Abstract
A novel hybrid image processing method is proposed to obtain the crack tip location, crack propagation path, displacement, strain fields, and plastic zone size of crack tip region under high-frequency resonant loading in this paper. An ordinary CCD camera is used to collect a series of crack images on one side of the compact tension (CT) specimen; meanwhile, a high-speed digital camera is used to acquire a series of digital speckle images of the other side of the specimen under the loading conditions at regular time intervals. Digital image processing (DIP) method is used to determine the macroscopic crack position. Digital image correlation (DIC) method is applied to obtain the displacement, strain fields, and plastic zone size of crack tip region. The characteristic digital speckle images of one stress cycle are obtained by data fitting and image matching method. Accordingly, the displacement/strain fields of crack tip region within one stress cycle and the displacement and strain amplitude fields with different crack lengths are obtained and analyzed. The obtained results are compared with the measured results of ordinary methods and show a good match. The success of this method will help to obtain better insight into and understanding of the fatigue and failure behavior of metal material with mode I crack under high-frequency resonant loading.
Highlights
Fatigue failure is the major failure mode of the metal mechanical parts
The fatigue failure cannot be completely studied by the effective theoretical method, so the specific material fatigue crack growth (FCG) tests have acquired considerable importance for studying the fracture mechanism
This paper presents a method based on the combination of Digital image processing (DIP), Digital image correlation (DIC), and digital high-speed photography techniques to measure the displacement, strain fields, and further plastic zone size of crack tip region under high-frequency resonant loading
Summary
Fatigue failure is the major failure mode of the metal mechanical parts. Fatigue cracks initiation and propagation in the metal materials or structures occur when they are subjected to alternating load and can result in material fatigue failure. This paper presents a method based on the combination of DIP, DIC, and digital high-speed photography techniques to measure the displacement, strain fields, and further plastic zone size of crack tip region under high-frequency resonant loading. First, a high-speed digital camera is used to acquire a series of digital speckle images of the CT specimen for a short period of time under high-frequency sinusoidal alternating load at regular intervals; DIC method is applied to obtain the displacement, strain fields, and further plastic zone size of crack tip region, and the characteristic load points images of one stress cycle are obtained by leastsquare sinusoidal fitting and image matching method. The research results can be a theoretical foundation for further research on the fatigue crack propagation mechanism and the parameter measurement method in the crack propagation under high-frequency resonant loading
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
