Master of Engineering Machine Design Flashcards
7 cards from real ME or MEng Master of Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Master of Engineering Machine Design flashcards as text
The Palmgren-Miner rule is used in machine design to:
Answer: Predict cumulative fatigue damage under variable amplitude loading
Miner's rule states failure occurs when Σ(ni/Ni) = 1, summing cycle ratios across all stress levels.
Which snap-ring groove feature most critically affects the fatigue life of a shaft?
Answer: Corner radius at the groove bottom
A sharp corner at the groove bottom is a severe stress concentration that dominates fatigue crack initiation on the shaft.
A spur gear pair has a velocity ratio of 4:1 and a center distance of 250 mm. If the pinion has 20 teeth, the module is:
Answer: 5 mm
Gear has 80 teeth; total teeth on centers: m(N1+N2)/2 = 250 → m×100/2 = 250 → m = 5 mm.
In hydrodynamic journal bearing design, the Sommerfeld number S is used to determine:
Answer: Minimum film thickness, friction, and flow characteristics
The Sommerfeld number S = (r/c)²(μN/P) consolidates design variables and maps to bearing performance parameters via charts.
When a machine component is designed using a safety factor of 2.5 based on yield strength, the design stress is:
Answer: Sy / 2.5
Design (allowable) stress = Sy / n = Sy / 2.5, ensuring the working stress stays well below yielding.
In a leaf spring, adding more leaves (laminations) of the same width and thickness primarily:
Answer: Increases stiffness and load capacity without changing stress
Additional leaves increase the effective second moment of area, raising both stiffness and load capacity while the bending stress formula remains the same.
The critical speed of a rotating shaft is most effectively raised by:
Answer: Shortening the shaft span or increasing shaft diameter
Critical speed ∝ √(EI/m) per unit length; a shorter, stiffer (larger diameter) shaft raises the critical speed.