Why do I have a bending moment and an axial displacement here?

In summary: Since the force is applied asymmetrically, the resulting moment is also asymmetric. From the sketch, it seems that the bending moment is larger at Point A than at Point B.In summary, the book states that there should be a bending moment instead of a bending force when a force is applied asymmetrically. However, the equation provided does not seem to support this claim. There is a difference in the magnitude of the bending moment at Points A and B, which suggests that the force may in fact be bending the object.
  • #1
Mech_LS24
148
16
Homework Statement
I have a flexure where a asymmetrically force is applied. Why do I have a bending moment + a axial force displacement instead of a bending force?
Relevant Equations
F*l^3/3*E*I
(F*L)/E*A
Hello,

I have an flexure where the force is applied asymmetrical, I just can't visualize why their should be a bending moment instead of an bending force? How can I distinguish those? Thanks!
IMG_20220228_163534__01.jpg
 
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  • #2
Mech_LS24 said:
Homework Statement:: I have a flexure where a asymmetrically force is applied. Why do I have a bending moment + a axial force displacement instead of a bending force?
Relevant Equations:: (M*L)/EI
(F*L)/E*A

I just can't visualize why their should be a bending moment instead of an bending force?
Your question is not well defined, for me at least. The moment of any vector is its value acting through a perpendidicular distance (the cross product to be technical).
Your relevant equation are not equations. Perhaps that would be a place to start.
 
  • #3
Sorry for that.

They ask what the deflection is at Point A. I thought their should be axial deflection and a bending force deflection (1 and 2). But the book states that the should be a bending moment instead of a bending force. I have added the equations in the sketch, and here below:
Delta1 = F*L/E*A
Delta2 = F*l^3/3*E*I

IMG_20220228_175039__01.jpg


*I see the one equation in the original post is wrong, I will try to fix that.
 
  • #4
I don’t understand the distinction between bending moment and bending force. A force can result in bending because it has a moment about the centre of the rigid attachment.
 
  • #5
Could you post the original text and diagram?
 
  • #6
Lnewqban said:
Could you post the original text and diagram?
I am afraid not, it's from a document which isn't allowed to be shared.

The only thing here, I can't distinguish bending moment and bending force..
 
  • #7
Mech_LS24 said:
I am afraid not, it's from a document which isn't allowed to be shared.

The only thing here, I can't distinguish bending moment and bending force..
As explained by @haruspex above, there is no moment without a distance and a force.
In this case, the distance of interest seems to be the one separating the neutral fibers from the point of application of the axial force.
 
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FAQ: Why do I have a bending moment and an axial displacement here?

Why do I have a bending moment at this location?

The presence of a bending moment at a certain location is due to the external forces acting on the structure. These external forces cause the structure to bend, resulting in a bending moment.

What factors contribute to the magnitude of the bending moment?

The magnitude of the bending moment is influenced by the type and magnitude of the external forces, the geometry and material properties of the structure, and the location of the point of interest.

How does the axial displacement affect the bending moment?

The axial displacement, or the movement of a structure along its longitudinal axis, can affect the bending moment by changing the distribution of forces within the structure. This can result in a change in the magnitude of the bending moment at a specific location.

Can a structure have both a bending moment and an axial displacement?

Yes, a structure can have both a bending moment and an axial displacement at the same location. This is often the case in real-world structures, where external forces and loads act in multiple directions.

How can I calculate the bending moment and axial displacement at a specific location?

The bending moment and axial displacement can be calculated using structural analysis techniques, such as the moment-area method or the finite element method. These methods involve analyzing the external forces, geometry, and material properties of the structure to determine the bending moment and axial displacement at a specific location.

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