Shock Pressure Research Articles

The effect of the accumulator on oil pressure shock suppression based on mill screw-down system

This paper takes the servo valve front accumulator as the research object. It analyzes its effect in suppressing pressure shock and improving system pressure stability. Finally, it achieves the purpose of improving the control accuracy of the hydraulic screw-down system of the rolling mill. According to the actual operating requirements, the mathematical model of the servo valve front accumulator is established. The pressure shock suppression effect of the accumulator is simulated and analyzed with different parameters in the process of servo valve adjustment and reversal. Finally, it is verified by experiment. The optimal selection method of the parameters of the accumulator is obtained to provide theoretical and empirical support for the study of methods to enhance the system pressure stability and improve the control accuracy.

코비드19 위기와 유럽통합

Recently, the Covid-19 crisis and the war in Ukraine have emphasized the question of the ‘raison d’ê̂tre’ of the European Union. These two crises have been the catalyzing processes revealing the nature of European integration through the shock waves and pressures on Europe. This research aims at analyzing the theoretical question of the relationship between crisis and integration – “Does crisis bring about integration?” - through a concrete case study. The covid-19 crisis seems to have so far strengthened European integration. However the European reaction to covid-19 crisis has not automatically and mechanically led to integration like the often cited formula of Jean Monnet. The first impact of the covid-19 crisis was rather the destruction of one of the most substantial achievements of European integration; Not only the freedom of movement had to be suspended to prevent disease expansion, but member-states also demonstrated non cooperative behaviour. It is only in a second step that Europe reacted cooperatively through policy integration on both health and financial sectors, with strong potential for further structural reinforcement. The main focus of this article is to describe those factors which form the basis of the macro-linkage between the covid-19 crisis and European integration in the period 2020-2023. I conclude by raising the need to compare this European covid-19 crisis study with other regions or/and other European crises.

Ignition delay times of C1–C7 natural gas blends in the intermediate and high temperature regimes: Experiment and correlation

This study presents new ignition delay time data for two multi-component natural gas (NG) blends composed of C1–C7n-alkanes with methane as the major component. New experimental data were recorded using a high-pressure shock tube (HPST) at reflected shock pressures (p5) of 10–30 bar, at temperatures (T5) in the range 770–1480 K, and at equivalence ratios (φ) of 0.5–1.5 in ‘air’. The current results together with published rapid compression machine (RCM) measurements show that higher concentrations of larger molecular weight n-alkanes in the NG blends increase fuel reactivity by more than an order of magnitude with mixtures that have ∼18.75% of C3–C5 components compared to mixtures that have ∼44.4% of C3–C7 components at temperatures below 1000 K. On the contrary, at higher temperatures the effect of increasing reactivity is reduced. NUIGMech1.2 is used to simulate the conditions studied and shows good agreement with the experimental ignition delay time data. A correlation equation is developed through regression analyses using NUIGMech1.2 to predict ignition delay times for a wide range of C1–C7 NG mixtures, in the pressure range 10–50 bar, at temperatures in the range 950–2000 K, and at φ = 0.3–3.0 in air. The proposed correlation expression that employs a traditional Arrhenius form is successfully validated against the new experimental data as well as previously published HPST experimental data.

Evaluation of Mechanical Performance of a New Disc Spring-Cable Counter Pressure Shock Absorber

Mechanical performance evaluation of a new disc spring-cable counter pressure shock absorber is focused on in this study. The proposed shock absorber is always in a compressive working state with energy dissipation capacity under both tension and compression loadings. The design formulas of its axial bearing capacity, vertical stiffness, deformation energy of the shock absorber were derived, and the corresponding specific design process was provided in detail. Experimental and numerical investigations of the mechanical performance were conducted under static and dynamic loadings. The parameters influencing the laws of the mechanical performance of the shock absorber, including loading frequency, pre-compression deformation and loading amplitude, were investigated. The rationality of the proposed shock absorber was firstly verified through comparative analysis using experimental, numerical and theoretical calculations. The shock absorber with a friction coefficient of 0.005 between disc springs, and a friction coefficient of 0.3 between the disc spring and cover plate has the smallest error between experiment and theory for the flattening force. The bearing capacity of the shock absorber exhibits a linear relationship with the loading displacement in static loading. In dynamic loading, however, the bearing capacity shows a trend of slow growth followed by rapid growth. The energy dissipation capacity of the shock absorber shows an increase with the increase of loading displacement. The minimum equivalent damping ratio of all of the dynamic test cases is 7%, with a maximum up to 15.3%. Under the same loading frequency, the equivalent stiffness and equivalent damping ratio have a linear amplification trend with the increase of pre-compression deformation, and the maximum increase of equivalent stiffness is equal to 41.37%. Under the same loading frequency and pre-compression deformation, the energy consumption capacity can be improved by increasing the loading amplitude.

