Non-destructive Acoustic Method Research Articles

Development of a method for assessing the degree of hydrogenation of titanium alloy VT1-0 by acoustic method

In this paper, the possibilities of using a non-destructive acoustic method to determine the degree of hydrogenation of titanium alloy VT1-0 are investigated. The features of the use of various acoustic parameters for the construction of engineering techniques for determining the structural state of a titanium alloy at various stages of its hydrogenation are analyzed. A number of computational and experimental methods for determining the mass fraction of hydrogen in a titanium alloy are proposed, based on the use of its acoustic characteristics, which increase the accuracy and stability of the algorithms underlying the calculation part of the methods. The sources of errors of the proposed methods, the limits of their applicability, as well as the requirements for hardware and software for their implementation are analyzed. The results of acoustic measurements carried out on samples from the VT1-0 alloy are compared with the ideas about the patterns of its structural changes during its hydrogenation. The possibility of creating engineering algorithms for assessing the state of the material of products subjected to hydrogenation on the basis of experimental data obtained in order to prevent dangerous degradation of its operational properties is shown.

ON THE RECONSTRUCTION OF PRESTRESS FIELDS IN A HOLLOW CYLINDER

The present research is devoted to the development of the theoretical foundations of nondestructive acoustic method for identifying inhomogeneous prestress fields in a hollow cylinder, depending on the probing loading type. A linearized model of steady oscillations of an elastic body in the presence of an inhomogeneous prestress field of arbitrary nature is considered in the standard and weak formulations. On the basis of this model, we formulate a problem for a cantilever-clamped prestressed hollow cylinder that performs steady axisymmetric vibrations under three types of probing loading. A corresponding weak formulation of the problem in the cylindrical coordinate system is presented, in which six independent components of the prestress tensor are taken into account. At that, a case of prestress fields obtained by applying some initial mechanical external static load is considered. In the presence and absence of prestresses of various types, amplitude-frequency dependences are analyzed, and resonant and natural frequencies are found in a wide frequency range. Numerical calculations were carried out using the FEM on a non-uniform grid; mesh refinement is carried out in the vicinity of the boundary points, where the type of boundary conditions changes. Based on the numerical solution of an auxiliary set of direct problems, seven types of prestress fields are constructed, differing in the types of initial loading, most often encountered in practice. To assess the possibility of implementing the procedure for reconstructing prestresses of each of the considered types, a sensitivity analysis was additionally performed, which showed that for some prestress types there are frequencies and types of probing loading for which the presence of prestress is practically not manifested. The sensitivity analysis performed made it possible to implement the optimal method of probing loading when solving the inverse coefficient problem. The statement of the new inverse problem on the restoration of arbitrary inhomogeneous prestress fields in the considered finite hollow cylinder is formulated. When restoring the prestress of a given structure, the inverse problem is reduced to finding a set of parameters from an ill-conditioned algebraic system, which was studied with the help of the A.N. Tikhonov regularization method. Additional data for solving the inverse problem was obtained on the basis of probing both via a single load and via combined probing modes. It has been found that it is most effective to use a combined loading mode and use a sufficiently wide frequency range when selecting sounding frequencies. The results of computational experiments on the reconstruction of six components of the prestress tensor are presented and analyzed, and recommendations are proposed for choosing the optimal modes of acoustic sounding.

Study on Sound Propagation Performance of Mechanized Coal Gangue-Fine Sand Filling Body

In the process of continuous and high-intensity mining in soft rock coal mines, high-quality filling treatment is required for the goaf. A nondestructive acoustic velocimetry method is an excellent way to measure the quality of filling body to effectively maintain the rock stability of the mining area and decrease industrial solid waste. In this study, the gangue and fine sand are used as the filling aggregates, and the uniaxial compression test and acoustic wave test are conducted in the cementitious gangue-sand filling body with different gangue-sand ratio. The results show that the longitudinal wave velocity of the filling body is basically between 1.556 km/s and 2.413 km/s. When the gangue-sand ratio is small, and the slurry concentration is high, the early strength of the cementitious gangue-sand filling body is low, but the later strength has a good growth trend. For specimens with higher strength-filled bodies, the propagation speed of sound waves inside them is also faster, indicating a certain positive correlation between the strength of the filled body and the speed of sound waves. A mathematical equation using longitudinal wave velocity to predict the strength of filling body is established. This equation can be used to predict and judge the quality of the filling body in the mining area.

