materials selection

Question 1

what are the stages in material selection?

Answer 1

screening
ranking
specialist factors

Question 2

what is the equation for hoop stress?

Answer 2

σ = Pr/t
Pr = pressure

Question 3

what does leak before break mean?

Answer 3

fast fracture must not occur even if cracks become equal to the wall thickness

Question 4

what is the equation for a leak before break requirement?

Answer 4

Kc^2 / σf = M1
M needs to be maximised

σf = stress at failure

Question 5

what is M?

Answer 5

merit index

Question 6

what is σf for different materials?

Answer 6

metals and ductile polymers: yield strength
ceramics and brittle polymers: tensile strength

Question 7

what is the order of size microscope can see?

Answer 7

light
SEM
TEM
AFM

Question 8

what sort of image do we get in light microscopy and how do we change this?

Answer 8

unfocused background part
use CLSM

Question 9

what happens in CLSM?

Answer 9

pinhole blocks out of focus light

Question 10

what does CLSM do?

Answer 10

allows for high resolution imaging at different depths

Question 11

what are the main features of an SEM?

Answer 11

a beam of electrons is accelerated in a vacuum
focused by lenses
scanned across surface by coils

Question 12

what happens in SEM preparation?

Answer 12

mount onto a stub
coat with a conductive material

Question 13

where does ESEM occur and what does this mean?

Answer 13

gaseous environment so sample can be wet and uncoated