Shock Wave Loading Research Articles

Damage characteristics of cabin in navigational state subjected to near-field underwater explosion

An arbitrary Lagrange-Euler (ALE) method is used to establish a numerical model for the fluid-structure interaction of near-field underwater explosion while cabins are under sailing conditions. First, the ALE method is used to calculate shock wave and bubble pulsation loads of free field underwater explosion. The results show that the values of shock wave peak, bubble fluctuation period, maximum radius of bubble are similar to empirical formula calculation, which verifies the accuracy of ALE method in calculating explosion loads. On this basis, from the aspects of local damage, longitudinal strength and impact environment of cabin structure, the dynamic response characteristics of cabin structure under the coupling of impact and bubble load at a certain speed and different explosion distance are analyzed and compared with that at static condition. The results show that compared with the static state, the local damage is weakened, the longitudinal strength is increased, the difference of longitudinal strength between navigation and static state is 7%–12%, the shock spectrum value of the compartment corresponding to the explosion source is reduced, and the shock spectrum value of the adjacent compartment is slightly increased; When the cabin is sailing, the increase of the explosion distance within the maximum radius of bubble pulsation increases the action area of bubble pulsation load, and the effect of bubble pulsation load is enhanced, but the coupling enhancement of explosion load is difficult to appear, so that the damage of cabin structure is reduced. The working condition of the cabin suffering from near-field underwater explosion damage under the navigational state analyzed in this paper is closer to the reality, and more truly reflects the process of underwater explosion shock wave and bubble load coupling applied to cabins, which lays a foundation for the fuze warhead coordination design and relevant parameter setting when the torpedo and other underwater weapons give full play to the damage efficiency.

Experimental study on the elastic-plastic dynamic response of shallow-buried corrugated steel-plain concrete composite structures under long-duration plane blast wave loading

To study the elastic-plastic dynamic response characteristics of shallow-buried corrugated steel-plain concrete (CSPC) composite structures under long-duration plane blast loads, a series of tests were conducted in a large confined blast-resistant test facility using the plane charge explosion technique (PCET), and the dynamic response and deformation laws of CSPC arches, reinforced concrete (RC) arches and plain concrete (PC) arches under different blast loads were comprehensively compared and analyzed. The test results show that under this test condition, the plane air shock wave overpressure peak with the increase in charge is basically a linear growth, but the shock wave pressure duration of action and impulse growth rate gradually decreased, the test device simulated by the explosion shock wave pressure duration of the maximum action time of more than 340 ms. Comparing the differences in the dynamic response of the three structures, it was found that when the peak long-duration shock wave overpressure acting on the structure reached 0.09 MPa, the PC model had plastic deformation, and the combined reinforced concrete and CSPC structure exhibited fully elastic deformation. When the peak shock wave overpressure reaches 0.238 MPa, the RC model begins to show plastic deformation. When the peak shock wave overpressure increased to 0.315 MPa, all models produced significant plastic deformation. The deformation resilience of the CSPC composite structure under the above-mentioned blast shock wave load is greater than that of RC and PC structures, which have good deformation recovery ability and can effectively reduce the damage to the structure by blast shock. On the contrary, the peak structural vibration acceleration caused by the blast shock wave is greater in the CSPC combined structure than in the RC and PC structure, and the deformation rebound and oscillation of the corrugated steel plate is the main way of impact energy dissipation. The results of the study provide an experimental basis for the simulation of long-duration plane blast waves and the optimal design of CSPC blast-resistant structures.

