Material Selection

Question 1

three stages in material selection

Answer 1

1. Screening (remove inappropriate materials)
2. Ranking ***
3. Specialist factors (for those at the top of the ranking list)

Question 2

specifications for choosing a material for a pressure vessel

Answer 2

maximise safe operating pressure

requires leak-before-break - ie. fast fracture does not occur even if cracks=wall thickness

Question 3

define merit index

Answer 3

aka performance index
an expression of material property parameters allowing materials to be ranked

created by ELIMINATING THE VARIABLE

Question 4

σ(failure) for different types of materials

Answer 4

for metals / ductile polymers, σ(f) = yield strength (elastic limit)

for ceramics / brittle polymers, σ(f) = tensile strength

Question 5

what does “yield-before-break” mean?

Answer 5

often for smaller pressure vessels - deforms plastically before breaking