# Strength of Materials Questions and Answers – Thermal Stress

This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Thermal Stress”.

1. The thermal stress is a function of _____________
P. Coefficient of linear expansion
Q. Modulus of elasticity
R. Temperature rise
a) P and Q
b) Q and R
c) Only P
d) Only R

2. A steel rod is heated from 25 to 250 degree celcius. Its coefficient of thermal expansion is 10-5 and E = 100 GN/m2. if the rod is free to expand, the thermal stress developed in it is:
a) 100 kN/m2
b) 240 kN/m2
c) Zero
d) Infinity

3. Which one of the following pairs is NOT correctly matched?
a) Temperature strain with permitted expansion – ( αTl – δ)
b) Temperature thrust – ( αTE)
c) Temperature stress – (αTEA)
d) Temperature stress with permitted expansion – E(αTl – δ) / l

4. A steel rod of length L and diameter D, fixed at both ends, is uniformly heated to a temperature rise of δT. The Youngs modulus is E and the coefficient of linear expansion is unity. The thermal stress in the rod is ____________
a) Zero
b) T
c) EδT
d) EδTL

5. A uniform, slender cylindrical rod is made of a homogeneous and isotropic material. The rod rests on a frictionless surface. The rod is heated uniformly. If the radial and longitudinal thermal stress are represented by σx and σz, then ___________
a) σx = 0, σy = 0
b) σx not equal to 0, σy = 0
c) σx = 0, σy not equal to 0
d) σx not equal to 0, σy not equal to 0

6. which one of the following are true for the thermal expansion coefficient?
a) αaluminium > αbrass> αcopper > αsteel
b) αbrass > αaluminium > αcopper > αsteel
c) αcopper > αsteel > αaluminium > αbrass
d) αsteel > αaluminium > αbrass > αcopper

7. The length, coefficient of thermal expansion and Youngs modulus of bar A are twice of bar B. If the temperature of both bars is increased by the same amount while preventing any expansion, then the ratio of stress developed in bar A to that in bar B will be ___________
a) 2
b) 4
c) 8
d) 16

8. The length, Young’s modulus and coefficient of thermal expansion of bar P are twice that of bar Q. what will be the ration of stress developed in bar P to that in bar Q if the temperature of both bars is increased by the same amount?
a) 2
b) 8
c) 4
d) 16

9. A steel bar 600mm long and having 30mm diameter, is turned down to 25mm diameter for one fourth of its length. It is heated at 30 C above room temperature, clamped at both ends and then allowed to cool to room temperature. If the distance between the clamps is unchanged, the maximum stress in the bar ( α = 12.5 x 10-6 per C and E = 200 GN/m2) is
a) 25 MN/m2
b) 40 MN/m2
c) 50 MN/m2
d) 75 MN/m2

10. A cube having each side of length p, is constrained in all directions and is heated unigormly so that the temperature is raised to T.C. What will be the stress developed in the cube?
a) δET / γ
b) δTE / (1 – 2γ)
c) δTE / 2 γ
d) δTE / (1 + 2γ)

11. A steel rod 10mm in diameter and 1m long is heated from 20 to 100 degree celcius, E = 200 GPa and coefficient of thermal expansion is 12 x10-6 per degree celcius. Calculate the thermal stress developed?
a) 192 MPa(tensile)
b) 212 MPa(tensile)
c) 192MPa(compressive)
d) 212 MPa(compressive)

12. A cube with a side length of 1m is heated uniformly a degree celcius above the room temperature and all the sides are free to expand. What will be the increase in the volume of the cube? Consider the coefficient of thermal expansion as unity.
a) Zero
b) 1 m3
c) 2 m3
d) 3 m3

Thermal stress is mechanical stress caused by a change in the temperature of a substance in mechanics and thermodynamics. In general, the bigger the temperature difference, the greater the potential for stress. A significant change in temperature can cause thermal shock, which can result in cracking or breaking. Thermal expansion and contraction cause thermal stress. When increasing gasoline ruptures a tank, thermal stress can be destructive. It’s also handy when two pieces are bonded together in the manufacturing process by heating one and then slipping it over the other and allowing the combination to cool.