Nondestructive Evaluation of Shoes Bonded Area Defect Composed of EVA Materials

The accurate detection of product defects in the assembly line is crucial to any industry. To achieve accurate detection, extensive studies have been conducted, in particular, on the nondestructive inspection technique. Shoe manufacturers, however, have yet to adopt a reliable defect-detection technique for their total inspection system. The deterioration of strength, one of the most common defects found in the shoe manufacturing process, is caused by the delamination in the bonding stage. Inadequate bonding between midsole and insole, the most serious of identified defects, has so far been detected only by cutting a sample shoe and examining it for its strength. For this study, the researcher tested the validity of some nondestructive techniques employed in inspecting shoes, particularly the infrared thermography technique and non contact air coupled ultrasonic testing, which are used to examine the bonded part of shoes made from ethylene vinyl acetate (EVA), the most common material used in manufacturing shoes. The study has thus confirmed the feasibility of applying a total inspection and nondestructive inspection technique to shoe inspection.