Solid Impactor Research Articles

Plane Strain State of Composite Material Reinforced by Two Rows of Crystalline Fibres in Dynamic Elastic-Plastic Formulation

A generalized approach was developed for solving contact problems in a dynamic elastic-plastic formulation. For the design of composite and reinforced materials, a technique for solving dynamic contact problems in more adequate an elastic-plastic mathematical formulation is used. To consider the physical nonlinearity of the deformation process, the method of successive approximations is used, which makes it possible to reduce the nonlinear problem to a solution of the sequences of linear problems. In contrast to the traditional plane strain, when one normal stress is equal to a certain constant value, for a more accurate description of the deformation of the sample, taking into ac-count the possible increase in longitudinal elongation, we present this normal stress as a function that depends on the parameters that describe the bending of a prismatic body that is in a plain strain state. The problem of a plane strain state of a beam made from the composite reinforced one-layer material is being solved. The reinforced or armed composite material consists of two materials: the main material of glass and two rows of the reinforcing crystalline fourteen fibres of basalt. Glass has high strength and is not affected by the processes of aging of the material, corrosion, and creep. In addition, this material is cheap and widely available. The reinforced composite beam is rigidly linked to an absolutely solid base and on which an absolutely solid impactor acts from above in the centre on a different size of the area of initial contact.

Plane Strain State of Four-Layers Composite Reinforced Body in Dynamic Elastic-Plastic Formulation Authors: Vladislav Bogdanov

The design of composite and reinforced or armed materials is a requirement of the modern level of production and life. In previous works (Bogdanov, 2022; Bogdanov, 2022; Bogdanov, 2022; Bogdanov, 2022), the plane problems of non-stationary interaction of a bullet-type impactor with the upper surface of a composite reinforced two-layers base, which consists of an upper thin layer of steel and a lower main layer of glass, was investigated. It is of interest to study the question of how a composite material composed of several two-layers composite bases laid on top of each other and rigidly bonded to each other will behave. In this work, we study the non-stationary interaction of a striker and a four-layers composite material reinforced with two thin steel layers. The four-layers base is obtained from two identical two-layers bases rigidly linked to each other. Such a four-layer material along its lower surface is rigidly linked to an absolutely hard half-space. The main layers of the material consist of glass. The use of glass in composites is promising due to the fact that glass is a durable, cheap, widespread material that does not corrode, and its strength properties do not degrade as a result of aging, creep like other materials, especially metals. The problem of glass brittleness is overcome by hard contact between the layers. In this case, the tops of micro cracks, micro pores on the surfaces of glass and steel are immobilized and do not propagate into the layers. An absolutely solid impactor acts from above in the centre on a small area of initial contact. The problem of a plane strain state of a beam made from the composite reinforced four layers material is being solved. A technique for solving dynamic contact problems in a dynamic elastic-plastic mathematical formulation is used. To consider the physical nonlinearity of the deformation process, the method of successive approximations is used, which makes it possible to reduce the nonlinear problem to a solution of the sequences of linear problems.

Plane Strain and Stress States of Two-Layer Composite Reinforced Body in Dynamic Elastic-Plastic Formulation

For the design of composite and reinforced materials, a technique for solving dynamic contact problems in more precise an elastic-plastic mathematical formulation is used. To consider the physical nonlinearity of the deformation process, the method of successive approximations is used, which makes it possible to reduce the nonlinear problem to a solution of the sequences of linear problems. In contrast to the traditional plane strain, when one normal stress is equal to a certain constant value, for a more accurate description of the deformation of the sample, taking into account the possible increase in longitudinal elongation, we present this normal stress as a function that depends on the parameters that describe the bending of a prismatic body that is in a plain strain state. The problems of a plane strain and stress states of a beam made from the composite reinforced double-layer material is being solved. The reinforced or armed material consists of two layers: the upper (first) thin layer of solid steel and the lower (second) main layer of glass. Glass is a non-crystalline, often transparent amorphous solid that has widespread practical and technological use in the modern industry. Glass has high strength and is not affected by the processes of aging of the material, corrosion, and creep. In addition, this material is cheap and widely available. Glass can be strengthened, for example, in a melt quenching process. The reinforced composite beam is rigidly linked to an absolutely solid base and on which an absolutely solid impactor acts from above in the centre on a small area of initial contact.

