grain boundaries
DESCRIPTION
Ni-Base Superalloy Waspalloy. low-angle grain boundary. 50µm. Grain Boundaries. high-angle grain boundary ( Q >15°). Properties of Materials. Mechanical Properties Elastic Plastic Viscoelastic Creep Testing methods. stress s =F/A. strain e = l - l 0 / l 0. The Tensile Test. - PowerPoint PPT PresentationTRANSCRIPT
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Grain BoundariesGrain Boundaries
Ni-Base Superalloy Waspalloy
50µm
high-angle grain boundary (>15°)
low-anglegrain boundary
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Properties of Materials Properties of Materials
• Mechanical Properties
• Elastic• Plastic• Viscoelastic• Creep
• Testing methods
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The Tensile TestThe Tensile Test
F o rc e
sp e c im e n
stress =F/A
strain =l-l0/l0
Al 0
l
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The Tensile TestThe Tensile Test
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Elastic DeformationElastic Deformation
re p u ls iv e
a ttra c tiv e
n e t e n e rg y
e n e rg y /fo rc e
r 0 distance r
r0
F
F
Force=dE/dr
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Elastic constants (isotropic case)Elastic constants (isotropic case)
• Stress – strain / shear stress – shear strain
• Young’s modulus• Shear modulus• Poisson ratio
In order to completely describe the elastic behavior of a solid 2 of these constants need to be known!
1G2E
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Yield Strength Yield Strength YY 0.002 strain offset yield-point phenomenon
(C steels, dislocations are pinned by C)
Y
Y
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The Stress-Strain CurveThe Stress-Strain Curve
stress
strain
necking
engineering stress
true stress
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Materials Selection ChartsMaterials Selection Charts
Strength [MPa]
Density [1000kg/m³]
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Plastic Deformation – Dislocation GlidePlastic Deformation – Dislocation Glide
shear stress
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Plastic Deformation – Dislocation GlidePlastic Deformation – Dislocation Glide
=>macroscopicdeformation
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Plastic Deformation – Dislocation GlidePlastic Deformation – Dislocation Glide
dislocation motion
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Plastic DeformationPlastic Deformation
shear stress
F
F
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Some concluding words on dislocationsSome concluding words on dislocations
• Strengthening mechanisms
• Grain size reduction (Hall-Petch equation)
• Solid solution strengthening• Strain hardening
dk y0y
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Mechanical testing Mechanical testing
• Hardness• Vickers• Rockwell• … Nanoindentation
• Ductility• Toughness• Creep • Fatigue
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Vickers Microhardness TestingVickers Microhardness Testing
length of the diagonals d1 and d2
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Rockwell Hardness Testing (HRC)Rockwell Hardness Testing (HRC)
scale
indenter (120° diamond pyramid)
specimen
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DuctilityDuctility
stress
strain
%EL, percent elongation
%RA, percent reduction in area
brittle
ductile
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Charpy Impact TestingCharpy Impact Testing
hammer
impact energy Av=mg(h-h´)specific ak=Av/A0
(DIN 50115)
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T-Dependence of T-Dependence of AAvv
BDTT
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Cleavage Fracture at Low Cleavage Fracture at Low TemperaturesTemperatures
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Deformation at Elevated Deformation at Elevated Temperatures: CreepTemperatures: Creep
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Creep TestingCreep Testing
sp e c im e n
w e ig h ts
s tra in g a u g e
fu rn a c e
t
ddt
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Fatigue Loading during ServiceFatigue Loading during Service
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Fatigue TestingFatigue Testing
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Fatigue TestingFatigue Testingpush-pullrotating-bending
counter
load
servohydraulic actuator
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Fatigue-Testing: The S/N DiagramFatigue-Testing: The S/N Diagram
400
500
600
700
800
900
1000
1100
1200
1000 10000 100000 1000000 10000000 100000000
Bruchlastspielzahl N B
Bie
ge
spa
nn
un
g
[MP
a]
Dauerfestigkeit
stress amplitude [MPa]
cycles to failure N
fatigue limit
total life design
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Fracture MechanicsFracture Mechanics
F
F
F
F
m o d e I m o d e II m o d e II I
KIc represents resistance to brittle fracture [MPam0.5]
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Determination of Determination of KKIcIc using Compact using Compact
Tension (CT specimens)Tension (CT specimens)
extensometer
force
displacement