Shock Wave Propagation Research Articles

Singular travelling waves in soft viscoelastic solids of rate type

We consider shear wave propagation in soft viscoelastic solids of rate type. Based on objective stress rates, the constitutive model accounts for finite strain, incompressibility, as well as stress- and strain-rate viscoelasticity. The theory generalises the standard linear solid model to three-dimensional volume-preserving motions of large amplitude in a physically-consistent way. The nonlinear equations governing shear motion take the form of a one-dimensional hyperbolic system with relaxation. For specific objective rates of Cauchy stress (lower- and upper-convected derivatives), we study the propagation of acceleration waves and shock waves. Then we show that both smooth and discontinuous travelling wave solutions can be obtained analytically. We observe that the amplitude and velocity of steady shocks are very sensitive to variations of the stress relaxation time. Furthermore, the existence of steady shocks is conditional. Extension of these results to the case of multiple relaxation mechanisms and of the Jaumann stress rate is attempted. The analysis of simple shearing motions is more involved in these cases.

Liquids with High Compressibility.

Compressibility is a fundamental property of all materials. For fluids, that is, gases and liquids, compressibility forms the basis of technologies such as pneumatics and hydraulics and determines basic phenomena such as the propagation of sound and shock waves. In contrast to gases, liquids are almost incompressible. If the compressibility of liquids could be increased and controlled, new applications in hydraulics and shock absorption could result. Here, it is shown that dispersing hydrophobic porous particles into water gives aqueous suspensions with much greater compressibilities than any normal liquids such as water (specifically, up to 20 times greater over certain pressure ranges). The increased compressibility results from water molecules being forced into the hydrophobic pores of the particles under applied pressure. The degree of compression can be controlled by varying the amount of porous particles added. Also, the pressure range of compression can be reduced by adding methanol or increased by adding salt. In all cases, the liquids expand back to their original volume when the applied pressure is released. The approach shown here is simple and economical and could potentially be scaled up to give large amounts of highly compressible liquids.

Experimental and numerical investigation of the laser shock-based paint stripping process on CFRP substrates

Various laser shock wave applications have been proposed for metals; the most popular is the laser shock peening. In composites, the use of the laser shock wave technology is still at an early stage. Laser shock paint stripping (LSPS) is a method where a laser-induced shock wave is used to remove a paint from a substrate. In this study, a combined experimental–numerical study was performed on the LSPS on Carbon Fiber Reinforced Polymers (CFRP) substrates. Two types of specimens were investigated: specimens with an epoxy structural primer covered by a polyurethane base and a clear coat and specimens with the above layers plus an epoxy exterior primer between the epoxy structural primer and the polyurethane layer. The specimens were shot using various laser intensities aiming to obtain the stripping threshold and the stripping percentage as functions of the laser intensity. The diameter of the stripped area was measured by a profilometer. An electron microscope was used to evaluate the stripping efficiency. In parallel, a numerical model was developed using the LS-DYNA explicit Finite Element (FE) software. For the modeling of the CFRP, a progressive damage model with strain rate parameters was used while for the epoxy an elastic–plastic-hydrodynamic material model combined with the Gruneisen equation of state. The interface between these two materials was modeled using cohesive zone elements of zero thickness, which follow a bi-linear traction-separation law. Calibration of the modeling of the shock wave propagation inside the composite material was achieved through the comparison of the back-face velocity profiles, measured by a velocity interferometer system for any reflector system. The results from the multiple tests conducted revealed the repeatability of the process and the significant effect of the laser intensity. On the other hand, the model managed to predict well the back face velocity–time profile but in most cases, it failed to predict the stripping pattern. This is mainly due to lack of crucial material properties and the assumptions made in the modeling of the applied pressure profile.

