Ultrasonic Nonlinearity Parameter Research Articles

Nitriding layer depth detection based on mixing frequency nonlinear ultrasonic parameters

Nitriding treatment can improve the surface properties of workpieces, thus increasing the service life of the workpiece. The depth of nitriding layer is not only one of the important indexes for evaluating the nitriding effect, but also an important factor affecting the end-use performance of the workpiece. While the existing hardness and metallographic methods cannot meet the needs for non-destructive testing of nitriding layer depth in shaft parts. Therefore, a method using non-linear ultrasonic testing technology is proposed for non-destructive evaluation of nitriding layer depth. In this study, 1045 steel shaft specimens with different nitriding layer depths were prepared by a liquid salt bath nitriding method. The total depth of the nitriding layer was measured using a microhardness tester, and metallographic microscopy was applied to observe microstructure changes before and after nitriding treatment. With the proposed non-destructive method, the longitudinal critically refracted (LCR) wave mixing detection model was established and the ultrasonic nonlinear coefficients were used for characterizing the nitrided layer depths. Experimental results show that the LCR wave sum frequency (LCRWSF) detection model better characterizes the nitriding layer depth of 1045 steel and has higher sensitivity. As a result, the LCRWSF model is more suitable to efficiently estimate the nitrided layer depth.

Determination of the softening point and temperature interval of asphalt mixture for the healing process based on the contactless nonlinear ultrasonic method

The softening point and gradient healing have significant engineering significance for the self-healing of asphalt mixtures. This study introduces a novel approach utilizing a contactless ultrasonic system in conjunction with the Second Harmonic Generation (SHG) technique to determine the softening point and monitor the gradient healing process of asphalt mixtures. Three distinct fracture patterns resulting from temperature variations are accurately characterized through simulation using the Discrete Element Method (DEM). The ultrasonic nonlinear parameter β, reflecting different crack interfaces, proves to be a highly effective alternative for characterizing asphalt fractures, outperforming traditional methods such as bearing force and wave velocity. In experimental analysis, variations in the healing index highlight the significant influence of asphalt mixture fracture patterns on healing efficiency. The observed decrease in ultrasound amplitude signifies the transition of the asphalt binder from a solid to a liquefied state, accompanied by an increase in the nonlinear parameter indicating enhanced plasticity. The softening point is precisely determined when the Rayleigh surface wave disappears. The cumulative healing process is visualized through the continuous decrease in the nonlinear parameter. To further enhance the understanding of the asphalt self-healing process, the internal temperature gradient field is characterized using the proposed energy difference method. A correlation between the nonlinear parameter and the depth of the temperature interval is established, providing a non-destructive method for evaluating the distribution of the temperature interval. This innovative approach significantly accelerates the development of non-destructive testing in the field of asphalt self-healing.

Quantification of tiny damage variation in asphalt mixture during the low-temperature thermal cycle

The performance evaluation of asphalt materials during low-temperature thermal cycles remains a challenge, particularly in quantifying the early tiny damage development and recovery processes. To address this issue, a high-sensitivity nonlinear ultrasonic method - the second harmonic generation (SHG) technique in the form of Rayleigh surface waves, is proposed to investigate these behaviors in asphalt mixture. The decrease in thermal contraction value and stiffness modulus with cycles verifies the damage behavior at the macro level. Turning points in crack length, crack density, and nonlinear parameter during the thermal cycle indicate the generation of cracks from − 20 ℃ to − 30 ℃ during the cooling process. The decrease of crack length and crack density in the heating phase demonstrates the recovery of asphalt. The nonlinear ultrasonic parameter β'(c) caused by crack is successfully separated from the total nonlinear parameter β', and the recovery index (RI)is defined to quantify the recovery behavior. Both of them are highly consistent with crack length and crack density. While the sensitivity index (SI) of nonlinear parameter is hundreds or thousands of times greater than other measurements of damage development. Furthermore, a qualitative correlation between the nonlinear parameters and plastic strain has been established. This breakthrough widens the scope of studying low-temperature weak damage in asphalt mixtures, moving beyond the confines of crack analysis.

