The yield strength of a steel shaft is twice its endurance limit. Which of the following torque fluctuations represent the most critical situation according to Soderberg criterion?

Fatigue strength of a rod subjected to cyclic axial force is less than that of a rotating beam of the same dimensions subjected to steady lateral force because

In a shaft with a transverse hole, as the hole to the shaft diameter ratio ___________ (increases / decreases), the torsional stress concentration factor__________ (increases/decreases)

The process of shot peening increases the fatigue life of steel springs mainly because it results in