Temperature and pressure propagation characteristics in multi-media interfaces of PVDF pressure sensor near underwater explosion source

In this paper, based on the self-made PVDF pressure sensor, the underwater explosion test of the emulsion explosive was performed to verify the measurement accuracy of the self-made PVDF pressure sensor and the feasibility of the pressure measurement near the explosive source. Then the single column emulsion explosive and gram-grade Al/PTFE underwater explosion experiment and numerical simulation were carried out, and the error between the experimental and numerical simulation results is small (The difference between the pressure peaks obtained from the emulsion explosive experiment and numerical simulation is about 25.07 MPa and the pressure decay trend is close; the peak difference in lane 1 obtained by Al/PTFE experiment and simulation is about 23 MPa, the second peak difference is about 0.8 MPa, the pressure decay trend after the second peak is close, and the shock wave arrival moment in experiment lags the numerical simulation by about 30μs), which verifies the reliability of the simulation model. Meanwhile, the numerical simulation of explosion at a depth of 10m below sea level was performed, the evolutionary law of the sensor and water pressure at 1–10 times the charge diameter is expounded, the variable rule of temperature during sensor response period is analyzed. The numerical simulation results show that the time-history curve of pressure includes two stages: bubble microjet and shock wave propagation, which the bubble microjet pressure can reach 10 GPa, and the sensor structure and shock wave pressure test will not be affected within the response period. The time history curves of shock wave pressure in experiments are basically the same by comparing with the simulation results of underwater pressure at the same position, and impact temperature rise will affect the measurement accuracy of PVDF film, but the lasting time of heat conduction in the PVDF sensor is longer than the response period of impact pressure, therefore the influence of heat conduction on the test accuracy can be ignored.

The effect of ablation crater on geomaterials caused by laser shot accumulation on the laser-induced plasma and shock wave

The stability of laser-induced breakdown spectroscopy (LIBS) signal is vital for its application in geomaterials, which is challenged by spectral fluctuations caused by variable ablation craters. To investigate the influence of the ablation crater caused by laser shot accumulation, the shot-to-shot variation of plasma was analyzed from the aspects of shock wave propagation, ablation crater morphology, plasma morphology, and spectral evolution, which was conducted based on a fiber-optic LIBS (FO-LIBS) system. A pressure sensor was applied to monitor the shock wave signal due to the shock wave propagation characteristics related to the number of shots and types of binding materials. The evolution of the ablation crater profile and depth was tracked, and a linear correlation model between crater depth and shock wave energy was established. It was found that the spectral intensity increases first rapidly and gradually decreases, which can be attributed to the competition between the enhancement of spatial confinement and the plasma cooling phase. Strong self-reversal was observed due to the laser pulse accumulation, with an increase in the plasma expanding distance. This study illustrates the interaction of laser pulses, ablation, and plasma from different aspects, and provides a simple method to track the ablation process.

Attenuation characteristics of shock waves in drilling and blasting based on viscoelastic wave theory

This study investigates the propagation and attenuation characteristics of shock waves produced by drilling and blasting. The focus is on a novel method for calculating the attenuation of the shock wave pressure. Based on the propagation of shock waves in a rod with a variable section and a Maxwell model for rock, theoretical solutions for the attenuation of the blast-induced shock wave pressure were derived and the main factors influencing the attenuation speed were analyzed. The attenuation law of shock waves for siltstone, limestone, and granite, with common borehole diameters of 76–150 mm and initial shock pressures of 1–6 GPa, was analyzed through numerical simulations. The results show that the shock wave falls off as the square root of the relative distance. The attenuation speed of the shock wave is mainly related to the borehole size, rock properties, and shock wave intensity. The attenuation speed increases with increasing initial shock pressure on the borehole wall, but decreases with increasing borehole radius. Compared with soft rock, the shock wave pressure attenuates faster in hard rock. Combining theoretical analysis and numerical simulations, an exponential attenuation coefficient was introduced to the attenuation formula. Statistical analysis shows that the exponential attenuation coefficient is linearly proportional to the initial shock pressure. Furthermore, a new method for calculating the attenuation of shock wave pressure was proposed, reflecting the comprehensive influence of rock characteristics and shock wave intensity. The new method is an improvement over existing methods, which only consider the effect of rock properties on shock wave attenuation. The reliability of the new method was verified against the results of field tests. The findings provide a theoretical basis for the optimization of blasting parameters and assessments of blast-resistance for structures.

