BME Machine Design 2 — Questions and Answers
Question 1: Which gear type is used to transmit motion between two parallel shafts?
- Bevel gear
- Worm gear
- Helical gear (Correct answer)
- Hypoid gear
Correct answer: Helical gear
Helical gears are commonly used to transmit power between parallel shafts, offering smoother and quieter operation than spur gears.
Question 2: The Hertz contact stress formula is used to analyze failure in:
- Welds
- Rolling element bearings (Correct answer)
- Bolted joints
- Keyways
Correct answer: Rolling element bearings
Hertz contact stress theory is applied to rolling element bearings, gears, and cam-follower systems where curved surfaces make contact.
Question 3: Which spring stores energy through torsion of its wire?
- Leaf spring
- Disc spring
- Helical compression spring (Correct answer)
- Flat spiral spring
Correct answer: Helical compression spring
In a helical compression spring, the coil wire is primarily subjected to torsional stress as the spring deflects axially.
Question 4: Goodman's criterion in fatigue design relates:
- Mean stress and alternating stress to failure (Correct answer)
- Yield strength and ultimate strength only
- Temperature and stress
- Strain and displacement
Correct answer: Mean stress and alternating stress to failure
Goodman's criterion provides a linear relationship between mean stress and alternating stress that defines the boundary between safe and unsafe fatigue conditions.
Question 5: What is the function of a retaining ring (snap ring) in a shaft assembly?
- Transmit torque
- Seal lubricant
- Prevent axial movement of a component (Correct answer)
- Absorb vibration
Correct answer: Prevent axial movement of a component
A retaining ring fits into a groove on a shaft or in a bore to provide a removable shoulder that prevents axial displacement of components.
Question 6: Stress concentration in a machine member is most influenced by:
- Material density
- Geometric discontinuities such as holes and notches (Correct answer)
- Surface color
- Component length
Correct answer: Geometric discontinuities such as holes and notches
Geometric discontinuities like holes, fillets, notches, and keyways cause local stress intensification described by the stress concentration factor Kt.
BME Machine Design 2
Which gear type is used to transmit motion between two parallel shafts?