Effect of the central gravitational field on self-accelerating outward propagating flames subjected to the Rayleigh-Taylor instability: Transition to detonation

Within the Boussinesq approximation an elementary model for the deflagration-to-detonation transition triggered by self-acceleration of an expanding flame in a central gravitational field is formulated and explored numerically. The self-acceleration is sustained by the intrinsic Rayleigh-Taylor instability until the Deshaies-Joulin deflagrability threshold is reached, followed by an abrupt transition to detonation. Emergence of the threshold is caused by positive feedback between the accelerating flame and the flame-driven pressure shock that results in the thermal runaway when the flame speed reaches a critical level. The model offers a simple mechanism that may be responsible for the transition to detonation in thermonuclear supernovae. The present study is an extension of the preceding models dealing with constant gravitational fields.

Effect of Al-made burst disk on the shock wave and the spontaneous ignition of high-pressure hydrogen during its sudden discharge

Hydrogen is regarded as the promising energy carrier in the next decades. However, the spontaneous ignition of pressurized hydrogen is one of the safety hazards blocking its safe utilization. In this paper, effect of the Al-made burst disk on the shock wave and the spontaneous ignition of high-pressure hydrogen is experimentally studied and discussed in detail through comparison with the previous results when Ni was used as a material. Pressure transducers and light sensors are employed to detect the shock wave and spontaneous ignition respectively. It is found that shock intensity, i.e., shock pressure and shock speed, decreases with the use of Al. As a result, the minimum burst pressure increases from 4.09 MPa for Ni to 4.51 MPa for Al. The result of the estimation of burst disk opening time and pressure profiles inside high-pressure storage tank prove that the opening time of Al is longer than Ni, which causes the wider hydrogen/air mixture area. The distance L between the contact surface and the leading shock wave increases with the increasing of Mach number, results in the short distance between contact surface and the leading shock wave for Al. After the mixing of cold hydrogen and heated air with high temperature that is close to the leading shock wave, spontaneous ignition occurs early inside the Al-made tubes.

Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland

AbstractThe Stac Fada Member (Stoer Group) is a ~1.2 Ga melt‐rich impact breccia preserved and intermittently exposed along the NW coast of Scotland. Using a combination of x‐ray diffraction and micro‐Raman spectroscopy, we identify potential coesite that is spatially associated with micron‐sized diamonds, as well as disordered carbon phases. Comparing the graphite G‐band of disordered carbon phases in the impact breccia to samples from underlying units indicates that most of the carbon in the Stoer Group was ultimately derived from the underlying Lewisian basement. Disordered carbon phases within the Stac Fada Member have been modified by mild heating within a hot ejecta blanket rather than shock pressure. We also report the first evidence for impact diamonds discovered within the Stac Fada Member. These diamonds have an average Raman shift of 1328.5 cm−1 and are present within both the impact breccia and the shocked gneiss clasts that are present in sandstones directly underlying the Stac Fada Member contact, and within sandstone rafts entrapped in the unit. These findings have implications for the timing of deposition of the Stac Fada Member, which must have occurred after ballistic ejection of Lewisian basement clasts during the impact event.

