Is Section Modulus the same as a cross sections bending strength modulus ?

In summary, the conversation is discussing the properties of a "Rear underun protection device" for a lorry, specifically the requirement for a steel beam with a bending strength modulus of at least 20cm^3. The question arises whether this is referring to the section modulus or a different entity. The conversation also touches on the units and definitions of flexural modulus and flexural rigidity.
  • #1
Mech King
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Is "Section Modulus" the same as a cross sections "bending strength modulus"?

Good afternoon everyone,

I am following an ECE directive that sets out the requirements for the properties of a "Rear underun protection device" for the rear of a lorry.

It states that the underun bar must consist of a "steel beam whos cross-section has a bending strength modulus of at least 20cm^3"

Are they referring to the "Section modulus"? or is what they are stating a completely differnt entity.

Trying to find the appropriate person to speak to for this directive is proving abit of a nightmare, oh the joys of bureaucracy eh!

What are your thoughts?

Mech King
 
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  • #2


From the looks of the information given, I would say it is indeed the section modulus because the unit is volume.

I believe bending strength modulus is the same as flexural modulus defined as:

EI or N/m^2 * m ^4 = N*m^2

Please correct me if i am wrong, but this is my take on this.
 
  • #3
Nick Bruno: No, flexural modulus of elasticity has units of Pa (pascals), as does tensile modulus of elasticity. And E*I, which has units of N*m^2, is called flexural rigidity, not the names you listed.

Mech King: I agree that "bending strength modulus" in your above post is elastic section modulus.
 
  • #4


Thanks for your replies chaps,

much appreciated.

Cheers
 

What is Section Modulus?

Section Modulus is a geometric property of a cross section that represents the resistance to bending of a specific material. It is calculated by dividing the moment of inertia of a cross section by the distance from the neutral axis to the outermost fibers of the section.

What is Cross Section Bending Strength Modulus?

Cross Section Bending Strength Modulus, also known as flexural modulus, is a measure of a material's ability to resist bending. It is calculated by dividing the maximum bending stress by the strain in the outermost fibers of a material's cross section.

Are Section Modulus and Cross Section Bending Strength Modulus the same thing?

No, Section Modulus and Cross Section Bending Strength Modulus are not the same thing. While both are measures of a material's resistance to bending, they are calculated using different properties and have different units of measurement.

How are Section Modulus and Cross Section Bending Strength Modulus related?

Section Modulus and Cross Section Bending Strength Modulus are related in that they both provide information about a material's ability to resist bending. However, they are not interchangeable and should not be used interchangeably in calculations or design.

Why is it important to understand the difference between Section Modulus and Cross Section Bending Strength Modulus?

It is important to understand the difference between Section Modulus and Cross Section Bending Strength Modulus in order to accurately analyze and design structures. Using the wrong value can lead to incorrect assumptions about a material's strength and potentially result in unsafe or inefficient designs.

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