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Far field ultrasonic welding of thermoplastics

by Zhang, Cheng

Abstract (Summary)
Far - field ultrasonic welding of thermoplastics is a bonding process in which the distance between the contact surface of the ultrasonic vibration tool and the joint interface is more than 6mm. The ultrasonic energy is transmitted through the upper part to the joint surface. The process is accomplished by applying high frequency (20 KHz), low amplitude vibrations (0.0015 - 0.0038 in) to the pieces to be joined together. The vibrational energy is dissipated as heat that elevates the plastic temperature to a level sufficient to promote welding between the parts. In this research, the effect of changes in ultrasonic welding conditions on the weld strength was investigated. The static displacement and static force as well as actual welding energy were measured. The storage modulus (Eā€™) and loss modulus (Eā€™ā€™) for different materials were determined from wave velocities and attenuation. The wave propagation in four different materials, i.e. ABS, PS, PP and HDPE, were studied. The weldability of two semicrystalline materials (PP and HDPE) in far-field welding were examined. The study shows that the dissipating ability of plastics is a basic factor which affect material weldability, and show far - field weld strength is affected by amplitude of vibration, weld time and specimen geometry. By increasing the amplitude of vibration, one can very effectively increase the weld strength. For a given combination of input power, amplitude and pressure, there exists an optimal weld time for obtaining a maximum weld strength.
Bibliographical Information:

Advisor:

School:The Ohio State University

School Location:USA - Ohio

Source Type:Master's Thesis

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ISBN:

Date of Publication:01/01/1988

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