Numerical simulation study on pile expansion by shock waves of electrical wire explosion in liquids

Compaction of the soil around the borehole filled with cement paste can build shaped pile foundations, effectively enhancing the bearing capacity of the pile foundations. Shock waves of electrical wire explosion in liquids can compact the soil and build expanded pile foundations, which has broad industrial application prospects. Electrical wire explosion in liquids has the advantages of high efficiency, good repeatability and controllability. In order to analyze the mechanism of pile expansion by electrical wire explosion in liquids, in this paper, a comprehensive test platform for pile expansion by electrical wire explosion was established, the voltage and current of the discharge channel were measured. The expanded piles were built through multiple discharges, and the size and bearing capacity of the piles were measured. Based on the finite element numerical method, a three-dimensional model of soil compaction by shock waves was established, and the material parameters, model dimensions were reasonably determined. The propagation and attenuation processes of shock waves in cement paste and soil were simulated, and the soil compaction process was obtained. The cumulative effect of pile expansion under multiple shock wave actions was analyzed and compared with test results.

Direct imaging of shock wave splitting in diamond at Mbar pressure

Understanding the behavior of matter at extreme pressures of the order of a megabar (Mbar) is essential to gain insight into various physical phenomena at macroscales—the formation of planets, young stars, and the cores of super-Earths, and at microscales—damage to ceramic materials and high-pressure plastic transformation and phase transitions in solids. Under dynamic compression of solids up to Mbar pressures, even a solid with high strength exhibits plastic properties, causing the induced shock wave to split in two: an elastic precursor and a plastic shock wave. This phenomenon is described by theoretical models based on indirect measurements of material response. The advent of x-ray free-electron lasers (XFELs) has made it possible to use their ultrashort pulses for direct observations of the propagation of shock waves in solid materials by the method of phase-contrast radiography. However, there is still a lack of comprehensive data for verification of theoretical models of different solids. Here, we present the results of an experiment in which the evolution of the coupled elastic–plastic wave structure in diamond was directly observed and studied with submicrometer spatial resolution, using the unique capabilities of the x-ray free-electron laser (XFEL). The direct measurements allowed, for the first time, the fitting and validation of the 2D failure model for diamond in the range of several Mbar. Our experimental approach opens new possibilities for the direct verification and construction of equations of state of matter in the ultra-high-stress range, which are relevant to solving a variety of problems in high-energy-density physics.

Attenuation effect of a preset bubble on hydrodynamic ram induced by fragments impacting fluid-filled tank

When the fluid-filled structure is impacted by a high-velocity penetrator, the hydrodynamic ram (HRAM) will appear and may induce catastrophic damage. Based on the damage mechanism of HRAM, a countermeasure through presetting a bubble inside the fluid-filled tank is proposed to attenuate the HRAM loads and thus alleviate the vulnerability of the tank structure under the impact of high-velocity projectile. Experimental tests are performed to compare the tank’s damage considering the effect of bubble by the charge-driven preset fragments. The experimental results show that the peak pressure and impulse of the initial impact wave acting on the tank rear plate are reduced by 78% and 88%, respectively, and the cavitation collapsing pressure acting on the rear plate almost disappeared. Meanwhile, the maximum deformation of the front plate is reduced by about 15%. In addition, numerical simulation is employed to reproduce the experimental process. By comparing the structural dynamic response and the shock wave propagation process, the attenuation mechanism of the preset bubble on HRAM is revealed. Furthermore, the influence of the bubble position and size on the attenuation effect is investigated. Numerical results show that a smaller distance between the bubble and the front plate, and a larger bubble size lead to a better attenuation effect.