Role of temperature and preexisting dislocation network on the shock compression of copper crystals

Shock wave experiments show that many annealed face-centered cubic metals exhibit an anomalously increasing yield strength with temperature at high strain rates. Such an increase is usually associated with the multiplication of dislocations in the phonon friction mode, which slows with temperature. However, the effect of temperature on the structure of the shock wave and the yield strength of metal crystals, including those with microstructure, remains elusive. In this paper, we perform molecular dynamic simulations of shock-wave loading for [110] and [111] copper crystals of 0.45 and 0.80μm length in a wide range of temperatures between 100 and 1100K to understand the role of temperature and preexisting dislocations on the Hugoniot Elastic Limit (HEL). We show that, in ideal copper crystals, the elastic precursor exhibits a form of plateau, and the HEL almost does not change with shock propagation distance. However, at higher impacts, the perturbations of an elastic precursor are observed leading to fluctuations in the HEL value. We show that temperature dependencies of the HEL are strongly anisotropic. The HEL values tend to decrease with temperature for [110] perfect copper crystals, and to increase with temperature for [111] copper crystals. This surprising result is explained by the presence of dislocation substructures in a plastic wave in [110] crystals, which reduces the mobility of dislocations and makes the process of dislocation nucleation more dominant than in [111] crystals. Preexisting dislocations in copper crystals allow the HEL to decay much faster than in ideal crystals. In contrast to ideal [110] crystals, [110] crystals with dislocations exhibit increasing HEL values with temperature, as do [111] crystals. We find that the HEL dependence could be well approximated by a power law, but the decay power changes as the wave propagates. The decay power values lie between 0.5 to 0.7 in the second stage for both [110] and [111] crystals, which is consistent with experimental results with polycrystalline annealed copper. Our findings extend our understanding of temperature-dependent mechanical properties of materials under high strain rate and crystal plasticity.

Strength Characteristics of a Heat-Resistant Metal-Matrix Composite Inconel 625–5%NiTi–TiB2 Alloy Fabricated by Direct Laser Deposition under Shock-Wave Loading

The Hugoniot elastic limit and spall strength were measured for a heat-resistant metal-matrix composite Inconel 625–5%NiTi–TiB2 alloy additive manufactured (AM) by direct laser deposition. The strength characteristics of the alloy were obtained from the analysis of the complete wave profiles recorded with a VISAR laser Doppler velocimeter during shock-wave loading of the samples. The samples were loaded using a PP50 pneumatic gun or ad hoc explosive devices along and across the material deposition direction in order to determine the strength anisotropy of the AM alloy under study. The maximum shock compression pressure was ~7 GPa, and the strain rate under tension before spalling varied in the range of 105–106 s–1. Kinetic dependencies of elastic/plastic transition and critical fracture stresses vs. loading conditions were plotted. It was shown that the Hugoniot elastic limit of the alloy under study decreases as the shock wave travels into the sample, while the spall strength increases as the material’s strain rate increases at the moment of spall fracture. A comparison of the strength characteristics of the Inconel 625–NiTi–TiB2 composite alloy with the original Inconel 625 alloy has shown that an addition of 5% of powder based on NiTi-TiB2 leads to a decrease in its elastic limit and critical fracture stresses upon spalling by more than 10%. The alloy under study demonstrates anisotropy of strength properties relative to the material deposition direction.

Shock Compression of Fluorapatite to 120 GPa

AbstractApatite is a phosphate mineral relevant to shock metamorphism in planetary materials. Here, we report on the response of natural fluorapatite from Durango, Mexico, under shock wave loading between 14.5 and 119.5 GPa. Wave profile measurements were obtained in plate‐impact experiments conducted on [0001]‐oriented fluorapatite single crystals. To 30 GPa peak stresses, we observed a two‐wave structure indicating an elastic‐inelastic response with elastic wave amplitudes of 10.5–13.1 GPa. Between 39.1 and 62.1 GPa, a complex wave structure was observed involving the propagation of three waves. At and above 73.7 GPa, only a single shock wave was observed. The data above 73.7 GPa provided the following linear shock velocity—particle velocity relationship: Us = 6.5(2) + 0.78(6) up, (mm/μs). Above 80 GPa, the densities in the shocked state exceed both the extrapolated 300‐K density of fluorapatite and the predicted 300‐K density for a mixture of the high‐pressure assemblage, tuite, and CaF2. This result indicates that fluorapatite undergoes a transition to a denser structure under shock loading at these conditions. The shock response of fluorapatite is observed to be similar to that of enstatite but stiffer than quartz and albite at the stresses examined in this work.

