A dedicated illumination system for fatigue crack-growth measurement

• Type: Article in International Scientific Journal
• Date: 2016

Authors

Tavares, PJ (Author) Other; Viriato, N (Author) Other; Mário Vaz (Author) FEUP; Moreira, PMGP (Author) Other

Journal

Title: Measurement: Journal of the International Measurement Confederation

Vol. 90

Pages: 85-93

ISSN: 0263-2241

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 2 Citations

Scopus - 0 Citations

Other information

Authenticus ID: P-00K-E3V

DOI: 10.1016/j.measurement.2016.04.042

Abstract (EN): This letter describes the design and development of a dedicated lighting system for the automation of fatigue crack-growth measurements. Crack growth testing is important to the characterization of the expected behaviour during service. Characteristic da/dN vs. Delta K enables the Mechanical Engineer's understanding of the material state in the presence of stress, and assists in the calculation of the remaining fatigue life expected behaviour. Similar to the darkfield illumination principle, the developed system uses a grazing incidence angle to enhance even the smallest crack detail, a necessary feature to enable the successful application of image processing methodologies for crack-growth monitoring. A poor or wrong illumination fails to reveal the true extent of hairline cracks, greatly influencing calculations that depend on large stress gradients. The device is being used in combination with a vision system for continuous monitoring of crack-growth in metallic specimens with great success. The results obtained to date are in full agreement with the expected data for the utilized specimens, which increases the confidence in the use of the device and the continuous work towards automation of fatigue experimental procedures.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9