co

s()

()

0

xx

xx

yxyx

yx

Nw

ww

FN

xy

xN

yx

xx

xN

Ny

xN

xy

Com

bine

d Lo

adin

gs E

quili

briu

m #

2

2xy

Nw

ww

31

2 2

()

()

()

()

((

))xy

z

xyxy

zxy

xy

xyxy

yxyx

zyx

Nw

ww

NN

xy

xN

yx

xxy

yN

ww

Nxy

xy

xy

xy

Nw

wN

Nxy

xy

xy

yx

N

Com

bine

d Lo

adin

gs E

quili

briu

m #

3

2N

ww

w

32

2

2

2

2

2

()

()

()

()

()

()

xxz

xx

xx

yyz

y

xz

Nw

ww

NN

xy

xN

yx

xx

xN

ww

Nxy

xy

xx

xN

ww

NN

xy

xy

yy

N

y

Page 9: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

9

Com

bine

d Lo

adin

gs E

quili

briu

m #

4

()

()

()

()

zz

zxy

zyx

zxz

yz

RF

RN

NN

N

2

22

22

22

2

22

)2

(2

)

xyxy

zxy

yx

xy

zx

yxy

z

NN

ww

wR

xy

Nxy

xy

xy

xy

yx

NN

ww

ww

Nxy

xy

Nxy

xy

xx

yy

xy

ww

wR

NN

Nxy

xy

xy

R

33

from

yx

x

xy

xy

NN x

y

0

and

0 an

d in

tran

sver

se lo

adxy

yN

Nx

y

44

42

22

42

24

22

12

(2

)x

yxy

ww

ww

ww

qN

NN

Dxy

xxy

yx

y

Initi

al C

urva

ture

Des

crip

tions

01

04

44

11

14

22

4

Ass

ume

tota

l def

lect

ion

as

the

sum

e of

initi

al

2

ww

ww

ww

w

42

24

22

20

10

10

12

2

2

0

()

()

()

1(

22)

Initi

al c

urva

ture

is e

quiv

alen

t to

the

appl

icat

ion

of

xy

xy

x

xxy

yw

ww

ww

wq

NN

ND

xy

xy

qN

22

00

02

22

yxy

ww

wN

Nxy

xy

34

01

1

12

62

22

21

1

sin

sin

, if

is c

ompr

essi

ve,

0

sin

sin

, (

/)

(/

)

mn

xy

xym

n

mn

xmn

mn

mn

x

xy

xy

mx

ny

wA

NN

Na

bAN

mx

ny

wB

Ba

bDa

mna

mb

N

Ener

gy M

etho

d D

escr

iptio

ns

35

22

2

22

22

22

2

22

22

1(

2)

2

From

(

),(

),(1

)

xy

xy

xy

xy

ww

wU

MM

Mxy

xy

xy

ww

ww

wM

DM

DM

Dxy

xy

yx

Ener

gy M

etho

d B

endi

ng a

nd T

wis

ting

22

22

22

22

22

22

22

22

22

2

()

()

22(

1)(

)2

For a

re

ctan

gula

r pla

tea

b

Dw

ww

ww

Uxy

xy

xy

xy

ab

Dw

ww

ww

36

22

22

22

00

2

2

((

)2(

1)

()

2

For b

endi

ng o

nly,

0

(2

ab

xy

Dw

ww

ww

Udxdy

xy

xy

xy

M

Dw

Ux

22

22

22

20

0(

)2

ab

ww

wdxdy

yx

y

Page 10: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

10

Ener

gy M

etho

d Tr

ansv

erse

Loa

d

00

()

ab

Vwqxy

Vwqdxdy

37

Ener

gy M

etho

d In

-pla

ne L

oads

#1

22

21

(1(

))

2

ax

ww

xx

a

38

2

0

2

0

2 1(1

()

)2 1

()

2(

)

a

a xx

xw

adx

x wa

adx

xV

Ny

Na

ay

Ener

gy M

etho

d In

-pla

ne L

oads

#2

21

()

ab

wV

Ndxdy

39

2

00

2

00

()

2 1(

)2

xx

ab

yy

VN

dxdy

x wV

Ndxdy

y

Ener

gy M

etho

d In

-pla

ne L

oads

#3

1 2 1 2

xyxy xy

xy

ww

VN

xx

yw

wN

yV

40

00

22

00

0

2 12

21

()

()

22

xy ab

xyxy

ab

b

xy

xyx

y

x

xy

yyx

y ww

VN

dxdy

xy

ww

ww

VV

VV

NN

Ndxdy

xy

xy

Page 11: Pure Bending - Chulalongkorn University: Faculties and ...pioneer.netserv.chula.ac.th/~mkuntine/45-321/files/ch5-4.pdf · 1 Lecture Note 5 Bending of Thin Plates First Semester, Academic

11

Exam

ple

Ener

gy #

1

A si

mpl

y su

ppor

ted

plat

e of

dim

ensi

on a

×b

is s

ubje

cted

to a

un

iform

tran

sver

se lo

ad q

. Det

erm

ine

the

defle

ctio

n an

d be

ndin

g m

omen

t dis

tribu

tions

.

1

22

22

22

22

22

20

0

sin

sin

((

)2(

1)

()

2mn

m

abm

xny

wA

ab

Dw

ww

ww

UV

dxdy

xy

xy

xy

41

00

62

22

1,3,

51,

3,5

2

()

16si

n(/

)sin

(/

)

(/

)(

/)

ab

mn

xy

xy

xy

wqdxdy

qmxa

nyb

wD

mnm

U

anb

V


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