Evaluation of high-temperature degradation of platen superheater tube in thermoelectric power plant using nonlinear surface ultrasonic waves

The operating conditions of Korean standard coal-fired thermal power plants involve high temperatures, with steam reaching approximately 540 °C. To support the life management of platen superheater (PSH) tubes, which operate under the highest temperature and pressure conditions among boiler tubes, various methods have been used. These methods include visual inspection, thickness measurement, and hardness measurement, which are typically used to conduct lifespan diagnosis on facilities that have been operating for more than 100,000 h or 20 y. This study examined the applicability of a nonlinear ultrasonic technique to evaluate the degradation damage of a PSH tube composed of X20CrMoV12.1 steel in a thermal power plant. The specimens of a PSH tube made of X20CrMoV12.1 steel that has been operating for approximately 20 y (160,000 h) in a Korean standard thermal power plant was obtained from three points, and the nonlinear surface ultrasonic wave was measured. Then, the results of the nonlinear ultrasound, microstructure analysis, and tensile test were compared. Based on where the boiler tube specimen was located, a strong correlation was observed between the ultrasonic nonlinearity parameter and changes in the tensile and yield strengths. These results confirm that the nonlinear ultrasonic method can be used to evaluate the changes in the mechanical properties affected by boiler tube degradation.

Fatigue damage assessment using nonlinear critically refracted longitudinal (LCR) wave in pure iron: Experiments and FEM

To achieve early-stage microstructure evolution assessment and damage monitoring of fatigue, a new thickness-independent and nondestructive method based on nonlinear critically refracted longitudinal (LCR) wave is proposed. The nonlinear ultrasonic (NLU) parameter is sensitive to the accumulated fatigue damage, showing two peaks around the 5th and 1000th cycles (0.03% and 6% of fatigue life), respectively. This phenomenon is comprehensively discussed in terms of dislocation structure evolution based on the dislocation string model. A correction considering the weakening of nonlinearity induced by the rough surface is applied to the experiment measurements. The corresponding results are closer to the finite element modeling (FEM) quantitation based on the dislocation-dependent nonlinear constitutive relation. Compared to linear LCR wave, nonlinear LCR wave has weaker sensitivity to roughness effect and higher sensitivity to damage such as dislocation, which offers a new method for monitoring fatigue in engineering components.

Non-destructive evaluation of the effects of exposure environment in mortars using non-linear ultrasonic measurements

The development of non-destructive techniques has currently a high interest, such as those based on non-linear ultrasonic measurements. In this work it has been assessed the possible application of non-linear ultrasonic measurements for getting information related to the microstructure and properties of Portland cement mortars exposed to real and non-optimum environments. The pore structure was studied using mercury intrusion porosimetry and differential thermal analyses. Mechanical strengths and linear ultrasonic pulse velocity were determined. Regarding non-linear ultrasonic measurements, the results of parameters R and DIFA were analyzed. The tests were performed at 28 and 250 days. At later ages, a loss of microstructure refinement and a worsening of mechanical performance of the mortars were observed. The results of non-linear ultrasonic parameters R and DIFA overall agreed with those obtained for the microstructural and mechanical characterization performed. In particular, an adequate correlation between parameter DIFA and the pore size distributions was observed.

Feasibility of Application for the SHG Technology of Longitudinal Wave in Quantitatively Evaluating Carbonated Concrete

