Investigation of Different Features for Baseline-Free RAPID Damage-Imaging Algorithm Using Guided Waves Applied to Metallic and Composite Plates.

In guided-wave-based damage-imaging algorithms, damage reconstruction typically involves comparing the signals with and without a defect. However, in many cases, defect-free data may not be available. Therefore, in this study, baseline and baseline-free approaches were used for damage imaging, exploiting not only the amplitude of the signal as the feature but also five additional features, namely, the amplitude of the sparse signal after deconvolution, the amplitude of the coefficients at the excitation frequency from the re-assigned short-time Fourier transform, the time of flight determined from cross-correlation, kurtosis in the time domain, and kurtosis in the frequency domain.

Determining the Elastic Constants of Isotropic Materials by Measuring the Phase Velocities of the A and S Modes of Lamb Waves.

In this study, a new method for determining the elastic constants of isotropic plates using Lamb wave fundamental modes is presented. This method solves the inverse problem, where the elastic constants (Young's modulus and Poisson's ratio) of the plate were estimated by measuring the phase velocities of the Lamb wave using the Rayleigh-Lamb equations to find the solution and determining the phase velocities of the A and S modes using a new method. The suitability of the proposed method for determining the elastic constants was evaluated using simulated and experimental signals propagating on an aluminum plate.

Detection and Classification of Uniform and Concentrated Wall-Thinning Defects Using High-Order Circumferential Guided Waves and Artificial Neural Networks.

Pipeline structures are susceptible to corrosion, leading to significant safety, environmental, and economic implications. Existing long range guided wave inspection systems often fail to detect footprints of the concentrated defects, which can lead to leakage. One way to tackle this issue is the utilization of circumferential guided waves that inspect the pipe's cross section.

Development and Investigation of High-Temperature Ultrasonic Measurement Transducers Resistant to Multiple Heating-Cooling Cycles.

Usually for non-destructive testing at high temperatures, ultrasonic transducers made of PZT and silver electrodes are used, but this could lead to damage to or malfunction of the ultrasonic transducer due to poor adhesion between PZT and silver. Soldering is one of the most common types of bonding used for individual parts of ultrasonic transducers (protector, backing, matching layer, etc.), but silver should be protected using additional metal layers (copper) due to its solubility in solder.

Excitation and Reception of Higher-Order Guided Lamb Wave's and Modes in Plastic and Composite Materials.

Contemporary technologies are employing composite plate materials developed by using various innovative materials (nanostructures, mica structures, etc.). Application of higher-order modes could allow better detection and characterization of defects characteristic of planar plastic and composite structures, mainly due to shorter wavelength.

Comparative Analysis of Ultrasonic NDT Techniques for the Detection and Characterisation of Hydrogen-Induced Cracking.

The article is devoted to the investigation of ultrasonic inspection techniques suitable for detecting hydrogen-induced cracking (HIC) and a high-temperature hydrogen attack (HTHA), which are of great importance in petrochemical and refinery industries. Four techniques were investigated: total focusing method (TFM), advanced velocity ratio (AVR) measurement, advanced ultrasonic backscatter technique (AUBT) and time of flight diffraction method using ultra low angle ultrasonic transducers (TULA). The experimental investigation has been carried out on two carbon steel samples cut off from a heat exchanger of an oil refinery and potentially affected by HIC.

Numerical Analysis of Guided Waves to Improve Damage Detection and Localization in Multilayered CFRP Panel.

Multilayered carbon fiber-reinforced polymers (CFRP) are increasingly used in aircraft components because of their superior mechanical properties. However, composite materials are vulnerable to impact loads, resulting in delamination-type damage which, if unnoticed, could lead to catastrophic structural failure. The objective of this research was to investigate possibilities to improve damage detection and the localization using signal processing methods.

Guided Wave Phase Velocity Dispersion Reconstruction Based on Enhanced Phased Spectrum Method.

Fibre-reinforced composite laminates are frequently used in various engineering structures, due to their increased weight-to-stiffness ratio, which allows to fulfil certain regulations of CO emissions. Limited inter-laminar strength makes composites prone to formation of various defects, which leads to progressive degradation of residual strength and fatigue life of the structure. Using ultrasonic guided waves is a common technique for assessing the structural integrity of composite laminates.

Novel Processing Algorithm to Improve Detectability of Disbonds in Adhesive Dissimilar Material Joints.

Adhesively bonded dissimilar materials have attracted high interest in the aerospace and automotive industries due to their ability to provide superior structural characteristics and reduce the weight for energy savings. This work focuses on the improvement of disbond-type defect detectability using the immersion pulse-echo ultrasonic technique and an advanced post-processing algorithm. Despite the extensive work done for investigation, it is still challenging to locate such defects in dissimilar material joints due to the large differences in the properties of metals and composites as well as the multi-layered structure of the component.

Detection and Localization of Partial Discharge in Connectors of Air Power Lines by Means of Ultrasonic Measurements and Artificial Intelligence Models.

According to the statistics, 40% of unplanned disruptions in electricity distribution grids are caused by failure of equipment in high voltage (HV) transformer substations. These damages in most cases are caused by partial discharge (PD) phenomenon which progressively leads to false operation of equipment. The detection and localization of PD at early stage can significantly reduce repair and maintenance expenses of HV assets.

Analysis of Wave Patterns Under the Region of Macro-Fiber Composite Transducer to Improve the Analytical Modelling for Directivity Calculation in Isotropic Medium.

