OBRABOTKAMETALLOV Vol. 26 No. 3 2024 technology diamond needle as it moves along the measured surface and further converting its movements into a digital signal that is processed on a computer. After disassembling the joint, the screw profile of the bolt was measured to determine possible deformations caused by an increase in the actual torque. For this purpose, the contour measuring station model 220 was used, intended to measure the geometric parameters of items of various shapes. Ultrasonic treatment of epoxy adhesive A two-component adhesive EDP was used as an experimental specimen (the base is ED-20 resin, and the hardener is polyethylene polyamine). Before treating, the components were mixed manually in a mass ratio of 1 : 10. Ultrasonic treatment was done by introducing an oscillatory system emitter into a container with an adhesive composition with a volume of 50 ml (Fig. 2). The adhesive was preheated to 25 °C. The vibration system and ultrasonic generator were used the same as in the previous series of experiments. The treatment mode was set by the vibration amplitude ξm, which determines the intensity of ultrasonic effects in a liquid medium, and time. The resonant vibration frequency was 21,900 Hz. After sounding, a 10 ml sample was taken from the adhesive container to find the viscosity by rotational viscometry using a Fungilab Expert L. viscometer. During the measurement process, the software records the viscosity every second. According to the instructions, the average of 10 readings was taken as the result, if the difference between them does not exceed 3 %. Also, after processing, the heating of the adhesive was controlled using an infrared thermometer Testo 810. The optimal treatment mode was chosen according to the greatest decrease in viscosity with the least heating of the adhesive. Next, using adhesive prepared in the selected modes, 5 specimens of overlapping adhesive joint (20×20 mm) were prepared for tensile testing. The surfaces to be bonded were polished until a roughness of Ra = 0.32 µm was achieved. Thus, the results are primarily influenced by changes in the properties of the adhesive, and not by the condition of the surface. The specimens were subject to tensile tests using a universal tensile-testing machine TCB-110M-50-0U designed to measure the normalized force during mechanical tests while stretching or compressing specimens of structural materials. In addition, the polymerized adhesive specimens were evaluated for submicrostructure parameters and microhardness. The submicrostructure was evaluated using the SMM-2000 microscope in atomic force microscopy mode by the constant height method, and the microhardness using the PMT-3 device. Assembly of the adhesive-threaded joint by superposing shear vibrations As a result of the analysis of the previous stages of the study, ultrasonic treatment modes were selected that provide the greatest increase in the relative torque of loosening and improve the properties of the adhesive composition. An adhesive in a volume of 5 ml was applied to the bolt at the future location of the nut. First, the joint was tightened to the nominal standard torque, and then ultrasound was turned on, followed by additional tightening. Five joints were assembled in this way. The resulting specimens of threaded joints were kept for 24 hours, and then were sorted out, and the loosening moment was recorded. Fig. 2. Ultrasonic treatment of adhesive
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