Shock Wave Loading Research Articles

Variations in Constitutive Properties of the Fluid Elicit Divergent Vibrational and Pressure Response Under Shock Wave Loading.

We performed a characterization of the shock wave loading on the response of the specimen representing a simplified head model. A polycarbonate cylinder (2-in. outer diameter, wall thickness: 0.06 or 0.12 in.) was filled with two fluids: pure de-ionized water and 40% glycerol in water, which differ only slightly in their constitutive material properties. These two fluids were selected to represent the cerebrospinal fluid and cerebral blood, using their high strain rate viscosity as a primary selection criterion. The model specimen was exposed to a single shock wave with two nominal intensities: 70 and 130 kPa overpressure. The response of the model was measured using three strain gauges and three pressure sensors, one mounted on the front face of the cylinder and two embedded in the cylinder to measure the pressure inside of the fluid. We noted several discriminant characteristics in the collected data, which indicate that the type of fluid is strongly influencing the response. The vibrations of the cylinder walls are strongly correlated with the fluid kind. The similarity analysis via the Pearson coefficient indicated that the pressure waveforms in the fluid are only moderately correlated, and these results were further corroborated by Euclidean distance analysis. Continuous wavelet transform of pressure waveforms revealed that the frequency response is strongly correlated with the properties of the fluid. The observed differences in strain and pressure modalities stem from relatively small differences in the properties of the fluids used in this study.

Dynamics behavior of porous tin under strong shockwave impact

The dynamic fracture and fragmentation of solid materials subjected to shocks have been widely studied for several decades. Motivations for investigating shock-induced damage behavior are both practical and scientific. In many cases, the loading conditions are two or more continuous shockwaves, causing complex dynamic behavior. Understanding the complex dynamics of metal materials under multiple strong shockwave loadings is important for inertial confinement fusion and impact protection. Under multiple shockwave loadings, the shockwaves not only interact with the material, but also cause interactions among the particles in the porous structure produced by the first impact. These complex dynamics might be revealed by studying the impact response of metals with a clear three-dimensional pore distribution. In this study, experiments were performed on three kinds of porous tin with typical dimensions (millimeters, sub-millimeters, and micrometers) and a clear initial structure. The dynamic behaviors of the porous tins under a 10 GPa-order shockwave loading were characterized by X-ray images, high-speed photography, and photon Doppler velocimetry. The porous tin was not completely compacted after the shockwave, and many particles were ejected at velocities far exceeding the theoretical free-surface velocity. The post-shockwave material density and status of the high-speed ejection were closely related to the initial structure of the porous tin. The distribution characteristics of the material after the shockwave, and the generation mechanism of the high-speed jets, were determined in numerical simulations. After the shock loading, the surface spray was ejected at high speed and the particles inside the porous stucture collided with each other, also at high speed. The particle collisions in the porous structure contributed significantly to the high-speed ejections and the distribution of material density. This study is significant for understanding the dynamic responses of metal materials under multiple shockwave loadings.

Experimental Research on the Influence of Different Curved Rigid Boundaries on Electric Spark Bubbles.

It is well known that the bubble dynamics and load characteristics of cavitation bubbles depend to a great extent on their proximity to the boundary. The purpose of this study is to explore the relationship between the boundary curvature and bubble dynamics, as well as the load characteristics, and summarize the relevant change laws. This study takes three hemispheres of different curvatures and one flat board as its main research boundaries. The hemisphere was chosen as the curved surface boundary because the hemisphere represents the simplest type of curved surface boundary. This method allowed us to easily observe the experimental results and summarize the change laws of bubble dynamics and load characteristics. A high voltage electricity of 400 V was used to produce stable and repeatable electric spark bubbles in this experiment. Since the pulsation time of the bubbles is very short, we used a high-speed camera to acquire the necessary photographs. We also used a Hopkinson bar (HPB) to measure the bubble collapse load. Suppose that the dimensionless parameter of curvature is ζ and the dimensionless parameter of the explosion distance is γ. By summarizing the 44 groups of the experimental results under different combinations of ζ and γ, we found that the cavitation bubble dynamics and loading characteristics are affected by ζ. With an increase of ζ, the shockwave load and bubble collapse load will decrease. In addition, in terms of load characteristics, this study further verified the change trend of the shockwave load and bubble collapse load with γ. For the bubble shrink shape, this paper illustrates the relationship between the bubble’s shrink shape and its shrinkage speed. Four typical bubble shrink shapes are summarized. The effects of different ζ and γ values on the jet are preliminarily explored using the experimental results, and, by considering the experimental results, the developmental trends of the time of the bubble’s first pulsation period are discussed.

