WO2016090589A1 - Nondestructive measurement method and device for residual stress of laser ultrasonic metal material - Google Patents
Nondestructive measurement method and device for residual stress of laser ultrasonic metal material Download PDFInfo
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- WO2016090589A1 WO2016090589A1 PCT/CN2014/093543 CN2014093543W WO2016090589A1 WO 2016090589 A1 WO2016090589 A1 WO 2016090589A1 CN 2014093543 W CN2014093543 W CN 2014093543W WO 2016090589 A1 WO2016090589 A1 WO 2016090589A1
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- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
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- the invention relates to the technical field of laser ultrasonic non-destructive testing system for residual stress of metal materials in a harsh environment, in particular to a non-destructive testing device for residual stress of metal materials in a harsh environment such as high temperature, high pressure and radiation.
- Ultrasonic detection of the residual stress of a metal material is based on the acoustic-elastic effect of the ultrasonic wave, that is, when the ultrasonic wave propagates inside the material, the stress is measured by the acoustic birefringence effect caused by the stress.
- the traditional method of laser ultrasonic non-destructive testing of residual stress in metal materials is to use Nd:YAG pulsed laser to excite surface waves and receive them with a self-difference laser interferometer.
- the residual stress distribution of the material is reflected by measuring the relative change of surface acoustic velocity at different positions.
- the self-difference laser interferometer detection principle is that the ultrasonic vibration of the sample surface is u(t), and the phase shift of the laser pulse reflected by the sample surface is 4 ⁇ u(t)/ ⁇ , the light intensity after the two beams are dried.
- the expression is:
- S is the effective intensity transmission coefficient of the reference beam
- Q is the transmission coefficient of the effective intensity of the reflected beam of the sample surface
- ⁇ (t) is the phase
- t is the time.
- the phase ⁇ (t) is determined by the optical path difference of the interferometer and is affected by external vibration. Therefore, when there is environmental vibration or vibration of the sample to be inspected, the accuracy of the residual force of the measurement is seriously affected.
- the residual stress measurement method using the piezoelectric probe for receiving, the piezoelectric probe must be coupled with the workpiece to be tested by the coupling agent, so it is not applicable to the residual stress test environment of high temperature, corrosion and radiation; other non-contact laser Ultrasonic optical measurement methods such as blade detection technology measurement principle is that when the diameter of the probe beam irradiated onto the surface of the sample is less than the length of the ultrasonic wave, the reflected detection beam is deflected by the surface ultrasonic wave, and the deflection is received by the displacement sensitive detector. The amplitude and nature of the ultrasonic wave are related. This method can show the propagation of surface waves and body waves, and detect the internal defects and microstructure of the sample. The method has the advantages of simple structure, frequency bandwidth and small influence of environmental vibration, and is an effective tool for ultrasonic detection of polished surface samples, but can only be measured by residual stress of metal materials with high smooth surface.
- Laser ultrasonic non-destructive testing equipment for residual stress of traditional metal materials ultrasonic residual stress detection method and equipment using self-difference laser interferometer, limited by the principle of self-differential measurement technology, when external environment vibration Or when the sample to be tested is vibrated, the measurement residual stress is very low precision, so it can only be used in the vibration-free environment or the residual stress measurement under the condition that the sample to be tested is very stable; other laser ultrasonic optical detection methods such as the blade detection technology require the sample to be inspected.
- the surface is very smooth and requires high reflective laser performance. However, in the measurement of residual stress of actual metal materials, many metal surfaces are matt, and the shape is irregular and the surface roughness is high. Therefore, the method is applied.
- the piezoelectric probe must be coupled with the workpiece to be tested by the coupling agent, so it is not suitable for the residual stress test environment of high temperature, corrosion and radiation; the piezoelectric probe is limited by its technical principle and cannot At the same time, longitudinal wave, transverse wave and surface wave are generated, so it can only be applied to the measurement of two-dimensional residual stress; when detecting residual stress, the piezoelectric probe requires full contact with the workpiece to be inspected. If the contact is not good, the measurement value error will occur. Therefore, it is not applicable to the measurement of the residual stress of the workpiece with a complicated shape, the application Domain also very restricted.
- the invention relates to a non-destructive measuring method and device for residual stress of laser ultrasonic metal material, wherein the device comprises a pulse laser, a detecting laser, a fiber detector, a double-wave mixing optical interferometer, a data acquisition and control card, and a computer;
- the optical fiber detector is respectively connected to the pulsed laser, the detecting laser and the dual-wave mixing optical interferometer, and the detecting laser is further connected to the dual-wave mixing optical interferometer;
- the data acquisition and control The front end of the card is connected to the dual-wave mixing optical interferometer, and the back end of the data acquisition and control card is connected to the computer.
- the pulsed laser and the detecting laser employ a Nd:YAG laser having a pulse width of 10 ns and a wavelength of 1064 nm.
