Effect of test speed on verification of material testing machine

摘要

A constant test speed is necessary in order to verify a material testing machine. According to EN 10002-2 or EN ISO 7500-1 standards, all verifications should be carried out by slowly increasing the load. This means that the test speed should be as low as possible, though the exact speed is not specified in the standards. If the machine is capable of holding the selected force in quasi-static conditions, then selected loads are applied step by step during verification. In some cases, the material testing machine is not capable of holding quasi-static force, which causes error due to the difficulty of obtaining data. Sometimes, the machine cannot adjust to the slow test speed, in which case the results are unreliable. In this study, measurements were taken with a tension testing machine using class 00 force-proving instruments, which comply with the requirements specified in EN ISO 376 and EN 10002-3. Similar measurements were repeated at different test speeds to compare results and determine the effect of test speed on verification results. At the same time, the accuracies of measurement results obtained by increasing the load step-by-step (with pauses in between the increases) versus continuously at identical test speeds are compared to determine the effect of loading methods. Measurement results show that applying different test speeds and loading conditions during the verification of a material testing machine affects verification results. In this study these results are discussed and the findings are presented.