Views:32 Author:Site Editor Publish Time: 2019-09-11 Origin:Site
Ultrasonic impact is the use of high-power ultrasonic to drive impact tools to impact metal surface at a frequency of more than 20,000 times per second. Because of the high frequency, high efficiency and high energy of ultrasonic, the metal surface produces large compressive-plastic deformation. At the same time, the ultrasonic shock wave changes the original stress field and produces a certain number. The value of compressive stress strengthens the ultrasonic impact site. The ultrasonic driving power supply is connected with the ultrasonic transducer arranged in the housing through the cable, the vibration output terminal of the transducer is connected with the horn, and the end of the horn is equipped with an impact needle. Ultrasonic driving power converts municipal electricity into high frequency and high voltage AC current, which is transmitted to the ultrasonic transducer. Then the ultrasonic transducer converts the input electric energy into mechanical energy, that is, ultrasonic. Its form of expression is that the transducer makes reciprocating and retractable motion in the longitudinal direction. The frequency of retractable motion is equal to the AC current frequency of the driving power supply, and the displacement of retractable motion is about ten microns. The role of the horn is to amplify the output amplitude of the transducer to more than 100 microns. On the other hand, it exerts impact force on the impact needle to push the impact needle forward at high speed. After the impact needle impacts the workpiece, the energy is transferred to the weld to eliminate the internal stress. The impact head bounces back after the reaction of the workpiece, and is stimulated again after encountering the horn with high frequency vibration. It bumps into the weld seam at high speed again and again, thus completing the impact operation many times.
Ultrasonic impact technology is an effective method to eliminate harmful residual tensile stress on the surface of parts or weld seam and to form compressive stress on the surface of workpiece. It can improve the fatigue life and fatigue strength of welded parts. It is efficient and time-saving. Promoting ultrasonic impact technology conforms to the national sustainable development strategy. After welding, the stress concentration caused by excess height is reduced, the defects on the surface of the weld toe are eliminated, and at the same time, a large compressive plastic deformation is produced at the weld toe, resulting in a certain amount of residual compressive stress, adjusting the welding residual stress field, and strengthening and hardening the materials at the weld toe. A large number of experimental data show that ultrasonic impact can increase the fatigue strength of steel welded joints by 60-180%, prolong their life by 10-135 times, increase the fatigue strength of aluminum and titanium non-ferrous metal welded joints by 26-48%, prolong their life by 5-45 times, and effectively improve the fatigue properties of welded joints and structures.
Ultrasonic impact technology has been applied in many industries, including ocean, petrochemical industry, ship, heavy lifting machinery and crane, heavy die machinery, wind turbine, steel or composite bridge, aviation and railway, etc.