Shock Wave Pressure Research Articles

ПРИБЛИЖЕННАЯ ОЦЕНКА ПОЛЕЙ ДАВЛЕНИЯ В ЖИДКОСТИ С ГАЗОВЫМИ ПОЛОСТЯМИ

The issues of protection of underwater objects using cylindrical air cavities are studied. In a number of tasks, it is fundamentally important to have not only the distribution of the pressure field in the liquid because of the movement of the boundaries of the deformable system, but also the parameters of the movement of the liquid itself. In this case, the parameters of the liquid movement have a significant effect on the fastening conditions of the gas cavities. The shock wave, spreading in water with gas inclusions, undergoes significant deformation. Preliminary experiments conducted to determine the parameters of underwater shock wave in water with air cavities have shown the possibility of controlling pressure peaks and, therefore, creating conditions for the safety of the underwater structure. Analyzing theoretical studies, it can be seen, that a dispersion of the wave process occurs inside the liquid region with gas cavities. The initial pressure peak decreases dramatically. In the area of the protected object, it decreases by almost two orders of magnitude compared to the maximum pressure in the initial shock wave. The pressure is mainly determined by the pulsation of the gas cavities generated by the explosive air wave. The duration of the load in the presence of gas cavities increases sharply.

Research on the Safety Response Characteristics of Composite Charges Under Shock Wave Loading

AbstractIn this work, reaction intensity diagnostic techniques such as self‐shorting electrical probes and witness plates were used to establish a new large‐scale gap test device, which can be used to effectively study the influence of shock wave pressure, confinement strength, and insensitive explosive layer thickness on the safety response under shock loading. Taking a composite charge consisting of a TATB‐based and an HMX‐based aluminized explosive as an example, the influence of shock wave pressure, shell confinement, and composite charge structure on the reaction intensity was studied in detail. The results show that the reaction intensity of the charge is positively correlated with the shock wave pressure, increases with the shell confinement strength, and decreases with the insensitive explosive layer thickness. For the same composite charge structure and confinement strength, the reaction intensity level of the charge increases with the shock pressure. When PBX‐5 is 40 mm thick and PBX‐6 is 60 mm thick, under initial pressures of 6.45, 3.61, and 1.51 GPa, the reaction levels are detonation, deflagration, and no reaction, respectively. Under the same shock pressure, the reaction intensity increases with the confinement strength and decreases with the insensitive explosive layer thickness. For the same composite charge structure and shock pressure (5 mm PBX‐5, 95 mm PBX‐6; 1.51 GPa shock pressure value), when the sleeve is 5 mm steel, 5 mm aluminum, 2 mm steel or weaker, the reaction levels are detonation, detonation, and no reaction, respectively. These results are helpful to the safety design of composite charges.

Effect of supercavity and shell casing on underwater energy release characteristics of armor-piercing-explosion supercavitating projectile charge

Abstract The Armor-Piercing Explosive Supercavitating Projectile (APESP) integrates explosion and armor-piercing effects, introducing a novel approach to underwater munitions. The energy release characteristic of the APESP charge underwater may differ from traditional underwater explosions due to the presence of the supercavity and shell casing. In order to investigate the effects of the supercavity and shell casing on this energy release characteristics, a finite element model of APESP charge underwater explosions is established. The deformation of the target is examined to evaluate the effects of the supercavity and shell casing. The mechanisms of these factors are further analysed theoretically. The results indicate that plastic deformation under the explosion of the APESP charge is primarily completed during the shock wave phase. Both the supercavity and shell casing influence the final deformation of the target by affecting the shock wave intensity, and the supercavity having a more significant impact. The pressure of the initial shock wave transmitted to the external medium of the charge is the highest when the charge is encased by a shell casing, and is the lowest when the charge is inside a supercavity. As the shock wave transmits through interfaces, it is amplified at the air-water interface and attenuated at both the shell-water and shell-air interfaces, with the greatest attenuation at the shell-air interface. Additionally, the presence of the shell casing reduces shock wave intensity but extends the duration of its action, thereby increasing the shock wave impulse.

