A BASIC STUDY FOR KNOWING THE WELDING STATE FROM TRANSMITTED ULTRASOUND THROUGH WELDING SURFACE IN ULTRASONIC WELDING OF PLASTIC RODS

摘要

Ultrasonic welding is widely used in various fields of industry. Generally, judgment on achievement of welding is difficult and it often depends on the data obtained statistically and the experience. For the purpose of obtaining the information of the welding state non-destructively, a basic examination using a simulated model of welding specimens was made to clarify how the welding state is reflected to the transmitted ultrasound in this study. Assuming the welding of plastic rods, models were made with narrow cutting depths by a lathe as simulated welding surface in plastic rods. Degree of accomplishment of welding was represented by the cross section of the welding surface of the rod. Nine kinds of specimens of different area were made. Ultrasound applied from the welding machine transmits through the welding surface and received by a transducer. This signal was analyzed in order to obtain information of the welding surface. As the result, received voltage was saturated with increase of the area, though the voltage was proportional to the welding area where the area is small. As the result of the frequency analysis of the received waves, it was found that some components of the higher harmonics were not always proportional to the welding area, though fundamental wave was comparatively proportional to the area. It was proven that the feasibility of obtaining the details of welding state by examining the transmitted and received ultrasound.