Failure Analysis of Open End Wrenches Containing Forging Defects

A maintenance worker was injured when his 3/4-inch (19 mm) open-ended wrench failed. The jaw of the wrench failed in an overload fashion. Wrenches were tested according to American National Standards Institute (ANSI) specification B107.6-1978. All wrenches passed ANSI standards. An additional wrench...

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Bibliographic Details
Published in:Journal of failure analysis and prevention 2010-12, Vol.10 (6), p.520-524
Main Authors: Iwand, Hans C., Wagner, Jacob A.
Format: Article
Language:English
Subjects:
Applied sciences
Characterization and Evaluation of Materials
Chemistry and Materials Science
Classical Mechanics
Corrosion and Coatings
Exact sciences and technology
Failure
Failure analysis
Forging
Fractures
Injuries
Litigation
Materials Science
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Metals. Metallurgy
Quality Control
Reliability
Safety and Risk
Scanning electron microscopy
Solid Mechanics
Technical Article > -Peer-Reviewed
Tribology
Wrenches
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Summary:A maintenance worker was injured when his 3/4-inch (19 mm) open-ended wrench failed. The jaw of the wrench failed in an overload fashion. Wrenches were tested according to American National Standards Institute (ANSI) specification B107.6-1978. All wrenches passed ANSI standards. An additional wrench of the same size and manufacturer failed in the same fashion as the first wrench. Due to pending litigation the first failed wrench was not available for analysis; however, no injuries were sustained in the second failure allowing for a detailed analysis. Hardness, chemistry, scanning electron microscopy (SEM), and metallurgical evaluations were performed on the second failure. SEM analysis revealed microvoid coalescence within the fracture zone. The microvoids were flat and smooth edged indicating insufficient bonding. A cross section of the wrench was mounted and etched using alkaline chromate to reveal an oxygen-rich zone in the jaw of the wrench. Due to the impending litigation, a joint failure analysis was performed on the first failure using both metallographic and SEM analysis. It was concluded that the failures were due to forging laps that remained present in the jaw due to improper or insufficient material having been removed during the broaching process of the wrenches.
ISSN:1547-7029
1728-5674
1864-1245
DOI:10.1007/s11668-010-9371-6