Experimental study on the effects of interface dip angle on deformation failure of combined limestone-coal specimens.

Uniaxial compression experiments of limestone-coal specimens at different inclination angles (0, 15, 30, 45, and 60°) were conducted using acoustic emission and three-dimensional, extension test digital image correlation, and full-field strain measurement systems to examine how dip angles affect deformation failure. The findings indicate that: (1) specimen groups demonstrate plastic yield characteristics in the pre-peak stage. However, slight variations exist due to inclination angles. (2) The localization zone for deformation evolution closely correlates to primary crack initiation and propagation within coal specimens and to slipping at the rock's and coal's interface. Failure in the coal specimen triggers rebound deformation in limestone when the rock coal inclination angle is set at 15°. Both the rebound deformation amount and its rate exhibit upward trends as a function of the inclination angle. (3) The percentage of pre-peak elastic property density in the combined specimen is augmented from 98.56 to 88.08% as the inclination angle augments and reduces to 75.80%. External energy's conversion into missile performance shows an initial increase followed by a decrease. (4) The energy rate of the acoustic emission (AE) signal exhibits distinct temporal characteristics in the combined specimen that can be associated with quiet, active, and sudden increases.

Elastic, Piezoelectric Coefficients, and Internal Frictions of a Single Alpha-Quartz Crystal Determined by Partial-Electrode Electromechanical Impedance Spectroscopy.

In this work, all independent elastic coefficients, piezoelectric coefficients, and internal frictions of a single alpha-quartz crystal are determined at room temperature using our recently proposed partial-electrode electromechanical impedance spectroscopy (PE-EMIS). In PE-EMIS, the rectangular parallelepiped quartz sample with two small partial electrodes fabricated on a corner is self-excited/sensed. The conductance spectrum (equivalent to the acoustic resonance spectrum) measured by an impedance analyzer under a free boundary condition is noiseless, allowing the first 100 eigenmodes ranging from 50 to 310 kHz to be accurately fit. To avoid mode misidentification, the off-plane displacement distributions of the quartz sample under different eigenmodes are determined using a scanned-laser vibrometer. The resonance spectrum measured by a traditional sandwich-like resonant ultrasound spectroscopy (RUS) apparatus is also presented for comparison, and the results show that the clamping force in sandwich-like RUS shifts the sample's resonance frequencies, causing 13% and 75% overestimations for the piezoelectric coefficients e11 and e14, respectively. In comparison with the RUS, our proposed PE-EMIS is more effective and convenient and will be widely used for characterization of piezoelectric crystals.

Analysis of the dust-methane two-phase coupling blowdown effect at different air duct positions in an excavation anchor synchronous tunnel.

Bolter miners are being increasingly used. Unfortunately, this mining technology causes a considerable amount of air pollution (especially by methane and dust) during excavation. In this study, the multiphase coupling field of airflow-dust-methane for different distances between the pressure air outlet and the working face (Lp) was simulated by using the FLUENT software. The migration law of pollutants in the multiphase coupling field was analyzed, and the distance parameters between the pressure air outlet and the working face were optimized. Finally, the simulation results were verified based on the field measurement results. We found that the blowdown effect was more obvious when 14 m ≤ Lp < 16 m compared with other conditions. The peak value of dust concentration within this distance range was the smallest (44.4% lower than the highest peak value, which was verified when Lp = 18 m), while the methane concentration was < 0.6%. A high-concentration area (where methane concentration > 0.75%), identified near the walking part of the bolter miner, was 13 m shorter than the largest (when Lp = 18 m). Therefore, we determined that the optimal blowdown distance would be 14 m ≤ Lp < 16 m. Within this range, the dust removal and methane dilution effects are optimal, effectively improving the tunnel air quality and providing a safe and clean environment for mine workers.

Monitoring of thermal stress in metal plates by using bonded shear horizontal wave piezoelectric transducers.

