Material Selection and costing

Question 1

What does material selection effect

Answer 1

Part function, cost, manufacture process, Quality test method, ability to be painted coated etc

Question 2

Name 2 general material properties

Answer 2

Density and price

Question 3

Name 2 Mechanical Properties

Answer 3

Elastic modulus (stiffness)
Ultimate strength

Question 4

What is a material index dependant on

Answer 4

Function, Geometry, How we want to optimise performance

Question 5

Give an example of how we might want to optimise performance

Answer 5

Light and strong or strong and cheap

Question 6

For material selection what is the function

Answer 6

What the part needs to do, e.g. support a tensile load or support a bending load

Question 7

What are the objectives in material selection

Answer 7

Goals that need to be achieved when selecting the material

e.g. minimise mass or minimise cost

Question 8

What are constraints on material selections

Answer 8

Specifications that constrain the selection when trying to meet the objectives
e.g have to have a thermal conductivity > 10

Question 9

What are free variables in material selection

Answer 9

Parameters not fixed by the initial design specification,

e.g. Cross sectional area or Material

Question 10

What is the first step of the material selection strategy

Answer 10

Identify the functions and objectives and constraints

Question 11

The 2nd step of the selection strategy is to Screen, what does screening use

Answer 11

Constraints

Question 12

What would you rank the material choices using for the 3rd selection step

Answer 12

Material Index

Question 13

For an example to select a material for the lightest stiffest tie What is the Function

Answer 13

Safely support a tensile load without breaking

Question 14

Light/ stiff tie. What are the free variables

Answer 14

Cross sectional area and material

Question 15

Light/ stiff tie, what is the objective

Answer 15

Minimise mass

Question 16

Light/stiff tie. What is the constraint

Answer 16

CSA must be strong enough to keep stress < failure stress

Question 17

What material index would you use for a Light/stiff tie

Answer 17

(failure stress)/(density)

Question 18

For a light/strong tie with a minimum value for electrical conductivity how many coupled constraints are there and what are they

Answer 18

2, Lightest/strongest

Question 19

For a light/strong tie with minimum electrical conductivity what is the uncoupled constraint

Answer 19

Electrical Conductivity

Question 20

For a problem with multiple constrains what constraint would you apply first

Answer 20

The uncoupled constraints

Question 21

How many material indices would you need for the lightest/strongest/stiffest tie

Answer 21

2

Question 22

What is the material index for a light/stiff tie

Answer 22

(density)/(young’s modulus)

Question 23

What would be the equation for the minimum mass a tie will have using a given material if it is to meet both constraints (m’)

Answer 23

m’=max(m1,m2)

Question 24

What is the equation for m1, the mass for the lightest strongest tie

Answer 24

m1>FxLx((density)/(failure stress))

Question 25

What is the equation for m2, the mass of the lightest strongest tie

Answer 25

m2>SxL^2x((density)/(Youngs modulus))

Question 26

For the cheapest strongest tie what is the objective

Answer 26

Minimise cost

Question 27

For cheapest strongest tie what is the constrain

Answer 27

Area of rod must be great enough so that stress stays bellow failure stress

Question 28

For cheapest strongest tie what is the Free variable

Answer 28

Area

Question 29

What is the basic equation for cost

Answer 29

Cost=mass x Cost per part

Question 30

What is the material index for the cheapest strongest tie

Answer 30

(failure strength)/((density) x (cost per part))

Question 31

Name some basic shaping processes

Answer 31

Casting, moulding, deformation, powder formation

Question 32

Name secondary shaping processes

Answer 32

Drilling, punching, turning

Question 33

Name a property enhancing process

Answer 33

Heat treatment

Question 34

Name some joining processes

Answer 34

Adhesives, welding, fastening

Question 35

Name some finishing processes

Answer 35

Polishing, Coating, Painting, Turning

Question 36

List the key process steps in order

Answer 36

``` Basic shaping secondary shaping Property enhancing Joining Finishing ```

Question 37

What is the process selection dependant on

Answer 37

Material selection, size, shape, precision, quality of parts

Question 38

In process selection what are the classification steps

Answer 38

Family class member attribute

Question 39

What does the family of process selection influence

Answer 39

Function

Question 40

What does the attribute of the process selection influence

Answer 40

Constraints

Question 41

What is the economic batch size

Answer 41

Size found by experience to e competitive in terms of cost

Question 42

How do batch size, investment cost and rate of production relate

Answer 42

Higher the batch size the higher the investment cost but also the higher the rate of production

Question 43

In the cost model what is Cm

Answer 43

Cost of material £/kg

Question 44

In the cost model what is Ct

Answer 44

Dedicated cost £

Question 45

In the cost model what is Cc

Answer 45

Capital cost £

Question 46

In the cost model what is the Coh

Answer 46

Overhead cost per hour £/hour

Question 47

in the material cost equation what is f

Answer 47

The scrap fraction

Question 48

In the dedicated cost equation what do n and nt mean

Answer 48

n is the number of parts | nt is the number of parts before replacing

Question 49

In the capital cost equation what does Two mean

Answer 49

Capital write off time

Question 50

In the capital cost equation what does L and n' mean

Answer 50

L= labour cost and n'= rate at which units are produced

Question 51

What is the cost per part equal to

Answer 51

material cost per part + dedicated cost per part + overhead cost per part