Measurement Of Stress Waves Research Articles

Exploring the Potential of Promising Sensor Technologies for Concrete Structural Health Monitoring.

Structural health monitoring (SHM) is crucial for maintaining concrete infrastructure. The data collected by these sensors are processed and analyzed using various analysis tools under different loadings and exposure to external conditions. Sensor-based investigation on concrete has been carried out for technologies used for designing structural health monitoring sensors. A Sensor-Infused Structural Analysis such as interfacial bond-slip model, corroded steel bar, fiber-optic sensors, carbon black and polypropylene fiber, concrete cracks, concrete carbonation, strain transfer model, and vibrational-based monitor. The compressive strength (CS) and split tensile strength (STS) values of the analyzed material fall within a range from 26 to 36 MPa and from 2 to 3 MPa, respectively. The material being studied has a range of flexural strength (FS) and density values that fall between 4.5 and 7 MPa and between 2250 and 2550 kg/m3. The average squared difference between the predicted and actual compressive strength values was found to be 4.405. With cement ratios of 0.3, 0.4, and 0.5, the shear strength value ranged from 4.4 to 5.6 MPa. The maximum shear strength was observed for a water-cement ratio of 0.4, with 5.5 MPa, followed by a water-cement ratio of 0.3, with 5 MPa. Optimizing the water-cement ratio achieves robust concrete (at 0.50), while a lower ratio may hinder strength (at 0.30). PZT sensors and stress-wave measurements aid in the precise structural monitoring, enhanced by steel fibers and carbon black, for improved sensitivity and mechanical properties. These findings incorporate a wide range of applications, including crack detection; strain and deformation analysis; and monitoring of temperature, moisture, and corrosion. This review pioneers sensor technology for concrete monitoring (Goal 9), urban safety (Goal 11), climate resilience (Goal 13), coastal preservation (Goal 14), and habitat protection (Goal 15) of the United Nations' Sustainable Development Goals.

Diagnosis and assessment of a historic timber structure in La Casa del Corregidor, using non-destructive techniques

This paper presents the assessment of the timber structure of “La Casa del Corregidor” building, a singular historic building in Cuenca (World Heritage City). The building is scheduled for restoration in the near future. The study made use of both non-destructive (NDT) and semi-destructive (SDT) techniques.A thorough experimental campaign and inspection were conducted on all the old wood elements across the eight floors of the building. More than 1200 elements of Pinus sylvestris L. wood were inspected. The data collected in this campaign allowed a mechanical evaluation of the timber elements.The following NDT and SDT were used: visual inspection, microphotography, moisture meter, stress-wave measurements, and resistance drilling. These techniques made facilitated the identification of the wood species, detection of natural defects and decayed areas, and estimation of the physical and mechanical properties of the timber elements. The experimental results were statistically analysed using a multidisciplinary approach to determine the scope of the intervention on the structure to meet the new use and its structural requirements. The final report produced at the end of the inspection was made of colour plans describing the singularities, natural defects, timber decays and damages of each single member.The results obtained will orient the building's conservation work. These findings support a minimal intervention, since more than 95 % of the structural elements were found to be in good condition.

Prediction of Static Bending Properties of Eucalyptus Clones Using Stress Wave Measurements on Standing Trees, Logs and Small Clear Specimens

In this study, we used both nondestructive and destructive methods for assessing solid wood properties in six Vietnamese grown Eucalyptus clones at 6 years after planting. We measured stress wave velocity in standing sample trees (SWVT), logs (SWVL), and small clear specimens (SWVS) obtained from the trees and logs, and to measure static properties, we used MOE—modulus of elasticity and MOR—modulus of rupture. The highest average MOE and MOR were detected in clones 3 and 5, suggesting that these clones might be more appropriate for breeding programs focused on improving wood quality of Eucalyptus grown in Vietnam. Mean MOE and MOR of the lumber had significant (p < 0.001) relationships with SWVT (r = 0.61 and 0.53, respectively) and SWVL (r = 0.76 and 0.71, respectively). Stress wave velocity measurements of both standing trees and logs can be useful for further segregating Vietnam’s Eucalyptus timber resource based on MOE and MOR. For the small clear specimens, the best prediction of stiffness (dynamic modulus of elasticity (MOEd)) was obtained when both SWVS and air-dry density (AD) were used. The coefficient of correlation between MOE and MOEd was 0.93.

