Thermographic test for the geometric characterization of cracks in welding using IR image rectification

• A thermographic method is proposed to characterize and measure welding cracks.
• The contour line processing enables the definition of the cracks.
• Measurements overrectified thermograms allow the planar characterization of the cracks.
• The results from the method are compared to two-dimension photogrammetry results.
• Results are better for longitudinal measures of cracks than for transverse measurements.

This paper presents a novel Infrared (IR) thermographic method based on IR image rectification and extraction of isotherms which allows the detection of cracks in welds, as well as the geometric characterization and orientation of the crack to assist the prediction of the direction of propagation of the crack through the material. The technique has been validated through its application to two specimens with different types of cracks, and the quality of the results obtained has been analyzed with respect to the real measurements of the cracks.