Influence of overdriven detonation on the energy release of aluminized explosives in underwater explosion

An underwater explosion experiment was designed for the cyclotrimethylenetrinitramine-based aluminized explosives to study the influence of detonation conditions on the explosion performance and the afterburn reaction of aluminum (Al) particles. The research results showed that the performance of shock wave and bubble pulsation grew stronger under the influence of overdriven detonation (ODD), and the contribution of ODD to the bubble energy was associated with the proportion of the inner core and the outer coat. Considering the propagation characteristics of the detonation wave in the ordinary charge and the inner/outer charge, the attenuation of ODD and its role in the initial pressure of the bubble were investigated, and this relationship was used to establish a numerical model for the bubble dynamic behaviors of aluminized explosives. According to the experimental results, the correctness of the established model for the bubble dynamics under ODD was verified, and the variation laws of the afterburn reaction during the bubble pulsation were investigated. It was found that the initial pressure of the bubble under ODD was higher than that under steady detonation. The improvement on the initial pressure promoted the afterburn reaction during the accelerating expansion and enhanced the bubble expansion capacity to support the formation and propagation of shock waves. In the subsequent bubble pulsation, the duration of the decelerating expansion was significantly longer than that of the accelerating expansion, and the ODD had little effect on the afterburn reaction in this stage.

Shock-induced melting and crystallization in titanium irradiated by ultrashort laser pulse

Modification of titanium microstructure after propagation of a melting shock wave (SW) generated by a femtosecond laser pulse is investigated experimentally and analyzed using hydrodynamic and atomistic simulations. Scanning and transmission electron microscopy with analysis of microdiffraction is used to determine the microstructure of modified subsurface layers of titanium. We found that two layers are modified beneath the surface. A top surface polycrystalline layer of nanoscale grains is formed from shock-molten material via rapid crystallization. In a deeper subsurface layer, where the shock-induced melting changes into plastic deformation due to attenuation of SW, the grain structure of solid is considerably affected, which results in a grain size distribution differing from that in the intact titanium. Molecular dynamics simulation of single-crystal titanium reveals that the SW front continues to melt even after its temperature drops below the melting curve Tm(P). The enormous shear stress of ∼12 GPa generated in a narrow SW front leads to free slip of atomic planes, collapse of the crystal lattice, and formation of a supercooled metastable melt. Such melt crystallizes in an unloading tail of SW. The mechanical melting ceases after drop in the shear stress giving rise to the shock-induced plastic deformation. The last process triggers a long-term rearrangement of atomic structures in solid. The overall depth of modified layers is limited by SW attenuation to the Hugoniot elastic limit and can reach several micrometers. The obtained results reveal the basic physical mechanisms of surface hardening of metals by ultrashort laser pulses.

Unraveling Anisotropy in Crystalline Orientation under Shock-Induced Dynamic Responses in High-Entropy Alloy Co25Ni25Fe25Al7.5Cu17.5.

Shock-induced plastic deformation and spall damage in the single-crystalline FCC Co25Ni25Fe25Al7.5Cu17.5 high-entropy alloy (HEA) under varying shock intensities were systematically investigated using large-scale molecular dynamics simulations. The study reveals the significant influence of crystalline orientation on the deformation mechanism and spall damage. Specifically, the shock wave velocities in the [110] and [111] directions are significantly higher than that in the [001] direction, resulting in a two-zone elastic-plastic shock wave structure observed in the [110] and [111] samples, while only a single-wave structure is found in the [001] sample. The plastic deformation is dominated by the FCC to BCC transformation following the Bain path and a small amount of stacking faults during the compression stage in the [001] sample, whereas it depends on the stacking faults induced by Shockley dislocation motion in the [110] and [111] samples. The stacking faults and phase transformation in the [001] sample exhibit high reversibility under release effects, while extensive dislocations are present in the [110] and [111] samples after release. Interestingly, tension-strain-induced FCC to BCC phase transformation is observed in the [001] sample during the release stage, resulting in increased spall strength compared to the [110] and [111] samples. The spall strength estimated from both bulk and free surface velocity history shows reasonable consistency. Additionally, the spall strength remains stable with increasing shock intensities. The study discusses in detail the shock wave propagation, microstructure change, and spall damage evolution. Overall, our comprehensive studies provide deep insights into the deformation and fracture mechanisms of Co25Ni25Fe25Al7.5Cu17.5 HEA under shock loading, contributing to a better understanding of dynamic deformation under extreme environments.

