ME EN 3000 DOME Midterm 2 quiz flashcards

Which Failure mode is more common in practical applications?

Fatigue Failure

When is the Fatigue Strength corresponding to the knee (or 10^6 cycles) in the SN diagram?

Endurance limit (Se)

In fatigue design, how does the size factor ​ generally change as the diameter of a round bar increases?

It decreases

By multiplying the endurance limit correction factors ka kb kc, the resulting Se should ultimately be higher than Se’

False

Which theory provides the most conservative approach?

soderberg

In fatigue failure analysis, why do we use equivalent fully reversed stress σ_rev for fluctuating stress condition (σ_m≠0_, σ_a≠0) ?

Converts fluctuating loading to an equivalent fully reversed form to use S=aNb

A solid circular shaft is subjected to a bending moment that varies sinusoidally between +120 MPa and –40 MPa, and a steady torsional shear stress of 50 MPa.

You are asked to evaluate fatigue failure using the Modified Goodman criterion.

Which stress combination should be used?

Use Von Mises equivalent alternating and midrange stresses

For the same weight of material, a hollow shaft always has a larger polar moment of inertia, leading to lower shear stress and smaller twist under the same torque, and thus better strength-to-weight efficiency.

True

In the calculation of the modified endurance limit (Se) for a hollow shaft, the size factor (kb) is determined based on the outer diameter (do), as fatigue failure is most likely to initiate at the outer surface. 

True

Choose the correct loading factor, k_c, when calculating Se if a shaft is rotating and subjected to both constant force F and constant torque, T.

kc=1