lecture 10: fracture analysis + propulsion systems Flashcards
main topics
inadequate design
unanticipated/ excessive loads
deterioration of material properties (fatigue)
unit cells see slide 9
body centred cubic (bcc)
9 atoms
chromium ,(cr,mo,w)
characteristically brittle
face-centered cubic (fcc)
14 atoms
al,cu,fe,ni
characteristically ductile
hexagonal close-packed (hcp)
highest density packing arrangement
be,cu,mg,ti
brittle or ductile
grain boundaries
large grain and long boundaries
small grains and long boundaries
stress fractures see slides
fatigue
stress concentration (localization of high plastic stress)
tensile @ crack
cyclic stress
composites
fibre orientations
fibre matrix volume ratios
ply thickness
ply stacking sequence
curing schedule
corrosion
chemical
electrochemical
pitting
galvanic
crevice
intergranualr
fretting
laminate
fibre waviness
poor fibre matrix volume ratios
turbine Powerplant Failure
Questions you can typically answer with an on-site
examination
Was the engine rotating at impact?
* Was the engine hot at impact?
* Was the engine on fire prior to impact?
* Are rotary components unaccounted for?
turbine Powerplant Failure
Questions you can typically answer during laboratory
examination, accompanied by flight recordings
- Was the engine surging/stalling
- Was Foreign Object Debris ingested
- Was there abnormal vibrations
- Was there abnormally high Exhaust Gas Temperatures
- Did the engine seize (core lock)
- Fuel flow runaway (control malfunction)
- Icing
- Etc…
lab exam techniques
magnetic particle inspection
fourier transform infared spetography (FTIR)
energy dispersive spectrometer
ultrasonic testing (UT)
radiography (xray,ct scans)
magnetic particle inspection
scanning - electron microscope (SEM) - X60000 MAGNIFICATION
optical microscope - x5000
destructive
hardness (brinell / rockwell)
charpy (toughness)
tensile