Environmental Sustainability and Efficiency of Offshore Platform Decommissioning: A Review

Malaysia has inherited many aged offshore platforms that have reached their decommissioning deadline. Many platforms need to be detached through subsea processes. Although there are good techniques for this, they are usually costly and necessitate a great deal of post-cut checking to ensure complete detachment. Explosive cutting techniques, on the other hand, are cost-effective and reliable for offshore decommissioning as they ensure complete cutting with little uncertainty. Until 2019, statistics showed that almost 35% of offshore platform decommissioning processes involved the use of explosive materials and other mechanical severance options. The method was reliable and cheap, but it had a large environmental impact. During blasting procedures utilizing pressure waves, many sea animal species are threatened, such as fishes, turtles, and dolphins. Depletion of already scarce fish stocks through the unsustainable use of explosive removal should be prevented by reducing the environmental impact of underwater explosives. Moreover, due to safety hazards, vessel and aircraft movement around the explosion zone is prohibited. Therefore, this paper provides a comprehensive review of using a highly vacuum-sealed pile for the explosion to control and reduce shock wave propagation. This effort appreciates the benefits of the explosive cutting technique and reduces its environmental side effects. Our findings indicate an accurate and clean-cut method serving the efficiency of offshore platform decommissioning as well as environmental sustainability. Finally, recommendations for future perspectives have been provided based on the decommissioning of offshore platforms, such as topside removal, planning, time scale, and optimization of available space.

Evolution of underwater shock wave in far-field regime of electrical wire explosion system over wide range of electric pulse energy

The parametric relationships between underwater shock waves (SWs) in far-field regime and electrically exploded wire under different charging voltages of a generator are investigated. Contributions of the vaporization and current restrike to the resulting SWs have been examined by means of electro-physical diagnostics, free-field pressure probe, and high-speed photography. In the experiment, a 6-μF pulse capacitor is adopted to provide a microsecond timescale pulsed current, exploding a 90/185-μm-diameter, 2-cm-long copper wire with the charging voltage ranging from 7.1 kV (stored energy ∼ 150 J) to 18.3 kV (∼1000 J). Experimental results indicate that as the increase of the charging voltage, the relationship between electro-physical and shock wave parameters shows a rather complex situation. When the charging voltage ranging from 7.1 kV (∼150 J) to 11.6 kV (∼400 J), the peak pressure of SWs (300 mm away from the explosion source) increases almost linearly from 1.16 ± 0.03 to 2.24 ± 0.05 MPa (90-μm wire), and 1.67 ± 0.17 to 2.87 ± 0.12 MPa (185-μm wire). Nevertheless, at a higher charging voltage between 11.6 kV (400 J) to 14.1 kV (600 J), the peak pressure stabilizes in a strange “plateau”. Until the residual energy after the explosion is sufficiently large (>600 J in this study) to induce a strong current restrike, the development of the plasma channel could further enhance the expansion of explosion products, as well as the intensity of measured SWs. In addition, high-speed photography has been applied for those explosions, providing the information of plasma channel expansion and initial SWs propagation.

