Page 272 - Fiber Fracture

FRACTURE OF SUPERFINE METALLIC WIRES 255

Fig. 15. Tested super-express linear motor cars (over 500 km/h). (Courtesy of Japan Railway Technical
Research Institute.)
&
1 .Dimensional accracy

2.Torsion and bending I-

3.Core fracture

ais
4.Sleeve fracture

5Separating

6.Sausaging I-

Fig. 16. Types of defects in drawn superconducting wire.

Fig. 18 show AE and drawing stress a against the drawing length of the wire by three
stages of drawing (Yoshida et al., 1994).
(1) After 6 passes (+ 5.8 mm + + 5.5 mm). Few changes were observable in either
AE or a along the entire length of the wire due to the sound matrix.
(2) After 7 passes (+ 5.5 mm -+ + 5.1 mm). Due to many small defects occurring in
the core, the responses for both AE and a become vivid.
(3) After 8 passes (+ 5.1 mm + + 4.8 mm). Because of the increasing number of
defects and fracture growth, a striking cyclic ruggedness in AE and a appeared, the