The ultrasonic transmission detection method is used to investigate the applicability for the second-harmonic generation (SHG) technology of longitudinal wave to quantitatively assess carbonated concrete. The principal of this method is to use the piezoelectric lead zirconate titanate (PZT) patch to detect the second-harmonic of longitudinal waves during the concrete carbonation process and extract non-linear parameters from observed signals. Non-linear parameters of concretes with two water–cement ratios (CI (w/c=0.47), CII (w/c=0.53)), two moisture contents (CI 0%, CI-W 100%), and three ultrasonic incident frequencies (50 kHz, 75 kHz, 100 kHz) were measured in this study. Results of the experiment demonstrate that non-linear ultrasonic parameters of longitudinal ultrasonic waves with high frequencies (75 kHz, 100 kHz) exhibit a better resolution regarding changes in concrete microstructure. Moisture (CI 0%, CI-W 100%) has little effect on the rate (CI: 62.73%, CI-W: 60.25, carbonation depth: 15 mm) for the change in relative non-linear parameters in the same concrete. The carbonation depth of concrete (CI (w/c=0.47), CI-W (w/c=0.47), CII (w/c=0.53)) can be well reflected by the change in relative non-linear parameters. Furthermore, there exists a good fit between the relative non-linear parameters of longitudinal waves and the concrete carbonation process. The relative non-linear parameters of longitudinal waves demonstrate feasibility in the quantitative assessment of concrete carbonation.

Effect of Temperature on Ultrasonic Nonlinear Parameters of Carbonated Concrete

In order to explore the monitoring technique of concrete carbonation in various temperatures, longitudinal ultrasonic nonlinear parameters of carbonated concrete are measured by using an embedded composite piezoelectric transducer (ECPT) and a surface-mounted transducer. The effect of temperature from -20 ∘C to 40 ∘C with a temperature interval of 5 ∘C and water-cement ratio on the measurements of ultrasonic parameters for carbonated concrete is investigated. The ultrasonic transmission detection method and the second harmonic generation (SHG) technique for longitudinal waves are used in the study. Results of the experiment demonstrate that ECPT is effective in the monitoring of the changes in ultrasonic parameters of carbonated concrete. At the temperature ranging from 15 ∘C to 40 ∘C, the increasing temperature slightly increases the relative nonlinear parameters of carbonated concrete. It decreases significantly that the relative nonlinear parameters of carbonated concrete measured at 0 ∘C compared with that at 10 ∘C. The configuration in this measurement is also appropriate for the assessment of carbonated concrete during carbonation time in low-temperature environments (below 0 ∘C). In the same carbonation time, the relative nonlinear parameters also increase slightly when the temperature is at -20 ∘C to 0 ∘C, but it does not change too much. Furthermore, there is a more significant variation of the nonlinear parameters in the same carbonation time for the specimens with a high water-cement ratio than that with a low one.

Comparisons of second- and third-order ultrasonic nonlinearity parameters measured using through-transmission and pulse-echo methods

It is well known that ultrasonic nonlinearity parameters are effective for assessing material degradation, so many applied studies have been actively conducted. However, a method of measuring the second-order nonlinearity parameter by the through-transmission method (TT) has been used in most cases. In these cases, the second-order harmonic component generated during the transmission of ultrasonic waves in the material is measured. In this study, we demonstrate the utility of the method for measuring the third-order nonlinearity parameter by the pulse-echo method (PE), which is advantageous for field applications because it measures only one side. In addition, the second harmonic component is difficult to measure by PE due to the phase inversion effect, but the third harmonic is not affected by phase inversion. To experimentally verify such differences in different measurement methods, second- and third-order nonlinearity parameters were measured using both TT and PE for the same specimen. For this, two Al6061-T6 alloy specimen groups, high-temperature heat-treated and tensile fatigued, were prepared, of which trends in the second-order nonlinearity parameters measured by TT were well-known. In both specimen groups, second- and third-order nonlinearity parameters measured by TT exhibited the same trend according to heat treatment time or fatigue. On the other hand, in the results measured by PE, only the third-order nonlinearity parameter showed the same tendency as the results of TT, whereas almost no change in the second-order nonlinearity parameter was observed. This result confirms that the third-order nonlinearity parameter measurement by PE can be used equally with the second-order nonlinearity parameter measurement by TT and is expected to remarkably expand the field applicability of nonlinear ultrasonic techniques.

