__Preload Torque Calculator:__

__Preload Torque Calculator:__

Enter the values of percentage of yield strength desired, yp (%),the yield strength of the bolt material, S_{(psi)}, the nominal diameter of the bolt, d_{(in)} and the tensile stress area of the bolt, A (in²) to determine the value of Preload torque, T_{pl(in-lb)}.

__Preload Torque Formula:__

__Preload Torque Formula:__

Preload torque is a critical concept in bolted joint assembly, referring to the torque required to stretch the bolt to a specific tension before the joint members begin to separate or move. This tension ensures the joint is secure and can handle the applied loads without loosening.

Preload torque, T_{pl(in-lb)}, is calculated by multiplying the yield strength of the bolt material, S_{(psi)} in per square inch, by the tensile stress area of the bolt, A (in²) in inches per square, and by the percentage of yield strength desired, yp (%), divided by 100. This product is then multiplied by the nominal diameter of the bolt, d_{(in)} in inches, and divided by 12 to convert the torque into inch-pounds (in-lb).

Preload Torque, T_{pl(in-lb)} = ( (yp/100) * S_{(psi)} * A _{(in²) }* d_{(in)} / 12

T_{pl(in-lb) }= Preload torque in pound inches, in-lb.

yp = percentage of yield strength desired, (%).

S_{(psi) }= yield strength of the bolt material in per square in inches, psi.

A _{(in²)} = tensile stress area of the bolt in inches per square, in^{2}.

d_{(in)} = nominal diameter of the bolt in inches, in.

__Preload Torque Calculation:__

__Preload Torque Calculation:__

- A structural bolt with a tensile stress area of 0.20 in² and a nominal diameter of 1/2 inch is to be tightened to 70% of its 120,000 psi yield strength. Calculate the preload torque.

Given: yp = 70, S_{(psi)} = 120,000psi, A _{(in²)} _{ }= 0.20in², d_{(in)} = 0.5in.

Preload Torque, T_{pl(in-lb)} = (yp/100) * S_{(psi)} * A _{(in²)} * d_{(in)} / 12

T_{pl(in-lb)} = (70/100 * 120,000 * 0.20) * 0.5 / 12

T_{pl(in-lb)} = (84,000 * 0.20) * 0.5 / 12

T_{pl(in-lb)} = 8400in-lb.

- Assume we aim to achieve a preload torque, T
_{pl(in-lb)}of 700 in-lb, with a desired percentage yp is 75% of the bolt’s yield strength, a tensile stress area, A_{(in²)}is 0.20in^{2}, and a nominal diameter d_{(in)}is 0.5inches.

Given: yp = 75, T_{pl(in-lb)} = 700in-lb, A _{(in²)} = 0.20in², d_{(in)} = 0.5in.

Preload Torque, T_{pl(in-lb)} = ( (yp/100) * S_{(psi)} * A _{(in²)} * d_{(in)} / 12

S_{(psi) }= T_{pl(in-lb)} * 12 * 100 / yp * A _{(in²)} * d_{(in)}

S_{(psi) }= 700 * 12 * 100 / 75 * 0.20 * 0.5

S_{(psi) }= 8400 / 0.15

S_{(psi) }= 56,000psi.

__Pre Load in a Fastener Explained in the Simplest Way Possible:__

__Pre Load in a Fastener Explained in the Simplest Way Possible:__