- the data acquisition and control card is based on a PC-DAQ data acquisition system.
- the present invention also provides a non-destructive measurement method according to the residual stress of the laser ultrasonic metal material, the method comprising the following steps:
- the pulsed laser is excited to generate ultrasonic waves, and the detecting laser is used to emit a detecting laser.
- the ultrasonic wave encounters residual stress, it is reflected back to the surface of the sample to cause surface deformation, and the detecting laser encounters the deformed sample surface, and the returned laser signal occurs.
- the change is detected by the dual-wave mixing optical interferometer, and a defect signal is generated, which is sent to a computer for processing by the data acquisition and control card, and a double-wave mixing laser ultrasonic measurement method for calculating a residual stress of the metal material is established. It is then inverted by the LabVIEW detection software to the residual stress value inside the sample, which is displayed on the computer screen in the form of curve imaging.
- Double-wave mixing laser optical interference technology is applied to measure the residual stress of metal materials in vibration environment.
- the positive effect of this innovation is that it is designed and manufactured by the principle of dual-wave mixing interference optical detection technology.
- the photorefractive crystal is a lithium niobate crystal, which can receive multiple scattered spots on the surface of the sample. Therefore, the collection ability of the light wave is very strong, and the in-plane displacement and the off-plane displacement can be simultaneously measured for the rough surface, and the precision can reach the sub-pici level.
- non-contact laser ultrasonic receiving technology using non-contact laser ultrasonic receiving technology, can achieve non-contact measurement, to meet the high temperature, corrosion, radiation metal material residual stress test environment.
- the positive effect of this innovation point is that the non-contact laser ultrasonic receiving technology is to use the laser to irradiate the workpiece to be inspected, and the ultrasonic wave is generated based on the thermoelastic theory, and the non-contact measurement can be realized without the technique of the workpiece to be inspected, thus satisfying High temperature, corrosion, and radiation metal material residual stress test environment.
- Figure 1 is a schematic diagram of the detection technique of the dual-wave mixing interferometer
- FIG. 2 is a schematic view showing the system structure of a non-destructive measuring device for residual stress of a laser ultrasonic metal material according to the present invention.
- Double-wave mixing laser ultrasonic optical interference technology the detection principle is that in the process of double-wave hybrid interference, the photorefractive crystal is equivalent to an adaptive beam splitter, and the distorted signal light and reference light energy are in the photorefractive crystal. Interference processing is performed after real-time correction is obtained.
- the schematic diagram of the double-wave hybrid interference is shown in Figure 1.
- the surface-reflected signal beam carrying the ultrasonic defect signal and the reference beam emitted by the laser are simultaneously incident into the photorefractive crystal.
- the two beams of light interfere in the crystal and form a dynamic holographic grating, and the reference beam is passed through the dynamic grating. Diffraction in a dynamic holographic grating becomes a "distortion" signal that is identical to the front of the signal light, and the signal interferes with the signal beam that is "distorted" by external environmental vibrations.
- a dynamic grating formed by interference between a signal beam and a reference beam is mainly used to correct the reference beam and the signal beam so that they can sufficiently interfere in the photoreceiver, and the vibration caused by the ultrasonic wave will It is demodulated in the form of light intensity to achieve the purpose of measuring the surface vibration of the sample, and a high-voltage electric field can be applied to the crystal to improve the coupling efficiency. It can be seen from the principle that in the actual detection, the waveform of the signal beam is inevitably caused by the surface roughness of the test piece or the vibration of the surrounding environment, so that the dual-wave hybrid interference device can pass the grating hologram established in the crystal.
- Performing real-time corrections does not have a negative effect on the superposition of the output waveforms. Even scattered light with severe distortion of the wavefront can be detected, making it suitable for rough surfaces.
- the photorefractive crystal has high-pass filtering function, it can cut off low-frequency noise, so it has strong resistance to external interference and can resist the surrounding environment. The effect of disturbance on the measurement.
- optical signal diffracted from the photorefractive crystal can be expressed as:
- a R represents the amplitude
- ⁇ opt is the angular frequency of the reference light
- ⁇ (t) is the phase modulated by the dynamic grating
- ⁇ , ⁇ , and L are respectively expressed as the gain, absorption coefficient, and length of the photorefractive crystal.
- the signal light passes through the photorefractive crystal, it is not interfered by the diffracted light, so the signal light can be expressed as:
- the signal output through the photoelectric converter is:
- 2k opt u(t) is the amount of phase change caused by the vibration of the ultrasonic residual stress signal. It can be concluded from formula (3) that the output signal is proportional to the displacement of the residual stress ultrasound, and the time of the movement of the ultrasonic wave in the test block can be calculated by using the light intensity signal, and then the time point of the residual stress signal is obtained, and then the calculation can be performed. The exact location of the residual stress in the test block.