Multi-Physics Mesoscale Substructure Analysis on Stress Wave Measurement within CFST-PZT Coupling Models for Interface Debonding Detection.

In recent years, the development of interface debonding defect detection methods for concrete-filled steel tubes (CFSTs) using stress wave measurement with piezoelectric-lead-zirconate-titanate (PZT) actuator and sensor has received significant attention. Because the concrete core in CFSTs is a heterogeneous material with randomness at the mesoscale, the size, position and distribution of aggregates unavoidably affect the stress wave propagation and the PZT sensor response. In this study, to efficiently investigate the influence of the mesoscale structure of the concrete core of CFSTs on the response of embedded PZT sensors, a multi-physics substructure model of CFST members coupled with a PZT actuator and a PZT sensor, where a single circular aggregate with different size and position and randomly distributed circular aggregates are considered, are established first. Then, multi-physics simulations on the effect of the local mesoscale structure of the concrete core on the response of the embedded PZT sensor excited by both a sinusoidal signal and sweep frequency signal are carried out. Moreover, corresponding multi-physics and mesoscale simulations on the embedded PZT sensor response of substructures with different interface debonding defects are also carried out for comparison. The amplitude and the wavelet packet energy of the embedded PZT sensor response of each mesoscale substructure are employed to distinguish the influence of the concrete core mesoscale structure and interface debonding defect on sensor measurement. The findings from the results with the multi-physics coupling substructure models are compared with those of the full CFST-PZT coupling models and the tested members of the previous studies to verify the rationality of the embedded PZT sensors measurement of the established substructure models. Results from this study show that the effect of interface debonding defect on the amplitude and the wavelet packet energy of the embedded PZT sensor measurement of the CFST members is dominant compared with the mesoscale heterogeneity and randomness of the concrete core.

Aerostat Airbag Damage Detection Based on VMD Decomposition and GenSVM

The capsule of the buoy is usually woven with composite materials. The existence of material anisotropy makes it difficult to establish the degradation mechanism model of the capsule, which affects the defect detection and health management of the capsule. To this end, this paper proposes a data-driven airbag defect detection method based on stress wave measurement. Firstly, strain signals under acoustic excitation are collected by sticking strain gauges on the surface of the capsule. Then, VMD is used to decompose the signal and extract the energy characteristics of each modal signal component to construct the feature vector. Finally, the feature vector is input into the GenSVM model for defect type recognition. The example analysis shows the effectiveness and applicability of the proposed method.

Interpretation of static and dynamic Young’s moduli and Poisson’s ratio of granular assemblies under shearing

Young’s modulus (E) and Poisson’s ratio (v) of granular assemblies are two essential mechanical properties. Measurements based on stress–strain relationships gives static values (Esta and vsta) while stress wave measurements give dynamic values (Edyn and vdyn). This study adopts the discrete element method (DEM) to investigate the evolution of E and v regarding various loading probes under drained conditions at selected strain levels from the original loading. The DEM results reveal that Esta and Edyn or vsta and vdyn are not always equivalent for face-centred cubic (FCC) packings and random/disordered packings (RDP). When samples are beyond the initial elastic range, either increasing friction coefficient or conducting unloading leads to a recovery of elasticity where Esta and Edyn are equivalent during the entire axial range while vsta and vdyn are equivalent at initial elastic range. The stress-induced fabric anisotropy is found to have negligible effect on the comparisons between Esta and Edyn or vsta and vdyn under various loading probes. Microscopic investigations signify that mean contact force ratio and fraction of slip contacts are key parameters to evaluate elasticity. Besides, the supplementary laboratory tests are conducted using spherical glass beads in which Esta measured from the small-amplitude cyclic loadings after creep is equivalent to Edyn at the pre-peak strain range.

