A pneumatic torque wrench is used to tighten 3/4-10 UNC bolts in an automobile assembly plant. A torque of 55 ft·lb is generated by the wrench. If the torque coefficient is 0.2, determine the tensile stress in the bolt in PSI.

13173.653 lb/in²

Explanation:

So, without mincing words let us dive straight into the solution to this problem/question. Also, we are given parameters which are going to be useful while solving this problem;

=> The kind of bolt given in the question is 3/4-10 UNC bolts which is 0.75 inches.

=> The torque generated by the wrench is equal to = 55 ft·lb which is also equal to 660 inc.lb when converted to inch pound.

=> The torque coefficient is given as 0.2.

The formula for tensile stress in the bolt = force/ area. So, the first thing to do is to determine the value for the force and secondly, determine the value of the area, then divide to find the tensile stress in the bolt.

Thus, Force = torque generated/ torque coefficient × bolt size= 660/ 0.2 × 0.75 = 4,400 lb.

The area = π/4 [ 0.75 - 0.9743/10]² = 0.334 in².

Therefore, the tensile stress = 4400/0.334 = 13173.653 lb/in²