# Bearing stress in Bolts

Consider the arrangement shown below. It consists of a bolt, clevis and plate. Since, the clevis and the plate press against the bolt, the bolt will be acted upon by forces 1,2,3 (as shown).

There is something called as bearing stress which will act on the bolt in this case.

I don't exactly get what is this bearing stress. According to what I know about stress, when a body is acted upon by loads, we consider an area in the body and on this area internal resistive forces are developed to oppose external loads, then we calculate the intensity of these internal resistive forces on that area to determine the stress.

The bearing stress in this bolt correspond to what internal resistive forces?

On which area these internal resistive forces are taken?

I've thought a little about it, and came with this, but not quite sure if this is what is exactly meant by bearing stress. Does the bearing stress correspond to the internal resistive forces shown by red? at the midplane?

• Check out shear pins - often a good example to help understand what happens and why. Commented Oct 5, 2021 at 13:44
• Oh, Alright. I will have a look. Thanks Commented Oct 5, 2021 at 14:19

Bearing stress is essentially the contact pressure between two surfaces (the bolt and the joint in this example).

I find illuminating the following picture that shows the force flow.

figure (source chegg)

how it is transferred though one part of the joint to the bolt and then to the other part of the joint.

The bearing stress in this bolt correspond to what internal resistive forces?

The bearing stress correspond the shear force diagram (Q). They are transverse forces that would cause bending.

On which area these internal resistive forces are taken?

different parts of the bolt experience difference load. for example above (if the system is static), the total force on (2) is equal to the force (1) + force (3). So the force flow (and the stress fields) distribution will look like the following image.

• So, because of the forces 1,2,3 (fig. in the question), bending of the bolt occurs. To oppose this bending internal forces are developed in the bolt. The distribution of these forces is pretty complex, not that uniform I was thinking of. At undergraduate level, bearing stresses are defined as force/ (projected area), which I guess is a sort of approximation. Am I right on this? Commented Oct 5, 2021 at 14:18
• Yes this is in line to what I answered. You filled the gaps a lot better though.... If you don't mind the pun 😀
– NMech
Commented Oct 5, 2021 at 14:35