OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 3 2023 the sections of the sensor blades (fig. 3). The dependences were obtained for steel 45 – line 1 and steel R6M5 – line 2 at torque amplitude of 176.4 N∙m The decrease in rigidity is connected with the fact that when increasing the distance between the sections of the sensor blades at a constant torque Tt, the angle of rotation of the sections φ (fig. 1) increases relative to each other. This dependence becomes more and more convex with a significant increase in the gauge length. The energy dissipation in the welds changes when changing the torque value. Figures 4 and 5 shows the amplitude dependences of energy dissipation in the welded joints of steel 45 + steel 45 and steel 45 + steel R6M5, respectively, as well as in solid specimens from these steels: 2, 3 are joints obtained by friction welding; 1, 4 are joints obtained by resistance welding; 5, 6 are solid specimens, respectively, from steel 45 and steel R6M5. The energy dissipation shown in the figures in steel 45 and steel R6M5 under alternating loading of specimens in the elastic area occurs due to local microplastic deformation of separate overstressed grain sections. Grain sections overstress arise because of the anisotropy of the modulus of elasticity [4, 17]. Inter granular displacements play a secondary role, since the main mechanism of plastic deformation is intragranular displacements [17]. The vast majority of the dissipated energy in welds is due to lack of welding penetration, which [7, 18] can be represented as a dense mechanical contact. During alternating loading of the contact by a tangential force, a preliminary displacement occurs in it in mutually opposite directions [16]. In this case, plastic and elastic shear deformations of micro irregularities of a rough surface are carried out. When the micro displacement occurs primarily in the plastic deformation process, the material is hardened and increases its elastic limit; re-displacement after unloading is performed within the limits of elasticity but with micro friction, therefore, the deformation takes on an elastic-frictional nature, similar to the nature of plastic deformation. Sliding of the contact elements takes place in addition to its deformation. It does not enter this sliding all at once, but sequentially one after the other. This is due to the fact that micro irregularities are involved into shear by micro friction on the contact areas of elements compressed in different ways. Besides, the rigidity of micro irregularities is different. Fig. 3. Dependence of stiffness on the gauge length l Fig. 4. Amplitude dependence of energy dissipation in welded joints of steel 45 + steel 45 Fig. 5. Amplitude dependence of energy dissipation in welded joints of steel 45 + steel R6M5
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