低频微振动测量系统及液体表面波振动状态的研究

【作者】 王文成；

【导师】 苗润才；

【作者基本信息】 陕西师范大学 ， 光学， 2012， 硕士

【摘要】 本文基于液体表面波的声光效应建立了低频液体表面波激光测量系统。通过探测液体表面波的特性参量,进而间接地获得固体表面的振动信息,提供了一种机械系统性能检测的方法。主要研究内容分为以下五个方面：一、光学平台台面的振动引起样品池中的液体产生表面波,激光斜入射到液体表面波上,观察到清晰的衍射图样。理论上导出了相邻衍射光斑间隔与表面波波长的关系,衍射光斑强度分布的解析关系,衍射图样宽度与表面波振幅的关系,进而求得表面波的波长和振幅。另外,基于一定深度的液体,研究激励引起的液体表面波的振动过程,分析了表面波波面的上升沿和表面波振幅随时间衰减的特性。结果表明,表面波波面在上升过程和衰减过程中振幅都呈指数规律变化,且上升过程持续时间比衰减过程持续的时间短,并计算出了衰减系数。二、保持液体表面波的波长不变,通过改变激光入射角的大小,得到清晰的干涉图样和衍射图样。理论上对比分析了这两种图样的光强分布。实验发现,当激光入射角在一定范围内可以得到干涉图样。当两束激光以不同的入射角同时照射到相同的液体表面波上时得到两幅不同的干涉图样。通过数据分析和处理,发现这两幅干涉图样得到的液体表面波的波长和振幅是相同的,这与实际情况相符。结果说明理论计算得到的液体表面波的波长和振幅具有较高的准确度。三、根据海底上升的扩散导致的波浪放大原理,实验上研究了液体深度在数十厘米范围内,改变样品池中液体的深度,得到了液体表面波的振幅随液体深度的变化规律,并发现了液体对微振动的放大效应。利用液体对微振动的放大效应,得到了微振动的振幅。四、通过敲击光学平台表面,激发产生的振动以光学平台的固有频率在其表面传播,此振动激励液体底部,并在液体表面形成表面波。通过对液体表面波的探测,间接地得到光学平台台面振动的固有频率。五、在光学平台中心线的前后两侧,采用对称方式设置两套声光调制激光测量系统。台面振动引起样品池中的液体产生表面波,激光束斜入射到液体表面波上,得到同步呈现的两列干涉光斑。根据两列衍射光斑个数的多少,可以直观的判断出光学平台台面中心线两侧不同对称部位受激振幅是否一致。另外,在实验上实现了对光学平台台面中心线两侧不同对称部位受激振幅一致性的检测,建立了一种具备结构简单、操作方便、测量成本低等特点的实验装置。更多还原

【Abstract】 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.更多还原