Comparative study of the explosive blast resistance of metal and composite materials used in defence platforms

Naval ships, military aircraft and land defence platforms are mostly constructed using steel, aluminium alloy, carbon fibre composite and/or glass fibre composite materials. Defence platforms are at risk from shock wave loads generated by explosive events, and therefore it is imperative that the construction materials are resistant to blast-induced deformation and damage. A comparative assessment is presented into the dynamic deformation and damage of metals and composites representative of naval construction materials when subjected to explosive air blasts. Flat plates of equal thickness (4 mm) or plates of similar areal density (in the range 6.2–9.2 kg/m2) made of the four materials were subjected to explosive blasts. Experimental blast testing and finite element (FE) modelling revealed that when the plate thickness was the same (4 mm) then the steel experienced less deformation (by ∼50–60%) and plasticity than the aluminium alloy due to its higher mechanical properties. The steel and aluminium plates were more resistance to blast-induced deformation (by up to ∼260–320% and ∼130–145% respectively) than the composite materials of the same thickness (4 mm). However, when the materials are compared on similar areal density, which is critical for lightweight design, the blast performance of the composite materials was similar to aluminium alloy and superior to steel. Deformation of the steel was up to 50% higher than the other construction materials, with the percentage increase rising with blast impulse.

Dynamic response prediction of prototype from scale-down model for I-core sandwich panels subjected to internal explosion

Cabin scale-down model experiments are an effective approach to investigate the dynamic response of I-core sandwich panels subjected to internal explosion. However, it is difficult to guarantee the complete geometrical similarity in terms of plate thickness for I-core sandwich panels between the scale-down model and prototype due to manufacturing process restriction and thickness specifications of commercially available plates. To resolve the above issue, a new and more reasonable dynamic response prediction method with high accuracy for prototype based on scale-down model test was proposed in the present work. The feasibility and accuracy of proposed prediction method were theoretically, experimentally, and numerically verified. The effects of TNT charge mass, correction method of TNT charge mass, and quasi-static pressure load were investigated. Results show that the proposed prediction method from the energy point of view has high accuracy and good feasibility when the plate thickness of scale-down model distorts. In the proposed approach, the TNT charge mass is corrected through specific impulse correction. Higher accuracy is gained by using the proposed prediction method in the case of internal explosion with large TNT charge mass. Directly correcting the TNT charge mass on the basis of geometrical similarity still underestimates the dynamic response of incomplete scale-down model when plate thickness distorts. It is not reasonable to ignore the effect of quasi-static pressure load, because the specific impulse of quasi-static pressure load is much larger than that of shock wave load. This work can provide practicable and accurate application guidance for the design of internal explosion scale-down model experiments for I-core sandwich panels.

Numerical simulation of the behavior of enstatite up to 1.4 TPa

An accurate description of the effect of extreme pressure and temperature on the physical properties of materials is required to understand the structure and composition of the mantle of the Earth and similar planets. One of such materials is enstatite MgSiO3, which causes increased interest in the investigating of its behavior under intense dynamic loads. It is proposed to consider the shock-wave loading of enstatite as a mixture of quartz oxides SiO2 and MgO periclase in an equal stoichiometric ratio based on experimental data in which decomposition of magnesium silicates was observed. Calculations are performed using a thermodynamically equilibrium model that takes into account the phase transitions of the components. Phase transitions of SiO2 and MgO are taken into account when modeling high-energy effects on enstatite. The results are compared with the data obtained on the basis of shock-wave loading experiments, as well as with calculations based on the PREM model performed based on the results of seismic exploration. Keywords: equation of state, phase transitions, quartz oxide, periclase oxide, enstatite.

