138 BELL SYSTEM TECHNICAL JOURNAL 



Fig. G 

 (c) Iiitcrfrystalliiic natiiix nf the cracks and the severely worked condition 

 of the metal as indicated liy several groups of slip hands traversing each 

 crystal grain. 

 These ratchet wheels developed radial cracks while in storage or in service. 

 Some of the cracks were so large as to be plainly visible to the nnaidcd eye and 

 others were of microscopic dimensions. They resulted from the metal being 

 severely Cold-worked at the time the [larts were machined and then left in a 

 strained condition. The intercrystalline nature of the cracking is shown in "c" 

 which is characteristic of season cracking. This illustration also shows the 

 crystal grains traversed by several groups of slip bands, indicating the severity 

 of the Cold-working. 



