INFRARED INSPECTION OF SPOT WELDS

A RELIABLE NONDESTRUCTIVE TESTING (NDT) METHOD TO INSPECT SPOT WELDS IN STAINLESS STEEL WILL CLEAR THE WAY TO INCREASED USE OF THESE LIGHT-WEIGHT, HIGH STRENGTH CORRUGATED STAINLESS STEEL SPOT WELDED PANELS IN SHIP AND OTHER CONSTRUCTION. AN INFRARED METHOD FOR INSPECTION OF STAINLESS STEEL SPOT WELDS IS PROPOSED. THE PROJECT BUILDS ON THE EXTENSIVE EXPERIENCE OF THE PROJECT TEAM AS RELATED TO INFRARED INSPECTION OFNON-METALS SUCH AS HONEYCOMB AND COMPOSITE STRUCTURE. THE APPROACH WILL MAKE USE OF EXISTING INFRARED INSPECTION EQUIPMENT BUT WILL ADAPT THE PROCEDURE IN TERMS OF HEAT INPUT, TIME LAPSE FOR MAXIMUM INFRARED SIGNAL AND ANALYSIS OF DATA TO SHOW FEASIBILITY FOR THE INSPECTION OF SPOT WELDS IN STAINLESS STEEL. THE INFRARED RESULTS WILL BE COMPARED TO DATA FOR DESTRUCTIVE TESTS OF SEVERAL SPOT WELDS THEREBY OFFERING INCREASED CONFIDENCE IN THE INSPECTION RESULTS. PRELIMINARY WORK ON SPOT WELDS HAS CLEARLY SHOWN THE POTENTIAL OF THIS TECHNIQUE FOR INSPECTION AND THE SORTING OF SPOT WELD QUALITY OVER THE SPOT WELDS AFTER FABRICATION, BOTH IN PRODUCTION AND MAINTENANCE. HOWEVER, THE POTENTIAL FOR MONITORING SPOT WELD QUALITY DURING FABRICATION AND USING AUTOMATIC FEEDBACK TO VARY WELD PARAMETERS IS RECOGNIZED.