Experimental and numerical study on ground shock propagation in calcareous sand

Surface explosion tests were conducted on calcareous sands to study the ground shock propagation in this medium. In the tests, ground shock at scaled distances between 0.33 m/kg1/3 and 1.46 m/kg1/3 was measured. After each explosion, the surface craters were observed and measured. The propagation and attenuation law of the peak pressure was derived according to the experimental measurement. The shock wave velocity and rise time were derived based on the pressure time-history curves. The empirical formula for pressure time-history curve of direct ground shock in calcareous sand induced by surface explosion was derived, and the predicted impulses showed good agreement with the experimental impulses. The indirect ground shock induced by air shock compression effect on the soil was discussed. Based on the field blast test results, validated numerical models were established to investigate the propagation of direct and indirect ground shock in calcareous sand. The attenuation law of peak pressure of indirect ground shock was then derived according to the numerical simulation results. Besides the surface explosion scenario, the contained burst cases were also modelled. The critical scaled depth of burial was derived as 1.3 m/kg1/3 in calcareous sand based on the surface crater and shock impulse.

The damage characteristics and formation mechanism of ultrahigh strength 7055 aluminum alloy under hypervelocity impact

This paper studies the damage morphology evolution of ultrahigh strength 7055 aluminum alloy plate under the hypervelocity impact of aluminum projectile, and analyzes the formation mechanism of crater morphology at different impact velocities. It is found that the impact crater evolves from spherical crown shape to spherical-conical composite shape, and eventually transforms into hemispherical shape with the increase of impact velocity. The evolution of crater shape is highly associated with the ratio of steady-state shock pressure and the strength of the alloy. The variation of crater diameter as a function of impact velocity follows the hypothesis of hemispherical theory, while the crater depth shows a great deviation due to the formation of conical region at the crater bottom and spall fracture at the back of the target. It is demonstrated that the formation of conical crater is related to the poor resistance to shear localization of 7055 aluminum alloy due to its low strain hardening capacity under dynamic loading. Hence, adiabatic shear bands are generated and evolve into shear cracks, thereby causing the formation of conical region at the crater bottom. It is suggested that the resistance to shear localization should be highly considered for the design, evaluation and selection of protection materials for spacecraft.

Summanen structure: Further geological and geophysical evidence of a meteorite impact event in Central Finland

AbstractThe Summanen structure is located in Central Finland and is one of Finland's 12 known meteorite impact structures. In 2017, the discovery of Summanen was based on numerous shatter cone boulders with planar deformation features (PDFs) and a circular electromagnetic anomaly, which is 2.6 km in diameter. The site was revisited in 2020 and 2022, and shatter cone‐bearing outcrops were discovered. PDFs and feather features were identified in samples from these outcrops. A total of 38 PDF sets in 27 quartz grains resulted in rational crystallographic orientations concentrating on {104}, {103}, {102}, and {112}, implying shock pressures of 2–20 GPa. Gravity measurements were taken, and the electrical conductivity of the structure was studied. The gravimetric results revealed a circular negative anomaly of about 4 km in diameter, with an amplitude of −3.5 mGal. Excluding the gravitational effect of water and Quaternary sediments reduces the anomaly to −1.6 mGal. A bowl‐shaped conductive layer, likely containing relict saline water in the impact‐fractured bedrock, was identified to a depth of 240 m. Topographic and bathymetric data were combined to determine the impact's effect and interpret the level of erosion. Cobbles of sedimentary sand‐ and siltstones were found on the coastline of Lake Summanen. Based on their similarity to those found in the Söderfjärden impact crater with a Cambrian age, it is likely that these rocks and post‐impact infill are also of a similar age.

A strategy to introduce multi-gradient structures into iron by explosive shock wave processing

A strategy combining shock-induced phase transition, twins, and dislocations to produce a multi-gradient structure in Fe is designed and proposed by the explosive processing method. A specific emulsion explosive is designed to introduce gradient pressure into iron ranging from 8.3 to 13.4 GPa by smooth particle hydrodynamics method. The pressure range generated by explosive processing covered shock loading phase transition point, shock unloading phase transition point, twin activating point and elastoplastic dislocation point of iron, creating gradient phase transition, gradient twins, gradient dislocations and gradient grain size structures in iron. The mechanism of gradient grain size formation is illustrated based on the twins and dislocation boundaries. Due to the multi-gradient microstructure, a demonstrating gradient hardness range from 1231.3 Hv to 89.8 Hv is distributed from the surface to the internal of the iron. This method lays an experimental foundation for Fe, Ti, Mg based gradient materials that undergo phase transition under low shock pressure.

