Force calibration of tension meter for measuring static tensions of AGTD parts at temperatures up to 700 °C

Abstract

Strain gauges are used in the measurement of surface parameters of engine parts to evaluate advanced materials and components, including gas turbines, and to provide experimental validation of computational models. To quantitatively determine the mechanical stress, the resistance values of the strain gauge were used. However, the electrical resistance of the strain gauge is also a function of the strain and temperature. These deviations from ideal behavior can be important under certain circumstances and can cause significant errors. These errors depend on the strain gauge and the material of the part to which they are attached. When measuring the static deformations of parts and structures of GTEs under variable temperatures, there is a problem in excluding imaginary temperature deformations. When the temperature of the tested part and the strain gauge installed on it change, temperature deformation of the part, the sensitive grid of the strain gauge, and the adhesive connector occur. The primary transducer described herein is a tensometric rectangular socket for measuring static and thermal stresses in structural parts operating under extreme conditions at temperatures up to 700 °C. This sensor is a two-layer socket consisting of two sensitive elements (SE), the main axes of which are rotated relative to each other by 90°. The lower SE perceives the main deformation of the part, and the upper one, located above the lower one, plays the role of the temperature-compensating electrical resistance of the element and simultaneously registers the transverse deformation of the part. SE sockets were made of wire with a diameter of 30 microns of X20N80 alloy and were fixed between themselves and on the parts with the help of VKP-26C cement. The experimental study consisted of determining the strength characteristic of the resistance of both the lower and upper SE of the tested strain gauge mounted on a tensile sample, and separating, by means of calculation, errors associated with the thermal expansion effect of the part-strain gauge system, the change in the specific resistance of the SE material, as well as with shunting of the insulator-connector. The obtained results allow the use of this sensor in the study of GTE parts with sufficient accuracy.

Keywords

• тензометр
• чутливий елемент
• статична деформація
• силове тарування
• шунтування