Assessment of Defect Severity in Wooden Pillars Using Ultrasonic Testing

Wooden structures are prone to internal defects, particularly cracks, which can significantly compromise their structural integrity over time. While ultrasonic testing is widely used, the relationship between ultrasonic wave behavior and crack severity is not well established. This study introduces a graded defect severity classification based on crack size and depth and evaluates its correlation with ultrasonic wave velocity, frequency, and attenuation in Abies alba (whitewood) pillars. Ultrasonic measurements were conducted on pillars with cracks of varying severity, including both defective (ranging from small to large cracks) and defect-free regions, using a digital oscilloscope and ultrasonic transducer system. Statistical analyses, including one-way ANOVA and Tukey HSD post-hoc tests, revealed significant differences in ultrasonic properties across severity classes. Among the parameters, wave velocity showed the greatest sensitivity to defect severity and correlated strongly with structural integrity, while frequency and attenuation provided supplementary but less distinct information. These findings confirm wave velocity as a reliable indicator of crack severity, and the proposed classification enhances ultrasonic data interpretation for more accurate assessment of structural degradation. This study advances the quantitative application of ultrasonic testing in timber evaluation, offering a refined approach to crack assessment in wooden pillars.