超声波的光外差接收

激光接收超声是一种非接触式的超声接收技术，它在超声无损评估及检测领域有重要的应用。本文设计研制了激光外差干涉接收超声的实验系统，该系统由声光调制器产生光频的频移，锁相环进行位相解调。文中重点讨论：（１）在光学部分，外差干涉光路空间准直性对信噪比的影响。（２）在信号处理电路部分，锁相环电路特性分析及其参数确定     

基于激光超声的GH4169高温合金残余应力检测

目前GH4169高温合金残余应力的检测手段多为有损检测或者检测受限的无损检测,激光超声作为一种具有非接触、高精度和无破坏性等优点的检测手段,鲜被应用于检测GH4169高温合金残余应力的分布特征。本文采用ABAQUS有限元软件模拟了热弹机制下,激光超声检测GH4169高温合金残余应力的声弹效应,为使用实验室自主研发的激光超声检测设备检测GH4169涡轮盘的残余应力提供基础,并重点将激光超声检测结果与X射线检测结果作对比。结果表明:GH4169高温合金的表面波波速与应力之间具有良好的线性关系;在实际检测过程中,由于检测范围不同,激光超声检测结果与XRD检测结果有一定差距,但均为压应力且趋势一致。     

用共焦Fabry—Perot干涉仪探测激光超声信号的研究

本文给出一种非接触式接收激光超声信号的方法，利用自行研制的实验系统，探测到用ＰＺＴ换能器和脉冲激光产生的超声信号，其信噪比足以满足进一步的电子学信号处理要求。这是将该技术应用于ＮＤＴ中的基础     

基于光栅式激光超声声谱的残余应变测量方法研究

提出了一种基于光栅激光超声进行残余应变测量的新型非接触超声检测方法。该方法利用光栅激光源激发具有特定波长的窄频带的相干表面波,通过测量表面波声谱的变化实现残余应变的测量。建立了考虑声弹效应的激光超声有限元模型,模拟了光栅激光超声在施加了预应变的介质中产生的相干表面波,研究了表面波中心频率与材料表面残余应变之间的变化关系,考察了该方法的检测能力。模拟结果表明,光栅激光超声产生的表面波(SW)波速与应变的大小呈线性关系;当应变场深度小于波长(0.05mm)时,表面波的中心频率有明显的下降,之后逐渐趋于平缓。最后,利用拉伸试验得到的具有不同残余塑性应变的试件进行实验测试,验证了基于光栅激光超声的残余应变测量方法的有效性。测量结果表明,相干表面波的波速与塑性应变呈线性关系。     

激光脉冲在固体中激励超声波的研究

本文讨论了由激光脉冲轰击试件表面，产生超声位移场的准点源理论模型；给出了用ＰＺＴ换能器接收超声波形以及检测人工缺陷的实验结果。     

基于激光超声场检测的材料常数测量方法

由于采用干涉仪的激光超声技术造价较高,对环境噪声极为敏感,很难在工业中得到广泛应用,为此开发了基于压电传感器的激光超声场检测仪(LUFT)。该系统采用激光激发、压电传感接收的方式,既保留了激光高分辨率的优势,又兼具了系统造价低、使用方便的特点。本文中,利用该检测仪对标准钢试样及不同厚度的铝试样进行了测量,获得其表面波和纵波波速,并根据固体力学理论得到铝的泊松比和杨氏模量。计算结果与文献参考值误差较小,说明该方法的可行性,也说明了该激光超声场检测仪的可靠性。     

激光陀螺仪频率稳定度高精度测量系统的研制

以碘稳定激光器为频率标准，根据拍频检测的原理，建立了一套高精度的激光陀螺仪频率稳定度测量系统。经过实验验证，该系统实现了可用光功率仅为0．1uw量级的微弱激光陀螺仪频率稳定度的测量，测量精度达到了10^-11量级。该系统的研制成功为深入开展激光陀螺仪的稳频研究奠定了基础。     

