Calculate Force for Beam Shear Failure

In summary, the speaker has recently started a new job and is seeking help in calculating the force that caused a shear failure in a 303 stainless steel component. The component was a 1/2" tall tooth with a cross section area of .125". The temperature at the time of failure was below freezing and the component was from an ice maker. The suggested approach is to use the formula for shear stress = force/area to calculate a coarse failure load, but it may only give an upper bound due to the complexity of forces on gear teeth. The speaker also asks for a description of the fracture surface, which was found to be both crystalline and dull, indicating both brittle and ductile failure. The part had been in use for
  • #1
Hockeyguy2026
3
0
I started a new job two weeks ago and I've been out of school for twenty years and have not used strength of materials knowlegde since. I had a part fail in the lab and I would like to calculate the force that would have been necessary to cause the shear failure. I have simplified the problem to a 1/2" tall tooth with a cross section area of .125". The material is 303 stainless steel. Can anyone help me with the equation to find this force. I understand that the part failure was caused by repeative stress and not a blunt force but my first step is to find that blunt force value.
 
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  • #2
What temperature was the component running at at failure?
 
  • #3
The temperature was below freezing - approx. -5C. The failed compent was from an ice maker.
 
  • #4
OK so standard quoted materials properties would apply.

Shear stress = Force/area

So you can calculate a coarse failure load by multiplying the shear stength of your steel by the 1/8 sq inch.

However the forces on gear teeth are much more complex so this will only give you an upper bound. There are significant stress concentrations depending upon the shape of the teeth.

Also, what did the fracture surface look like? Can you describe it?
Was it crystalline and shiny or dull and smooth? or was it part crystalline and part dull?
 
  • #5
The failure looks part crystalline and part dull. The part that broke off is a stream divider that changes the flow of ice from an evaporator to a nozzle that pushes the ice through a tube. The part failed after many months of 24/7 operation.
 
  • #6
The crystalline part is brittle failure, the dull part ductile failure.
 

1. What is beam shear failure and why is it important?

Beam shear failure is a type of structural failure that occurs when the shear force on a beam exceeds its capacity to resist it. This can lead to the beam breaking or collapsing, which can have serious consequences for the stability and safety of a structure. It is important to calculate the force for beam shear failure to ensure that beams are designed and constructed to withstand the expected loads and prevent catastrophic failures.

2. How do you calculate the force for beam shear failure?

The force for beam shear failure can be calculated using the formula F = VQ/It, where F is the maximum shear force, V is the shear force at a given point, Q is the first moment of area of the cross section about the neutral axis, I is the moment of inertia of the cross section, and t is the depth of the beam at the point of interest.

3. What factors can affect the force for beam shear failure?

Several factors can affect the force for beam shear failure, including the type and properties of the material used, the dimensions and shape of the beam, the support conditions, and the applied loads. It is important to consider all of these factors when calculating the force for beam shear failure to ensure accurate and safe results.

4. How can the force for beam shear failure be prevented?

The force for beam shear failure can be prevented by designing and constructing beams that can withstand the expected shear forces, such as using appropriate materials and dimensions, providing adequate support and bracing, and ensuring that the applied loads are within the beam's capacity. Regular inspections and maintenance of structures can also help to prevent shear failures.

5. Are there any limitations to calculating the force for beam shear failure?

Yes, there are some limitations to calculating the force for beam shear failure. The formula used assumes that the material is homogenous and isotropic, and that the beam is loaded in a linear and elastic manner. It also does not take into account any potential damage or defects in the beam, which could affect its strength. Therefore, it is important to use conservative estimates and consider other factors when calculating the force for beam shear failure.

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