ПРИМЕНЕНИЕ ШИРОКОДИАПАЗОННОГО УРАВНЕНИЯ СОСТОЯНИЯ СМЕСИ К ОПИСАНИЮ ПОВЕДЕНИЯ ПОРИСТОГО ЖЕЛЕЗА И СМЕСЕЙ, СОДЕРЖАЩИХ ЖЕЛЕЗО

This paper considers the behavior of porous iron and iron-copper mixtures within a singlecontinuum thermodynamic equilibrium medium. This model describes the behavior of the medium under the shock-wave loading and the isoentropic unloading of solid and porous iron and iron-containing mixture samples using only the parameters of the equation of state and mass concentrations of the components. The comparison of the calculated results with experimental data suggests the effectiveness of the proposed equation for modeling.

Численное моделирование поведения энстатита до 1.4 TPa

An accurate description of the effect of extreme pressure and temperature on the physical properties of materials is required to understand the structure and composition of the mantle of the Earth and similar planets. One of such materials is enstatite MgSiO3, which causes increased interest in the investigating of its behavior under intense dynamic loads. It is proposed to consider the shock-wave loading of enstatite as a mixture of quartz oxides SiO2 and MgO periclase in an equal stoichiometric ratio based on experimental data in which decomposition of magnesium silicates was observed. Calculations are performed using a thermodynamically equilibrium model that takes into account the phase transitions of the components. Phase transitions of SiO2 and MgO are taken into account when modeling high-energy effects on enstatite. The results are compared with the data obtained on the basis of shock-wave loading experiments, as well as with calculations based on the PREM model performed based on the results of seismic exploration.

Mathematical modeling of the behavior of metals and alloys under shock-wave loading

Mathematical modeling of the behavior of metals and alloys under shock-wave loading

Experimental Study on the Cumulative Damage of Shipboard Structure Subject to Near-field Underwater Explosions

To explore the cumulative damage law of near-field underwater explosions on the side of the ship structure, the multi-cabin model of the shipboard local structure is designed and applied to close-in underwater explosion experiments with different explosive masses and model conditions. The pressure load of the explosion shock wave near the water surface is obtained and analyzed. The damage results, such as the damage pattern of the model and the damage range of cabins, are acquired. The comprehensive comparison shows that: the secondary explosion on the side has a significant cumulative damage effect; the damage pattern of the structure is closely related to the proportional distance of the explosion. The damaged power of a single large charge explosion on the shipboard is bigger than the cumulative damage caused by two small explosions. The results of this study can provide a reference for the research on the damage and protection of the ship.

Investigation and Design of the Transonic Laminar Flow Characteristics in a Laminar Aircraft

Reducing drag is critical to aircraft design. In recent years, laminar technology has become one of the most important feasible technologies for civil aircraft drag reduction design under many design constraints. However, various factors have a certain impact on the laminar flow characteristics in the state of transonic flight. Therefore, it is necessary to deeply understand the specific effects of various flight parameters on the characteristics of laminar flow. In this paper, a parameter sensitivity analysis for a central experimental wing in a special layout aircraft was carried out to investigate its transonic laminar characteristics. Then, the airfoil of the central experimental wing of the aircraft was designed for real flight. The RANS (Reynold-averaged Navier–Stokes) method combined with the γ−Reθ transition model based on local variables was used. The computational approach was validated by the wind tunnel tests and analyzed by the grid independence analysis. The sensitivity mainly focuses on the transition location and the length of the laminar flow zone of the central experiment under different boundary conditions. The transonic transition was affected by a variety of interacting factors that include FSTI (free stream turbulence intensity), pressure gradient, Re (Reynolds number), Ma (Mach number) and α (angle of attack, degree). The essence of the transition is the disruption of flow stability caused by the increase in flow entropy. Among these factors, FSTI directly affects global flow stability, and the pressure gradient affects local flow stability. Ma and α can indirectly affect the flow stability by changing the pressure gradient. Re can control the boundary layer properties to change the flow stability, whereas its effect is easily determined by the pressure gradient. Finally, the improved design of the airfoil with the central experimental wing was conducted. The design of weak shock wave and aerodynamic load on the rear part of the airfoil can improve the aerodynamic characteristics (CL, lift coefficient, increases by 0.28) of the airfoil, which can reduce the load burden on the outboard wing without affecting the laminar flow characteristics of the airfoil. In the next step, cross-flow instability will be considered.

