Fatigue strength of a rod subjected to cyclic axial force is less than...
Explanation:
Axial force and lateral force are two types of forces that can be applied to a structural member. When a rod is subjected to cyclic axial force and a rotating beam is subjected to steady lateral force, the fatigue strength of the rod is less than that of the beam.
The reason for this is that at a particular time, the rod has only one type of stress, whereas the beam has both tensile and compressive stresses. This is because of the bending moment induced in the beam due to centrifugal forces.
To explain this in more detail, we can break it down into the following points:
1. Axial stiffness vs bending stiffness: The axial stiffness of a rod is generally less than the bending stiffness of a beam. This means that a rod is more susceptible to buckling under compressive loads than a beam.
2. Centrifugal effects: When a beam rotates, centrifugal forces are induced, which create bending moments. These bending moments induce both tensile and compressive stresses in the beam, making it more resistant to fatigue failure.
3. Discontinuities: The number of discontinuities vulnerable to fatigue failure in a rod is generally more than that in a beam. This is because rods have more stress concentrations due to the abrupt changes in cross-sectional area, such as fillets, threads, and keyways.
4. Types of stress: At a particular time, a rod has only one type of stress, either tensile or compressive. In contrast, a beam has both tensile and compressive stresses induced by the bending moment. This means that a beam is subjected to a wider range of stresses, making it more resistant to fatigue failure.
In conclusion, the reason for the lower fatigue strength of a rod subjected to cyclic axial force compared to a rotating beam subjected to steady lateral force is that the rod has only one type of stress at a particular time, whereas the beam has both tensile and compressive stresses induced by the bending moment.
Fatigue strength of a rod subjected to cyclic axial force is less than...
For fatigue loading normally generated tensile and compressive stresses in the shaft.
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