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EXAM COVER SHEET Student name:

Student ID

Campus:

Associate Degree of Applied Engineering (Renewable Energy Technologies)

Subject number: ENMAT101A

Subject name: Engineering Materials and Processes

Semester 1, 2013 Final Exam

Time allowed 1:50 hours plus 10 minutes reading time

General instructions Marks

Write your answers using black or blue pen Total marks: 35% of Subject

Write your name and campus at the top of each page

All questions must be attempted.

No liquid paper (whiteout) can be used – if you make a mistake, just cross out your attempt.

Marks allocated for each question are shown throughout the examination paper. Total marks 100.

Examination aids permitted as indicated

Standard dictionaries

Bilingual dictionaries

Technical dictionaries

Programmable calculators

Non-programmable calculators

No No No No Yes

Other examination aids permitted

Writing implements (pens, pencils, erasers, highlighters) Ruler

Note: Reference information included at end

ENMAT101A Engineering Materials and Processes Semester 1, 2013

Student name: Campus:

Question 1 (8 marks total)

(a) Choose the non-ferrous metal that best matches the properties listed below. Mark with a single “tick” in each row (2 marks)

Tit

aniu

m

Alu

min

ium

Zinc

Tun

gste

n

Lead

Copp

er

Nic

kel

Low density, good electrical conductor, ductile. Alloys have high strength-to-weight ratio.

High electrical conductivity, ductile, can be soldered.

Corrosion resistant, used for surgical implants. Alloys have high strength-to-weight ratio at high temperature.High density, extremely high melting point, hard. Used in high speed steel and high temperature alloys.

High density, low melting point, soft. Used in batteries.

Easy to high pressure die-cast, corrosion coatings of steel.

Corrosion resistant. Makes special alloys for: high temperature, electrical resistance wire, low expansion.

(b) Explain why titanium is more corrosion resistant than aluminium. (1mark)

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(c) What is the main property of magnesium for its use in engineering? (1mark)

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(d) What is the main problem with using magnesium? (1mark)

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(e) What is a Babbit metal and what is it used for? (1mark)

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© TAFE NSW Higher Education 2012Version: X | Day-Month-Year

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(f) A catalytic converter in car exhaust systems improves emissions by completing reactions of unburnt hydrocarbons, reducing Nitrogen oxides and oxidising Carbon monoxide into CO2. Platinum works best, because it attracts the molecules to its surface so the reaction can take place. What other properties about Platinum are important here? What is a disadvantage of using Platinum? (2 marks)

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(g) The mass airflow (MAF) sensor for this car has the following material label: PBT-GF30. Describe this code and any relevance to this operating environment. (2 marks)

PBT: ___

GF30: ___

Environment: ___

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(a) Brass is predominately an alloy of copper and _________________, while bronze is

predominately an alloy of copper and _________________ (1 mark)

(b) The Copper Zinc diagram:

From the diagram above, complete the following;

(i) What type of diagram is this? _________________ (0.5 marks)

(ii) The melting point of copper: _________________(0.5 marks)

(iii) The melting point of zinc: _________________(0.5 marks)

(iv) The melting point of brass: _________________ (0.5 marks)

(c) The majority of engineering brasses are in the range (circle the appropriate symbol/s) :

(1 mark)


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(d) With reference to the Cu/Zn diagram, explain what happens when molten cartridge brass (70/30 brass) slowly cools to 200oC. (2 marks)

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(e) Explain what the letters represent, and what they have to do with copper and zinc. (1 mark)

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(f) Why is de-zincification a problem? Give examples of what can be done about this in both the production of brass and when brass is in service. (2 marks)

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(a) In the earth’s crust, aluminium is more common than iron. Explain why scrap aluminium is more than 10 times the price of scrap steel. (1 mark)

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(b) Explain how aluminium resists corrosion. (1 mark)

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(c) Explain the advantages and disadvantages of using aluminium for electrical wires. (1 mark)

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(d) Explain artificial aging of Aluminium grade 7075T6, using information below. Describe what happens to the microstructure during the various stages of the process with regard to all the relevant data in the table below. (3 marks)

GRADEUTS

(MPa)YS

(MPa)Elongation

%

Annealing Temperature

oC

Solution Temperature

oC

Aging Temperature

oC

7075-O 228 103 17% 413 466-482 -

7075-T6 572 503 11% 413 466-482 121

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(a) Match the most appropriate polymer to each diagram below (a) to (d). (2 marks)

(i) Natural Rubber

(ii) Epoxy

(iii) Low Density Polyethylene

(iv) High Density Polyethylene

(b) Which diagram/s (above) show thermoplastics _____ , and thermosets __ (1 mark)

(c) The melting point of a linear polymer increases with increasing molecular weight. What is the name of the intermolecular force of attraction that causes this? (1 mark)

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(d) Explain the terms amorphous and crystalline when applied to polymers. List some of the physical differences between strongly amorphous and strongly crystalline polymers. Give an example of each. (3 marks)

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(e) Fill in the blanks in the table below. Briefly describe problems in the recycling of each plastic products and give examples of the end use of recycled scrap material. Identify the dominant material in the product and write the appropriate recycling code from the list below. (4 marks)

Product Material Code Problems / Recycled into ….

1. Carbonated drink bottle

2. Telephone

ABS

3. Electrical cable

5. Car tyre

6. Oil container

2


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(a) According to the engineering definition, what is the difference between ceramic and glass? (1 mark)

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(b) Hip replacement prosthesis: In the 1970’s the femoral head stem was stainless steel, and the socket (acetabular component) was Teflon. They lasted only a few years. A more modern one (below) has titanium alloy stem, ceramic ball and HDPE socket.

