In a beam subjected to pure bending, the direct stress at any point within the elastic limit is directly proportional to:

Explanation:

Direct Stress in a Beam Subjected to Pure Bending

In the case of a beam subjected to pure bending, the direct stress (also known as bending stress) at any point within the elastic limit is directly proportional to the distance of that point from the neutral axis. This follows from the bending equation:

Analyzing the Given Options

1. "The moment of inertia of the beam section." (Incorrect)

   • The moment of inertia affects the beam's resistance to bending, but the direct stress at a point is not directly proportional to it.

2. "The total applied load on the beam." (Incorrect)

   • The total applied load influences the bending moment but does not directly relate to the stress at a specific point.

3. "The cross-sectional area of the beam." (Incorrect)

   • The cross-sectional area affects the overall bending resistance but not the direct stress at a point.

4. "The distance of the point from the neutral axis." (Correct)

   • According to the bending equation, σ = My/I, where σ is the direct (bending) stress, M is the moment, y is the distance from the neutral axis, and I is the moment of inertia.

   • This means the direct stress is directly proportional to the distance from the neutral axis (y).