Skew bending in a circular cross section (proof)

In summary, the conversation discusses the proof of stress generated in a circular cross section due to skew bending. The principle of superposition says that forces and displacement can be simply added when applied to the tube. Additionally, the bending stress at any point is calculated using the formula Mf*r/I, with the maximum stress occurring at the edge of the circle. There is no need to break up the moment into components due to the symmetry of the circle. The conversation ends with gratitude for the information provided.
  • #1
Amaelle
310
54
Good day all
I'm looking for the proof of stress generated in case of skew bending applied in acircular cross section ( I browsed internet the whole day without finding anything convincing)
circular.png


we use
formula1.png

with
formula 2.png

many thanks in advance!
 

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  • #2
The principle of superposition says that forces due to torsion and forces due to bending of the tube should be simply added. The same goes for displacement. When many forces are applied, the order of summation of all forces is not important.
 
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  • #3
No need to break up the moment into its components, because the circle is symmetrical about all axes, and I is the same no matter which axis is chosen. Thus, bending stress at any point is Mf*r/I, where r is the perpendicular distance from the chosen point to the neutral axis, and if the radius of the section is R, then max stress is Mf*R/I, which occurs at the point on the edge of the circle which is a distance R measured perpendicular to the neutral axis.
 
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Likes Amaelle
  • #4
Thanks a lot to both of you!
 

What is skew bending in a circular cross section?

Skew bending in a circular cross section refers to the deformation of a circular cross section when subjected to a bending moment that is not perpendicular to its axis. It is also known as transverse bending.

How does skew bending affect the strength of a circular cross section?

Skew bending causes non-uniform stress distribution along the cross section, resulting in reduced strength compared to pure bending. This is because the material experiences both bending and shear stresses.

What is the formula for calculating the maximum bending stress in a circular cross section under skew bending?

The formula for calculating the maximum bending stress in a circular cross section under skew bending is given by sigma = (M * r) / (I * z), where sigma is the maximum bending stress, M is the bending moment, r is the radius of the cross section, I is the moment of inertia, and z is the distance from the neutral axis to the point of interest.

How can we prove that a circular cross section can resist skew bending?

To prove that a circular cross section can resist skew bending, we can use the principle of superposition and break down the applied bending moment into its components along the x and y axes. Then, we can calculate the bending stresses along both axes and combine them using the Von Mises criterion to determine the maximum stress. If this stress is within the yield strength of the material, the cross section can resist skew bending.

What are some practical applications of skew bending in engineering?

Skew bending is commonly encountered in engineering applications such as the design of curved beams, pipes, arches, and curved roof trusses. It is also important in the analysis of structures subjected to wind or seismic loads, where the bending moments may not be perpendicular to the structural elements.

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