tensile tests

29
Lecture Note 1.1 Stress and Strain First Semester, Academic Year 2012 Department of Mechanical Engineering Chulalongkorn University Objectives #1 Describe basic features of elasticity in Cartesian coordinates Relate deformation to strains and loads to stresses Describe behaviors in stress strain diagrams and Describe behaviors in stress-strain diagrams and determine stress/strain histories Describe the characteristics and properties of stress and strain components as tensor quantities Relate stress and strain components for linear elastic materials in 2D and 3D 2 T&C Tests Tensile Tests Diagrams 3 keywords: stretching, lateral contraction necking, region of necking fracture, region of fracture Stress – Strain Diagrams Diagrams 4

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Page 1: Tensile Tests

Lect

ure

Not

e 1.

1

Stre

ss a

nd S

trai

n

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 #1

D

escr

ibe

basi

c fe

atur

es o

f ela

stic

ity in

Car

tesi

an c

oord

inat

es

Rel

ate

defo

rmat

ion

to s

train

s an

d lo

ads

to s

tress

esD

escr

ibe

beha

vior

sin

stre

ssst

rain

diag

ram

san

d

Des

crib

e be

havi

ors

in s

tress

-stra

in d

iagr

ams

and

dete

rmin

e st

ress

/stra

in h

isto

ries

D

escr

ibe

the

char

acte

ristic

s an

d pr

oper

ties

of s

tress

and

st

rain

com

pone

nts

as te

nsor

qua

ntiti

es

Rel

ate

stre

ss a

nd s

train

com

pone

nts

for l

inea

r ela

stic

m

ater

ials

in 2

D a

nd 3

D

2

T&C

Tes

ts T

ensi

le T

ests

Dia

gram

s

3

keyw

ords

:st

retc

hing

, lat

eral

con

tract

ion

neck

ing,

regi

on o

f nec

king

fract

ure,

regi

on o

f fra

ctur

e

Stre

ss –

Stra

in D

iagr

ams

Dia

gram

s

4

Page 2: Tensile Tests

Stre

ss –

Stra

in D

iagr

ams

Mild

Ste

elD

iagr

ams

5

Stre

ss –

Stra

in D

iagr

ams

Load

ing

& U

nloa

ding

Dia

gram

s

6

Exam

ple

Ger

e 1.

4-4

#1

A c

ircul

ar b

ar o

f mag

nesi

um a

lloy

is 7

50 m

m lo

n g. T

he s

tress

Dia

gram

s

gst

rain

dia

gram

is s

how

n. T

he b

ar

is lo

aded

in te

nsio

n to

an

elon

gatio

n of

4.5

mm

, and

then

th

e lo

ad is

rem

oved

.a)

Wha

t is

the

perm

anen

t set

of

the

bar?

b)If

thb

il

dd

hti

7

b) I

f the

bar

is re

load

ed, w

hat i

s th

e pr

opor

tiona

l lim

it?

Exam

ple

Ger

e 1.

4-4

#2

69

8810

Pa

4410

Pa

000

2pr

E

Dia

gram

s

3 3

6 9

3

0.00

2

4.5

10 m

0.00

675

010

m16

010

Pa

0.00

644

10 P

a2.

3636

10 m

pr

A

AB

A

B

L

E

8

31.

7727

10 m

1.77

mm

Ans

()

160

MP

aA

ns

pB

pr

B

new

A

p

L

Page 3: Tensile Tests

Stre

ss –

Stra

in D

iagr

ams

Com

mon

App

rox.

Dia

gram

s

Ela

stic

-Per

fect

ly P

last

ic

Ela

stic

-Stra

in H

arde

ning

9

Stre

ss A

rea

Elem

ent

0lim zA

F A F

zz

ˆˆ

xy

z

xy

z

FF

FF

Fi

Fj

Fk

Gen

Sta

te

0 0

lim limz zA A

F A F A

xx

yyz

z

zz

xy

zj

10

: p

lane

, d

irect

ion

: p

lane

, d

irect

ion

: p

lane

, d

irect

ion

z zz x y

z

z x yz z

Stre

ss V

olum

e El

emen

tG

en S

tate

00

0,

, lim

limlim

AA

A

FF

FA

AA

x

yx

zx

yzx

11

00

0

00

0

00

0

, ,

limlim

lim

, ,

limlim

lim

xx

x

yy

y

zz

z

AA

A

AA

A

AA

A

AA

AF

FF

AA

A

FF

FA

AA

x

yx

zx

yz

y yx

zx

yz

xx

yy

yy

zz

zz

z

Stat

e of

Str

ess

Def

initi

on

9

stre

ss c

ompo

nent

sσ x

, σy,

σ z, τ

xy, τ

xz ,

τ yx , τ

yz ,

τ zx,

τ zy

Gen

Sta

te Fr

om c

ompl

emen

tary

prin

cipl

e of

she

arτ x

y=

τ yx

, τxz

=τ z

x, τ y

z=

τ zy

6

inde

pend

ent c

ompo

nent

sσ x

, σy,

σ z, τ

xy, τ

yz ,

τ zx

12

To

def

ine

a ge

nera

l sta

te o

f stre

ss

Mag

nitu

de o

f stre

ss c

ompo

nent

s

Dire

ctio

n of

stre

ss c

ompo

nent

s (+

ve,−

ve)

O

rient

atio

n of

the

volu

me

elem

ent (

x, y

, zax

es)

Page 4: Tensile Tests

Stre

ss C

ompl

emen

tary

Prin

cipl

e of

She

ar

C

onsi

der a

vol

ume

elem

ent s

ubje

ct to

pur

e sh

ear

A

ll fo

ur s

hear

stre

sses

mus

t hav

e eq

ual m

agni

tude

and

be

dire

cted

eith

er to

war

d or

aw

ay fr

om e

ach

othe

r at o

ppos

ite

dft

hl

t

Gen

Sta

te

edge

s of

the

elem

ent.