Theoretical Study on Impact Compression Behavior and Reaction Characteristics of Reactive Materials

Abstract Reactive Materials (RMs) is usually inert at normal temperature and pressure, but when it is subjected to enough impact energy, it can be rapidly transformed into a high-temperature and high-pressure environment, which triggers a chemical reaction and releases a large amount of energy. In order to study the impact compression behavior and reaction characteristics of RMs, this paper established a typical Al/PTFE RMs impact reactivity calculation equation based on the Arrhenius reaction rate model and combined with Avrami-Erofeev’s n-dimensional nuclear/growth control reaction model. And theoretical calculations were conducted on the impact response and reaction characteristics of typical Al/PTFE RMs. The reliability of the model was verified by comparing the calculated results with the simulation results. At the same time, the propagation process of shock wave pressure peak under explosive load in RMs was numerically simulated using software, and the propagation law was studied. The results showed that the impact pressure had a significant impact on the energy release characteristics of typical Al/PTFE active materials. The calculation results of the critical reaction threshold for impact are in good agreement with the simulation results, indicating the reliability of the model. The size of the explosive charge remained unchanged, and as the propagation distance of the shock wave increases, the peak pressure of the shock wave attenuated slowly in the Al/PTFE RMs. During the explosive loading process, the Al/PTFE RMs did not undergo complete chemical reactions, and only a portion of the RMs underwent chemical reactions.

Influence of lining thickness and impedance on the explosion driving of prefabricated fragments

Abstract Prefabricated fragments may deform or crack during explosion driving process, which is adverse to kinetic energy damage. Setting up lining between explosive charges and prefabricated fragments is considered to be an effective way to prevent the excessive load on fragments. This paper studied the influence of lining thickness and impedance on explosion driving of prefabricated fragments based on LS-DYNA finite element simulation. Steel lining of different thickness between 0∼14mm have been studied, as well as steel liner with Kevlar fiber. Fragments accelerated drive process were analysed from the perspective of energy conversion. The results show that the initial speed of the fragment is mainly affected by the quality of the lining and the fracture radius. The axial deformation of the fragment is positively correlated with the initial impact pressure. Steel-fiber composite lining can reduce the shock wave pressure transmitted though, which significantly reducing the initial pressure on the fragments. Low-impedance Kevlar fiber on the outside of the 4340 steel lining can reduce the initial impact pressure of the fragment by about 75%.

Measurement of plasma characteristic parameters of copper foil explosion using interferometry

The accurate testing of plasma temperature and electron density and shock wave pressure during an electroburst in a copper foil transducer is critical for the characterization of the detonation performance of its elements. In this paper, the sequence of interferograms during the detonation of a copper foil transducer is captured at a frame rate of 3×106fps in conjunction with Mach–Zehnder interferometry and high-speed photography, and the results clearly demonstrate the propagation of the shock wave wavefront and plasma. The phase differences disturbed by plasma are extracted using the Fourier transform method, and the refractive index distributions are reconstructed with the Abel algorithm. Subsequently, based on the refractive index models of the shock wave and plasma, the shock wave pressure and plasma temperature and electron density are partitioned and reconstructed. Results show that the maximum shock wave pressure in the detonation of the copper foil transducer element is 1.297 atm, the maximum plasma temperature is 16,280 K, and the maximum plasma electron density is 2.134×1017cm−3. This study provides a theoretical and technical foundation for the detonation performance testing of pyrotechnic energy-conversion components.