A Nonlinear Ultrasonic Method for Detection and Characterization of Dewetting Damage in Solid Propellant

AbstractThe dewetting damage of solid propellant under loading is a key factor affecting the constitutive properties of solid propellant, and it will weaken structural integrity of solid rocket motor charge. The quantitative characterization of its evolution process has always been a very active research field. In this study, a nonlinear ultrasonic (NLU) method is proposed to investigate and monitor in real‐time the nonlinear dynamic response of solid propellant. The NLU parameter, which can evolve dewetting damage, is expressed by some physical quantities such as the frequency peak, the propagation distance and so on, and is recorded at different strain in the tensile tests of the round rod solid propellant specimens. Then, the initial dewetting point, characteristic dewetting point and characteristic dewetting rate are defined to characterize the dewetting performance. The results show that NLU parameter changes continuously with the evolution of tensile process and increases sharply at the initial dewetting damage point. By analyzing the data, an empirical formula characterizing the variation law of NLU parameter with strain is proposed, which is well fitted to the experimental data under different strain rates. In addition, relevant numerical simulation is carried out, and the simulation results verify the feasibility of the NLU method.

Microstructural Characterization of Additively Manufactured Metal Components Using Linear and Nonlinear Ultrasonic Techniques.

Metal additive manufacturing (AM) is an innovative manufacturing technology that uses a high-power laser for the layer-by-layer production of metal components. Despite many achievements in the field of AM, few studies have focused on the nondestructive characterization of microstructures, such as grain size and porosity. In this study, various microstructures of additively manufactured metal components were characterized non-destructively using linear/nonlinear ultrasonic techniques. The contributions of this study are as follows: (1) presenting correlation analyses of various microstructures (grain size and texture, lack of fusion, and porosity) and ultrasonic properties (ultrasonic velocity, attenuation, and nonlinearity parameters), (2) development of nondestructive microstructural characterization techniques for additively manufactured components; and (3) exploring the potential for the online monitoring of AM processes owing to the nondestructive nature of the proposed technique. The performance of the proposed technique was validated using additively manufactured samples under varying laser beam speed conditions. The characteristics of the target microstructures characterized using the proposed technique were consistent with the results obtained using destructive optical microscopy and electron back-scattered diffraction methods.

Characterization of optimal healing efficiency based on a new nonlinear ultrasonic method for the process of gradient heating healing in asphalt mixture

In this research, we proposed a new nonlinear ultrasonic method, second harmonic generation (SHG) technique, to investigate the gradient heating-healing properties and determine the optimal healing efficiency in asphalt mixture based on the principle of ultrasonic Rayleigh surface wave. The energy approach is used to characterize the released energy based on the laws of Newton's convection. The released energy can be used to determine the optimum healing period according to law of conservation of energy. Three healing indices, absorbed energy, effective healing depth and nonlinear ultrasonic parameter, are respectively defined to characterize the healing efficiency of asphalt mixture for different healing periods. The healing gradient direction is verified by the X-ray computed tomography (CT) scanning images and corresponding porosity calculation. The results indicate the existence of an optimal healing period and healing efficiency in the healing process of asphalt mixture, and the calculation method proposed here is suitable to predict the optimal healing efficiency. While the nonlinear parameter is considerably prominent due to its sensitivity and high resolution for each healing period. Finally, through the correlation analysis of three healing indices, it is found that the nonlinear ultrasonic parameter is an ideal alternative of two other healing indices in terms of characterizing the gradient heating-healing properties of asphalt mixture specimens.

Investigation on characteristics of tensile damage and microstructure evolution of steel AISI 316L by nonlinear ultrasonic Lamb wave

In view of the high sensitivity to microstructure evolution of higher harmonics generated by the nonlinear ultrasonic method, the tensile damage in the stainless steel AISI 316L was evaluated by nonlinear ultrasonic Lamb wave. The effect of different degree of tensile deformation on nonlinear ultrasonic response in 316L was analyzed by considering the microstructure evolution and the test results. First, the power-law relation of nonlinear ultrasonic parameter and plastic strain is proposed. Meanwhile, martensitic transformation and the increasing of dislocation density can be observed in the micrographs of specimens with the increase of plastic deformation. Then, the same variation tendency of intergranularly averaged Kernel Average Misorientation (KAM), as well as the relative nonlinear ultrasonic parameter, demonstrated that the nonlinearity due to tensile damage is controlled by the evolution of microstructure that directly affects higher order elastic constant of stainless steel 316L. Furthermore, based on continuous damage mechanics, the method quantitatively characterizes the degradation of mechanical properties was proposed with a functional relation of damage variable and relative nonlinear parameter. The method proposed in this study provides a theoretical basis for online monitoring of the damage status of in-service equipment. It is of great significance for residual life assessment, structure integrity assessment, and service life extension of equipment.

