Characterization of “Humping” in the GTA welding process using infrared images

• A novel defects identification technique based on the isotherms geometry.
• The use of infrared thermography can help to understand the weld bead defect phenomena.
• Novel correlations techniques between changes in temperature fields observed by thermography and the occurrence of defects in welds running by the TIG process.
• Proposes a real-time monitoring methodology based on the analysis of temperature gradients observed by a thermographic camera.
• Digital image processing was used to measure model responses in empirical modelling.

A real-time methodology is proposed for monitoring the occurrence of defects such as “humping” in GTA welding based on temperature gradient analysis, as observed by a thermographic camera. A technique based on the isotherm geometry for identifying defects that can be observed in a region around the arc and weld pool is provided. Isotherms between 1200 and 1400 °C were analyzed. The temperature field near both of these values varied during seamless weld bead deposition and induced a weld bead with “humping”. Abrupt changes in the temperature distribution are identified as being indicative of this type of defect in an on-line monitoring system. The use of thermographic techniques for monitoring the presence of weld defects is a promising tool that can be used for the on-line detection and control of welding process discontinuities.