Impact Kinetic Energy Research Articles

Flexible and lightweight melamine sponge/MXene/polyborosiloxane (MSMP) hybrid structure for high-performance electromagnetic interference shielding and anti-impact safe-guarding

With the development of electronic devices, human beings are always disturbed by the widespread electromagnetic radiation. Meanwhile, the impact kinetic energy from external object will also cause injuries to precision electronic instrument itself and human body. Herein, a lightweight and flexible Melamine Sponge/MXene/Polyborosiloxane (MSMP) hybrid structure with both anti-impacting and electromagnetic shielding performance is proposed by incorporating conductive Ti3C2TX and polyborosiloxane (PBS) into porous melamine sponge (MS). The nanocomposite shows outstanding energy dissipation ability which can efficaciously degrade the external impact force due to the shear stiffening characteristic. Meanwhile, the nanocomposite presents an excellent electromagnetic interference (EMI) shielding ability with a maximum SET value of 39 dB. Besides, the MSMP displays obvious adhesion property after being cut due to the viscoelastic property and internal supramolecular network of PBS, thus can repeatedly resist the external damage. Finally, a safety sports protective equipment is developed by integrating the MSMP nanocomposite into the common sportswear. Owing to the good integration of safe-guarding performance and EMI shielding properties, the MSMP nanocomposites show high prospective potential in precision electronic instruments and wearable protective equipment.

Improvement of the slotless tubular permanent magnet linear motor with lighter mover mass for punching applications

The slotless tubular permanent magnet linear motor (STPMLM) offers obvious advantages when it is applied to the punching system, such as space saving and controllable impact strength. Herein, the mechanical and electromagnetic coupled differential equations were established to present a comprehensive analysis of the relationship between mover mass and motor performance in the punching system. The travel time of the punching movement was expressed analytically under the condition of the mover obtaining the same impact kinetic energy, and the relationship between the mover mass and the resistive energy consumption in one punching process was also deduced under the same condition. Then the analytical results were validated by a numerical model. The studies show that a lighter mover mass can contribute to less resistive energy consumption and faster dynamic response in the punching applications. Based on that, a STPMLM with special-shaped yoke was designed for lighter mover mass. Moreover, prototype experiments including static thrust characteristic and dynamic performance were conducted. The experimental results proved that the proposed permanent magnet linear motor with special-shaped yoke can improve the dynamic performance and reduce resistive energy consumption while ensuring that the electromagnetic performance is not affected.

Honeycomb core failure mechanism of CFRP/Nomex sandwich panel under multi-angle impact of hail ice

The rudder of an airplane is fabricated as a sandwich panel and can potentially be damaged by hail ice. The dynamic responses of a CFRP/Nomex sandwich panel with barely any visible core damage under multi-angle impact of an ice sphere at various velocities are researched experimentally and by using numerical simulations at the mesoscale. The results show that the honeycomb core represents three types of failure modes: wrinkling, fracture of cell walls, and debonding of cell walls at the interface of two-glued-paper-walls (TGPW) due to resin failure. These failure modes exist at specific impact velocities and angles. This paper proposes a mesoscale numerical modeling method of a honeycomb structure to represent the debonding failure at the TGPW interface. In addition, the mechanical properties of these failures are revealed, as the wrinkling of the cell walls are caused by buckling and the fracture of the cell walls and debonding of the TGPW interface are caused by out-plane and in-plane shearing of cell walls. The results showed that the relationship between the denting and impact kinetic energy under multi-angle impact is linear with respect to the impact angle. The effects of impact angles on the contacting forces on a rigid wall and sandwich panel are presented as the amount of peak impact forces affected by the target material type. However, the intensity of the peak impact forces is rarely affected by the type of the target material. The peak impact force of nonvertical impact is greater than that of the normal impact when the normal components of the impact velocities are the same. This is because the impact angle affects the distribution of ice scatter fragments during the impact, and this generates different pressure distributions on the face sheet of the panel.

Experimental assessment of axial deformation behaviour of aluminium-kevlar composite hybrid bitubular structures

Thin-walled hybrid tubular structures have been received more consideration in recent decades due to their considerable stability between crushing features and light-weight. In this regard, some previous research studies have been focused on deformation characteristics and energy absorbing ability of thin-walled metal-composite tube. Hence, in the present research study, Aluminium-kevlar composite bi-tubular structures are introduced and their corresponding crushing behaviour under quasi-static compressive force is investigated experimentally. A number of tests were performed to compare the crushing mechanism of Aluminium- Kevlar composite bi-tubular structures. The conclusions obtained exposed that better crashworthiness features of Aluminium-kevlar composite tubes with a pentagonal section, were due to the favorable crushing styles occurring during the crushing process. Furthermore, the suggested Aluminium-kevlar composite bi-tubular structures might be applied as impact kinetic energy dissipating components in recently manufactured vehicles.

