Question

In bending, the stress is maximum at:

• A. Neutral axis
• B. Outer fibers
• C. Midpoint
• D. At centroid

Hint:

The maximum bending stress occurs at the outer fibers of the beam, where the distance from the neutral axis is greatest. This is a key concept in beam bending.

Answer 1

The Correct Option is B

In bending, stress varies across the cross-section of the beam. The bending stress is given by: \[ \sigma = \frac{M y}{I} \] Where:
- \( M \) is the bending moment,
- \( y \) is the distance from the neutral axis,
- \( I \) is the second moment of area (also called the area moment of inertia).
The neutral axis is the axis where there is no stress; it experiences zero strain because it neither elongates nor shortens during bending. As you move away from the neutral axis, the stress increases. The maximum bending stress occurs at the outermost fibers of the beam, where \( y \) is maximum. Thus, the bending stress is maximum at the outer fibers, and decreases as you move toward the neutral axis.
- The neutral axis has zero stress, as explained above.
- The midpoint is typically at the neutral axis, where the bending stress is zero.
- The centroid is the geometric center of the cross-section, but it does not necessarily coincide with the neutral axis in all cases. The maximum bending stress occurs at the outer fibers, not at the centroid.
Thus, the correct answer is that the maximum bending stress occurs at the outer fibers.