Stress Wave Propagation Research Articles

Embedded PZT aggregates for monitoring crack growth and predicting surface crack in reinforced concrete beam

This study proposed an approach to monitor the cracks growth process of reinforced concrete beam using embedded piezoelectric aggregates. The principle of stress waves propagation in concrete cracks was analyzed, and a damage index was introduced to estimate the crack damage degree in concrete structure on this basis. A stepwise loading was applied to the reinforced concrete beam, and it was divided into three areas according to the different force conditions. Moreover, the piezoelectric aggregates were fabricated, and four aggregates were embedded into the specimen to monitor its each area by active monitoring technique. The results of the experiment demonstrated that the proposed damage index could realize the dynamic monitoring and damage degree evaluation of the specimen. Furthermore, this index could forecast the occurrence of surface crack and warn the collapse of the structure in advance. The proposed method was also verified by high-speed camera and image processing technique.

Stress waves in a lightweight substrate plate actuated with piezoelectric layers under sinusoidal time-dependent pressures

The dynamic behavior of cantilever lightweight substrate plates actuated by surface layers of piezoceramic with a potential application as an energy harvester is presented in this paper. The utilized passive substrate is made of nanocomposite plates with embedded pores where both nanofillers and pores are functionally graded (FG) distributed. Carbon nanotubes (CNTs) are employed as the enhancement part of the substrate whereas their major distribution drawback which is CNT accumulating in some clusters has been taken into account by employing a modified Eshelby's approach for the calculation of nanocomposite's material properties. The proposed structure is assumed under a half wave of sinusoidal time-dependent pressure to model an impact load and by providing a meshless solution, its dynamic behavior in a framework of stress wave propagation analysis has been conducted. By exploring porosity and CNT effects, the achieved results revealed that there is an optimum value for porosity volume fraction which offers the highest wave frequency. Moreover, it was observed that although there is a great difference between stress waves in structures with pure polymeric and nanocomposite substrates, involving higher CNT amounts without a perfect distribution would considerably reduce the enhancement efficiency of CNTs due to accumulating CNTs in some clusters.

Experimental study on dynamic tensile performance of Q345 structural steel considering thickness differences

This paper experimentally investigates the dynamic tensile performance of Q345 structural steel, especially taking the tested coupon thickness as the key parameter. The tests of low alloy Q345 structural steel widely used in China are carried out under intermediate strain rate level loading of 101s−1 to 102s−1, as well as under static loadings for comparison. A purpose-built experimental arrangement is set up for dynamical coupon test, which can convert the compression triggered by the impact hammesr into rapid tension action. Firstly, the reliability of the proposed experimental technique and measurement method is verified by evaluating the influence of inertia and stress wave propagation. Then, a detailed description of the test results concerning the effect of strain rates on steel material is provided, including failure modes, the yield strength, ultimate strength, elongation, and dynamic increase factors (DIF) of the specimens. Additionally, the results of previous tests on the dynamic properties of steel materials and their relationships to evaluate the validity of the test results are summarized and compared, and the levels and sources of DIF inconsistency are also discussed. Based on the test results, the modified Cowper-Symonds formula was proposed to predict the DIFy-ε̇ relationship curve of yield strength of Q345 steel considering the size effect. Meanwhile, the applicability of Malvar formula for predicting ultimate strength by DIFu-ε̇ relationship curve of Q345 steel with different sizes was verified.

Mechanical behavior of single-layer graphdiyne via supersonic micro-projectile impact

The mechanical behavior of single-layer graphdiyne (SLGDY) subjected to high-velocity micro-ballistic impacts is analyzed by molecular dynamics (MD) simulations. The ballistic limits of SLGDY is obtained for the first time. The temperature deterioration effects of the impact resistance are also investigated. The results show that the ballistic limits can reach 75.4% of single-layer graphene (SLGR) at about 1/2 density, leading to approximately the same specific energy absorption (SEA) as SLGR. The ballistic limits of SLGDY and SLGR with single atomic thickness agree with the predictions of macroscopic penetration limits equations, implying the applicability of continuum penetration theories for two-dimensional (2D) materials. In addition, the dynamic responses involving stress wave propagation, conic deformation, and damage evolution are investigated to illuminate the mechanisms of the dynamic energy dissipation. The superior impact resistance of SLGDY and SLGR can be attributed to both the ultra-fast elastic and conic waves and the excellent deformation capabilities. This study provides a deep understanding of the impact behavior of SLGDY, indicating it is a promising protective material.