Self-Excited Acoustical System Frequency Monitoring for Refractory Concrete under Uniaxial Compression

The characterization of materials, stress and fatigue state monitoring based on the acoustoelastic principle are gaining widespread attention in recent years, mainly due to their advantages such as high sensitivity and non-destructive character. This article presents the application of a non-destructive acoustic method to test the degree of degradation of materials with which the heating boiler is coated. The combustion chamber is covered in materials when the temperature of the process itself increases, and has a very positive effect on fuel combustion. Unfortunately, with the passage of time, such materials undergo gradation. This article describes an innovative measuring system that has been successfully applied to monitor changes in resonance frequency under uniaxial compression in refractory grade material, which by definition is characterized by a high level of heterogeneity with a network of pre-existing cracks. The paper indicates that both stress and elasticity coefficients have an impact on the vibration frequency of the measuring system. Initial research was conducted to qualitatively determine the influence of these parameters on the measured frequency of the system.

Параметры акустической неоднородности для неразрушающей оценки влияния технологии изготовления и эксплуатационной поврежденности на структуру металла

In this paper, we propose a non-destructive acoustic method for assessing microstructural alterations produced in metals as a result of processing and exploitation damage. The method is based on measuring ratios of longitudinal and shear ultrasound waves velocities with subsequent normalization of these ratios to their counterparts corresponding to a “baseline state” of the metal. The choice of the baseline state depends of the particular problem and corresponds to either the pre-exploitation metal state for the object to be monitored, or the state of reference samples, for which the strength characteristics fall into acceptable range according to the results of conventional strength-evaluation methods. For the introduced Microstructure-Sensitive Acoustic parameters (MSA-parameters) characterizing alterations in the metal microstructure, we discuss the reasons of the difference between the baseline and current states of the metal in terms of the total values of the normal and tangential compliances imparted to the metal due to the appearance of microstructural heterogeneities. The efficiency of utilization of the proposed acoustic diagnostic parameters is demonstrated using experimental data for two types of metal samples with essentially different microstructure (isotropic and anisotropic heterogeneity). Measurements of the proposed microstructure-sensitive acoustic parameters can be used in a variety of applications: (i) non-destructive quality control of manufacturing technologies in metallurgy and mechanical engineering (ii) evaluation of damage accumulation during exploitation manufactured constructions/samples; (iii) evaluation of mechanical properties, fracture resistance and other physical parameters of metals.

Evaluation of quality changes and elasticity index of kiwifruit in shelf life by a nondestructive acoustic vibration method

Abstract A nondestructive acoustic vibration method combined with kinetic models was used to evaluate the quality changes and elasticity index (EI) of kiwifruit in shelf life in this study. The kiwifruit was stored at 0, 4, 10 or 20 °C. On each test day, the elasticity index of the kiwifruit was measured by the nondestructive acoustic vibration method. Then, the samples were measured by the puncture test and sensory evaluation. The results showed that EI and the quality indices changed gradually during storage and were significantly affected by the storage temperature. Moreover, EI correlated well with the tissue strength and sensory indices. Different kinetic models were used to fit the change in EI. The results showed that the first-order kinetic model had a better performance (with R2 values of 0.986∼0.997 and RMSE values of 0.009–0.019 kHz2 kg2/3) than the zero- and second-order kinetic models. The temperature dependence of the reaction rate (k) of EI was further modelled by the Arrhenius model. The Arrhenius model showed good performance for modelling k as a function of temperature (R2>0.99). The first-order kinetic model combined with the Arrhenius model was used to evaluate quality changes and EI for kiwifruit. The results showed that the errors between the predicted and experimental values of EI were within 12%, indicating the established model could be used for the evaluation of quality changes and EI of kiwifruit. This study provides a nondestructive method for evaluating the quality changes and EI of kiwifruit in shelf life.

Sensitivity Assessment of the Nonlinear Resonant Ultrasonic Spectroscopy for Concrete Damage Detection

Nonlinear Resonant Ultrasound Spectroscopy is a nondestructive acoustic method which is able to measure the bulk hysteretic nonlinearity. This method monitors the shift of the resonant frequency in response of variations in the excitation frequency amplitudes. Measurements were performed on concrete samples exposed to temperatures of 200, 400, 600, 800, 1000, 1200 °C. The elastic modulus values are given to compare the Nonlinear Resonant Ultrasound Spectroscopy (NRUS) sensitivity. These are calculated from the measured velocities of ultrasonic pulses (linear acoustic method) and from the bulk density. The strengths of the samples obtained by destructive methods are also given. Based on these results, the NRUS method can be described as a very sensitive indicator of damage in concrete.

