Acoustic emission measurement of fatigue crack closure

Journal Article · Wed Mar 01 04:00:00 EST 1995 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(95)91589-H· OSTI ID:6874588

Lee, C S; Rhyim, Y M ^[1]; Kwon, D ^[2]; Ono, K ^[3]

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1. Pohang Univ. of Science and Technology (Korea, Republic of). Center for Advanced Aerospace Materials
2. Seoul National Univ. (Korea, Republic of). Dept. of Metallurgical Engineering
3. Univ. of California, Los Angeles, CA (United States). Dept. of Materials Science and Engineering

In this study the acoustic emission (AE) technique has been applied to measure the crack closure loads precisely and the results have been compared with those measured by the conventional techniques such as the crack opening displacement (COD) method, back face strain gage (BFS) method, and surface strain gage method. In addition, fatigue tests at high stress ratio (R=0.8) have also been conducted to compared the results with those of the above methods at R=0.1 and to verify the accuracy of each method. The material used in the present investigation was an Al-Li 8090 alloy which was supplied as a 44.5mm thick rolled plate in the solution heat treated, 6% stretched and naturally aged condition. The COD and BFS methods show relatively good agreement with each other and measure the through-thickness mean value of crack closure loads. In the plane strain condition, the crack closure levels obtained by the COD and BFS methods were lower than those by the AE and surface train gage methods. The data obtained by the surface strain gage method must be interpreted carefully, because the shape of the compliance curves is affected by the location relative to the crack tip. The intrinsic fatigue life curve (da/dN vs. [Delta]K[sub eff]) obtained by the AE technique fitted well with the curve of high stress ratio (R=0.8) test at high [Delta]K, suggesting that the AE technique is sensitive to local crack-tip behavior on a microscopic scale and can be considered as a reliable measurement method for crack closure phenomena under repetitive loads.

• OSTI ID: 6874588
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 32:5; ISSN SCRMEX; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
CHEMICAL COMPOSITION
CRACK PROPAGATION
FRACTURE MECHANICS
LITHIUM ALLOYS
MECHANICS
MICROSTRUCTURE