Problem of plane strain state of two-layer body in dynamic elastic-plastic formulation (Part I)

The design of composite and reinforced or armed materials is a requirement of the modern level of production and life. Many methods of calculation and design of such materials are successfully used. In this article, for the design of composite and reinforced materials, a technique for solving dynamic contact problems in more precise an elastic-plastic mathematical formulation is used. To consider the physical nonlinearity of the deformation process, the method of successive approximations is used, which makes it possible to reduce the nonlinear problem to a solution of the sequences of linear problems. In contrast to the traditional plane strain, when one normal stress is equal to a certain constant value, for a more accurate description of the deformation of the sample, taking into account the possible increase in longitudinal elongation, we present this normal stress as a function that depends on the parameters that describe the bending of a prismatic body that is in a plain strain state. The problem of a plane strain state of a beam made from the composite reinforced double-glazed material is being solved. The reinforced or armed material consists of two layers: the upper (first) thin layer of solid steel and the lower (second) main layer of glass. Glass is a non-crystalline, often transparent amorphous solid, that has widespread practical and technological use in the modern industry. The most familiar types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz). Glass has high strength and is not affected by the processes of aging of the material, corrosion, and creep. In addition, this material is cheap and widely available. Glass can be strengthened, for example, in a melt quenching process. If the cooling is fast enough (relative to the characteristic crystallization time), then crystallization is prevented, and instead the disordered atomic configuration of the supercooled liquid is frozen into a solid state. This increases the strength properties of the glass. The reinforced composite beam is rigidly linked to an absolutely solid base and on which an absolutely solid impactor acts from above in the centre on a small area of initial contact.

Simulated Kick Injury to the Mandible in Horses: Study of Fracture Configurations and Physical Parameters of the Impact.

The goal of this study was to generate mandibular fractures in three regions of the diastema using a metal impactor to simulate a kick from a horse and to determine the mean deceleration in the initial phase of the impact event, the maximum contact force, the impact energy necessary to create a fracture and the duration of the impact. Thirty heads of horses aged between 5 and 20 years and euthanatized for various reasons were used. The heads were attached to a steel bar at the occiput at an axial angle of 45 degrees so that the body of the mandible was positioned horizontally and directly under the trajectory of the impactor. A 2 kg solid impactor was dropped with velocities of 6 to 14 m/s to simulate a kick from a horse. The impact was recorded using a high-speed video camera with a frame rate of 30,000 frames per second. Radiographs of the heads were obtained before and after the simulated kick. Mandibular fractures with configurations similar to those seen in clinical practice were generated at all three locations. The mean deceleration increased with impact velocity and with more cranially located impact positions. Absorbed energy increased with increasing impact velocity when no fracture was generated. The susceptibility to experimental fracture of the diastema increased from rostral to caudal locations, which is most probably caused by decreasing mandibular bone strength and an increase in the curvature at the lateroventral aspect of the mandible in that region. Physical parameters depended on fracture occurrence and type.

Introducing pre-impact air-cushioning effects into the Wagner model of impact theory

In this analysis, we consider the effects of non-quiescent initial conditions driven by pre-impact air–water interactions on the classical Wagner model of impact theory. We consider the problem of a rigid, solid impactor moving vertically towards a liquid pool. Prior to impact, viscous forces in the air act to deform the liquid free surface, inducing a flow in the pool. These interactions are then incorporated as initial conditions in the post-impact analysis. We derive expressions for the size of the effective contact set, the leading-order pressure and force on the impactor, and the speed and thickness of the jet at its base. In all cases, we show that the effect of the pre-impact behaviour is to cushion the impactor, reducing the size of the effective contact set and, hence, the force on the impactor. Small- and large-time asymptotic solutions are derived for general power-law impactors, and we show that the effects of the air die away as the impact progresses, so that we approach the classical Wagner solution.

SARS-CoV-2: a systematic review of indoor air sampling for virus detection.

