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Quantitative diagnosis method of beam defects based on laser Doppler non-contact random vibration measurement
摘要： The beam structure is prone to defect damage during its use, and the rapid quantitative diagnosis of the beam structure can detect the defects of the beam in real time and quantitatively. In this article, the method of obtaining the vibration time-domain signal under random excitation of beam structure is proposed by using random vibration excitation and Laser Doppler principle. Based on this, the defect quantitative identification algorithm of beam structure is proposed based on fast Fourier, continuous wavelet transform and convolutional neural network. The random vibration of different parts of steel beams with artificial defects is measured by Laser Doppler method. The experimental results show that the defect size of the beam structure can be effectively identified only by the random vibration signal of the finite point. The method is expected to help to develop an online real-time assessment instrument for beam structure defects in service state.
关键词： Continuous wavelet transform,Beam defects,Laser Doppler,Non-contact random excitation,Quantitative diagnosis,Convolutional neural network
更新于2025-09-11 14:15:04
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Characterizing the Complex Modulus of Asphalt Concrete Using a Scanning Laser Doppler Vibrometer
摘要： Asphalt mixtures are the most common types of pavement material used in the world. Characterizing the mechanical behavior of these complex materials is essential in durable, cost-effective, and sustainable pavement design. One of the important properties of asphalt mixtures is the complex modulus of elasticity. This parameter can be determined using different standardized methods, which are often expensive, complex to perform, and sensitive to the experimental setup. Therefore, recently, there has been considerable interest in developing new, easier, and more comprehensive techniques to investigate the mechanical properties of asphalt. The main objective of this research is to develop an alternative method based on an optical measurement technique (laser Doppler vibrometry). To do this, a frequency domain system identification technique based on analytical formulas (Timoshenko’s beam theory) is used to determine the complex modulus of asphalt concrete at its natural frequencies and to form their master curve. The master curve plotted by this method is compared with the master curve obtained from the standard four-point bending test, and it is concluded that the proposed method is able to produce a master curve similar to the master curve of the standard method. Therefore, the proposed method has the potential to replace the standard stiffness tests. Furthermore, the standard stiffness methods usually conduct experiments up to the maximum frequency of 30 Hz. However, the proposed method can provide accurate complex modulus at high frequencies. This makes an accurate comparison between the properties of the asphalt mixtures in high frequencies and the development of more accurate theoretical models for simulation of specimens possible.
关键词： laser Doppler vibrometry,asphalt mixtures,modal analysis,complex modulus,master curve,non-destructive testing
更新于2025-09-11 14:15:04
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On the Application of Laser Vibrometry to Perform Structural Health Monitoring in Non-Stationary Conditions of a Hydropower Dam
摘要： This paper presents the ?rst application of the Laser Doppler Vibrometer (LDV) in non-stationary conditions within a hydropower plant powerhouse. The aim of this research is to develop a methodology to include non-contact vibration monitoring as part of structural health monitoring of concrete dams. We have performed in-situ structural vibration measurements on the run-of-the-river Bre?ice dam in Slovenia during the start-up tests and regular operation. In recent decades, the rapid development of laser measurement technology has provided powerful methods for a variety of measuring tasks. Despite these recent developments, the use of lasers for measuring has been limited to sites provided with stationary conditions. This paper explains the elimination of pseudo-vibration and measurement noise inherent in the non-stationary conditions of the site. Upon removal of the noise, fatigue of the different structural elements of the powerhouse could be identi?ed if signi?cant changes over time are observed in the eigenfrequencies. The use of laser technology is to complement the regular monitoring activities on large dams, since observation and analysis of integrity parameters provide indispensable information for decision making and maintaining good structural health of ageing dams.
关键词： concrete dam,dam monitoring,laser doppler vibrometry,vibration,accelerometers
更新于2025-09-11 14:15:04
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[IEEE 2019 41st Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) - Berlin, Germany (2019.7.23-2019.7.27)] 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - A System for Combined Laser Doppler Flowmetry and Microelectrode Recording during Deep Brain Stimulation Implantation
摘要： Microelectrode recording (MER) and intraoperative test stimulations are commonly used during stereotactic implantation of deep brain stimulation (DBS) electrodes but they can increase the risk of hemorrhage. The aim of the study is to present and evaluate a system combining laser Doppler flowmetry (LDF) and MER. An optical probe was designed with an inner metal tube for the microelectrode. Calibration of the MER-LDF probe in a standard microsphere solution showed expected LDF pattern. No interferences of the MER probe with the LDF signals could be observed. LDF was also acquired in one Parkinson patient undergoing DBS implantation. LDF data were obtained along the precalculated trajectory i.e. from cortex towards the target in the subthalamic nucleus (STN). Results demonstrated the technical feasibility of the combined MER-LDF probe during in-vitro experiences and in one patient. The perfusion signal representing the microcirculation showed stable values with clear peaks from each heartbeat. This agreed with previous investigation using an optical probe without the MER function. Due to the forward-looking probe design, this new technology has a high potential to avoid vessels during MER recording. In addition, it could be possible to detect changes in microcirculatory blood flow during stimulation.
关键词： stereotactic surgery,Microelectrode recording,laser Doppler flowmetry,deep brain stimulation,microcirculation
更新于2025-09-11 14:15:04
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Different lasers reveal different skin microcirculatory flowmotion - data from the wavelet transform analysis of human hindlimb perfusion
摘要： Laser Doppler flowmetry (LDF) and reflection photoplethysmography (PPG) are standard technologies to access microcirculatory function in vivo. However, different light frequencies mean different interaction with tissues, such that LDF and PPG flowmotion curves might have distinct meanings, particularly during adaptative (homeostatic) processes. Therefore, we analyzed LDF and PPG perfusion signals obtained in response to opposite challenges. Young healthy volunteers, both sexes, were assigned to Group 1 (n = 29), submitted to a normalized Swedish massage procedure in one lower limb, increasing perfusion, or Group 2 (n = 14), submitted to a hyperoxia challenge test, decreasing perfusion. LDF (Periflux 5000) and PPG (PLUX-Biosignals) green light sensors applied distally on both lower limbs recorded perfusion changes for each experimental protocol. Both techniques detected the perfusion increase with massage, and the perfusion decrease with hyperoxia, in both limbs. Further analysis with the wavelet transform (WT) revealed better depth-related discriminative ability for PPG (more superficial, less blood sampling) compared with LDF in both challenges. Spectral amplitude profiles consistently demonstrated better sensitivity for LDF, especially regarding the lowest frequency components. Strong correlations between components were not found. Therefore, LDF and PPG flowmotion curves are not equivalent, a relevant finding to better study microcirculatory physiology.
关键词： Laser Doppler flowmetry,perfusion,photoplethysmography,wavelet transform,microcirculatory function
更新于2025-09-11 14:15:04