Acoustic Nondestructive Methods Research Articles

Monitoring degradation in alkaline-activated slag materials

This paper deals with determining degradation changes in alkaline-activated slag-based building materials. It describes methods for determining dynamic elastic moduli obtained by acoustic non-destructive methods, including the ultrasonic pulse method and the resonance method. A finegrained mortar was chosen as the initial mix for the implementation of the experiment, the binder part of which was sodium hydroxide-activated blast-furnace granulated slag. Beams with dimensions of 40 × 40 × 160 mm were chosen as test bodies, for which acoustic non-destructive methods monitored changes in the material structure during degradation processes.

The Cold-Brittleness Regularities of Low-Activation Ferritic-Martensitic Steel EK-181

The behavior of the EK-181 low-activation ferritic-martensitic reactor steel (Fe–12Cr–2W–V–Ta–B) in the states with different levels of strength and plastic properties after traditional heat treatment (THT) and after high-temperature thermomechanical treatment (HTMT) in the temperature range from −196 to 25 °C, including the range of its cold brittleness (ductile–brittle transition temperature, DBTT) is studied. The investigations are carried out using non-destructive acoustic methods (internal friction, elasticity) and transmission and scanning electron microscopy methods. It is found that the curves of temperature dependence of internal friction (the vibration decrement) of EK-181 steel after THT and HTMT are similar to those of its impact strength. Below the ductile–brittle transition temperature, it is characterized by a low level of dislocation internal friction. The temperature dependence curves of the steel elastic modulus increase monotonically with the decreasing temperature. In this case, the value of Young’s modulus is structure-sensitive. A modification of the microstructure of EK-181 steel as a result of HTMT causes its elastic modulus to increase, compared to that after THT, over the entire temperature range under study. The electron microscopic studies of the steel microstructure evolution near the fracture surface of the impact samples (in the region of dynamic crack propagation) in the temperature range from −196 to 100 °C reveal the traces of plastic deformation (increased dislocation density, fragmentation of the martensitic structure) at all of the temperatures under study, including those below the cold brittleness threshold of EK-181 steel.

Guided waves in stratified media: Observing multiple Sezawa modes

Appearance of multiple Sezawa (M2,2) modes and the related interfacial Stoneley waves at propagation of Lamb wave in a stratified medium containing several layers obeying Wiechert condition is observed. Possible appearance of the multiple high frequency Stoneley and Sezawa modes may have importance in various applications starting from micro and nanomechanics to geophysics along with developing the nondestructive acoustic methods for qualitative and quantitative assessment of the high frequency asymptotics. The analysis is based on Cauchy sextic formalism.

Abnormal dispersion of fundamental Lamb modes in FG plates: II—symmetric versus asymmetric variation

A closed-form dispersion equation for Lamb waves propagating in functionally graded (FG) plates with arbitrary varying anisotropic physical properties in transverse direction is constructed by applying Cauchy sextic formalism. Comparative analyses of the dispersion curves related to the fundamental modes of homogeneous and FG plates reveal their substantial and visually detected differences even at sufficiently small transverse inhomogeneity. The observed discrepancy in dispersion curves may serve for developing acoustic nondestructive methods for determination of possible transverse inhomogeneity.

Improving the economic and operational reliability of the designed structures by improving the acoustic methods for diagnosing invisible material microdefects

AnnotationThe study aimed at increasing the economic and operational reliability of various designed building structures, improving non-destructive acoustic methods for detecting hidden microdefects in the materials used has been carried out. Construction, water, oil, gas pipelines must have the strength to ensure the trouble-free operation during the entire period of their operation, which determines the economic and operational reliability of structures. Strength can be significantly reduced if the latent microdefects are available in the material. In the field of such structural disturbances, material destruction, leading to loss of stability and bearing capacity of structural elements, accompanied by huge economic losses, environmental degradation and, in the worst case, human losses can develop. Therefore, it is necessary to improve the non-destructive acoustic methods for detecting latent microdefects. The mathematically refined models that describe the propagation of nonlinear deformation waves in thin-walled structural elements should be constructed for this. This is possible if the real physical and mechanical parameters, leading to more accurate characteristics of the deformation waves required for acoustic methods of the materials’ defectoscopy are taken into account. Such models include nonlinear mathematical models describing the propagation of deformation waves in rods and cylindrical shells, when the real hereditary properties of the material, the possibility of developing large deformations in them, and the effects lost in the framework of models that consider only the linearly elastic properties of structural elements are taken into account. Such a simplification causes unacceptable errors in the calculation of wave parameters and, accordingly, gives far-from-truth results of an acoustic study of the presence of invisible microdefects in the material of thin-walled structural elements that weaken their strength, and the economic and operational reliability of the designed structures and pipelines depends on it.