Evaluation of the performance and effect of steel fiber reinforced cellular concrete for underwater blast protection under contact explosion loading

The reinforced concrete structure is more likely to be destroyed under the action of underwater explosion load, which makes the overall structure have the risk of instability. The purpose of this paper is to study the underwater anti-explosion protection performance of steel fiber reinforced cellular concrete protective layer. The FEM-SPH coupling method was used to study the underwater damage process, dynamic response, failure mode and protection effect of the protected structure strengthened by eight different proportions of protective layers. The results show that the addition of steel fiber reinforced cellular concrete protective layer can effectively improve the anti-explosion performance of the protected structure, and its anti-explosion performance is directly related to the volume fraction of steel fiber in the protective layer. Under different ratio protection schemes, the total energy absorption and protection rate of the protective layer increase first and then decrease with the increase of the volume fraction of steel fiber in the protective layer, while the peak pressure of the protected structure at the measuring point and the failure volume rate of the whole structure decrease first and then increase. Among them, the underwater wave attenuation and energy consumption effect of SAP10S15 protective layer is the most prominent, and its total energy absorption is 20 % higher than that of other protective layers. Under this ratio protection scheme, the shock wave pressure of the protected structure is greatly attenuated, and the peak pressure of each measuring point is reduced by about 35.8 %, 37.9 %, 23.7 %, 27.9 % and 35.1 % respectively compared with the unprotected scheme. The damage degree of the protected structure under the SAP10S15 ratio protection scheme is significantly reduced. The failure volume rate and damage index are 8.03 % and 0.21, respectively, which are 37.7 % and 42.5 % lower than those of the unprotected scheme. The damage level is reduced from serious damage to moderate damage. In addition, the damage grade prediction curve of the protected structure is constructed, and the predicted value of the curve is in good agreement with the simulation results, which can provide a reference for the rapid evaluation of the underwater explosion-proof performance of the steel fiber reinforced cellular concrete protective layer.

Numerical study of the spontaneous ignition mechanisms of pressurized hydrogen released inside pipes with different structures

Hydrogen is considered a key clean energy carrier to achieve the global goal of carbon neutrality. But spontaneous ignition can occur when pressurized hydrogen is released into pipes, and the presence of different pipe structures will significantly affect the ignition mechanism. In this work, the effects of varied pipe structures on the shock wave propagation and spontaneous ignition characteristics are investigated by numerical simulation with the DNS-like approach, EDC combustion model, and 21-step detailed hydrogen combustion mechanism. Results show that the simulation is in well agreement with the experimental data. Five dominant spontaneous ignition mechanisms are provided depending on different pipe structures. Among all types of pipe structures investigated, contraction structures can lead to a greater increase in shock wave pressure due to more severe shock wave reflection and convergence. While enlargement structures can contribute to more mixing of hydrogen and air, causing more sufficient combustion. This study provides a comprehensive understanding and clear safety guidance to inform the practical application of hydrogen energy.

Numerical investigation of dual‐source gas explosion dynamics in h‐type tunnels under varied enclosed situations

AbstractTo further investigate the propagation characteristics of shock waves and flame waves in H‐type tunnel gas explosions, numerical simulation studies were conducted on a dual‐source gas explosion model using Fluent software. Three distinct operational conditions were designed and modeled, leading to the following outcomes. The shock wave flow field parameters from dual sources (with equal source energy) are symmetrically distributed in the H‐type tunnel, with high pressure and low flow velocity in the connecting roadway between the two shock waves. Under different conditions, the pressure is generally higher in closed tunnels (fully closed greater than semi‐closed) and lower in open tunnels. The largest overpressure in non‐explosion areas occurs at the closed ends and in the connecting roadway, while the areas bearing the greatest impulse are the shock wave reflection zones and pressure coupling regions. In closed conditions, the flame wave first moves forward and then propagates backward after the explosion, influenced by reflected waves and pressure differences between the ends and the tunnel. In open conditions, the pressure in the flame zone is lower than at both ends, inhibiting the forward propagation of the flame wave.

