metalurgia mecnica - revisão (eng)

8/12/2019 Metalurgia Mecnica - Reviso (Eng)

1/95


2/95

direct stress examples

Engineering StressLoad, P

P

Area

Ao

Lo

L/2

L/2

Load, P

P

Area

Ao

Lo

L/2

L/2

o

o

LLe

AP

=

=

Engineering Strain

Direct Stress - Tension Direct Stress - Compression


3/95

tension test

Loa

d,

P(k

N)

Elongation, L (mm)

Uniform DeformationTotal Elongation

Elastic

Deformation

X

MaximumLoad, Pmax

Load, Pf


4/95

Elongation

0.2% offset

yield stress

Proportional Limit

E

E

(Ultimate)

Engineering Strain, e = L/Lo)

Eng

ineeringStress,=

P/Ao Sy

Su

engineering stress-strain curve N

mm2 MPa


5/95

Hookes law - elastic deformation

Elastic deformation is not permanent; it means that when

the load is removed, the part returns to its original shape

and dimensions.

For most metals, the elastic region is linear. For some

materials, including metals such as cast iron, polymers,

and concrete, the elastic region is non-linear.

If the behavior is linear elastic, or nearly linear-elastic,

Hookes Law may be applied:

where E is the modulus of elasticity (MPa)

Ee=


6/95

modulus of elasticity - stiffness

0.0100.0080.0060.0040.0020.0000

100

200

300

400

500

CONTINUED

Stress(MPa)

Strain

E=Se

=(300 0) Pa(0.015 0.0)

= 2x105MPa


7/95

shear stress and strain

Shear Stress,ShearStrain,

GShearStress

Shear Strain

shear stress, = Shear Load / Areashear strain, = angle of deformation (radians)

shear modulus, G = / (elastic region)


8/95

Poissons ratio,

= exez

= eyez

for most metals,

0.25 < < 0.35in the elastic range

furthermore:

E= 2G(1+)


9/95

plastic deformation

Stress

Strain0.002 0.002 0.002

y

y

y

Elastic Plastic Elastic Plastic

Elastic Plastic

Most Metals - Al, Cu Clad Al-Alloys Low carbon Steel


10/95

elastic and plastic strain

Stress

Strain

Plastic Elasticeeep

P

Total Strain

(e,)

ep

e

pe

eee

Ee

eee

=

=

+=

The 0.2% offset yield stress

is the stress that gives a plastic

(permanent) strain of 0.002.


11/95

elastic recovery

Strain

Stress

Loading

Unloading

Loading

Unloading

Reloading

elastic strain Strain


12/95

Elongation

Area Reduction

EL%=LfLo

Lo

x 100

AR%=AoAfAo

x 100

Lo

Ao

Lf

Af

ductility EL% and AR%


13/95

ductile vs brittle materials

only ductile materials will exhibit necking.

ductile if EL%>8% (approximately)

brittle if EL% < 5% (approximately)

X

XXA

B C

XD Brittle DuctileA & B C & D

Enginee

ringStres

s

Engineering Strain


14/95

toughness and resilience

toughness: a measure of the ability of a material toabsorb energy without fracture.

(J/m3 or N.mm/mm3= MPa)

resilience: a measure of the ability of a material toabsorb energy without plastic or permanent

deformation.(J/m3 or N.mm/mm3= MPa)

note: both are determined as energy/unit volume

t h U


15/95

toughness, Ut

X

+

=

100

%

2

)( EL

deU

uy

e

o

t

f

uy

Eng

ineeringStress,=P/Ao

Engineering Strain, e = L/Lo)


16/95

t i l h i l ti


17/95

typical mechanical properties

metals in annealed (soft) condition

Material Yield Stress(MPa)

Ultimate

Stress (MPa)

Ductility

EL%

Elastic Modulus

(MPa)

Poissons

Ratio

1040 Steel 350 520 30 207000 0.301080 Steel 380 615 25 207000 0.30

2024 Al Alloy 100 200 18 72000 0.33

316 Stainless Steel 210 550 60 195000 0.30

70/30 Brass 75 300 70 110000 0.35

6-4 Ti Alloy 942 1000 14 107000 0.36AZ80 Mg Alloy 285 340 11 45000 0.29

str ct ral origins of plasticit


18/95

structural origins of plasticity

Slip, Climb and Slide of atoms in the crystal structure. Slip and Climb occur at Dislocations and Slide occurs

at Grain Boundaries.



19/95


C04edge4.mov C04disje.mov C04dragb.movC04bubb1.mov

C0445deg.mov


20/95


21/95


22/95


23/95


24/95


25/95


26/95


27/95


28/95


29/95


30/95


31/95


32/95


33/95


34/95


35/95


36/95


37/95


38/95


39/95


40/95


41/95


42/95


43/95


44/95


45/95


46/95


47/95


48/95


49/95


50/95


51/95


52/95


53/95


54/95


55/95


56/95


57/95


58/95


59/95


60/95


61/95


62/95


63/95


64/95


65/95


66/95


67/95


68/95


69/95


70/95


71/95

C04frank.mov


72/95


73/95

Kink:

degrau

na LD

no PE

Jog:

degrau na LD

em outro PE


74/95


75/95


76/95


77/95


78/95


79/95


80/95


81/95


82/95


83/95

C04climb.mov


84/95


85/95


86/95

Resultante da tenso de cisalhamento


87/95

Relao do escorregamento com estrutura cristalina


88/95


89/95

Resultante critica da tenso de cisalhamento


90/95

Escorregamento mltiplo


91/95

Escorregamento mltiplo


92/95

Encruamento e escorregamento


93/95


94/95

Deformao por maclagem


95/95

metalurgia mecnica - revisão (eng)

Documents