Validation of numerical simulations for investigating flow control in hypersonic inlets

Various flow control devices have been conceived for hypersonic inlets to suppress the inlet unstart and reduce the total pressure loss over the wide range of operating conditions of hypersonic systems. In particular, bleed systems that remove the low-momentum portion of the flow have drawn attention because they effectively reduce shock-induced flow separation and suppress inlet unstart. Numerical simulations are crucial for investigating the effectiveness of different bleed configurations in hypersonic inlets during the design phase. However, the flow structure in these inlets and the effect of the bleed on the flow are challenging to predict due to complicated factors such as shock-wave/boundary-layer interactions and compressibility effects. Moreover, since the boundary conditions, turbulence model, and turbulence corrections affect the numerical results, the most appropriate model can be difficult to determine. Therefore, a numerical solver was developed and evaluated on a series of validation cases with available experimental data to establish the fidelity of the numerical simulations. Seven validation cases, ranging from an elementary configuration involving a flat plate to a complex configuration involving a flat plate with a porous bleed and plenum chamber, were investigated. The flat plate flow numerical results, including the turbulent boundary layer and shock-wave/laminar boundary-layer interactions, were consistent with previous experimental and numerical results. However, in the hypersonic inlet cases, the actual physical phenomena could not be represented without considering compressibility and streamline curvature effects, which depend on the hypersonic inlet configuration. Thus, the effects of turbulence corrections on the numerical results of various hypersonic inlet configurations were examined. For cases with rapid expansion near the inlet throat or inlets with curved walls, compressibility or rotation/curvature corrections were necessary to accurately capture the size of the recirculation zone and reproduce the wall pressure data and shock structure along the flow path. However, for bleed flows on flat plates, the simulations were accurate without applying turbulence corrections. Thus, these turbulence corrections should be applied only when rapid expansion occurs or the wall near the shock-induced separation zone is curved. This paper provides the best practice appropriate for various supersonic, hypersonic flow cases, and can be utilized in future numerical studies on hypersonic inlet boundary layer control.

A Review Paper on Designing of Knee Support System for Elderly People

Knee pain can now occur in people as young as their 30s, not just in their 60s and 70s. As the elderly population grows, hospitals will have a hard time accepting more patients due to the high demand for services. The focus will shift from post-accident care to preventative care, especially for people with knee pain. The first step in designing and developing a successful knee exoskeleton is to conduct high-quality research on the following topics: knee structure, the diseased state of osteoarthritis, knee kinematics, gait analysis, the existing market for knee exoskeletons, actuation methods, novel software, sensors, and more. The study found that applying heat to the knee increases tissue temperature, softens surrounding tissues, reduces tissue viscosity, increases connective tissue extensibility, reduces pain, and increases joint mobility. Flexible sensors are used in wearable devices such as electric skin, flexible strain gauge sensors, motion detectors, and self-repairing sensors. A self-adjusting knee joint is being developed to allow passive self-alignment with the ICR of the natural knee. Neoprene rubber is a synthetic closed-cell rubber used in medical devices, but it lacks breathability and restricts the movement of water vapor, moisture, and heat. Knitted stretch fabrics provide warmth and compression to injured areas, and foam provides shock protection and pressure points to promote healing. Test methods are used to evaluate the dimensional, mechanical, and thermo-physiological properties for material selection. A wearable suit design was studied using a Design of Experiments approach, with eight key parameters identified and an optimization method developed. Robotics and automation technology were used to address discomfort issues in the body-worn knee exoskeleton design.

Methodology for determination of critical crack depth in a class-I component

In this study, a methodology for the determination of critical crack depth in a class-I component using the failure assessment diagram has been proposed and implemented through the finite element method. Overviewing the literature in the field of fracture mechanics, the need for the development of such methodology was felt, as such straightforward methodologies are difficult to find in contemporary literature. As a case study, the proposed methodology was then successfully applied to a pressurized water reactor’s pressure vessel closure head (class-I component). Subsequently, the critical crack depth was determined through a failure assessment diagram under pressurized thermals shock induced during the small break loss of coolant accidental and Rancho-Seco transient accidental conditions of the reactor.