Assessing the Condition of the Material of Pressure Vessel after Their Long-Lasting Operation in the Petrochemical Industry Using Non-Destructive Acoustic Methods and Structural Stress Field Analysis

Assessing the Condition of the Material of Pressure Vessel after Their Long-Lasting Operation in the Petrochemical Industry Using Non-Destructive Acoustic Methods and Structural Stress Field Analysis

The Classification of Cracks Recorded during the Cyclic Loading of the Reinforced Concrete Beam by Acoustic Emission Method

Non-destructive testing is a process of inspecting, testing, and evaluating materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of a system or its part. The acoustic non-destructive methods are concerned with the state-of-the-art situation in the field of experimental studies of the physical properties of engineering materials. In this paper, the acoustic emission method was used for classification of cracks recorded during the cyclic loading of the reinforced concrete beam. Acoustic emission is a phenomenon of stress wave radiation caused by the dynamic reconstruction of material’s structure that accompanies processes of deformation and fracture. Crack propagation is one of the macroscopic sources of acoustic emission. Acoustic emission signals generated by different loading patterns can provide valuable information concerning the structural integrity of a material. Load levels that have been previously exerted on a material do not produce acoustic emission activity.

Assessment of the Protective Properties of Impact-Resistant Ceramic-Polymer Composites Using Acoustic Nondestructive Methods

The use of acoustic nondestructive methods was studied with the purpose of determining the composition and structure of protective ceramic-polymer composites according to the criteria of penetration resistance and protective barrier endurance. The methods of acoustic measurements were adapted to the characteristics possessed by groups of samples from the following materials: ceramics, polymer composites, honeycomb-structure materials, and ceramic-polymer composites. Stiffness, ρc2, was used as an informative parameter to define the elasticity of the materials in the direction of impact, and frequency drift was used as a measure of elastic wave dissipation. The measured acoustic characteristics of the samples were compared to the known criteria for penetration resistance of ceramics and the results of ballistic tests. The ceramic-polymer material with a gradient support demonstrated better ballistic endurance and lower after-penetration deformation. The material is recommended for the production of efficient impact-resistant composites possessing enhanced dissipative capabilities.

Nondestructive Testing of the Physicomechanical Properties of Zinc-Oxide Varistors Proposed by Different Manufacturers

We present the results of investigations by the nondestructive acoustic methods of the physicomechanical properties of zinc-oxide ceramic varistors produced by the leading foreign firms, such as ABB and Epcos, and the St.-Petersburg Plant of Energy-Protective Devices. We describe and discuss the results of application of this method for the determination of the properties of disk-shaped varistors with various diameter-to-height ratios. Note the range of particle dimensions of the powders used for the formation of varistors affects their physicomechanical properties.

Assessment of the Low-Cycle Strain-Induced Martensite Transformation in AISI 316 Stainless Steel by Magnetic and Acoustic Nondestructive Methods

The strain-induced martensite transformation during the low-cycle fatigue in austenitic AISI 316 stainless steel was investigated by magnetic and acoustic nondestructive methods. The low-cycle fatigue test was performed at various strain amplitudes. The volume fraction of α′-martensite was determined for the fatigue-failed specimens by magnetic property measurements with further microstructure detection. The cyclic hardening behavior was discussed in terms of the α′-martensite transformation. The volume fraction of α′-martensite was growing with the strain amplitude. An increase in the α′-martensite fraction was evaluated with the nonlinear ultrasonic parameter. The α′-martensite fraction may distort the lattice in austenitic stainless steel, resulting in the distortion of an ultrasonic wave. From this distortion, superharmonics may be generated with the α′-martensite nucleation, which strongly depends on the strain amplitude. The relationship between nonlinear acoustic characteristic and the volume fraction of α′-martensite is linear.

Assessment methodology of concrete crack resistance on cement binder

The study examines a methodology based on the assessment of factors which further influence properties of concrete, that is its physical and mechanical characteristics analysis. The methodology is based on the research results obtained in the Samara School of Material Engineering and previously developed by the authors themselves. Its essence is based on the study of concrete destruction processes with account of existing rules of fracture mechanics. The researchers merged the energy conception of A.A. Griffiths with the kinetic theory of S.N. Zhurkova and developed a mathematical apparatus capable of modeling the conditions of external influence on concrete. They also estimated "Rebindera effect" while applying external load from the described types of external influence. They determined three stages in the course of destruction development depending on quantity and quality of initial defects. The first stage of destruction occurs at the micro level, the destruction is negligible. At the second stage cracks begin to fuse and already influence on change of values of concrete stress-strain properties. Finally, the third stage is "direct fracture" when the main cracks are formed dividing the specimen into separate fragments not capable of carrying the external load. The work reveals parameters and divide them into two groups. These parameters have a significant influence on the nature and kinetics of the destruction processes, respectively. The authors introduce a criterion of concrete crack resistance named "the length of the reduced crack". This criterion represents the total length of all surfaces of destruction at a single width of a crack. The proposed method can be applied with the use of non-destructive acoustic methods and destructive mechanical methods. Approbation of this methodology showed sufficient reliability and authenticity of the proposed indicator as a criterion of crack resistance.

