Page 287 - Failure Analysis Case Studies II

272

Fig. 7. The fracture appearance of small cracks

'liP.V- mi-

Fig. 8. The fracture appearance of the outer layer.

alternating stress caused by pressure variations. The outer layer bears stress and bursts after the
inner layer bursts. When kerosene has penetrated the inner and middle layers as well as the steel
wire layer, kerosene gathered between the steel wire and the outer layer. Large fatigue cracks
initiated in the most highly bent position of the outer layer and formed the multiple fatigue crack
sources.
There were three openings in the inner layer of one B type hosepipe; two of them were fully
penetrating and the other was not. Fatigue cracks originated from the interface between the cotton