Characterization of the transition regime between high-velocity and hypervelocity impact: thermal effects and energy partitioning in metals

We propose a theoretical interpretation of penetration data, based on partition mechanisms of the impact kinetic energy for different projectile/target combinations of metals and related alloys of interest in terminal ballistics. It is shown how the regime between the upper bound of high-velocity impact, where material strength and failure are still dominating, and the threshold of purely hydrodynamic behavior is characterized by the progressive phase transformations of projectile and target materials. Thermodynamics, impedance matching, and shock dynamics considerations allow quantifying such velocity boundaries for arbitrary impact configurations. We believe that the identification of such transition regime would support the choice of techniques and strategies in the computational modeling of metals upon impact and guide related experiments and their interpretation in such domains for ballistic applications.

Dynamic load of the carrying structure of an articulated wagon with new draft gear concepts

The article deals with a new draft gear concept proposed by the authors to reduce the dynamic load of wagons in operational modes. The peculiarity of the concept is transformation of the kinetic impact energy into the work of viscous resistance forces when the viscous fluid passes through the throttle openings of the piston. The concept can be introduced for the wagons, in which centre sills of the frames are of closed sections. The mathematic modelling was conducted for the dynamic load of articulated wagons with consideration of the draft gear concept. It was established that the use of the draft gear concept can lower the dynamic load of wagons by about 10 %. The research will encourage engineers to design modern structures of rolling stock units and increase their operational efficiency.

Formation pathways of complex organic molecules: OH• projectile colliding with methanol ice mantle (CH3OH)10

In this article, we simulated the collisions of an OH• projectile impacting on a methanol cluster formed by ten units of methanol to mimic an ice mantle (CH3OH)10. The chemical processes occurring after the impact were studied through Born-Oppenheimer (ab-initio) molecular dynamics. We focus on collisions with initial kinetic impact energy of 10–22 eV, where the richest chemistry happens. We report the formation mechanisms of stable complex organic molecules (COMs) such as methoxymethanol CH3OCH2OH, formic acid HCOOH, formyl radical HCO, formaldehyde H2CO and its elusive HCOH isomer. We show that CH2(OH)2, •CH2OH or +CH2OH are key intermediates to generate H2CO and other COMs. We compare the outcomes using OH• with those using OH− projectiles. These processes are likely relevant to the production of COMs in astrophysical environments. We discuss its formation mechanism and the astrophysical implications of these chemical pathways in star-forming regions.

Ionization probability of sputtered indium atoms under impact of slow highly charged ions

In order to investigate the different role of kinetic and potential projectile energy for secondary ion formation, the authors have measured the ionization probability of indium atoms sputtered from a clean indium surface under irradiation with rare gas (Xeq+) ions of different charge states q at the same kinetic impact energy of 20 keV. In this energy range, the kinetic energy of the projectile is predominantly deposited via nuclear stopping, leading to a collision-dominated sputtering process. The authors find that the ionization probability increases significantly if a highly charged ion is used as a projectile, where the ionization energy becomes comparable to or even exceeds the kinetic energy, indicating that a higher level of electronic substrate excitation induced by the potential energy stored in the projectile can boost the secondary ion formation process. This experimental result is discussed in terms of microscopic model calculations describing the secondary ion formation process. At the same time, the authors observe a significant change of the emission velocity distribution of the sputtered particles, leading to a pronounced low-energy contribution at higher projectile charge states. It is shown that this “potential sputtering” contribution strongly depends on surface chemistry even under conditions where the surface is dynamically cleaned by interleaved 5 keV Ar+ ion bombardment.

Molecular dynamics simulations of single-layer and rotated double-layer graphene sheets under a high velocity impact by fullerene

Molecular dynamics (MD) simulations are employed in this paper to study the behavior of single-layer and rotated double-layer graphene sheets under a high velocity impact. The AIREBO force field is used for MD simulations. Stress wave propagation is investigated, and cone-wave and axial-wave velocities are determined. The coefficient of restitution for the double-layer graphene sheet is calculated at different impact incident angles and velocities. Impact and rebound kinetic energy of projectile under the impact simulation of different rotation angles double-layer graphene sheet is monitored. High cone-wave and axial-wave velocities show that single-layer and double-layer graphene sheets have potential applications in impact protection materials.