激光激发和接收固体中声脉冲方法

本文介绍了一种全光学的检测超声脉冲技术和装置。是用脉冲激光在固体中产生声(?)并以探测束偏转(刀刃技术)的原理为基础。文章给出了有关的性能(灵敏度,最佳实验条件,系统带宽,最小可检测表面梯度等)及其测量方法,实验证明该装置的带宽大于10MHz,最小可检测表面偏转角的实验值为8.5μrad。     

胶结波纹夹芯板水浸超声相控阵检测

首次采用水浸相控阵超声检测方法对加工或使用过程中的胶结波纹夹芯板粘结质量进行了无损检测,与射线、激光、常规超声等检测方法相比,该方法具有分辨率高、检测速度快等优点;设计制作了具有2mm~50mm不同尺寸脱粘缺陷的波纹夹芯板试样并进行了漏粘、脱粘缺陷人工检测实验,研究了本文方法的检测可行性和检测精度(精度至少可达2mm)。     

非线性超声相控阵无损检测系统及实验研究

相控阵超声无损检测技术近年来在无损检测领域得到了越来越广泛的应用。但当前相控阵超声检测基于传统线性超声,对于材料或结构的微缺陷、微裂纹等缺陷不敏感。研究基于超声的非线性效应的非线性超声无损检测技术对于克服线性超声相控阵技术的不足具有积极的意义。本文设计和开发了基于非线性超声相控阵的无损检测系统,并利用超声检测的标准试件对该系统的性能进行了检验。对比测试了常规线性超声方法、基于滤波的非线性超声方法以及基于反相脉冲的非线性超声方法对于钨丝线靶、超声仿体以及碳钢试块的检测效果。测试结果表明,非线性超声相控阵无损检测技术与传统线性超声相控阵无损检测相比具有空间分辨力高、缺陷分辨力强等优点,而基于反相脉冲的非线性相控阵超声无损检测在空间分辨力上比基于滤波的非线性超声检测方法又有比较显著的提高。     

连续信号激光—超声旋涡测量技术

介绍了一种新的激光超声测量技术-连续信号激光-超声旋涡测量技术。用连续波超声信号记录流场参数（速度）变化。其主要优点是：降低对超声换能器的要求;不需要高能量激光光源;可以对旋涡流场进行定量的非接触测量。     

Numerical simulation of laser ultrasonic detection of the surface microdefects on laser powder bed fusion additive manufactured 316L stainless steel

A numerical model is presented in this article to investigate the interactions between laser generated ultrasonic and the microdefects (0.01 to 0.1 mm), which are on the surface of the laser powder bed fusion additive manufactured 316L stainless steel. Firstly, the influence of the transient sound field and detection positions on Rayleigh wave signals are investigated. The interactions between the varied microdefects and the laser ultrasonic are studied. It is shown that arrival time of reflected Rayleigh (RR) waves wave is only related to the location of defects. The depth can be checked from the feature point Q, the displacement amplitude and time delay of converted transverse (RS) wave, while the width information can be evaluated from the RS wave time delay. With the aid of fitting curves, it is found to be linearly related. This simulation study provides a theoretical basis for quantitative detection of surface microdefects of additive manufactured 316L stainless steel components.     

Development of an Optical System for Simultaneous Ultrasonic Wave Propagation Imaging at Multi-points

This paper introduces the development of an optical system for simultaneous ultrasonic propagation imaging at multi-points. For the system, fiber acoustic wave grating sensors (FAWGSs) and a Q-switched pulsed laser (QPL) mirror scanner are utilized for simultaneous multipoint sensing and remote scanning ultrasonic generation, respectively. The structural strain-free FAWGS based on a fiber Bragg grating allows simultaneous multipoint acoustic emission (AE) sensing. A structure in which the FAWGSs are deployed can sense external ultrasonic stimulus. Consequently, the structure with the integrated FAWGSs cannot only detect damage event under the passive AE technique, but can also evaluate the damage under the active scheme of ultrasonic transmission and reception. The feasibility of the simultaneous multipoint ultrasonic sensing system based on the FAWGSs as built-in sensors is studied with ultrasound transmitted by a piezoelectric transducer and a QPL. Then the QPL ultrasonic generator is modified into a QPL mirror scanner for laser beam scanning and finally an optical UPI system is integrated. The ultrasonic wave propagation movie (UWPM) obtained by the optical UPI system visualizes impact damage on a carbon-fiber reinforced composite.     