Thermal stress is one of the major causes of failure of engineering structures and its measurement has attracted more attention in recent years. The ultrasonic wave method is very promising in stress measurement due to its non-destructive nature and easy manipulation. The traditional ultrasonic wave transducers require a coupling medium which would introduce large repeatability errors in travel time measurement and thus in the measured stress. In this work, a methodology based on bonded shear horizontal (SH) guided wave piezoelectric transducers was developed to monitor thermal stress in metal plates. The adhesive bonding between the transducer and the specimen ensures the repeatability in travel time measurements, and the strain gauges are also employed to monitor the wave path length. The dispersive equation of acoustoelastic SH wave propagating in an isotropic medium under the uniaxial stress is derived. Both the uniaxial tension test and thermal modulation test have been performed in aluminum and steel plates. The results show that the acoustoelastic constants of the SH0 wave are identical to that of the shear bulk wave as predicted by the acoustoelastic theory and the thermal stress measured from -60 °C to 100 °C by the proposed method has a very good repeatability (better than 2 MPa) in both the aluminum and steel plates. Considering the convenience and reliability of the bonded SH0 wave piezoelectric transducer, the proposed method is very promising for monitoring of thermal stress in engineering structures, such as rails, etc.

Seepage Characteristics of Mixed-Wettability Porous Media on the Phase-Field Model.

Clarifying the microscale gas-water flow behaviors in a mixed wettability reservoir is of great importance for underground engineering. A numerical model of mixed wettability based on circular particles was constructed using the MATLAB stochastic distribution program, and the gas-water flow was simulated based on the phase-field method. The Navier-Stokes equations were solved by the finite element method. The work analyzed the effects of the content of heterogeneous wetting particles, wettability, and inversed wettability of the matrix on the flow path and pressure distribution of the mixed wettability model. Besides, the two-phase flow behaviors were evaluated in microscale mixed-wettability porous media. The simulation results revealed that (i) the residual saturation of the gas phase showed a positive correlation with the hydrophobic particle content, and closed gases only existed in isolated pore channels with small content. Isolated closed gases gradually connected as the content increased. (ii) The residual gas content in the corner and tail end increased as the hydrophobicity of particles increased in hydrophilic matrices. Hydrophobic matrices showed a negative correlation, with the greatest pressure drop due to capillary resistance and step changes in the neutral-hydrophobic transition zone. (iii) Water-phase breakthrough time and gas-phase residual saturation showed a negative correlation change. The more space occupied by the gas phase, the faster the water-phase breakthrough. Moreover, the saturation no longer changes after the breakthrough. The work provides a guideline for determining the dominant flow path of phase displacements and the distribution of residual phases.

Determining Full Matrix Constants of Piezoelectric Crystal From a Single Sample Using Partial Electrode Electromechanical Impedance Spectroscopy.

To determine all the material constants of a piezoelectric crystal using the IEEE resonance method or ultrasonic method, several samples with specific geometries and orientations are required, and the obtained results may be somewhat self-contradictory. The resonant ultrasound spectroscopy (RUS) can determine full material constants of a single piezoelectric sample by matching the numerically computed eigenfrequencies to the measured resonance spectrum. However, typically the usage of PZT transducers for excitation and reception makes the testing complicated and may add additional mass and damping. In this work, we propose a new method called partial electrode electromechanical impedance spectroscopy (PE-EMIS), which can obtain all the elastic, piezoelectric constants, and related internal frictions of a piezoelectric crystal by just using a single sample without additional transducers. In PE-EMIS, two small PEs are fabricated on one corner of a piezoelectric sample, and the sample's resonance frequencies, along with the internal frictions of the k th eigenmode, can be accurately obtained from the conductance spectrum measured using an impedance analyzer. The PE-EMIS experiment is carried out on a rectangular parallelepiped PZT-4 piezoelectric ceramic, and the extracted material constants are highly repeatable. Three of the extracted elastic constants ( c11E , c33D , and c66E ) are validated by the traditional wave propagation method. Due to its simplicity, convenience, and accuracy, the proposed PE-EMIS is expected to be widely used for characterization of piezoelectric materials in near future.

