Ballistic Effects Research Articles

Bio-inspired helicoidal hemp/basalt/polyurethane rubber bio-composites: Experimental, numerical and analytical ballistic impact study with residual velocity prediction using artificial neural network

Recent body armour trends emphasize mobility, flexibility, and cost reduction while maintaining ballistic effectiveness through the use of natural fiber composite. This study evaluates the ballistic impact performance of soft and hard armor using experimental, analytical, numerical, and machine learning methods. We developed a soft armor bio-composite using monolithic, hybrid, and helicoidal structured Hemp (H)/Basalt (B)/Polyurethane (PU) rubber and tested its V50 ballistic limit according to Millitary-Standred-662 F. For hard armour, a multi-layer armor system (MAS) consisting of Al2O3/SiC ceramic, intermediate soft armour bio-composites, and an Aluminum (Al)-5052 plate backing was tested with armour-piercing bullets as per National Institute of Justice (NIJ)-0101.06 standards (Level IV). Soft armor performance was evaluated using macro-homogeneous finite element (FE), the Ipson-Retch analytical, and an Artificial Neural Network (ANN) regression model. Results showed minimal discrepancies from experimental data, with differences of 13.33 %, 12.08 %, and 8.08 % in V50 ballistic limit. The mechanical and thermal behaviors of bio-composites were assessed using un-notched Charpy, FTIR, and TGA methods. Helicoidal laminates improved Charpy toughness by 9.44 %, 19.30 %, and 40.28 % compared to hybrid and monolithic ([H]15 and [H]10) laminates, and exhibited lower weight reduction at high degradation temperature of 395.76 ℃. Helicoidal laminates increased V50 ballistic performance by 155.80 %, 76.22 %, and 16.61 % compared to [H]10, [H]15, and hybrid laminates, respectively. Due to spiral load distribution reduces stress concentration and enhanced the damage resistance of the laminate. Stand-alone soft armor demonstrates crater formation and radial cracks (petaling) due to fiber wedging and the shearing effect of a bullet. In conclusion, MAS revels a maximum back face deformation (BFD) of 18.06 mm. Al2O3/Helicoidal/Al-plate MAS reduced weight and cost by 69.21 %, and 233.72 % compared to Kevlar™-based MAS, promoting sustainable, lightweight, economical designs. Due to its higher fracture toughness and lower density, SiC ceramic in MAS provides lower trauma and further reduced weight compared to Al2O3 ceramic.

A modified bond-based peridynamic approach for rigid projectile perforation on concrete slabs

Peridynamic (PD) has a unique advantage in describing the crack growth and fragmentation of brittle materials. Concerning the dynamic behaviors and failure patterns of concrete slabs under projectile perforations, a modified bond-based PD approach maintaining both the easy implementation and computational stability characteristics was firstly developed from the following three aspects, (i) a rate-dependent PD constitutive model was proposed for describing the dynamic behaviors of concrete; (ii) a progressive damage criterion considering the tension-compression anisotropy, softening behavior, and strain rate effect of concrete was incorporated to more accurately reproduce the damage and failure of concrete; (iii) an improved micro-modulus function related to bond length was introduced to reveal the internal length effect of bond force. Then, numerical simulations of projectile perforation on concrete slabs by utilizing the developed modified bond-based PD approach, as well as the corresponding sensitivity analyses of discretization parameters including horizon size and particle spacing were performed. Based on the recommended horizon size and particle spacing, the predicted residual velocity of projectile and failure patterns of concrete slabs exhibited an excellent agreement with the test data. Furthermore, by comparisons of the traditional bond-based PD and classical finite element methods, the superiority of developed approach in describing the perforation damage of concrete targets against projectile impact was demonstrated. Finally, the modified bond-based PD approach was employed to blind simulate the projectile normal and oblique perforating multi-layered spaced concrete target plates. It was found that the modified PD model reasonably predicted the terminal ballistic trajectory, deflection angle, and residual velocity of projectile, as well as the failure patterns of target plates. The present work provides a new way to predict the terminal ballistic effect of projectile and dynamic behaviors of concrete slabs.