A study on damage characteristics of double-layer cylindrical shells subjected to underwater contact explosion

In this study, the damage characteristics of double-layer cylindrical shells with interlayer water subjected to small charge underwater contact explosion were investigated through experimental and numerical methods. At the same time, the distribution characteristics of the field pressure near the double-layer cylindrical shells and detailed bubble dynamics were revealed. The experimental results showed that there were crevasse and non-crevasse areas in the outer shell of the double-layer cylindrical shells, which form “inrushing bubbles” and “induced bubbles” in the interlayer water, respectively. Their subsequent bubble collapse behavior continued to impact the inner shell. Based on the traced analysis of the field pressure and deformation duration characteristics of the double-layer cylindrical shells, the load characteristics of the shock wave, interlayer bubble (inrushing bubble and induced bubble), and outboard bubble load sequence response to double-layer cylindrical shells were obtained.

Study on directional enhancement effect of underwater explosion for cylindrical explosive with large length-to-diameter ratio and structural response of nearby water-back plate

In order to study the directional enhancement effect of underwater explosion for cylindrical explosive with large length-to-diameter ratio, based on the experiment and ALE method, the influences of length-to-diameter ratio on the shock wave and bubble load as well as the structural response of nearby water-back copper plate are analysed. Meanwhile, the influence of the explosive weight on the directional enhancement effect is considered. Some instructive conclusions can be drawn. i) As the length-to-diameter ratio increases, the propagation velocity increases in the radial direction and decreases in the axial direction, and the high-pressure area gradually concentrates in the radial direction. ii) In the range of 1:1–8.2:1, increasing the length-to-diameter ratio enhances the shock wave and bubble load in the top direction and facilitates the formation of a stable bubble jet in this direction. iii) Increasing the length-to-diameter ratio enhances the damage effect of combined load in the top and bottom directions. When the length-to-diameter ratio increases from 1:1 to 8.2:1, the maximum plastic deformation of the water-back copper plate is increased by 26.2%. iv) The directional enhancement effect will be more obviously if the maximum bubble radius is larger than the distance between the structure and the explosive.

Behavior of a Magnesium Alloy under High-Speed Strain under the Action of a Shock-Wave Load

Behavior of a Magnesium Alloy under High-Speed Strain under the Action of a Shock-Wave Load

Investigating the Mechanical Performance on Static and Shock Wave Loading of Aramid Fiber-Reinforced Concrete

Fiber-reinforced concrete (FRC) has been used for over a century to improve the mechanical properties of concrete. Kevlar ® 29 fiber (KF) is one of the most popular aramid fibers used in industrial products. This research investigated the effect of the fiber length, the weight ratio of fiber to cement, the mix-proportion of two fiber lengths, and the sizing on the fiber surface on the mechanical properties of Kevlar fiber-reinforced concrete (KFRC) under static, dynamic, and shock wave loadings. Two lengths of chopped KF and three different weight ratios of fiber to cement were mixed in the KFRC specimens for comparison. Moreover, this study also compared how the five mix-proportions of two fiber lengths affected the mechanical properties of mix-proportion KFRC. KF was dispersed by the pneumatic method first, and then, the separated KF was mixed into the concrete to make KFRC. The results indicated that the KFRC specimens with a 10‰ weight ratio of fiber to cement exhibited the maximum compressive, flexural, and splitting tensile strengths, regardless of whether the fiber length was 12 mm or 24 mm. The main finding showed that the specimen mixed with 24 mm KF could endure the highest impact resistance under different impact energies. From the shock wave test, the external damage on the front and rear faces of all KFRC slabs and the KFRC slab reinforced with two layers of KF sheets was less than that of the benchmark slab. The testing results showed that KF greatly enhanced the static and dynamic mechanical performances of concrete, and the KFRC specimen with a 10‰ weight ratio and 24 mm length KF with sizing exhibited the best performance.

