A Statistical Model for Determining the Through-Transmission Ultrasonic Amplitude Response for Imperfectly Contacting Interfaces during Thermoplastic Fusion Bonding

摘要

The focus of this work is to develop a system model for through-transmission ultrasonics (TTU) as a process monitoring technique for nonintrusive, online control of thermoplastic fusion bonding processes. A closed form model is developed to predict the TTU amplitude of a fusion bond using an ultrasonic wave propagation theory with a model for the evolution of intimate contact at the material interfaces. This new approach treats the attenuation of sensor response due to imperfect contact at the bond interface as a statistical averaging of the transmission coefficients for each of the possible sound paths between source and receiver. The results of experimental and model-based parametric studies show that the intimately contacting path dominates the overall signal behavior. An approximation of the full model for an arbitrary number of interfaces based on these results is derived.