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Professional Resources
Published online: 14 May 2011 ASM International 2011
ASTM Standard Describes Common Particles in In-Service Lubricants
ASM Technical Resources Address Fatigue Cracking in Commercial Aircraft
The objective of particle examination is to diagnose the operational condition of the machine sampled based on the quantity and type of particles observed in the oil. After break-in, normally running machines exhibit consistent particle concentration and particle types from sample to sample. An increase in particle concentration, accompanied by an increase in size and severity of particle types, is indicative of initiation of a fault. Without particulate debris analysis, in-service lubricant analysis results often fall short of concluding likely root cause or potential severity from analytical results because of missing information about the possible identification or extent of damaging mechanisms. ASTM D7684-11, ‘‘Standard Guide for Microscopic Characterization of Particles from In-Service Lubricants,’’ describes commonly found particles in in-service lubricants, but does not address methodology for quantification of particle concentration. This guide is provided to promote improved and expanded use of particulate debris analysis with in-service lubricant analysis. It helps overcome some perceived complexity and resulting intimidation that effectively limits particulate debris analysis to the hands of a specialized and very limited number of practitioners. Standardized terminology and common reporting formats provide consistent interpretation and general understanding. For more information: ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; tel: 610/832-9585; e-mail: [email protected]; web: www.astm.org/Standards/D7684.htm.
On April 3, 2011, the National Transportation Safety Board reported that fatigue cracking of aluminum lap joints was the cause of a five-foot hole that ripped open during the April 1st flight of a Southwest Airlines Boeing 737 jet. Subsequent inspections of other 737 jets revealed subsurface cracks similar to those found on the affected flight. Fatigue cracking of aircraft is explained in several technical resources from ASM International. ASM Handbook, Volume 19: Fatigue and Fracture is ASM’s most comprehensive resource on this topic and includes: •
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Fatigue Crack Growth under Variable-Amplitude Loading, by J. Schijve, Delft University of Technology. This article summarizes fatigue phenomena in metallic materials, discusses fatigue under variable-amplitude loading (such as that experienced by aircraft), where the emphasis is on crack growth, and presents prediction models. Damage Tolerance Certification of Commercial Aircraft, by T. Swift, Federal Aviation Administration. ‘‘Damage tolerance’’ is the current philosophy used for maintaining the structural safety of commercial transport aircraft. This article describes the structural evaluations necessary to comply with FAA regulations. Detection and Monitoring of Fatigue Cracks, by S.
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