| Thin-walled parts have been applied widely in industrial production fields,especially in the field of aeronautics and astronautics, because of the advantages oflight weight, high structure efficiency and high reliability. Excessive vibration is easyto be produced in the process of mechanical operation for that the commonthin-walled parts is low stiffness and large area, so that the vibration noise and evenmechanical failure are generated, so modal testing and dynamic prediction must bedone for thin-walled parts. Additional quality would be introduced and the modalwould be changed for pasting the sensor to the face of thin-walled parts, if thetraditional modal broadband testing method which is realized by vibration sensor andstrength hammer is used, and the information are obtained by it is extremely limited.The modal testing method of single point laser point-by-point vibration measurementis time-consuming, operating trouble and long measurement cycle, and only somesimple thin-walled parts can be tested by the method. In view of the problem thatexisting modal testing method is difficult to meet the demand of modal testing forthin-walled parts, single point laser continuous scanning vibration measurementexperimental modal testing method for thin-walled parts is proposed in this paper, themain research contents as follows.Research on basic theory of single point laser continuous scanning vibrationmeasurement modal testing method. The basic principle of laser Doppler effect isdiscussed, and base on it, the implementation principle of laser Doppler vibrationmeasurement is analyzed; the pure modal theory and free vibration problem of finestring which both ends are fixed are researched, the theoretical relationship betweenthe vibration signal which is obtained by laser continuous scanning on the string andthe modal shapes of the string is established; the processing method for the actualvibration signal acquiring by single point laser continuous scanning vibrationmeasurement is investigated, and the calculating method for the upper and loweralternate envelope of vibration signal is proposed.Research on modal testing experiment for thin-walled beam using single pointlaser continuous scanning vibration measurement method. Thin-walled beam as testobject, single point laser continuous scanning vibration measurement modal testingscheme for thin-walled beam is proposed, The corresponding modal testing platformis put up, The first four order natural frequency and its mode shape is obtained by modal measurement testing for thin-walled beam. The testing result is analyzed andproved by contrast with finite element modal analysis results of the thin-walled beam.Research on modal testing experiment for thin-walled cylinder point using singlepoint laser continuous scanning vibration measurement method. The view constraintsabout laser continuous scanning vibration measurement methods is broken, singlepoint laser continuous scanning vibration measurement modal testing scheme forthin-walled cylinder is proposed, the sensitivity of the alignment and calibrationparameters for experiment system are analyzed in theoretically, the experimentalplatform of single point laser continuous scanning vibration measurement modaltesting for thin-walled cylinder is put up, and the calibration scheme for the testingsystem is proposed, The first five order natural frequency and its mode shape isobtained by modal measurement testing for thin-walled cylinder. The testing result isanalyzed and proved by contrast with finite element modal analysis results of thethin-walled cylinder.A single point laser continuous scanning vibration measurement modal testingmethod for thin-walled parts is proposed in the paper, the full vision vibrationmeasurement for parts is realized by it, and the measurement resolution andmeasurement accuracy is greatly improved, it is simple operating, can greatly improvethe efficiency of the experiment and time saving, which prepares for vibration andnoise reduction and structural optimization of thin-walled parts on base. |
