Design of Ultrasonic Processing Device for Aluminum Surfaces

Abstract

The work in this thesis examines the design possibility of a device capable of harnessing ultrasonic oscillations through resonance such that it can be applied onto an aluminum surface to produce a compressive residual stress field. Particularly to solve the common industry issue of fatigue life failures around stress concentration areas such as holes and shape discontinuities. Purchase of a pre-assembled ultrasonic transducer was used to simplify the project, however the design research focuses on developing a Sonotrode or Horn capable of amplifying and focusing ultrasonic oscillations onto a sample surface. The development includes iterative analytical, numerical, and experimental design to achieve the final result. MatLab and Comsol software were used for analytical and numerical simulation models. Three iterations of physical designs were conducted including full steel body, combined aluminum and steel, and aluminum and carbide material design methods. The first two iterations were unsuccessful in achieving resonance due to incorrect design assumptions which lead to a mismatch in frequency resonance and a significant increase in system electrical impedance due to mass. The third iteration used a complete aluminum body with multi-stepped shape design and an attached carbide insert for tip hardness. A 200W precision ultrasonic driver and analyzer device made by Piezo Drive combined with a Laser Doppler Vibrometer was used for monitoring electrical and mechanical system response during operation. The result of this study shows that after true system resonance is achieved, maximum tip displacement occurs at the same frequency, and can be increased by increasing applied input voltage to the transducer.