OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 3 2023 The area of the loop W can be approximately represented as the area of two triangles with the base φс (loop width in radians and loop height) the amplitude of the torsion moment is Tt in N∙m. The energy dissipation will be proportional to the loop width at the same torque for all specimens. The connection of the torsion strength of annealed specimens with the width of the mechanical hysteresis loop at torque amplitude of 176.4 N∙m is shown in fig. 12, where a) and b) are specimens made of steel 45 and steel R6M5, and “○” and “●” are joints obtained by friction welding and resistance welding, respectively. When controlled by the static hysteresis loop method, for its closure it is necessary to perform several cycles of preloading during torsion, and it is obtained automatically during bending vibrations. a b Fig. 12. Relation between the mechanical hysteresis loop width and relative torsional strength for annealed joints: a – steel 45 + steel 45; b – steel 45 + steel R6M5 In order to clarify the effect of the material structure on the weld quality, metallographic studies of joints (steel 45 + steel 45) and (steel 45 + steel R6M5) were carried out. Metallographic analysis was performed with the help of instrumental microscopes at ×400 magnification. Micrographical etching is standard for these steels. The specimens were subjected to various types of heat treatment, simulating the conditions (temperature and duration of heating during welding, cooling intensity, etc.) for the formation of the weld structure. The data obtained made it possible to specify the technological parameters of butt welding, as well as friction welding, namely, heating time, etc. (Tables 1, 2) Conclusion It has been established that with an increase in lack of welding penetration, the energy dissipation increases at the same values of the torque amplitude under static loading conditions. It has been revealed that the rigidity of qualitatively welded joints remains constant, and the rigidity of joints with lack of welding penetration decreases with an increase of torque amplitude. The usage of the static hysteresis loop method allowed establishing the connection of the rigidity and damping ability of welded joints with its strength. It allows this method to be used as a non-destructive testing method for assessing the quality of butt joints obtained by pressure welding. References 1. Leenen R. The modelling and identification of an hysteretic system. The wire-rope as a nonlinear shock vibration isolator. Department of Mechanical Engineering Eindhoven University of Technology. Technische Universiteit Eindhoven, 2012. 45 p. 2. Golovin I.S. Vnutrennee trenie i mekhanicheskaya spektroskopiya metallicheskikh materialov [Internal friction and mechanical spectroscopy of metallic materials]. Moscow, MISiS Publ., 2012. 247 p. ISBN 978-5-87623-638-8.
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