MEASUREMENT AND ANALYSIS OF LASER GENERATED RAYLEIGH AND LAMB WAVES CONSIDERING ITS PULSE DURATION

In this article, laser generated Rayleigh and Lamb waves are studied by taking into account its pulse duration. The physical model and theoretical solution are presented to predict the corresponding waveforms for aluminum samples under the ablation generation regime.The waveforms of the excited Rayleigh and Lamb waves by laser with selected pulse duration were measured by laser interferometer and analyzed theoretically, and the agreement between measurement and analysis is demonstrated for the validation of the theoretical model and solution.The broadening of the Rayleigh wave and the disappearing of high order Lamb wave modes can be found with the increase of the pulse duration by the laser ultrasonic technique.     

超声散斑数字相关法应用于体面内转动测量的研究

在激光数字散斑相关法测量理论的基础上,阐述了超声散斑相关法测量的基本原理,并建立了相应的超声散斑数字相关实验分析系统。在实验分析时,首先应用模拟测量的方法对刚体面内转动对散斑场相关性的影响进行了分析;然后应用实验测量的方法再对此进行了分析;最后对刚体未知面内转角进行了实测。实验结果表明,刚体面内转动可测量的最大转角为9°,当转动角度为10°时,误差大于9%。实验中分别应用了爬山搜索法和相关系数拟合法来分别搜索整像素的位移和亚像素的位移。     

超声散斑数字相关法应用于刚体面内转动测量的研究

在激光数字散斑相关法测量理论的基础上,阐述了超声散斑相关法测量的基本原理,并建立了相应的超声散斑数字相关实验分析系统。在实验分析时,首先应用模拟测量的方法对刚体面内转动对散斑场相关性的影响进行了分析;然后应用实验测量的方法再对此进行了分析;最后对刚体未知面内转角进行了实测。实验结果表明,刚体面内转动可测量的最大转角为9°,当转动角度为10°时,误差大于9%。实验中分别应用了爬山搜索法和相关系数拟合法来分别搜索整像素的位移和亚像素的位移。     

PTFE基超声电机摩擦材料磨合阶段摩擦磨损特性研究

在超声电机运行200 h时间内,对超声电机的运行参数进行监测,采用激光共聚焦显微镜对定、转子表面粗糙度、表面形貌和磨屑特征等进行观察分析,探讨超声电机磨合期的时间及磨合期、稳定期的摩擦磨损特性.结果表明:1经过80 h磨合后,超声电机性能基本稳定.2磨合初期,摩擦材料磨损形式以黏着磨损为主,在定子表面可观测到尺寸较大的片状磨屑,进入摩擦稳定期后摩擦材料表面出现大量点蚀凹坑,表面疲劳磨损成为磨损形式之一,磨粒磨损始终存在并占重要部分;定子表面可观测到明显犁沟,磨损形式以磨粒磨损为主.3由于超声振动的存在,摩擦产生的磨屑不易在摩擦表面停留,进入稳定期后在摩擦界面难以观测到磨屑的大量存在,超声振动有排除磨屑的作用.     

Sliding friction in the presence of ultrasonic oscillations: superposition of longitudinal oscillations

Summary  It was often observed that friction forces can be reduced significantly if ultrasonic oscillations are superposed to the macroscopic sliding velocity. This phenomenon can be used to improve machining processes by addition of ultrasonic vibration to tools or workpieces, and forms the basis for many processes of ultrasonic machining. On the other hand, ultrasonic vibrations can be used to generate motion. The thrusting force of ultrasonic motors is provided to the rotor through friction. In the present paper, a simple theoretical model for friction in the presence of ultrasonic oscillations is derived theoretically and validated experimentally. The model is capable of predicting the reduction of the macroscopic friction force as a function of the ultrasonic vibration frequency and amplitude and the macroscopic sliding velocity. Received 22 November 2000; accepted for publication 6 February 2001