Answer:

Introduction:
The fatigue strength of a material is its ability to resist failure under cyclic loading over a period of time. In this question, we are asked to compare the fatigue strength of a rod subjected to cyclic axial force and a rotating beam subjected to steady lateral force.

False:
The statement is false. The fatigue strength of a rotating beam subjected to steady lateral force is less than that of a rod subjected to cyclic axial force.

Explanation:
There are several reasons why a rotating beam subjected to steady lateral force has less fatigue strength than a rod subjected to cyclic axial force:

1. Stress Concentration: A rotating beam has stress concentration at the points where it is fixed to the supports. This stress concentration leads to the initiation and propagation of cracks, which reduces the fatigue strength of the beam.

2. Bending Stress: A rotating beam is subjected to bending stress due to the lateral force. Bending stress causes the formation of microcracks, which can lead to catastrophic failure of the beam.

3. Residual Stress: A rotating beam may have residual stress due to the manufacturing process. This residual stress can lead to premature failure of the beam under cyclic loading.

4. Material Properties: The fatigue strength of a material depends on its properties, such as hardness, toughness, and ductility. The material properties of a rotating beam may be different from those of a rod, which can affect its fatigue strength.

Conclusion:
In conclusion, the statement that the 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 is false. The rotating beam has less fatigue strength due to stress concentration, bending stress, residual stress, and material properties.

False