Low-frequency The Micro Vibration Measurement System And The Liquid Surface Wave Vibration State

Based on the experiment, a laser measurement system of low frequency liquid surface wave is set up. Through detecting characteristic parameters of the liquid surface wave, the information of solid surface can be obtained. It is a way to detect the properties of the mechanical system. This thesis mainly focuses on five aspects of research work as follows:1) The surface wave of the liquid sample pool can be induced by the vibration of optical platform table-board. The clear and high visible diffraction patterns were obtained experimentally, when the laser beam illuminates obliquely on the liquid surface wave at a certain angle. The relationship between the interval of adjacent light spot and the analytic expression of the intensity distribution about the diffraction light pattern was derived theoretically. Based on this, the characteristics of the surface wave wavelength and amplitude parameters were determined. Otherwise, we investigate the dynamic process of the liquid surface wave caused by vibrating, the rising edge and the amplitude attenuation characteristics of surface wave as a function of time. The results show that the changing processes of rising edge and attenuation characteristics of surface wave present the index, and the time surface wave rising undergoes is shorter than that of the attenuation process. The attenuation coefficients also can be calculated.2) Keeping a certain wavelength of the liquid surface wave, through changing the size of the laser incident angle, and clear interference and diffraction patterns can be obtained. Basing on the experiment we can find that when the laser incident angle is under a certain range, the clear interference pattern can be obtained. While two lasers radiate the same liquid surface wave with different angles, two different interference patterns can be received. Through the data analyse, it is found that the wavelength and amplitude of the liquid surface wave obtained from this two different patterns show the same. It proves that the wavelength and amplitude of the liquid surface wave calculated theoretically is accurate.3) Laser illuminates aslant the liquid surface wave can achieve the light diffraction of the low frequency liquid surface wave, and a clear laser diffraction pattern with a higher contrast degree. Natural frequency of the large mechanical system via calculating the liquid surface wave frequency. It is showed that the natural frequency in experiments is agree with that of optical platform.4) Through establishing a low frequency micro-vibration measurement device in experiments, a clear diffraction pattern with a higher contrast degree presents. According to the principle of the bed rising and lateral spread leading that the wave blowing up, Via changing the depth of the liquid sample pool, the relationship between surface wave amplitude and liquid depth and between micro-vibration amplificatory multiple and liquid depth, the amplitude of the optical platform micro-vibration can be obtained further. The results show that the vibration liquid presets amplification effect, and magnification multiple increases linear in the liquid depth. The relationship between the amplitude of the liquid surface wave and the number of diffraction spots is also derived theoretically.5) Adopting a symmetrical mode at the two sides of the center line of optical platform to set two sound and light modulation laser measurement systems. The liquid sample pool produce surface wave caused by the optical platform table-board vibration. Using the laser to incidence aslant the liquid surface wave, two columns of synchronous interference flare present. According to the number of two interference stripes, we can judge different symmetrical parts amplitude on both sides of the different parts center line of the optical platform are consistent or not. Otherwise, in experiments detecting the consistency of different symmetrical parts amplitude comes true, and establish a kind of experiment device with a simple structure, convenient operation, low cost and accurate measurement results.