Performance Indicies & Materials Selection

Question 1

A performance index
depends on

Cost

Functional requirements

Material properties

Geometric parameters

Answer 1

Functional requirements

Material properties

Geometric parameters

Question 2

Answer 2

1.5

Question 3

Answer 3

line c
The selected line should have a slope of 1

Question 4

Specific stiffness is the same as the material performance index for which one of the following cases?

A light strong beam in tension

A light stiff bar in tension

A light stiff bar in bending

A light stiff bar in torsion

Answer 4

A light stiff bar in tension

Question 5

Given the following graph where E is Young’s modulus, ρ is density and Cm is cost per kilogramme select the best candidates for a low cost bar in tension.

Answer 5

Materials A, E, F

Question 6

Answer 6

Plot a line of slope 2 and select materials below the line (towards the bottom right)
As E is on the y-axis the equation rearranges to log E equals 2 log sigma subscript y minus 2 log M hence slope is 2 and the negative sign indicates we need to choose materials from below the line

Question 7

performance index p is a function of:

Answer 7

p = f[(functional requirements, f), (geometric parameters, G), (material properties, M)] = f(F,G,M)

Question 8

What are the performance index line limitations?