Acoustic Determination of Properties Possessed by Porous Titanium

To impart the optimal structure to a powder material and promote high mechanical properties, the production process is to be monitored at each step using nondestructive methods. Acoustic methods are believed to be promising in this respect. The parameters of acoustic fields are influenced by many factors that determine the structure and properties of powder materials. A relevant task is to improve acoustic methods for the identification and use of this influence. A model material is taken as an example to show the capabilities of a nondestructive acoustic method relying on integrated measurement of the propagation velocities of longitudinal, transverse, and rod elastic waves in studying the patterns peculiar to the powder structurization at the molding and sintering stages. The following problems that can be solved using this method are considered and experimentally confirmed: identify how the properties of the starting powders influence the characteristics of the final material, monitor the compaction and contact formation processes in the material, and identify features of these processes, which are manifested as uneven distribution of properties over the material and aftereffects and are stepwise. Additional criteria are proposed to increase the reliability and descriptiveness of the results. Analysis of the experimental data shows that the propagation velocities of bulk and rod elastic waves in different ways reflect the compaction and contact formation in powder materials. The differences are explained by the peculiarities of acoustic fields generated by various types of elastic waves.

Effect of Thermal Loading on Selected Parameters of Reinforced Concrete Obtained by Acoustic NDT Method

The paper presents the results of experiments carried out on test samples made from reinforced concrete. Within this experiment, concrete beams with steel reinforcement in the middle were made. The concrete samples were tested by a non-destructive acoustic Impact-echo method before and after high temperature loading (after cooling to room temperature). We focused on the dominant frequencies shift in the frequency spectra obtained by this method. The aim was to assess the ability of aforementioned acoustic method to detect the thermal damage of steel reinforced concrete.

Does Thinning Intensity Affect Wood Quality? An Analysis of Calabrian Pine in Southern Italy Using a Non-Destructive Acoustic Method

In the middle of XIX century, Calabrian pine was planted in southern Italy to increase the forest cover in mountainous areas. Many of these forest stands were never managed, since they were considered non-profitable for wood production. Therefore, in order to promote timber value, it is fundamental to study, more deeply, the characteristics and management options for this species. The acoustic technologies applied to predict the mechanical and physical properties of timber are well-established practices in forest research. In this study, we hypothesized that the tree stand density could influence the dynamic modulus of elasticity (MOEd) and, therefore, the future wood quality. We specifically aimed to verify if different management options, when applied, could influence the timber quality of Calabrian pine growing in similar environmental conditions. The study was conducted in the Aspromonte National Park (Calabria, Southern Italy). We derived the MOEd values from data obtained by the acoustic velocity measured through the TreeSonic™ timer. Calabrian pine trees were selected in stands where different intensities of thinning were applied eleven years before this study began (no thinning, thinning 25%, thinning 50%, and thinning 75%). The percentage refers to the number of trees cut with respect to the total number of occurring trees. The analyses were conducted on a total of 804 trees (201 trees for each intensity of thinning). A strong positive correlation was observed between the acoustic velocity, the thinning treatments and diameter at breast height (DBH). The thinning realized at 25% induced better tree wood quality. We also analyzed the best predictors for MOEd estimation, using variables easily measurable in the field, such as tree diameter, tree height, or their transformations (number of trees per hectare, basal area per hectare). We provide, here, a useful tool for predicting the wood stiffness in relation to stand parameters easily measurable in forest inventories.