In the design above, describe the relevant properties of each material that make it a suitable choice in this application. (2 marks)

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(c) Identify the following ceramic materials: Amorphous Silicon Dioxide, Tungsten carbide, Titanium Nitride, Aluminium Oxide. (2 marks)

Product Material Properties required for the task

Saw

Grinding wheel

Drill

Optical fibres

(d) Explain the microstructure differences between amorphous and crystalline silicon dioxide. What is another name for the amorphous state? (1 mark)

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(a) “Safety glass” can refer to laminated or toughened (tempered) glass. Briefly compare each in the table below. (4 marks)

Laminated Glass Tempered Glass

How it is made

Advantages for fabrication and

installation

Advantages in service and applications

Disadvantages

(b) Describe metallic glass and explain its mechanical properties. (1 marks)

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(c) Discuss the arguments (for and against) for the alleged proof that window glass flows over centuries to become thicker at the bottom and thinner at the top. How does this compare with the same claims for lead pipes and flashing? (1 marks)

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(d) What does “float glass” mean? Describe how it is made. (1 mark) ___

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(e) Solar panels can use monocrystalline, polycrystalline or amorphous cell technology. Identify each solar cell type below. Rank by entering 1,2 or 3 in each row. (2 marks)

Identify

Low cost

High solar efficiency

Quick payback of embodied energy

(f) Discuss performance / cost issues of using float, laminated and tempered glass for solar panels. What is the role of the glass? (1 mark)

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(a) To make and set strong concrete there are many factors: Fill in the table below referring to cement properties such as strength, workability, curing time, shrinkage and cost. (6 marks)

What happens if too low or not enough

What happens if too high or too much

Cement ratio

Water Ratio

Curing Temperature

Curing Humidity

Sand (fine aggregate)

Gravel (coarse aggregate)

(b) Describe what a cermet is, and what the intended mechanical properties should be. (1 mark)

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(c) Explain the mechanism of dispersion hardening. (Where small particles can strengthen a ductile metal matrix even when the particles are rounded). (2 marks)

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A frame for a high performance bicycle requires strength, stiffness and low weight.


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Compare alloy steels, aluminium, titanium and CFRP and explain the following: (Refer also to reference section Diagram 1: Strength vs Density and Diagram 2: Specific Stiffness vs Specific Strength).

(a) During the 1990’s, top class cyclists were racing on frames of all four materials – in the same race. Explain with reference to the chart above. (2 marks)

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(b) Chrome Molybdenum steel frames are brazed while aluminium and titanium alloys are TIG welded. Explain the difference and why steel is done differently. (1 mark)

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(c) CFRP bike frames did not dominate until more recently. Explain with reference to the chart above, and your understanding of manufacturing processes. (1 mark)

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(d) Rank the following fibre composites (enter 1, 2 and 3 in each row, where 1 = best). Briefly describe problems or disadvantages of each. (3 marks)

GRP Aramid CFRP

Strength

Stiffness

Low Weight

Briefly describe problems or

disadvantages


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(e) In this energy storage flywheel, a fibre reinforced composite is preferred over a steel flywheel. Why? Give as many reasons as you can. (False or irrelevant reasons will lose marks. E.g “Carbon is cheaper” = false. “Nicer colour” = irrelevant) (3 marks)

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(f) Failure of wind turbine blades. Give advantages and disadvantages of the material chosen for turbine blades. (4 marks)

Storm damage to turbine blades and tower Generator fire

Disadvantages Advantages

Manufacture

Operating performance

Minor repair and

maintenance

Major failure, recycling



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(a) Adhesives can be classified according to the method of curing. Fill in the table below. (3 marks)

Cures by… How it works (brief) Example adhesive and application

Cooling

Chemical reaction

between 2 components

Evaporation

Surface curing

Anaerobic

Heat

(b) What does shelf-life mean, and what is the usual method of extending it? (1 mark)

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(c) Define soldering and brazing according to temperature. (1 mark)

Soldering: ___

Brazing: ___

(d) Name and briefly describe the four welding processes in the table below. (4 marks)

Name How it works Advantages/applications

MMAW

MIG

TIG

ERW

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(a) Domestic water tanks are produced in four different materials: Concrete, steel, polyethylene and fibreglass. Briefly highlight (a few words each) the issues for/against each type of material. (6 marks)

Concrete Steel Polyethylene Fibreglass

Made by…

Transport and

installation

Water quality

Leakage and Repair

Special problems

Recycling

(b) In the solar industry, most of the racking system components (including the solar module frames) are aluminium. Bolts and nuts can be stainless steel, bronze, brass or galvanised steel.

(i) Explain galvanic corrosion with reference to the anodic table of metals. (2 marks)


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AnodicMagnesiumZincAluminium alloysLow alloy steelCast ironLeadAluminium bronze, brassCopperBronze (manganese, silicon)Nickel, SilverStainless steel 302, 304, 316, Alloy 20TitaniumGold, PlatinumGraphiteCathodic

(ii) Why is this type of corrosion more aggressive near the coast? Explain chemically. (1 mark)

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(iii) Briefly describe four ways to counter galvanic corrosion in PhotoVoltaic system structures. (2 marks)

(c) Explain energy content (embodied energy) vs material cost. (Ref Diagram 3 and 4) (1 mark)


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_________

_________

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(d) Why is it economic to recycle aluminium cans but less so for steel ones? (1 mark)

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(e) Describe how you would build a domestic home that has the lowest total of embodied energy + energy efficiency + re-use/recycling. Justify your answer. (Ref Diagram 3 and 4) (3 marks)

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REFERENCE SECTION


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Diagram 1

Diagram 2


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Diagram 3

Diagram 4


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associate degree of applied engineering …€¦ · web viewtitanium aluminium zinc tungsten lead...

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