<title>Thermal expansion measurement of gauge blocks</title>

Abstract

An instrument for the measurement of the thermal expansion coefficient near room temperature of gauge blocks and other samples of similar shape and size has been developed. The length dilatation is measured by a differential plane mirror interferometer. A special interference phase detection technique compensates for non-linearity errors caused by polarization mixing. In combination with an electronic phase meter this allows to achieve nanometer accuracy. Since the measurements are done in vacuum, no compensation for the refractive index of air has to be made. For samples with good thermal conductivity the slow heat exchange by thermal radiation allows for a small temperature gradient of the sample and a good stability in the thermal equilibrium. From the thermal expansion curve, measured in a temperature range typically between 10 °C and 30 °C, the linear and quadratic expansion coefficients are evaluated at 20°C, the reference temperature for length. It is shown, that for the investigated gauge block materials the room temperature expansion can be very accurately described with two coefficients within a few parts in iO per degree. A detailed analysis of the measurement uncertainty demonstrates the capability of the measurement instrument, which is continued by the results of an international comparison.

Ultra-precise thermal expansion measurements of ceramic and steel gauge blocks with an interferometric dilatometer

“…That the LTECs for the gauges A1 to A4 (2 % Al 2 O 3 PSZ) are lower than those for gauges B1 to B3 ("pure" PSZ), is quite reasonable, because the LTEC of the added Al 2 O 3 is much less than that of PSZ, which is reported to be 5.30 10 -6 K -1 at 20 C [12]. We calculated the LTEC for 2 % Al 2 O 3 PSZ using Turner's equation [14]: (4) where , , and represent, respectively, LTEC, weight proportion, bulk modulus, and density. The subscripts 1 and 2 represent the two components, i.e.…”

“…Knowledge of the linear thermal expansion coefficient (LTEC) is essential in order to correct the absolute length of gauge blocks, and to compare dimensional measurements at different reference temperatures. Several papers have been published relating to thermal expansion measurements of gauge blocks [1][2][3][4], and to international comparisons of short and long gaugeblock measurements among the national measurement institutes of EUROMET [5,6].…”

Experimental Evaluation of Coefficient of Thermal Expansion of Carbon Fiber Reinforced Polymer Tube

“…Thus given two measurements of the linear dimension of a sample, L 1 and L 2 made at temperature T 1 and T 2 the mean CTE over the temperature range T 2 -T 1 is given by [2] where L = length of sample at given reference temperature ΔT = change in temperature of sample ΔL = change in length of sample corresponding to change in temperature According to international standard ISO all the measurements are to be performed considering 20°C as reference temperature. This means that for all precise dimensional measurements, correction are to be applied, if the measurements are not carried out at 20°C, taking into account the thermal expansion coefficient of work piece to be measured [3]. For applications such as space borne payload structure, composite materials are used to achieve thermally stable structure with minimum weight.…”