MS MS in Mechanical Engineering 2 — Questions and Answers
Question 1: In materials science, what is the 'yield strength' of a material?
- The stress at which a material begins to deform plastically (Correct answer)
- The maximum stress a material can withstand before fracture
- The stress at the elastic limit divided by strain
- The energy absorbed during fracture per unit area
Correct answer: The stress at which a material begins to deform plastically
Yield strength is the stress level at which a material transitions from elastic (reversible) to plastic (permanent) deformation, marking the end of the linear elastic region.
Question 2: What does CNC stand for in manufacturing?
- Computer Numerical Control (Correct answer)
- Centralized Network Computing
- Continuous Numerical Cutting
- Composite Nano Coating
Correct answer: Computer Numerical Control
Computer Numerical Control (CNC) refers to automated machine tools controlled by pre-programmed computer sequences that precisely direct cutting tools, lathes, and mills.
Question 3: Which law relates the pressure and volume of an ideal gas at constant temperature?
- Boyle's Law (Correct answer)
- Charles's Law
- Gay-Lussac's Law
- Dalton's Law
Correct answer: Boyle's Law
Boyle's Law states that for a fixed amount of ideal gas at constant temperature, pressure and volume are inversely proportional (PV = constant).
Question 4: What is 'fatigue failure' in mechanical engineering?
- Fracture caused by repeated cyclic loading at stresses below the static yield strength (Correct answer)
- Sudden brittle fracture due to single overload
- Gradual corrosion weakening a component over time
- Deformation caused by sustained high-temperature loading
Correct answer: Fracture caused by repeated cyclic loading at stresses below the static yield strength
Fatigue failure occurs when a material fractures after repeated cyclic stress applications, even at stress levels well below its static yield strength, due to crack initiation and propagation.
Question 5: Which theorem in static analysis states that the sum of moments about any point equals zero for a body in equilibrium?
- Principle of moments (rotational equilibrium) (Correct answer)
- Theorem of virtual work
- Castigliano's theorem
- Superposition principle
Correct answer: Principle of moments (rotational equilibrium)
The principle of rotational equilibrium states that for a stationary rigid body, the sum of all torques about any arbitrary point must equal zero.
Question 6: In control systems, what does PID stand for?
- Proportional-Integral-Derivative (Correct answer)
- Power-Input-Distribution
- Phase-Induced Damping
- Pressure-Inertia-Displacement
Correct answer: Proportional-Integral-Derivative
PID control combines proportional (present error), integral (accumulated past error), and derivative (predicted future error) terms to minimize steady-state error and improve system response.
MS MS in Mechanical Engineering 2
In materials science, what is the 'yield strength' of a material?