Effect of residual stress on ACFM crack measurements in drill collar threaded connections

• Published in: NDT & E international : independent nondestructive testing and evaluation Vol. 37; no. 5; pp. 337 - 343
• Main Authors: Knight, M.J, Brennan, F.P, Dover, W.D
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-07-2004; Elsevier Science
• Subjects: Alternating current field measurement; Applied sciences; Crack sizing; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Industrial metrology. Testing; Materials science; Materials testing; Mechanical engineering. Machine design; Non-destructive testing: methods and equipments; Physics; Residual stress; Thread root cold rolling; Thread root cold rolling; Alternating current field measurement; Residual stress; Crack sizing; Cold forming; Ruptures; Nondestructive testing; Bolted joints; Fatigue; Residual stresses; Petroleum industry; Cold rolling; Defect characterization; Cracks; Metrology; Drills; Damage; Electromagnetic testing; Drill pipes; Alternating current; Stress measurement
• ISSN: 0963-8695; 1879-1174
• DOI: 10.1016/j.ndteint.2003.03.001

The drill collar threaded connection of the type used in hydrocarbon exploration is a critical component of the drillstring that is highly susceptible to fatigue damage. In an attempt to reduce costly downhole failures the connections are cold rolled to introduce compressive residual stress, and when in service the connections are routinely inspected. The Alternating Current Field Measurement (ACFM) technique is an increasingly popular method of thread inspection, however, results have indicated that the ACFM defect sizing capability may be compromised when it is used to inspect recently cold rolled connections. If a connection is cold rolled without first being defect free, subsequent inspections may under estimate crack depth with the standard interpretation. Inspection before rolling is therefore necessary.