Increasing Impact Velocity Research Articles

Dynamic crushing behaviors and failure of cylindrical lithium-ion batteries subjected to impact loading

The mechanical property and failure prediction play a significant role in engineering applications of lithium-ion batteries (LIBs), but with great difficulties due to their complicated internal structures. This paper mainly focused on dynamic crushing behaviors and internal failure mechanisms of cylindrical LIBs subjected to different impact loadings for the safety assessment and protection design. A series of dynamic experiments were conducted on typical 18650 LIBs using the drop weight impact test system. The force-electric-thermal responses and impact failure modes of the cells with state of charge (SOC) dependence were experimentally explored under different impactor types. The finite element (FE) model was also established to reveal the failure mechanisms of the battery under high-velocity impact, and its accuracy was validated by the comparison between the experimental and corresponding FE results. Furthermore, the dynamic failure mechanisms of cylindrical cells using the stress wave theory were also explored in this work. It was shown that except from impact velocities, there were significant effects of the SOCs and impactor types on dynamic responses and internal failure modes of LIBs. The failure displacement of the cell will decrease with the increase of impact velocity, but it was insensitive under low-velocity crushing. Based on the FE results, the relationships between failure displacement and impact velocity and impactor diameter were established under flat-end cylinder head impacting. This work can provide some references for multi-functional dynamic integrity design and safety assessment of LIBs.

Study on the head and neck injury risk impacted by UAV: effect of impact velocity, angle, location, and mass

The number of the collision accidents between Unmanned Aerial Vehicle (UAV) and people on the ground increase in recent years. It is necessary to clarify human injury characteristics brought by the impact of UAV and promote its management. This study focuses on head and neck injury risk resulted from the impact of the UAV with a relatively large mass, and the difference brought by the UAV with a small mass. First, the model of the Y3-dummy (Hybrid III 50th) is developed. Second, simulations are conducted to analyse head and neck injury characteristics from Y3’s impact under different velocities, angles, and locations. With increasing the impact velocity, HIC and Nij increase with an exponential function and a power function, respectively. When the vertical impact velocity exceeds 5 m/s, both head and neck have a high probability of injury, while for the horizontal impact, the corresponding velocity is 9 m/s. As the impact angle increases, the changes of HIC satisfy the form of the sum of two exponential functions, and Nij changes in the form of the sum of a power function and a quadratic polynomial function. When the impact angle is close to 0°, the head injury risk is relatively high, while for 58°, the neck is more likely to be injury. The injuries induced by the top of mainframe and the front of the long arm are more serious. Finally, the differences in head and neck injury characteristics under different velocities and locations for UAVs with different masses are compared.

Numerical and theoretical modeling of the elastic-plastic bulging deformation of UHMWPE composite laminate under high-speed impact

The bulging test is crucial for evaluating the ballistic resistance of ultra-high molecular weight polyethylene laminate. However, the underlying deformation mechanism and the quantitative description of the bulging deformation, including the apex displacement and the location of the boundary of the deformation region (traveling hinge), are still lacking due to the complex dynamic elastic-plastic response under impact. In this paper, the bulging deformation of UHMWPE laminates is computationally and theoretically studied. First, an orthotropic elastic-plastic damage model considering the strain rate effect is established, which can describe the dynamic response of UHMWPE laminates in agreement with the experimental results. Secondly, the results show that the apex displacement increases linearly with the increase of impact velocity but decreases nonlinearly with the thickness. In contrast, the traveling hinge moves outward at a constant speed, independent of the thickness and impact velocity. It can be explained that the membrane stretching dominates the bulging deformation. Based on these results, an analytical model is proposed to quantitatively predict the bulging deformation, which can be used to predict the effects of the mass and the impact velocity and thickness on the bulging deformation. The work is meaningful for the design of UHMWPE laminates with high-impact resistance.

Direct tensile mechanical properties and damage fracture mechanisms of thermally damaged coal measures sandstone under high strain rate loading

