Selection of Materials

Part II, Engineering materials

Application of Materials

Structural strength

Strenth of Materials

Stiffness Reliability Lifetime

Strength of materialsProperties determined at tensile/compression tests

Jäävp ike nem ine

K o gup ike nem in e

L , m m

F m ax

F eH

F eL

N

m m 2

R m

R p0,2

0

AA t

Permanent elongation

Total elongation

Criteria for materials selection plastic materials – yield strength (yield limit) –

Re, Rp (Rec, Rp

c)

brittle materials – strength limit – Rm (Rmc), Rm/

Classification of materials (Re, Rp0,2) low strength < 250 N/mm2

medium strength 250...750 N/mm2

high strength 750...1500 N/mm2

super high strength > 1500 N/mm2

Stress concentration

t

R m

ax

m

m

F F

FF

R

tm 2max

Stiffness

E = tg

K =E

E =

G = tgG =

K = tgK =

G =3/8E

E

N o rm a a l- N ih k e - M a h t-

Stiffness D = Ex K(geometric characteristic of cross-section)

At tension K = S (cross-section area)At bending K = I (moment of inertia) I = bh3/3

Modulus of elasticity

Normal Shear Volume

Modulus of elasticityMaterial E, N/mm2 x 109

DiamondWCSiCAl2O3TiCMo & Mo-alloysCo & Co-alloysNi & Ni-alloysSteelsCast ironsCu & Cu-alloysTi & Ti-alloysZn & Zn-alloysAl & Al-alloysSn & Sn-alloysGraphitePb & Pb-alloysPlasticsRubbersPVC

1000450-650500390380320-360200-250130-230190-210170-190120-15080-13045-9070-8040-5030151-50,01-0,10,003-0,01

T KU, KV – cold brittleness

TDBT – ductile-to-brittle transition

Reliability (1)Toughness – notch impact energy KU or KV, J – fracture toughness KC, N/mm2 m1/2

T T TT K H L T K H L T K H L

1 00

5 0

0

T 5 0

Kiu

lise

pinn

a %

K UK U

TDBTT’DBTTDBT

Duc

tile

fra

ctur

e %

5 5

5 5

1 0

1 0

2

1010

R 0 .25

R 1 .0

5

4 5

Reliability (2)Influence of C, ordinary and alloying elements to KU

normal

cold worked

cold worked

el steel

TDBT

TDBT

TDBT CTDBT C

TDBT

Reliability (3)

% of alloying elements

Duc

tile-

to-b

rittl

e tr

ansi

tion

T50

, C

Reliability (4)

Kõrgtugev

Madaltugev

Temperatuur

Pur

ustu

stöö

A , J

15,4

14,0

12,6

11,2

9,8

8,.4

7,0

5,6

4,2

2,82 3 4 5 6 7 8 Tera nr.

U KU, J

low strength

high strength

T

KU

, KV

Grain no.

Dependence of KU/KV on temperature

Dependence of M toughness of A-grain size

Fine and coarse grain steels

T, C T, C

1 20 0 1 20 0

11 0 0 11 0 0

1 00 0 1 00 0

9 00 9 00

8 00 8 00

7 00 7 00

6 00 6 000 0 ,5 1 ,0 1 ,5

A

A 3

A cm

A + F

A + T

A 1

F + TF

C %

12

A C 1

d A

d P d

a b

1 – killed steel2 – rimmed steel

Influence of microalloying elements

Vanaad ium

Titaan

N io ob ium

1 40

1 20

1 00

8 0

6 0

4 0

0

2 0

0 0,02 0,060,04 0,10 0,120,08

L egee riva te e lem en tid e %

Fer

riid

i ter

a,

m2

Alloying elements, %

Gra

in s

ize

of f

erri

te,

m2

V

Ti

Nb

Plane strain fracture toughness K1c

At tension K1c

a

F

F

b

Coefficient of stress intensity

aK maxmax [MPam1/2]

Relationship between K1c and yield strength

Material K1C, MPa

m1/2

WCTiCSiCAl2O3

SiO2

Steels-low carbon-maraging

(E)6 (680)4 (440)3 (420)3 (320)

0,7 (100)54

110-175

Superplastic steels

Maraging steels

Low-alloyed highly tempered steels

Precipitation hardened stainless steels

Fra

ctur

e to

ughn

ess

K1c

, MP

a

m1/

2

Yield strength, MPa

Life time (1)Fatigue

F

P in geepüür

N 1 10 7N 2 N 3 N

R

a b

Steels N = 107Nonferrous alloys N = 108

Impactors:- surface roughness- stress state- stress concentrations

R (R = min/max)-1 – symmetric loading

Life time (2)

Material Rp0,2, N/mm2

-1,

N/mm2

Plain carbon steel-strain hardened-annealedAlloyed steelAl-alloys-wrought alloys-cast alloysTi-alloysCu-alloys

275475

1700275110900450

24034070010080

500150

Life time (3)

Creep = f(, T, t) low temperature T/Tm < 0.5 high temperature T/Tm > 0.5

Impactors structure alloying (super creep alloys) – TMT

7501000/0.1

Corrosion

Modes of corrosion

Chemical

Electrochemical

Biochemical

in dry gases

in organic liquids

in water containing environments

in melt electrolytes

Types of corrosionTypes of corrosion:

a – uniform

b – nonuniform

c – selective

d – spotted

e – pitting

f – dotted

g – under surface

h – intercrystal

i - stress

Chemical corrosion of metals (1)