1

2

13

Stat

e of

Str

ess

Nor

mal

Str

ess

Sign

Con

vent

ion

Gen

Sta

te

14

Stre

ss E

lem

ents

2DG

en S

tate

MP

a

MP

a

MP

a

x y xy

15

Stre

ss E

lem

ents

3DG

en S

tate

MP

ax

MP

a

MP

a

MP

a

y y xy

16

MP

a

MP

a

yz zx

Page 5: Tensile Tests

Stat

e of

Str

ain

Def

initi

on

9

stra

in c

ompo

nent

sε x

, εy,

ε z, γ

xy, γ

xz ,

γ yx , γ

yz ,

γ zx,

γ zy

Gen

Sta

te Fr

om c

ompl

emen

tary

prin

cipl

e of

she

arγ x

y=

γ yx

, γxz

=γ z

x, γ y

z=

γ zy

6

inde

pend

ent c

ompo

nent

sε x

, εy,

ε z, γ

xy, γ

yz ,

γ zx

17

To

def

ine

a ge

nera

l sta

te o

f stra

in

Mag

nitu

de o

f stre

ss c

ompo

nent

s

Dire

ctio

n of

stre

ss c

ompo

nent

s (+

ve,−

ve)

O

rient

atio

n of

the

volu

me

elem

ent (

x, y

, zax

es)

Stat

e of

Str

ain

Volu

me

Elem

ent

Gen

Sta

te

,,

xxy

xzu

uv

uw

18

, ,

, ,

xxy

xz

yxy

yz

zxzy

z

xy

xz

xv

uv

vw

xy

yz

yw

uw

vw

xz

yz

z

Stat

e of

Str

ain

Mod

ern

nota

tion

Gen

Sta

te

11

1,

,2

22

xxxy

xzu

uu

vu

wx

xy

xz

x

19

22

2

11

1,

,2

22

11

1,

,2

22

yxyy

yz

zxzy

zz

xx

yx

zx

vu

vv

vw

xy

yy

zy

wu

wv

ww

xz

yz

zz

Pois

son’

s R

atio

Def

initi

onH

ooke

’s

lat

long

20

Page 6: Tensile Tests

Tria

xial

Str

ess

Gen

eral

Hoo

ke’s

Law

#1

Hoo

ke’s

C

onsi

der n

orm

al s

train

in

dire

ctio

n ca

uses

xx

E

21

cau

ses

cau

ses

cau

ses

1(

)

EE E

E

xx

x

yx

y

zx

z

xx

xx

xy

z

Tria

xial

Str

ess

Gen

eral

Hoo

ke’s

Law

#2

1(

)E

xx

yz

Hoo

ke’s

(1

)(

)(1

)(12

)E

xx

yz

1(

)

1(

)

E E

yy

xz

zz

xy

22

(1)(1

2)

(1)

()

(1)(1

2)

(1)

()

(1)(1

2)

E E

yy

xz

zz

xy

Uni

axia

l Str

ess

Stra

in E

nerg

y #2

1(

)2

xx

yy

zz

u

Hoo

ke’s

22

2

2 11

()

()

22

1(

)2 1

()

()

2

yy

xx

yz

yy

xz

zz

xy

xy

zx

yy

zz

x

EE

E E

u u uE

23

22

2

2

(1)(

)2

()

2(1

)(12

)x

yz

xy

yz

zx

EE

E

u

Pure

She

ar G

ener

al H

ooke

’s L

awH

ooke

’s

Con

side

r she

ar s

train

sC

onsi

der s

train

ene

rgy

24

xyxy

yzyz

zxzx

G G G

1(

)2

xyxy

yzyz

zxzx

u

2(

1)

EG

Page 7: Tensile Tests

Hoo

ke’s

Law

2D S

peci

al C

ases

#1

P

lane

stre

ss: σ

z=

τ yz

= τ z

x=

0

11

()

xx

yz

xx

yE

E

Hoo

ke’s

11

()

1(

)

xx

yz

xx

y

yy

zx

yy

x

zz

xy

zx

y

xyxy

xyxy

EE

EE

EE

GG

25

0 0

xyxy

yzyz

yz

zxzx

zx

GG

G G

Hoo

ke’s

Law

2D S

peci

al C

ases

#2

P

lane

stra

in: ε

z=

γ yz

= γ z

x=

0

11

()

()

xx

yz

xx

yz

EE

Hoo

ke’s

11

()

()

1(

)0

()

xx

yz

xx

yz

yy

zx

yy

zx

zz

xy

zx

y

xyxy

xyxy

EE

EE

E GG

26

00

00

xyxy

yzyz

yz

zxzx

zx

GG

G G

Ther

mal

Effe

cts

G

ener

ally

, a b

ody

expa

nds

or tr

ies

to e

xpan

d w

hen

tem

pera

ture

rise

s.

Hoo

ke’s

If th

e bo

dy c

an e

xpan

d, th

ere

will

be th

erm

al s

train

s ε T

=α(

ΔT) i

n th

e no

rmal

dire

ctio

ns.

If

the

body

can

not e

xpan

d fre

ely,

ther

e w

ill be

ther

mal

st

ress

es.