- the two-dimensional wave mixing interferometer of the device is designed and manufactured by the principle of double-wave mixing interference optical detection technology.
- the photorefractive crystal is a lithium niobate crystal and can receive multiple surfaces of the sample. Scattering the light spot, therefore, the ability to collect light waves is very strong, and the in-plane displacement and the out-of-plane displacement can be simultaneously measured for the rough surface, and the precision can reach the sub-pici level.
- the device uses a Nd:YAG laser with a pulse width of 10 ns and a wavelength of 1064 nm as the laser ultrasonic excitation source and detection laser source.
- the laser ultrasonic optical receiving system adopts a two-dimensional wave mixing interferometer, and the device software uses LabView to develop the residual stress of the metal material.
- Measurement software, system hardware based on PC-DAQ data acquisition system, the equipment workflow is pulse laser used to stimulate the generation of ultrasonic waves, detection laser is used to emit detection laser, after the ultrasonic encounters residual stress, it is reflected back to the surface of the sample, causing surface deformation The detection laser encounters the deformed sample surface, and the returned laser signal changes.
- a defect signal is generated, which is sent to the computer through the data acquisition card for processing, and the method is used to establish a double Wave-mixed laser ultrasonic measurement of the residual stress calculation model of metal materials, and then inverted by LabVIEW detection software into the residual stress value inside the sample, displayed on the computer screen in the form of curve imaging; the structure of the equipment system is shown in Figure 2.
Abstract
A nondestructive measurement method and device for residual stress of a laser ultrasonic metal material. The device comprises a pulse laser, a detecting laser, an optical fiber detector, a dual-wave frequency mixing optical interferometer, a data collection and control card, and a computer. The optical fiber detector is separately connected to the pulse laser, the detecting laser and the dual-wave frequency mixing optical interferometer. The detecting laser is further connected to the dual-wave frequency mixing optical interferometer. The front end of the data collection and control card is connected to the dual-wave frequency mixing optical interferometer, and the rear end of the data collection and control card is connected to the computer. The device has strong light wave gathering capability, can measure both in-plane displacement and out-of-plane displacement of a rough surface, and can reach precision of the sub-picometer level. The device realizes non-contact measurement with no blind area of residual stress of a detected metal material workpiece in a test environment of high temperature, corrosion and radiation.
Description
本发明涉及到恶劣环境下金属材料残余应力的激光超声无损检测系统技术领域，具体来讲就是一种高温、高压及辐射等恶劣环境下金属材料残余应力的无损检测设备。The invention relates to the technical field of laser ultrasonic non-destructive testing system for residual stress of metal materials in a harsh environment, in particular to a non-destructive testing device for residual stress of metal materials in a harsh environment such as high temperature, high pressure and radiation.
超声波检测金属材料的残余应力，是基于超声波的声弹效应，即超声波在材料内部传播时，利用应力引起的声双折射效应对应力进行测量。传统的金属材料残余应力激光超声无损检测方法，是用Nd：YAG脉冲激光激发表面波，用自差式激光干涉仪接收，通过测量表面波声速在不同位置上的相对变化反映材料的残余应力分布，但是由于自差式激光干涉仪检测原理是设样品表面的超声振动为u(t)，激光脉冲被样品表面反射的相移为4πu(t)/λ，则两束光干后的光强表达式为：Ultrasonic detection of the residual stress of a metal material is based on the acoustic-elastic effect of the ultrasonic wave, that is, when the ultrasonic wave propagates inside the material, the stress is measured by the acoustic birefringence effect caused by the stress. The traditional method of laser ultrasonic non-destructive testing of residual stress in metal materials is to use Nd:YAG pulsed laser to excite surface waves and receive them with a self-difference laser interferometer. The residual stress distribution of the material is reflected by measuring the relative change of surface acoustic velocity at different positions. However, since the self-difference laser interferometer detection principle is that the ultrasonic vibration of the sample surface is u(t), and the phase shift of the laser pulse reflected by the sample surface is 4πu(t)/λ, the light intensity after the two beams are dried. The expression is:
