Free Master of Engineering Machine Design Questions and Answers — Questions and Answers

Question 1: Which of the following, when applied to power screws, is the right formula to calculate torque when the load is reduced during machine design? (W=weight in N, =angle of inclination, =angle of friction)

W tan (θ – ϕ) (Correct answer)
W tan (θ + ϕ)
W tan (θ x ϕ)
W tan (θ / ϕ)

Correct answer: W tan (θ – ϕ)

In machine design, when a power screw is used to lower a load, the torque required to overcome friction and the load itself is calculated using the formula W tan (θ – ϕ). Here, W is the load, θ is the helix angle of the screw, and ϕ is the friction angle, representing the resistance encountered during the lowering motion.

Question 2: Which of the following represents a screw in dominance?

Mechanical advantage is lowered
High efficiency
Large load carrying capacity (Correct answer)
Wear of screw is reduced

Correct answer: Large load carrying capacity

Power screws are mechanical devices specifically designed to convert rotational motion into linear motion, and their primary advantage, or 'dominance,' lies in their ability to handle and sustain very large axial loads. This characteristic makes them ideal for applications requiring significant force transmission, such as jacks and presses.

Question 3: According to ASME code, what is the maximum shear stress for a material with keyway effect and ultimate tensile strength (Sut)?

0.225 Sut
0.18 Sut
0.135 Sut (Correct answer)
0.30 Sut

Correct answer: 0.135 Sut

According to the ASME code for shaft design, the maximum permissible shear stress for a material with a keyway effect is reduced to account for the stress concentration caused by the keyway. This reduction is typically specified as 0.135 times the ultimate tensile strength (Sut) of the material, reflecting the weakening effect of the keyway on the shaft's strength.

Question 4: Which of the following components only experiences the bending moment when transferring torque?

Belt drive
Axle (Correct answer)
Clutch
Brake

Correct answer: Axle

An axle is a shaft that supports a transverse load (like the weight of a vehicle or machine component) while also transmitting torque. The transverse load inherently creates bending moments along the axle's length. Therefore, an axle experiences both bending moment due to the supported load and torsional stress from the transmitted torque, making bending a primary stress when transferring torque.

Question 5: Which one of the following connects two rotating shafts?

Belt drive
Key
Coupling (Correct answer)
Gear

Correct answer: Coupling

A coupling is a mechanical device specifically designed to connect two rotating shafts, allowing for the transmission of power and torque between them. Couplings can be rigid or flexible, depending on the need to accommodate misalignment between the shafts. Other options like belt drives and gears transmit power between shafts but do so indirectly, while a key is used to secure components *to* a shaft, not connect two shafts directly.

Question 6: Which of the ensuing lines is the most cost-effective?

Lagrange line
Gerber parabola
Goodman line
Soderberg line (Correct answer)

Correct answer: Soderberg line

The Soderberg line is the most conservative fatigue failure criterion among the options, as it uses the yield strength for the mean stress component. While this leads to designs with larger safety factors and potentially more material, its high reliability minimizes the risk of costly failures during operation. In critical applications where failure consequences are severe, this robust design approach can be considered cost-effective by preventing expensive repairs, downtime, or liability issues in the long run.

Question 7: Which of the following expressions is incorrect for rigidity-based shaft design?

L = GθT / J (Correct answer)
T = GθJ / L
J = TL / Gθ
θ = TL / GJ

Correct answer: L = GθT / J

The fundamental equation for torsional rigidity is T/J = Gθ/L, where T is torque, J is the polar moment of inertia, G is the shear modulus, θ is the angle of twist, and L is the length of the shaft. Rearranging this equation to solve for L gives L = GθJ / T. The expression L = GθT / J incorrectly swaps the torque (T) and polar moment of inertia (J) in the numerator and denominator, making it mathematically incorrect.

Question 8: What sort of welding in machine design use an oxygen-acetylene gas?

Forge welding
Thermit welding
Electric arc welding
Gas welding (Correct answer)

Correct answer: Gas welding

Gas welding, specifically oxy-acetylene welding, utilizes a flame produced by burning a mixture of oxygen and acetylene gases. This high-temperature flame melts the edges of the metals to be joined, often with the addition of a filler metal. Other welding methods like forge, thermit, and electric arc welding use different heat sources and processes.

Question 9: Which of the subsequent is not a transmission shaft type?