Anisotropy in AISI 316L produced by Binder Jetting 3D printing: Sintering shrinkage and thermal conductivity

The inhomogeneous particle packing in green parts manufactured by Binder Jetting 3D printing is responsible for the anisotropy in several phenomena and properties. In this work, the anisotropy of the sintering shrinkage and of thermal conductivity of AISI 316L green specimens is investigated. Shrinkage was investigated by dilatometry. Moreover, the dimensional changes, density, and the thermal conductivity of specimens sintered at intermediate temperatures were measured. The microstructure of the specimens was analysed with the standard metallographic. Sintering shrinkage is basically isotropic during the heating step and becomes anisotropic on approaching the sintering temperature at 1370°C when the full density is achieved. A slight anisotropy in the building plane is observed. Contrarily, thermal conductivity is anisotropic during the heating step and becomes isotropic during the isothermal holding at the sintering temperature. Moreover, there is an inverse relationship between thermal conductivity in the debinded specimen and shrinkage. A hypothesis for this indirect correlation is proposed. The role of the large interlayer pores and the aligned pores caused by the ballistic effect of the binder jet is confirmed.

Thermal Spreading Resistance of Near Surface Localized Heating-Induced Size Effects in Semiconductors

Abstract Localized heating is encountered in various scenarios, including the operation of transistors, light-emitting diodes, and some thermal spectroscopy techniques. When localized heating occurs on a scale comparable to the mean free path of the dominant energy carriers, additional thermal resistance is observed due to ballistic effects. The main objective of this study is to find a relation between this resistance, problem geometry, and material thermal properties in situations involving localized heating. Models based on the solution of the Fourier heat diffusion equation and the gray phonon Boltzmann Transport Equation are solved simultaneously to calculate the additional thermal resistances that arise from localized heating. Subsequently, the results are analyzed to derive the desired relationship. It is noted that in the context of localized heating resistance, the effects of geometrical variables are non-linear and substantial, particularly when the Knudsen numbers for the boundary and heat source exceed certain thresholds. Specifically, when the Knudsen number for the heat source becomes comparable to 1 localized heating resistance is observed. However, when the Knudsen number based on heat source height and width surpasses 8 and 20, respectively the heat source behaves akin to a point source, no longer significantly affecting the localized heating resistance. At this juncture, the maximum resistance limit is reached.

Rectification of heat current in Corbino geometry.

We prove analytically the ballistic thermal rectification effect (BTRE) in the Corbino disk characterized by an annular shape. We derive the thermal rectification efficiency (RE) and show that it can be expressed as the product of two independent functions, the first dependent on the temperatures of the heat baths and the second on the system's geometry. It follows that a perfect BTRE can be reached with the increase of the ratios of the heat baths' temperatures and of the radius of the outer edge to the inner edge of the disk. We also show that, by introducing a potential barrier into the Corbino disk, the RE can be greatly improved. Quite remarkably, by an appropriate choice of parameters, the thermal diode effect can be reversed. Our results are robust under variation of the Corbino geometry, which may provide a flexible route to manipulate the heat flow at the nanoscale.

Effect of structural disorder induced by external irradiation with heavy ions on the alteration of a four oxide borosilicate glass

The irradiation of glass by heavy ions induces structural damage, generally leading to a decrease in its chemical durability whose amplitude strongly depends on the glass chemical composition. Here, we investigate the effects of irradiation by 7 MeV Au ions (simulating the main ballistic effects induced by self-irradiation in nuclear glass) on the behavior of a 4-oxide borosilicate glass in both the initial and residual dissolution regimes. The comparison between irradiated and non-irradiated glasses provides insights into the predominant atomic mechanisms governing glass alteration processes. The most pronounced effect is observed on interdiffusion in acidic conditions, with the rate increased by more than an order of magnitude for the irradiated glass. We show that both the interdiffusion regime and the residual regime are controlled by the hydrolysis of the B—O—Si linkages, whereas under initial dissolution rate regime in basic conditions the rate-limiting step becomes the hydrolysis of Si—O—Si linkages. Overall, the observations suggest structural disorder due to external irradiation by Au ions primarily affects the kinetics of glass alteration without changing the fundamental nature of the limiting reactions.

