Experimental and Computational Feasibility Study of a Non-Contact Temperature Measurement Method for TIG Welding

Past decades have witnessed extensive research in the use of infrared (IR) thermal imaging for non-contact temperature measurement for direct estimation of weld penetration in Tungsten Inert Gas (TIG) welding [1-4]. IR spot sensors due to their high sensitivity and fast response time have been shown to provide accurate absolute temperature measurements [5]. IR spot sensors have also been used successfully to observe the back of the weld to directly measure weld penetration. Hence, IR sensors have the potential of being used in feedback loops and process control to thereby enhance weld quality and consistency [6-8]. However, this can be better achieved if the IR spot sensor can measure the temperature distribution on the weld (top) surface. Extraneous radiation from the welding arc has been a major issue in the design and implementation of feedback weld penetration control based on top surface temperature measurement.

The present investigation looks into the use of an IR sensor for top surface temperature measurement of the base metal at a location near the TIG weld pool. Using thermocouples attached to the bottom surface of the workpiece, additional temperature measurements will be taken for verification purposes [9]. A numerical simulation of the exact welding process will be conducted [10] to validate the temperature distribution and measurement as reported by the IR sensor. The present work aims to calibrate the IR sensor through verification based on thermocouple and simulation data and to develop a correlation between the measured surface temperature and the weld penetration and bead width.  Such a study will ensure the feasibility of IR sensor usage for direct weld surface temperature measurement and automation of the welding process based on feedback loops.