Ultrasonic Spectroscopy Methods Research Articles

An ultrasonic study of the effect of uniaxial green compaction pressure on the elastic anisotropy of porous copper fabricated using the pore-former route

Porous copper is potentially very attractive for various functional applications such as filters and heat exchanger materials. Within the scope of this study, porous copper samples with dual pore morphologies were fabricated following the space holder technique using a 1:2 mixture ratio of K2CO3 to NaCl as pore formers. The initial compaction pressure required for green body fabrication was systematically varied between 120 and 180 MPa, and the influence of this pressure over porosity, pore morphology, volume shrinkage, and longitudinal elastic constants was systematically studied. Three longitudinal elastic constants of the porous Cu samples were determined following the non-destructive ultrasonic phase spectroscopy method through the measurement of the phase shift vs. frequency spectra along the three orthogonal directions in each sample. When the applied pressure is increased from 120 to 160 MPa and the Cu:PF mixture ratios are 70:30 and 60:40, respectively, the elastic constant values in the green compaction direction (C11) decrease from 34.2 GPa to 7.5 GPa and 23.7 GPa–17.9 GPa. However, for Cu:PF mixture ratios of 70:30 and 60:40, under 180 MPa green compaction pressure C11 increases to 30.9 GPa and 21.2 GPa, respectively. As the applied green compaction pressure increased from 120 to 160 MPa, the samples' average elastic anisotropy ratio initially increased from 0.29 to 0.59 and then decreased to 0.55 at 180 MPa pressure. While the initial increase in anisotropy is due to increased pore flattening with increasing green compaction pressure, the decrease in anisotropy ratio in the samples fabricated under 180 MPa green compaction pressure is due to enhanced sample densification. Contour maps for different properties have been proposed to identify the optimum combination of initial powder composition and green compaction pressure for the intended end application.

Development of a Novel Ultrasonic Spectroscopy Method for Estimation of Viscosity Change during Milk Clotting.

Ultrasonic testing is an emerging non-destructive testing technology with high repeatability and precision. Milk is a very complex liquid and the change of its viscosity is a highly relevant property throughout conversion into other dairy products. In the following paper, we propose a novel method for the monitoring of viscosity during enzymatic milk clotting by ultrasonic spectroscopy. An ultrasonic transducer–receiver couple with a 250 kHz nominal frequency was submerged in the samples and an enveloped sweep (“chirp”) signal was applied in a through-transmission mode. Simultaneously, the change in viscosity was measured with a rotational viscometer at a constant shearing speed. The data were analyzed with an algorithm developed by the authors for spectral ultrasonic testing. Estimations yielded a high adjusted R2 (0.963–0.998) and low cross-validated estimation error (RPD: 4.38–14.22), suggesting that the method is suitable for industrial use given the right instrumentation.

Detection of Reinforced Concrete Thermal Damage by Nonlinear Ultrasonic Spectroscopy

Nonlinear Ultrasonic Spectroscopy (NUS) methods investigates nonlinear phenomena that occur when the sound or ultrasound waves pass through the material. This paper focuses on the use of these methods for nondestructive testing of reinforced concrete damaged by high temperature. For this research, reinforced concrete beams with one steel rod were made and the NUS measuring equipment was assembled. An appropriate nonlinear parameter was selected to assess the damage. The nonlinear behavior of thermally damaged reinforced concrete was manifested by the deformation of ultrasound waves passing through the measured samples, resulting in nonlinear effects in the frequency spectra of the recorded signal.

Technological features of receiving and research of high density ceramic materials on the basis of silicon carbide

The article is devoted to the establishment of regularities of synthesis and technological aspects of the formation of composite ceramics based on silicon carbide and aluminum nitride by the method of hot pressing, as well as the study of its structural properties. The paper presents the results of the study of the microstructure and elastic properties of ceramics based on silicon carbide, obtained by hot pressing at temperatures up to 2170 K and pressures up to 35 MPa, of various compositions (0.9SiC - 0.1AlN; 0.7SiC - 0.3AlN; 0.5SiC - 0.5AlN; 0.3SiC - 0.7AlN; 0.1SiC - 0.9AlN), the average density of which is 3.21 g/cm3. The microstructure of the obtained samples was studied with a scanning electron microscopy. Elastic moduli of SiC-AlN hot-pressed ceramic materials were determined by the method of resonant ultrasonic spectroscopy (RUS) depending on the composition. Our data on Poisson’s ratio are in good agreement with the literature data and are well described by linear approximation. The values of Young’s modulus are noticeably lower than the literature ones. The values of the elastic moduli lie below the additive right line of ceramic SiC and AlN with zero porosity, which is related to the influence of the porosity of our samples.