1

27

, , ,

1(

)

1(

)

1(

)

xM

xT

xy

z

yM

xT

yz

x

zM

xT

zx

y

TE

TE

TE

α=

coef

ficie

nt

of li

near

ther

mal

ex

pans

ion

Hoo

ke’s

Law

With

and

With

out T

emp

Effe

cts

11

()

()

xx

yz

xx

yz

TE

E

Hoo

ke’s

11

()

()

11

()

()

xx

yz

xx

yz

yy

zx

yy

zx

zz

xy

zz

xy

xyxy

xyxy

EE

TE

E

TE

E

GG

28

xyxy

yzyz

yzyz

zxzx

zxzx

GG

GG

GG

Page 8: Tensile Tests

Obj

ectiv

es #2

D

escr

ibe

basi

c fe

atur

es o

f ela

stic

ity in

Car

tesi

an c

oord

inat

es

Giv

en a

sta

te o

f stre

ss o

r sta

in, d

eter

min

e th

e eq

uiva

lent

st

ate

atot

hero

rient

atio

nsst

ate

at o

ther

orie

ntat

ions

D

eter

min

e th

e pr

inci

pal a

nd m

axim

um s

hear

st

ress

es/s

train

s in

2D

by

Moh

r’s c

ircle

D

eter

min

e th

e pr

inci

pal a

nd m

axim

um s

hear

st

ress

es/s

train

s in

3D

by

linea

r alg

ebra

C

alcu

late

Tre

sca

and

von

Mis

esst

ress

es

Rev

iew

ofst

ress

and

defo

rmat

ion

inax

ially

load

ed

29

R

evie

w o

f stre

ss a

nd d

efor

mat

ion

in a

xial

ly lo

aded

m

embe

rs, t

hick

-wal

led

tors

ion

and

beam

ben

ding

Stat

e of

Str

ess

Sign

Con

vent

ion

& O

rient

atio

nTr

ansf

orm

=

30

posi

tive

dire

ctio

npo

sitiv

e an

gle

of ro

tatio

n θ

(cou

nter

cloc

kwis

e)

Incl

ined

Pla

neTr

ansf

orm

31

Incl

ined

Pla

neSt

ress

es o

n In

clin

ed P

lane

#1

Tran

sfor

m

0

(co

s)c

os(

cos

)sin

xx

xxy

FA

AA

32

22

(si

n)s

in(

sin

)cos

0

cos

sin

2si

nco

s

0

(co

s)s

in(

cos

)cos

(si

n)c

os(

sin

)sin

0

yxy

xx

yxy

yx

yx

xy

yxy

xy

AA

FA

AA

AA

22

()s

inco

s (

cos

sin

)y

xxy

Page 9: Tensile Tests

Incl

ined

Pla

ne S

tres

ses

on In

clin

ed P

lane

#3

Tran

sfor

m

33

22

0

(si

n)s

in(

sin

)cos

(co

s)c

os(

cos

)sin

0

sin

cos

2si

nco

s

yy

xxy

yxy

yx

yxy

FA

AA

AA

Stre

ss T

rans

form

atio

n Eq

uatio

nsTr

ansf

orm

cos2

sin

22

2

sin

2co

s22

xy

xy

xxy

xy

xy

xy

34

2

cos2

sin

22

2x

yx

yy

xy

xy

xy

Exam

ple

Hib

bele

r 9-4

/5 #

1

The

stat

e of

stre

ss a

t a p

oint

in a

mem

ber i

s sh

own

on th

e el

emen

t. D

eter

min

e th

e st

ress

com

pone

nts

actin

g on

the

Tran

sfor

m

incl

ined

pla

ne A

B.

35

Exam

ple

Hib

bele

r 9-4

/5 #

2

Sta

te o

f stre

ss (

axe

s)3

ksi,

2 ks

i, 4

ksi

xy

xy

xy

Tran

sfor

m

,,

The

rota

tion

of

to

is

60

cos2

sin2

22

32

32

cos (

260

)(

4)si

n(2

60)

2.71

41 k

si2

2

xy

xy

xy

xy

xxy

x

xyx

y

36

()

()

()

22 sin2

cos2

2x

yx

yxy

x

32

sin(

260

)(

4)co

s(2

60)

4.16

51 k

si2

xy

Page 10: Tensile Tests

Exam

ple

Hib

bele

r 9-4

/5 #

3Tr

ansf

orm

37

2.71

ksi

4.17

ksi

A

nsx xy

100

MP

a,

0x

yxy

Tran

sfor

m Stre

ss T

rans

Uni

axia

l Str

ess

#2

38

Stre

ss T

rans

Uni

axia

l Str

ess

#3

100

MP

a,

0x

yxy

Tran

sfor

m

39

Stre

ss T

rans

Bia

xial

Str

ess

100

MP

a,

50 M

Pa,

0

xy

xy

Tran

sfor

m

40

Page 11: Tensile Tests

Stre

ss T

rans

Pur

e Sh

ear

0,

100

MP

ax

yxy

Tran

sfor

m

41

Stre

ss T

rans

Gen

eral

100

MP

a,

50 M

Pa,

100

MP

ax

y

xy

Tran

sfor

m

xy

42

Gen

eral

Str

ess

Max

imum

Nor

mal

Str

esse

s

'

'm

ax &

min

,

0x

y

Tran

sfor

m

43

Gen

eral

Str

ess

Max

imum

She

ar S

tres

ses

''

''

max

& m

in

, x

yx

y

Tran

sfor

m

44

Page 12: Tensile Tests

Gen

eral

Str

ess

Prin

cipa

l Str

esse

sσ 1

& σ

2#1

Th

eσ 1

is th

e m

axim

um n

orm

al s

tress

and

σ2

is th

e m

inim

um

norm

al s

tress

in th

e pl

ane.

P

rinci

pal p

lane

s ar

e de

fined

by

prin

cipa

l ang

les

θ p1

& θ p

2.