Nonlinear electromechanical impedance spectroscopy: A powerful tool for studying amplitude dependent internal frictions of solids.

Strain amplitude dependent effects of materials/structures are very important in the field of material science and engineering and have been found to be extremely sensitive to defects or damage. In this work, a nonlinear electromechanical impedance spectroscopy (N-EMIS) technique is proposed to characterize the amplitude dependent internal frictions (ADIFs) and modulus defects (or resonance shift) of materials. First, a new experimental scheme called the on/off parallel resistor capacitor circuit is proposed to measure the N-EMIS of a piezoelectric transducer (PZT)-specimen composite system under high driving levels. Second, based on the N-EMIS, the formulas for calculating the ADIF are derived and validated by vibration measurement using a laser vibrometer. To further enlarge the strain amplitude, a PZT-stepped horn-specimen three-component system is then introduced, with which the maximum strain amplitude can reach 10-3. Finally, ADIF tests are conducted on polycrystalline pure copper and 1045-steel. The results show that at high strain levels, the internal frictions of both materials can reach several times than those at low driving levels, while the modulus drops only slightly. The proposed N-EMIS technique can effectively assess the strain amplitude dependent properties of materials and is expected to be widely used in the near future for evaluation of plasticity, fatigue, and damage.

An omnidirectional piezoelectric transducer for selective excitation and reception of high-order shear horizontal waves.

Guided wave tomography, as an advanced structural health monitoring (SHM) method, has offered a feasible solution to wall thickness quantification which is essential in petrochemical industries. However, previously used low-frequency Lamb waves (A0 and S0) limit the resolution of tomography. Recently, the first-order shear horizontal guided wave (SH1) was found very promising in tomography for its capability in resolution improvement. However, the SHM-required omnidirectional piezoelectric transducers for selectively generating and receiving the SH1 wave, namely OSH1-PT, are not available yet. In this work, a general method was developed to design an OSH1-PT based on the thickness-poled PZT half-ring configuration. Firstly, the excitation function of the OSH1-PT was explicitly derived and validated through finite element simulations. Secondly, a design formula was obtained and used to determine the size of the OSH1-PT. Then, the designed OSH1-PT was fabricated and tested by using a 2D laser Doppler vibrometer. Significant mode selectivity was observed in all directions (0 âˆ¼ 90°) with the excited SH1 to SH0 ratio higher than 15 dB. Pitch-catch tests were conducted from 400 âˆ¼ 520 kHz and the received SH1 to SH0 ratio was found higher than 19 dB at all frequencies and reached its maxima of 30.7 dB at 490 kHz, which is very close to the designed working frequency of 500 kHz. Finally, an OSH2-PT was theoretically designed and validated by FE simulations. Due to its simplicity and effectiveness in designing the OSHn-PT, the proposed method is expected to pave the road to wide applications of high-order SH wave tomography.

Formulation development of anti-rheumatoid gel of Saraca asoca (Roxb. ) De Wilde hydroalcoholic extract containing eucalyptus oil and peppermint oil as penetration enhancer

Abstract In the present research investigation, various concentrations of hydro-alcoholic extract of Saraca asoca (Roxb.) De Wilde (family: Caesalpinaceae) dried bark and carbopol polymer at different temperature ranges were optimized for the preparation of gel formulation. Natural penetration enhancers, v.i.z., eucalyptus oil and peppermint oil were incorporated separately in the extract based gel formulations to study the rate of drug permeation across egg membrane, using franz diffusion cell. In vitro anti-arthritis potential of the formulations was also studied using inhibition of albumin denaturation, antiproteinase activity and membrane stabilization method. As per the results of current study, it is established that S. asoca dried bark hydroalcoholic extract based gel prepared using peppermint oil as penetration enhancer exhibited good permeation rate of 8.48% at the end of 3 h. The percentage inhibition of proteins by antiproteinase method at concentration of 50 µg/ml was 50.01±1.00% which was close to 53.92±0.99% as shown by the standard drug, Diclofenac. Also, the percent protein inhibition determined using membrane stabilization method was found to be 49.70±1.00%, however, it was 63.32±0.94% for the standard drug, Diclofenac. Hence, it is concluded that peppermint oil may act as a good candidate for the preparation of potent anti-rheumatic gel preparations.

