Defect detection in wire welded joints using thermography investigations

The formation of gas voids inside the wire joints during laser welding may cause internal defects (cracks and porosity), that are invisible from outside. Authors propose the application of active thermography for detection of such defects. Thermal camera was used to acquire sequences of thermograms showing the joints during transient heating. Fourier analysis enabled phase value calculation, which is different for defective and non-defective samples. Laboratory results were confirmed by simulations on prepared two-dimensional model.