LEVITATION FORCES AND MECHANICAL-PROPERTIES OF VGF MELT-TEXTURED YBCO

Thermal cycling reduces the levitation force of melt-textured YBCO. In vestigations of the mechanical properties reveal that the fracture tou ghness, K-IC, and the hardness, H-v, are very low. K-IC decreases even more after thermal cycling. These poor mechanical properties in combi nation with nearly no possibility for stress relief due to plastic def ormation are thought to be responsible for the generation and propagat ion of cracks. These cracks reduce the effective radii of the screenin g currents leading to a decreased magnetic moment and the observed red uction of the levitation force.