Basic Research On Application Of CCD Image Recognition Technique In Detecting Fatigue Crack

As CCD (Charge Coupled Device) image recognition technique with numerous merits such as high precision, low requirement for environment, non-contact and real-time monitoring, it has been widely applied as an important testing means in modern science and technology field. Fatigue failure has been the main form of structure strength failure. Therefore, studying on fatigue crack growth rate plays an important role in modern industry. Based on the detailed analysis of the CCD image recognition technique and the characteristics of the surface fatigue crack, a method of surface fatigue crack detecting has been studied which providing an effective approach for monitoring fatigue crack.The main work and results are as follows:1. Experimental study on fatigue crack growth has been carried out. Fatigue specimens and clamps meeting the test requirement have been designed and manufactured. The images collecting system for the fatigue crack has been designed. Surface replication has been applied in detecting surface fatigue crack in order to verify the precision of the image recognition method.2. Detecting method for surface fatigue crack has been studied. The images of micro crack and long crack have been pre-processed respectively to gain regional images of the formal and skeleton images of the latter. Based on the images above, the length and width of the surface fatigue crack have been calculated and the growth curve has been fitted. The precision of the image detecting method has been verified by comparing with the results of surface replication for fatigue crack. And the characterization methods of length and width have also been compared.3. The surface fatigue crack detecting system including length and width research modules has been developed. The functions such as images pre-processing, calculation of the length and the width, fitting of the growth curve can be realized. So an integrated, visual and alternant operation circumstance has been provided for detecting, recognizing and analyzing surface fatigue crack.