アミン応力腐食割れ先端領域の挙動と超音波スペクトロスコピー法による測定に関する研究

In conventional linear ultrasonic flaw detection method, since an ultrasonic wave incident on a steel material is excited at an interface having a difference in acoustic impedance, opening crack can be detected. However, the backscattered waves at ultrasonic spectroscopy method (noise) is the most suitable for detecting and evaluating precursory minute defect size of deterioration damage to equipment along with aging of amine stress corrosion cracking. This approach focuses on power spectrum intensity of a specific frequency band, to grasp precursor behavior by comparing area values of the power spectral intensity is confirmed with an actual device, and thus life expectancy can be predicted.

実機における水素誘起割れの経年劣化挙動と計測としての超音波スペクトロスコピー法の研究

実機における水素誘起割れの経年劣化挙動と計測としての超音波スペクトロスコピー法の研究

The Application of NUS Method for Concrete-Covered Steel Corrosion Monitoring

The corrosion of steel elements in reinforced concrete can cause considerable damage to civil engineering structures. Early detection of corrosion is therefore very important. Steel in concrete is protected if the concrete pH is higher than 9.6. Carbonated concrete, unfortunately, has a lower pH and this causes that the unprotected steel reinforcement begins to corrode. Nonlinear ultrasonic spectroscopy (NUS) methods shows potential to be very reliable to identify the structure defects in a wide range of materials. These methods are based on the fact that crack-induced nonlinearity makes a sensitive material impairment indicator. This paper describes the ability of one of NUS methods for monitoring steel corrosion in reinforced concrete. It studies nonlinear interaction between elastic waves and structural defects caused by corrosion of steel in concrete. For research we used concrete beams with ten millimetres thick steel rods. These beams were exposed to accelerated degradation by chlorides. The paper presents the initial results of our research.

Monitoring of the Damage in Stone Blocks by Means of Non-Destructive Methods

This paper deals with the damage assessment in stone blocks dismantled from a historic bridge construction. Nonlinear ultrasonic spectroscopy and impact echo methods were used for evaluating the stone block integrity structure. Harmonic analysis of the sample response on well defined ultrasonic excitation was used in the case of nonlinear ultrasonic method application. The amplitude dependent spectral changes of the probing signals were measured in the damaged blocks. Measurement results showed that the analysis of amplitude dependent spectral changes is a promising method for the damage assessment in structures. The Impact-Echo method is a technique for detecting defects in material structure such as stone blocks. It is based on monitoring the propagation of elastic waves from a short-duration mechanical impact. The aim of this paper is to provide an overview of the technique and to discuss the important parameters involved in this type of testing. The impact echo method is used to generate low-frequency stress waves from 500 Hz to 50 kHz that propagate into the structure and are reflected by defects and external surfaces.

Characterization of full set material constants of piezoelectric materials based on ultrasonic method and inverse impedance spectroscopy using only one sample

The most difficult task in the characterization of complete set material properties for piezoelectric materials is self-consistency. Because there are many independent elastic, dielectric, and piezoelectric constants, several samples are needed to obtain the full set constants. Property variation from sample to sample often makes the obtained data set lack of self-consistency. Here, we present a method, based on pulse-echo ultrasound and inverse impedance spectroscopy, to precisely determine the full set physical properties of piezoelectric materials using only one small sample, which eliminated the sample to sample variation problem to guarantee self-consistency. The method has been applied to characterize the [001]C poled Mn modified 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystal and the validity of the measured data is confirmed by a previously established method. For the inverse calculations using impedance spectrum, the stability of reconstructed results is analyzed by fluctuation analysis of input data. In contrast to conventional regression methods, our method here takes the full advantage of both ultrasonic and inverse impedance spectroscopy methods to extract all constants from only one small sample. The method provides a powerful tool for assisting novel piezoelectric materials of small size and for generating needed input data sets for device designs using finite element simulations.

