Use of Thermography and Ultrasonic Inspection for Evaluation of Crimped Wire Connection Quality

摘要

Quality of crimped wire connections is usually evaluated from metallographic investigation of joint cross-sections and from wire pull-out forces. Quality depends upon shape of joint after deformation and upon distribution of strands in connection where strands have to be tightly compressed with no gaps between them. Previous trials of quality connection supervision were based on mentioned methods and various criteria using statistical procedures. Today's technologies enable some other possibilities, methods and procedures for assessing crimped wire connection quality. Various non-destructive methods are used for measurement of coupling tightness which defines the quality of connection. This article gives experiences with the use of thermographic and ultrasonic method for evaluation of crimped wire connections quality. Investigations were made on the wire with 1.5 mm~2 cross section and the standard contact of a nominal rate 6.3 mm. Wire connection was crimped at crimp barrel and insulation grip at different crimp heights. Due to the low emissivity of contacts the measurement site was painted in black for thermografic analysis. Each crimped wire connection was heated by the electric current. On site observation of crimp barrel revealed temperature differences, which were compared with measurements from ultrasonic inspection, wire pull-out forces and measurements of contact voltage drop between conductor and contact at different crimp heights.