Coupled vibrations in the vibration system of high-power ultrasonic transducers lead to extremely complex vibration characteristics, which seriously degrade their operational performance. Therefore, optimizing the coupled vibration system and improving its dynamic performance to meet engineering application requirements has become an urgent issue to be solved.
Currently, phononic crystal structures with hole and pillar configurations have been widely investigated to optimize the coupled vibrations of ultrasonic transducers. Nevertheless, studies have demonstrated that the hybrid pillar-hole phononic crystal structure exhibits distinct advantages in broadening the bandgap width. Accordingly, this paper adopts the pillar-hole structure to optimize the coupled vibration system of high-power ultrasonic transducers. Considering that different operating environments impose diverse performance demands, this work focuses on the optimal design of coupled vibration systems for high-power large-scale ultrasonic transducers used in plastic welding, guided by the practical requirements of ultrasonic plastic welding applications.
This paper applies a quasi-periodic phononic crystal structure, which incorporates combined cylindrical holes with transverse bandgaps (capable of suppressing lateral vibrations in both the length and width directions), topological defects, and acoustic surface structures, to the optimal design of high-power ultrasonic vibration systems. Specifically, the system was optimized using five types of structures, namely cylindrical holes, pipe column holes, square column holes, three-fan column holes, and four-fan column holes. Data analysis techniques were integrated to analyze and quantify the optimization effects of these different structures on system performance.
The simulation and calculation results demonstrate that the amplitude distribution uniformity of the system's radiation surface is excellent when the column hole shape is a pipe column, square column, three-fan column, or four-fan column. Specifically, the displacement amplitude of the radiation surface is relatively large when the column hole is a square column, three-fan column, or four-fan column. Considering both the amplitude distribution uniformity and displacement amplitude of the radiation surface, the system performance can reach a relatively ideal state when the column hole shape is a square column, three-fan column, or four-fan column. This paper fabricated a system with a square column hole structure and tested its performance; the test results show that the square column hole structure effectively improves the displacement amplitude and amplitude distribution uniformity of the system's welding surface, enhances the design efficiency and reliability of the coupled vibration system of high-power ultrasonic transducers, and fully verifies the feasibility of the optimization scheme proposed in this paper.