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Q8. Explain why a material may fracture when stressed below its yield point. Give examples of components which might fracture in this way if suitable precautions are not taken. Explain how such fractures can be avoided with reference to the materials chosen, careful design and workmanship.

Q2.a) Define fatigue and fracture and specify the conditions under which it occurs.

b) Describe the different fracture modes and the mechanism of crack propagation in different fracture modes.

Q6.a) Define the cause and effect of thermal stressing in cylinder heads, liners, and pistons.

Explain why thermal stressing is aggravated with an increase in the cylinder bore.

Explain how stress concentration and it's effects is relieved by maintenance and operational practices.

Q9. (a) Describe the properties of each of the following alloys used in marine engineering, giving a practical example for which, each is suited:

(i) cupro-nickel

(ii) white metal

(iii) titanium.

b) Discuss the merits of EACH of the following alloys for use in the casting of large propellers:

(i) nickel aluminium bronze (ii) stainless steel.

c) Describe the tests that may be carried out on steel to be used for ship's side plating.

Q8.  With reference to fatigue of engineering components;

(a) Draw an S/N curve for steel, showing the fatigue limit and two representative stress cycle condition on the graph

(b) Explain how a component is designed to avoid fatigue failure, suiting the S/N curve drawn in part (a)

(c) Explain how poor maintenance and incorrect machinery operation can result in fatigue failure even though a component is designed to operate below the fatigue limit.

Q8. A. Explain the action of EACH of the following metallurgical mechanism:

(i) Creep;          (ii) Brinelling;   (iii) Fretting;     (iv) Fretting corrosion;

B .State, with reasons, where EACH of the mechanisms in occur in ship propulsion System.

Q6. a) Describe Three methods of tracing a superficial crack in a marine machinery component;

b) Explain how propagation of a crack in a machinery component can be arrested.

Describe TWO methods of tracing a superficial crack in a marine machinery component;

Q7. Compare the destructive testing done on engineering materials with non-destructive testing done on engineering components. Briefly describe one destructive test and two non-destructive tests to illustrate your answer

Q2. Describe the following properties of steel and which components are most considered with advantages & disadvantages.

a) Ductility (4)

b) hardness (4)

c) Malleability (4)

d) Toughness (4)

Q9. A. Briefly explain the term fatigue and explain how fatigue failure occur;

B. State the difference between high stress / low cycle and low stress / high cycle fatigue giving an example of each;

C. State how defect in metal can influence the expected safe life of a component;

D. State how fuel injection timing and cylinder power balance can influence the possibility of fatigue cracks developing in the bedplate.

Q1. a) Describe the key phases and microstructures present in the iron-carbon equilibrium diagram and explain their significance in the heat treatment of steel. (8)

b) How do the different regions of the iron-carbon diagram influence the mechanical properties of steel, such as hardness, toughness, and ductility? Provide examples of how specific compositions and heat treatments can achieve desired properties. (8)

Q2.  Describe TWO methods of tracing a superficial crack in a marine machinery component; Explain the procedure for arresting propagation of a crack in a machinery component.