Inspection of welded quality in thermoplastic welding using ultrasonics under different temperature conditions

This study experimentally investigated the effect of temperature conditions on the welding quality of thermoplastic sheets by non-destructive and destructive testing methods. Ultrasonic inspection method was employed for evaluating the fusion welds. Since the thermoplastic materials lead to significant ultrasonic signal attenuation, optimizing the setting condition for the ultrasonic testing was carried out in advance. Then, ultrasonic experiments were performed to evaluate welding qualities with respect to welding temperature conditions. In the partially incomplete welding specimen, two distinct signals were observed, reflected from the intermediate and back wall. The quality factor was defined using the ratio between intermediate and backwall reflection signals to evaluate the welding characteristics according to temperature. Based on this factor, ultrasonic images were produced using a C-scan method for welded thermoplastic specimens to visualize the welding quality. Lap-shear tests were conducted to verify the ultrasonic testing results for the welded specimens. As the welding temperature increased, there was a maximum decrease of 28 % in the percentage of incomplete welds in the C-scan results, and the lap-shear test showed an increase in shear strength. Validation through temperature-dependent shear strength confirmed the effectiveness of C-scan images using ultrasonics.