Preload (engineering)

A preload is a test segment where the crosshead moves to load the specimen to a specified value before a test starts. Data is not captured during the preload segment. When tensile specimens are initially placed into testing grips, they can be subjected to small compressive forces. These forces can cause specimens to bend imperceptibly, causing inaccurate and inconsistent results. Establishing a small preload as a part of the test method eliminates those compressive forces on specimens and improves the repeatability of results.