Bending (flexural) stress

Category: Strength of Materials & Mechanics
Formula

σ = M · c / I

Input parameters

Result
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Example

Practical Example:

A simply supported steel beam section experiences a maximum bending moment of 5 kN·m at midspan.
The section’s extreme fiber distance from neutral axis is 0.05 m (50 mm).
The section modulus is given via the second moment I = 8.33×10⁻⁵ m⁴.

Calculation:
M = 5 kN·m = 5,000 N·m
c = 0.05 m
I = 8.33×10⁻⁵ m⁴

σ = M·c / I = 5,000 * 0.05 / 8.33e-5 = 3,000,300 Pa ≈ 3.000 MPa

FAQ

What is bending stress?
Bending (flexural) stress occurs in beams subjected to bending moments and is calculated with σ = M·c / I.
What units are used for I?
Moment of inertia (I) is commonly expressed in mm⁴, cm⁴, m⁴ or in⁴. Ensure unit consistency when calculating.
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