2 Mg + O2 = 2 MgO

2 Fe + 3 O2 = Fe2O3

For protection Voxide > Vmetal

Kui Voxide/Vmetal > 1 – Cd, Al, Ti, Zr, Zn, Ni, Cr, Fe

At high Voks / Vmet (1,2…2,0) cracking

High temperature corrosion

T 1000 C – oxide layer electroconductive

Chemical corrosion of metals (2)

Corrosion influencing parameters structure surface treatment materials parameters internal stresses T

gas composition velocity environmental parameters heating parameters

Chemical corrosion of metals (3)

Protection alloying ( ) coatings protective atmosphere (at heat treatment) (H2 + N2

+ H2O; CO + CO2 + N2; etc.)

metalbaseion

.el.allion

metalbaseoxide

el.alloxide rr,FF

Electrochemical corrosion of metals (1)Moisture + H2S, Co2,

So2, NaCl electrolyte

metals galvanic pair

Normal potential E, V

Galvanic series

Normal condition Sea water

-2,37 Mg Mg

-1,66 Al Zn

-1,63 Ti Cd

-1,18 Mn Al

soft steel

-0,76 Zn Pb

-0,74 Cr Sn

Ni

-0,44 Fe brass

-0,40 Cd Cu

-0,25 Ni monel (Ni alloy

-0,14 Sn Cr-steel (13% Cr)

0,13 Pb Ti

+0,34 Cu Cr

+0,80 Ag Ag

+1,20 Pt Au

+1,50 Au Pt

Electrochemical corrosion of metals (2)

Microgalvanic pairs at steels

Atmosphere

Moisture film

Metal

Electrochemical corrosion of metals (3)

Protection (1) Selection of materialsTable: Allowed contacts of metals

GroupI II III IV V

Mg Al Fe Ni TiZn plain

carbon steel

Cr Cu-Ni alloy

Cd Pb Stainless steel

Cu-Zn alloy

Sn Cr-steel CuAg, Au

Protection (2)

Protective coatings- metallic (less active metals (Cu, Ni, Sn, Ag) – up

to coating must be undamage; active (Zn, Co) – protection up to end)

- paints, lubricants other

- cathodic protection- protector protection- anodic protection- corrosion inhibitors (high molecular matters)

Wear

Modes of wear

Mechanical Corrosive-mechanicalAdhesive

-abrasion -oxidizing wear-erosion -fretting corrosive wear-cavitation-fatigue wear

Method for wear protection

hardening, thermo-chemical treatment overwelding surface alloying coating (chemical, thermo-chemical, thermally

sprayed, PVD, CVD, mechanical) selection of pairs (by adhesion)

Wear testing methodsDescription

Sliding friction with or without a lubrication

Abrasive wear

Rolling friction with or without a lubrication

Material groups

Metals

Ceramics

Glass

Composites

Polymers

Cermets

Glass-ceramics

MCM

MCM Metal composite materialsCCM Ceramic composite materialPCM Polymeric composite materialGCCM Glass-ceramic composite materialFRG Fiber-reinforced glass

CCM

PCM

GCCM

FRG

Material group kg/m3

Rm

N/mm2

Rm/

up to

Metals an

d allo

ys

Cast ironsPlain carbon steelsAlloy steelsAl-alloysCu-alloysTi-alloysMg-alloys

7800780078002700890045001750

150…800320…1000460…1650150…500230…700300…1450150…335

1013211883220

Plastics

PVCPEPCFiberglass plastic EP . PC

1350950105012501250

10…2520…4035…8030…9080…170

8

14

Specific strength of materials (1)

Specific strength of materials (2)

Material group kg/m3

Rm

N/mm2

Rm/

up toCera-mics

Al2O3

TiO2

3Al2O3 2SiO2

SiC (-modif.)Si3N4

39804240316032203170

300…40070…170110…190450…800500…1000

10462522

Compo-sites

Al-B (30%)Al-B (50%)Fiberglass plastic EP

ECCarbon-Carbon composite 3-directions

2700

1250

8011030…9080…170

4

14

35 (2000C)5 (3000C)

Wood PineOak

550 II690 II

8997 17

Basic physical and mechanical properties of construction materials (1)

Property Metals Ceramics Polymers

Density, kg/m3 x 10-3

2-6 (average.

8)

2-17 (average.

5)1-2

TS, C

Low. High.

Sn232, W3400

High 4000

Low

Hardness Average High LowWorkability Good Poor GoodTensile strength Rm,

MPa 2500 400 120

Compressive strength Rm

c,

MPa 2500 5000 350

Basic physical and mechanical properties of construction materials (2)

Property Metals Ceramics PolymersModulus of elasticity, E GPa

40 400 150 450 0,001 3,5

Creep resistance at high temperatures

Poor Outstanding -

Thermal expansion

Average High

Low Average

Very high

Thermal conductivity

Average

Average (mostly

lowers then t )

Very high

Electrical properties

Conductors Isolators Isolators

Chemical inertness

Low average

OutstandingGood in general

Thank you for attention

priit.kulu@ttu.ee