• July 11th, 2015

Engineering

Paper, Order, or Assignment Requirements

 

few questions to be answered

5119ENG Test-referral

Module Name:                     MATERIALS AND PROCESSES

Module Code:                      5119ENG

Weighting:                             15% of Final Module Mark

 

  1. What is work hardening? The effects of cold work (strain hardening) on the properties of an aluminium alloy are shown in Figure Q1. Assuming this alloy has a single phase microstructure (aluminium solid solution, or Al). Sketch a schematic stress-strain diagram for the alloy at 0, 20 and 60 percent cold work.

 

 

(15 Marks)

  1. The lower yield point for an iron that has an average grain diameter of 5.5x 10-2 mm is 130 MPa. At a grain diameter of 10x 10-3 mm, the yield point increases to 236MPa. At what grain diameter will the lower yield point be 205 MPa?

(10 Marks)

  1. What is eutectic reaction?What is eutectoidreaction?Explain the microstructure  generated by these reactions. Give examples according to Fe-C phase diagram.

(10 Marks)

  1. Use the Pb–Sn diagram in figure Q4 to answer the following questions.

(a) What are the values of the two state variables at point 1?

Composition: _ _ _ _ _ _ _ _ _ _ _ _

Temperature: _ _ _ _ _ _ _ _ _ _ _ _

 

(b) The alloy corresponding initially to the constitution point 1 is cooled veryslowlyto room temperature.

At which temperatures do changes in the number or type of phases occur?

_ _ _ _ _ _ and_ _ _ _ __ _

What phases are present at point 2? _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. How much of each phases are there in the alloy? _ _ _ _ _ _ _ _ _ _ _ _ _ and _ _ _ _ _ _ _ _ _ _ _ _ _

What phases are present at point 3? _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. How muchof each phasesare there in the alloy? __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ and _ _ _ _ _ _ _ _ _ _ _ _ _

(c) Similarly, the alloy corresponding to the constitution point 4 is cooled to room temperature. Identifythe following:

Initial composition and temperature: _ _ _ _ _ _ _ _ _ _ _ _

Initial phase(s): _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Temperature at which change of phase occurs: _ _ _ _ _ _ _ _ _ _ _

Final phase(s) (when temperature drops below 155°C): _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

(14 Marks)

  1. A hypo-eutectoid steel contains 1.1wt% carbon. Calculate the total weight percent ferrit and the total weight percent cementite in the steel, and in the cementite. How much pro-eutectoid  cementite and eutectoid cementite are there in the  steel?

(10 Marks)

 

  1. Describe  the following heat treatment processes, purposes, and give their applications.

(a) Full annealing

(b) Process anneal

(c) Normalizing

(d) Quenching

(e) Tempering

(f) Austempering

(g) Martempering

(21 Marks)

  1. A uniaxial (with the fibres running along the length) carbon fibre reinforced epoxy composite of size 50mm x 500mm x 10mm (w x l x h) with a fibre volume fraction of 0.55 is subjected to a load of 20 kN in the direction of the fibres.
  2. Calculate the density of the composite
  3. Calculate the axial and transverse modulus
  4. With isostrain condition, the load carried by the fibres and the load carried by the matrix.
Uniaxial high strength carbon fibre reinforced epoxy
Density (Mg.m3) Elastic modulus (GPa) Tensile strength (MPa) Failure strain(%)
Carbon fibre 1.75 300 axial 3400 1.1
Epoxy matrix 1,2 3 75 3

 

 

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