What are the three categories of ceramics?
CMC - Ceramic Matrix Composites
MMC - Metal Matrix Composites
PMC - Polymer matrix composites
Describe the following characteristics for a SiC/SiC Composite:
1. Mechanical
2. Ductility
3. Thermal Conductivity
4. Creep
5. oxidation resistance
- Mechanical - variable depending on form
- Ductility - non-brittle due to disbonding in the matrix arresting cracks. typical ceramics are brittle.
- Thermal Conductivity - very high
- Creep - excellent creep resistance
- oxidation resistance - generally good, but can be a problem
How to calculate heat transfer through refractory wall:
- Q =
- how to add multiple refractory thicknesses
- Q = (k / x) * SA * DeltaT, where x is the wall thickness
- When adding multiple thicknesses, the equation for k/x is 1 / [ (x1 / k1) + (x2 / k2) + … ]
Highly alloyed steel is being austenitized, quenched, then tempered. However, the hardness and strength is not as high as it should be. What action should you take with regard to either changing the austenitizing temp or changing the quench method?
Increase the austenitizing temp to make sure that all carbides are dissolved. Otherwise, ferrite will nucleate at the carbide locations during quench and prevent more martensite formation
How does distance from point source relate to radiation level?
radiation level is proportional to the inverse square of the distance from source
Crack morphology of chlorides SCC
transgranular and branching
crack morphology of hydrogen embrittlement
intergranular on high strength parts
What metallurgy do you need to use caution with when designing for use in hydrogen environment?
Titanium. It becomes embrittled.
Equation for principal stress?
[(stress 1 + stress 2) / 2] +/- sqrt( [(stress 1 + stress 2) / 2]^2 + shear^2)
how do you know if something is a principal stress?
all shear stress related to that direction is zero
Fatigue Life Equation based on number of cycles vs stress
stress = A log(N) + B, where A&B are constants and N is number of cycles until failure
How to Estimate yield strength based on vickers hardness?
HV/3 = YS
must convert HV into Mpa
What are units of a pascal?
N/m^2