Spec

ial

The

σ 1 o

ccur

s in

θp 1

plan

e an

d σ 2

occ

urs

in θ

p 2pl

ane.

max

& m

in

45

0x

y

Gen

eral

Str

ess

Prin

cipa

l Str

esse

sσ 1

& σ

2#2

cos2

sin

20

22

xy

xy

xxy

dd

dd

Spec

ial

2ta

n2

xyp

xy

12

90p

p

46

12

mut

ually

pe

rpen

dicu

lar

plan

es

pp

Gen

eral

Str

ess

Prin

cipa

l Str

esse

sσ 1

& σ

2#3

2ta

n2

xyp

xy

Spe

cial

22

1

2

cos2

2

xy

xy

xy

p

R

R2

47

1

2

sin

22xy

p

R R

22

1,2

22

xy

xy

xy

Gen

eral

Str

ess

Prin

cipa

l Str

esse

sσ 1

& σ

2#4

Spe

cial

3

plan

e st

ress

0

48

Page 13: Tensile Tests

Gen

eral

Str

ess

Max

In-P

lane

She

ar S

tres

s τ m

ax #

1

''

''

max

& m

in

, x

yx

y

Spec

ial

49

Gen

eral

Str

ess

Max

In-P

lane

She

ar S

tres

s τ m

ax #

2

Max

imum

in-p

lane

she

ar s

tress

es τ

max

and

τ min

Th

e τ m

axis

the

max

imum

+ve

she

ar s

tress

and

τm

inis

the

max

imum

−ve

she

ar s

tress

.

Spec

ial

Pla

nes

of τ

max

and

τ min

are

defin

ed b

y an

gles

θs 1

and

θ s2.

max

& m

in

50

xy

Gen

eral

Str

ess

Max

In-P

lane

She

ar S

tres

s τ m

ax #

3

sin2

cos2

02

xy

xy

xy

dd

dd

Spe

cial

tan

22x

ys

xy

51

11

22

45 45s

p

sp

Gen

eral

Str

ess

Max

In-P

lane

She

ar S

tres

s τ m

ax #

4

22

12

,2

2x

ym

axm

inxy

xy

Spe

cial

22

2 2

xy

avg

xy

52

Page 14: Tensile Tests

Gen

eral

Str

ess

Max

In-P

lane

She

ar S

tres

s τ m

ax #

5

M

axim

um in

-pla

ne s

hear

stre

sses

are

foun

d by

rota

ting

x 1y 1

z 1ax

es a

bout

z1

axis

thro

ugh

45.

Th

e ro

tatio

ns o

f 45

abou

t set

s of

two

prin

cipa

l axe

s gi

ves

lith

it

fl

ht

Spec

ial

plan

es w

ith m

axim

um o

ut-o

f-pla

ne s

hear

stre

sses

.

11

1

21

12

()

, (

),

()

22

2m

axx

max

ym

axz

53

Exam

ple

Hib

bele

r 9-4

/5 #

4

Det

erm

ine

the

prin

cipa

l stre

sses

, the

max

imum

in-p

lane

she

ar

stre

ss a

nd a

vera

ge n

orm

al s

tress

as

wel

l as

thei

r cor

resp

ondi

ng

orie

ntat

ions

.

Spec

ial

oe

tato

s

54

Exam

ple

Hib

bele

r 9-4

/5 #

5S

peci

al

Sta

te o

f stre

ss0

(ax

es)

xy

55

0 (

axe

s)3

ksi

2 ks

i4

ksi

x y xy

xy

Exam

ple

Hib

bele

r 9-4

/5 #

6Pr

inci

pal S

tress

esS

peci

al

1

22(

4)ta

n21.

63

22

57.9

95, 5

7.99

518

028

.997

, 61

.003

At

28.9

97xyp

xy

pp

x

56

1

11

1

1 1

cos2

sin2

22

32

32

cos(

228

.997

)(

4)si

n(2

28.9

97)

22

5.21

70 k

si

xy

xy

xx

x

x

yx

x

Page 15: Tensile Tests

Exam

ple

Hib

bele

r 9-4

/5 #

7

2A

t 61

.003

cos2

sin

24

2170

ksi

x

xy

xy

Prin

cipa

l Stre

sses

Spec

ial

22

2

21

21

21

1

12

1

cos2

sin

24.

2170

ksi

22

, ,

,

4.22

ksi

, 61

.0

522

ksi

290

Ans

xx

xyx

xp

xx

px

p

57

22

5.22

ksi

,29

.0

Ans

p

Exam

ple

Hib

bele

r 9-4

/5 #

9M

ax S

hear

Stre

sses

32

tan

20.

625

22(

4)x

ys

xy

Spec

ial

3

33

33

232

.225

, 32

.225

180

16.0

03,

73.9

97

At

73.9

97 si

n2

cos2

4.71

70 k

si2

xy

ss

x

xy

xy

xxy

x

58

4

44

44

At

16.0

03 sin

2co

s24.

7170

ksi

2

x

xy

xy

xxy

x

Max

She

ar S

tress

esEx

ampl

e H

ibbe

ler 9

-4/5

#10

12

33

44

At

&

, 2

0.5

ksi

ss

xy

xy

avg

avg

Spe

cial

31

34

24

1 2

, ,

,

4.72

ksi

,74

.0

4.72

ksi

,16

.0

0.5

ksi

in b

oth

plan

esA

ns

max

xs

xm

inx

sx

max

s

min

s

avg

59

pav

g

Moh

r’s C

ircle

Gra

phic

al M

etho

d

From

stre

ss tr

ansf

orm

atio

n eq

uatio

ns

Tran

sfor

m

22

22

cos2

sin

2...

(1)

22

sin

2co

s2...

(2)

2

xy

xy

xxy

xy

xy

xy

60

22

22

(1)

(2)

cons

t2

2x

yx

yx

xy

xy

Page 16: Tensile Tests

Moh

r’s C

ircle

Con

stru

ctio

n

22

2(

)x

avg

xy

R

Tran

sfor

m

22

2 2

xy

avg

xy

xyR

61

Moh

r’s C

ircle

Prin

cipa

l & S

hear

Str

esse

s

min

1

Spec

ial

2

62 m

ax

Exam

ple

Hib

bele

r 9-4

/5 #

12

The

stat

e of

stre

ss a

t a p

oint

in a

mem

ber i

s sh

own

on th

e el

emen

t. U

sing

the

Moh

r’s c

ircle

, det

erm

ine

the

stre

ss c

ompo

nent

s ac

ting

on th

e in

clin

ed p

lane

AB

. The

n, fi

nd th

e pr

inci

pal s

tress

es,

Tran

sfor

m

act

go

te

ced

pa

ee

,d

te

pc

past

esse

s,th

e m

axim

um in

-pla

ne s

hear

stre

ss a

nd a

vera

ge n

orm

al s

tress

as

wel

l as

thei

r cor

resp

ondi

ng o

rient

atio

ns.