Line shaft
Transmission shaft (Correct answer)
Countershaft
Crankshaft

Correct answer: Transmission shaft

A 'transmission shaft' is a general term for any shaft used to transmit power. Line shafts, countershafts, and crankshafts are all specific *types* or classifications of transmission shafts, each with a distinct function or arrangement within a machine. Therefore, 'transmission shaft' itself is the overarching category, not a distinct type alongside the others.

Question 10: Which of the following is false regarding stiff and flexible connections in machine design?

Rigid couplings cannot tolerate slight misalignment between axes of shafts
Flexible couplings can absorb shocks and vibrations
Flexible couplings can tolerate any slight misalignment between axes of shafts
Rigid couplings are expensive than flexible couplings (Correct answer)

Correct answer: Rigid couplings are expensive than flexible couplings

Rigid couplings are generally simpler in construction and design, consisting of solid components that rigidly connect shafts. In contrast, flexible couplings incorporate elements (like elastomers, gears, or chains) designed to accommodate misalignment and absorb shocks, making them more complex and typically more expensive to manufacture. Therefore, the statement that rigid couplings are more expensive than flexible couplings is false.

Question 11: Which of the following failure types cannot occur in a riveted joint?

Shear failure of plate (Correct answer)
Crushing failure of the plate
Shear failure of rivet
Tensile failure of the plate between rivets

Correct answer: Shear failure of plate

In a riveted joint, the primary failure modes for the plate material are tensile failure (tearing of the plate between rivets) and crushing failure (bearing stress at the rivet hole). The rivets themselves are prone to shear failure. While the plate can tear, it does not typically fail by 'shear failure of the plate' in the same manner as a rivet, which undergoes direct shear across its cross-section.

Question 12: Which of the following statements regarding roller bearings and ball bearings is correct?

They have point contact
Radial dimensions are more
Axial dimensions are less
Power lost in friction is more (Correct answer)

Correct answer: Power lost in friction is more

Roller bearings, due to their line contact (compared to the point contact of ball bearings), generally have a larger contact area under load. This larger contact area, along with increased sliding friction and hysteresis losses, typically results in higher power loss due to friction compared to ball bearings, especially under heavy loads. While roller bearings offer higher load capacity, this often comes with increased frictional losses.

Question 13: Which of the following is an accurate representation of a fillet joint?

A triangle
A triangle with an arc above it
Two parallel lines with an arc above them
A right angled triangle (Correct answer)

Correct answer: A right angled triangle

A fillet weld, when viewed in cross-section, is conventionally represented as a right-angled triangle. The two perpendicular sides of the triangle lie along the surfaces of the parts being joined, and the hypotenuse forms the exposed face of the weld. This geometric representation is standard for design calculations and engineering drawings.

Question 14: What kind of welding joint is the one in the list below not one?

Single strap joint (Correct answer)
Lap joint
Butt joint
Tee joint

Correct answer: Single strap joint

Lap joints, butt joints, and tee joints are fundamental classifications of welding joints, describing the relative positioning of the parts being welded. A 'single strap joint,' however, is a term primarily associated with *riveted* or *bolted* connections, where a single plate (strap) is used to connect two main plates. It is not a standard type of welding joint geometry.

Question 15: Which of the following is a multi-leaf spring's rebound clips used for?

Attach a member or component to
Helps to share the load from master leaf to graduated leaves (Correct answer)
Hold all the leaves of the spring
Engage the bolts to clamp the leaves

Correct answer: Helps to share the load from master leaf to graduated leaves

Rebound clips in a multi-leaf spring serve to hold the individual leaves together, preventing them from separating during the rebound phase of spring action. More importantly, they help distribute the load more evenly among the graduated leaves, ensuring that the entire spring assembly works cohesively. This load sharing prevents individual leaves from being overstressed and contributes to the spring's overall durability and performance.

Question 16: What form of lever has the effort situated between the load and fulcrum?

Fourth type
First type
Second type
Third type (Correct answer)

Correct answer: Third type

In a third-class lever, the effort force is applied between the fulcrum (pivot point) and the load. Examples include tweezers, fishing rods, and the human forearm when lifting an object. This arrangement typically results in a mechanical disadvantage in terms of force but allows for greater range of motion and speed at the load end.

Free Master of Engineering Machine Design Questions and Answers

Which of the following, when applied to power screws, is the right formula to calculate torque when the load is reduced during machine design? (W=weight in N, =angle of inclination, =angle of friction)