Acoustic Interactions with Internal Stresses in Metals

It became evident at the residual stress meeting in San Antonio last yearl that it is necessar2 to restate the definitions for internal stresses. In general, we are talking about three kinds of residual stresses as shown in Table I. The one that's called the first kind of internal stress ranges over millimeters or centimeters {or long range internal stress) and can be identified by x-rays through a line shift. The second kind ranges over dimensions of microns and with the x-ray method gives rise to a shift as well as a line broadening. This type is usually due to particles within the material or particles of a different phase or something similar. The third kind, which ranges over 100 to 1,000 Angstroms, is a microscopic internal stress in a true sense and is indicated by x-ray line broadening only. In the following, we will be talking about the internal stresses of the third kind, due to dislocations, and later about the first kind of internal stresses.