St

tf

tt

0(

)

63

Sta

te o

f stre

ss a

t 0

( a

xes)

3 ks

i, 2

ksi,

4 ks

i

The

rota

tion

of

to

is

60

xy

xyxy

xyx

y

Exam

ple

Hib

bele

r 9-4

/5 #

13

0

.5 k

si2

(0)

(0

50)

xy

avg

CC

Tran

sfor

m

(,0

)(

0.5,

0)

(,

)(

3,

4)

avg

xxy

CC

AA

64

22

(3

0.5)

(4)

4.71

70 k

si4

tan

, 57

.995

2.5

R R

Page 17: Tensile Tests

Exam

ple

Hib

bele

r 9-4

/5 #

14

60

Rot

ate

260

CC

Wto

G

Tran

sfor

m

Rot

ate

260

CC

W to

2

6057

.99

62.0

1

Coo

rdin

ate

of

(

2.71

, 4.

17)

G

GG

65

Exam

ple

Hib

bele

r 9-4

/5 #

15Tr

ansf

orm

66

2.71

ksi

4.17

ksi

Ans

x xy

Exam

ple

Hib

bele

r 9-4

/5 #

16Pr

inci

pal S

tress

esM

ax S

hear

Stre

sses

14.

22 k

si

Spe

cial 1 22

61.0

CW

5.22

ksi

29.0

CC

W

4.72

ksi

740

p p max

67

1 2

74.0 4.

72 k

si16

.0 0.5

ksi

Ans

s min

s avg

Ex

ampl

e H

ibbe

ler 9

-4/5

#17

Spe

cial

68

Prin

cipa

l Stre

sses

Max

She

ar S

tress

es

Page 18: Tensile Tests

Plan

e St

rain

P

lane

stra

in in

the

xypl

ane

0z

zxzy

69

D

oes

plan

e st

ress

occ

urs

in a

pla

ne s

train

bod

y?

Plan

e St

rain

Sig

n C

onve

ntio

n an

d O

rient

atio

n

70

posi

tive

dire

ctio

npo

sitiv

e an

gle

of ro

tatio

n θ

(cou

nter

cloc

kwis

e)

Stra

in T

rans

form

atio

n N

orm

al S

trai

n #1

71

Stra

in T

rans

form

atio

n N

orm

al S

trai

n #2

cos

sin

cos

cos

sin

cos

xy

xy

xx

yxy

ddx

dydy

ddx

dydy

1 1

22

cos

sin

cos

As

cos

, si

n,

cos

sin

sin

cos

xx

yxy

xx

yxy

dsds

dsds

dxdy

dsds

72

1

22

Rem

embe

r co

ssi

n 2

sin

cos

?x

xy

xy

Page 19: Tensile Tests

Stra

in T

rans

form

atio

n Sh

ear S

trai

n #1

73

Stra

in T

rans

form

atio

n Sh

ear S

trai

n #2

11

12

3

xy

γ

2

sin

cos

sin

()s

inco

ssi

n

xy

xy xy

xy

dxdy

dsds

dy ds

2(

)i

(90

)(

90)

(90

)

74

11

2

2

22

()s

in(

90)c

os(

90)

cos

(90

)

()s

inco

sco

s

2()s

inco

s(c

ossi

n)

xy

xy

xy

xy

xy

xy

xy

11

22

()s

inco

s (

cos

sin

)x

yy

xxy

Stra

in T

rans

form

atio

n Eq

uatio

ns

co

s2si

n22

22xy

xy

xy

x

sin2

cos2

2

cos2

sin2

2

22

22

xy

xx

y

xy

xy

y xy

x

y

xy

y

75

Prin

cipa

l Str

ains

ε 1

is th

e m

axim

um n

orm

al s

train

and

ε2

is th

e m

inim

um n

orm

al

stra

in in

the

plan

e.

22

tan2

22

x

x

yp

y

Th

e pr

inci

pal s

tress

es a

nd p

rinci

pal s

train

s oc

cur i

n th

e i

tti

1,2

22

2x

yx

yxy

P

rinci

pal p

lane

s ar

e θ p

1an

d θ p

2,

76

sam

e or

ient

atio

n.

In p

rinci

pal p

lane

s γ x

’y’=

0.

For p

lane

stra

in, t

hird

prin

cipa

l stra

in ε

3 =

0.

Page 20: Tensile Tests

Max

imum

In-p

lane

She

ar S

trai

ns

γ max

is th

e m

axim

um p

ositi

ve s

hear

stra

in a

nd γ m

inis

the

max

imum

neg

ativ

e sh

ear s

train

.

22

In

pla

ne o

f max

imum

she

ar s

train

s,

O

ccur

in p

lane

s θ s

1an

d θ s

2,

12

,

22

22

xy

xym

axm

in

tan

2x

ys

xy

77

2x

yx

yav

g

Moh

r’s C

ircle

Pla

ne S

trai

n

22

2(

)2x

yx

avg

R

2

22

2 22

xy

avg

xy

xyR

78

Moh

r’s C

ircle

Str

ain

Tran

sfor

mat

ion

/2

min

1

2

79

/2m

ax

Stra

in R

oset

te

S

train

gau

ges

can

only

mea

sure

nor

mal

stra

ins.

C

lust

ers

of s

train

gau

ges,

stra

in ro

sette

s, a

re u

sed

to

mea

sure

stat

esof

plan

est

rain

mea

sure

sta

tes

of p

lane

stra

in.