The direct tensile mechanical properties of highly thermally damaged rock under high strain rate loads are a key basic mechanical problem that must be solved for the stability and effective control of surrounding rock stability in the combustion control area of an underground coal gasification project. In this paper, a two-dimensional equivalent grain-based model (GBM) unit and Split Hopkinson Tension Bar (SHTB) numerical model for thermally damaged coal-measures sandstone were constructed using particle flow code (PFC). The comparison with the experimental results shows that the numerical method can accurately describe the dynamic direct tensile behavior of thermally damaged sandstone. The following conclusions are drawn: The dynamic tensile strength of thermally damaged sandstone shows a significant strain rate-strengthening effect. With the increase in thermal damage temperature, the dynamic tensile strength of sandstone increases first and then decreases. The generation and development of hot cracks in a high-temperature environment is the fundamental reason for the change in macroscopic mechanical properties. The dynamic tensile failure process of thermally damaged sandstone can be divided into four stages: the dynamic damage initiation, the dynamic damage development, the damage crack penetration, and the sample dynamic fracture. With the increase in impact velocity, the initial kinetic energy, elastic strain energy, dissipated energy, and elastic strain energy ratio in the failure process of thermally damaged sandstone gradually increase. In contrast, the dissipated energy ratio gradually decreases. As the heat treatment temperature increases, the elastic strain energy and the ratio of elastic strain energy increase first and then decrease.

A molecular dynamics study of the effects of velocity and diameter on the impact behavior of zinc oxide nanoparticles

Molecular dynamics simulations of particle impact have been conducted for a ceramic with mixed ionic-covalent bonding. For these simulations, individual zinc oxide (ZnO) nanoparticles (NPs) were impacted onto a ZnO substrate to observe the effects of impact velocity (1500–3500 m s−1) and particle diameter (10, 20, and 30 nm) on particle deformation and film formation mechanisms that arise during the micro-cold spray process for producing films. The study shows that a critical impact velocity range exists, generally between 1500 and 3000 m s−1, for sticking of the NP to the substrate. Results suggest that solid-state amorphization-induced viscous flow is the primary deformation mechanism present during impact. Decreasing particle diameter and increasing impact velocity results in an increased degree of amorphization and higher local temperatures within the particle. The impact behavior of mixed ionic-covalent bonded ZnO is compared to the behavior of previously studied ionic and covalent materials.

Influence of interface inclination angle and load impact velocity on dynamic splitting tensile behavior and dissipated energy of geopolymer-concrete composites

The application of geopolymer has great potential in repairing damaged concrete. In engineering construction, the repaired structure is often affected by dynamic loading. Experimental research on the dynamic mechanical behavior and energy dissipation of geopolymer-concrete composites (GCC) is of great significance for understanding the bonding performance between geopolymer and concrete. In this paper, dynamic splitting experiment was performed on GCC under different interface inclination angles and load impact velocities by using the split Hopkinson pressure bar (SHPB). Then, the influence of interface inclination angle and load impact velocity on dynamic splitting tensile behavior and dissipated energy of GCC were discussed. Finally, the failure modes and strain field were analyzed based on digital image correlation (DIC) technique. The results indicate that the static peak load of GCC is roughly distributed around 26.0 kN and the dynamic peak load is 263.0 kN. The dynamic peak load measured by GCC is more than 10 times the static peak load. As the interface inclination angle increases from 0° to 90°, the dynamic peak load, static peak load and energy dissipation rate increase linearly, while the tensile sensitivity coefficient decreases. The energy dissipation ratio of GCC is kept between 0.30 and 0.40. In addition, the dynamic peak load, tensile sensitivity coefficient and dissipated energy increase gradually as the load impact velocity increases. A transition from interface failure to tensile failure can be found in GCC with the inclination angle increases.

Study of the in-plane crashworthiness performance of 6-legged starfish-inspired structures

Bio-inspired design is an impressive design method that improves a structure's crashworthiness performance and mechanical features. A cellular structure bio-inspired by a 6-legged starfish shape has been developed. Accordingly, this study examines the in-plane crushing behavior and crashworthiness of the 6-legged starfish-inspired structure (6LSIS). Analytical solutions were built based on the principle of energy balance to estimate the plateau stress in low-impact velocity conditions. Plateau stresses are related to high-impact velocities using a curve fitting method for a given wall's thickness. The predictions matched the numerical results. The crashworthiness performance of the 6LSISs mainly depends on wall thickness, impact velocity, and loading direction. It has been observed that an increase in wall thickness and impact velocity results in an enhancement in plateau stress ( σpl), specific energy absorption (SEA), and peak load (PL) in both directions. However, if the wall thickness is >0.3 mm, SEA decreases due to an increase in the structure's mass. The in-plane crushing direction ( X or Y) determines the crushing strength and deformation mode of the structure. This study illustrates that the crashworthiness of the structure in the X-direction is superior to that in the Y-direction.