Shear horizontal wave transducers for structural health monitoring and nondestructive testing: A review.

Shear horizontal (SH) waves are of great importance in structural health monitoring (SHM) and nondestructive testing (NDT), since the lowest order SH wave in isotropic plates is non-dispersive. The SH waves in plates, circumferential SH waves and torsional waves in pipes have remarkable resemblances in dispersion characteristics and wave structures, so the latter two can also be called as SH waves in pipes. This paper reviews the state-of-the-art research on SH wave transducers for SHM and NDT. These transducers are grouped into the following categories: Lorentz-force-based electromagnetic acoustic transducers (EMATs), magnetostrictive EMATs, shear wave piezoelectric wedge transducers, thickness-shear piezoelectric transducers and face-shear piezoelectric transducers. The working principles, applications, merits and limitations of different kinds of SH wave transducers are summarized, with a focus on discussing the various configurations for exciting and receiving directional, omnidirectional SH waves in plates and torsional waves in pipes. This paper is expected to greatly promote the applications of SH waves in SHM, NDT and the related areas such as elastic metamaterials.

The prescription patterns and safety profiles of oral non-steroidal anti-inflammatory drugs in China: an 8-year real-life analysis.

BACKGROUND: This study aimed to evaluate the prescription patterns and safety profiles of oral nonsteroidal anti-inflammatory drugs (NSAIDs) in three Chinese hospitals. METHODS: The study analyzed the data of 50,732 patients who were prescribed oral NSAIDs from July 1, 2012 to August 31, 2019. The characteristics of these patients, the prescription patterns of NSAIDs, and the drug-related safety profiles were evaluated. RESULTS: Oral NSAIDs were prescribed to patients of all ages. Of the patients, 81.88% were prescribed NSAIDs on only one occasion, and 91.64% were prescribed one type of NSAID only. The combination of different NSAIDs accounted for 2,360 person-times. Orthopedic departments most commonly used selective cyclo-oxygenase-2 (COX-2) inhibitors, while emergency departments most commonly used traditional NSAIDs. The incidences of gastrointestinal (GI) complications, cardiovascular (CV) events, and newonset hypertension were lower in patients treated with selective COX-2 inhibitors than those treated with traditional NSAIDs and NSAID combinations (P<0.05). In relation to selective COX-2 inhibitors, incidences of new-onset hypertension were lower in patients treated with imrecoxib than those treated with other types of selective COX-2 inhibitors (P=0.0102). CONCLUSIONS: In respect of the at-risk patients (i.e., those with related disease, such as GI complications, CV events or other risks), the patterns with which oral NSAIDs were prescribed was not standardized. In terms of adverse effects, selective COX-2 inhibitors represent a better choice than traditional NSAIDs and NSAID combinations.

Tailoring Artificial Mode to Enable Cofired Integration of Shear-type Piezoelectric Devices.

