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Investigation of the effects of manufacturing variations and materials on fatigue crack detection methods in gear teethThe fatigue life of a gear tooth can be thought of as the sum of the number of cycles required to initiate a crack, N(sub i), plus the number of cycles required to propagate the crack to such a length that fracture occurs, N(sub p). The factors that govern crack initiation are thought to be related to localized stress or strain at a point, while propagation of a fatigue crack is a function of the crack tip parameters such as crack shape, stress state, and stress intensity factor. During a test there is no clear transition between initiation and propagation. The mechanisms of initiation and propagation are quite different and modeling them separately produces a higher degree of accuracy, but then the question that continually arises is 'what is a crack?' The total life prediction in a fracture mechanics model presently hinges on the assumption of an initial crack length, and this length can significantly affect the total life prediction. The size of the initial crack is generally taken to be in the range of 0.01 in. to 0.2 in. Several researchers have used various techniques to determine the beginning of the crack propagation stage. Barhorst showed the relationship between dynamic stiffness changes and crack propagation. Acoustic emissions, which are stress waves produced by the sudden movement of stressed materials, have also been successfully used to monitor the growth of cracks in tensile and fatigue specimens. The purpose of this research is to determine whether acoustic emissions can be used to define the beginning of crack propagation in a gear using a single-tooth bending fatigue test.
Document ID
19940020296
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Wheitner, Jeffrey A. (Ohio State Univ. Cleveland, OH, United States)
Houser, Donald R. (Ohio State Univ. Cleveland, OH, United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1994
Subject Category
Quality Assurance And Reliability
Report/Patent Number
NAS 1.26:195093
NASA-CR-195093
Accession Number
94N24769
Funding Number(s)
CONTRACT_GRANT: NAG3-1147
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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