Analysis of the Stress-Wave Influence Parameters of Silicon MOSFET Under 300V Drain Source Voltage

The traditional condition monitoring (CM) methods for power electronic devices are normally using electrical, magnetic, and thermal sensors. Alternatively, this paper uses the acoustic emission (AE) sensor to measure the mechanical stress wave generated inside the power electronic devices such as MOSFETs. Specifically, this paper focuses on the influence of measured surface, electrical parameters, and filters on the stress wave signal and the reliability of repeatability tests. Under the single pulse test with 300V drain-source voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {ds}}$ </tex-math></inline-formula> ), the same acoustic emission sensor is pasted on the MOSFET package and the cooling surface with a coupling agent. The factors affecting stress waves are studied by changing electrical parameters and filters. The proposed experiments draw the following conclusions. 1) The characteristic parameters of the stress wave measured on the package and cooling surface of MOSFET are different under the same electrical parameters. 2) The characteristic parameters of the stress wave are almost unchanged under the same test conditions, which shows that the stress wave measurement method is reliable. 3) The peak value of the stress wave, the frequency domain amplitude, and energy are affected by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {ds}}$ </tex-math></inline-formula> and turn-on time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t}_{\text {on}}$ </tex-math></inline-formula> ). Specifically, the gate voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {gs}}$ </tex-math></inline-formula> has no obvious trend to the amplitude. The impact on package is basically the same as the cooling surface.

Mesoscale numerical analysis and test on the effect of debonding defect of rectangular CFSTs on wave propagation with a homogenization method

In this paper, in order to distinguish the influence of both interface debonding defect and the mesoscale structure of concrete core on the stress wave field and the response of an embedded Piezoelectric-lead-zirconate-titanate (PZT) sensor in rectangular concrete filled steel tube (RCFST) members efficiently, a two dimensional (2D) mesoscale numerical concrete homogenization approach for concrete core considering the random distribution of circular, elliptical and irregular polygonal aggregates is proposed firstly. Then, mesoscale simulation on stress wave fields within the cross-section of RCFST members with and without interface debonding defects using both mesoscale models and their homogenization models are carried out, respectively. The effect of both mesoscale structure of concrete core and the interface debonding defects on the stress wave field of each member is discussed and the efficiency of the homogenization approach is illustrated. Therefore, the time-domain response of an PZT sensor embedded in the concrete core of RCFST members coupled with PZT patches under sweep frequency excitation signal is determined with multi-physics field simulation and compared when both mesoscale models and their homogenization models are used. Then, the sensitivity of the wavelet packet energy of the embedded PZT sensor response on the variation of both mesoscale structure of concrete core and the dimension of interface debonding defects is investigated in details. Finally, in order to illustrate the difference in the significance of the effect of interface debonding defect and the mesoscale structure of concrete core on stress wave propagation, comparative test with a set of RCFST members without and with interface debonding defects is carried out. Test results also show that the influence of interface debonding defects on embedded PZT sensor response and the stress wave fields is dominant. The detectability of interface debonding detection approach using stress wave measurement is illustrated efficiently with the proposed equivalent homogenization mesoscale modelling approach even the mesoscale structure of the concrete core is considered.

Embedded PZT sensors for monitoring formation and crack opening in concrete structures

An application for sensing the stress-induced localization of damage in the form of a discrete crack in a concrete substrate is developed using embedded PZT patches. Stress-wave measurements are obtained through the stages of damage localization leading to crack formation, propagation, and opening of the discrete, localized crack in the concrete. A self-compensating attenuation factor is proposed to quantify the changes in stress waves produced by the material discontinuity introduced by cracking in concrete. The attenuation factor measurements provide a sensitive indication of displacement discontinuity introduced by a crack in the stress wave path. Displacement discontinuity in concrete associated with a crack opening smaller than 10 μm in the loaded state is detected in the attenuation factor measurements even after the removal of stress. The embedded PZT sensors can continuously monitor concrete structures for indications of crack formation before visual indication.