Identification of corrosion formation in CORTEN steel using acousto-ultrasonic approach and deep learning

PurposeThe acousto-ultrasonic approach is used for propagating stress waves through different configurations of CORTEN steel specimens. The propagated waves are recorded and analysed by piezoelectric sensors. The purpose of the study is to study the characteristics of the CORTEN steel by analysing the propagated waves.Design/methodology/approachTo investigate the attenuation in acoustic wave propagation due to the corrosion formation in CORTEN steel specimens and to train a neural network model to classify the attenuated acoustic waves automatically.FindingsDue to the corrosion formation in CORTEN steel specimens, attenuation is observed in amplitude, energy, counts and duration of the propagated waves. When the waves are analysed in their time-frequency characteristics, attenuation is observed in their frequency and spectral energy.Originality/valueThe corrosion formation in CORTEN steel can automatically be analysed by using the acousto-ultrasonic approach and the trained deep learning neural network.

Monitoring Stress State of H-Shape Steel Using Ceramic Piezoelectric Sensor: A Feasibility Study

To monitor the stress state and yield capacity of H-beams across their entire service process, a real-time monitoring method based on the energy signal response of ceramic piezoelectric sensors is proposed in this paper. The method is applied to conduct loading experiments on H-beams under different load values and web heights. Then, the amplitude and energy of the piezoelectric signals under the two working conditions are compared and analyzed, and the finite element analysis results are verified. The experimental results show that the time-domain waveform energy index increases under an increase in web height or load. Taking the H-section steel member with a web height of 10 cm as an example, when the load value is less than 500 kN/m, the energy index increases (on average) by ~10.5% for every 100 kN/m load increase; when the load value exceeds 500 kN/m and is below 675 kN/m (yield load), the same load increases the energy index by ~13.4%. Meanwhile, a 1 cm average increase in web height increases the energy index by ~14.6%. The finite element simulation results indicate that the ceramic piezoelectric sensor load increases under external load increases up to the yielding load. Because the stress state at the sensor location directly determines the stress wave propagation, the critical buckling loads of H-beams can be predicted using the energy index.

Experimental Study on the Dynamic Mechanical Properties of a Jointed Rock Mass under Impact Loading

The propagation law of blast stress waves in jointed rock masses is closely related to the characteristics of the joint filling medium. The water content and thickness of the filling medium affect the propagation characteristics of the blast stress wave in the joint surface. Based on similarity theory, mortar-red clay-mortar composite specimens with different moisture contents (36%, 39%, 42%, and 45%) and medium thicknesses (3 mm, 6 mm, and 9 mm) were prepared with red clay as the filling medium. The dynamic uniaxial compression test of the specimen under different strain rates was carried out by using a variable cross-section split Hopkinson compression bar with a diameter of 50 mm. The effects of strain rate, moisture content, and medium thickness on the stress wave propagation characteristics, dynamic stress-strain curve, peak stress, crushing energy consumption density, and crushing characteristics of mortar-red clay-mortar composite specimens were analyzed. The results show that the blocking effect of joints on stress waves increases significantly with increasing filling medium thickness and water content. With increasing strain rate, the peak stress and energy of the composite specimen increase and there is an obvious strain rate effect. With the increase in the thickness and moisture content of the filling medium, the peak stress, dynamic elastic modulus, energy consumption density per unit volume, and crushing degree of the specimen gradually decrease and the nonlinear deformation is more obvious. There is a good linear relationship between the peak stress and the thickness and moisture content of the filling medium. The existence of joints greatly weakens the damage effect of stress waves on the specimens behind the joints, and with the increase in the thickness and water content of the filling medium, the degree of damage to the specimens behind the joint surface decreases under the same impact pressure and the weakening effect becomes increasingly significant.

Self-consistent homogenization-based parametrically upscaled continuum damage mechanics model for composites subjected to high strain-rate loading

