This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Variables Affecting Impact Value”.
1. Above critical speed, what happens to the energy required to rupture a material when striking velocity increases?
a) Increases slowly
b) Increases rapidly
c) Decreases slowly
d) Decreases rapidly
View Answer
Explanation: Above critical speed, the energy required to rupture a material rapidly decreases with increasing striking velocity. This doesn’t happen below the critical speed.
2. Critical velocity is higher for annealed steels than hardened.
a) True
b) False
View Answer
Explanation: The critical velocity is much less for annealed steels. It is higher for hardened steel. It is because of internal stresses.
3. The energy loss should be ____________ by the manufacturer by ________
a) Minimized, heavy foundation of machine
b) Minimized, addition of weight to specimen
c) Maximized, heavy foundation of machine
d) Maximized, addition of weight to specimen
View Answer
Explanation: The energy loss should be minimized by the manufacturer through a heavy foundation of the machine. The fraction of energy is lost due to absorption in vice and structure.
4. A sharp notch ________ the yield stress and ________ the transition temperature?
a) Increase, Increase
b) Increase, decrease
c) Decrease, Increase
d) Decrease, decrease
View Answer
Explanation: The presence of notch affects the impact value. The yield stress increases with a sharp notch. The transition temperature also increases.
5. A ________ notch is preferred in Charpy test.
a) Shallow V-shaped
b) U shaped
c) Shallow U-shaped
d) Keyhole shaped
View Answer
Explanation: A shallow V-shaped notch is preferred in the Charpy test. It is because sharp notch raises yield stress and transition temperature.
6. The energy absorbed by a notched test bar of a ductile material under impact load is commonly called ________
a) Static toughness
b) Impact strength
c) Notch-bar toughness
d) Fracture energy
View Answer
Explanation: The energy absorbed by a notched test bar of a ductile material under impact load is commonly called Notch-bar toughness. The energy absorbed by the material at fracture is a measure of impact strength. It is also called impact toughness.
7. The transition temperature is found to be ________ as the grain size decreases.
a) Increasing
b) Decreasing
c) Remaining constant
d) First increasing then decreasing
View Answer
Explanation: The transition temperature is found to be decreasing as the grain size decreases. Yield strength is a function of grain size. It is related by the Hall-Petch relationship.
8. Value of Ï’m will decrease if _________
a) Increase in number of unpinned dislocation sources
b) Increase test temperature
c) Increase crack velocity
d) Blunting of crack
View Answer
Explanation: Ï’m is plastic work done around the crack. It will decrease if crack velocity is increased. It will enhance with an increase in test temperature.
9. What does an increase in temperature causes?
a) Increase in PN stress
b) Decrease in dislocation velocity
c) Increase in fracture energy
d) Decrease in slip planes.
View Answer
Explanation: With an increase in temperature, fracture energy increases. It is because of the decrease in P-N stress. It also increases dislocation velocity.
10. Which element decreases DBTT of steel?
a) Ni
b) Mn
c) Al
d) Mo
View Answer
Explanation: Mn content when increased 0.10%, lowers DBTT by 5°C. P, Si and O raise the DBTT of steel. Carbon also raise the DBTT.
11. What is aluminum responsible for in steel?
a) Decrease notch toughness
b) Deteriorate strength
c) Lower oxygen content
d) Increase growth strength
View Answer
Explanation: Aluminium combine with oxygen and nitrogen. It creates aluminum nitride. It enhances the rate of nucleation and strength.
12. Which element increases DBTT of steel?
a) Ni
b) Mn
c) Al
d) Mo
View Answer
Explanation: Molybdenum raises DBTT of steel. Ni and Mn lowers DBTT. Al combines with Nitrogen and lower DBTT.
13. Strain ageing raises the DBTT.
a) True
b) False
View Answer
Explanation: Strain ageing raises the DBTT of steel. It reduces tensile ductility and notch toughness of low carbon steel.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
To practice all areas of Mechanical Behaviour & Testing of Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.