式中S为参考光束的有效强度透射系数，Q为样品表面反射检测光束的有效强度的透射系数，Φ(t)为相位，t为时间。其中，相位Φ(t)由干涉仪的光程差决定，并受外界振动的影响。因此，当外界有环境振动或被检样品本身发生振动，则会严重影响测量残余余力的精度。而采用压电探头进行接收的残余应力测量方法，压电探头必须通过耦合剂跟被检工件进行耦合才能检测，因此不适用高温、腐蚀、辐射的复合材料残余应力测试环境；其他非接触式激光超声光学测量方法如刀刃检测技术测量原理是当激光照射到试样表面的探测光束直径小于超声波长时，反射检测光束由于表面超声波动而发生偏转，偏转大小由位移敏感探测器接收，偏转值与超声波的振幅及性质有关，这一方法能显示表面波与体波的传播情况，检测出试样的内部缺陷和微结构。该方法具有结构简单，频带宽，环境振动影响小等优点，是对抛光表面样品进行超声检测的有效工具，但是只能用高光滑表面的金属材料残余应力测量。Where S is the effective intensity transmission coefficient of the reference beam, Q is the transmission coefficient of the effective intensity of the reflected beam of the sample surface, Φ(t) is the phase, and t is the time. Among them, the phase Φ(t) is determined by the optical path difference of the interferometer and is affected by external vibration. Therefore, when there is environmental vibration or vibration of the sample to be inspected, the accuracy of the residual force of the measurement is seriously affected. The residual stress measurement method using the piezoelectric probe for receiving, the piezoelectric probe must be coupled with the workpiece to be tested by the coupling agent, so it is not applicable to the residual stress test environment of high temperature, corrosion and radiation; other non-contact laser Ultrasonic optical measurement methods such as blade detection technology measurement principle is that when the diameter of the probe beam irradiated onto the surface of the sample is less than the length of the ultrasonic wave, the reflected detection beam is deflected by the surface ultrasonic wave, and the deflection is received by the displacement sensitive detector. The amplitude and nature of the ultrasonic wave are related. This method can show the propagation of surface waves and body waves, and detect the internal defects and microstructure of the sample. The method has the advantages of simple structure, frequency bandwidth and small influence of environmental vibration, and is an effective tool for ultrasonic detection of polished surface samples, but can only be measured by residual stress of metal materials with high smooth surface.
传统金属材料残余应力的激光超声无损检测设备，采用自差式激光干涉仪的超声波残余应力检测方法及设备，受自差式测量技术原理限制，当外部环境振动
或被检样品发生振动时，测量残余应力精度很低，因此只能用于无振动环境或被检样品非常稳定的状况下残余应力测量；其他激光超声光学检测方法如刀刃检测技术要求被检样品表面非常光滑，要求具有较高的反射激光性能，但是，在实际金属材料的残余应力测量，很多金属表面是亚光状况，且外观形状不规则，表面粗糙度也较高，因此，该方法应用范围受到很大限制；另外，压电探头必须通过耦合剂跟被检工件进行耦合才能检测，因此不适用高温、腐蚀、辐射的金属材料残余应力测试环境；压电探头受其技术原理限制，不能同时产生纵波、横波和表面波，因此只能适用于二维残余应力的测量；压电探头在检测残余应力时，要求与被检工件全面接触，如果接触不好，就会出现测量数值误差，因此，不适用复杂形状被检工件的残余应力的测量，应用领域也受到很大限制。Laser ultrasonic non-destructive testing equipment for residual stress of traditional metal materials, ultrasonic residual stress detection method and equipment using self-difference laser interferometer, limited by the principle of self-differential measurement technology, when external environment vibration
Or when the sample to be tested is vibrated, the measurement residual stress is very low precision, so it can only be used in the vibration-free environment or the residual stress measurement under the condition that the sample to be tested is very stable; other laser ultrasonic optical detection methods such as the blade detection technology require the sample to be inspected. The surface is very smooth and requires high reflective laser performance. However, in the measurement of residual stress of actual metal materials, many metal surfaces are matt, and the shape is irregular and the surface roughness is high. Therefore, the method is applied. The range is greatly limited; in addition, the piezoelectric probe must be coupled with the workpiece to be tested by the coupling agent, so it is not suitable for the residual stress test environment of high temperature, corrosion and radiation; the piezoelectric probe is limited by its technical principle and cannot At the same time, longitudinal wave, transverse wave and surface wave are generated, so it can only be applied to the measurement of two-dimensional residual stress; when detecting residual stress, the piezoelectric probe requires full contact with the workpiece to be inspected. If the contact is not good, the measurement value error will occur. Therefore, it is not applicable to the measurement of the residual stress of the workpiece with a complicated shape, the application Domain also very restricted.
发明内容Summary of the invention
本发明涉及一种激光超声金属材料残余应力的无损测量方法及设备，所述设备包括脉冲激光器、检测激光器、光纤检测仪、双波混频光学干涉仪、数据采集及控制卡、计算机；其中，所述光纤检测仪分别连所述接脉冲激光器、所述检测激光器和所述双波混频光学干涉仪，所述检测激光器还连接所述双波混频光学干涉仪；所述数据采集及控制卡的前端连接所述双波混频光学干涉仪，所述数据采集及控制卡的后端连接所述计算机。The invention relates to a non-destructive measuring method and device for residual stress of laser ultrasonic metal material, wherein the device comprises a pulse laser, a detecting laser, a fiber detector, a double-wave mixing optical interferometer, a data acquisition and control card, and a computer; The optical fiber detector is respectively connected to the pulsed laser, the detecting laser and the dual-wave mixing optical interferometer, and the detecting laser is further connected to the dual-wave mixing optical interferometer; the data acquisition and control The front end of the card is connected to the dual-wave mixing optical interferometer, and the back end of the data acquisition and control card is connected to the computer.