Numerical simulations for plates under ice impact based on a concrete constitutive ice model

Polar ships and offshore platforms frequently experience floating ice impacts or iceberg collisions in Arctic region, which may cause permanent deformations of plates, resulting in negative effects on their work performance. The modeling of ice material is critical and difficult point to study the ice-structure interaction. This paper proposes a new ice material model based on a soil and concrete material model (MAT 78) with some user-defined ice material curves applied, to simulate the ice mechanical behavior in an ice-plate impact scenario. Calibration of the proposed ice material model is performed by comparing the pressure-area relationship recommended by the International Organization for Standardization (ISO) rules. Using this proposed ice model, numerical simulations are conducted to study the dynamic behavior of plates under ice impact by using LS-DYNA finite element program. The related model tests were also performed to verify the accuracy of the results calculated by numerical method. Besides, a series of numerical simulations are conducted to investigate the influences of initial ice impact kinetic energy and ice impact momentum on ice-plate impact. The maximum plastic deformations of plate, energy absorption of plate and energy dissipation of ice damage during the ice impact process are studied in these numerical simulations.

Defining patterns in the longitudinal load on a train equipped with the new conceptual couplers

The longitudinal-dynamic load on a railroad train has been studied at its steady motion along the track of a homogeneous profile. A value of the longitudinal loading that a train is exposed to has been established. The calculations were carried out for a train consisting of 40 similar semi-wagons. The magnitude of the longitudinal loading, in this case, is taken to equal 1.2 MN. It is important to note that when increasing the motion speed, as well as the weight of a train, the magnitude of the longitudinal load may exceed the specified value. This contributes to the additional loading on the bearing structures of cars on the train and can cause damage to them. In addition, significant longitudinal-dynamic loads contribute to disrupting the motion stability of cars in the train. In order to reduce the longitudinal-dynamic efforts in the train under operating modes, including braking, it has been proposed to use, instead of a standard automatic coupling device, a conceptual coupler. In this case, the impact's kinetic energy is damped by transforming it into the work of a viscous resistance force. This resistance is created by moving a viscous liquid through the throttle holes of the piston based on the principle of hydraulic damper operation. To substantiate the use of a conceptual coupler, the calculation has been performed based on a method for determining the strength of the coupling device through the imaginary separation of a train into two parts. Taking into consideration a coefficient of the viscous resistance, which is created by the conceptual coupler, the acceleration experienced by a train reached about 0.8 m/s 2 . In other words, the use of a conceptual coupler makes it possible to reduce the longitudinal loading on a train by almost 30 % compared with the standard scheme of interaction between a locomotive and cars. The rod of the conceptual coupler has been estimated for strength. It has been established that the maximum equivalent stresses do not exceed permissible limits. The proposed measures would contribute to the reduction of a dynamic load on a railroad train under the loading modes of operation. The implementation of a given concept could also contribute to bringing down the damage to railroad stock in exploitation

Hypervelocity cratering and disruption of the Northwest Africa 4502 carbonaceous chondrite meteorite: Implications for crater production, catastrophic disruption, momentum transfer and dust production on asteroids

The meteorites provide samples of their asteroidal parent bodies, allowing laboratory measurements of the response of asteroidal material to hypervelocity impacts. The meteorites span a wide range of physical properties, with porosities ranging from near zero to more than 40%, comparable to the range determined for stony asteroids. To investigate the effects of target properties on cratering, impact disruption, momentum transfer and dust production we have begun a series of hypervelocity impact experiments on various types of meteorite targets. In this work whole stones or fragments of the Northwest Africa 4502 (NWA 4502) CV3 carbonaceous chondrite were impacted by 1/16” or 1/8” Al-spheres at speeds ranging from 4.11 to 5.89 ​km/s at the NASA Ames Vertical Gun Range. These samples had a mean porosity of ~2.1% and a mean unconfined compressive strength of ~32.9 ​MPa. Eight hypervelocity disruptions demonstrated that these NWA 4502 targets are less resistant to disruption, i.e., they require less impactor kinetic energy per unit target mass to produce an equivalent disruption, than non-porous terrestrial basalt targets or ordinary chondrite meteorite targets. The threshold collisional specific energy, Q∗D, for these NWA 4502 targets is ~224 ​J/kg, which is significantly lower than the ~1795 ​J/kg value we measured previously for the moderately porous (~6.4%) ordinary chondrite meteorite Northwest Africa 869. This likely results from the numerous cracks crosscutting the NWA 4502 samples. We measured the post-impact momentum of seven NWA 4502 cratering events and found a mean momentum transfer of 3.55 times the momentum of the projectile, showing that the recoil from the crater ejecta significantly exceeded the direct momentum transferred by absorption of the projectile. In two cases we found much higher momentum transfer values (11.72 and 8.95), suggesting these two impactors struck a different material, likely hydrous weathering veins, which fill the cracks, than the other five NWA 4502 cratering impacts. This suggests that hydrous asteroids and comets would experience significantly more recoil from hypervelocity impact than anhydrous targets having similar strength and porosity.