Analysis of the Coordination Effects and Influencing Factors of Transportation and Tourism Development in Shaanxi Region

With the accelerated growth of global tourism and the increasing availability of transport, the coordination and interaction between the tourism economy and transport have become a topic of great interest. This study seeks to analyse the coordination effects and influencing factors of Shaanxi’s tourism economy and transportation, thereby contributing to the sustainable development of the region’s tourism economy. To achieve this, we develop a tourism economy–transportation evaluation index system and employ the system coupled with the coordination model and entropy method to conduct a thorough analysis. The research spans over the years 2003–2021. According to the findings of this study, the integration and coordination of tourism economy–transportation and tourism development in Shaanxi are exhibiting an upward development trend. Over the years, the degree of coupling coordination has progressed through the stages of uncoordinated development, transformational development, and coordinated development, with the recent epidemic upheaval resulting in a primary level of coordination. In addition, the transport system has a significant impact on the coupled and coordinated development of the tourism economy–, with the size of the transport base and transport efficiency serving as the driving factors and transport pressure and epidemic shocks serving as significant influencing factors. Due to the fluctuations of the global pandemic, the coordination of the tourism system declines sharply in 2020, but recovers in 2021 as the pandemic progressively stabilises. Through this study, we can gain a better understanding of the relationship between the tourism economy and transport in Shaanxi and devise strategies and policies to support the development of sustainable transport and tourism systems.

Quality of fish eggs and production of androgenetic and gynogenetic doubled haploids (DHs).

Induced development of haploid embryos (H) with only paternal (androgenesis) or maternal (gynogenesis) chromosomes requires irradiation of eggs before fertilization or activation of eggs with irradiated spermatozoa, respectively. To provide doubled haploids (DHs), androgenetic and gynogenetic haploid zygotes need to be subjected to the thermal or high hydrostatic pressure (HHP) shock to suppress the first mitotic cleavage and todouble paternal or maternal haploid set of chromosomes. Androgenesis and mitotic gynogenesis (mito-gynogenesis) result in the generation of fully homozygous individuals in a single generation. DHs have been utilized in selective breeding programs, in studies concerning the phenotypic consequences of recessive alleles and to evaluate the impact of sex chromosomes on the early ontogeny. Moreover, the use of DHs for the NGS approach radically improves de novo the assembly of the genomes. However, reduced survival of the doubled haploids limits the wide application of androgenotes and gynogenotes. The high mortality of DHs may be only partly explained by the expression of recessive traits. Observed inter-clutch variation in the survival of DHs developing in eggs originating from different females make it necessary to take a closer look at the quality of the eggs used during induced androgenesis and gynogenesis. Moreover, the developmental competence of eggs that are subjected to irradiation before fertilization in order to deactivate maternal chromosomes when undergoing induced androgenesis and exposed to the physical shock after fertilization that leads to the duplication of the zygotes in both mito-gynogenesis and androgenesis may be also altered as irradiation and sublethal values of temperatures and hydrostatic pressure are considered as harmful for the cell organelles and biomolecules. Here, recently provided results concerning the morphological, biochemical, genomic, and transcriptomic characteristics of fish eggs showing high and low competence for androgenesis and mito-gynogenesis are reviewed.

Characteristics and load reduction method of the deep-sea implosion of the ellipsoidal and egg-shaped pressure hulls

Pressure hulls is an essential part of the deep-sea submersible and may implode to emit shock pressure wave. This paper establishes a deep-sea implosion model based on the Eulerian finite element method, and two implosion conditions, ellipsoidal and egg-shaped, are studied. It is found that the pressure load at the gauging point in the long semi-axis direction is always greater than that in the short semi-axis direction when the two models implosion. Introducing the radius ratio β, it is found that the pressure load after the implosion of the two models increases first and then decreases with the increase of β. Then the dimensionless number Ma is introduced to simulate the change of pressure load under implosion in different water depths. It is found that pressure peak Pm∗ decreases by a factor of Ma−0.5 as Ma increases, and the time Tm∗ to reach the pressure peak increases linearly with the rise of Ma. Therefore, the pressure load caused by implosion can be reduced by reasonably selecting the radius ratio of the pressure hull. In addition, the implosion load when a plurality of pressure hulls are arranged together can be reduced by organizing them along the short semi-axis direction.

