Design optimization of block horn for ultrasonic joining application using RSM–FEA–GA integration approach

This study investigates the design optimization of block horn used in ultrasonic insertion application. Ultrasonic insertion is the process of joining a metal insert with thermoplastic component. As the performance of ultrasonically produced joint depends upon the uniformity of amplitude of vibration generated by horn, the uniformity of displacement amplitude can be improved by optimizing the block horn design. The horn is computationally designed and acoustically analysed by integrating finite element analysis (FEA) with response surface methodology (RSM). The polynomial model for displacement amplitude is developed using RSM. Further, the design of horn is optimized to improve the displacement amplitude by coupling the developed polynomial model with genetic algorithm (GA) as fitness function. The optimized design is acoustically analysed, the results show that the optimal design yields maximum displacement amplitude of 29.57 µm, and the maximum stress induced in the optimal design is 16.3 MPa, which is much lower than fatigue strength of horn material. As the heat developed at joint is quality indicator, the temperature obtained at joint is measured using data acquisition system (DAQ). The measured temperature is 138°C, which correlates well with displacement amplitude developed by optimal design of block horn. The results of this study revealed that the proposed RSM–FEA–GA integration approach managed to find the optimal combination of design variables, which yields maximum displacement amplitude and results good joint performance.