80

22

22

22

cos

sin

sin

cos

cos

sin

sin

cos

cos

sin

sin

cos

ax

ay

axy

aa

bx

by

bxy

bb

cx

cy

cxy

cc

Page 21: Tensile Tests

Stra

in R

oset

te R

ecta

ngul

ar R

oset

te

0,

45,

90a

ba

, ,

2(

)x

ay

c

xyb

ac

81

W

hat i

s th

e re

stric

tion

in s

peci

fyin

g an

gles

in s

train

rose

tte?

No

two

gaug

es a

re a

rran

ged

180°

to e

ach

othe

r

Exam

ple

Hib

bele

r 10-

8 #1

The

stat

e of

stra

in a

t the

poi

nt o

n th

e sp

anne

r wre

nch

has

com

pone

nts

of ε

x =

260(

10–6

), ε y

= 3

20(1

0–6 )

, and

γ xy

= 18

0(10

6 ) .

Use

the

stra

in-tr

ansf

orm

atio

n eq

uatio

ns to

det

erm

ine

(a)

)U

set

est

ata

so

ato

equa

tos

tode

tee

(a)

the

in-p

lane

prin

cipa

l stra

ins

and

(b) t

he m

axim

um in

-pla

ne

shea

r stra

in a

nd a

vera

ge n

orm

al s

train

. In

each

cas

e, s

peci

fy

the

orie

ntat

ion

of th

e el

emen

t and

sho

w h

ow th

e st

rain

s de

form

the

elem

ent w

ithin

the

x-y

plan

e.

Sta

te o

f stra

in

82

6 6 6

0 (

axe

s)26

010

320

10

180

10

x y xy

xy

Exam

ple

Hib

bele

r 10-

8 #2

Prin

cipa

l Stra

in

635

.783

180

10ta

n2

xy

1

11

1

6

6

tan

2

54

.218

(260

320)

10

At

35.7

83

cos2

sin

219

5.13

102

22

pp

xy

x

xy

xy

xyx

xx

83

2

22

2

6

At

54.2

18

cos2

sin

238

4.87

102

22

x

xy

xy

xyx

xx

Exam

ple

Hib

bele

r 10-

8 #3

Prin

cipa

l Stra

in

12

21

1

61

,

385

1054

.2

px

px

p

84

2

62

195

1035

.8A

nsp

Page 22: Tensile Tests

Exam

ple

Hib

bele

r 10-

8 #4

Max

She

ar S

train

1

145

54.2

1845

9.21

8

4554

218

4599

218

sp

21

12

6

4554

.218

4599

.218

: 2

238

4.87

195.

1310

22

max

,min

sp

max

,min

85

6

6

189.

7410

290

102

max

,min

xy

avg

Exam

ple

Hib

bele

r 10-

8 #5

Max

She

ar S

train

19.

22s

1 2

6

6

190

10

99.2 19

010

s max

s min

86

6

On

both

pla

ne29

010

Ans

avg

Exam

ple

Hib

bele

r 10-

8 #6

Moh

r’s C

ircle

At

(/2

)A

6 6 6

At

(,

/2)

0 (

axe

s)26

010

320

10

180

10

xxy

x y xy

A

xy

87

6

At

(,0

)(

)/2

290

10

avg

avg

xy

C

6

61

6

94.8

6810 90

10ta

n71

.565

(290

260)

10

R

Exam

ple

Hib

bele

r 10-

8 #7

Moh

r’s C

ircle

1

61

385

1054

.2p

88

2

62

195

1035

.8A

nsp

Page 23: Tensile Tests

Exam

ple

Hib

bele

r 10-

8 #8

Moh

r’s C

ircle

1 2

6

6

9.22 19

010

99.2 19

010

s max

s

89

6

6

190

10

On

both

pla

ne29

010

Ans

min

avg

Stre

ss &

Str

ain

Tens

or 3D

Tens

or

xxy

xzxx

xyxz

/2/2

/2/2

yxy

yzyx

yyyz

zxzy

zzx

zyzz

xxxy

xzxx

xyxz

90

/2/2

/2/2

yxyy

yzyx

yyyz

zxzy

zzzx

zyzz

Stre

ss T

rans

form

atio

n 2D

#1

Tens

or

ˆ

ˆˆ

ˆx

yx

yF

Fi

Fj

Fi

Fj

cos

sin

cos(

)co

sco

ssi

nsi

nsi

n()

sin

cos

cos

sin

cos

sin

cos

sin

x y x yFF

FF

FF

FF

FF

FF

FF

F

F

91

cos

sin

cos

sin

cos

sin

sin

cos

xx

y

yy

x

FF

FF

FF

x yF F

F

aF

Stre

ss T

rans

form

atio

n 2D

#2

Tens

or

T

aa

22

22

cos

sin

cos

sin

sin

cos

sin

cos

cos

cos

2si

nco

s

2i

xx

xy

xxxy

yx

yy

yxyy

xx

yy

xy

92

22

cos

cos

2si

nco

s

sin

cos

sin

cos

2y

xx

yxy

xy

xy

xyxy

2

cos

Page 24: Tensile Tests

Stre

ss T

rans

form

atio

n 2D

#3

22

cos

cos

2si

nco

s

1co

s21

cos2

2si

nco

s2

2

xx

yy

xy

xy

yxy

Tens

or

2

22

cos2

cos2

2si

nco

s2

22

2

sin

c

cos2

sin

22

2os

sin

cos

2cos

yx

xy

yxy

xy

xy

xyxy

xy

xy

xxy

93

()s

inx

y

2

cos

(2c

sin

2co

os1)

