An experimental technique for detection of naturally grown cracks using vibration parameters

G.E. CARR; L.F. JAUREGUIZAHAR; M.D. CHAPETTI

Albuquerque, New Mexico

Conferencia; SEM 2009 Annual Conference & Exposition on Experimental & Applied Mechanics - Experimental Mechanics Applied to Failure; 2009

Society for Experimental Mechanics (SEM)

In the present work an experimental technique for crack detection using vibration analysis is used to detect naturally grown cracks in metallic components. It is known that cracks provoke a change in natural frequencies and damping characteristics of metal parts and components. Most models and computational predictions use through-width crack models instead of semi elliptical shaped cracks. Experimental tests were done on T-welded carbon steel plates to study vibration characteristics given by naturally grown cracks. Free vibration tests were performed periodically throughout the crack growth process. Crack length was measured online by indirect strain measurement technique. A comparison between theoretical calculi and experimental data was done. Different analytical models results as well as FEM results were compared to vibration data collected from tests performed. Results showed the difference between theoretical modeling and measurements from real semi elliptical cracks. Crack shape is important for the detection threshold of the method. It was found that small size semicircular cracks do not noticeably modify the beam natural frequency but tend to increase the time related damping coefficient. The results obtained showed the ability of the experimental technique to detect cracks from a size of 18.5% of the cross section area.