Problem 2: True or False (20%)
1. ( ) For the temperature factor ($k_a$): When the operating
temperature is high room temperature, the yield strength increases
and the material becomes more ductile.
2. () Could not compute the fatigue strength ($S_f$) in the S/N diagram
with low cycle ($1 \leq N \leq 10^3$)
3. () The rotating beam endurance limit is lower than the actual
endurance limit.
4. () Under fatigue loading conditions, the presence of stress
concentration increases the fatigue life of an element.
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5. () Related to fatigue criteria for fluctuating stress, there are five
different theories to predict failure.
6. () When a machine element is subjected to general fluctuating
stress ($\sigma_m \neq 0$), the endurance limit is obtained from the
rotating-beam test (after applying the necessary modifying factors).
7. () Related to S/N diagram, at N<$10^6$ cycles, fatigue strength is
equal to endurance limit.
8. () The mean, or midrange, stress is the average of the maximum
and the minimum stress in a cycle.
9. () When the notch sensitivity is smaller, the $K_r$ is closer to $K_t$?
10.() The S-N diagram obtained from the R. R. Moore high-speed
rotating-beam machine can be applied or used for any type of
variable loading.