进一步地，所述脉冲激光器和检测激光器采用脉宽10ns、波长1064nm的Nd：YAG激光器。Further, the pulsed laser and the detecting laser employ a Nd:YAG laser having a pulse width of 10 ns and a wavelength of 1064 nm.
进一步地，所述数据采集及控制卡是基于PC-DAQ数据采集系统。Further, the data acquisition and control card is based on a PC-DAQ data acquisition system.
进一步地，本发明还提供一种根据所述的激光超声金属材料残余应力的无损测量方法，所述方法包括如下步骤：Further, the present invention also provides a non-destructive measurement method according to the residual stress of the laser ultrasonic metal material, the method comprising the following steps:
所述脉冲激光器激励产生超声波，所述检测激光器用于发射检测激光，超声波遇到残余应力后，经反射返回样品表面，引起表面形变，检测激光遇到形变的样品表面，返回的激光信号会发生变化，经所述双波混频光学干涉仪进行检测后，产生缺陷信号，通过所述数据采集及控制卡送入计算机中进行处理，建立双波混频激光超声测量金属材料残余应力计算模型，再经过LabVIEW检测软件反演为样品内部的残余应力值，以曲线成像的方式显示在计算机屏幕上。The pulsed laser is excited to generate ultrasonic waves, and the detecting laser is used to emit a detecting laser. After the ultrasonic wave encounters residual stress, it is reflected back to the surface of the sample to cause surface deformation, and the detecting laser encounters the deformed sample surface, and the returned laser signal occurs. The change is detected by the dual-wave mixing optical interferometer, and a defect signal is generated, which is sent to a computer for processing by the data acquisition and control card, and a double-wave mixing laser ultrasonic measurement method for calculating a residual stress of the metal material is established. It is then inverted by the LabVIEW detection software to the residual stress value inside the sample, which is displayed on the computer screen in the form of curve imaging.
本发明具有以下特点：
The invention has the following characteristics:
1、采用双波混频激光光学干涉技术，适用于振动环境的金属材料残余应力测量。该创新点的积极效果在于：采用双波混频干涉光学检测技术的原理设计制造而成的，在干涉仪中，光折变晶体为铌酸锂晶体，能接收样品表面的多个散射光斑，因此，对光波的收集能力非常强，可以对于粗糙表面均能同时测量出面内位移和离面位移，精度可达亚皮米级。1. Double-wave mixing laser optical interference technology is applied to measure the residual stress of metal materials in vibration environment. The positive effect of this innovation is that it is designed and manufactured by the principle of dual-wave mixing interference optical detection technology. In the interferometer, the photorefractive crystal is a lithium niobate crystal, which can receive multiple scattered spots on the surface of the sample. Therefore, the collection ability of the light wave is very strong, and the in-plane displacement and the off-plane displacement can be simultaneously measured for the rough surface, and the precision can reach the sub-pici level.
2、建立双波混频激光超声测量金属材料残余应力计算模型，采用非接触激光超声技术实现对金属材料被检样品的测量。该创新点的积极效果在于：基于双波混频激光超声光学干涉技术，建立了对金属材料残余应力的计算模型，采用非接触式激光超声技术，实现对金属材料被件工件的残余应力实现无盲区测量。2. Establish a two-wave mixing laser ultrasonic measurement of the residual stress calculation model of metal materials, and use non-contact laser ultrasonic technology to measure the metal material samples. The positive effect of this innovation point is that based on the dual-wave mixing laser ultrasonic optical interference technology, the calculation model of the residual stress of the metal material is established, and the non-contact laser ultrasonic technology is used to realize the residual stress of the workpiece of the metal material. Blind area measurement.
3、采用非接触式激光超声接收技术，可实现非接触测量，满足高温、腐蚀、辐射的金属材料残余应力测试环境。该创新点的积极效果在于：采用非接触式激光超声接收技术，是利用激光照射到被检工件上，基于热弹理论产生超声波，不需要与被检工件技术，可实现非接触测量，因此满足高温、腐蚀、辐射的金属材料残余应力测试环境。3, using non-contact laser ultrasonic receiving technology, can achieve non-contact measurement, to meet the high temperature, corrosion, radiation metal material residual stress test environment. The positive effect of this innovation point is that the non-contact laser ultrasonic receiving technology is to use the laser to irradiate the workpiece to be inspected, and the ultrasonic wave is generated based on the thermoelastic theory, and the non-contact measurement can be realized without the technique of the workpiece to be inspected, thus satisfying High temperature, corrosion, and radiation metal material residual stress test environment.
