Application of fractal theory in examination of resistance spot welding quality

Resistance spot welding is a technology applied extensively in mechanical manufacturing industry, non-destructive testing of resistance spot weld quality has been a hot research project in welding field. In this paper, spot welding tests were carried out and the welding spot surface images were acquired. Testing calculational formula of box-counted dimension were introduced. Calculational method about box-counted dimension was given and program about dimension and image processing based on Matlab were projected. In the end, the relationship between fractal dimension and tensile strength of the welding spot was analyzed, the result showed that the fractal dimension of the welding spot is correlated with the tecsile strength of the welding spot. It provides a basis on using welding spot imprint image to examine the weld quality.