Experimental study on grout defects detection for grouted splice sleeve connectors using stress wave measurement

Grouted splice sleeve (GSS) connectors have been widely employed to connect rebars in prefabricated concrete (PC) structures. However, grout defects may occur due to manual operation miss or poor control approaches for quality, which weaken the efficient embedment of rebars in GSS connectors and lead to a negative effect on mechanical properties of PC structures. The development of reliable and efficient grout defect detection methods for GSS connectors is challenging because its inaccessibility and inner structure complexity. In this paper, an active grout defects detection approach for GSS connectors using direct stress wave measurement is proposed, where piezoelectric-lead-zirconate-titanate (PZT) patches are mounted on the surface of the sleeve as actuators and sensors, and experimental study is carried out to validate its feasibility. Stress wave propagating along the GSS connectors excited by the surface-mounted PZT actuator is measured with PZT sensors. In order to investigate the effect of grout defects on stress wave measurement, four GSS specimens with different degrees of mimicked grout defects are designed and analysis on the PZT sensor measurement with a pitch and catch pattern is carried out. By comparing the PZT sensors measurement of different specimens without and with different grout defects under an identical impulse excitation signal, the grout defect is detected. The relationship between a normalized defect evaluation index (DEI) determined by the use of the PZT sensor measurement and the grout defect severity is analyzed. Experimental results indicate grout defect leads to increase in PZT sensors measurement compared with that of specimen without grout defect. The results show that the proposed approach based on stress wave measurement is efficient in detecting grout defect and the stress wave measurement is sensitive to the dimension of grout defect in GSS.

Local wave propagation analysis in concrete-filled steel tube with spectral element method using absorbing layers – Part I: Approach and validation

Concrete-Filled Steel Tube (CFST) members have been widely employed in high-rise buildings or long-span bridges as vertical or axial load-carrying components and the development of efficient interface debonding detection approach for CFST members has been a common concern. In recent years, wave propagation measurement based interface debonding defect approaches have shown their efficiency and efficient numerical simulation techniques on elastic wave propagation within CFST members are critical to understand the mechanism of the approaches. In this study, in order to efficiently investigate the effect of interface debonding on local elastic wave propagation within CFST members, a two-dimensional (2D) time domain spectral element method (SEM), where absorbing layers with increasing damping (ALID) is introduced to attenuate the wave reflection effect on boundaries, is developed at first. Then, the developed 2D time domain SEM with ALID is employed to simulate the wave propagation in a steel plate and an isotropic panel mimicking concrete core in CFST members. The effect of ALID on the attenuation of reflected Lamb waves in the steel plate and the bulk waves in the isotropic panel is validated. Finally, the local wave propagation in a substructure of the CFST model is numerically studied with the proposed 2D SEM with ALID. The dimensions and parameters of the ALID are determined and their effect on eliminating the reflected waves within the substructure excited by a single point load and a surface-mounted PZT patch actuator is demonstrated, respectively. The developed 2D time domain SEM with ALID provides efficient tool to simulate the local wave propagation in CFST specimens with interface debonding defects for understanding the mechanism of local stress wave measurement based interface debonding detection method to be discussed in the accompanying paper.

Stress and damage localization monitoring in fiber-reinforced concrete using surface-mounted PZT sensors

In concrete structures, damage is identified by the appearance of cracks on the surface. Monitoring the level of tensile stress in the material provides an indication of microcrack localization, which leads to the formation of a crack in the medium. In this study, the stress in the substrate leading to the localized cracking in a concrete substrate is evaluated using surface-mounted PZT patches. The PZT patches are used in a local electrical impedance (EI) measurement mode and for distributed stress wave measurements. The EI measurements from PZT patches sensitively detect the tensile stress in the substrate. The localization of damage resulting in the formation of a crack in the concrete medium is detected sensitively by stress wave measurements. A frequency-dependent attenuation factor, which is independent of the intervening material effects is presented for quantifying the changes in the stress waves. The localization of microcracks leading to the formation of a crack is detected by the attenuation factor measurements of stress waves significantly before visual detection of a surface crack. The combined use of the EI measurement with the distributed stress wave attenuation allows for detecting stress and microcracking in the concrete leading up to the formation of a localized crack. The attenuation factor gives an indication of the crack opening once the crack is formed.