The defect detection algorithm that combined spectrum entropy with vibrational energy ratio for acoustic inspection method

We have studied the non-contact and non-destructive acoustic inspection method using airborne sound wave and a laser Doppler vibrometer. Internal defects (crack, peeling etc.) of concrete near the surface are excited by vibrational energy of acoustic radiation. The resonance frequency of flexural vibration of the defect (inside to depth 8-10 cm) of concrete can be measured. By our technique, a non-destructive test is possible from a long distance more than 5 m max to 30 m. The two-dimensional vibration velocity data are measured and processed numerically. An image of the defect is reconstructed by vibrational energy ratio. There was a problem of an optical noise resulting from the leakage of light reception depending on surface state of concrete. To solve it, we introduced “Spectrum Entropy.” The data under influence of an optical noise show a frequency characteristic similar to a white noise. Spectrum entropy is calculated as an information entropy and express white nature of a signal. Therefore, we propose an algorithm that combines spectrum entropy with vibrational energy ratio. Our technique was applied to an experiment with a real concrete structure (bridge). The defective part was extracted as an image and the validity of our method was confirmed.

The non-contact acoustic inspection method for concrete structures using the defect detection algorithm based on the statistic evaluation for a healthy part of concrete

The deterioration of concrete structure becomes a social problem in Japan. Social needs increase as for maintenance, check and renewal of concrete structures such as a tunnel or a bridge. The check of concrete structures has been performed conventionally by a hammering test. Not the inspection depended on a human experience and sense, but the inspection by a quantitative measuring system are demanded. We have developed the technique “non-contact nondestructive acoustic inspection method” to measure the internal defects near the concrete surface to a depth of about 10cm using airborne sound and the laser Doppler vibrometer at a distance 5―10 m far from measurement surface. Depending on the surface state (reflectance, dirt, etc.) of concretes, there is a problem to decrease the quantity of the light of the returning laser and there arise optical noise resulting from the leakage of light reception. To remove an abnormal measurement point, we proposed a defect detection algorithm, in which vibrational energy ratio and spectrum entropy are combined. As a result, it enables to distinguish a defect part, healthy part and an abnormal measurement point. However, for a real concrete structure, the gray area exists. We evaluate quantity of acoustic characteristics against a healthy part of concrete statistically. We found the distribution of each acoustic characteristic against a healthy part follow a normal distribution by excluding some outlier. A defective part is separated from a healthy part clearly and visualized vividly.

Impact-Echo Method for Non-Destructive Testing of High-Temperature-Degraded Cement-Based Composite

Non-destructive acoustic analysis method Impact-echo method as a traditional method for civil engineering was used for this experiment. The paper deals with the applicability of Impactecho acoustic method to testing of cement-based composites prepared from a mix of cement mortar and quartz sand, which were intentionally degraded by high-temperature treatment (in the temperatures range from 200°C to 1200°C). The aim of this paper is introduce the effect of high-temperature degradation. An understanding of microstructure performance relationships is the key to true understanding of material behaviors. The results of non-destructive testing confirmed the different structure of mortar specimens. The subjected to high-temperatures led to absorption of lower frequencies as compared to the reference specimens. A significant decrease of the absorbed frequencies was observed, depending on temperature. The largest decrease occurred after the specimens exposure at 400-600 °C. The effect of heat exposure to the decrease of frequencies was mitigated to the temperature degradation 1200 °C.

The Influence of Curing and Process of Hydration to Damping Coefficient of Alkali Activated Slag Mortars

Non-destructive acoustic analysis method Impact-echo method as a traditional for civil engineering was used for experiment. This paper reports the experiment during hardening and drying of specimens of alkali activated slag mortars. Alkali activated slag is a material having a great potential to be used in practice. The main drawback of this material is a high level of autogenous and especially drying shrinkage, which causes a deterioration of the mechanical properties. The aim of this paper is introduce the effect of method curing of mortars and time curing on the microstructure of alkali activated slag mortars. An understanding of microstructure performance relationships is the key to true understanding of material behaviours.

Concerning the possibility of examining compressor blades according to attenuation and speed of ultrasound

Possibilities for studying the structural condition of the material, from which the operating blades of the axial compressor of a gas-turbine engine are made, are considered based on measuring ultrasound attenuation and speed. The results of measuring the propagation of pulses of longitudinal and elastic shear waves in the blade material after their operation and repair. The experimental studies are performed using an ultrasonic echo method. The potential of the nondestructive acoustic method of evaluating the structural state of corrosion resistant stainless steel after use, restorative repairs, and repeated use of the blades in the General Electric MS 5142 gas turbine engine of a GTK-25I gas compressor is presented.