In a post-pandemic scenario, indoor air monitoring may be required seeking to safeguard public health, and therefore well-defined methods, protocols, and equipment play an important role. Considering the COVID-19 pandemic, this manuscript presents a literature review on indoor air sampling methods to detect viruses, especially SARS-CoV-2. The review was conducted using the following online databases: Web of Science, Science Direct, and PubMed, and the Boolean operators “AND” and “OR” to combine the following keywords: air sampler, coronavirus, COVID-19, indoor, and SARS-CoV-2. This review included 25 published papers reporting sampling and detection methods for SARS-CoV-2 in indoor environments. Most of the papers focused on sampling and analysis of viruses in aerosols present in contaminated areas and potential transmission to adjacent areas. Negative results were found in 10 studies, while 15 papers showed positive results in at least one sample. Overall, papers report several sampling devices and methods for SARS-CoV-2 detection, using different approaches for distance, height from the floor, flow rates, and sampled air volumes. Regarding the efficacy of each mechanism as measured by the percentage of investigations with positive samples, the literature review indicates that solid impactors are more effective than liquid impactors, or filters, and the combination of various methods may be recommended. As a final remark, determining the sampling method is not a trivial task, as the samplers and the environment influence the presence and viability of viruses in the samples, and thus a case-by-case assessment is required for the selection of sampling systems.

Spatial Non-Stationary Contact Problem for a Cylindrical Shell And Absolutely Rigid Body

A spatial non-stationary contact problem with moving boundaries of the interaction region for a thin elastic cylindrical shell and an absolutely solid impactor bounded by a smooth convex surface is considered. A closed mathematical formulation is given and a system of resolving equations is constructed. The latter is based on the spatio-temporal integral equation resulting from the principle of superposition and contact conditions. The core of this equation is the influence function for the cylindrical shell. To a closed system of resolving equations, it is supplemented by a kinematic relation for determining the moving boundary of the contact region and the equation of motion of the impactor as an absolutely rigid body. An algorithm for solving the spatial non-stationary contact problem for an infinitely long cylindrical shell and absolutely solid impactor in the case of a normal impact on the side surface of the shell is constructed and implemented. Examples of calculations are given.

Terrestrial magma ocean origin of the Moon

A conceptual framework for the origin of the Moon must explain both the chemical and the mechanical characteristics of the Earth–Moon system to be viable. The classic concept of an oblique giant impact explains the large angular momentum and the lack of a large iron-rich core to the Moon, but in this scenario it is difficult to explain the similarity in the isotopic compositions of the Earth and Moon without violating the angular momentum constraint. Here we propose that a giant, solid impactor hit the proto-Earth while it was covered with a magma ocean, under the conventional collision conditions. We perform density-independent smoothed particle hydrodynamic collision simulations with an equation of state appropriate for molten silicates. These calculations demonstrate that, because of the large difference in shock heating between silicate melts and solids (rocks), a substantial fraction of the ejected, Moon-forming material is derived from the magma ocean, even in a highly oblique collision. We show that this model reconciles the compositional similarities and differences between the Moon and Earth while satisfying the angular momentum constraint. Moon formation by a giant impact ejecting material from a magma ocean on Earth reconciles geochemical and dynamical constraints on its formation, according to numerical simulations.

Peculiarities of Milligram Mass Acceleration in Electromagnetic Railguns with an External Pulsed Magnetic Field

Solid polycarbonate impactors were accelerated in a channel of electromagnetic railgun to which an external pulsed magnetic field was applied. The channel was filled with air at atmospheric pressure. The dynamics of impactor acceleration in the railgun was calculated. The impactor velocities in the railgun muzzle were measured in two cases. In the first case the railgun and external field system were powered from independent energy sources (scheme 1) and in the second case the railgun and external field circuits were connected in series to a common energy source (scheme 2). It was established that the effective coefficient of rail erosion in a 2-mm caliber channel that takes into account only the eroded mass captured by the plasma piston was 1.5–1.7 mg/C, and the eroded mass involved in the motion was comparable with the impactor mass. It was shown that in scheme 1, when the external field system was switched earlier, the impactor was accelerated at a maximum magnetic induction, and the impactor velocity in the channel muzzle exceeded 6 km/s.