Effects of Vibration and TiB2 Additions to the Melt on the Structure and Strain-Rate Sensitive Deformation Behavior of an A356 Alloy

For the first time, joint experiments have been conducted with samples of A356-TiB2 cast aluminum alloy under quasi-static and plane shock-wave loading. Alloys were obtained by introducing TiB2 particles using a master-alloy, combined with the effect of vibration treatment on the melt in order to fragment the dendritic structure and prevent its branching during solidification. The melt treatment and introduction of TiB2 particles allowed the average grain size to reduce to a third of that of the base cast alloy. During the experiments the strain rate and the shock-wave compression pressure were varied. It was shown that introducing particles affected the strain-rate sensitivity of the alloy. The best elastic–plastic and strength characteristics at increased strain rates of over 0.01 s−1 were demonstrated by an A356 alloy without TiB2 particles.

Damage evolution and spall failure in copper under complex shockwave loading conditions

The damage evolution and spall behavior of copper under complex shockwave loading conditions were investigated using plate impact experiments with conical targets. Sweeping tensile waves were generated by the interaction of the released waves that were reflected from the free surfaces of the impactor and the cone surface. From the free-surface velocity profiles measured by multi-channel velocimetry, the classic pull-back spall signals were observed in incipient and complete spallation experiments. The spall strength estimated from the pull-back velocity strongly depended on the loading path and the loading wave profile. Post-experiment analysis based on the soft-recovery technique revealed that the damage distributions were very different from the bottom to the top of the conical target, but the corresponding free-surface velocity data measured at different locations suggested that similar responses occurred, which indicated that the spall strength was the critical threshold stress of micro-void nucleation or early growth. The fractography analysis of the fracture surfaces showed that metal micro-spheres were scattered in deep dimples, which indicated that the increase in temperature due to local severe plastic deformation around the voids was important. With the same set of model parameters, the plate impact spallation experiments with plane and conical targets were simulated using a critical damage evolution model. A good agreement was obtained between the simulations and experiments, which demonstrated the model capabilities for predicting the spall responses of metals under complex shockwave loading.

Effect of the Temperature of Shock-Wave Loading on Structure and Phase Transformations in Nitrogen-Containing Austenitic Cr–Mn–Ni Steel

This work has determined the peculiarities of structure and phase transformations at various initial temperatures (–129…548°С) and high deformation rates (448–530 m/s) of shock-wave loading in the austenitic nitrogen-containing steel KH20N6G11M2AFB (0.4N–20Сr–6Ni–11Mn–2Mo–V–Nb). The cyclic γ → e → γ transformation is observed in the course of shock-wave loading at 20–203°С, which causes the phase naklep of austenite and the possible occurrence of the shape memory effect in the regions of deformation localization.

Shockwave dissipation by interface-dominated porous structures

The advent of additive manufacturing (AM) has enabled topological control of structures at the micrometer scale, transforming the properties of polymers for a variety of applications. Examples include tailored mechanical responses, acoustic properties, and thermal properties. Porous polymer materials are a class of materials used for shock and blast mitigation, yet they frequently possess a lack of structural order and are largely developed and evaluated via trial-and-error. Here, we demonstrate control of shockwave dissipation through interface-dominated structures prepared by AM using 2-photon polymerization. A fractal structure with voids, or free surfaces, arranged less than 100 μm apart, allows for rarefaction interactions on the timescale of the shockwave loading. Simulations and dynamic x-ray phase contrast imaging experiments show that fractal structures with interfaces assembled within a “critical” volume reduce shockwave stress and wave velocity by over an order of magnitude within the first unit cell.

Safety evaluations of a large-scale facility under blast loading

In this work, the safety performance and loading behavior of a large-scale facility were studied using experimental observations, numerical simulations and theoretical calculations. Furthermore, the effects of concentration, pressure relief and volume on the shock wave loadings were investigated. In particular, based on the dimensional theoretical analysis, a model for the analysis of overpressure peak and impulse for such facilities was proposed. The results showed that if concentration was larger than 10.5 %, the peak overpressure and the maximum overpressure rate were decreased; if the ignition mode was chemical, the propagation speed of flame was increased. In addition, it was found that the overpressure was the largest if the concentration was 9.5 %, and with the increase of the distance from the ignition source, the overpressure peak decreased first and then increased. The present study and results can therefore provide the loading information to enhance the antiexplosion performance of such facilities, which is very promising for the future safety evaluations and fault diagnosis of buildings, and constructions in various fields, especially, for nuclear power stations.

