The burnishing section is operative to upset the material around the hole, so as to result in {HEAD ~ a residual stress} beneficial to {TAIL ~ the hole} 
The burnishing section is operative to upset the material around the hole , so as to result in { HEAD ~ a residual stress } beneficial to { TAIL ~ the hole }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL