how to calculate proof load of a bolt

Bolts are one of the universally used fasteners in construction and engineering projects. They are used to keep things together that need to withstand heavy loads, forces, and vibrations. It is vital to make sure that a bolt is capable of handling the load it will be subjected to. Proof load is an essential factor to consider while selecting a bolt for a particular application. In this article, we will discuss how to calculate the proof load of a bolt.

What is proof load?

Proof load is a term used to define the maximum force or stress that a bolt can endure without permanent deformation. It is usually expressed in kN or lb-f. This load is applied to the bolt gradually until it shows evidence of deformation. The yield point is reached when the stress applied has caused significant deformation of the bolt. The proof load indicates the minimum tensile strength of the fastener, a safety factor from the ultimate tensile strength.

Calculating proof load

Calculating the proof load of a bolt involves simple mathematics. The formula is proof load = maximum tensile strength x tensile stress area. The tensile stress area is calculated by finding the the mean of the minimum and the maximum diameter of the threaded portion of the bolt, and then multiplying it by the constant value of 0.7854.

An example of calculating the proof load of a bolt

Suppose you have a bolt with a nominal diameter of 10mm and a maximum tensile strength of 600 N/mm². The tensile stress area can be calculated by finding the mean of the minimum and the maximum diameter - which is (10 9.78) / 2 = 9.89mm. Multiplying this value by the constant value of 0.7854, the tensile stress area is 7.708 square millimeters. Now, the proof load can be calculated using the above formula: proof load = 600 N/mm² x 7.708 = 4,625.6N. Therefore, the proof load of the bolt is 4,625.6N.

Conclusion

In conclusion, calculating the proof load of a bolt is a simple yet crucial step in ensuring that the bolt can withstand the loads that it will be subjected to. Always ensure that the tensile strength and stress area of the bolt are considered to get accurate results. By following the calculations outlined in this article, you can determine the proof load of a bolt and select the appropriate fastener for your application.