engleski

A Novel Videoextensometer for Strain Measurement on Tensile Testing Machines

This paper presents a new optical procedure for strain measurement on standard specimens, which avoids systematic errors introduced by the construction of tensile testing machines. The results of measurements conducted solely with tensile testing machine are affected by influence of its mechanical parts. To determine the amount of such errors, behavior of a screw-driven Uniaxial Tensile Testing Machine (UTM) Messphysik BETA 50-5 was measured by means of the optical stereophotogrammetric method. A videoextensometer system for strain measurement on tensile testing machines was developed in order to determine actual specimen elongation. The applied method is based on an optical measurement of length deviation of referent distance, which is defined by two optical gauges attached to the specimen surface. Performed experiments confirm a significant influence of the Uniaxial Tensile Testing Machine imperfections on the measured specimen deformation data. The results have shown that e.g. Young modulus obtained from UTM displacements differ from the actual value up to 100%.

videoextensometer; strain; tensile testing; optical method

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