Low-temperature cofired ceramic technology is the prerequisite for producing advanced integrated piezoelectric devices that enable modern micro-electromechanical systems because of merits such as high level of compactness and ultralow drive voltage. However, piezoceramic structure with shear-type outputs, as a most fundamental functional electronic element, has never been successfully fabricated into multilayer form by the cofired method for decades. Technical manufacture requirements of parallel applied electric fields and polarization are theoretically incompatible with intrinsically orthogonal orientations in naturally occurring shear modes. Herein, inspired by the philosophy of building metamaterial from identical unit cells, an artificial prototype device with distinctive patterned electrodes and arrayed piezoceramic subunits is designed and fabricated, which is proved to perfectly generate synthetic face shear deformation. At the same drive voltage, an enhanced shear-type displacement output by over an order of magnitude is observed beyond previous d15-mode bulk elements. Further results of guided wave-based structural health monitoring and force sensing confirm that the methodology wipes out a tough piezoelectric technique barrier, and promises to fundamentally enlighten advances of integrated shear-mode piezoelectric devices for augmented actuation, sensing, and transduction applications.

Measurement of elastic moduli and internal frictions using modified piezoelectric ultrasonic composite oscillator technique with large frequency mismatch.

In this Note, first, the calculation errors of elastic moduli and internal frictions using the explicit formulas in the traditional and modified piezoelectric ultrasonic composite oscillator technique (PUCOT and M-PUCOT) are comparatively studied when the frequency match condition is not satisfied. Then, new implicit formulas free of frequency match are proposed for the three-component M-PUCOT. Finally, the measurement results on a lead zirconate titanate ferroelectric ceramic from room temperature to 500 °C by using the pervious explicit formulas and the new implicit formulas are compared. The results show that when the frequency mismatch is within 15%, the induced error by using the explicit formulas is less than 0.5% and 2.5% for moduli and internal frictions, respectively. When the frequency mismatch is over 15%, the implicit formulas are suggested to improve the accuracy of M-PUCOT.

A high-sensitivity and long-distance structural health monitoring system based on bidirectional SH wave phased array.

When estimating a structural health monitoring (SHM) system, its defect sensitivity and area/distance coverage are most important factors. For commonly used guided wave sparse array system, it usually requires a reference state as the baseline which is not available in many cases. In comparison, phased array technique typically does not need the baseline in simple structures and it had been successfully used in nondestructive testing (NDT). However, currently developed phased array systems employed omni-directional transducers routinely, where the wave energy is distributed equally along all directions thus it is not favorable for long-distance detection. In this work, bidirectional piezoelectric transducers were used to form a linear phased array system, which can generate/receive shear horizontal (SH) wave with high energy concentration. Firstly, the configuration of the employed transducer composed by antiparallel d15 piezoelectric strips (APS) was presented. Then the total focusing method (TFM) employed for defect detection was introduced. After validating the radiation pattern of SH wave generated by the APS, the properties of beam steering for the proposed phased array was investigated. Finally, experiments were carried out to validate its performance in detection of various defects. Results indicated that even for a 1 mm through-thickness hole 700 mm away, the proposed phased array system can still detect it accurately, which is much better than previous SHM systems. Dual defects including a crack and a hole can also be clearly detected without baseline. The high-sensitivity of the proposed system was attributed to the employed bidirectional transducer which can generate non-dispersive SH0 wave with high energy concentration. This proposed SH wave phased array system will provide a high-performance SHM method for plate-like structures.

Long-distance structural health monitoring of buried pipes using pitch-catch T(0,1) wave piezoelectric ring array transducers.

In modern industries, long-distance guided wave inspection has been routinely used for various types of pipelines. The usage of T(0,1) wave is always of great interests since it is the only non-dispersive wave mode in pipes. In this work, a pair of pitch-catch piezoelectric ring arrays were proposed for long-distance structural health monitoring (SHM) of buried pipes. Firstly, the working principle of the proposed transducer was introduced. Next, the performances of thickness-shear (d15) and face-shear (d24) modes based piezoelectric ring transducers in T(0,1) wave generation and reception were comparatively tested. It was found that at most frequencies, it is best to employ the d15 ring as the exciter and the d24 ring as the receiver. Then, the signal-to-noise ratio (SNR) of the generated T(0,1) wave and its attenuation in pipes with different coating conditions were investigated to estimate the detectable distance using the proposed transducer. Results showed that after applying acoustical isolation layer on pipes, the proposed ring transducers can inspect buried pipes over 20 m. Finally, the performance of the ring transducers in defect detection was validated. This work is expected to provide a promising solution to long-distance SHM of buried pipes.