Review of shock wave pressure reconstruction methods in explosion field

Explosion shock wave pressure is one of the main damage parameters produced in the process of ammunition explosion, and it is also an important technical index to evaluate the damage power of ammunition. However, in the actual testing process, only a limited amount of shockwave pressure data at specific measuring points can be obtained, which cannot accurately reflect the distribution laws of the shockwave pressure propagation after the ammunition explosion. Therefore, it is particularly important to conduct reconstruction of the shockwave pressure field distribution laws based on limited measuring point data. This paper reviews the research work and related achievements obtained by researchers at home and abroad on the reconstruction of shockwave pressure distribution laws in explosion fields. The paper also elucidates the relevant application of computer tomography imaging techniques, shockwave propagation attenuation model reconstruction, and various interpolation algorithms in the reconstruction process of the shockwave pressure field. Given the current research situation both domestically and internationally, we have pinpointed the major issues that still exist in the current stage of research and proposed the key areas of focus that need attention in future research.

Selection of Material and Thickness of the Protective Wall in the Conditions of a Hydrogen Explosion of Various Power

The main purpose of this study is a numerical assessment of the consequences of an explosion of a hydrogen-air cloud on the personnel of a hydrogen fueling station and the strength of a protective solid wall of certain dimensions. An explosive gas mixture is formed as a result of the destruction of high-pressure cylinders, the number of which determines the size of the cloud, the power of the explosion, and the scale of the consequences of environmental impact. To obtain the spatio-temporal distribution of the maximum overpressure and the impulse of the shock wave compression phase, a mathematical model of the dispersion of an active gaseous admixture is used, taking into account the chemical interaction with air oxygen. The probable consequences of the shock-impulse impact on the personnel at the control point are carried out using probit analysis. The values of the maximum bending moment and stress at the base of the protective wall, which result from the impact of the blast wave, are used to deterministically estimate the minimum wall thickness necessary for the safe operation of the protective device. The mathematical model takes into account the complex terrain and the three-dimensional non-stationary nature of the shock wave propagation process, and it is a source of data necessary to solve the problem of the strength of solid objects located in the area of baric perturbation of the gaseous medium. The developed methodology makes it possible to carry out a comparative analysis of the effectiveness of protective structures in relation to the power of the explosion.

A study of explosive-induced fracture in polymethyl methacrylate (PMMA)

The fracture response of geologic materials is of interest for applications, including geothermal energy harnessing and containment of underground explosions. To better understand the explosively induced fracture response of geomaterials, polymethyl methacrylate (PMMA) was used as a transparent rock surrogate to allow imaging of internal shock propagation and fracture growth processes. Experiments were conducted using high-speed shadowgraphy and photon Doppler velocimetry (PDV), which were compared to numerical simulations. Experiments measured fractures produced in 304.8mm×304.8mm×304.8mm PMMA cubes with two simultaneously initiated detonators. The cubes were subjected to varying amounts and directions of externally applied uniaxial stresses, including no stress, 2 MPa stress, and 20 MPa stress. The fracture radius as a function of time was extracted from the high-speed videos. Post-test images of the PMMA cubes aided in the determination of three-dimensional effects not directly imaged by the cameras. The surface velocity history and the shock response captured in PDV and the high-speed videos were compared to the simulated explosive-induced shock response. The simulation results indicate that the shock drives the fracture for the first 20 μs corresponding to a fracture radius of approximately 15 mm in the experiments. The gas-driven fracture extent was estimated analytically using an equilibrium stress distribution calculated after the shock wave propagation through the sample. Reduction in the gas pressure due to the leakage of the explosive products through the crack as a function of time was accounted for. The estimated fracture lengths were in agreement with the experimentally observed fracture lengths.

The Shock-Induced Deformation and Spallation Failure of Bicrystal Copper with a Nanoscale Helium Bubble via Molecular Dynamics Simulations.

