M.S. Thesis Presentation by Matthew S. Miller
Thursday, October 7, 1999

(Dr. I. Charles Ume, advisor)

"Development of a Non-Contact data Acquisition System for Robotic Welding Process Monitoring"

Abstract

The focus of this research was the development a data acquisition system for a robotic welding process that was capable of collecting ultrasonic data in a real welding environment.  This data acquisition system used a General Electric P-50 process robot and a Miller Pulstar welding machine to weld two strips of 1020 steel together, a laser to generate ultrasound in the steel on one side of the weld bead and an Electromagnetic Acoustic Transducer (EMAT) to detect the ultrasound on the other side of the weld bead.  Control of the laser and the sampling of the data collected by the EMAT were done through the data acquisition computer with a GaGe 6012 high speed A/D card and a DaqBoard 112 I/O card.  The laser control and data acquisition process was largely automated through the used of several handshaking and timing signals.

The ultrasound that was detected was shown to be a surface wave that travels over the surface of a solidified weld bead (weld reinforcement).  Furthermore, the time required for the ultrasound to travel from the ultrasonic source to the EMAT, known as the time of flight (ToF), was measured.  This ToF is directly related to the surface distance of the weld reinforcement.  While knowledge of the size of the reinforcement of a weld is of limited practical importance, it is commonly part of the weld specifications.  Hence, this data acquisition system could be incorporated into a closed loop welding control system when it is desired to control the size of the weld reinforcement.  More importantly, this research demonstrated the feasibility of using a laser to generate ultrasound and a non-contact EMAT to receive the ultrasound in a real welding environment.  As a result of the knowledge gained in this research, several recommendations are given that should aid in the development of a data acquisition system that is capable of measuring the depth of penetration of a weld pool in real time.