Особливості дослідження деформаційної поведінки матеріалів при випробуваннях на згин

Abstract

The application of bending tests is due to the widespread use of this load scheme in real operating conditions and its greater softness compared to tensile strength. This makes it possible to assess the properties of materials that are brittle when tensile. Bending tests are convenient for estimating the transition temperatures from brittle to plastic (for example, in cold-brittle BCC metals and intermetallics). The issue of determining the elastic characteristics, in particular the measurement of deflections, needs to be clarified. The aim of this work is to improve experimental methods for determining the characteristics of elasticity, in particular to determine the ratio of movement of internal rollers relative to external and deflection between internal rollers, as well as accurate determination of absolute deformation of the test machine depending on load. To obtain the deformation curve of the sample without the deflection meter, a method of subtracting from the total load curve the yield curve of the test machine, which can be obtained after testing the sample with a high axial moment of inertia to minimize its deflection. To test this technique, a ceramic sample based on Al2O3 was tested. After the adjustments, it was found that the modulus of elasticity was 371.3 GPa, which corresponds to the tabular values. The proposed technique allows to accurately measure the modulus of elasticity and obtain curves of microdeformation of low-plastic materials at different test temperatures in the absence of a deflector. The deflection of the central part of the sample relative to the inner rollers by four-point bending is 3/8 of the movement of the inner rollers relative to the outer ones. The improved method of determining the deflections allows to obtain diagrams of deformation of the samples without the deflection meter, as well as to measure the modulus of elasticity and obtain curves of microdeformation of low-plastic materials at different test temperatures. Comparison of the results of determining the modulus of elasticity by methods without a deflector and with it allows you to assess the accuracy of measuring the modulus of elasticity. It is experimentally established that the difference between the values of the Young's modules calculated by the proposed method and the corresponding values calculated taking into account the directly measured deflections does not exceed 1%. Keywords: bending, stress, deformation, deflection, angle of rotation, radius of curvature, axial moment of inertia, deflection meter.