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Tec111: Introductionto Material Science Question Paper
Tec111: Introductionto Material Science
Course:Bachelor Of Technology In Civil And Structural Engineering
Institution: Moi University question papers
Exam Year:2012
MOI UNIVERSITY
UNIVERSITY EXAMINATIONS 2011/2012 ACADEMIC YEAR
FIRST YEAR FIRST SEMESTER EXAMINATION FOR THE BACHELOR OF ENGINEERING
COURSE CODE: TEC 111
COURSE TITLE: INTRODUCTION TO MATERIAL SCIENCE
INSTRUCTIONS
ANSWER ALL FIVE QUESTIONS; ALL QUESTIONS CARRY EQUAL MARKS
Question One
a) Give two reasons why it is important for an engineering student to study material science and engineering course. [2 marks]
b) Calculate the number of atoms in 1mm3 of copper given that the relative density of copper is 8.96 and its atomic mass is 63.546. [4 marks]
c) Give the reason why Chromium 24 and Copper 29 have irregularities during the filling of the 3d shell in the periodic table of elements. [2 marks]
d) Briefly discuss Rutherford experiment, 1911, which explains the structure of atoms. [4 marks]
e) When is the greatest reign-forcing effect and maximum strength obtained in a fiber reign forced composite material. [2 marks]
Question Two
a) Give two reasons why different polymers have different properties. [2 marks]
b) What do you understand by the following terms as used in material science [4 marks]
I. Condensation polymerization
II. Degree of polymerization
III. Amorphous ceramic
IV. Particle composites
c) Wood being fibrous in nature is highly anisotropic. Explain [2 marks]
d) Explain clearly how a pre-stressed concrete works [6 marks]
Question Three
a) How in reference to engineering materials do the term stress and strain differ [2 marks]
b) A mild steel bar of 25mm diameter, 20cm gauge length hs an extension of 0.15mmunder the load of 7.5 tonnes. Load at elastic limit is 16 tonnes and maximum load is 25 tonnes. Diameter of the rod a fracture is 1.85cm. Find:
I. The elastic limit stress [2 marks]
II. Young`s modulus [2 marks]
III. Percentage elongation [1 mark]
IV. Percentage reduction in area [1 mark]
c) A round bar of metal which is 9mm in diameter and 250mm in length extends by an amount of 0.225mm under a load of 11.8kN. At the same time its diameter contracts by 0.00227mm. Determine:
I. Young`s modulus [3 marks]
II. Shear modulus [3 marks]
Question Four
a) A 20,000n load is applied to a steel bar of cross-sectional area 6cm2. When the same load is applied to an aluminium bar it is found to give the same elastic strain as the steel. Calculate the cross-sectional area of the aluminium bar. Young`s modulus for steel is 2.1x105 MN/m2 and for aluminium is 0.703x105 MN/m2 [3 marks]
b) A 6m long hollow bar of circular section has 140mm diameter for a length of 4m,while it has a 120mm diameter for a length of 2m. The bore diameter is 80mm throughout the length. Find the elongation of the bar, when it is subjected to an axial tensile force of 300kN. Take modulus of elasticity for the bar material as 200Gpa [4 marks]
c) A hollow steel tube 3.5m long has a diameter of 120mm. In order to determine the internal diameter, the tube was subjected to a tensile load of 400kN and extension was measured to be 2mm. If the modulus of elasticity for the tube material is 200x103 N/mm2 determine the internal diameter of the tube(in mm) [4 marks]
d) A reign forced circular section of 50,000mm2 cross-sectional area carries 6 reign forcing bars whose total area is 500mm2. Find the safe load the column can carry if the concrete is not to be stressed more than 3.5Mpa. Take modular ratio for steel and concrete as 18 [3 marks]
Question Five
a) In a tension test on a mild steel rod of 16mm diameter using 80mm gauge length,the following observations were made:
Parameter Parameter value
Extension under a load of 150kN 0.28mm
Load at yield point 311kN
Ultimate load 300kN
Breaking load 290kN
Length between the gauge marks after fracture 7.40mm
The diameter at fracture was 12.4mm.
From data in the above table compute he following engineering material properties:
I. Young`s modulus [1 mark]
II. Yield stress [1 mark]
III. Ultimate stress [1 mark]
IV. Engineering stress [1 mark]
V. True stress [1mark]
VI. Percentage elongation [2 marks]
VII. Percentage reduction in area [2 marks]
b) A steel wire ABC 16m long having a cross-sectional area of 4mm2 weighs 20N (see the figure below). If the modulus of elasticity for the wire material is 200 Gpa, find the deformations(in mm) at C and B [5 marks]
A 8m B 8m C
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