This paper develops a Parametrically Upscaled Continuum Damage Mechanics (PUCDM) model for carbon fiber/epoxy matrix composites subjected to high strain-rate loading. The PUCDM model for predicting high strain-rate induced deformation and damage evolution at the macroscopic scale, explicitly incorporates microstructural morphology and micro-inertia in its constitutive coefficients. It is developed using self-consistent homogenization that uses a concurrent multiscale model to account for the effect of micro-inertia and stress wave interaction with the microstructure. The concurrent model embeds a statistically equivalent representative volume element (SERVE) of the microstructure in an exterior domain, whose constitutive and damage response are described by the PUCDM model. Micromechanical modeling for the composite microstructure involves a unified cohesive zone enhanced phase-field damage model for fiber-matrix interface debonding, fiber breakage, and matrix cracking. The PUCDM model parameters for the upscaled domain are determined through micro-macro-scale energy equivalence, along with traction reciprocity and displacement continuity at the SERVE-exterior domain interface that are enforced using a Lagrange multiplier-based approach. Simulations using the concurrent model analyze stress wave propagation and damage evolution in composite microstructures with three different fiber volume fractions at multiple strain rates in the range of 102 − 105 s−1. The fiber volume fraction and spatial distributions affect the overall stiffness and damage evolution in the PUCDM model. Results of the analysis demonstrate the need for representation of micro-inertia, strain rates and microstructure morphology in the PUCDM-based stiffness and damage model parameters for high strain-rates above [Formula: see text].

Vibration effect and ocean environmental impact of blasting excavation in a subsea tunnel

Drill-blast method is one of the important methods in the current subsea tunnel excavation construction. Controlling the vibration effect during blasting construction and its impact on the marine environment has been a key topic in the construction of subsea tunnels. This paper takes the Xiamen subsea tunnel excavation and blasting project as the background, combines blast vibration monitoring in the tunnel and underwater sound pressure testing in seawater, analyzes the attenuation law of subsea tunnel blast vibration propagation along the rockmass, studies of the characteristics of shock waves formed in water following the propagation of blast stress waves to seawater. Based on the dynamic finite element numerical calculation, the impact of blasting vibration effect of mainline tunnel on the adjacent built service tunnel structure and the characteristics of shock wave pressure distribution in water excited by blasting vibration are analyzed. Considering the influence of the burial depth of tunnel blasting source, a mathematical prediction model of the attenuation law of underwater sound pressure in water caused by subsea tunnel blasting is established. Based on the pressure control standard of marine organism safety, the control range of marine organism safety under the influence of subsea tunnel blasting is proposed.

Dynamic Response Characteristics of Roadway Surrounding Rock and the Support System and Rock Burst Prevention Technology for Coal Mines

Anchor cables (bolts) act as the main support system and play an important role in improving the rock burst resistance and stability of the roadway surrounding the rock. In this study, the dynamic response characteristics of the roadway surrounding the rock and the support system under different shock intensities were investigated. The following findings were obtained. The stress wave propagation process under dynamic shock was divided into a stress vibration initiation stage, a stress fluctuation stage, and a stress adjustment stage. In the stress vibration initiation stage, the surface mass of the roadway surrounding the rock started to vibrate, and the pretension of the anchor cables (bolts) was reduced; in the stress fluctuation stage, the failure of the roadway surrounding the rock intensified, and the anchor cables (bolts) were damaged to some extent; and in the stress adjustment stage, the roadway deformation of the surrounding rock and the axial forces of the anchor cables (bolts) tended to stabilize. As the dynamic shock intensity increased, the vibration velocity, displacement increment, and acceleration amplitude of the mass of the roadway surrounding the rock increased exponentially. The critical shock energy of the roadway surrounding the rock was 105 J, above which the damage to the rock was aggravated. The larger the pretension of the anchor cables (bolts) was and the higher the dynamic shock intensity was, the more severe the damage to the anchor cables (bolts) was. Given the dynamic response characteristics of the roadway surrounding the rock and support elements under shock, a full anchor cable yielding support technology is proposed to effectively control the stability of the roadway surrounding the rock under dynamic shock, providing a reference for the construction of the support systems for preventing rock bursts in similar roadways.

Elastoplastic stress wave propagation in functionally graded material due to combined compression and shear

In the present paper, an analytical model for the propagation of stress waves in a functionally graded half-space subjected to combined compression and shear impact loading is established. The functionally graded materials (FGMs) based on the elastic–plastic model (the Tamura–Tomota–Ozowa model) are assumed to be continuously graded according to a power-law function of the volume fractions of the constituents. Based on generalized characteristics theory, the characteristic wave speeds were obtained and analyzed. The finite difference method was implemented to discretize the governing equations. Typical numerical examples for FGMs with positive and negative gradients are presented. The numerical examples reveal that the FGMs have the function of managing stress waves. Unlike traditional elastoplastic materials, the wave structures of FGMs will also change depending on such factors as the initial stress state, the amplitude of the loading, and the gradient distribution of the material.