通过参照附图更详细地描述本发明的示例性实施例，本发明的以上和其它方面及优点将变得更加易于清楚，在附图中：The above and other aspects and advantages of the present invention will become more apparent from the following detailed description of exemplary embodiments of the invention.
图1为双波混频干涉仪的检测技术原理图；Figure 1 is a schematic diagram of the detection technique of the dual-wave mixing interferometer;
图2为本发明的一种激光超声金属材料残余应力的无损测量设备的系统结构示意图。2 is a schematic view showing the system structure of a non-destructive measuring device for residual stress of a laser ultrasonic metal material according to the present invention.
在下文中，现在将参照附图更充分地描述本发明，在附图中示出了各种实施例。然而，本发明可以以许多不同的形式来实施，且不应该解释为局限于在此阐述的实施例。相反，提供这些实施例使得本公开将是彻底和完全的，并将本发明的范围充分地传达给本领域技术人员。In the following, the invention will now be described more fully hereinafter with reference to the accompanying drawings in which FIG. However, the invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and
在下文中，将参照附图更详细地描述本发明的示例性实施例。Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.
双波混频激光超声光学干涉技术，检测原理是在双波混合干涉的过程中，光折变晶体相当于一个自适应的分束器，失真的信号光和参考光能在光折变晶体中得到实时修正后再进行干涉处理。双波混合干涉的原理图如图1所示，经试块表
面反射携带了超声缺陷信号的信号光束与激光发出的参考光束同时射入光折变晶体中，两束光波在晶体中干涉并形成动态全息光栅，同时再让参考光束通过该动态光栅，使其在动态全息光栅中衍射，变成一个与信号光波前相同的“畸变”信号，该信号与受外界环境振动干扰而“畸变”的信号光束再相干涉。Double-wave mixing laser ultrasonic optical interference technology, the detection principle is that in the process of double-wave hybrid interference, the photorefractive crystal is equivalent to an adaptive beam splitter, and the distorted signal light and reference light energy are in the photorefractive crystal. Interference processing is performed after real-time correction is obtained. The schematic diagram of the double-wave hybrid interference is shown in Figure 1.
The surface-reflected signal beam carrying the ultrasonic defect signal and the reference beam emitted by the laser are simultaneously incident into the photorefractive crystal. The two beams of light interfere in the crystal and form a dynamic holographic grating, and the reference beam is passed through the dynamic grating. Diffraction in a dynamic holographic grating becomes a "distortion" signal that is identical to the front of the signal light, and the signal interferes with the signal beam that is "distorted" by external environmental vibrations.
在光折变晶体中，由信号光束和参考光束相互干涉形成的动态光栅，其主要用途是用于校正参考光束和信号光束，使它们能够在光电接收器重充分干涉，则超声波所引起的振动将以光强度的形式解调出来，从而达到测量试样表面振动的目的，同时可以在晶体上外加高压电场提高耦合效率。由原理可以看出，在现实检测中，不可避免的会因为试块表面粗糙度或周围环境的振动导致信号光束波形的失真，这样双波混合干涉装置可以通过晶体中建立的光栅全息图对其进行实时修正，并不会对输出波形相叠加产生负作用。即便是波前严重畸变的散射光也可以检测，使其适用于粗糙表面；此外，由于光折变晶体具有高通滤波的功能，能截止低频噪声，故抗外界干扰的能力强，可抗周围环境的扰动对测量的影响。In a photorefractive crystal, a dynamic grating formed by interference between a signal beam and a reference beam is mainly used to correct the reference beam and the signal beam so that they can sufficiently interfere in the photoreceiver, and the vibration caused by the ultrasonic wave will It is demodulated in the form of light intensity to achieve the purpose of measuring the surface vibration of the sample, and a high-voltage electric field can be applied to the crystal to improve the coupling efficiency. It can be seen from the principle that in the actual detection, the waveform of the signal beam is inevitably caused by the surface roughness of the test piece or the vibration of the surrounding environment, so that the dual-wave hybrid interference device can pass the grating hologram established in the crystal. Performing real-time corrections does not have a negative effect on the superposition of the output waveforms. Even scattered light with severe distortion of the wavefront can be detected, making it suitable for rough surfaces. In addition, because the photorefractive crystal has high-pass filtering function, it can cut off low-frequency noise, so it has strong resistance to external interference and can resist the surrounding environment. The effect of disturbance on the measurement.
