A Proof Load test is a tensile test performed to a specific load for a specified period of time. Unlike a standard tensile test, the sample is not stressed to the failure point. The proof load test is used to prove the material will support the specified load with an acceptable amount of deflection and/or elongation.

To perform a proof load test, the material is machined into a "dog bone" test specimen. It is then placed into the tensile machine and the specified load is applied for an extended period of time according to the test specifications, usually between one to ten minutes.

The test apparatus measures the elongation and deflection to determine the maximum service load of the material. Proof loads are often used to test the strength of cables and bolts.

Proof Load Testing is done per ASTM A370-10 Mechanical Testing of Steel Products