TIMD4 exhibits regulatory capability on the proliferation and apoptosis of diffuse large B-cell lymphoma cells via the Wnt/ß-catenin pathway.

BACKGROUND: Prior studies have noted the importance of T cell immunoglobulin and mucin domain containing 4 (TIMD4) in various diseases and its functions on cell malignant behaviors. However, the biological function of TIMD4 in diffuse large B-cell lymphoma (DLBCL) is unknown. METHODS: Relative expression of TIMD4 was analyzed based on the GSE56315 array including 88 cases of human tissues. TIMD4 expression in cells was detected using a quantitative reverse transcriptase-polymerase chain reaction and western blot experiments. Cell proliferation was measured using the cell counting kit-8 (CCK-8) assay and apoptotic properties were assessed through the detection of related proteins by western blotting. The underlying molecular mechanism of TIMD4 in DLBCL was predicted and confirmed using KEGG enrichment analysis and western blotting. RESULTS: The results indicate that TIMD4 is overexpressed in DLBCL tissues and the poor prognosis of DLBCL patients is significantly linked with the higher TIMD4 expression. The loss-of-TIMD4 experiment in CYP6D reveals that knockdown of TIMD4 blocks cell growth and accelerates cell apoptosis, whereas the gain-of-TIMD4 experiment in Raji cells suggests that up-regulation of TIMD4 promotes cell proliferation and inhibits cell apoptosis. The activity of the Wnt/ß-catenin pathway is mediated by the TIMD4 expression in DLBCL cells. CONCLUSIONS: These findings demonstrate that TIMD4 is up-regulated in patients with DLBCL and the regulatory effects of TIMD4 on cell proliferation and apoptosis are associated with the Wnt/ß-catenin pathway, posing a novel target for DLBCL therapy.

Quick and repeatable shear modulus measurement based on torsional resonance using a piezoelectric torsional transducer.

Shear modulus is one of the fundamental mechanical properties of materials, while its quick and accurate measurement is still a challenge. Here we proposed a method for shear modulus measurement based on torsional resonance using a piezoelectric torsional transducer bonded on a cylindrical specimen. Firstly, the torsional transducer was introduced which consists of two thickness poled, thickness shear (d15) piezoelectric half-rings. Secondly, the equivalent circuit of the transducer-cylindrical specimen system is derived and the shear modulus can be explicitly obtained using the torsional resonance frequency. The internal friction can also be obtained, which is calculated by using an approximate formula. Then, shear modulus and internal friction measurement on four materials including 1045 steel, 6061 aluminum, quartz glass and PMMA were conducted. Results indicate that all the measured shear moduli are consistent with the reference values in literatures. The repeatable error in shear modulus measurement is within 0.2%, which is very desirable. Finally, shear modulus measurement scheme under high (or low) temperature is proposed using a frequency-match quartz glass bar as the thermal insulator. Measurement results on the 6061 aluminum indicates that from room temperature to 500 °C, the shear modulus decreases from 26.8 GPa to 16.6GPa. The proposed method is very reliable and quite convenient, which can be widely used in near future.

A modified piezoelectric ultrasonic composite oscillator technique for simultaneous measurement of elastic moduli and internal frictions at varied temperature.