Effects of ballistic transport on the thermal resistance and temperature profile in nanowires

Effects of ballistic transport on the temperature profiles and thermal resistance in nanowires are studied. Computer simulations of nanowires between a heat source and a heat sink have shown that in the middle of such wires the temperature gradient is reduced compared to Fourier’s law with steep gradients close to the heat source and sink. In this work, results from molecular dynamics and phonon Monte Carlo simulations of the heat transport in nanowires are compared to a radiator model which predicts a reduced gradient with discrete jumps at the wire ends. The comparison shows that for wires longer than the typical mean free path of phonons the radiator model is able to account for ballistic transport effects. The steep gradients at the wire ends are then continuous manifestations of the discrete jumps in the model.Graphical abstract

A novel ballistic model for the subthreshold behavior of nanosheet transistors

A novel ballistic model for the subthreshold current of nanosheet transistors is successfully developed based on the Landauer approach with the three-dimensional number of channels. The ballistic threshold voltage can also be achieved through the calculated free charge density induced by the three-dimensional density-of-states equal to the substrate doping concentration. It indicates that under the low drain voltage corresponding to the Fermi distribution function, the subthreshold current is mainly governed by the low contact potential. However, under the high drain voltage corresponding to the Fermi distribution function, the thermal voltage, instead of the contact potential between the source and drain, initiates the subthreshold current. Besides subthreshold current and threshold voltage, the ballistic conductance and subthreshold swing are also revealed in the subthreshold conduction. It indicates that the thin silicon, thin gate oxide, heavy substrate doping density, and high work function will alleviate the ballistic effects, decrease the subthreshold current/swing, and increase the threshold voltage/ballistic resistance.

Electron–phonon coupling and non-equilibrium thermal conduction in ultra-fast heating systems

A discrete unified gas kinetic scheme is developed to solve the Boltzmann transport equation (BTE) with coupled electron and phonon thermal transport, whose time step is not limited by the relaxation time. The key of the present scheme is that the electron/phonon advection, scattering and electron–phonon interactions are coupled together within one time step by solving the BTE again at the cell interface. Numerical results show that the present scheme can correctly predict the electron–phonon coupling effects, and is in agreement with typical two-temperature model and experimental results in existing literatures and our performed time-domain thermoreflectance technique. It can also capture the ballistic effects when the characteristic length is comparable to or smaller than the mean free path where the two-temperature model fails. In addition, two anomalous heat conduction phenomena are predicted by the present scheme, namely, heat flows from phonon to electron in transient thermal grating geometry and re-rise reflected signal appears in Au/Pt bilayer metal structure. The present work can provide theoretical guidance for the study of electron–phonon coupling and offer a useful tool for multi-scale thermal management.

Damage Behaviors of Thin and Thick Laminated Composites Under Ballistic Effect

Damage Behaviors of Thin and Thick Laminated Composites Under Ballistic Effect

Abrupt intensification of AMOC and monsoonal winds during mid-MIS4 (Heinrich Event 6) in the western Arabian Sea