Cryo-braking using penetrators for enhanced capabilities for the potential landing of payloads on icy solar system objects

The icy moons of Jupiter and Saturn are important astrobiology targets. Access to the surface of these worlds is made difficult by the high ΔV requirements which is typically in the hypervelocity range. Passive braking systems cannot be used due to the lack of an atmosphere, and active braking by rockets significantly adds to the missions costs. This paper demonstrates that a two-stage landing system can overcome these problems and provide significant improvements in the payload fraction that can be landed The first stage involves a hypervelocity impactor which is designed to penetrate to a depth of a few tens of meters. This interaction is the cryo-breaking component and is examined through laboratory experiments, empirical relations and modeling. The resultant ice-particle cloud creates a transient artificial atmosphere that can be used to enable passive braking of the second stage payload dd, with a substantially higher mass payload fraction than possible with a rocket landing system.It is shown that a hollow cylinder design for the impactor can more efficiently eject the material upwards in a solid cone of ice particles relative to solid impactors such as spheres or spikes. The ejected mass is shown to be of the order of 103 to 104 times the mass of the impactor. The modeling indicates that a 10 kg payload with a braking system of 3 m2 (i.e. an areal density of 0.3 kg/m2) is sufficient to allow the landing of the payload with the deceleration limited to less than 2000 g's. Modern electronics can withstand this deceleration and as such the system provides an important alternative to landing payloads on icy solar system objects.

Collisional model of energy dissipation in three-dimensional granular impact

We study the dynamic process occurring when a granular assembly is displaced by a solid impactor. The momentum transfer from the impactor to the target is shown to occur through sporadic, normal collisions of high force carrying grains at the intruder surface. We therefore describe the stopping force of the impact through a collisional-based model. To verify the model in impact experiments, we determine the forces acting on an intruder decelerating through a dense granular medium by using high-speed imaging of its trajectory. By varying the intruder shape and granular target, intruder-grain interactions are inferred from the consequent path. As a result, we connect the drag to the effect of intruder shape and grain density based on a proposed collisional model.

Shock-induced ejecta from a layer of spherical particles. Part II: modeling with the non-equilibrium two-phase model of a granular medium

In this work we consider the problem of high-velocity impact of a solid impactor on the layer of spherical solid particles. The impact initiates a wave-type process of compaction of particles in the layer, and the ejection of small solid particles from the compacted layer surface to the air. The first part of the paper addresses modelling the process of particle compaction and the initial stage of solid ejection with the SPH method. In the second part presented below, we consider the process of compaction and solid mass ejection using a new non-equilibrium two-phase model of the granular medium. This model makes it possible to describe mechanics of two-phase gas-solid medium in a wide range of the phase volume fraction, from regimes of isolated particle flows to regimes of dense packed particles.

On peculiarities of near-threshold initiation of powder density explosive by air shock wave and by solid impactor

The features of near-threshold mode of initiating by gas-tight piston and high- enthalpy gas flow was evaluated for a powder density explosive PETN. Both methods lead to the development of detonation in about 10 μs time. The synchrotron radiation diagnostics have shown that the initial stages of the process were significantly different, that diversity being caused by the influence of the gas flow in the pores of the charge. In this work, the effect of the gas flow on the mode of initiation was studied experimentally.

Impact-driven ejection of micro metal droplets on-demand

On-demand metal droplet deposition will be a cornerstone technology in 3D metal printing. However, suitable small nozzles are hardly available, limiting the resolution and surface finish of final products. Here, the ejection of record-small metal droplets with a diameter of only 0.55±0.07 times the nozzle diameter was demonstrated. To this end, a novel metal drop-on-demand (DoD) generator for high-temperature metal processing was designed and manufactured. A metal rod was utilized to transfer a vibration pulse, which was required to eject a liquid droplet, from a low-temperature region to the high-temperature liquid metal close to the nozzle. The influence of the pulse characteristics on the droplet ejection regime was studied experimentally and numerically. A 2D axisymmetric numerical model revealed that the shorter pulses allow reducing the droplet size, with the pulse duration of 13μs resulting in the smallest feasible droplets. A novel method to create such short pulses, by impacting the metal-ring connected rod with a solid impactor was manufactured and tested, and the benefits of this method over more the spring-type pulse transfer was experimentally confirmed. This research provides a feasible way to achieve ejection of the small metal droplet on-demand.

Heating and Melting in Impacts: Basic Theory and Possible Applications

Mutual collisions and impacts of solids occur in systems of widely different scales. The aim of this paper is to present a calculation of the change of temperature which a solid target undergoes when hit by a solid impactor. As a test, the equations derived are applied to examples of laboratory experimental data, and the results are physically plausible.

