Shear stress in a pinned shaft

[fusername]

So I am trying to figure out this shear stress problem that I have no idea how to approach. I have a shaft which is transmisitting a torque. It can be locked to its housing by using a pin which passes through it radially. I need to know that the shaft won't snap when transmitting its torque when unpinned however, and do not know how to solve this problem. I found the stress concentration factor for such a model, but I don't know what equation to use for max or average shear stress, this is beyond my understanding of stress, and beyond all the texts i have my hands on.

 

[Studiot]

You need to post quite a bit more detail.

Is the shaft solid or hollow?

Does the pin transmit the load?

Is the pin tapered, a cotter or what?

If the pin does not transmit the load, is there a keyway, spline, flat or what?

A simple sketch would help enormously.

 

[fusername]

sorry, been staring at it soo long everything sounds obvious, I am sure you know the feeling.

it is a solid shaft with a hole drilled through it from the side. I am not worried about failure of the pin, but failure of the shaft it passess through when the pin is removed. it is a plain cylinder shaft undergoing pure torsion.

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i can do a picture in a bit if that drawing is not enough. It is a very simple stress concentration problem, but it is one i have never seen before and can't find reference on.

 

[Studiot]

Well I would have hoped a mech engineer? could have provided better information but still, here is the formula you require from my stress conc tables.

You realize that the max shear stress occurs at the outer surface and that your shaft is only at risk if the hole is between the load and the drive?

go well

 

[alphy]

Hello,

Thank you for sharing your question about shear stress in a pinned shaft. I can offer some guidance on how to approach this problem.

Firstly, it is important to understand the concept of shear stress. Shear stress is a type of stress that occurs when two forces act parallel to each other in opposite directions, causing one part of an object to slide against another. In the case of a pinned shaft, shear stress is generated when the torque is transmitted through the shaft, causing it to twist.

In order to determine if the shaft will snap when transmitting torque, we need to calculate the maximum shear stress that the shaft will experience. This can be done by using the formula:

Shear stress = (Torque x distance from center of shaft) / (Polar moment of inertia)

The polar moment of inertia can be calculated using the shaft's diameter and length. Once you have the maximum shear stress value, you can compare it to the material's shear strength to determine if the shaft will fail or not.

As for the stress concentration factor, it is used to account for any irregularities or changes in the shape of the shaft, such as the presence of a pin. This factor is multiplied by the calculated maximum shear stress to get a more accurate value.

I would recommend consulting with a mechanical engineer or referring to a textbook on mechanical engineering to understand the equations and concepts better. I hope this helps in solving your problem. Good luck!