In the Arabian Sea (AS), higher organic matter preservation and biological productivity are observed during the summer due to strong southwest monsoonal winds. Centennial and millennial-scale fluctuation in the geochemical and relative abundance of foraminifera species are widely used to study the past preservation and productivity variation reconstruction in the Western Arabian Sea (WAS). The sediment records from the AS also show similarities with the North Atlantic and Greenland mainly during Heinrich events (HEs) which is related to the atmospheric and oceanic teleconnections of the AS with the higher latitude climate perturbations. In this context, we used a sediment core VM3504-PC from the WAS to understand the long-term changes in productivity and organic matter preservation using Globigerina bulloides (G. bulloides) relative abundance, total organic carbon (TOC) content, and calcium carbonate (CaCO3) wt%. The TOC and G. bulloides shows a positive correlation, while significantly negative correlation is recorded in the TOC % and CaCO3 wt% datasets during interglacial periods (MIS5e-b, MIS3, and MIS1). Our results show evidence of CaCO3 dissolution and intense summer monsoon induced upwelling related productivity in core location during interglacial periods (MIS5e), based on higher relative abundance of G. bulloides (%), higher TOC content, and lower CaCO3 wt%. Interestingly, higher preservation of organic matter and increased productivity/nutrient concentration during mid-MIS4 suggesting stronger upwelling/winter convective mixing together with higher aeolian transport from adjacent landmasses. The abrupt weakening in the Atlantic Meridional Overturning Circulation (AMOC) synchronized with low productivity due to weak monsoon during HEs except for H6 and H4 in the tropical Indian Ocean. The H6 coincides with mid-MIS4 is showing abnormal preservation. Thus, AMOC and the summer monsoon significantly regulate primary productivity in the WAS. It is interesting to note that possibly well‑oxygenated deep-water masses do not penetrate up to surface water and/or ballistic effect (indicated by moderate sedimentation rate), preventing organic matter degradation on the seafloor during mid-MIS4.

Compact Spice Models for Terafets

Field effect transistors (FETs) in plasmonic regimes of operation could detect terahertz (THz) radiation and operate as THz interferometers, spectrometers, frequency-to-digital converters and THz modulators and sources. We report on the development of compact models for Si MOS (Metal-Oxide-semiconductor) and heterostructure-based plasmonic FETs (or TeraFETs) suitable for circuit design in the THz range and based on the multi-segment unified charge control model. This model accounts for the electron inertia effect (by incorporating segmented Drude inductances), for the ballistic field effect mobility, which is proportional to the channel length, for parasitic resistances and capacitances and for the leakage current. It is validated by comparison with experimental data and TCAD simulation results. The model can be used for simulation and optimization of sub-THz and THz detectors. Our simulations use up to 200 segments in the device channel. The results are also in good qualitative agreement with the hydrodynamic simulations. Applications of our model could dramatically reduce astronomical design costs of nanoscale VLSI reaching US$1.5 billion for the 3 nm technological node.

Two-temperature principle for evaluating electrothermal performance of GaN HEMTs

Self-heating effects in Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) can adversely impact both device reliability and electrical performance. Despite this, a holistic understanding of the relationship among heat transport mechanisms, device reliability, and degradation of electrical performance has yet to be established. This Letter presents an in-depth analysis of self-heating effects in GaN HEMTs using technology computer-aided design and phonon Monte Carlo simulations. We examine the differential behaviors of the maximum channel temperature (Tmax) and the equivalent channel temperature (Teq) in response to non-Fourier heat spreading processes, highlighting their respective dependencies on bias conditions and phonon ballistic effects. Our study reveals that Tmax, a crucial metric for device reliability, is highly sensitive to both heat source-related and cross-plane ballistic effects, especially in the saturation regime. In contrast, Teq, which correlates with drain current degradation, shows minimal bias dependence and is predominantly influenced by the cross-plane ballistic effect. These findings emphasize the importance of optimizing device designs to mitigate both Tmax and Teq, with a particular focus on thermal designs influenced by the heat source size. This work contributes to a deeper understanding of self-heating phenomena in GaN HEMTs and provides valuable insights for enhancing device performance and reliability.

