The effectiveness of stress relief features in austenitic drillcollar connections

✍ Scribed by K.A Macdonald

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 682 KB
• Volume: 3
• Category: Article
• ISSN: 1350-6307
• DOI: 10.1016/s1350-6307(96)00019-2

✦ Synopsis

Standard designs for stress relief features and unmodified joints in non-magnetic (austenitic) drillcollar connections are investigated using finite element stress analysis. An NC-61 connection containing API pin and box stress relief grooves and box boreback features are compared. In addition to the recognized problem of fatigue failure from critically loaded threads, instances of stress corrosion cracking in pin bores have focused attention on this region and the effect which the presence of a pin stress relief groove has on the stresses there. The results of the analyses confirm the failure sites noted in service, and predict that the pin stress relief groove gives considerable benefit in terms of reducing the pin last engaged thread peak stress (fluctuations in which can cause fatigue), but causes an unexpected increase in the maximum pin bore axial stress (which can drive stress corrosion cracking).