Both the nanoscale helium (He) bubble and grain boundaries (GBs) play important roles in the dynamic mechanical behavior of irradiated nanocrystalline materials. Using molecular dynamics simulations, we study the shock-induced deformation and spallation failure of bicrystal copper with a nanoscale He bubble. Two extreme loading directions (perpendicular or parallel to the GB plane) and various impact velocities (0.5-2.5 km/s) are considered. Our results reveal that the He bubble shows hindrance to the propagation of shock waves at lower impact velocities but will accelerate shock wave propagation at higher impact velocities due to the local compression wave generated by the collapse of the He bubble. The parallel loading direction is found to have a greater effect on He bubble deformation during shock compression. The He bubble will slightly reduce the spall strength of the material at lower impact velocities but has a limited effect on the spallation process, which is dominated by the evolution of the GB. At lower impact velocities, the mechanism of spall damage is dominated by the cleavage fracture along the GB plane for the perpendicular loading condition but dominated by the He bubble expansion and void growth for the parallel loading condition. At higher impact velocities, micro-spallation occurs for both loading conditions, and the effects of GBs and He bubbles can be ignored.

Analysis of the influence of corrugated steel thickness on the damage characteristics and explosion resistance of corrugated steel-concrete composite structure

A three-dimensional refined numerical simulation model of corrugated steel-concrete slab composite structure under contact explosion load was established by using FEM-SPH coupling method to explore the anti-explosion performance of corrugated steel reinforced concrete slabs with different thicknesses. The influence of corrugated steel thickness on the dynamic damage evolution characteristics, anti-explosion performance and shock wave propagation mechanism of composite structure was investigated. The results show that the maximum error between the simulation results and the experimental results of the crater diameter of the concrete slab and the mid-span displacement of the corrugated steel in the corrugated steel-concrete slab composite structure is 1.6 % and 2.3 %, respectively, which verifies the effectiveness of the simulation method. The mid-span displacement, peak stress and acceleration at the center point of corrugated steel in corrugated steel-concrete composite structure decrease with the increase of corrugated steel thickness, while the energy absorption value increases with the increase of corrugated steel thickness. The mid-span displacement of 12 mm thick corrugated steel is 83.4 % lower than that of 3 mm thick corrugated steel. The failure mode of the composite structure under the same explosive equivalent is mainly manifested as the crater and penetration failure of the concrete slab, and the damage range gradually decreases with the increase of the thickness of the corrugated steel. The failure volume of concrete slab in the composite structure decreases with the increase of corrugated steel thickness, while the energy absorption value of the composite structure increases with the increase of corrugated steel thickness. The research results can provide a theoretical basis for the application of corrugated steel-concrete slab composite structure in the field of structural anti-explosion protection.

Survey of the quality and origins of websites on penile low-intensity shockwave therapy in Canada.

The aim of this study was to establish the quality of patient-facing websites advertising low-intensity shockwave therapy (LISWT) for erectile dysfunction (ED) and Peyronie's disease (PD) patients in Canada. Canadian websites offering LIWST for ED or PD were identified using online web searches. The characteristics of these websites were reviewed, along with examining the presence of HONCode certification, assigning a brief DISCERN score (a tool designed to evaluate health information online) and readability scores. We also examined the LIWST technology advertised, as well as benefits of LIWST cited by the websites. Twenty-five unique websites linked to 46 clinics were identified and reviewed. Twenty-four percent of websites were run by a urologist. Other specialties offering LISWT included general practitioners, anesthesiologists, naturopaths, nurse practitioners, physiotherapists, and registered massage therapists. Twenty-four percent of the websites advertised the use of a focused shockwave generator. Forty percent of the websites had peer-reviewed references. The average brief DISCERN score was 14 (standard deviation 3.4). There was no association between the physician-or non-physician-led websites and the use of peer-reviewed references, readability scores, the number of clinic locations, or higher brief discern scores. LISWT is readily advertised online for ED and PD patients in Canada; however, only a minority use a focused shockwave generator. There is a wide diversity of practitioners offering LISWT. Websites offering LISWT are generally of poor quality and do not provide adequate information for patients to make educated treatment decisions.