On a high-velocity annular impactor

Results of interaction of a high-velocity annular steel impactor with a flat steel plate are reported. An annular crater is formed on the frontal surface of the plate. On the backward surface of the plate, the material is spalled in the form of a solid quasi-disk whose diameter is almost twice the outer diameter of the annular impactor. This observations shows that annular impactors are more hazardous than solid impactors (with an identical velocity and outer diameter).

Asymmetric shock heating and the terrestrial magma ocean origin of the Moon

One of the difficulties of the current giant impact model for the origin of the Moon is to explain the marked similarity in the isotopic compositions and the substantial differences in the major element chemistry. Physics of shock heating is analyzed to show that the degree of heating is asymmetric between the impactor and the target, if the target (the proto-Earth) had a magma-ocean but the impactor did not. The magma ocean is heated much more than the solid impactor and the vapor-rich jets come mainly from the magma-ocean from which the Moon might have been formed. In this scenario, the similarity and differences in the composition between the Moon and Earth would be explained as a natural consequence of a collision in the later stage of planetary formation. Including the asymmetry in shock heating is the first step toward explaining the chemical composition of the Moon.

Stardust interstellar dust calibration: Hydrocode modeling of impacts on Al‐1100 foil at velocities up to 300 km s−1 and validation with experimental data

Abstract– We present initial results from hydrocode modeling of impacts on Al‐1100 foils, undertaken to aid the interstellar preliminary examination (ISPE) phase for the NASA Stardust mission interstellar dust collector tray. We used Ansys’ AUTODYN to model impacts of micrometer‐scale, and smaller projectiles onto Stardust foil (100 μm thick Al‐1100) at velocities up to 300 km s−1. It is thought that impacts onto the interstellar dust collector foils may have been made by a combination of interstellar dust particles (ISP), interplanetary dust particles (IDP) on comet, and asteroid derived orbits, β micrometeoroids, nanometer dust in the solar wind, and spacecraft derived secondary ejecta. The characteristic velocity of the potential impactors thus ranges from <<1 to a few km s−1 (secondary ejecta), approximately 4–25 km s−1 for ISP and IDP, up to hundreds of km s−1 for the nanoscale dust reported by Meyer‐Vernet et al. (2009). There are currently no extensive experimental calibrations for the higher velocity conditions, and the main focus of this work was therefore to use hydrocode models to investigate the morphometry of impact craters, as a means to determine an approximate impactor speed, and thus origin. The model was validated against existing experimental data for impact speeds up to approximately 30 km s−1 for particles ranging in density from 2.4 kg m−3 (glass) to 7.8 kg m−3 (iron). Interpolation equations are given to predict the crater depth and diameter for a solid impactor with any diameter between 100 nm and 4 μm and density between 2.4 and 7.8 kg m−3.

Molecular comparison of the sampling efficiency of four types of airborne bacterial samplers

In the present study, indoor and outdoor air samples were collected using four types of air samplers often used for airborne bacterial sampling. These air samplers included two solid impactors (BioStage and RCS), one liquid impinger (BioSampler), and one filter sampler with two kinds of filters (a gelatin and a cellulose acetate filter). The collected air samples were further processed to analyze the diversity and abundance of culturable bacteria and total bacteria through standard culture techniques, denaturing gradient gel electrophoresis (DGGE) fingerprinting and quantitative polymerase chain reaction (qPCR) analysis.The DGGE analysis indicated that the air samples collected using the BioStage and RCS samplers have higher culturable bacterial diversity, whereas the samples collected using the BioSampler and the cellulose acetate filter sampler have higher total bacterial diversity. To obtain more information on the sampled bacteria, some gel bands were excised and sequenced. In terms of sampling efficiency, results from the qPCR tests indicated that the collected total bacterial concentration was higher in samples collected using the BioSampler and the cellulose acetate filter sampler.In conclusion, the sampling bias and efficiency of four kinds of air sampling systems were compared in the present study and the two solid impactors were concluded to be comparatively efficient for culturable bacterial sampling, whereas the liquid impactor and the cellulose acetate filter sampler were efficient for total bacterial sampling.