Ballistic Thermoelectricity

The analysis of Local thermo-EMF in p-n junctions made it possible to reveal the phenomenological features of ballistic thermoelectricity. By the Curie Symmetry Principle, in polar structures of p-n junctions, the thickness of which is of the order of the electron mean free path, the contribution of ballistic effects to the formation of the total EMF is decisive. This ballistic contribution to thermo-EMF provides both high output voltages and high efficiency of DIRECT energy conversion.

Topology optimization for near-junction thermal spreading of electronics in ballistic-diffusive regime

Hotspots in electronic devices can cause overheating and reduce performance. Enhancing the thermal spreading ability is critical for reducing device temperature to improve the reliability. However, as devices shrink, phonon ballistic effects can increase thermal resistance, making conventional optimization methods less effective. This paper presents a topology optimization method that combines the phonon Boltzmann transport equation with solid isotropic material with penalization method to optimize high thermal conductivity (HTC) material distributions for thermal spreading problems. Results show that the contraction-expansion structure can effectively reduce thermal resistance. Optimal distributions differ from that based on Fourier's heat conduction law, and only the trunk structure appears in optimized layouts due to the size effect. Additionally, HTC material with longer mean free paths tends to be filled around the heat source with a gap in a ballistic-diffusive regime. This work deepens understanding of thermal spreading and aids in thermal optimization of microelectronic chips.

Uncertain ballistic effects and reliability optimization design of ceramics composite armors

The uncertain ballistic effects and reliability optimization design of the ceramics composite armors are investigated. Considering the material uncertainty, the ballistic penetration process is analyzed through simulation model. The effects interlayer SiC mass fraction and the matrix thickness gradient ratio are discussed. The optimal parameters of both material and structure are obtained through reliability design methods and verified through ballistic experiments. The results show that the standard deviation can be reduced when interlayer SiC mass fraction increases. The ballistic depth can be reduced by increasing the gradient ratio. Through optimization, the ballistic reliability of the ceramic composite armor is improved.

Optical spectroscopy study of damage in ion-irradiated 3C-SiC epilayers on a silicon substrate

Epitaxial cubic (100) 3C-SiC films on a (100) silicon wafer were irradiated at room temperature with 2.3-MeV Si+ or 3.0-MeV Kr+ ions up to a fluence of 1 × 1016 cm−2. The evolutions of the epilayer and the substrate were followed as a function of ion fluence by using micro-Raman spectroscopy, optical absorption, and diffuse reflectance spectroscopy in the UV-visible and near infrared range. Raman spectra evidence the amorphization of SiC films at an estimated dose of about 0.1 displacement per atom (dpa) for both ion irradiations. The narrow peaks of the Raman-allowed TO and LO modes of SiC and Si are recorded in the virgin sample, together with few peaks assigned to zone-edge modes of SiC arising from the intrinsic disorder in the strained films. Those crystal phonon peaks broaden or disappear with increasing fluence. The spectra finally exhibit broad extra peaks assigned to the formation of Si–Si and C–C wrong homonuclear bonds in the local order of the amorphous phase. The optical transmission and diffuse reflectance spectra feature interference fringe patterns in the SiC film that are smoothened out with irradiation due to the matching of refractive indices of the amorphous SiC film and Si substrate. The evolution of the refractive index of SiC and optical gap of Si are deduced from those spectra. The respective roles of ballistic effects and electronic excitations in the radiation damage of both SiC and Si are discussed for those two ions with about the same electronic stopping power and about one order-of-magnitude difference in nuclear stopping power. The damage is dominated by the nuclear collision processes and rather well correlated with the estimated irradiation dose in dpa. Optical spectra show that electronic excitations induce damage recovery of the amorphized substrate below the SiC/Si interface. Raman spectra and optical absorption/reflection spectra yield complementary pictures of the radiation damage.