Analytical modelling is an efficient approach to estimate the directivity of a transducer generating guided waves in the research field of ultrasonic non-destructive testing of the large and complex structures due to its short processing time as compared to the numerical modelling and experimental techniques. The wave patterns or the amplitude variations along the region of ultrasonic transducer itself depend on its behavior, excitation frequency, and the type of propagating wave mode. Depending on the wave-pattern of a propagating wave mode, the appropriate value of the amplitude correction factor must be multiplied to the amplitudes of the excitation signal for the accurate evaluation of directivity pattern of the ultrasonic transducers generating guided waves in analytical modelling.

Attenuation of a Slow Subsonic A Mode Ultrasonic Guided Wave in Thin Plastic Films.

The ultrasonic testing technique using Lamb waves is widely used for the non-destructive testing and evaluation of various structures. For air-coupled excitation and the reception of A mode Lamb waves, leaky guided waves are usually exploited. However, at low frequencies (<100 kHz), the velocity of this mode in plastic and composite materials can become slower than the ultrasound velocity in air, and its propagation in films is accompanied only by an evanescent wave in air.

Ultrasonic non-destructive testing of complex titanium/carbon fibre composite joints.

Ultrasonic inspection is widely used for non-destructive evaluation of composite adhesive joints. However, there are serious challenges in applying ultrasonic testing on metal to composite hybrid joints, because they are multi-layered, made out of dissimilar materials and relatively thin. The ultrasonic signals reflected by different layers are overlapped, scattered and attenuated.

Air-Coupled Excitation of a Slow A₀ Mode Wave in Thin Plastic Films by an Ultrasonic PMN-32%PT Array.

Ultrasonic non-destructive testing techniques (NDT) based on the application of guided waves are already used for inspection of plate-type structures made of various materials, including composite materials. Air-coupled ultrasonic techniques are used to test such structures by means of guided waves. The objective of this research was development and investigation of air-coupled excitation of a slow A₀ Lamb wave mode in thin plastic films by a PMN-32%PT ultrasonic array.

2D Analytical Model for the Directivity Prediction of Ultrasonic Contact Type Transducers in the Generation of Guided Waves.

In this paper, a novel 2D analytical model based on the Huygens's principle of wave propagation is proposed in order to predict the directivity patterns of contact type ultrasonic transducers in the generation of guided waves (GWs). The developed model is able to estimate the directivity patterns at any distance, at any excitation frequency and for any configuration and shape of the transducers with prior information of phase dispersive characteristics of the guided wave modes and the behavior of transducer. This, in turn, facilitates to choose the appropriate transducer or arrays of transducers, suitable guided wave modes and excitation frequency for the nondestructive testing (NDT) and structural health monitoring (SHM) applications.

A novel ultrasonic method for evaluation of blood clotting parameters.

Purpose: For long time, blood clot retraction was measured only by thromboelastographic or platelet contractile force measurement techniques. The purpose of the present study was development of a novel ultrasonic method based on simultaneous monitoring of variations in the ultrasound velocity and the frequency spectrum of the signal propagating in clotting blood and its application for automatic evaluation of blood clotting parameters.

Methods: Simultaneous measurement of ultrasound velocity and variations in the frequency spectrum of wideband ultrasonic signals in clotting blood samples was performed.

Influence of the Spatial Dimensions of Ultrasonic Transducers on the Frequency Spectrum of Guided Waves.

Ultrasonic guided wave (UGW)-based condition monitoring has shown great promise in detecting, localizing, and characterizing damage in complex systems. However, the application of guided waves for damage detection is challenging due to the existence of multiple modes and dispersion. This results in distorted wave packets with limited resolution and the interference of multiple reflected modes.

Micromachining and validation of the scanning acoustic microscope spatial resolution and sensitivity calibration block for 20-230 MHz frequency range.

Scanning acoustic microscopy (SAM) is used as a routine non-destructive test tool for different diagnostic examinations: detection of defects such as microcracks, delamination, disbonding, inclusions, subsurface features in materials such as pores and cracks. SAM can be operated in a wide frequency range from Megahertz to Gigahertz. SAM measurement spatial resolution is diffraction limited by the wavelength of the acoustic wave in particular medium and also depends on individual transducers geometry.

Propagation of Ultrasonic Guided Waves in Composite Multi-Wire Ropes.

Multi-wire ropes are widely used as load-carrying constructional elements in bridges, cranes, elevators, . Structural integrity of such ropes can be inspected by using non-destructive ultrasonic techniques. The objective of this work was to investigate propagation of ultrasonic guided waves (UGW) along composite multi-wire ropes in the cases of various types of acoustic contacts between neighboring wires and the plastic core.

Ultrasonic Technique for Density Measurement of Liquids in Extreme Conditions.

An ultrasonic technique, invariant to temperature changes, for a density measurement of different liquids under in situ extreme conditions is presented. The influence of geometry and material parameters of the measurement system (transducer, waveguide, matching layer) on measurement accuracy and reliability is analyzed theoretically along with experimental results. The proposed method is based on measurement of the amplitude of the ultrasonic wave, reflected from the interface of the solid/liquid medium under investigation.

Measurement of viscosity of highly viscous non-Newtonian fluids by means of ultrasonic guided waves.

In order to perform monitoring of the polymerisation process, it is necessary to measure viscosity. However, in the case of non-Newtonian highly viscous fluids, viscosity starts to be dependent on the vibration or rotation frequency of the sensing element. Also, the sensing element must possess a sufficient mechanical strength.

High temperature ultrasonic transducers for imaging and measurements in a liquid Pb/Bi eutectic alloy.

In some nuclear reactors or accelerator-driven systems (ADS) the core is intended to be cooled by means of a heavy liquid metal, for example, lead-bismuth (Pb/Bi) eutectic alloy. For safety and licensing reasons, an imaging method of the interior of ADS, based on application of ultrasonic waves, has thus to be developed. This paper is devoted to description of developed various ultrasonic transducers suitable for long term imaging and measurements in the liquid Pb/Bi alloy.