Investigation of dynamic impact responses of layered polymer-graphene nanocomposite films using coarse-grained molecular dynamics simulations

Polymer nanocomposite films have recently shown superior energy dissipation capability by using the micro-projectile impact testing method. However, how stress waves interact with nanointerfaces and the underlying deformation mechanisms have remained largely elusive. This paper investigates the detailed stress wave propagation process and dynamic failure mechanisms of layered poly(methyl methacrylate) (PMMA)-graphene nanocomposite films during piston impact through coarse-grained molecular dynamics simulations. The spatiotemporal contours of stress and local density clearly demonstrate shock front, reflected wave, and release wave. By plotting shock front velocity (Us) against piston velocity (Up), we find that the linear Hugoniot Us−Up relationship generally observed for bulk polymer systems also applies to the layered nanocomposite system. When the piston reaches a critical velocity, PMMA crazing can emerge at the location where the major reflected wave and release wave meet. We show that the activation of PMMA crazing significantly enhances the energy dissipation ratio of the nanocomposite films, defined as the ratio between the dissipated energy through irreversible deformation and the input energy. The ratio maximizes at the critical Up when the PMMA crazing emerges and then decreases as Up further increases. We also find that a critical PMMA-graphene interfacial strength is required to activate PMMA crazing instead of interfacial separation. Additionally, layer thickness affects the amounts of input energy and dissipated energy for nanocomposite films under impact. This study provides important insights into the detailed dynamic deformation mechanisms and how nanointerfaces/nanostructures affect the energy dissipation capability of layered nanocomposite films.

The origin of high-velocity impact response and damage mechanisms for bioinspired composites

Natural materials such as nacre abalone shells are often leveraged for inspiration in developing high-performing materials for impact protection applications. However, a comprehensive understanding of the microstructure-property relationships and their corresponding damage mechanisms in bioinspired designs under high-speed impact has not yet been fully studied. In this paper, the mechanism of the high-speed impact performance of nacre-inspired microstructures is presented, considering a set of design parameters using high-throughput computational simulations. Results show that adding interfacial waviness to traditional nacre designs enlarges the damage area, and an inclined interface helps to effectively block the crack and stress wave propagation, leading to superior impact performance. Moreover, an asymmetric microstructure tends to rotate an impactor, causing it to travel a longer path yielding larger energy dissipation. It is envisioned that pinpointing the superior features embedded in nacre-like structures can provide unique design guidelines for next-generation impact-resistant materials. • Impact resistance of bioinspired composites studied using computational simulations • Toughening mechanisms presented by investigating crack and stress wave propagations • Microstructural design effects on impact performance under different velocities Lee et al. present the mechanism of high-speed impact performance of bioinspired microstructural designs using high-throughput computational simulations. Results show that adding interfacial features such as waviness and incline can enlarge the damage area and help to effectively block the crack and stress wave propagation, leading to superior impact performance.

Blast behaviour of precast segmental vs monolithic concrete beams prestressed with unbonded tendons: A numerical investigation

This study aims to numerically investigate the response of precast/prefabricated segmental concrete girders/beams (PSCBs) under detonations of high explosives. A new and effective method of applying prestressing force in tendons in LS-DYNA is explored and used. The working mechanisms of PSCBs vs conventional monolithic beams in resisting blast loads are comprehensively examined and discussed. The numerical results show that blast-induced damage to the beams is primarily caused by three different mechanisms, namely the propagations of blast-induced stress waves and plastic hinges, and the beam free-vibration deflection (global response). There are similar stress wave propagation and the resultant damage in the monolithic and segmental beams at the early stage when the joints are closed. The different damage patterns in these two beams are mainly due to the propagation of plastic hinges and the beam's free-vibration deflection. Damage is more severe and well distributed in the monolithic beam whereas damage to PSCB mainly concentrates in the segment next to the explosive and around the joints. The energy absorption mechanism provided by the relative movement between the segments is the main reason for the reduced damage in the PSCB. Although having larger displacement, the PSCB shows better blast resistance compared to the monolithic beam. Either increasing the prestressing reinforcement ratio or effective prestressing stress reduces the peak and residual displacement of the beam but increases concrete damage. Increasing the number of segments leads to a larger beam displacement response but reduces concrete damage. Energy dissipation (ED) bars are found to effectively unite the segments and hence result in the segmental beam having a similar blast behaviour as the monolithic counterpart.