s22

xy

xy

xy

xy

2 2

sin

22

sin

cos

sin

(1co

s2)/

2co

s(1

cos2

)/2

xy

xy

Stre

ss T

rans

form

atio

n 3D

#1

Tens

or

Ta

a

94

cos

cos

cos

cos

cos

cos

cos

cos

cos

T

xx

xy

xz

yx

yy

yz

zx

zy

zz

aa

a

Stre

ss T

rans

form

atio

n 3D

#2

Tran

sfor

mat

ion

mat

rix

cos

cos

cos

xx

xy

xz

Tens

or

cos

cos

cos

cos

cos

cos

cos

cos

cos9

0co

sco

sco

s90

cos9

0co

s90

cos0

xx

xy

xz

yx

yy

yz

zx

zy

zz

xx

xy

yx

yy

aa

95

cos

sin

0si

nco

s0

00

1a

Stre

ss T

rans

form

atio

n 3D

Prin

cipa

l Str

ess

#1Te

nsor Th

e pr

inci

pal v

alue

s an

d di

rect

ions

of t

he s

tress

and

stra

in

tens

ors

can

be o

btai

ned

in th

e sa

me

met

hod

of c

alcu

latin

g ei

genv

alue

san

d ei

genv

ecto

rsof

a m

atrix

and

equ

ival

ent t

o e

gea

ues

ad

ege

ecto

so

aat

ad

equ

ae

tto

mat

rix d

iago

naliz

atio

n.

ˆˆ

From

ˆR

earra

ngin

g(

)0

Non

-triv

ial s

olut

ion

if de

t()

0

Tn

n

TI

n

TI

96

1 2 3

Equ

atio

ns fo

r 3 e

igen

valu

es

det(

)0

de

t()

0

de

t()

0

TI

TI

TI

Page 25: Tensile Tests

Stre

ss T

rans

form

atio

n 3D

Prin

cipa

l Str

ess

#2Te

nsor

For e

ach

eige

nval

ue

, ˆˆ

Det

erm

ine

eige

nvec

tor

from

()

0i

ii

in

TI

n

12

3

11

1

22

2

33

3

g(

ˆˆ

Then

, ass

embl

e tra

nsfo

rmat

ion

mat

rix fr

om

, a

nd

as u

nit n

orm

al d

irect

ions

ii

i

xy

z

px

yz

xy

z

nn

n

nn

na

nn

nn

nn

97

y

1

2

3

Form

nor

mal

tran

sfor

mat

ion

00

00

00

T

pp

pa

a

Stre

ss T

rans

form

atio

n 3D

Prin

cipa

l Str

ess

#3

0Fr

om0

00

xxy

xyy

z

Tens

or

20

Eig

enva

lues

00

00

Yiel

ds[(

)()

]()

0

z

xxy

xyy

z

xy

xyz

98

2

3

Or

()(

)0

(1)

and

0 (2

)

For (

2)

yy

xy

xy

z

z

Stre

ss T

rans

form

atio

n 3D

Prin

cipa

l Str

ess

#4

22

22

For (

1)(

)0

()

()

4()

xy

xy

xy

Tens

or

1,2

22

2

1,2

22

2

1,2

()

()

4()

2 24

4(

)2

2(

)2

42

4

xy

xy

xy

xy

xx

yy

xy

xyx

y

xy

xx

yy

xy

99

2

21,

21,

2

24

()

()

22

xy

xy

xy

Prin

cipa

l Stre

sses

=Ei

genv

alue

s

Stre

ss T

rans

form

atio

n 3D

Prin

cipa

l Str

ess

#5

0E

igen

vect

ors

00

xxy

x

xyy

yn n

Tens

or

33

33

3

33

33

3

00

0Fo

r ,

00

00

Yiel

ds(

)0

(3.1

)

xyy

y

zz

xxy

x

zxy

yy

zz

xx

xyy

n

n n nn

n

100

33

3

33

()

0(3

.2)

()

0(3

.3)

Sol

ve (3

.1)-(

3.3)

axyx

yy

zz

nn

n

22

23

33

3

12

3

nd

1

0,

0,

1 x

yz

zz

z

nn

nn

nn

n

Page 26: Tensile Tests

Stre

ss T

rans

form

atio

n 3D

Prin

cipa

l Str

ess

#6

2

21

()

()

For

22

xy

xy

x y

Tens

or

11

11

11

11

1

11

1

22

0E

iven

vect

ors

00

00

Yiel

ds(

)0

(1.1

)(

)0

(1.2

)

y

xxy

x

xyy

y

zz

xx

xyy

xyx

yy

n n nn

n

nn

101

11

1

11

11

()

0(1

.2)

()

0(1

.3)

Solv

e (1

.1)-(

1.3)

and

1

to fi

nd

,

xyx

yy

zz

x

nn

n nn

11

2

,

Sim

inar

pro

cedu

re fo

r

yz

nn

Exam

ple

Hib

bele

r 9-4

/5 #

1

The

stat

e of

stre

ss a

t a p

oint

in a

mem

ber i

s sh

own

on th

e el

emen

t. D

eter

min

e th

e st

ress

com

pone

nts

actin

g on

the

Tens

or incl

ined

pla

ne A

B. T

hen,

det

erm

ine

the

prin

cipa

l stre

sses

and

th

e co

rresp

ondi

ng o

rient

atio

ns.

102

Exam

ple

Hib

bele

r 9-4

/5 #

2Te

nsor

34

04

20

ksi

00

0

xxy

zx

xyy

yz

zxyz

z

103

1/2

3/2

0co

ssi

n0

sin

cos

03

/21/

20

00

10

01

a

Exam

ple

Hib

bele

r 9-4

/5 #

3

T

xx

yx

z

aa

Tens

or

1/2

3/2

01/

23

/20

34

03

/21/

20

42

03

/21/

20

00

10

00

00

1

yx

yy

z

zx

zy

z

104

2.71

414.

1651

04.

1651

1.71

410

ksi

00

0A

t 60

,

2.71

ksi

, 1.

