Device for plastic compression of long-dimensional cylindrical samples in linear stress conditions

Abstract

A design of the device for studying plastic compression of long cylindrical specimens under conditions of a linear stress state is presented. The device is developed to study the properties of metals under plastic deformation in conditions of nonmonotonic loading. The goal of getting the accurate experimental data entails the necessary of carrying out tests using one long-length cylindrical sample, with the calculated length being more than five diameters. To prevent flexure of the long-length sample upon compression, the support conical sectors made by cutting truncated cone shaped blank into 6 or 8 equal parts with a central longitudinal hole having a diameter equal to the diameter of the test sample are used. The sectors are coupled by two pairs of semirings. A transcendental equation is obtained for determination of the taper angle of those sectors on the basis of kinematic analysis of the mobile links. This angle depends on the total weight of the sectors and sliding friction coefficients in the corresponding kinematic pairs of the device. For the considered device, the taper angle of the sectors is 36°. This device is designed and manufactured for compression testing of the samples with a diameter of 16.5 mm and a gaged length of 135 mm. Samples from steel 45 are tested with a goal of the flow curve construction and experimental verification of the strain diagrams under conditions of cyclic tensile-compression. Comparison of the calculated and experimental data proved the satisfactory accuracy of the stress determination, which makes it possible to recommend this device as a testing tool to be used in mechanical laboratories of the universities and research institutes.