Research on the Vibration and Wave Propagation in Ship-Borne Tethered UAV Using Stress Wave Method

To investigate the vibration behavior of ship-borne tethered UAVs under taut–slack conditions, the Hamilton principle is used to establish the three-dimensional dynamic equations of the ship-borne tethered UAVs while taking into account geometric nonlinearity and simplifying them into the corresponding stress wave equations. By employing the characteristic line technique to solve the stress wave equation of ship-borne tethered UAVs, it is possible to numerically determine the effects of various factors on the vibration behavior of these drones. Dimensional analysis is then used to build the experimental model, ensuring that the numerical outcomes are accurate. The findings show that the impact of equilibrium curvature connects longitudinal and transverse waves and that the geometric dispersion of stress wave propagation in the tethered cable is caused by equilibrium curvature. The standing wave takes the lead and causes subharmonic and frequency doubling components in the top tension response when the end excitation frequency is near the tethered UAVs’ natural frequency. Additionally, the cable’s center as well as its end will display the highest dynamic tension value.

Fast numerical estimation of residual stresses induced by laser shock peening

The aim of this paper is to develop a model allowing a fast first approximate estimation of the elastic–plastic stress wave propagation caused by a laser impact and the resulting residual stress field. We start by modeling the stress wave propagation, adopting a 1D uniaxial modeling, reducing the behavior of the specimen to the axis of the laser impact, excluding any edge effects caused by the edges of the laser spot. The plastic strain field resulting from this propagation can in turn be used to compute the residual stresses, by making use of an analytic modeling in the case of an infinite planar plate. The accuracy of the 1D model is assessed by comparing it to finite elements simulations, acting as a reference solution, for several materials and laser spot diameters. The results show that the stress wave propagation from the 1D model is close to identical to the reference solution. The residual plastic and stress fields from the finite elements model present a uniaxial distribution on a large portion of the laser spot, except for the very edge and spot center. The comparison between the 1D model and the reference solution shows a good match, indicating that the 1D model can be used for a fast approximation the mechanical fields created by a laser impact for laser spot diameters larger than 2 mm.

Stress wave propagation characteristics and impact resistance of laminated composites under impact loading

SHPB simulation of TC4/2024AL/TC4, TC4/TA2/TC4, and TC4/Al3Ti/TC4 laminated composites under different impact velocities of strike bar was carried out by ANSYS/LS-DYNA. Then stress distribution of the laminated composites under impact loading was theoretically analyzed according to the one-dimensional stress wave theory. Influencing factors of stress distribution and energy attenuation were emphatically analyzed, including impact velocities of the strike bar, wave impedance of interlayer, and plastic deformation. The results show that, when the impact velocity is determined, impact resistance is negatively correlated with the impedance of the interlayer. Under certain conditions, impact resistance is negatively correlated with impedance of interlayer, and positively correlated with impact velocity. In addition, the accumulation of plastic deformation could make residual stress distribution along the position coordinate axis shows a trend of gradual increase from both sides to the middle position.

Research on stress wave wood nondestructive testing technology

As a kind of nondestructive testing technology, stress wave technology has the advantages of long propagation distance, strong anti-interference ability and convenient use, and has become one of the important means to detect wood properties and defects at home and abroad. This paper introduces several stress wave wood testing equipment commonly used in the field of wood non-destructive testing at this stage, and analyzes its characteristics. The research status of stress wave wood nondestructive testing technology is analyzed from three aspects: mechanical property testing, internal defect testing and factors affecting stress wave propagation velocity. Finally, the existing problems and development trends of stress wave technology in wood nondestructive testing are discussed to provide reference for further research in this field.

Influence of Bandgap on the Response of Periodic Metaconcrete Rod Structure under Blast Load

A metamaterial is an engineered material made by embedding engineered cores (heavy cores coated with a soft coating) into a matrix, which generates bandgaps such that stress waves with frequencies falling into the bandgaps can be mitigated. Metaconcrete made by embedding engineered aggregates into a mortar matrix can be used to attenuate stress waves generated by blast loads. This study presents a method for determining the metaconcrete bandgaps and designing a metaconcrete unit cell by using commercially available software to achieve the desired bandgaps. The dispersion relation of metaconcrete unit cells was investigated. With the designed configuration, the performance of metaconcrete rod structures under blast load was studied by using a software simulation. The results demonstrated the effectiveness of the designed unit cell with the selected soft coating and heavy core in mitigating blast-induced elastic and nonlinear inelastic stress-wave propagation. The responses of metaconcrete rod structures with one type of unit cell and grouped two types of unit cells with multiple bandgaps subjected to blast load were also studied. The results show that the grouped unit cells with multiple bandgaps led to better performance in wave mitigation than only one type of unit cell in the example metaconcrete rod structure.

Impact-Induced Through-Thickness Stress Wave Propagation and Damage in Woven Composites

Impact-Induced Through-Thickness Stress Wave Propagation and Damage in Woven Composites