ADVANCED ULTRASONIC METHODS FOR THE NONDESTRUCTIVE EVALUATION OF BOND QUALITY IN BRAZED COMPOSITE-METAL JOINTS

A NONDESTRUCTIVE ULTRASONIC METHOD CAPABLE OF QUANTITATIVELY EVALUATING THE BOND STRENGTH AND RESIDUAL INTERFACE STRESSES AT BRAZED JOINTS, SUCH AS CARBON/CARBON-COPPER USED IN FUSION REACTOR FIRST WALL STRUCTURES, IS PLANNED. THE MECHANICAL PROPERTIES AT THE INTERFACE CONTROL THE INTIMACY OF CONTACT. BY EXAMINING THE BOUNDARY CONDITIONS THE BONDLINE PROPERTIES MAY POTENTIALLY BE EVALUATED. TWO INNOVATIVE ULTRASONIC METHODS ARE PLANNED FOR THE FEASIBILITY STUDY IN PHASE I. THE FIRST ONE INVOLVES GUIDED WAVES TRAVELLING ALONG THE INTERFACE; THE EFFECT OF BONDING INTIMACY WILL BE MEASURED USING THE VELOCITY AND THE ATTENTUATION CHARACTERISTICS OF THE ULTRASONIC WAVE. THE SECOND METHOD USES ULTRASONIC WAVES WHICH ARE NORMALLY INCIDENT TO THE BONDPLANE; THE FREQUENCY CHARACTERISTICS OF THE REFLECTION/TRANSMISSION COEFFICIENTS AT THE BONDPLANE WILL BE USED. BOTH THESE METHODS WILL BE EXPLORED THROUGH INITIAL MODELING AND EXPERIMENTAL STUDIES. THE GOAL OF THE INVESTIGATION IS TO SELECT THE OPTIMAL TECHNIQUE FOR HARDWARE DEVELOPMENT IN PHASE II.