| Mechanical stress of modern industry is getting higher and higher, more and more accidents of fatigue and failure come up continually. Thus, the fatigue life of mechanical components is very important. It is necessary to do a lot of experiments in fatigue crack propagation for studying the structure and Strength of material. Though there are various kinds of metal fatigue equipment in laboratory, there is still lack of ideal on-line crack measuring device. With the machine vision technology as the basis, the image processing technology as the main approach, the virtual instrument technology as a platform, this paper developed a high-frequency fatigue testing machine for crack-line monitoring system. The work mostly does the following:1、According to a number of the previous research with the development of machine vision in testing field, the summarization and recent developments of virtual instrument technology related to machine vision detection, and the shortcomings and lackness of crack detection technology in the existing high-frequency fatigue testing machine. I proposed a way to monitor crack in the basis of the combination machine vision with virtual instrument.2、Considering the precision, efficiency and cost. The basic characteristics of the hardware in measuring system have been discussed to select the appropriate hardware. The measuring platform of the system is based on the universal tool maker’s microscope. The CCD camera, image acquiring board and computer are employed to acquire the image of the gear.3、The theories of processing numeric pictures have been discussed to bring forward the programs used to measure the Surface length of fatigue crack. The image pretreating, edge detecting, edge fitting and image measuring can be done with the software that we program with LabVIEW and IMAQ Vision. Finally, the result of the measurement is transformed from pixel value to real value by system calibration.4、The system is designed by modular, so it has excellent reliability, maintainability and expansibility. These programs have been executed in experiments to test their effects.The success of the vision detection system raised the automation degree of the production. The efficiency is high. The function, the capability and the reliability target accord with the design requirements completely. It solved the defects of low efficiency and low accuracy of manual detecting crack quality, by choosing the LabVIEW development terrace and the powerful image processing software IMAQ Visions, the times spent on development of the system is shortened, and the system has high flexibility and reusing property by the use of it. Its application can be applied to a wide range of professional fields. |
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