•A method is proposed combining nonlinear SPC based techniques and pulse-echo method.•The proposed method has a high sensitivity to detect fatigue damage.•The method maintains the easier operability ...as traditional linear methods.•The length and width of cracks are more sensitive to low and high frequencies, respectively.
The nondestructive ultrasonic detection and evaluation of fatigue cracks is critical to ensure the safe operation of equipment. Although linear ultrasonic methods are easy to implement in practice, their parameters are insensitive to micro-scale cracks that are smaller than the wavelength. Conventional nonlinear techniques have better sensitivity but require a relatively complicated configuration and demanding experimental setups. In this work, a simple approach for the inspection of fatigue damage is presented to overcome the above shortcomings by combining nonlinear sideband peak count (SPC) techniques with the pulse-echo experimental method. Related nonlinear wave theories are briefly reviewed, and experiments are performed in stainless steel specimens with varying crack levels to verify the effectiveness of the proposed method. The linear and nonlinear parameters are extracted from the measurements for comparison. The results demonstrate that, under the same pulse-echo mode with low excitation amplitude, both the SPC-I (sideband peak count-index) and SPI (sideband peak intensity) variations are more sensitive to the quantitative detection of fatigue cracks than the conventional linear and nonlinear ultrasonic based parameters, especially in the initial stages of cracking. Experiments using pitch-catch configuration and an additional pulse-echo experiment using a different input frequency are carried out to verify the reliability and superiority of the proposed method. This work provides a convenient and efficient method for robust measurements of early damage of materials in practice.
This paper deals with the description and use of one of the up-to-date NDT method, the ultrasonic pulse echo, to determine the thickness of an asphalt concrete model. In the article, the authors ...explain the principle of the method and the limits of its use. Furthermore, attention is also paid to the influence of the shape and design of the back wall of the tested elements and the speed of propagation of ultrasonic waves. The research is part of a larger work, defect analysis and implementation of Whitetopping technology in the Czech Republic.
•Ultrasonic NDT uses pulse-echo or direct transmission-reception to investigate structures.•A method using both approaches simultaneously was developed.•The joint outcome improves the accuracy ...significantly regarding reflection coefficient assessment.•The novel approach was proved experimentaly and with numerical simulation.
Most ultrasonic applications in non-destructive testing (US-NDT) by contact use pulse-echo or direct transmission reception. Because of the nature of each method, part of the data is not retrievable. Thus, jeopardizing the analysis and synthesis of information. However, by applying these methods together, the joint approach can provide additional evidence from NDT. This study proposes a novel procedure that combines the most common US-NDT that includes rationale and theory. The goal is to improve the reflection coefficient assessment that is defined as the combined reflection coefficient (CRC). The determination of this parameter can improve the estimates of the attenuation of the medium when only one sample is available or when immersion techniques cannot be applied. The proposed arrangement uses one transducer as a transmitter and two transducers located on opposite sides of the working piece as the receivers. The measurements were performed simultaneously with the two receiving transducers. The general equations relate the signal amplitudes and identify the energy losses in each reflection within the material and its interface. The graphs show the amplitude loss. Furthermore, numerical simulations using the k-Wave software indicate an exponential relationship between the CRC and amplitude losses and the traditional ultrasonic methods and their combination. The theory was verified by numerical simulations using the k-Wave software and experiments with two aluminium samples at two ultrasonic frequencies of 2.25 MHz and 5.0 MHz. The usefulness of the new method for the determination of the CRC, including improvements in the estimates of acoustic attenuation in low-loss pieces, was proven.
Empirical data is presented on the pulse-echo performance of poly-vinylidenefluoride (PVDF) ultrasound transducers monitored in-situ at temperatures in the range 50–130°C. Measurements were performed ...over a 5 h period beginning at the sensors’ initial exposure to temperature. A reduction in pulse-echo amplitude was observed at all temperatures in the range and was found to be proportional to temperature increase. Four different thicknesses of PVDF film were used for the trials and small differences in behaviour were observed between sensors constructed using each thickness. On average, the overall loss was found to increase linearly with temperature from a 16% drop in pk–pk pulse-echo voltage observed at 60°C to a 95% drop in performance at 120°C after 5 h. Rates of signal loss were found to follow a logarithmic decay, particularly at temperatures above 70°C where significant reductions were observed in the initial seconds/minutes following exposure to temperature.
Ultrasonic pulse-echo C-scan imaging is a widespread method for detecting and characterizing defects in fiber reinforced polymer composites. However, the accurate assessment of a complex distributed ...damage cluster, like barely visible impact damage, in multi-layer and heterogeneous composites is not straightforward. For reliably estimating the remaining load carrying capacity and/or remaining useful lifetime of a damaged composite, a proper and complete damage assessment is of utmost importance.
