OBRABOTKAMETALLOV Vol. 26 No. 3 2024 technology The assembly was done according to the scheme in Fig. 1 with 5 ml of adhesive applied to the bolt thread. First, tightening to the nominal torque was done, then vibrations were turned on and additional tightening was done. The ultrasound was turned off after 5 seconds after re-tightening. A comparative diagram of the Topen depending on the assembly conditions is shown in Fig. 8. Fig. 8. Diagram of the dependence of the unscrewing torque on the assembly method: I – assembly without ultrasonics and adhesive; II – assembly with ultrasonics without adhesive; III – assembly without ultrasonics with adhesive; IV – assembly with ultrasonics and adhesive According to method III, adding a liquid medium reduces the friction force, which leads to an increase in the actual torque compared to I. After tightening, the adhesive fills the gaps in the joint area of the bolt and nut and polymerizes, creating a strong threaded joint. At the same time, a significant increase in the loosening torque compared to I is provided to a greater extent due to the forces of molecular adhesion of the polymer to the parts. That is, this method, compared with II, has a greater resistance to loosening, but at the same time creates a lower axial force, which ensures that the location of the parts joined by the thread is preserved. With an increase in the torque, the deformation of the thread turns begins, as in I with 32 Nm. The proposed assembly method IV combines the advantages of ultrasonic action both to increase the torque and uniform stress distribution along the turns of the thread, and to increase the properties of the epoxy adhesive. As a result, this method allows creating the greatest axial force while simultaneously creating the maximum loosening torque. Conclusions The completed theoretical and experimental studies have allowed obtaining the following results: 1. A scheme for applying ultrasonic vibrations perpendicular to the thread axis to a threaded joint has been developed; 2. Imposing shear ultrasonic vibrations during the assembly of the threaded joint creates an additional force that promotes tightening and leads to a decreased friction force, which ensures an increase in the relative loosening torque; 3. The maximum efficiency is achieved with a vibration amplitude of 5 to 9 µm. The relative loosening torque increases by 1.5 times; 4. A comparative analysis of the thread profile after disassembling the test joint and with vibrations shows the uniformity of load distribution along the turns of the threaded part with a higher torque;
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