Bending stress can be understood as the measure of internal pressure within a material that resists any change in shape when a bending moment is applied. The strength and response of a material to bending stress can provide essential information about how it may behave in actual structures. In mechanical engineering, knowledge of bending stress is necessary for the design of mechanical elements subjected to bending moments such as shafts, gears, and pulleys.
Motivation phase
What do you see?
The photo shows a bookshelf. Why do you think the shelf cracked? Were the books too heavy for that shelf? What stress caused the shelf to crack? The shelf cracked due to bending.
The photo is from https://www.istockphoto.com/photo/the-bent-shelf-with-old-dampened-books-gm665496540-121240359.
Information phase
Bending in a console
Consider a steel rod fixed at one end, with a weight hanging on the other end. The rod will bend due to the weight, resulting in distribution of bending stress across its cross-section. In mechanical engineering this would be bending in a console.
Information phase
Bending in a beam
In pure bending, there is a neutral axis. The length of the neutral axis does not change when the beam is bent. Fibers above the neutral axis shorten while fibers below the axis lengthen.
The upper part of the beam is loaded by compression and the lower part by tension. The highest stress occurs in the upper and lower surfaces of the beam.
Consolidation phase
Let's play
Spin the wheel and answer the questions.
Consolidation phase
Video about stress in beams
In this video it is explained bending and shear stresses in beams. A bending moment is the resultant of bending stresses, which are normal stresses acting perpendicular to the beam cross-section. Watch the video for a better understanding of bending stress.