Quantitative analysis of the influence of voids and delaminations on acoustic attenuation in CFRP composites by the laser-ultrasonic spectroscopy method

The aim of the present work is to develop the ultrasonic spectroscopy method using laser thermoelastic generation and piezoelectric detection of broadband acoustic pulses for quantitative evaluation of the influence on the ultrasonic attenuation coefficient of microscopic dispersed voids and interply delaminations in CFRP laminates. The specimens under study have different entire porosity values up to 10% determined by the X-ray computer tomography. The ultrasonic attenuation resonance is observed in all specimens governed by their periodic layered structure. The absolute maximum and the frequency bandwidth of the resonance peak depend on the total porosity level formed by the predominant type of imperfections, either of only microscopic spheroidal voids entrapped in the epoxy layers or of additional extended interply delaminations. The derived empirical relations between these parameters and the total porosity level can be used for rapid nondestructive evaluation of the structure of CFRP composite laminates subject to different manufacturing conditions.

Monitoring of the Damage Evolution in Reinforced Concrete Girder by Means of Nonlinear Elastic Wave Spectroscopy

Nonlinear elastic wave spectroscopy (NEWS) is a package of advanced methods of ultrasonic spectroscopy which make it possible to capture with a high level of sensitivity the formation and development of structure damage even in materially, as well as geometrically, highly complicated specimens. Concrete and reinforced concrete are classical examples of materials to which the application of conventional ultrasonic methods is very complicated. This is why they make an ideal medium for the application of non-linear ultrasonic methods. The object of this experimental study consists of the application of nonlinear ultrasonic testing to assess the structural integrity of a reinforced concrete girder which was extracted from a bridge structure during the reconstruction of the bridge. The girder was tested in three stages: prior to loading, in the course of loading, and when the loading had been completed, with the aim of identifying the parameters correlating with the girder structure integrity damage. Two nonlinear ultrasonic spectroscopy methods were applied, namely, employing one and two harmonic signals. Frequency spectra of the transmission responses were analyzed. Defects occurring in the structure under investigation give rise to heavy nonlinear effects accompanying the propagation of elastic waves, which, in the singlesignal excitement case took effect in emphasizing the odd-numbered harmonic components among the newly generated frequencies. Therefore, the amplitudes of the latter were evaluated. In the other case, two ultrasonic signals of close frequencies were applied and their difference components were evaluated. Structure integrity damage was identified in the girder by means of the frequency spectrum analysis.

NDT of Mechanical Damaged Concrete Specimens by Nonlinear Acoustic Spectroscopy Method

Current research and development of non-linear ultrasonic spectroscopy methods shows these methods to be very promising for material testing and defectoscopy in the near future. Our experiments focused on the testing of lightweight concrete specimens using the single-frequency excitation method. We studied the concrete specimens' structure after having been stressed by a mechanical force. Measurements were realized before and after mechanical loading.

NDT of Reinforcement Corrosion Using Ultrasonic Spectroscopy

Corrosion of built-in steel reinforcement ranks among the most serious mechanisms of bridge structure degradation. There are many reasons for the corrosion to occur: failures occurring during the bridge construction, consequences of traffic load, or, simple, ageing of the structures. Visual inspection of a bridge provides general information on the bridge condition. However, it cannot provide any information on the internal structure and integrity of the reinforced concrete or pre-loaded elements of the bridge in question. This is why non-destructive diagnostic methods are acquiring growing importance, helping researchers to properly evaluate the condition of a bridge and decide upon the most convenient methods for maintenance, repair or refurbishment of the bridge in question or its parts and schedule them accordingly.In this domain, methods employing the non-linear acoustic spectroscopy (NEWS - Nonlinear Elastic Wave Spectroscopy) achieved rush advancement recently. They are based on the fact that a non-linearity, which is due to the presence of a defect, makes an extraordinary indicator of the structure damage. These new, non-destructive methods appear to be promising for application to a wide range of materials featuring relatively heavy non-homogeneities, and for a large span of sites, from micro-chip to bridge structures. The present paper deals with an experimental study of the application of non-linear ultrasonic spectroscopy methods to the detection of steel reinforcement corrosion and its consequences for reinforced concrete specimens subjected to corrosion induced degradation cycles.

Elastic constants identification of anisotropic composite rectangular parallelepipeds

For many years, composite materials have been investigated due to their potential in many applications such as nuclear fuel. Nowadays, the improvement of structure conception and simulation requires many reliable properties, especially the entire elastic tensor. For these reasons, the implementation of simulation and characterization methods adapted to the geometry of samples and the high anisotropy degree of such materials are then crucial issues to developers and end users. The work presented here reports first macroscopic properties of two composites Duralumin/Air and Duralumin/Tungsten Carbide) calculated using periodical homogenization method from elastic constants of each phase measured by high frequency acoustic microscopy. Then a resonant ultrasonic spectroscopy method is used to identify the entire elastic tensor. First, computation predicting the resonant frequencies and the mode shapes of free vibrations of cubes are presented. Excitation is then ensured by ultrasonic transducers and detection is performed by means of a laser vibrometer. A fit process of the theoretical frequencies on the measured data is then described. This method allows us to conclude about the accuracy of the homogenization method.

