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A New Approach to Guided Wave Ray Tomography for Temperature-Robust Damage Detection Using Piezoelectric Sensors
摘要： In this paper, a new approach to guided wave ray tomography for temperature-robust damage detection with time-of-flight (TOF) temperature compensation is developed. Based on the linear relationship between the TOF of a guided wave and temperature, analyses show that the TOF of the baseline signal can be compensated by the temperature measurement of the inspected materials without estimating the temperature compensation parameters. The inversion is based on the optimization of the TOF misfit function between the inspected and compensated baseline TOFs of the guided waves, and is applied by the elastic net penalty approach to perform thickness change mapping in a structural health monitoring (SHM) application. Experiments that are conducted in isotropic plates by piezoelectric sensors demonstrate the effectiveness of the proposed method. According to the results, our approach not only eliminates the artefacts that are caused by a temperature variation from 25 ?C to 70 ?C but also provides more accurate and clearer imaging of damage than conventional ray tomography methods.
关键词： TOF,ray tomography,piezoelectric sensors,guided wave,structural health monitoring,temperature compensation
更新于2025-09-23 15:21:21
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A criterion of the vertical spacing between fluorescent molecules in a waveguide structure
摘要： We demonstrate a method to discriminate the vertical spacing of ?uorescent molecules in a guided mode structure. A function that depends only on depth and wavelength is constructed to detect the axial position of a pair of ?uorescent molecules, which is especially suitable for the measurement of microstructure gaps and is not a?ected by the di?raction limit. Since directional ?uorescence radiation information can be collected from the back focal plane in a leakage radiation microscope, we can utilize the appropriate emission angles and corresponding waveguide modes. The relative position of the ?uorescent molecules is calculated by analyzing the intensity ratio between modes emission, so as to determine the vertical distance between the molecules.
关键词： Leakage radiation microscopy,Guided wave coupling emission,Molecular spacing,Surface plasmons
更新于2025-09-23 15:19:57
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An ultra-stable 2.9 μm guided-wave chip laser and application to nano-spectroscopy
摘要： We present a configurable guided-wave planar glass-chip laser that produces low-noise and high-quality continuous-wave laser emission tunable from 2.82 to 2.95 μm. The laser has a low threshold and intrinsic power and mode stability attributable to the high overlap of gain volume and pump mode defined by an ultrafast laser inscribed waveguide. The laser emission is single transverse-mode with a Gaussian spatial profile and M2 x,y ～ 1.05, 1.10. The power drift is ～0.08% rms over ～2 h. When configured in a spectrally free-running cavity, the guided-wave laser emits up to 170 mW. The benefit of low-noise and stable wavelength emission of this hydroxide resonant laser is demonstrated by acquiring high signal-to-noise images and spectroscopy of a corroded copper surface film with corrosion products containing water and hydroxide ions with a scattering-scanning near-field optical microscope.
关键词： ultra-stable,continuous-wave laser emission,guided-wave chip laser,nano-spectroscopy,mid-infrared
更新于2025-09-16 10:30:52
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Design of a remote and integrated Sagnac interferometer that can generate narrowband guided wave through the use of laser and effective optics to detect defects occurred in plates
摘要： To inspect the integrity of specimens that are moving or no space available to mount sensors on their surfaces, laser generated guided wave (GW) becomes the only feasible option. However, conventional GW generated by laser-based emission is in broadband frequency range. Hence, unwanted GW modes, along with the emitted desired GW mode, also get produced simultaneously to the inspected specimen. The results generated from reflected GW become chaotic, making the identification of GW signals truly reflected by defects very difficult. Hence, substantial research efforts have been spent on reducing unwanted GW modes by spatially modulating the laser pattern to emit narrowband GW. Previous methods to generate narrowband GW include the use of slit mask, diffractive grating, lenticular array, and interference of laser beam. Among these techniques, each has certain shortcomings. A recent research achievement is the design of the integrated optical Mach-Zehnder system (IOMZ) (J. Chen et al, Opt. Lett., 42, 4255, 2017). It can emit desired narrowband Lamb wave into the aluminum plate by using pulsed laser and the designed optical system. Although the results showed IOMZ’s ability in emitting narrowband GW mode, significant unwanted noise was also generated, making the signal-to-noise ratio (SNR) of the received GW signals rather low. In this study a new optical system to overcome the shortcoming of the above reported devices is proposed. It is called integrated Sagnac interferometer-based optical system (SIOS) which can minimize generation of unwanted noise and substantially improve the SNR of reflected GW signals. A comparison study is also presented to illustrate the effectiveness of SIOS is superior to that of the IOMZ. Experimental results reveal that the proposed SIOS is promising for remote nondestructive testing and evaluation.
关键词： Non-destructive testing,Laser,Optical systems,Narrowband laser generated ultrasound,Guided wave,Optical Sagnac interferometer
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing LLC 41ST ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Volume 34 - Boise, Idaho (20–25 July 2014)] - Feasibility of PZT ceramics for impact damage detection in composite structures
摘要： Fiber reinforced plastic composites are becoming widely used in vehicles and airframe structures due to their high strength to weight ratio. However unlike metals, the multilayered composite structures are more susceptible to damage mechanisms such as disbonds and delaminations due to impacts. It is often dif?cult to visually detect the damage. Lead-Zirconate-Titanate (PZT) thin ?lms are becoming popular for in-situ structural health monitoring due to their small size, high piezoelectric coupling coef?cient, and ease of surface-mounting and/or embedding in composite structures. A network of such transducers could be utilized for damage detection using guided wave techniques, impedance techniques, or passive impact detection techniques. However, the PZT ?lms are subject to the same impact probabilities that the structure encounters. If the transducers fail due to the subjected impacts, they can result in false readings and ultimately failing to correctly detect damage in the structure. This paper presents a feasibility study using the guided wave S0 mode for detecting impact damage. The health of the structure is quanti?ed using guided wave measurements, and the PZT health is monitored using impedance methods.
关键词： impact damage detection,impedance techniques,PZT ceramics,composite structures,guided wave techniques
更新于2025-09-10 09:29:36