THE EFFECTIVENESS OF STRESS RELIEF FEATURES IN AUSTENITIC DRILLCOLLARCONNECTIONS

Standard designs for stress relief features and unmodified joints in n on-magnetic (austenitic) drillcollar connections are investigated usin g finite element stress analysis. An NC-61 connection containing API p in and box stress relief grooves and box boreback features are compare d, In addition to the recognized problem of fatigue failure from criti cally loaded threads, instances of stress corrosion cracking in pin bo res have focused attention on this region and the effect which the pre sence of a pin stress relief groove has on the stresses there, The res ults of the analyses confirm the failure sites noted in service, and p redict that the pin stress relief groove gives considerable benefit in terms of reducing the pin last engaged thread peak stress (fluctuatio ns in which can cause fatigue), but causes an unexpected increase in t he maximum pin bore axial stress (which can drive stress corrosion cra cking). Copyright (C) 1996 Elsevier Science Ltd.