Theoretical investigation on energy absorption of single-layer graphene under ballistic impact

The superb mechanical properties make graphene an ideal candidate material for impact protection. Combining molecular dynamics simulations and theoretical analyses, the deformation and failure modes, energy absorption of single-layer graphene under ballistic impact are investigated. According to numerical and theoretical results, the expression for residual velocity of projectile after impact is given. The dependence of deformation and failure modes, energy absorption mechanisms, specific penetration energy (SPE) on impact velocity is analyzed. The results show that during low-velocity impact, there are conical deformation region (CDR), star-like crack and monoatomic carbon chain in graphene. Energy absorption mechanisms of graphene are mainly local deformation and fracture. With increasing impact velocity, the size of CDR decreases. The star-like crack gradually transforms into circular hole. When impact velocity is high enough, carbon atoms within projectile projection area in graphene will be ejected in the form of debris. The kinetic energy (KE) loss of projectile is converted into KE of debris carbon atoms and fracture energy of carbon bonds. Besides, it is also found that SPE (dominant factors are deformation of conical region and KE increments) exhibits a decreasing–increasing trend with increasing impact velocity. When impact velocity is the same, SPE decreases with increasing projectile diameter.

Suppressing the pancake bouncing induced secondary contact on superhydrophobic surfaces via jet splash

Pancake bouncing of water droplets on superhydrophobic surfaces has been extensively studied, because the reduction in solid–liquid contact time shows great potential for self-cleaning, anti-icing, etc. However, the behavior of a pancake-bouncing droplet in the ambient air and its subsequent interaction with the underlying surface remain unrevealed, which is actually crucial for practical applications. In this Letter, we comprehensively investigate the overall dynamics of droplets on post-array superhydrophobic surfaces by extending the range of impact velocities. An unreported phenomenon was observed, whereby the retracting droplet undergoes vertical elongation and re-contacts the underlying surface following the pancake bouncing event. As the impact velocity increases, the submillimeter-scale posts notably influence the droplet splash, where tiny droplets are ejected from the edges of lateral liquid jets through the posts. Experimental results and scale analysis show that the critical Weber number for this jet splash phenomenon decreases with the post spacing and the post edge length over a certain range. The violent jet splash occurring at higher Weber numbers reduces the mass of the remaining droplet and, consequently, diminishes the diameter prior to retraction, thereby suppressing the secondary contact with the surface. Our findings are believed to provide valuable insight for the understanding and the application of the pancake bouncing effect.

Dynamic response and failure of CFRP Kagome lattice core sandwich panels subjected to low-velocity impact

Dynamic response and failure of carbon fiber reinforced plastic (CFRP) Kagome lattice core sandwich panels subjected to low-velocity impact were investigated experimentally and numerically. The geometrical shapes of the impactor noses are flat, hemispherical, and conical. The active failure modes of fiber fracture, matrix crack, delamination of face sheets, rib inclining/fracture of lattice core, and debonding were observed in experiment. The impactor nose shape has significant influence on the failure modes of sandwich panels. The energy absorption of sandwich panel increases with increasing impact velocity. The sandwich panel struck by the flat impactor has the highest energy absorption among three impactor noses. Finite element (FE) simulations implementing a user-defined material subroutine (VUMAT) of Hashin criterion and progressive degradation were performed and agree well with the experimental results. It is shown that both dynamic response and energy absorption of the sandwich panels are sensitive to the impactor size and impact position.

Study on solid particle erosion behavior of polymer functionally graded composites

Present research focussed on solid particle erosion behavior of epoxy/copper (Cu) functionally graded composites (FGCs). Four layered sample having different volume fraction (10%, 15%, 20%, 25%) of filler particles was developed using lay-up lamination and layered curing processes. Erosion behavior studied on abrasive-air jet testing apparatus using angular shaped silica sand erodent. Experiments were performed at impingement angles of 30°, 45°, 60°, 90° and impact velocity of 101 m/s, 119 m/s, 151 m/s and erosion rate was evaluated at different layers. Irrespective of impact velocity, FGCs showed greater erosion at 45° impingement angle which indicate their semi-ductile nature. At 45° and 101 m/s, wear rate at layer 4 comprising 25 vol% of Cu was 6.90%, 3.94%, and 1.77% lower than layer 1 (10 vol%), layer 2 (15 vol%), and layer 3 (20 vol%), respectively. Moreover, increment in erosion wear rate was observed to increase with an increase in impact velocity at all test parameters. Dominant wear mechanisms on eroded samples was observed using Scanning Electron Microscope (SEM).

