Michael de Leon

Joining of REBCO Coated Conductor Tapes Using Ultrasonic Welding Method

In coil manufacturing for magnets and other electrical device applications that require long lengths of tapes, the joining of coated conductor (CC) tapes is still necessary. The joint is a critical part that may affect the performance of a particular device during its operation. Thus, a practical joint method which has a strong adhesion and low contact resistance without critical current Ic degradation should be developed to meet both purposes of electrical and mechanical connections. In this study, a new joint method using ultrasonic welding (UW) was introduced and the parametric tests were performed to produce a good quality of UW joint. The mechanical-controlled solder joint method was also adopted for comparison. The electrical properties such as Ic and specific joint resistance Rsj were measured at 77 K and the results were compared for each method.

Analysis of interface solid-state reaction on dissimilar ultrasonic spot welding of Al-Mg alloys

The solid-state joining nature of the ultrasonic spot welding (USW) process has been proven useful in the fields where joining applications involve dissimilar lightweight materials. This study focused on the USW of challenging dissimilar aluminum (Al)-magnesium (Mg) alloys to gain a better understanding of the dominant factors of joint performance with particular emphasis on proper lap-joint positioning. Weld qualities of dissimilar ultrasonic spot welds, classified through a series of experiments, were determined. Process parameters effects, such as failure load and fracture morphologies, showed distinctions between two dissimilar welds based on lap-joint position. Characteristic distinctions between welding process parameters and material combinations (lap-positioning) were found. Incomplete deformation zones were found during USW of Mg/Al combination, yet they were noticeable and almost the same size as the horn diameter. It can be found that proper lap-positioning of the top part of the specimen is important for efficient utilization of the USW process.