Investigation on the Effect of Energy Release Rate of Aluminized Explosive on the Damage of Underwater Targets

AbstractAs a type of high‐energy explosive, aluminized explosives are extensively used in underwater weapons and ammunition. This study aims to investigate the energy release rate on the damage of underwater targets caused by aluminized explosives (RDX/Al). The ship was selected as a target, and numerical simulations were conducted using AUTODYN software to study the energy release rate corresponding to different particle sizes of aluminum powder (25 nm −300 μm) in the underwater explosion process of RDX/Al, as well as its destructive effect on targets in the water. The research quantitatively evaluates the whole ship′s destruction results, including longitudinal bending deformations and crevasse. In addition, typical cabins were selected in this study to assess the local damage effects by analyzing stress, shock wave pressure, displacement, and acceleration shock response. Based on the damage results, it was revealed that RDX/Al with aluminum powder particle sizes ranging from 54 nm to 145 nm exhibited the most optimal damaging effects on ships after underwater explosions. These findings provide a basis for improving the destructive power of aluminized explosives against underwater targets, simultaneously, they can be utilized by ship designers to guide research and development of improved protective measures, aiming to reduce the vulnerability of ships to explosive attacks.

The spatio-temporal evolution of shock wave pressure induced by laser: Effects of laser parameters and confinement layer

The spatio-temporal distribution of the shock wave pressure on the surface of the target is the key to the performance of laser shock processing (LSP), which is mainly determined by the laser parameters and the confinement layer. The two-dimensional kinetic simulations of the expansion process of the shock wave induced by irradiation of an aluminum target with nanosecond laser pulses are performed. It is found that by controlling the gap between the rigid confinement layer and the aluminum target, and the interval time between the double pulse laser pulses, multiple peaks appear on the shock wave pressure-time curve of the aluminum target surface, and the value and interval time of each peak will change.

Analysis of the Impact of Multiple Explosion Source Layouts on the Kinetic Characteristics of Gas Explosions in Blind Roadways

To investigate the changes in conditions within a blind roadway when multiple gas explosion sources are simultaneously detonated, the fluid dynamics software Fluent14.0 was used to conduct numerical simulation experiments with different numbers (2 and 3) and varying intervals (5 m, 10 m, and 15 m) of explosion sources. The results revealed that multiple explosion sources in gas explosions generate shock waves that propagate in opposite directions, creating pressure overlap zones within the roadway. The pressure waves and shock waves in these overlap zones continuously couple within the roadway. The number of overlap zones decreases incrementally with each encounter of opposing shock waves in the roadway. Unlike single explosion source models, the pressure at various positions within the roadway in multiple explosion source models oscillates due to the coupling of multiple shock waves, with significant peak pressures occurring at the closed end of the roadway and in the pressure overlap zones. Additionally, the propagation patterns of shock waves and flames within the roadway are not associated with the interval distance between explosion sources, whereas the encounter time, speed, and pressure of shock waves increase with the interval distance.

Numerical Investigation on Dynamic Response of Carbon Fiber Honeycomb Sandwich Panels Subject to Underwater Impact Load

This study investigates the dynamic response and failure mechanisms of carbon fiber honeycomb sandwich structures under underwater impact loads using finite element numerical simulation. The geometric modeling was performed using HyperMesh, and the dynamic response simulations were carried out in ABAQUS, focusing on honeycomb core configurations with varying edge lengths, heights, and gradient forms. The Hashin damage model was employed to describe the damage evolution of the composite materials. The simulation results revealed that the dynamic response was significantly influenced by the initial shock wave pressure and the geometrical parameters of the honeycomb cells. Larger cell-edge lengths and heights generally resulted in improved energy absorption and reduced rear panel displacement. Among the different configurations, interlayer gradient honeycomb structures demonstrated superior impact resistance compared to homogeneous and in-plane gradient structures, particularly under higher initial shock wave pressures. These findings contribute to optimizing the design of carbon fiber honeycomb sandwich structures for enhanced impact resistance in relevant applications.