Failure Probability and Reliability of Hatch Cover of Bulk Carrier Subjected To Lateral Pressure Load

One of the situations that may cause severe damage and even sinking of bulk bulkheads is the destruction of the hatch cover and as a consequence of the ship's waterlogging. This destruction may be due to heavy loads on the page, such as shock wave loads. Considering this, it is very important to investigate the possibility of structural failure in this situation. In this paper, using a MATLAB programming language developed for the FORM method, we have tried to summarize the reliability analysis on two models of bulk carrier storage models. To achieve this, first, the algorithm of the method of expression, and then the limit state function of this failure state and its components are described, then the probability of failure of these two models of the storage compartment is calculated.

Spall Characterization in Epoxy Via Laser Spallation

Background: The strength of materials under extreme dynamic loading conditions, such as in the case of shock wave loading, is assessed from their spallation characteristics. Under laboratory conditions, flyer plate impact, or sometimes laser-induced stress waves, is employed to instigate spall in a material. These methods are often combined with velocity interferometer system for any reflector (VISAR) technique for performing transient measurements. Although the VISAR can record the velocity of extremely fast-moving surfaces, it requires a complex optical setup and a specialized data reduction technique. Objective: In this study, a simpler approach is adopted by extending laser spallation method to determine the spall strength of epoxy, while performing in situ interferometric measurements, directly on top of thick epoxy films. Methods: The glass/epoxy test samples are prepared by transferring an aluminum coating on top of epoxy layers with different thicknesses. Laser-induced stress waves transmit across the substrate/film interface and induce subsurface failure in the epoxy at sufficiently high incident laser energy. The nature and magnitude of the waves are deciphered from the out-of-plane displacement histories of the top reflective sample surfaces, which are recorded by using a Michelson interferometer. Results: The interferometric data reveal the development of two (temporally) well-separated stress waves: an ablation-induced high-amplitude short-duration longitudinal pulse, which is referred to as the primary wave, and a secondary wave, which travels at a comparatively slower speed. The complex constructive interaction of the two waves develops a high-magnitude tensile stress region in the epoxy layer. The spall strength is quantified by superimposing the two stress wave histories associated with the critical energy fluence. Conclusions: The spall depths predicted from spatiotemporal wave travel analyses are in excellent agreement with the experimental observations. The newly adopted methodology estimates the spall strength of epoxy as 260 ± 20 MPa.

Chemical composition and structure of interfacial boundaries in Cr<sub>3</sub>C<sub>2</sub>-Ti powder hard alloys after explosive pressing and subsequent heating

The paper presents the results of studies of the fine structure, chemical and phase composition of boundaries between the components of the Cr 3 C 2 -Ti hard alloy containing 40 wt.% of titanium bond in the state after explosive pressing, as well as after heat treatment. The powder mixture was subjected to shock-wave loading at a heating temperature of 730 °C and pressure of 14 GPa to ensure the maximum compaction and consolidation of the powder mixture without sintering. Compact specimens were heat-treated by heating from 400 to 700 ° С and holding in the oven for 1 hour followed by still air cooling. The equilibrium phase composition was calculated by numerical thermodynamic modeling using Thermo-Calc software. The structure and elemental composition were studied using FEI Quanta 3D and Versa 3D electron microscopes with an integrated focused ion beam system for foil fabrication, as well as FEI Tecnai G2 20F and Titan 80-300 transmission electron microscopes with foil transmission scanning mode. The Bruker D8 Advance diffractometer was used for X-ray phase analysis. It was shown that the formation of strong interfacial boundaries under explosive pressing of titanium and chromium carbide powder mixtures is accompanied by chemical interaction between the components with the formation of boundary layers having a total thickness of about 90 nm. There is a continuous monotonic change in the Cr and Ti content within the transition layer at the almost constant carbon content. The phase composition of layers corresponds to the equilibrium one calculated at the shock-wave compression pressure but it is thermodynamically nonequilibrium under normal conditions. When heated to 400 °C, boundary layers dissolve with the transition of Cr 3 C 2 -Ti hard alloys into a two-phase state. When heated to 700 °C, alternating layers of carbon-depleted chromium carbides (Cr 7 C 3 , Cr 23 C 6 ) and titanium carbide (TiC) form along the interfacial boundaries by carbon diffusion from the original chromium carbide (Cr 3 C 2 ) to titanium.

