# Crushing Area Of Pin

1. Jul 14, 2013

### jayanth nivas

Hi all,
I today learnt that for pin design there is a parameter called,crushing stress,where the pulling force of the fork is divided over projected area,I learnt that projected area was d*t where d was the diameter of the pin and t was the contact length between pin and the fork being pulled.Can any one explain me how the area was derived,it seems i cannot understand why curved surface area of the cylinder cannot be taken for it.Or the difference between CSA and projected area of cylinder.

Sorry if I have misstated something and thanks in advance

2. Jul 14, 2013

### 256bits

Hello jayanth
Crushing stress or bearing stress uses projected area.
You have a round pin in a same size round hole. The force pulling the fork(yoke) and rod apart acts in one direction. The projected area is what the hole and pin 'see' of each other in holding the force. Definitely one obtains a nominal stress acting over the profected area, whereas in fact the first contact may be between the pin and hole some where in line with the direction of force.

If it was a square pin in a square hole does that make it easier to grasp.

It definitely is not the CSA minus the projected area.

3. Jul 14, 2013

### jayanth nivas

I did not mean the algebric difference between CSA and projected area,I wanted to know why conceptual difference between both.If Projected area is d*t and there is clearance between the hole in the fork and pin (Which there should be),the contact will take place only over some arc length.My question is instead of considering the arc length,why do we consider the entire diameter of pin.

Also can someone provide mathematical proof for projected area ?

I'm sorry to ask the same question again and again.I cannot find any material on internet for this.So,if anyone could point me some source I would be much obliged.