Autofrettaged cylinders have been restricted in their use to relatively low temperatures because of the stress relieving effect of high temperatures. Thus, it was felt that high-temperature operation would alter the stress pattern to such an extent that the auto-frettage process would be of little benefit. This study was conducted to determine what the effects of time and temperature would be on the residual stresses. Small-size autofrettaged cylinders were subjected to temperatures varying from 400 to 850 F for times varying from 1 hr to 72 hr. The residual stresses were determined using a modification of the Sachs’ boring-out technique. The results indicated a stress relief in all the cylinders subjected to high temperatures. However, it was found that for a given temperature and time the bore tangential stress relaxes in a manner that can be predicted by means of creep data. This relation appears to have a limiting value related to the creep-resistant characteristics of the material.

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