Research On The Application Of Electronic Speckle Pattern Interferomety Vibration Measurement For Plate's Crack Recognition

The principle of TV-holography system's measurement and some simple image processing techniques are introduced in this paper. Several internal crux parts of TV-holography system are described in the second chapter, such as co-axial illumination and observation, how to get image signal with CCD vidicon.In brief, some principles and arithmetic of images processing are interpreted in the thesis. They are average value filtering, medium value filtering, math morphologic operations including unlock operation and close operation and how to extracting image's contour line, skeleton, and so on. Furthermore, an essential arithmetic about unwrapping and a method how to corrective error in fringe picture are giving.In this paper, combining holographic measuring techniques with video recording and display results in a real-time system TV-holography or ESPI can be used to reveal extremely small movements and abnormal surface behavior of the test object. Under the excitation of vibration it is possible to detect and study defects and structural weaknesses in materials.In the process of experiment, we observes the movement disciplinarian of plate's every rank mode parameter. At last, in term of contradictorily problem idea, we can deduce crack's geometry parameters according to mode parameters and fringe's movement we found. The work and conclusions we did are mainly manifested in this paper:1.Identifying crack according to variety curve of every rank inherence frequency2.Identifying whether there is crack in the part and crack's approximately area when crack exists according to node line's variety current in the holography. The orientation of node line may be clear by extracting fringes skeleton3.Recognizing crack抯 nicety position according to holography's sequence variety process4.Observing some abnormal information in the variety process of holography. IdentiI~ring whether there is crack in the part and crack抯 nicety area when crack exists5.When penetrate crack exists in the part and is big in length we can indentifying it adopting small swing measurement . This method is quite simple and can reflect crack抯 nicety position, length and orientation.All crack identifying method mentioned in the thesis can be used in equipment watching. They are very engineering and practice meaning.