双波混频激光超声测量金属材料残余应力计算模型如下：The calculation model of residual stress of metal materials by double-wave mixing laser ultrasonic measurement is as follows:
从光折变晶体中衍射出来的光信号可以表示为：The optical signal diffracted from the photorefractive crystal can be expressed as:
公式中，AR表示振幅，ωopt为参考光的角频率，φ(t)为受动态光栅调制后相位，γ、α、L分别表示为光折变晶体的增益、吸收系数和长度。In the formula, A R represents the amplitude, ω opt is the angular frequency of the reference light, φ(t) is the phase modulated by the dynamic grating, and γ, α, and L are respectively expressed as the gain, absorption coefficient, and length of the photorefractive crystal.
信号光通过光折变晶体时，没有受到衍射光的干扰，这样信号光可以表示为：When the signal light passes through the photorefractive crystal, it is not interfered by the diffracted light, so the signal light can be expressed as:
信号光束与参考光束相互干涉后，经光电变换器输出的信号为：After the signal beam and the reference beam interfere with each other, the signal output through the photoelectric converter is:
公式中，
2koptu(t)为超声残余应力信号振动引起的相位变化量。由公式(3)可以得出，输出的信号与残余应力超声的位移成正比，可以利用光强信号计算出超声在试块中运动的时间，进而获取出残余应力信号的时间点，就可以计算出试块中残余应力的确切位置。formula, 2k opt u(t) is the amount of phase change caused by the vibration of the ultrasonic residual stress signal. It can be concluded from formula (3) that the output signal is proportional to the displacement of the residual stress ultrasound, and the time of the movement of the ultrasonic wave in the test block can be calculated by using the light intensity signal, and then the time point of the residual stress signal is obtained, and then the calculation can be performed. The exact location of the residual stress in the test block.
本设备二维波混频干涉仪即是采用双波混频干涉光学检测技术的原理设计制造而成的，在干涉仪中，光折变晶体为铌酸锂晶体，能接收样品表面的多个散射光斑，因此，对光波的收集能力非常强，可以对于粗糙表面均能同时测量出面内位移和离面位移，精度可达亚皮米级。The two-dimensional wave mixing interferometer of the device is designed and manufactured by the principle of double-wave mixing interference optical detection technology. In the interferometer, the photorefractive crystal is a lithium niobate crystal and can receive multiple surfaces of the sample. Scattering the light spot, therefore, the ability to collect light waves is very strong, and the in-plane displacement and the out-of-plane displacement can be simultaneously measured for the rough surface, and the precision can reach the sub-pici level.
设备采用脉宽10ns、波长1064nm的Nd：YAG激光器，作为激光超声激发源和检测激光源，激光超声光学接收系统采用研制二维波混频干涉仪，设备软件采用LabView开发出金属材料的残余应力测量软件，系统硬件基于PC-DAQ数据采集系统，设备工作流程是脉冲激光器用来激励产生超声波，检测激光器用于发射检测激光，由于超声波遇到残余应力后，经反射返回样品表面，引起表面形变，检测激光遇到形变的样品表面，返回的激光信号会发生变化，经二波混频光学干涉仪进行检测后，产生缺陷信号，通过数据采集卡送入计算机中进行处理，经过本方法建立双波混频激光超声测量金属材料残余应力计算模型，再经过LabVIEW检测软件反演为样品内部的残余应力值，以曲线成像的方式显示在计算机屏幕上；设备系统结构图如下图2所示。The device uses a Nd:YAG laser with a pulse width of 10 ns and a wavelength of 1064 nm as the laser ultrasonic excitation source and detection laser source. The laser ultrasonic optical receiving system adopts a two-dimensional wave mixing interferometer, and the device software uses LabView to develop the residual stress of the metal material. Measurement software, system hardware based on PC-DAQ data acquisition system, the equipment workflow is pulse laser used to stimulate the generation of ultrasonic waves, detection laser is used to emit detection laser, after the ultrasonic encounters residual stress, it is reflected back to the surface of the sample, causing surface deformation The detection laser encounters the deformed sample surface, and the returned laser signal changes. After the detection by the two-wave mixing optical interferometer, a defect signal is generated, which is sent to the computer through the data acquisition card for processing, and the method is used to establish a double Wave-mixed laser ultrasonic measurement of the residual stress calculation model of metal materials, and then inverted by LabVIEW detection software into the residual stress value inside the sample, displayed on the computer screen in the form of curve imaging; the structure of the equipment system is shown in Figure 2.
以上所述仅为本发明的实施例而已，并不用于限制本发明。本发明可以有各种合适的更改和变化。凡在本发明的精神和原则之内所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。
The above description is only an embodiment of the present invention and is not intended to limit the present invention. The invention is susceptible to various modifications and changes. Any modifications, equivalents, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.
