goals introduce key properties introduce ways to measure show testing options dimensions composition hardness indicate errors sensitivities show test differences 2 Property Distributions ID: 616025
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Slide1
Analysis Techniques
goals
introduce key properties
introduce ways to measure
show testing options dimensions, composition, hardness
indicate errors, sensitivities
show test differencesSlide2
2
Property Distributions
normal distribution
Gaussian, bell curve
best for random errors
operator, machine, room conditions
Weibull distribution
exponential
best for inherent flaw variation
voids, defects, cracksSlide3
Weibull Distribution
F(S)
is cumulative failure probability
S
is stress
V
is volume in useVO is volume in testingSO is characteristic strengthSU is proof stress
3Slide4
Distribution Comparison
4Slide5
Typical Plot
5Slide6
Component Mass Variation
6Slide7
Normal Distribution
X
is value
U
A
is averageσ is standard deviationP(X) probability density, frequency
7Slide8
Hand Tool Dimensional Tests
8Slide9
Dimensional Testing
micrometers, calipers, plug gauges, laser profile, shadow profile, coordinate measuring machines
9Slide10
Process Capability
comparison of variation with allowed range
maximum or minimum – average divided by three standard deviations
two values for max or min, smaller is process
C
pk
seek values of 1.33 10Slide11
Dimensional Budget
realize many features and tight tolerances add greatly to cost
try to relax tolerances where possible
gives less restriction
uses coefficient of variation
11Slide12
Composition Tests
X-ray diffraction (XRD)
X-ray fluorescence (XRF)
atomic absorption (AA)
combustion (Leco) C, O, N, S
energy dispersive spectroscopy (EDS)
12Slide13
X-Rad Diffraction Output
13Slide14
Fluorescence Analysis
14Slide15
Combustion Analysis
15Slide16
Electron Microscope
16Slide17
SEM Image
17Slide18
SEM Image
18Slide19
Energy Dispersive Spectroscopy
19Slide20
Accuracy
+ / - 5 % XRD
+ / - 1 % EDS
+ / - 0.01 % AA, XRF
20Slide21
Density (Porosity)
simple – measure mass and volume
units g/cc or kg/m
3
water 0.997 g/cc
steel 7.9 g/cctungsten 19.3 g/cccomposite density linear with vol %21Slide22
Composite Theoretical Density
W
= weight fraction
ρ
= theoretical density of phase
22Slide23
Porosity Effects
pores degrade most engineering properties
15 % porosity gives
25 % lower thermal conductivity
40 % lower elastic modulus
50 % lower strength
65 % lower ductility70 % lower fracture toughness23Slide24
Porosity
convert density to fractional
fractional density = measured density / theoretical
porosity = 1 – fractional density
can measure directly via microscopy
24Slide25
Archimedes Density Technique
water displacement
25Slide26
Mass Determinations
M
= mass
1
= prior to immersion
2
= after filling pores (if porosity is high)3 = immersed in waterW = indicates wire mass 26Slide27
Water Immersion
27Slide28
Pycnometry
gas P-V measurements
use standard volumes
sample displaces part of volume, changes pressure
less accurate
handles any shape
28Slide29
Two Chamber Pycnometry
29Slide30
Pycnometer Test Device
30Slide31
Hardness
resistance to indentation
mixture of mechanical properties
yield strength
elastic modulus
work hardening
Vickers = microhardness (microscope)Rockwell = macrohardness31Slide32
Standard Tests
32Slide33
Rockwell Hardness Testing
33Slide34
Example Indentation
34
RHB RHCSlide35
Vickers Microhardness Testing
35Slide36
Example Indentation
36Slide37
37
Key Points
means to measure and specify
many possible tests
some tests are easy, widely used
chemistry, density, hardness typical
other tests are destructivevalues differ between tests