71 k

si,

4.17

ksi

,

0A

nsx

yx

y

zy

zx

z

Page 27: Tensile Tests

Exam

ple

Hib

bele

r 9-4

/5 #

4

34

04

20

ksi

00

0

xxy

zx

xyy

yz

zxyz

z

Tens

or

00

0 34

04

20

00

00

()

(3

)(2

)16

0

189

189

zxyz

z

xxy

zx

xyy

yz

zxyz

z

105

12

3

189

189

0,,

22

189

4.21

699

ksi,

0,

21

895.

2169

9 ks

i2

Ans

Exam

ple

Hib

bele

r 9-4

/5 #

5

1tra

nsfo

rm20

0

00

x

xyzx

xyy

yz

Tens

or

3

trans

form

00

34

04.

2169

90

04

20

ksi

0

00

ksi

00

00

05.

2169

9

zxyz

z

106

0 0 0

xxy

zxx

xyy

yzy

zxyz

zzn n n

Exam

ple

Hib

bele

r 9-4

/5 #

6

11

89Fo

r 4.

2169

9 ks

i2

34

00

Tens

or

11

11

11

11

34

00

42

00

00

00

589

()

40

22

Sol

vesi

mul

tane

ousl

yw

ith5

89

x y z

xy

n n n

nn

107

22

21

11

11

1

1

Sol

ve s

imul

tane

ousl

y w

ith5

894

()

01

22

189

()

02

2 0.

xy

xy

z

z

xnn

nn

n

n

n

1

148

477,

0.

8746

4,

0y

zn

n

Exam

ple

Hib

bele

r 9-4

/5 #

7

2Fo

r 0

34

00

n

Tens

or

22

22

22

22

22

22

22

22

34

00

42

00

00

00

34

0S

olve

sim

ulta

neou

sly

with

42

01

00

x y z

xy

xy

xy

z

n n n

nn

nn

nn

nn

108

2

22

2

00 0,

0,

1z

xy

z

n nn

n

Page 28: Tensile Tests

Exam

ple

Hib

bele

r 9-4

/5 #

8

31

89Fo

r 5.

2169

9 ks

i2

34

00

Tens

or

33

33

33

33

34

00

42

00

00

00

589

()

40

22

Sol

vesi

mul

tane

ousl

yw

ith5

89

x y z

xy

n n n

nn

109

22

23

33

33

3

3

Sol

ve s

imul

tane

ousl

y w

ith5

894

()

01

22

189

()

02

2 0.xy

xy

z

z

xnn

nn

n

n

n

3

187

464,

0.

4847

7,

0y

zn

n

Exam

ple

Hib

bele

r 9-4

/5 #

9

11

1

22

2

0.48

477

0.87

464

00

01

Ans

xy

z

px

yz

nn

na

nn

n

Tens

or

33

30.

8746

40.

4847

70

0.48

477

0.87

464

03

40

0.48

477

00

00

14

20

0.87

464

0.48

477

00

00

xy

z

T

pp

p

p

nn

n

aa

.874

640.

8746

40

0.48

477

01

0

110

4.21

699

00

00

0 k

si0

05.

2169

9p

3D S

tate

of S

tres

s3

Moh

r C

ircle

s

111

3D S

tate

of S

tres

s Tr

iaxi

al S

tres

s

If

ther

e is

no

shea

r stre

ss, σ

x', σ

y', σ

z'ar

e pr

inci

pal s

tress

es.

3 M

ohr

Circ

les

12

3

max

int

min

112

Page 29: Tensile Tests

Tria

xial

Str

ess

Max

imum

She

ar S

tres

s3

Moh

r C

ircle

s

113

abso

lute

max

imum

shea

r stre

ss

1

3(

)2

abs

max

Yiel

d C

riter

ia &

Yie

ld S

urfa

ces

If th

e bo

dy is

sub

ject

ed to

a u

niax

ial s

tress

, the

yie

ld

stre

ss c

an b

e di

rect

ly o

btai

ned

from

the

stan

dard

test

ing.

Equi

vale

nt S

tress

How

ever

, if t

he b

ody

is s

ubje

cted

to a

mul

tiaxi

al s

tate

of s

tress

, th

e th

eorie

s of

failu

rear

e us

ed to

det

erm

ine

whe

ther

poi

nts

in

the

body

hav

e re

ache

d th

e yi

eld.

A yi

eld

crite

rion

is a

hyp

othe

sis

conc

erni

ng th

e lim

it of

el

astic

ity u

nder

any

com

bina

tion

of s

tress

es. Y

ield

sur

face

is

desc

ribed

thro

ugh

stat

esof

stre

ssTh

est

ates

ofst

ress

insi

de

114

desc

ribed

thro

ugh

stat

es o

f stre

ss. T

he s

tate

s of

stre

ss in

side

th

e yi

eld

surfa

ce a

re e

last

ic w

hile

the

surfa

ce s

igni

fies

the

yiel

d po

ints

.

Tres

ca S

tres

sEq

uiva

lent

Stre

ss

13

T

The

Tres

ca c

riter

ion

(max

imum

she

ar s

tress

theo

ry) a

ssum

es

that

yie

ld o

ccur

s w

hen

the

max

imum

she

ar s

tress

exc

eeds

the

max

imum

shea

rstre

ssin

asi

mpl

ete

nsile

case

max

imum

she

ar s

tress

in a

sim

ple

tens

ile c

ase.

115

Von

Mis

es S

tres

sEq

uiva

lent

Stre

ss

The

von

Mis

es c

riter

ion

(max

imum

dis

torti

on e

nerg

y th

eory

) as

sum

es th

at y

ield

occ

urs

the

dist

ortio

n co

mpo

nent

of t

he to

tal

stra

in e

nerg

y U

sex

ceed

s th

at fr

om th

e si

mpl

e te

nsile

test

.

26

sy

UG

116

22

21

22

33

1(

)(

)(

)2

v