In this paper, a statistical time-energy gating approach is proposed in view of obtaining improved ultrasonic pulse-echo imaging of impacted composites. The majority of virgin A-scan signals are first clustered by analyzing their back-wall echoes. Next, using the principle of maximum likelihood, a Rice distribution is matched to the instantaneous amplitude in order to estimate the natural variability in the local energy of the virgin response signals. The resulting time-varying reliability interval provides an effective means to identify signals coming from defects or inhomogeneities, and as such to robustly assess defect parameters. The proposed probabilistic imaging procedure is demonstrated on various carbon fiber reinforced polymer laminates with barely visible impact damage. The obtained results are benchmarked by conventional ultrasonic C-scan imaging in through-transmission mode as well as in pulse-echo mode using the classical time gating approach. In contrast to the classical time gate method, the proposed statistical time-energy gating procedure successfully extracts and quantifies the full extent of the complex impact damage cluster. Further, the good noise resistance of the proposed probabilistic imaging method is demonstrated for a wide range of signal-to-noise ratios.
In this work, we report on the structure and dynamics of the 1,1,3,3 tetramethyl guanidine (TMG) aqueous solutions in a wide concentration and temperature range by combining vibrational and ...ultrasonic spectroscopies. The experimental Raman spectra have been compared with the corresponding spectra obtained by ab initio quantum mechanical and density functional theory electronic structure calculations. This comparison indicated that only a single mechanism occurs when dissolving TMG in water and this is the proton transfer reaction, while the formation of byproducts during hydrolysis of TMG is dubious. This observation is further supported by the concentration dependence of the Raman spectra. The analysis of the ultrasonic relaxation data also revealed that the system exhibits a single relaxation process associated with this proton transfer reaction. It has been also observed that both relaxation amplitude and frequency exhibit a clear monotonous increase with increasing amine concentration in the solutions supporting the concept of the proton transfer reaction. The corresponding activation enthalpy was estimated directly from the temperature dependence of the acoustic data and found equal to ΔH* = 5.56 ± 0.34 kcal/mol, which seems to be reasonable for hydrogen-bond formation. Furthermore, the concentration dependence of the acoustic parameters and kinematic viscosity data has been used as a probe for the molecular association in these solutions. The results have been discussed in relation to the ability or inability of water molecules to form stable clathrates after the addition of amine molecules in the solutions.
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•A single relaxation process related to proton transfer occurs in TMG aqueous solutions.•Relaxation parameters support the assignment of ultrasonic relaxation to proton transfer.•The activation enthalpy ΔH* = 5.56 ± 0.34 kcal/mol is reasonable for hydrogen-bond formation.•Formation of byproducts during TMD hydrolysis is excluded using Raman spectroscopy.•The stability of substructures in solutions is reflected on acoustic properties.
Lithium Nickel Manganese Cobalt Oxide (NMC) is one of the most common oxide cathode materials for Li-ion batteries. NMC is also under consideration for use in all solid-state batteries. However, ...differences in the coefficients of thermal expansion (CTE) between NMC and the solid electrolyte during composite electrode fabrication and differential expansion and contraction during electrochemical cycling will cause stresses possibly resulting in electrode fracture and battery capacity fade. As a consequence, we hot-pressed phase-pure polycrystalline NMC with controlled density and accurately measured the mechanical (elastic modulus, shear modulus, Poisson’s ratio and nanoindentation hardness) and physical properties (CTE and thermal conductivity). We believe that this is the first report of the mechanical and physical properties of commercially available NMC and these experimental data are important to predict or increase the cycle life of NMC as a cathode material for state-of-the-art Li-ion and advanced solid-state batteries.
•The pulse-echo nonlinear acoustic waves of a focused transducer are analyzed.•Wave distortion behaviors in the reflected direction are studied and explained.•Experiments are conducted to verify the ...theoretical analysis.
The pulse-echo nonlinear acoustic wave fields generated by focused transducers are calculated numerically and verified experimentally. Simulation results show that in the reflection direction, phase differences between newly generated second harmonic and reflected waves are about π/2, regardless of the rigid and stress-free boundaries; thus, the total second harmonic wave will neither be strongly enhanced nor be cancelled. Experiments are conducted with a focused transducer working in pulse-echo mode and the measured amplitudes of nonlinear waves reflected after water-air and water-aluminum/steel interfaces agree with the simulated results. This work helps advance applications using pulse-echo nonlinear acoustics.
•Three NDT methods with different principles to the detection of delamination.•Methods are demonstrated and validated experimentally and in-situ.•Potentials and limitations of each method are ...compared.
Buildings, bridges, roads, and other structures need to be regularly maintained if they are to last. In general, if a defect is detected early, the cost of its remediation is typically much lower than if the structure is allowed to degrade for months or years. A key means of locating hidden defects are non-destructive testing methods. This paper describes measurements that compare three non-destructive methods applied to a concrete bridge and a laboratory specimen with artificial defects to simulate cavities. Three methods (infrared thermography, ground-penetrating radar and ultrasonic pulse echo) were used to measure the depth and size of cavities in the concrete panel. Furthermore, the measurements were made using two different brands of radar and two different thermal imaging cameras from the same manufacturer. Lastly, the NDT methods were compared across general performance criteria in terms of accuracy, testing practicality, and costs.