Ultrasonic nonlinear evaluation of tensile plastic damage in Nickel based single crystal superalloy

The tensile interruption tests of Nickel-based single crystal (NBSX) superalloys at room temperature were carried out to artificially introduce controllable levels of plastic damage, and linear and nonlinear ultrasonic nondestructive methods were used to evaluate it. The results indicate that ultrasonic nonlinear parameter β shows hypersensitivity to early tensile plastic damage compared with traditional linear parameters. Transmission electron microscope (TEM) and X-ray diffraction (XRD) measurements of dislocation string length and dislocation density were conducted to calculate the theoretical predicted values of β by ultrasonic nonlinearity dislocation monopole model, and they are in well agreement with experimental results. In addition, the actuation of slip systems and evolution of dislocation configuration were observed under optical microscope (OM) and TEM. From the perspective of element distribution and energy, it is revealed that the plastic deformation mechanism of the NBSX superalloys at room temperature is anti-phase boundary (APB) dislocation pairs shear γ′ phase. The measurement results of macro mechanical properties manifested that accumulative tensile plastic deformation lead to increase of strength and decrease of plasticity.

Nonlinear Acoustic Technique for Monitoring Porosity in Additively Manufactured Parts

Abstract Ultrasonic wave based techniques are widely used for damage detection and for quantitative and qualitative characterization of materials. In this study, ultrasonic waves are used for probing the response of additively manufactured 316L stainless steel samples as their porosity changes. The additively manufactured stainless steel specimens were fabricated using a laser powder bed fusion (LPBF) metal 3D printer. Four different levels of porosity were obtained by suitably controlling the LPBF process parameters. For generating ultrasonic waves, lead zirconate titanate (PZT) transducers were used. The signals were generated and propagated through the specimens in a transmission mode setup. Both linear and nonlinear analyses were used during the signal processing of the recorded signals for damage characterization. Linear ultrasonic parameters such as the time-of-flight (related to wave velocity) and signal amplitude (related to wave attenuation) were recorded. The nonlinear ultrasonic parameter, Sideband Peak Count—Index (SPC-I), was obtained by a newly developed nonlinear analysis technique. The experimental results obtained for the specimens were analyzed and compared for both linear and nonlinear ultrasonic analyses. Finally, the effectiveness of the SPC-I technique in monitoring porosity levels in additively manufactured specimens is discussed.

Weibull parameter based probability distribution for predicting creep life of power plant materials: A non-destructive approach

The knowledge of remaining useful life and the probability of failure at any point of time in the life cycle of any power plant component is an important information for the plant operators to take preventive action. This paper focuses on life data evaluation of creep-exposed power plant material based on statistical probability distribution through Weibull analysis. The probability distribution was obtained considering the change in non-linear ultrasonic (NLU) parameter measured in P92 steel at different creep test conditions. The material was creep tested at 650⁰C for three different applied stresses. The NLU parameter (β), which indicates the extent of damage, is the ratio of the amplitude of the fundamental frequency of the transmitted signal to the square of the amplitude of the second harmonic of a sinusoidal wave propagated into the material. The two-parameter based Weibull distribution function was adopted for evaluating the cumulative distribution function and failure rate. A sudden increase in NLU parameter was observed at ∼ 80% of creep damage followed by a drop in its value indicating the specimen failure. With increase in applied stress, failure rate increase was also observed. Microstructural observations revealed that with creep progress, the growth and coarsening of precipitates, micro crack formation and their coalescence were the major cause for increase in failure rate. Therefore, application of this technique can be useful for evaluating the creep life and probability of failure of any plant component in a non-invasive way.