In this work, a modified piezoelectric ultrasonic composite oscillator technique (M-PUCOT) is developed for measuring a material's elastic moduli and internal frictions, as a function of temperature. Different from the traditional PUCOT that employs two quartz bars as the drive and gauge, here, a single small piezoelectric transducer (PZT) ring is used to drive and sense longitudinal or torsional vibration in a cylinder specimen. Because of the strong piezoelectric effect and relatively large bandwidth of the PZTs compared to their quartz counterpart, the frequency match condition between the transducer and the specimen is not required in this M-PUCOT. For high temperature measurement, a fused quartz spacer, whose resonance frequency matches the specimen's, is bonded between the transducer and the specimen to provide thermal insulation. First, the united equivalent circuit of the transducer- (spacer) -specimen composite system was derived. Then, Young's modulus, longitudinal friction, shear modulus, and torsional friction were explicitly obtained by measuring the resonance frequency and antiresonance frequency of the 2- or 3-component system's electrical susceptance curve using an impedance analyzer. The accuracy of this method was validated both by measuring the system's amplitude-frequency curves using a laser vibrometer and through finite element simulations. The repeatability error of the M-PUCOT is only ∼0.2% for moduli measurement and ∼2.5% for internal friction measurement, which is very promising for studying the moduli and internal friction variations during damage, fatigue, and phase transitions. Finally, the M-PUCOT was employed to measure the variations in moduli and internal frictions of an Fe64Ni36 Invar alloy from room temperature to 500 °C. Results show that above the ferromagnetic phase transition temperature Tc, both moduli reach their maxima, and both internal frictions reach their minima. The proposed M-PUCOT is expected to be widely used in the near future for its quick measurement, high repeatability, and low cost.

A tunable bidirectional SH wave transducer based on antiparallel thickness-shear (d15) piezoelectric strips.

Guided wave based defects inspection is very promising in the field of structural health monitoring (SHM) and nondestructive testing (NDT) due to its less dissipation and thus long distance coverage. In comparison with the widely used Lamb waves, shear horizontal (SH) waves are relatively simple but less investigated probably due to the traditional notion that SH waves were usually excited by electromagnetic acoustic transducers (EMAT). In this work, we proposed a tunable method to excite single-mode bidirectional SH waves in plates using antiparallel thickness-shear (d15) piezoelectric strips (APS). The proposed SH wave driving mechanism here is similar to that by using the periodic permanent magnetics (PPM) based EMAT with the period of strips equal to half of the wavelength. Both finite element simulations and experiments were conducted to validate this transducer in excitation of bidirectional SH waves. Results show that the Lamb waves excited by single piezoelectric strip can be suppressed very well. The radiation angle of the excited bidirectional SH wave can be reduced by extending the strip length, increasing the driving frequency or using more strips. Moreover, the APS transducer can selectively excite SH1 wave and suppress the SH0 wave at 174 kHz and 273 kHz in a 10 mm-thick aluminum plate. Considering its simple structure, flexible design and low excitation energy, the APS SH wave transducer is expected to be widely used in near future.

A high-resolution structural health monitoring system based on SH wave piezoelectric transducers phased array.

Guided wave based structural health monitoring (SHM) has been regarded as an effective tool to detect the early damage in large structures and thus avoid possible catastrophic failure. In recent years, Lamb wave phased array SHM technology had been intensively investigated while the inherent multi-mode and dispersive characteristic of Lamb waves limits its further applications. In comparison, the fundamental shear horizontal (SH0) wave is non-dispersive with uncoupled displacements and thus more promising for defect detection. In this work, we proposed an SH0 wave linear phased array SHM system based on our recently proposed omni-directional SH wave piezoelectric transducer (OSH-PT). Firstly, the working principle of the phased array system was presented and the total focusing method (TFM) was employed for imaging. Then the SH0 wave mode generated by the OSH-PT was confirmed in a defect-free plate. Finally, experiments were carried out to examine the performances of this SHM system. Results showed that the proposed system can detect a through-thickness hole as small as 2 mm in diameter with the location error only about 6.3 mm. Moreover, the proposed phased array system can also detect multi-defects. Due to its low working frequency and thus low attenuation, the proposed phased array system is capable of monitoring large structures. This work will lay the foundations of SH wave based phased array SHM.