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FINAL EXAMINATION

Subjects/Codes :Engineering Materials/ INT220801I

Smt/Program :4/Int.Program/Chemical Engineering

Lecturer : Dr.Ir.Myrna Ariati MS

Date/Time : Tuesday, May 29th 2012/ 120 minutes

Please finish 5 from 7 problems belows, accept that number 7 is a must done problem

(Total 5 problems)

1. (a) Compare the fatigue limits for Poly (methyl methacrylate) (Figure15. 11, please draw in your paper)) and the cast iron for which fatiguedata are given in Problem 8.20.(b) Compare the fatigue strengths at 10 6 cycles for Nylon (dry, inFigure15.11) and red brass (Figure 8.34). Please explain your answer.

2. Please explain the influence of the following factor to the mechanicalproperties of a semicrystalline polymer, ;a. Degree of crystallinityb. Deformation by drawingc. Molecular Weightd. Annealing of an undeformed material

3. For the following pairs of alloys that are coupled in seawater, predict the possibility of

corrosion; if corrosion is probable, note which metal/alloy will corrode.explain yourreason

(a) Aluminum and magnesium

(b) Zinc and a low-carbon steel(c) Brass (60 wt% Cu40 wt% Zn) and Monel (70 wt% Ni30 wt% Cu)

(d) Titanium and 304 stainless steel

(e) Cast iron and 316 stainless steel

4. A Cd/Cd 2+ concentration cell is constructed in which both electrodes are pure Cd. The Cd2+ concentration for one cell half is 1.0 M, for the other, 10-2 M. Is a voltage generated

between the two cell halves? If so, what is its magnitude and which electrode will beoxidized? If no voltage is produced, explain this result.

b. An electrochemical cell is composed of pure cadmium and pure Zn electrodes

immersed in solutions of their respective divalent ions. For a 0.6Mconcentration ofCd2+, the Zn electrode is oxidized yielding a cell potential of 0.810 V. Calculate the

concentration of Zn2+ ions if the temperature is 30C.

5. Is it possible to produce a continuous and oriented aramid Carbon epoxy matrix

composite having longitudinal and transverse moduli of elasticity of 57.1 GPa and 4.12

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GPa, respectively? Why or why not? Assume that the modulus of elasticity of the epoxy

is 2.4 GPa. (Use table 16.4)

6. A large-particle compqosite consisting of Molybdenum particles within a copper matrix

is to be prepared. If the volume fractions of Molybdenum and copper are 0.70 and 0.30,

respectively, estimate the upper limit for the specific stiffness of this composite given thedata that follow

Specific Gravity Modulus of Elasticity (GPa

Copper 8.9 110

Molybdenum 10,2 324

7. Some examples of materials substitutions in automobilesmanufacture are as follows:

a. Certain components of the metal body replaced with plastic orreinforced plastic parts.

b. Metal fuel tanks replaced with plastic or compositec. Metallic engine components replaced with ceramic and compositesparts.

d. All metal driveshafts replaced with composites driveshafts.e. Cast Iron engine blocks changed to cast aluminum

Explain the reason of the changes/ substituting the existing materials of eachchanges (from a to e) according to performance or properties of thematerials, or from manufacturing, assembly, or costs of materials andprocessing.