Effects of shock-induced chemical reaction on equation of state for Ni/Al energetic structural material

The equation of state (EOS) for energetic structural materials (ESMs) has been drawn a great attention due to the absent comprehensive understanding on the effect of the shock-induced chemical reaction. In this paper, the shock compression behavior of Ni/Al ESM is investigated by developing the EOS, which mainly considers the effects of the chemical reaction and the reaction products. The chemical reaction is based on the Avram-Erofeev kinetic law and the Arrhenius equation. The study concerns the shock pressure, the relative volume, the temperature, and the chemical reaction during the shock compression. The effects of the initial porosities, the stoichiometric ratios and inert additives were mainly discussed. The results showed that high porosity would induce high temperature rise. Different stoichiometric ratios would produce different temperature rise. When the stoichiometric ratio Ni: Al ​= ​1:1, the temperature rise is highest. In addition, the inert additive material would obviously reduce the temperature rise. Finally, the developed model improved the temperature calculation, compared with the existing model.

Study on the Vibration Displacement of Hydraulic Pipeline System Excited by Fluid Impact

Hydraulic impact had an effect on pipeline vibration displacement, so it was important to study the external lateral impact periodic force on fluid-structure coupling vibration displacement of hydraulic pipeline. Based on Bernoulli beam model, the fluid-structure coupling vibration equation of flexible pipeline was established by analyzing the stress of flexible pipeline under the action of internal flow. The hydraulic system pipeline was simulated whether the pipeline was subject to periodic impact force. The displacement-time curves in x, y and z directions of vibration monitoring points of hydraulic flexible pipelines were obtained, and the maximum displacement-time curves of fluid-structure coupling vibration under different pressure hydraulic impact were obtained. The simulation results were shown that the vibration of monitoring points in x, y and z directions of hydraulic impact pressure increased and the total displacement of the pipeline middle section of the hydraulic system decrease continuously, and then they tend to stabilize after a period of attenuation. The maximum displacement value of the X-direction monitoring point in the middle part of the hydraulic system pipeline was 9.5e −5 m, and the displacement vibration was stable at 0.135s. The maximum y-displacement was 3.1e −4m, and the vibration was stable at 0.2 s. The maximum z displacement was 1.32e-4 m, and the vibration was stable at 0.36 s. The total displacement was 3.35e −4 m, and the vibration was stable at 0.43s. Increasing the impact pressure, the maximum displacement of the hydraulic pipeline vibrations were larger, and the attenuation of the maximum values were faster. The research results provide a reference for the hydraulic system to prevent pressure shock and reduce vibration.

Experimental Evidence for Shear‐Induced Melting and Generation of Stishovite in Granite at Low (<18 GPa) Shock Pressure

AbstractKnowledge of the shock behavior of planetary materials is essential to interpret shock metamorphism documented in rocks at hypervelocity impact structures on Earth, in meteorites, and in samples retrieved in space missions. Although our understanding of shock metamorphism has improved considerably within the last decades, the effects of friction and plastic deformation on shock metamorphism of complex, polycrystalline, non‐porous rocks are poorly constrained. Here, we report on shock‐recovery experiments in which natural granite was dynamically compressed to 0.5–18 GPa by singular, hemispherically decaying shock fronts. We then combine petrographic observations of shocked samples that retained their pre‐impact stratigraphy with distributions of peak pressures, temperatures, and volumetric strain rates obtained from numerical modeling to systematically investigate progressive shock metamorphism of granite. We find that the progressive shock metamorphism of granite observed here is mainly consistent with current classification schemes. However, we also find that intense shear deformation during shock compression and release causes the formation of highly localized melt veins at peak pressures as low as 6 GPa, which is an order of magnitude lower than currently thought. We also find that melt veins formed in quartz grains compressed to >10–12 GPa contain the high‐pressure silica polymorph stishovite. Our results illustrate the significance of shear and plastic deformation during hypervelocity impact and bear on our understanding of how melt veins containing high‐pressure polymorphs form in moderately shocked terrestrial impactites or meteorites.