Nondestructive Testing on Ancient Wooden Components Based on Shapley Value

In this study, we propose nondestructive testing methods and combined forecasting models-based stress wave and impedance measurements to obtain accurate internal defects information for wooden building components. Internal defects data for major wooden components of an ancient building in China and reverse laboratory test data on matching tree species indicated various degrees of damage on the pavilion wood structure surface and internal defects in certain pillars. The stress wave method enabled rapid acquisition of two-dimensional plots of test sections; however, the results revealed that the area of stress wave detection was greater than the actual defect area. Moreover, the impedance meter was able to determine the defect position and type in a single path, and the actual defect area was proportional to the absolute error of the drilling resistance. By distributing the errors from the two nondestructive testing methods on the basis of a Shapley value algorithm, we determined the weights of stress wave and impedance meter data in the forecasting models and established combined forecasting models that showed greater accuracy with a mean relative error of less than 6%. This method can improve the prediction accuracy of internal defects in ancient buildings and provide effective data support for practical engineering repair and reinforcement schemes.

Numerical study on interface debonding detection mechanisms with 2D spectral element method for concrete-filled steel tube using embedded PZT sensor

Interface debonding detection approaches based on stress wave measurement for concrete-filled steel tube (CFST) members have received a great deal of attention in civil and infrastructural engineering societies. The development of efficient computing approaches to investigate the mechanisms of the interface debonding detection approaches and the effect of interface debonding on wave propagation within CFST members is critical. In this study, the wave propagation within the cross section of CFST members with and without interface debonding under a single point excitation force is simulated with a two-dimensional (2D) spectral element method (SEM) at first and that of CFST models coupled with a surface-mounted piezoelectric lead zirconate titanate (PZT) actuator and an embedded PZT sensor in the concrete core under continuous and sweep sinusoidal signals is simulated with the 2D SEM and a piezoelectric spectral element. The debonding defect is modeled by removing concrete elements between the steel tube and the concrete core. Results show that interface debonding affects the wave propagation process, the output potentials of the embedded PZT sensors as well as the displacement responses at different locations of CFST specimens obviously. Rayleigh damping identified from experiments is introduced to the SEM models to reflect wave attenuation in the coupled models. The effect of interface debonding on the amplitude, the Fourier spectra and the wavelet packet energy of stress waves are analyzed. For comparison, another numerical model in which the PZT actuator is not located near the interface debonding defect is studied numerically and the effect of the debonding defect on the response of the embedded PZT sensor is illustrated. SEM provides an efficient way to simulate stress wave propagation and to understand the mechanisms of interfacial debonding defect detection for CFSTs with PZT technique.

Multi-Scale Stress Wave Simulation for Aggregates Segregation Detection of Concrete Core in Circular CFST Coupled with PZT Patches.

In this study, the numerical investigation of the detectability of concrete aggregate segregation in circular concrete-filled steel tubulars (CCFST) based on piezoelectric lead zirconate titanate (PZT) measurement is performed. The stress wave propagation in the concrete core of circular CCFST excited with a surface-mounted PZT actuator is studied with multi-scale and multi-physical field coupling analysis. The piezoelectric effect of PZT patches and its coupling effect with CFSTs are considered. Numerical concrete modeling technology is employed to construct the concrete core composed of randomly distributed aggregates with and without aggregate segregation at different levels, mortar, and an interfacial transition zone (ITZ). The effects of the random distribution of elliptical aggregates, aggregate segregation, and the existence of ITZ in the concrete core on the wave fields in the cross-section and the corresponding voltage response of the embedded PZT sensor are discussed. An evaluation index based on wavelet packet analysis on the output voltage response is defined, and its sensitivity to concrete aggregate segregation is systematically investigated. The multi-scale and multi-physics coupling simulation results indicate that concrete aggregate segregation in the concrete core of CFST members can be efficiently detected based on the stress wave measurement with a PZT sensor.

NUMERICAL SIMULATION ON STRESS WAVE PROPAGATION OF STEEL-CONCRETE COMPOSITE STRUCTURES WITH INTERFACE DEBONDING BY SPECTRAL ELEMENT METHOD

To investigate the elastic stress wave propagation in steel-concrete composite structures, a 2 dimensional spectral element model for steel-concrete composite sections was established and the elastic stress wave propagation in the hybrid section with and without interface debonding defects was simulated under single point excitation. The interface debonding was simulated by removing concrete elements between steel tube and concrete core. The wave field and displacement responses of different nodes between the models with and without defects were compared to explain the effect of interface debonding on elastic stress wave propagation. Finally, the displacement responses of different numerical models with different levels of interface debonding were compared to investigate the relationship between the displacement response and the interface debonding defects. Spectral element method (SEM) provides an efficient way for the stress wave simulation of steel-concrete composite structures, which is helpful for the study on the mechanism for interface debonding detection of steel-concrete composite structures based on stress wave measurement.

