Fatigue crack advance presumably detected by acoustic emission signals

Journal Article · Tue Mar 01 04:00:00 EST 1983 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(83)90173-4· OSTI ID:5531398

Kim, C J; Lu, G; Weertman, J

In recent papers the authors made the prediction that the value of the exponent n of the Paris fatigue crack growth equation da/dN = C(..delta..K) /SUP n/ depends upon where in a stress cycle a fatigue crack begins its incremental growth. C is a constant, K is the cyclic stress intensity factor = 2sigma..sqrt..(..pi..a) where sigma is the amplitude of the cycle stress, a is the crack half length, and da/dN is the crack growth rate per cycle. If a fatigue crack begins its crack advance phase when the cyclic stress is still well below its peak value then n should be n approx. = 2. On the other hand if the incremental growth only commences when the cyclic stress is virtually at its peak value then n should be n approx. = 3 to 4. In this letter preliminary results are presented of an experiment which is being carried out to test these predictions. The position in a stress cycle where crack advance starts is assumed in this study to occur where the specimen gives off an acoustic emission (AE) signal. Several methods were used to characterize the observed acoustic emission signals. These are adding oil to the fracture surface and the changing of load ratio (R-ratio).

• Research Organization: Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, IL 60201
• OSTI ID: 5531398
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 17:3; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
42 ENGINEERING
420500 -- Engineering-- Materials Testing
ACOUSTIC EMISSION TESTING
ACOUSTIC TESTING
CRACK PROPAGATION
EQUATIONS
FATIGUE
FORECASTING
MATERIALS TESTING
MECHANICAL PROPERTIES
METALLOGRAPHY
NONDESTRUCTIVE TESTING
STRESS ANALYSIS
TESTING