Acoustic deep brain modulation: Enhancing neuronal activation and neurogenesis

BackgroundNon-invasive deep brain modulation (DBM) stands as a promising therapeutic avenue to treat brain diseases. Acoustic DBM represents an innovative and targeted approach to modulate the deep brain, employing techniques such as focused ultrasound and shock waves. Despite its potential, the optimal mechanistic parameters, the effect in the brain and behavioral outcomes of acoustic DBM remains poorly understood. ObjectiveTo establish a robust protocol for the shock wave DBM by optimizing its mechanistic profile of external stimulation, and to assess its efficacy in preclinical settings. MethodsWe used shockwaves due to their capacity to leverage a broader spectrum of peak intensity (10–127 W/mm2) in contrast to ultrasound (0.1–5.0 W/mm2), thereby enabling a more extensive range of neuromodulation effects. We established various types of shockwave pressure profiles of DBM and compared neural and behavioral responses. To ascertain the anticipated cause of the heightened neural activity response, numerical analysis was employed to examine the mechanical dynamics within the brain. ResultsAn optimized profile led to an enhancement in neuronal activity within the hypothalamus of mouse models. The optimized profile in the hippocampus elicited a marked increase in neurogenesis without neuronal damage. Behavioral analyses uncovered a noteworthy reduction in locomotion without significant effects on spatial memory function. ConclusionsThe present study provides an optimized shock wave stimulation protocol for non-invasive DBM. Our optimized stimulation profile selectively triggers neural functions in the deep brain. Our protocol paves the way for new non-invasive DBM devices to treat brain diseases.

Soy proteins modified using cavitation jet technology

Soy proteins are seen as a promising alternative food source for meat with environmentally friendly properties. The problem is that the functional properties of soy proteins do not meet the needs of the food industry, and some existing modification technologies have adverse effects. Recently, cavitation jet technology (CJT) has been studied because it generates high heat, high pressure, strong shear and strong shock waves. This review summarizes the history and mechanism of cavitation jets. The energy generated during the cavitation jet process can open molecular structures, and the shock waves and microjets generated can pulverize the materials by erosion. The impact of the CJT on the morphology, structure, and functionality of soy proteins is discussed. The impact of combining CJT with other techniques on the production of soy proteins was also reviewed. The modification of proteins using two or more methods with complementary strengths, avoiding the disadvantages of certain techniques, makes the modification of proteins more effective. One of the most prominent effects is the combined treatment of cavitation jets with physical techniques. Finally, the review provides a comprehensive analysis of the application of modified soy proteins in the food industry and highlights promising avenues for future research.

Simulations of the optical diffraction patterns produced by the pressure field of a clinical shock wave source

Today, shock waves are used to treat a wide variety of ailments. Consequently, there is a need to develop efficient methodologies for comparing and evaluating the pressure fields generated by different equipment. Hydrophones are commonly utilized for accurate pressure measurements although they can be damaged by pitting due to acoustic cavitation. Furthermore, the range of measurement is limited by the position of the device. Optical methods have also been proposed since the presence of a disturbing device in the wave propagation medium is not necessary, and they provide a broader registering field. Nevertheless, these methods do not provide accurate measurements compared with those obtained with polyvinylidene difluoride or fiber-optic hydrophones. Herein, an optical method for shock wave characterization based on diffraction analysis, that can lead to more precise results, is proposed. The phase fluctuations of a light wave produced when it traverses the shock wave pressure field are calculated. The diffraction patterns produced by this perturbed wave at an observation plane at different propagation distances are presented. Considering the state of the art of high-speed cameras, we conclude that an experimental setup, based on the results reported here, can contribute to the evaluation and comparison of shock wave generators for medical applications.

