Guided Lamb waves for identification of damage in composite structures: A review

The investment in an automated fabric defect detection system is more than economical when reduction in labor cost and associated benefits are considered. The development of a fully automated web inspection system requires robust and efficient fabric defect detection algorithms. The inspection of real fabric defects is particularly challenging due to the large number of fabric defect classes, which are characterized by their vagueness and ambiguity. Numerous techniques have been developed to detect fabric defects and the purpose of this paper is to categorize and/or describe these algorithms. This paper attempts to present the first survey on fabric defect detection techniques presented in about 160 references. Categorization of fabric defect detection techniques is useful in evaluating the qualities of identified features. The characterization of real fabric surfaces using their structure and primitive set has not yet been successful. Therefore, on the basis of the nature of features from the fabric surfaces, the proposed approaches have been characterized into three categories; statistical, spectral and model-based. In order to evaluate the state-of-the-art, the limitations of several promising techniques are identified and performances are analyzed in the context of their demonstrated results and intended application. The conclusions from this paper also suggest that the combination of statistical, spectral and model-based approaches can give better results than any single approach, and is suggested for further research.

/pdf/computer-vision-based-fabric-defect-detection-a-survey-27mr8b2pf3.pdf

Computer-Vision-Based Fabric Defect Detection: A Survey

This paper investigates various approaches for automated inspection of textured materials using Gabor wavelet features. A new supervised defect detection approach to detect a class of defects in textile webs is proposed. Unsupervised web inspection using a multichannel filtering scheme is investigated. A new data fusion scheme to multiplex the information from the different channels is proposed. Various factors interacting the tradeoff for performance and computational load are discussed. This scheme establishes high computational savings over the previously proposed approaches and results in high quality of defect detection. Final acceptance of visual inspection systems depends on economical aspects as well. Therefore, a new low-cost solution for fast web inspection is also included in this paper. The experimental results conducted on real fabric defects for various approaches proposed in this paper confirm their usefulness.

/pdf/defect-detection-in-textured-materials-using-gabor-filters-519irthzwt.pdf

Defect detection in textured materials using Gabor filters

Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications.

This review of process analytical chemistry is an update to the previous review on this subject published in 1995(A2). The time period covered for this review includes publications written or published from late 1994 until early 1999, with the addition of a few classic references pointing to background information critical to an understanding of a specific topic area. These older references have been critically included as established fundamental works. New topics covered in this review not previously treated as separate subjects in past reviews include sampling systems, imaging (via optical spectroscopy), and ultrasonic analysis.

/pdf/process-analytical-chemistry-1edp1w106r.pdf

Process Analytical Chemistry

An ultrasonic viscometer and method for measuring fluid viscosity are provided. Ultrasonic shear and longitudinal waves are generated and coupled to the fluid. Reflections from the generated ultrasonic shear and longitudinal waves are detected. Phase velocity of the fluid is determined responsive to the detected ultrasonic longitudinal waves reflections. Viscosity of the fluid is determined responsive to the detected ultrasonic shear waves reflections. Unique features of the ultrasonic viscometer include the use of a two-interface fluid and air transducer wedge to measure relative signal change and to enable self calibration and the use of a ratio of reflection coefficients for two different frequencies to compensate for environmental changes, such as temperature.

Method for measuring liquid viscosity and ultrasonic viscometer

An in-line viscometer is valuable to the control of a flow process, particularly a non-Newtonian flow because its viscosity is shear-rate dependent and thus requires continuous monitoring Currently available in-line viscometers are mostly of the probe design [1] and may obstruct the flow pattern, causing plugging problem in flows with suspended particles A probe-type viscometer generally measures a response of fluid density-viscosity product To separate mass loading and viscous effects, Kim and Bau [2] used a dual-probe design based on torsional wave speed and attenuation measurements However, no commercial system has been developed from their concept Another limitation of existing probe-type viscometers is the range of application, primarily in the low-viscosity range

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2168&context=qnde

An in-Line Ultrasonic Viscometer

This current report is a summary of information obtained in the "Information Capture" task of the US DOE-funded "Under Sodium Viewing (USV) Project" The goal of the multi-year USV project is to design, build, and demonstrate a state-of-the-art prototype ultrasonic viewing system tailored for periodic reactor core in-service monitoring and maintenance inspections The study seeks to optimize system parameters, improve performance, and re-establish this key technology area which will be required to support any new US liquid-metal cooled fast reactors

/pdf/under-sodium-viewing-a-review-of-ultrasonic-imaging-26r7rabh34.pdf

Under-Sodium Viewing: A Review of Ultrasonic Imaging Technology for Liquid Metal Fast Reactors

A unified analytical treatment is presented supported by extensive numerical illustrations of the interactions of ultrasonic waves with piezoelectric anisotropic plates. The plates are allowed to possess up to monoclinic anisotropic symmetry and associated piezoelectric coupling. The plates are also assumed to be immersed in water and subjected to incident acoustic beams at arbitrary polar and azimuthal angles. Simple analytical expressions for the reflection and transmission coefficients are derived, from which all propagation characteristics are identified. Such expressions contain, as a by‐product, the secular equation for the propagation of free harmonic waves on the piezoelectric plates. This equation is written in simple and completely separate terms pertaining to symmetric and antisymmetric modes. It is found that piezoelectric coupling, as well as water, influence both types of modes. Higher symmetry, such as orthotropic, transverse isotropic, and cubic, are contained implicitly in this analysis. ...

The influence of piezoelectricity on free and reflected waves from fluid‐loaded anisotropic plates

We investigated 94 GHz millimeter-wave (MMW) scattering from neutral and charged water mist produced in the laboratory with an ultrasonic atomizer. Diffusion charging of the mist was accomplished with a negative ion generator (NIG). We observed increased forward- and backscattering of MMW from charged mist, as compared to MMW scattering from an uncharged mist. In order to interpret the experimental results, we developed a model based on classical electrodynamics theory of scattering from a dielectric sphere with diffusion-deposited mobile surface charge. In this approach, scattering and extinction cross-sections are calculated for a charged Rayleigh particle with effective dielectric constant consisting of the volume dielectric function of the neutral sphere and surface dielectric function due to the oscillation of the surface charge in the presence of applied electric field. For small droplets with radius smaller than 100 nm, this model predicts increased MMW scattering from charged mist, which is qualitatively consistent with the experimental observations. The objective of this work is to develop indirect remote sensing of radioactive gases via their charging action on atmospheric humid air.

Hual-Te Chien

Papers

Method for measuring liquid viscosity and ultrasonic viscometer

An in-Line Ultrasonic Viscometer

Under-Sodium Viewing: A Review of Ultrasonic Imaging Technology for Liquid Metal Fast Reactors

The influence of piezoelectricity on free and reflected waves from fluid‐loaded anisotropic plates

Millimeter-wave scattering from neutral and charged water droplets