Near-junction phonon thermal spreading in GaN HEMTs: A comparative study of simulation techniques by full-band phonon Monte Carlo method

Accurate thermal simulation is essential for the near-junction thermal management and electro-thermal co-design of GaN HEMTs. While various methods have been employed to simulate phonon thermal transport in GaN, a comprehensive evaluation of their performance and reliability has yet to be conducted. In this work, first-principle-based steady-state full-band phonon tracing Monte Carlo (MC) simulations are conducted to study the thermal spreading resistance in GaN HEMTs. The results of full-band MC serve as a standard against which the applicability, accuracy, and computational efficiency of three widely-used approaches to simulate the near-junction phonon transport in GaN are thoroughly examined. The simulation techniques compared in this study include MC simulations with empirical isotropic phonon dispersion (isotropic MC), MC simulations with gray-medium approximation (gray MC), and finite-element methods (FEM) with effective thermal conductivities (FEM with keff). It is found that isotropic MC largely overestimates the thermal resistance due to the empirical model’s overestimation of phonon mean free path (MFP) distributions. By selecting an appropriate average MFP, gray MC can approximate the full-band results well, but due to its inability to reflect the contributions of different phonon modes, discrepancies are inevitable for some geometric parameters. For FEM-based analysis, although the diffusive nature of Fourier’s law precludes the reproduction of channel temperature distributions, the influence of phonon ballistic effects on the junction temperature can be accurately reflected in the well-chosen effective thermal conductivities. The comparison highlights the importance of directly incorporating first-principles-calculated phonon properties into device thermal simulations, and the paper can provide a clearer understanding of near-junction thermal transport in GaN and can be useful for thermal simulations of GaN-based devices.

Extraction of Mobility from Quantum Transport Calculations of Type-II Superlattices

Type-II superlattices (T2SLs) are being investigated as an alternative to traditional bulk materials in infrared photodetectors due to predicted fundamental advantages. Subject to significant quantum effects, these materials require the use of quantum transport methodologies, such as the nonequilibrium Green's function (NEGF) formalism to fully capture the relevant physics without uncontrolled approximations. Carrier mobility is a useful parameter that affects carrier collection in photodetectors. This work investigates the application of mobility extraction methodologies from quantum transport simulations in the case of T2SLs exemplified using an InAs/GaSb midwave structure. In a resistive region, the average velocity can be used to calculate an apparent mobility that incorporates both diffusive and ballistic effects. However, the validity of this mobility for predicting device properties is limited to cases of diffusive limited transport or when the entire device can be included in the simulation domain. Two methods that have been proposed to extract diffusive limited mobility, one based on approximating the ballistic component of transport and the other which considers the scaling of resistance with simulation size, were also studied. In particular, the resistance scaling approach is demonstrated to be the method most physically relevant to predicting macroscopic transport. We present a method for calculating the mobility from resistance scaling considerations that accounts for carrier density variation between calculations, which is particularly relevant in the case of electrons. Finally, we comment on the implications of applying the different mobility extraction methodologies to device property predictions. The conclusions of this study are not limited to T2SLs, and may be generally relevant to quantum transport mobility studies.

Crossing the ballistic-ohmic transition via high energy electron irradiation

The delafossite metal ${\mathrm{PtCoO}}_{2}$ is among the highest-purity materials known, with low-temperature mean free path up to 5 $\ensuremath{\mu}\mathrm{m}$ in the best as-grown single crystals. It exhibits a strongly faceted, nearly hexagonal Fermi surface. This property has profound consequences for nonlocal transport within this material, such as in the classic ballistic-regime measurement of bend resistance in mesoscopic squares. Here, we report the results of experiments in which high-energy electron irradiation was used to introduce pointlike disorder into such squares, reducing the mean free path and therefore the strength of the ballistic-regime transport phenomena. We demonstrate that high-energy electron irradiation is a well-controlled technique to cross from nonlocal to local transport behavior and therefore determine the nature and extent of unconventional transport regimes. Using this technique, we confirm the origins of the directional ballistic effects observed in delafossite metals and demonstrate how the strongly faceted Fermi surface both leads to unconventional transport behavior and enhances the length scale over which such effects are important.