Design and optimisation of a protective device for bridge piers against debris flow impact

In Western China, a large number of bridges are located in debris flow gullies and are exposed to a great risk of damage in case of a geological disaster. To ensure the safety of the bridge and extend its service period, in this study, we propose a modular protective device for bridge piers against the impact of debris flow, especially large boulders. The device is composed of a set of independent modules in the form of a closed-cell aluminium foam-filled composite structure (AFCS) that are set at predetermined spacings and fixed by prestressed steel fasteners. The mechanical behaviour and energy absorption characteristics of five AFCS configurations were evaluated by quasi-static compression testing using both experimental and numerical modelling methods, which produced similar results. The two-layer foam-filled lattice structure AFCS05 exhibited the best comprehensive energy absorption performance, and the effects of the material and geometric parameters on the performance were investigated based on the validated finite element models. A prototype protective device based on the AFCS05 design was attached to a model bridge pier. The dynamic response of the prototype indicated that the device prolonged the impact duration and reduced the largest impact force by 84.89%, and absorbed 81.96% of the impact kinetic energy, which effectively protected the pier. The device design and production can be standardised, making it convenient for installation and on-site repair.

Protection of armoured vehicles against chemical, biological and radiological contamination

The article presents problems related to mechanical protection of vehicles with different add-on armours against chemical, biological and radiological contamination. This applies to vehicles with additional passive, reactive and hybrid protection in the form of cassettes against piercing with anti-tank projectiles, piercing with their kinetic energy of impact, and as a result of chemical energy of shaped charges as well as explosively formed projectiles. It has been shown how increased ballistic protection of these vehicles at the same time reduces their decontaminability in various places of the vehicle due to the increased additional surface of the vehicle with cassettes. Prevention of contamination of these cassettes has been presented as a way of reducing hard to reach surface for decontamination and a method of insulating construction elements (stands), fixing these cassettes to the vehicle, from the environment to prevent contact with contaminated liquids and dusts. The selection of appropriate materials is shown, which may affect the improvement of the decontamination efficiency of the vehicle with such cassettes. This applies to the use of materials with low absorption of chemical warfare agents, which prevent the accumulation of large amounts of these agents on contaminated surfaces and improve the effectiveness of decontamination. It also shows how to ensure better access of the disinfectant to as much of the vehicle surface as possible, covered with cassettes that have been contaminated. It shows how a vehicle, in particular with such cassettes, can provide protection against radar detection when Radar Absorbent Material is used on vehicle cassettes.

Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

AbstractTraditional methods of controlling hard roofs have a limited scope of action and cannot effectively release the strong ground pressure behavior (SGPB) induced by high‐position hard roofs (HHRs) in extra‐thick coal seam mining (ETCSM). Thus, an innovative control technology of fracturing HHRs by vertical‐well stratified fracturing (VWSF) has been proposed. However, the key parameters of VWSF, namely fracturing horizon and fracturing thickness of HHRs, which have a significant influence on stope stability, remain uncertain. In this study, a mechanical model of the “coal wall–hydraulic support–gangue” support system is established by considering the effective loading acting on HHRs, through which modified expressions for the periodic breaking span and impact kinetic energy of the stope are deduced. Based on the self‐bearing of bulking rocks, the stability principle of the surrounding rock, and energy dissipation theories, the criteria for determining the fracturing horizon and thickness of the HHR are obtained. Next, a numerical model of ETCSM, which accounts for the supporting effect of gangue, is constructed in FLAC3D. The support load and energy released by stratum breakage are determined through modeling under various hard roof parameters, thus verifying the correctness of the determination criteria. The results show that the energy released by a hard roof, average support load, and critical support load are positively correlated with thickness, and first increase before declining with respect to an increase in the fracturing horizon. The key parameters for a real coal mine are obtained by theoretical calculations and numerical simulations. A field application demonstrates that the support load and advance roadway deformation can be decreased using the proposed parameterization. This provides theoretical support for determining the key parameters of HHRs for VWSF and facilitates the widespread application of VWSF technology in HHR control.

