A system of remote measurement of forces and deformations in cyclic tests of irradiated materials in the elastoplastic region

Abstract

In cyclic tests of design materials the forces and deformations must be measured continuously and recorded in the form of cyclic deformation curves and also curves of the change in the test parameters with time. As a result, the measuring system must be sufficiently rapid-acting. However, this requirement is not filled by the frequency-impuls e method of measuring displacements [4] or by the method of resonant hollows [61. In addition, it should be mentioned that the high sensitivity of the latter is possible only at a constant temperature and with location of the resonant cavity close to the sample, which makes the tests significantly more complex and expensive since the chamber together with the adjacent portions of the waveguides becomes a single-usage element. The simplest and most practical are measuring systems using resistance strain gauges and induction sensors. For the purpose of eliminating the effect of radiation the sensors are removed from the active zone and their connection with the sample is either by special extensions [7] or using design elements of the test machine itself. We should mention that despite the rigidity of test machines within the channel, tests made on the basis of design elements of the machine at a large distance from the sample satisfy the requirements of low-cycle tests since they make it possible to obtain data necessary for treating cyclic elastoplastic deformation curves under conditions of ideal elasticity of the design elements of the loading equipment. At the same time, despite some distortion of the mechanical hysteresis loop introduced by elastic deformation of the machine, the measured parameters of the curves (width of the elastoplastic hysteresis loop, its area, the torsional moment, the one-sided accumulated deformation) maintain their true values. In cyclic loading of a sample by a torsional moment, in contrast to tension-compress ion loading, the measurement of deformations is substantially easier since oscillations in temperature do not have an effect on the transmission of the angular displacements from the sample to the sensor. The use of resistance strain