Changes in Berry Firmness of Various Grape Cultivars on Vines Measured by Nondestructive Method before and after Veraison

Time-course changes in the elasticity index (EI) of 8 cultivars and 1 selection of grape berries on vines were investigated with a nondestructive acoustic method. A portable device was constructed for the measurement of grape firmness. The EI was determined by the formula EI = f22 · d2, where f2 and d were the second resonant frequency and the diameter of the sample respectively. In all cultivars, the date of veraison was judged by touch and the EI largely decreased around veraison. These changes were classified into two types; one decreased before veraison and the other after veraison. The EI was compared with the firmness measured by two penetration methods. Relationships between the EI and firmness measured by the penetration methods were classified into three types of regression curves; a linear relation which detected similar berry firmness with both the nondestructive method and the penetration methods; logarithmic, in which the nondestructive method was more sensitive when berries were hard; and exponential, in which the nondestructive method waas more sensitive when berries were soft. We concluded that these differences were caused by differences in the spatial softening process.

Measurement of ripening speed and determination of the optimum ripeness of melons by a nondestructive acoustic vibration method

The ripening speed of the melon cultivar ‘Miyabi-Haruaki’ was determined by monitoring its elasticity index (EI) with a nondestructive acoustic vibration method. EI was determined by the formula EI = f 2 2 ⋅ m 2 / 3 , where f 2 is the second resonance frequency of a melon sample, and m is the mass of the sample. The speed of ripening, i.e., ΔEI/day, was determined to be 0.36 × 10 4 kg 2/3 Hz 2 d −1, which was lower than the ripening speeds of previously studied melon cultivars ‘Andes’ and ‘Quincy’ (0.39 × 10 4 kg 2/3 Hz 2 d −1 and 0.50 × 10 4 kg 2/3 Hz 2 d −1, respectively). Using a sensory panel test, the period of optimum ripeness of the melons was determined to be 5.3–7.1 × 10 4 kg 2/3 Hz 2. Nondestructive determination of the period of optimum ripeness in terms of the EI can be useful for estimating the shelf-life of melons. In addition, by determining the ripening speed, the time required for a melon to reach optimum ripeness can be predicted.

A nondestructive acoustic method for estimating the residual stresses in a hardened layer

A theoretical model for estimating the residual stresses in a hardened layer of axially symmetric articles by a nondestructive acoustic method is considered. A technique of experimental investigations and an algorithm for estimating the residual stresses are presented. The envelope of a signal scattered by a structure and arising during propagation of ultrasonic waves in a hardened layer is qualitatively identified.

Non-destructive monitoring of the physicomechanical properties of zinc oxide varistors

Results are presented for a study of the physicomechanical properties of zinc oxide ceramic varistors produced by the St Petersburg ZAO Zavod Elektrozashchitnykh Ustroistv (ZAO ZEU) by a non-destructive acoustic method. With analysis of the results the desirability is demonstrated of using instruments for non-destructive monitoring in order to improve the quality of the ceramic varistors produced. The effectiveness is also established of using the method in question for determining the properties of developed larger diameter varistors.

Storage ability and differences of carrot varieties defined by firmness changes measured with new non-destructive acoustic method

Carrot production in Hungary is getting more important these days. The condition of the quality insurance is to choose the proper variety of carrot and store on optimal conditions therefore measuring firmness and matter parameters are very important. Four varieties of carrots were measured (Bangor, Olympus, Napa and I3olero). The roots were stored in unsealed polyethylene bags at 4-10 degrees Celsius and 95% relative humidity. The vegetables were measured three times: at harvest, after I .5 months of storage and after four months of storage. The samples were tested by non-destructive acoustic. Stillness measuring method during the 112 days experiment for firmness. In laboratory were measured weight loss, dry material -NO3 and sugar content as an important matter parameters.
 The firmness change as a function of storage time are the following: First part of the storage (after 60 days), the Napa variety changed least in the case of acoustical parameter, at the same time its weight Foss and dry material content were not rise significantly, while its sugar content increased with 50%. The l3olero variety had the highest changes of sugar content during storage. During the second storage period, the softening speed of all samples was increased. The Bolero had the highest average mass loss (32,7%) and NO3 content changes as well. All measurements showed the largest changes for the Bolero variety. The highest percentage of dry material content was found by the Bolero and Napa varieties (18-20%).
 In this experiment, we found that the Bolero variety showed the greatest loss in compressibility during storage. If both firmness and weight loss results are considered, the Napa variety is found to be the most storable variety in sort period. The Bangor variety was found to be the best for long-term storage.