Analysis of CFRP inter‐laminar cracking location under laser impacts

AbstractIn this study, a combination of theoretical analysis and experimental verification was used to investigate the effects of laser parameters and shock wave shape on the location of layer cracks in carbon fiber‐reinforced plastics specimens. Firstly, the propagation coupling process of trapezoidal, rectangular, and triangular pulses in the material was investigated based on the one‐dimensional stress wave propagation theory. The study analyzed the effects of shock wave pressure amplitude, pulse width, and other factors on the location of layer cracks in the material. Subsequently, laser impact experiments with varying energies and pulse widths were conducted on specimens of different thicknesses to investigate the impact of shock wave pressure amplitude and laser pulse width on the location of layer cracking. The results show that the theoretical analysis of triangular shock waves has broader applicability and can serve as a representative analytical model to describe single‐layer crack damage.Highlights Laser impact experiments with various specimen thicknesses. Laser pulse width determines the initial location of inter‐laminar cracking. The applicability of the triangular pulsed layer cracking formula. The effect of laser energy on pulse amplitude.

Numerical study of cavitation shock wave emission in the thin liquid layer by power ultrasonic vibratory machining

In the field of power ultrasonic vibration processing, the thin liquid layer nestled between the tool head and the material serves as a hotbed for cavitation shock wave emissions that significantly affect the material's surface. The precise manipulation of these emissions presents a formidable challenge, stemming from a historical deficit in the quantitative analysis of both the ultrasonic enhancement effect and the shock wave intensity within this niche environment. Our study addresses this gap by innovatively modifying the Gilmore-Akulichev equation, laying the groundwork for a sophisticated bubble dynamics model and a pioneering shock wave propagation model tailored to the thin liquid layer domain. Firstly, our study investigated the ultrasound enhancement effect under various parameters of thin liquid layers, revealing an amplification of ultrasound pressure in the thin liquid layer area by up to 7.47 times. The mathematical model was solved using the sixth-order Runge–Kutta method to examine shock wave velocity and pressure under different conditions. our study identified that geometric parameters of the tool head, thin liquid layer thickness, ultrasonic frequency, and initial bubble radius all significantly influenced shock wave emission. At an ultrasonic frequency of 60 kHz, the shock wave pressure at the measurement point exhibited a brief decrease from 182.6 to 179.5 MPa during an increase. Furthermore, rapid attenuation of the shock wave was found within the range of R0-3R0 from the bubble wall. This research model aims to enhance power ultrasonic vibration processing technology, and provide theoretical support for applications in related fields.

Spatial-temporal characteristics analysis of laser-induced shockwave pressure by reverse optimization with multi-island genetic algorithm

Spatial-temporal characteristics analysis of laser-induced shockwave pressure by reverse optimization with multi-island genetic algorithm

DEVELOPING THE COMBINED KALMAN-EMD ALGORITHM TO PROCESS BLASTING SHOCKWAVE SIGNALS PROPAGATING IN A WATER MEDIUM

In experiments deploying underwater blast sensors, measured data is always disturbed, expressed as analog peaks in the obtained signal form. Except for pressure peak pmax, other parameters of an underwater explosion such as positive impulse I+, positive phase duration τ+, negative impulse I- and negative phase duration τ- are difficult or almost impossible to extract from this signal type. This article studies developing an algorithm called Kalman-EMD with the combination of Kalman filter and empirical mode decomposition for processing this signal type. The algorithm is applied in 6 data sets measuring the shockwave pressure of underwater explosions by PCB W138A05 sensors with the same condition that 184 grams of A-IX-2 explosive is detonated underwater. The results show that noise in signals is significantly eliminated. For the blasting parameters of processed signals, which can be compared with theory such as I+ and τ+, although it witnesses a small trade-off when errors of I+ enhance from about 3% to 6%, errors of τ+ are significantly decreased from about over 30% to only about 3%. Especially other pieces of information such as I- and τ- can be extracted from the processed signal so this trade-off can be acceptable. Hence, this algorithm can be applied to denoise and extract parameters from shockwave pressure signals of underwater explosions.