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PowerPointPresentation
Chapter 8
Fractography and Failure Analysis
Fractography Fracture SurfaceOrientation Fracture Surface
Morphology Failure Analysis
Destructive Examination FailureAnalysis Report
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Chapter 8Fractography and Failure Analysis
Fractography is
performed at
macroscopic and
microscopic levels
of magnification.
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Chapter 8Fractography and Failure Analysis
Ductile metals loaded under
tension will fracture at a 45
angle to the tensile stress. Brittle
metals loaded under tension will
fracture perpendicular to thetensile stress.
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Chapter 8Fractography and Failure Analysis
Necking is the
reduction of the
cross-sectional area
of a test specimen.
Shear lip is the 45final fracture of a
test specimen.
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Chapter 8Fractography and Failure Analysis
Ductile metals loaded under
compression will bulge but
do not usually fracture.
Brittle metals loaded under
compression will fracturealong planes parallel to the
compression stress but will
not bulge.
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Chapter 8Fractography and Failure Analysis
Ductile metals loaded under
torsion will fracture
perpendicular to the axis of the
metal (parallel to the torsional
stress). Brittle metals loadedunder torsion will fracture in a
spiral at a 45 angle to the axis
of the metal (parallel to the
tensile stress).
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Chapter 8Fractography and Failure Analysis
Ductile dimples caused by
microvoid coalescence are
characteristic of ductile
fractures.
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Chapter 8Fractography and Failure Analysis
Brittle fractures
occur by
transgranular
cleavage or
intergranularseparation.
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Chapter 8Fractography and Failure Analysis
Arrest lines are an indication
of a progressive fracture.
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Chapter 8Fractography and Failure Analysis
Mechanical nicks or
corrosion pits on the
surface of a component
can sometimes be
used to locate theinitiation points of a
fatigue fracture.
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Chapter 8Fractography and Failure Analysis
At high magnification,
fatigue crack propagation
is revealed as striations.
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Chapter 8Fractography and Failure Analysis
Microcracks in the
morphology are further
evidence of fatigue.
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Chapter 8Fractography and Failure Analysis
The origin of a fracture is the point
where the fracture is initiated.
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Chapter 8Fractography and Failure Analysis
Ratchet marks are an
indication of a fracture
with multiple origins.
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Chapter 8Fractography and Failure Analysis
The morphology of a fracture face changes as the
force for the fracture changes.
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Chapter 8Fractography and Failure Analysis
A checklist may be used to review the
stress, temperature, and operating
conditions at the time of failure.
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Chapter 8Fractography and Failure Analysis
A checklist may be
used to indicate
material characteristics.
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Chapter 8Fractography and Failure Analysis
A failure overview can pinpoint
areas that require more
detailed investigation.
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Chapter 8Fractography and Failure Analysis
An ultrasonic cleaning
bath of organic solvent is
used to remove light
amounts of grease,
deposits, or residues.
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Chapter 8Fractography and Failure Analysis
Cathodic cleaning is
used to remove
adherent deposits
from a metal surface.
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Chapter 8Fractography and Failure Analysis
A checklist may be used to
determine which features
to look for during
macroscopic examination.
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Chapter 8Fractography and Failure Analysis
Photomacrography
is accomplished
using a digital
overhead camera.
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Chapter 8Fractography and Failure Analysis
Next to sunlight, flashlight
is the best light source for
color photography of
fractured surfaces.
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Chapter 8Fractography and Failure Analysis
Proper selection and use of lighting
methods permits key features on a
fracture surface to be revealed.
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Chapter 8Fractography and Failure Analysis
The electron beam
interaction with a
specimen causes
various types of
emissions. Two types,backscattered
electrons and
secondary electrons,
can be used to form animage of the surface.
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Chapter 8Fractography and Failure Analysis
EDXA identifies and
measures the
concentration of
chemical elements
present in a specimen.
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Chapter 8Fractography and Failure Analysis
X rays are emitted from a
teardrop-shaped volume
of a specimen.
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Chapter 8Fractography and Failure Analysis
Electron probemicroanalyzers use
WDXA to analyze
chemical elements
present inmicrometer-size
areas of a specimen.
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Chapter 8Fractography and Failure Analysis
An X-ray map can becompared to an
electron micrograph
of the fracture
surface to reveal thechemical elements in
a specimen.
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Chapter 8Fractography and Failure Analysis
A minimum of twometallurgical mounts are
produced from specimens
removed from the bulk of
the metal.
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Chapter 8Fractography and Failure Analysis
The specimen from the fractureface must be carefully cut,
mounted, ground, and polished
to reveal the fracture origin.
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Chapter 8Fractography and Failure Analysis
Failure analysis reportsare documents that
describe the cause(s)
of a failure and offer
recommendationsabout prevention of
future failures.