Texture evolution in nanocrystalline Cu under shock compression

We investigate with large-scale molecular dynamics simulations texture evolution in nanocrystalline Cu under planar shock wave loading. Five representative initial textures are explored under varying impact strengths. On the basis of Euler angles, we perform orientation mapping and texture analysis, including orientation distribution functions, pole figures, and inverse pole figures. Shock compression induces a weak but apparent ⟨110⟩ textures in nanocrystalline Cu initially with no texture, and a ⟨100⟩ fiber texture, and an incomplete weak ⟨110⟩ texture in nanocrystalline Cu initially with a {100}⟨100⟩ recrystallization texture; such texture changes can be attributed to deformation twinning and dislocation slip and traced back to grains initially with ⟨100⟩. A ⟨100⟩ texture and a {100}⟨100⟩ cube texture component are induced via twinning in nanocrystalline Cu initially with the ⟨111⟩ and β fiber textures, respectively, and can be traced back to grains initially with ⟨111⟩.

Three-dimensional modeling and simulations of single-crystal and bi-crystal titanium for high-strain-rate loading conditions

High purity single crystal titanium (Ti) under shock wave loading is modeled under both one-dimensional and three-dimensional cylindrical conditions. Cylinder sizes of 10 μm and 20 μm radius are both considered in order to assess influence of boundary conditions. A thermodynamically consistent single crystal model for application to shock conditions is presented. The model accounts for the coupled non-linear elastic, dislocation slip, deformation twinning, and structural phase transformation response of the titanium material. Plate impact experiment results using a copper flyer are used to compare against the simulations for crystals oriented in [0001] and [101‾1] crystallographic directions. The one-dimensional and three-dimensional simulations of the two differently oriented single crystals indicate differences between the one-dimensional and three-dimensional representation, especially for the [101‾1] oriented single crystal. This orientation breaks the relative orientation symmetry between the crystal and cylinder which otherwise exists for the [0001] oriented single crystal. A significant amount of heterogeneity in the field response of the [101‾1] oriented simulation was demonstrated due to the highly coupled nature of the deformation. A bi-crystal model composed of both the [0001] and [101‾1] orientations with the boundary between the two along the axis of the cylinder is also considered for cylinder model sizes of 10 and 20 μm. The results indicate a strong interaction between the two grains that affects the ω phase volume fraction achieved relative to the single crystal calculations.

Characteristic Study on Gas Blast Loadings in an Urban Utility Tunnel

China is actively building urban utility tunnels and incorporating gas pipes into the tunnels. However, there is a certain risk of leakage and explosion when gas enters the tunnels. If the gas pipe leaks and causes an explosion, this will not only seriously damage the integrated tunnel structure and other pipelines, but also lead to a catastrophic impact on the surrounding buildings. It is therefore necessary to study the safety of urban utility tunnels under gas blast loadings. In the present work, based on a completed gas explosion model, we investigated the blast loading characteristics of a typical utility tunnel to achieve the shock wave propagation law and distributions of the explosion. We also analyzed the effects of gas concentration, pressure relief vent, and gas volume on the shock wave load. By dimensional theoretical analysis, we established a formula for calculating the overpressure peak and impulse for such utility tunnels. The research can therefore provide loading information for the safety assessment and further improve the antiexplosion safety performance of utility tunnels.

Experimental Study and Theoretical Verification of Explosion-Proof Performance of Insulated Glass

Building glass fragment in a blast-related environment is the main cause of casualties. In order to analyze the explosion-proof performance of insulated glass quantitatively in conventional buildings, the explosion experiment under different shock wave loads was carried out on the insulated glass, the pressure sensor was used to collect the overpressure value of the explosion shock wave, and the high-speed camera was used to record the breaking process of glass. The broken state of the insulated glass and the critical overpressure value of the broken state under different working conditions were obtained. And the theoretical calculation method based on the equivalent static load was used to verify the critical overpressure value of the insulated glass. The research showed that the fragments scattered toward the center of the explosion source when the layer of the insulated glass face to the explosion wave front was broken, and the fragments mainly scattered in the direction of the shock wave propagation when it was completely broken. The theoretical calculation method based on the equivalent static load could be used to evaluate the explosion-proof performance of the insulated glass.