Gas Dynamics Processes above the Polymers Surface under Irradiation with Broadband High-Brightness Radiation in the Vacuum Ultraviolet Spectrum Region.

Obtaining new data on the gas-dynamic responses from the polymer samples (polytetrafluoroethylene, PTFE) irradiated by powerful VUV radiation from compressed plasma flows is in the focus of the present study. An erosion type magnetoplasma compressor (MPC), a type of plasma focus discharge, was used as a radiation source. The operating voltages of the MPC were between 15 and 25 kV, the maximum measured discharge current was 200 kA, and the radiation energy in the VUV range was ≈1–2 kJ. The VUV fluxes on the sample surface were high and equal to ≈1022–1024 photons cm−2·s−1. Double-exposure laser holographic interferometry and schlieren photography were used to diagnose and visualize the gas-dynamic structures. The spatial distribution of the parameters (temperature, pressure and concentrations of electrons and ions) was defined based on the assumption of local thermodynamic equilibrium. It has been demonstrated that the maximum temperature ranged from ≈ 10 to 15 kK in the plasma layer. The electron concentration was ≈ (0.7–1.6) × 1018 cm−3 in this region. The used techniques of optical diagnostics and procedures of result processing make it possible to obtain data on the dynamics of polymer ablation, which occurs when their surface is exposed to powerful energy fluxes (thermal, shock-wave, radiation, and other extreme loads).

Структурные особенности и технология получения легких броневых композиционных материалов с механизмом локализации хрупких трещин

Introduction. Monometallic armor traditionally used in military and special equipment armaments has a number of key disadvantages that have a significant impact on the tactical and technical characteristics of the products, namely, significant weight and thickness. At the same time, composite non-metallic armors, which have been widely used recently as an alternative, in turn, are not able to withstand multiple hits in local areas of the structure due to its complete destruction or delamination. The purpose of the work: to develop the technology of obtaining a new class of multilayer metal armor materials based on light metals and alloys by explosive welding, combining high indicators of bullet resistance and structural strength along with low specific gravity. The work presents a new scheme for reinforcing the composite using explosive welding technology, which allows localizing the development of brittle cracks along interlayer boundaries with external ballistic impact on the object. Results and discussion. Reinforced composite material based on titanium and aluminum alloys is obtained by explosive welding. Rational modes of shock-wave loading, which ensure production of composite material of required quality are determined; evaluation of strength of composite is carried out. In order to improve the tactical and technical characteristics of the composite, it was proposed to form high-solid intermetallic layers in its structure due to heat treatment. Rational modes of high-temperature annealing are defined, which ensure formation of intermetallic layers of preset thickness in composite structure. The phase composition of intermetallic pro-layers is studied. Structural features of the composite material are investigated. Mechanism of brittle cracks localization in composite structure at ballistic impact on it is described.

Dynamic response of CFRP-lattice sandwich structures subjected to underwater shock wave loading

Carbon fiber reinforced composites (CFRP) and porous lattice structures possess the advantages of high specific strength and outstanding energy absorption efficiency. However, the structures combining their merits for underwater explosion protection receives little attention, and the underlying mechanics are still not clear. In this work, a CFRP-lattice sandwich structure is proposed, and its responses subjected to the underwater shock wave loading is studied via the finite element code ABAQUS/Explicit. The numerical results are first validated by the existing experiments (Huang et al., 2016), and the influences of the geometrical and load factors on the deformation modes and energy absorption performances are further explored. Results shows that with the variation of the load intensity and structural configuration, the failure modes of the plates can be mainly divided into three types. The failure occurs in the middle layer of the metal porous lattice core along the thickness direction. The thickness of the back plate has a greater influence on the overall deformation of the structure than that of the front plate. When the thickness of the back plate increases, the energy absorption of the front plate increases first and then decreases under the condition of a small shock wave load. The impact resistance of composite sandwich structure is the result of the coupling of core layer and plates. The proportion of energy absorption of each layer is affected by the form of structural energy transfer. The work of this paper provides guidance for the design of underwater protective equipment.