Complex characteristic for forecasting durability of hydraulic concrete

The paper analyzes operating conditions of hydraulic structures, as well as the main types of external influence with temperature and humidity variations. The purpose of the research is to highlight the main parameters which will be able to assess the actual durability of concrete hydraulic structures in the process of their design. The authors use methods developed in Samara Architecture and Civil Engineering Institute to determine concrete physical and mechanical characteristics. Thus, these methods help accurately assess concrete durability, frost resistance and water resistance. These methods are based on theoretical studies of the processes of concrete destruction by means of non-destructive acoustic methods. The the energy conception developed by A.A. Griffits and S.N. Zhurkova's kinetic serve as a scientific basis for the methods. Theoretical research and its analysis of concrete destruction processes from various kinds of external influence was confirmed by results of standard measurements. The research showed that durability of concrete, that is speed of its destruction, depended on two groups of physical and mechanical characteristics. One of the groups evaluates the initial structure of concrete, while the second group characterizes the speed of the material loading . The paper proposes a forecasting method of frost resistance and water-resisting properties of concrete according to its physical-mechanical characteristics. It also introduces an indicator of their assessment which is named the length of the reduced crack. The proposed indicator has a good correlation with frost resistance and water-resisting properties . Besides, the proposed method can be used not only in laboratory conditions, but also in construction production directly on the construction site.

The Assessment of Cement Mortars after Thermal Degradation by Acoustic Non-destructive Methods

Thanks, the terrorist attacks on the worldwide interest in the design of structures for fire greatly increased. One of the advantages of concrete over other building materials is its inherent fire-resistive properties. The concrete structural components still must be able to withstand dead and live loads without collapse even though the rise in temperature causes a decrease in the strength and modulus of elasticity for concrete and steel reinforcement. In addition, fully developed fires cause expansion of structural components and the resulting stresses and strains must be resisted. This paper reports the results of measurements by Impact-echo method and measurement by ultrasound. Both methods are based on the acoustic properties of the material which are dependent on its condition. These acoustic methods allow identifying defects and are thus suitable for monitoring the building structure condition. The results are obtained in the laboratory during the degradation of composite materials based on cement by high-temperature.

Перспективное устройство для измерения линейной и угловых составляющих малых перемещений поверхностей объектов контроля

Introduction. Measuring the linear and angular components of small displacements of the monitor object surfaces is considered. A high-precision non-contact device based on the advanced laser technologies and methods of optical interferometry, namely a double-pass laser interferometer with integrated branches, is developed to perform these measurements. The calculated and experimental validation of the device is offered. Thus, the quality and condition of the materials and products can be controlled by means of the acoustic non-destructive methods. Materials and Methods. New software and mathematical models describing optical fields of the interference patterns generated by the interferometer under consideration are offered. Various types of beam splitters and cases of polarization are used under the numerical simulation of the intensity distributions in the interference patterns. Research Results. New mathematical models and software for the numerical simulation of the optical radiation intensity fields in the interference patterns considering both linear and angular components of small displacement of the surface of the test object are developed. A new interference technique of measuring small linear and angular displacements is developed and theoretically grounded. It allows combining the meter measuring capabilities for both small linear and angular displacements of the monitor object surfaces in a single tool. New optical interference methods and means for the noncontact measurements of small linear and angular movements of the monitor object surfaces that implement the method capabilities and extend the functionality of the known indicators of small displacements are offered. Discussion and Conclusions. The obtained results can be used for the high-precision measurements of small linear and angular displacements of surfaces of the objects under control. Areas of application are the following: experimental research; assessment and diagnostics of the structural materials samples; investigations of fast wave processes in the layered structures of complex shape made of the anisotropic composite materials. The methods developed in this study are applicable in such industries as mechanical engineering, shipbuilding, aircraft engineering, instrument making, power engineering, and etc.

Non-destructive neural identification of the bond between concrete layers in existing elements

The paper presents the results regarding the identification of the value of the pull-off adhesion between a concrete added layer with a constant thickness and a substrate concrete layer in existing elements. A method of identification, which is based solely on the use of artificial neural networks (ANNs) and two non-destructive acoustic methods: impact-echo and impulse response on the surface of the added layer, was developed. The methodology of identifying the pull-off adhesion between a concrete added layer and a substrate layer in existing elements was developed and presented in the paper and is useful in construction practice.