Detecting Damage in Composite Material Using Nonlinear Elastic Wave Spectroscopy Methods

Modern aerospace structures make increasing use of fibre reinforced plastic composites, due to their high specific mechanical properties. However, due to their brittleness, low velocity impact can cause delaminations beneath the surface, while the surface may appear to be undamaged upon visual inspection. Such damage is called barely visible impact damage (BVID). Such internal damages lead to significant reduction in local strengths and ultimately could lead to catastrophic failures. It is therefore important to detect and monitor damages in high loaded composite components to receive an early warning for a well timed maintenance of the aircraft. Non-linear ultrasonic spectroscopy methods are promising damage detection and material characterization tools. In this paper, two different non-linear elastic wave spectroscopy (NEWS) methods are presented: single mode nonlinear resonance ultrasound (NRUS) and nonlinear wave modulation technique (NWMS). The NEWS methods were applied to detect delamination damage due to low velocity impact (<12 J) on various composite plates. The results showed that the proposed methodology appear to be highly sensitive to the presence of damage with very promising future NDT and structural health monitoring applications.

Complete Characterization of Porous Piezoelectric Ceramics Properties Including Losses and Dispersion

In this paper a line of porous piezoelectric ceramics with 3-0/3-3 connectivity types and porosity up to 70% was systematically studied. Complex sets of elastic, dielectric and piezoelectric coefficients of the porous piezoelectric ceramics were measured by ultrasonic and impedance spectroscopy methods using Piezoelectric Resonance Analysis (PRAP) software. Finite element modeling (FEM) of effective constants of the porous piezoelectric ceramics was performed using ANSYS software package. Critical comparison of numerical FEM calculations with the results of various approximated formulas, unit cell models, and experimental data for different porous piezoelectric ceramics was carried out.

Stiffness evaluation of contacting surfaces by bulk and interface waves

This paper describes ultrasonic measurements of normal and tangential stiffnesses of the contacting interface between polished aluminum blocks subjected to nominal contact pressures up to about 3.8 MPa. These stiffnesses were evaluated by ultrasonic spectroscopy methods for the bulk (longitudinal and transverse) wave reflection coefficients and the anti-symmetric mode interface wave velocity. The measurements revealed the interfacial stiffnesses as functions of the frequency as well as the applied contact pressure. The ratio of the tangential and normal stiffnesses is discussed in the light of foregoing theoretical and experimental findings. Furthermore, possible explanations for the frequency dependence of the measured stiffnesses are reviewed, invoking the spatial inhomogeneity of the interfacial stiffness as well as its lossy nature.

Ultrasonic Spectroscopy for the Identification of Defects and Environmental Disturbances

Ultrasonic health monitoring of structures under realistic operating conditions is very difficult because ultrasonic waves are influenced by not only structural defects but also environmental disturbances. We examined a method of ultrasonic spectroscopy in this investigation to classify signal changes as either structural or experimental. We used aluminum plates to investigate the ultrasonic propagation characteristics with respect to the growth of defects (fatigue cracks, slits, and drilled holes) and the change in environmental disturbances (water drops, temperature, and load). The frequency dependency of the propagation delays and amplitudes of tone-burst waves differed for defects and environmental disturbances. Defects could be distinguished from environmental disturbances by monitoring the delay-amplitude plot lines of the tone-burst waves with increasing frequency.

Characterization of the Structure of Perfluorinated Ionomers Dispersed in Aqueous and Alcoholic Solutions Using Ultrasonic Attenuation Spectroscopy Method

not Available.

Ultrasonic Spectroscopy for the Identification of Defects and Environmental Disturbances

Ultrasonic health monitoring of structures under realistic operating conditions is very difficult because ultrasonic waves are influenced by not only structural defects but also environmental disturbances. In this investigation, we examined the method of ultrasonic spectroscopy to classify the signal changes as “structural” or “experimental”. Using aluminum plates, the ultrasonic propagation characteristics against the growth of defects (fatigue crack, slit and drilled hole) and the change in the environment disturbances (water drop, temperature and load) was investigated. The frequency dependency of both propagation delays and amplitudes of tone-burst waves were different from each other for defects and environmental disturbances, and it was found that defects could be distinguished from the environmental disturbances by monitoring the delay-amplitude plot lines of the tone-burst waves with increasing frequency.