Temperature Rise of Foil Strain Gages on Plastics

Abstract

In stain measurements of plastics using foil strain gages, the temperature rise caused by power dissipated in the gage produces serious errors. A simple model for estimating the temperature rise is proposed, that is, a single strip representing a grid is bounded onto a half space made of plastic, and generates constant heat flux. A formula and diagram, by which the maximum value of the temperature rise can be estimated, are presented in this paper. The estimated temperature rise, T_max, is about 2 times as large as the measured one for actual gages bounded onto acrylic plates. The difference between both values is due to the incompleteness of the gage model and errors in the temperature measurement using a thermocouple. In spite of this incompleteness, the value of T_max can still be used to estimate the temperature rise of the actual gages. This value is more useful than the power density which is often used as a parameter for estimating the temperature rise.