MATERIALS AND STRUCTURES I (CIVN2008A)
ASSESSMENT 6 – Mechanics of Materials Part – Block 2
30 Marks
Question 1 ( 8 marks)
A steel rod of 20 mm diameter passes centrally through a copper tube of 50 mm
external diameter and 40 mm internal diameter. The tube is closed at each end by
rigid plates of negligible thickness. The nuts are tightened lightly home on the
projecting parts of the rod. If the temperature of the assembly is raised by 50°C,
calculate stresses developed in copper and steel. Take E for steel and copper as 200
GN/m2 and 100 GN/m2 and α(steel)=12 × 10−6 , /◦C, α (copper)=18 × 10−6 , /◦
C.
Question 2 (12 marks)
In a tensile test on a specimen of mild steel, 12.5 mm diameter and gauge length of
200 mm, the following results were obtained.
Load
(N)
Extension
(mm)
5 000
10 000 15 000 20 000 25 000 30 000
35 000 40 000
0.040
0.080
0.282
0.121
0.161
0.201
0.242
0.322
a) Plot the Load-extension graph for the given results.
b) Determine the value of Young’s modulus of elasticity.
c) When the specimen was afterwards tested to failure, the maximum load
recoded was 58.5 kN, the diameter of the neck was 7.35 mm and the length
between the gauge marks was 268.7 mm. Determine the ultimate tensile
strength, perceontage reduction of area and percentage elongation.
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Question 3 (10 marks)
A steel rod 5 m long and 30 mm in diameter is subjected to an axial tensile load of
50 kN. Determine the change in length, diameter, and volume of the rod. Take 𝐸 =
2 × 105 N/mm2 and Poisson’s ratio =0.25.
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