Failure of a screw in a helicopter fuel-control unit: Was it the cause of a fatal crash?
- 134 Downloads
Investigations into a fatal helicopter crash centered around the failure of a cadmium-plated, non-conforming, steel screw in a fuel-control unit. The present study, which includes a critical evaluation of previous investigations, was undertaken with the aim of getting more definitive answers as to whether the screw failed in flight due to hydrogen-embrittlement or stress-corrosion cracking, or whether the screw failed due to liquid-metal embrittlement during a post-crash fire. Previous investigations had not resulted in any consensus regarding the mode of failure or whether the failure was responsible for the crash.
Keywordscadmium-plated steel screw energy-dispersive spectroscopy failure analysis hydrogen-embrittlement liquid-metal embrittlement stress-corrosion cracking
Unable to display preview. Download preview PDF.
- 1.J.H. Bickford: “An Introduction to the Design and Behavior of Bolted Joints,” 2nd ed., Marcel Dekker, New York, 1990.Google Scholar
- 3.H.E. Ebert: “Liquid Metal Embrittlement of Flange Connector Studs in Contact with Cadmium,” Handbook of Case Histories in Failure Analysis, vol. 1, ASM International, Materials Park, OH, 1992, pp. 335–37.Google Scholar
- 5.A.J. de Marcay and W.G. Hoover: “Cadmium-Coated Fasteners Cause LME,” Mater. Perform., 1991, p. 67.Google Scholar
- 6.L. Raymond: “The Susceptibility of Fasteners to Hydrogen Embrittlement and Stress Corrosion Cracking,” Handbook of Bolts and Bolted Joints, J.H. Bickford and S. Nasser, ed., Marcel Dekker, New York, 1998.Google Scholar
- 7.M.H. Kamdar: “Liquid Metal Embrittlement,” Failure Analysis and Prevention, vol. 11, ASM Handbook, American Society for Metals, Metals Park, OH, 1986, pp. 225–38.Google Scholar
- 9.C.R. Brooks and A. Choudhury: Failure Analysis of Engineering Materials, McGraw-Hill, New York, 2002.Google Scholar
- 10.D.N. Fager and W.F. Spurr: “Solid Cadmium Embrittlement: Steel Alloys,” Corrosion, 1971, 27, pp. 72–76.Google Scholar
- 12.M.O. Speidel: “Branching of Stress Corrosion Cracks in Aluminum Alloys,” The Theory of Stress Corrosion Cracking in Alloys, J.C. Scully, ed., NATO, Brussels, 1971, pp. 345–53.Google Scholar
- 13.A.R. Elsea and E.E. Fletcher: “Hydrogen-Induced Delayed Brittle Failures of High-Strength Steels,” DMIC Report 196, Defense Metals Information Center, Battelle Memorial Institute, Columbus, OH, Jan. 20, 1964.Google Scholar
- 14.A.R. Troiano: “The Role of Hydrogen and Other Interstitials in the Mechanical Behavior of Metals,” Trans. ASM, 1960, 52, pp. 54–80.Google Scholar
- 15.T.J. Hughel: “Delayed Failure of Class 12.8 Bolts in Automotive Rear Suspensions,” SAE Technical Paper Series, 820122, Society of Automotive Engineers, Warrendale, PA, 1982, pp. 439–44.Google Scholar
- 16.Y. Asayama: “Metal-Induced Embrittlement of Steels,” Liquid and Solid Metal Induced Embrittlement, M.H. Kamdar, ed., American Institute of Mining, Metallurgical and Petroleum Engineers, Littleton, CO, 1984, pp. 317–31.Google Scholar