Residual strength estimation of a laminated composite with barely visible impact damage based on topology optimization

The purpose of this study is to develop an approach to generate reasonably conservative estimations of the residual strength of a composite material with barely visible impact damage (BVID) without directly modeling the dynamic impact process. During an impact, a portion of the impactor kinetic energy transforms into the formation of a microcrack system in the matrix, fiber, and interface, which can be interpreted as material damage. Using the estimated value of energy transformed into damage as a constraint in the mathematical formulation, the optimization algorithm computes the damage distribution to minimize the residual stiffness of the structure as an objective function, which is closely related to the residual strength. Thus, this procedure gives “the worst” possible damage distribution within the material as a conservative estimation of the residual strength of the composite part. The proposed approach is promising for establishing the allowable BVID with fewer experiments.

Mathematical modeling and analysis of energy conversion efficiency of particle jet accelerating nozzle

The impact kinetic energy of particle jet determines rock-breaking effect and velocity, and as acceleration device of particle jet, the energy conversion efficiency of nozzle determines rock-breaking efficiency. According to three different types of nozzles of the straight-taper nozzle, the pressure drop model and energy conversion efficiency of particle jet was established, and the energy conversion efficiency under different type nozzles was studied. And then, the acceleration ability of different nozzles for was analyzed with simulation. The results of model calculation and simulation show that constant-acceleration nozzle has the best acceleration ability and energy conversion efficiency. The rock-breaking experiment was carried out with the adopted nozzle, and comparison analysis between experimental results and numerical calculation prove that the applicability of mathematical model.

A probability prediction model of erosion rate for Ti-6Al-4V on high-speed sand erosion

When a helicopter flies in sand and dust environment or encounters sandy weather, the sand entering the engine compressor can cause severe erosion damage to the blades. This paper aims to deduce an erosion rate prediction model for titanium alloy blade material which can take into account the probability factors such as particle size, velocity and sand fracture. Methods to judge whether sand fractured and quantify the effect of sand fragmentation on erosion damage were obtained. The probability relationship between particle size and mass ratio, impact kinetic energy and fracture rate, particle size range and impact velocity were studied. It is verified that the model can not only adapt to the high-speed erosion conditions, but also adapt to the probability characteristics of many impact factors. The angle of maximum erosion rate under relative high-speed erosion condition is significantly larger than that of under relatively low-speed erosion condition.

Evaluation of breach behavior due to plate fragment impact

This paper presents modifications to existing relationships that analyze the breach potential of concrete elements subjected to impact by plate fragments. Experimental data associated with a previous study that evaluated plate fragment impacts were analyzed to determine the impactor kinetic energy required to cause reinforced concrete to present a breached condition. This value was compared to the energy that the existing contact charge relationships indicate is required to breach a wall of the same thickness. Modifications were made to existing contact charge equations to account for the difference between the contact charge energy required to cause a breach condition and that required from fragment impact to produce a breach condition. A numerical model that simulates concrete slab breach response was also created and utilized to further evaluate the breach relationships. These modified relationships provide the ability to determine the thickness of wall required to prevent a breach due to impact from a plate fragment at varying impact velocities; however, they appear to be less reliable for thinner slabs and are not recommended for low aspect ratio projectiles.

Experimental Pellet Shatter Thresholds and Analysis of Shatter Tube Ejecta for Disruption Mitigation Cryogenic Pellets

Mitigating disruptions is essential for the longevity of future large tokamak experimental devices and reactors. Currently, shattered pellet injection (SPI) technique is the most effective mitigation technique found thus far, and has been chosen for the baseline disruption mitigation (DM) system for ITER. To optimally design SPI systems, the survivability of the pellet throughout the pre-shatter flight and the resulting shatter spray must be better understood. Experimental tests of low-angle single strike impacts of neon and argon pellets were conducted to determine the minimum normal kinetic impact energy that pellets can withstand throughout guide tube travel. Knowing the maximum normal kinetic energy that pellets of relevant materials and temperatures can withstand during flight will allow for an optimal SPI system design. Characterization of the downstream shatter spray was performed for various shatter tube geometries using pure argon and neon pellets. The experimentally measured post-shatter fragment size distribution is compared to theoretical models. The most accurate model found from this comparison is a statistics-based model for brittle material shattering that is correlated with the relevant physical parameters of SPI pellets. Extrapolation of the model to ITER size pellets is presented.