Field and laboratory stress-wave measurements of asphalt concrete

Non-contact surface wave measurements are performed on a new asphalt concrete (AC) pavement using 48 micro-electro-mechanical system (MEMS) sensors as receivers to estimate the real part of the dynamic moduli of the AC top layer. Laboratory measurements of core samples, extracted from the field measurement positions, are used to construct master curves for comparison with the field measurements. The real parts of the dynamic moduli from the two test methods are consistent at the field measurement temperatures, and the non-contact field measurements are highly repeatable. These results indicate a possible application for quality assurance of AC based on mechanical properties.

Damage detection of concrete piles subject to typical damage types based on stress wave measurement using embedded smart aggregates transducers

Concrete piles are the most common types of foundation structures. Pile damages, such as fractures, cracks, mud intrusion and secondary concrete pouring, are the leading causes of pile structural failure, which may directly result in casualties and economic loss. It is desirable to develop a monitoring system that can detect these pile damages. In this paper, embedded piezoceramic-based smart aggregates transducers along with the active sensing approach are developed to detect common types of pile damages, including crack, partial mud intrusion, secondary pouring, and full mud intrusion, based stress wave measurement. With the active sensing approach, one smart aggregate is used as an actuator to generate a stress wave that will propagate along the pile, and other smart aggregate(s) will measure the propagating wave. All damages, which introduce new interfaces and discontinuities, attenuate the stress wave propagation. The attenuations of the stress waves based on different pile damages were compared by the received sensor signal in time domain. A wavelet packet-based energy analysis was used to develop an energy index to assist the detection of damages. Experimental results demonstrated the feasibility that the proposed approach can detect all four types of common damages associated with concrete piles.

Measurement of stress waves induced by laser pulse

This letter describes modelling and experimental results of low and high pressure shock waves (of the order of 100 and 1000 bar, respectively) induced by pulse laser radiation. Measurements were performed using piezoelectric polymer PVDF sensors. The results of numerical calculations and their comparison with an experiment have been posted. Measured and calculated results have been used in estimation of the temporary course of signals from a fibre VISAR interferometer which measured the movement velocity of steel plate driven by the analysed shock waves. Description is supplemented with results of magnitude measurements of surface plastic deformation and material microstructure of samples. Full Text: PDF References J. Wang, N.R. Sottos, R.L. Weaver, Tensile and mixed-mode strength of a thin film-substrate interface under laser induced pulse loading, J. Mech. Phys. Solids 52, 999 (2004). CrossRef R. Ecault et al., study of composite material damage induced by laser shock waves, Composites A 53, 54 (2013). CrossRef K. Jach et al., Computer modeling of dynamic interactions of bodies using free point method, Wydawnictwo Naukowe PWN, Warszawa, (2000) (in Polish). D.H. Dolan, Foundations of VISAR analysis, SANDIA REPORT, SAND2006-1950 (2006). CrossRef

Dynamic properties of zirconium alloy E110 under shock-wave loading of submicrosecond duration

The results of stress wave measurements under shock-wave loading of specimens of zirconium alloy W110 of thickness from 0.5 to 8 mm at normal and elevated temperatures are presented. The duration of shock loading pulses varied from ∼0.05 to 1 µs with amplitude from 3.4 to 23 GPa. The free surface velocity profiles were registered by interferometric velocimeters VISAR and PDV with nanosecond time resolution. The results of measurement of the elastic precursor decay were used to determine the plastic strain rate behind its front, which decreases from 106 s−1 at a distance of 0.46 mm to 2 × 104 s−1 at a distance of 8 mm in the course of propagation. The spall strength values at normal and elevated temperatures were obtained, and its dependencies on the strain rate in the range from 105 to 106 s−1 were constructed. The three-wave configuration of the shock wave caused by the polymorphic transformation as α → ω was registered under a shock compression pressure of 10.6 GPa.