Determination of Correlation between Destructive and Nondestructive Test Methods Applied on Modified Wood Exposed to Natural Weathering

The objective of this study was to determine a correlation between the dynamic modulus of elasticity (MOEd) and the static modulus of elasticity (MOEs), and to assess the potential of using nondestructive (NDT) methods as a grading tool for both treated and untreated wood exposed to weathering. In the experiment, test samples made from spruce and oak were exposed for four months to natural weathering. Half of the specimens were treated with a silicon-based nano-protection. The MOEd was determined using acoustic NDT methods–ultrasound transmission (MOEdu) and the vibration methods (MOEdv), while the MOEs was determined by a destructive three-point bending test. The results showed that there was no statistical significance for the influence of the time of exposure and the surface treatment on the modulus of elasticity. The ultrasound method, measured in the longest distance of the sample, had the most significant correlation with the MOEs. The vibration method also reached a similar correlation with the MOEs. The mean values of the MOEdu and MOEdv were higher than the MOEs. The influence of density on the acoustic wave velocity was not confirmed.

Non-Destructive Testing during the Hardening of Alkali-Activated Slag

Non-destructive acoustic analysis methods, Impact-echo method as a traditional and the Acoustic Emission method as nontraditional method for civil engineering, were 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 used 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.

Potential for the use of nondestructive acoustic methods of inspection for estimation of the physico-mechanical properties and quality of refractories1

Certain potential fields of application and the results of the use of acoustic low-frequency methods of nondestructive inspection of the physico-mechanical properties and quality of different types of refractory materials are presented. A description of the equipment and of the standards that regulate the use of nondestructive acoustic methods as regards inspection of refractory articles and corrosive tools in the course of their production and application is presented.

Predicting Wood Quality of Green Logs by Resonance Vibration and Stress Wave in Plantation-Grown Populus ×euramericana

A cost-effective estimation of wood quality of hardwood green logs is needed. The purposes of this study were to investigate and compare two nondestructive acoustic methods to predict the wood quality of green logs from a poplar I-72 (Populus xeuramericana cv. I-72/58 San Martino) plantation. After log measurements, small clear wood specimens were cut and air dried to 12 percent moisture content. The static bending modulus of elasticity (MOE) of small clear wood specimens was about 15 and 20 percent greater than the dynamic MOE of green logs based on resonance vibration (Efr) and stress wave (Esw). However, good correlations (R) between Efr and Esw of logs and bending MOE of 0.806 and 0.848 (P < 0.001), respectively, were observed. Significant correlations were also found between the Efr and Esw of logs and the modulus of rupture and compressive strength parallel to grain (sigmac) of small clear wood specimens (P < 0.001). The results indicate that both acoustic techniques were effective predictors of wood quality, although the stress wave method was found to be more accurate and reliable than the resonance vibration method. The longitudinal changes of strength properties with tree height could be tracked by these two methods.

Mechanical properties assessment of Cunninghamia lanceolata plantation wood with three acoustic-based nondestructive methods

The objectives of this study were to establish the method of evaluating wood mechanical properties by acoustic nondestructive testing at standing trees and at logs of a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantation, and to compare three acoustic nondestructive methods for evaluating the static bending modulus of elasticity (MOE), modulus of rupture (MOR), and compressive strength parallel-to-grain (σc) of plantation wood as well. Fifteen Chinese fir plantation trees at 36 years of age were selected. Each tree was cut into four logs, for which three values of dynamic modulus of elasticity, i.e., E sw, of the north and south face based on stress waves to assume the measuring state of the standing tree, E fr, longitudinal vibration, and E us, ultrasonic wave, were measured in the green condition. After log measurements, small specimens were cut and air-dried to 12% moisture content (MC). Static bending tests were then performed to determine the bending MOE and MOR, and compressive tests parallel-to-grain were made to determine σc. The bending MOE of small clear specimens was about 7.1% and 15.4% less than E sw and E us, respectively, and 11.3% greater than E fr. The differences between the bending MOE and dynamic MOE of logs as determined by the three acoustic methods were statistically significant (P < 0.001). Good correlation (R = 0.77, 0.57, and 0.45) between E sw, E fr, and E us and static MOE, respectively, were obtained (P < 0.001). It can be concluded that longitudinal vibration may be the most precise and reliable technique to evaluate the mechanical properties of logs among these three acoustic nondestructive methods. Moreover, the results indicate that stress wave technology would be effective to evaluate wood mechanical properties both from logs and from the standing tree.