Research on piezoelectric pressure sensor for shock wave load measurement

The paper presents piezoelectric pressure sensor to measure the dynamic pressure of explosive shock wave in real time. Crystal group structural layout with acceleration compensation is designed by adding mass blocks. The static and dynamic model of the sensor is established to calculate the sensitivity and natural frequency. The influence of structural parameters of the sensor on its static and dynamic characteristics is analyzed. The mapping relationship between input and output of the sensor under different pressure loads is obtained by simulation. Prototype of the sensor under shock wave load is fabricated. Static and dynamic calibration platforms are built to complete calibration experiments. The experimental results show that the sensor can meet the measurement requirements of high frequency dynamic load signals.

Adhesively bonded joints under quasi-static and shock-wave loadings

Advanced developments in adhesive technology allow adhesive joints to be used in structures that may be subjected to dynamic loads caused by collisions, explosions, or high-velocity impacts. Characterizing adhesive joints under high loading rates is imperative before integrating them into structures that demand crashworthiness and high impact resistance. In this experimental study, an attempt is made to characterize adhesive joints under a moving shock-wave loading using custom designed specimens mounted on a large-scale shock tube and compare the results with quasi-static loading. Both the dynamic and static loading experiments are configured to the same mounting location of the shock tube, using the same instrumentation setup. It is found that failure of adhesive joints takes place at lower pressures in dynamic loadings caused by impacting shock waves compared to the case of quasi-static loadings. The residual strengths of the post-shock specimens are also assessed by performing quasi-static tests. In order to gain more insight into the behavior of the adhesive, an FEM model is developed, and the rate dependency of the adhesive is simulated using Cowper Symonds material model.

Investigation of the Structure and Distribution of Chemical Elements between the Phases of Hard Alloys of the Cr<sub>3</sub>C<sub>2</sub>-Ti System, Obtained at Various Modes of Explosive Compaction

The Article presents the findings of the studies of the microstructure, chemical and phase composition of the Cr3C2-Ti system alloys obtained by the explosion. Scanning electron microscopy, energy dispersive and x-ray diffraction analyses were used. The program Thermo-Calc software was used to calculate the equilibrium phases. The phase composition of the compact was shown to fully correspond to that of the initial powder mixture during explosive pressing in the modes of heating from 300 ̊С to 600 ̊С. When heated above 600 ̊С, the chemical interaction of the initial components begins with the formation of new boundary phases. Meanwhile, there is a change in the sample destruction nature and a significant increase in hardness, which points to the hard alloy consolidation. The increase in the powder mixture heating in shock waves to 1000 ̊С leads to intensive macrochemical interaction of the powder mixture components and to formation of an equilibrium phase composition. The established temperature limits determine the most appropriate parameters of shock-wave loading when producing hard alloys by explosive pressing.

About mechanical behaviour of metal matrix composites under shock wave loading

In this work the results of studying of the mechanical behaviour of metal-ceramic composites with an aluminium matrix on meso-scale level are submitted. Computer simulation of mechanical reaction of representative volume of composite material, considered as ensemble of the interacting structural elements (ceramic particles and metal matrix), is used for studying mechanisms of deformation on meso-scale level of metal-ceramic composites under the loading by shock waves. The mechanical behaviour of aluminium matrix is described by the model of the damaged elastic-plastic medium. The model of the damaged brittle solid is used for ceramics. The absence of macroscopic and mesoscopic voids and cracks in the material before loading is assumed. Ideal adhesion of ceramic material to metal is supposed at the initial condition. The problem is solved in 2D statement with application of finite-difference method. Results of numerical simulation of the mechanical behaviour of metal-ceramic composites under shock wave loading have shown the formation of non-stationary and essentially non-uniform fields of stresses and strains at the meso-scale level. The generation of a dissipative structure on the meso-scale level of the composites under shock wave loading was revealed in the simulations.

Synthesis in SHS-Mixtures by Explosive Loading

The article is devoted to the study of the characteristics of shock-wave processing of powder mixtures capable of an exothermic reaction of the synthesis of metal-ceramic materials. Experiments on shock-wave initiation of synthesis in systems based on Ti-B and Ti-C with 10% and 20% Ni content were carried out. Explosive loading was carried out by oblique throwing of a steel drummer with speeds of 1000 m / s and 1500 m / s. X-ray phase analysis of synthesis products showed the presence of TiB2 diboride and TiC carbide in the nickel bond. The significant role of the mechanical activation of powder mixtures in increasing the sensitivity of SHS-mixtures to shock-wave loading is shown.