Study of the stress-strain and temperature fields in cutting tools using laser interferometry

OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 4 drift occurs in the measured temperature. The infrared camera has a relatively low spatial resolution because of the long wavelength of thermal radiation, which makes it dif fi cult to study small objects. There are also dif fi culties in measuring temperatures that vary over a wide range. The high cost of infrared detector arrays and infrared optics limits the application of this method. The interferometric method of registering temperature deformations of the study object [16] has low inertness, high spatial resolution, and limits the study surface to a small area. Moreover, the coef fi cient of thermal expansion ( CTE ) required to convert deformations into temperature can be measured with high accuracy using modern dilatometers [17] and does not depend on the extent of surface roughness. The disadvantage of this method is the problem of separating force- and temperature-induced deformations during their combined action, and the limitations associated with the shape of the study object surface. Formulation of the research problem At present, analytical [18, 19] and numerical [20] methods are widely used to determine the stress-strain and temperature fi elds in tools. These methods use idealized distributions of force and thermal loads on the tool faces [21, 22], which are usually obtained analytically, and the processes in the contact zone are greatly simpli fi ed. Increased reliability of the analytical results can be achieved by studying experimentally obtained boundary conditions. The above-mentioned experimental methods of studying the stress-strain state and temperatures have signi fi cant disadvantages that limit their applicability and the accuracy of the obtained results. Therefore, the development of new experimental methods for studying the phenomena that occur during the operation of various types of tools is a signi fi cant scienti fi c goal. Methods New experimental methods for studying deformations [23] and temperature fi elds [24] in cutting tools are developed to overcome the limitations of current experimental methods and to make experimental conditions more realistic. We also created a laser interferometric rig [25] to implement these methods. The principal scheme of the experimental setup is illustrated in Fig. 1. The processed material was formed as a disc (1) and was fi xed on a rotating mandrel (2). The study tool (3), installed in the tool holder (4), moves together with the optical part of the rig in the radial direction at the feed rate S . To obtain an interference pattern, an interferometer formed by the polished tool surface (5) and fi xed on the tool holder optical wedge (6) was used. The light source was a laser (7), and a beam expander (8) was applied to increase the beam aperture. The initial polarization of the laser beam is horizontal, which allows the beam to pass through a polarized beam splitter (9) without loss. After passing through the quarter- wave plate (10), the beam changes to circular polarization with counterclockwise rotation. In the interferometer, the beam is divided into measurement and reference beams. The reference beam is formed by the part of the original beam that re fl ects from the optical wedge surface facing the tool. The part of the original beam that passes through the optical wedge forms a measurement beam that strikes the polished surface of the tool. After re fl ection of both beams, their polarization vectors rotate clockwise, and when they meet again in the optical wedge, they interfere. Because of the change in the vector rotation direction, after passing through the wave plate, the resulting beam becomes vertically polarized and is re fl ected from the diagonal beam splitter surface toward the Fig. 1. Schematic diagram of the experimental rig