OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 3 2023 pre-displacement is similar to plastic deformation in its characteristics [6]. Microfriction leads to the absorption of energy by the contact — hysteresis. Hysteresis losses in the welded joint were determined by the loop area (fig. 1). Various values can be chosen as a measure of internal friction, regardless of the sources of energy losses. The most commonly used absorption coefficient is ψ = ΔW/W, where ΔW is the irreversible dissipated energy in one loading cycle in the coordinates: torque Tt and the corresponding displacement φ. The amplitude value of the potential energy is characterized by the area of the triangle ОАВ (fig. 1). The energy dissipation, determined by the static hysteresis loop method, is the sum of losses for joints steel 45 + steel 45 and it is described by the dependence W = 2W1 + W3; and for samples steel 45 + steel R6M5 by the dependence W = 2W1 + W2 + W3. In these dependencies W1, W2 characterize the energy dissipation in the base metal volume of steel 45 and steel R6M5 respectively between the weld and the sensor blade, and W3 is the energy dissipation in the weld [4, 6, 12]. It follows that in order to obtain the energy dissipation W in the weld, it is necessary to subtract the energy dissipation in the base material from the total energy dissipation. The absorption coefficient of the weld is also determined by subtracting losses in the base material from the total absorption coefficient. This paper presents rigidity C as the rigidity of the specimen part between the sensor blades. Results and its discussion The influence of the gauge length (l) on the parameters under consideration was studied on annealed specimens. Energy dissipation in the specimen material under alternating torque loading increases directly proportional to the distance between the sensor blades when increasing from 2 to 6 mm (fig. 2). Lines 1, 2, 4 characterize the energy dissipation in steel R6M5 at amplitude values of the torque Tt = 196; 176.4; 137.2 N∙m and 3, 5 – energy dissipation in steel 45 at amplitude values of torque Tt = 196; 176.4 N∙m. The increase in energy dissipation is due to the increase in the specimen material volume where the measurement is taken. The volume increase occurs because of the gauge length increase when a diameter is constant. The absorption coefficient, being a relative characteristic, remains constant with the increase in the gauge length both for steel 45 (φ = 0.05) and for steel R6M5 (φ = 0.6). The measurements were carried out at torque amplitude of 176.4 N∙m. The measured rigidity value decreases with increasing distance between Fig. 1. Hysteresis losses in a welded joint Fig. 2. Dependence of energy dissipation on the gauge length l at various torque values
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