Features of Thermally Stressed Energy Equipment Tensometric Studies under High Temperatures and Strain Conditions

The aim of the study is to solve the problem of constructing schemes and models taking into account the peculiarities of conducting full-scale strain gauge studies of structures operating at temperatures up to 550°C, in the elements of which local elastoplastic deformations may occur. To solve the problem, the results of strain gauge studies of a heat exchanger, the elements of which are subjected to intense thermal effects from a liquid metal coolant with variable temperature, were used. Based on the analysis performed, schemes for constructing measuring systems are proposed that are used at various stages of research and allow the use of equipment with alternative methods of powering strain gauge transducers. The use of alternative schemes for constructing a measuring system provides data on changes in the metrological characteristics of primary transducers directly in the process of a full-scale experiment. For this purpose, the principle of dependence of the magnitude of the dissipation of the temperature characteristics of strain gauges on changes in the temperature components of their output signals is used. To construct a mathematical model of creep of strain gauges at high temperatures, experimental results were obtained that made it possible to substantiate the exponential model of changes in the uninformative output signal associated with creep. As a result of the analysis, a method for determining the creep of strain gauges, based on measuring the output signals under cyclically changing strain, was substantiated. Algorithms for taking into account errors associated with the creep of strain gauges under conditions of nonstationary thermal loading of the heat exchanger under study are proposed. As a result of the research, an adjustment was made to the experimentally obtained functions for changing the stress state of the structure under study. The results make it possible to increase the reliability of assessing the strength and service life of power engineering structures, carried out on the basis of field studies.