Effect of test speed on verification of material testing machine Bulent Aydemir, Sinan Fank * , Baris Cal TUBITAK, Ulusal Metroloji Enstitusu (UME), Gebze, Kocaeli 41470, Turkey Received 6 June 2005; received in revised form 16 May 2006; accepted 18 May 2006 Available online 2 June 2006 Abstract 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 obtain- ing 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 contin- uously 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 verifica- tion results. In this study these results are discussed and the findings are presented. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Material testing machine; Verification; Effect of test speed 1. Introduction Most verification of material testing machines in the European Community are carried out in accor- dance with EN 10002-2 or EN ISO 7500-1 standards [1,2]. A constant test speed is necessary for satisfac- tory results. According to the standards, all verifica- tions 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 spec- ified in the standards. If the machine is capable of holding the selected force in a quasi-static state, then selected loads can be applied step by step dur- ing verification, some material testing machines are not capable of holding quasi-static force, which causes error due to the difficulty of obtaining data at the correct moment. Sometimes, the machine can- not properly adjust to the slow test speed; in which case results are unreliable. In this study, a computer controlled material testing machine with a 250 kN capacity was verified at different crosshead speeds. Three different class 0263-2241/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.measurement.2006.05.011 * Corresponding author. Tel.: +90 262 679 50 00; fax: +90 262 679 50 01. E-mail address: sinan.fank@ume.tubitak.gov.tr (S. Fank). Measurement 40 (2007) 343–346 www.elsevier.com/locate/measurement