Ultrasonic nonlinear parameter based on Hollomon hardening model

The Hollomon hardening model is introduced into the wave equation of ultrasound and the ultrasonic nonlinear parameter βn based on hardening index n is obtained. Subsequently, tensile tests and ultrasonic nonlinear tests are carried out on AA6061-T6 aluminum alloy specimens under different pre-deformations and strain rates. The results show that under unloading condition, the normalized βn based on n and the normalized βtest based on ultrasonic nonlinear test both increase with the increasing pre-deformation and strain rate. The growth rate of the former is about 77% of the latter. The results show that it is possible to evaluate the hardening state of materials quantitatively based on ultrasonic nonlinear technology.

Nonlinear ultrasonic testing for evaluation of fracture toughness in 4130 steel

An estimation of plane strain fracture toughness [endif]--> is essential to assess the operational safety of fracture-critical systems; loss of [endif]-->can lead to catastrophic failure. However, it is not possible to quantify [endif]-->in situ; the laboratory testing to determine [endif]-->is destructive. Here, we investigate nonlinear ultrasonic testing as a nondestructive method to evaluate [endif]-->. This is based on a hypothesized correlation between the nonlinear ultrasonic parameters and [endif]-->characteristics of a material given their mutual dependence on microstructure. Using Second Harmonic Generation (SHG), surface and bulk waves are used to measure the (relative) nonlinearity parameter for tempered 4130 steel samples. Coupons made of the same materials are also tested for their [endif]-->characteristics using Charpy V-Notch testing, providing a direct comparison between destructive and nondestructive measures. Our results show correlations between ultrasonic parameters and [endif]-->characteristics of 4130 steel samples, but different relations are observed for bulk and surface waves. The observed differences are possibly due to sample heterogeneity and different wave structures of the two wave modes and should be further investigated. We demonstrate the potential of nonlinear ultrasonic testing for [endif]-->estimation. The ultimate goal is developing a nondestructive method to assess [endif]--> in situ.

Thermal damage evaluation of nickel-based superalloys based on ultrasonic nondestructive testing

Ultrasonic nondestructive technique was used to assess the thermal degradation in a nickel-based superalloy in this research. Thermal exposure tests were carried out at an elevated temperature of 1050 °C to introduce controlled levels of damage, while the linear ultrasonic parameters (sound velocity and attenuation coefficient) and nonlinear ultrasonic parameters were observed. The evolution of the microstructure and the subsequent degradation in macro-mechanical properties of the material were quantitatively researched. The results suggest that the nonlinear parameters show hypersensitivity and high-credibility compared with the traditional linear parameters. The monotonic increase of the ultrasonic nonlinear parameters was explained by the evolution of the lattice mismatch and the volume fraction of the γ′ and carbide precipitated phase based on the dislocation precipitation interaction model.

Nonlinear Analysis Method of High-Strength Steel Based on Local Buckling Fiber Hinge

Based on the analysis and summary of the research and application status of domestic and foreign high-strength steel local buckling fiber hinged rod stability and ordinary steel local buckling fiber hinged rod stability control, this paper proposes a fiber hinged rod suitable for spatial structures subject to local buckling. The new type is high-strength steel composite local buckling fiber hinged pressure rod. The influence of related parameters in the dislocation string model and the dislocation couple model on the ultrasonic nonlinear parameters is deeply analyzed. And, from the perspective of contact nonlinear acoustics, the mechanism of the ultrasonic nonlinear response of the crack is analyzed, and the finite element software ABAQUS is used to simulate it. The relationship between the nonlinear parameter and the internal crack shape of the material is simulated and analyzed, which proves the nonlinearity. A series of nonlinear ultrasonic testing was performed on three groups of FV520B high-strength steel fatigue specimens using a nonlinear testing system. Analyzing the results, it is found that the material has a good ultrasonic nonlinear cumulative effect, and the microcracks have a greater impact on the ultrasonic nonlinear response. The β-N curves under three sets of fatigue tests are obtained. The results show that the nonlinear parameters are very sensitive to the fatigue damage of FV520B high-strength steel, and the ultrasonic nonlinear parameters generally increase with the increase in the number of fatigue cycles.