Transverse stress effects on critical current and joint resistance in mechanical lap joint of a stacked HTS conductor

This paper discussed feasibility of bridge-type and multi-layer mechanical lap joint of a stacked HTS conductor. In the multi-layer mechanical lap joint, a decrease in critical current induced by transverse compressive joint force is one of the important factor to decide joint resistance. In addition, misalignment of joint section could be a problem because respective HTS tapes consisting the stacked HTS conductor could have slightly different thickness. In this study, therefore, transverse stress effect on critical current of stacked BSCCO and GdBCO conductors was experimentally investigated at first. Then, bridge-type mechanical lap joints of single layer and 2-layer HTS conductors were tested to confirm their performance and to consider the misalignment of joint section. Experimental results showed that critical current of the BSCCO conductor decreased at lower stress when the number of layers increased whereas that of the GdBCO conductor was less influenced by the stress. Joint resistance in the bridge-type mechanical lap joint was comparable to those in normal mechanical lap joint and soldered lap joint in the case of the single layer. Joint resistances in the 2-layer lap joint were two or three times larger than those in the single layer lap joint due to the misalignment. To solve this problem, compliant metal layer should be inserted into joint section.