Choice of materials

TAFE NSW -Technical and Further Education Commission

www.highered.tafensw.edu.au

ENMAT101A Engineering Materials and ProcessesAssociate Degree of Applied Engineering (Renewable Energy Technologies)Lecture 27 – Choice of materials


Choice of materials

EMMAT101A Engineering Materials and Processes

Reference Text Section

Higgins RA & Bolton, 2710. Materials for Engineers and Technicians, 5th ed, Butterworth Heinemann

Ch 27

Reference Text Section


Introduction (Higgins 27)


Bicycle development - frames

Ashby diagram: Specific strength vs Specific stiffness

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/spec-spec/basic.html


27.2 Selection of materials (Higgins 27.2)


• The ability of the material to withstand service conditions.• The method(s) by which it will be shaped.• The overall cost, i.e. the cost of the material(s), with in some casesthe availability of the material, and the cost of the shapingprocess(es).


27.3 Service requirements (Higgins 27.3)


Mechanical propertiesPhysical propertiesChemical properties27.3.1 Tensile strength and specific strength27.3.2 Stiffness, modulus of elasticity and specific modulus27.3.3 Toughness and impact value27.3.4 Fatigue resistance27.3.5 Creep resistance27.3.6 Refractoriness27.3.7 Friction and wear resistance27.3.8 Stability in the environment27.3.9 Electrical conductivity27.3.10 Relative costs of important engineering materials


27.4 Choice of shaping process (Higgins 27.4)


• Malleability• Ductility• Strength• The effects of temperature on the above properties• Castability• Machinability• Can it be heat treatment?• How can it be joined?




27.4.1 Processes• Number of components required• Equipment, tooling and labour costs, i.e. the capital costs to set up aprocess and then the running costs• Processing times• Material costs and availability• Component form, detail such as holes required, and dimensions• Dimensional accuracy and surface finish required




27.8.2 Changing conditions


Environmental Factors (Additional)


Disposal (bury it or burn it)Reuse (collect it intact, clean it up and use it again)Recycle (collect it as scrap and recover the material and use it somehow).

• Aluminium is very energy intensive to produce from ore, but as it is easy to remelt, it is particularly cost effective to recycle.• Although thermoplastics can be easily recycled once separated, the bulkiness of scrap polymer products like drink bottles means that very large volumes have to be collected, which is rarely economic.• Even if they can be collected, mixed thermoplastics are difficult to separate and it is probably more economic to burn the material to produce energy.• In spite of their higher cost, composites are difficult to recycle because the fibre and matrix cannot easily be separated, and ceramics cannot effectively be recycled at all.


Recycling (Additional)


Ashby DiagramRecycle Fraction - Cost

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/recycling-cost/NS6Chart.html


Energy cost (Additional)


Ashby DiagramEnergy content - Cost

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/energy-cost/NS6Chart.html


Selection Summary (Additional)


Overview

Advanced Design and Technology Third Edition,

Norman, Cubitt, Urry and Whittaker. Longman 2000

p363



Wikipedia: Welding

Resources.

HI-RESOLUTION ASHBY CHARTS: http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/hardcopy/colour/Photoshop300dpi /

DESIGN CASE STUDIES AND TUTORIALhttp://www-materials.eng.cam.ac.uk/mpsite/design.html

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/hardcopy/colour/Photoshop300dpi/



http://www-materials.eng.cam.ac.uk/mpsite/design.html



http://en.wikipedia.org/wiki/Welding

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/spec-spec/basic.html


Glossary


Specific (density/stress etc)Mechanical propertiesPhysical propertiesChemical propertiesService conditionsDuty cycleIndustrial designManufacturing energy contentRecycle fractionDisposalRe-useRecycleProduct life-cycle


QUESTIONS: Joining of MaterialsHiggins Ch27, Ashby, Norman

1. Define all glossary terms2. On the specific stiffness - strength chart (Ashby Chart), the bubbles for the metals and alloys

tend to be elongated parallel to the strength axis. By considering the physical origins of Young's modulus and strength in these materials, explain why this is so. (Norman 2000)

3. Explain why bike frames are made from steel, aluminium alloy, titanium alloy and carbon fibre composites. Why are carbon fibre composites and titanium generally only found in performance racing bikes. Discuss the practicality of making a bicycle frame out of a polymer. (Norman 2000)

4. The dominant material in car bodies is steel, but there is now fierce competition from aluminium and glass fibre composites. Use the energy content and recycle fraction selection charts to compare how these materials compete with steel in a life cycle analysis of the car. (Norman 2000)

5. Briefly the relative advantages and disadvantages of timber, metal and plastic window-frames. Your answer should refer to one specific named material from each of the three groups of materials: (i) manufacturing methods employed; (ii) durability and maintenance; (iii) aesthetic factors. (Norman 2000)



QUESTIONS: Joining of MaterialsHiggins Ch27, Ashby, Norman

6. Research the manufacture of large wind turbine blades. List the required performance needs, the potential materials and associated production processes. You may need to research the size, design life, factors influencing wear, storm and other damage, risk factors. (Norman 2000)

7. Old cars have metal door handles but today they are mostly plastic. Investigate the older metal door handles and their finish and compare to the modern ones. List the reasons and outline the pro’s and con’s of such a change. Describe design changes necessary when switching from a metal to a plastic.

8. Designing and making a one-off product is very different to producing many thousands. Using, as an example, a project you have made, discuss and sketch the changes which would be needed to make it viable for mass production. Your answer should compare your one-off product with a similar mass produced one in terms of: (i) choice of material, (ii) shaping and forming, (iii) joining and assembly, (iv) applying finishes, and (v) evaluating and testing. (b) Discuss the disadvantages of mass production of products. (Norman 2000)

9. Explain how a CO2-based penalty/incentive scheme (carbon-tax) would influence material and process selection for a significant area of industry (e.g. transport, housing, manufacturing etc). What are the pros and cons of this concept in terms of meeting an environmental objective? Can you think of a better way to manage environmental resources?


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Choice of materials