Claims (5)
- 一种激光超声金属材料残余应力的无损测量设备，其特征在于：A non-destructive measuring device for residual stress of laser ultrasonic metal materials, characterized in that:所述设备包括脉冲激光器、检测激光器、光纤检测仪、双波混频光学干涉仪、数据采集及控制卡、计算机；其中，所述光纤检测仪分别连所述接脉冲激光器、所述检测激光器和所述双波混频光学干涉仪，所述检测激光器还连接所述双波混频光学干涉仪；所述数据采集及控制卡的前端连接所述双波混频光学干涉仪，所述数据采集及控制卡的后端连接所述计算机。The device includes a pulse laser, a detection laser, a fiber detector, a dual-wave mixing optical interferometer, a data acquisition and control card, and a computer; wherein the fiber detector is connected to the pulse laser, the detection laser, and The dual-wave mixing optical interferometer, the detection laser is further connected to the dual-wave mixing optical interferometer; the front end of the data acquisition and control card is connected to the dual-wave mixing optical interferometer, and the data acquisition And the back end of the control card is connected to the computer.
- 如权利要求1所述的一种激光超声金属材料残余应力的无损测量设备，其特征在于：A non-destructive measuring device for residual stress of a laser ultrasonic metal material according to claim 1, wherein:所述脉冲激光器和检测激光器采用脉宽10ns、波长1064nm的Nd：YAG激光器。The pulsed laser and the detecting laser employ a Nd:YAG laser having a pulse width of 10 ns and a wavelength of 1064 nm.
- 如权利要求2所述的一种激光超声金属材料残余应力的无损测量方法及设备，其特征在于：A non-destructive measurement method and apparatus for residual stress of a laser ultrasonic metal material according to claim 2, wherein:所述数据采集及控制卡是基于PC-DAQ数据采集系统。The data acquisition and control card is based on a PC-DAQ data acquisition system.
- 一种根据权利要求1-3任意一项所述的激光超声金属材料残余应力的无损测量方法，其特征在于所述方法包括如下步骤：A non-destructive measurement method for residual stress of a laser ultrasonic metal material according to any one of claims 1 to 3, characterized in that the method comprises the following steps:所述脉冲激光器激励产生超声波，所述检测激光器用于发射检测激光，超声波遇到残余应力后，经反射返回样品表面，引起表面形变，检测激光遇到形变的样品表面，返回的激光信号会发生变化，经所述双波混频光学干涉仪进行检测后，产生缺陷信号，通过所述数据采集及控制卡送入计算机中进行处理，建立双波混频激光超声测量金属材料残余应力计算模型，再经过LabVIEW检测软件反演为样品内部的残余应力值，以曲线成像的方式显示在计算机屏幕上。The pulsed laser is excited to generate ultrasonic waves, and the detecting laser is used to emit a detecting laser. After the ultrasonic wave encounters residual stress, it is reflected back to the surface of the sample to cause surface deformation, and the detecting laser encounters the deformed sample surface, and the returned laser signal occurs. The change is detected by the dual-wave mixing optical interferometer, and a defect signal is generated, which is sent to a computer for processing by the data acquisition and control card, and a double-wave mixing laser ultrasonic measurement method for calculating a residual stress of the metal material is established. It is then inverted by the LabVIEW detection software to the residual stress value inside the sample, which is displayed on the computer screen in the form of curve imaging.
- 根据权利要求4所述的方法，其特征在于：The method of claim 4 wherein:所述双波混频激光超声测量金属材料残余应力计算模型如下：The double-wave mixing laser ultrasonic measurement of the residual stress calculation model of the metal material is as follows:从光折变晶体中衍射出来的光信号表示为：The optical signal diffracted from the photorefractive crystal is expressed as:
公式中，AR表示振幅，ωopt为参考光的角频率，φ(t)为受动态光栅调制后相位，γ、α、L分别表示为光折变晶体的增益、吸收系数和长度；In the formula, A R represents the amplitude, ω opt is the angular frequency of the reference light, φ(t) is the phase modulated by the dynamic grating, and γ, α, and L are respectively expressed as the gain, absorption coefficient and length of the photorefractive crystal;信号光通过光折变晶体时，没有受到衍射光的干扰，这样信号光表示为：When the signal light passes through the photorefractive crystal, it is not interfered by the diffracted light, so the signal light is expressed as:
信号光束与参考光束相互干涉后，经光电变换器输出的信号为：After the signal beam and the reference beam interfere with each other, the signal output through the photoelectric converter is:公式中，
为超声残余应力信号振动引起的相位变化量；由公式(3)可以得出，输出的信号与残余应力超声的位移成正比，可以利用光强信号计算出超声在试块中运动的时间，进而获取出残余应力信号的时间点，就可以计算出试块中残余应力的确切位置。 formula,
The amount of phase change caused by the vibration of the ultrasonic residual stress signal; it can be concluded from the formula (3) that the output signal is proportional to the displacement of the residual stress ultrasonic wave, and the light intensity signal can be used to calculate the time of the ultrasonic motion in the test block, and further The exact position of the residual stress in the test block can be calculated by taking the time point of the residual stress signal.
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