Simulations of the interaction between fiber bundles/yarns and the energy absorption of the fabric under hypervelocity impact

In this work, the interaction between fiber bundles/yarns and the energy absorption of the multiple fabrics under hypervelocity impact (HVI) are studied by numerical simulation and experiments. In numerical model, an anisotropic elastic-plastic constitutive equation coupled with the Mie-Grüneisen equation of state (EOS) is adopted to describe deviatoric deformation and strongly nonlinear volumetric compression induced by HVI. Considering the internal interactions within fabrics that possess a hierarchical structure and the evolution of impact-induced debris clouds, a meso‑scale model for woven fabrics is developed using the finite element-smoothed particle hydrodynamics (FEM-SPH) adaptive method. The meso‑scale fabric model is validated through HVI experiments, and the simulation results demonstrate excellent agreement with the experimental data. Notably the model reveals an approximately linear increase relationship between the absorbed energy by the fabric and the impact energy of the projectile. Moreover, the meso‑scale fabric model exhibits enhanced predictive capability in modeling the movement and dispersion of debris clouds. Furthermore, the results of the sensitivity analysis of yarn partition indicate that the model is capable of capturing the interactions between fiber bundles/yarns within the fabric during HVI. With increasing impact velocity, the impact time decreases, which reduces the interaction between fabric components and subsequently leading to a decrease in the generated frictional energy.

Stab and yarn pull-out resistance of shear thickening fluids (STFs)/E-glass based on PEG modification and modeling yarn pull-out behavior with artificial intelligence

Impregnating fabrics with shear thickening fluid (STF) improves impact resistance. In this study modification of polyethylene glycol (PEG 200) was carried out to enhance the thickening behavior of STF. The rheological analysis shows tunned STFs by PEG modification with glutaric acid and oxalic acid increase the maximum viscosity by about 10.33 and 3.28 folds with respect to unmodified STF. Additionally, the alternations of a liquid dispersion medium (PEG) led to higher chain length in STFs, representing superior interaction between media and particles by profuse H-bonding. The results confirmed that increasing the molecular length of PEG-based on STF caused a significant improvement in the knife and spike stabbing impact resistance, quasi-static, and yarn pull-out performance of the neat fabric. In addition, it was realized, by increasing impact velocity the energy absorption ability of STF-treated fabric composite increases. Additionally, a regression analysis using artificial intelligence was applied to study the effect of the pull-out rate on the mechanical response of different materials. Using a third-order polynomial for AI regression model, it turned out that while the pull-out rate has the least influence on untreated E-glass fabrics (UEG) response, for other materials, the behavior changes significantly by increasing the rate from 100 to 400 mm/min.

The damage characteristics and formation mechanism of ultrahigh strength 7055 aluminum alloy under hypervelocity impact

This paper studies the damage morphology evolution of ultrahigh strength 7055 aluminum alloy plate under the hypervelocity impact of aluminum projectile, and analyzes the formation mechanism of crater morphology at different impact velocities. It is found that the impact crater evolves from spherical crown shape to spherical-conical composite shape, and eventually transforms into hemispherical shape with the increase of impact velocity. The evolution of crater shape is highly associated with the ratio of steady-state shock pressure and the strength of the alloy. The variation of crater diameter as a function of impact velocity follows the hypothesis of hemispherical theory, while the crater depth shows a great deviation due to the formation of conical region at the crater bottom and spall fracture at the back of the target. It is demonstrated that the formation of conical crater is related to the poor resistance to shear localization of 7055 aluminum alloy due to its low strain hardening capacity under dynamic loading. Hence, adiabatic shear bands are generated and evolve into shear cracks, thereby causing the formation of conical region at the crater bottom. It is suggested that the resistance to shear localization should be highly considered for the design, evaluation and selection of protection materials for spacecraft.

A comparative study on dynamic compression response of multi-cell thin-walled structures with filling foams and connecting ribs

In order to comparatively study effect of foam filling and connecting ribs on dynamic response of multi-cell thin-walled structure (MTS), high velocity (30–70 m/s) mass block impact tests were performed on empty MTS, polyurethane foam (PUR) filled MTS (FMTS) and 2nd order MTS (MTS-2nd) with connecting ribs between sub-cells. The dynamic enhancement mechanism of energy absorption of three kinds of thin-walled structures was discussed based on experimental and numerical results. The results indicate that the dynamic enhancement coefficient (DEC) of the mean crushing force (MCF) is 1.07–1.23 and 1.08–1.33 for empty MTS and FMTS, respectively. The dynamic enhancement of total energy absorption (EA) is 11.4–26.32% for MTS, 13.83–32.52% for FMTS and 4.3–9.68% for MTS-2nd, compared to the quasi-static compression. The multi-cellularization tends to degenerate the crushing force sensitivity of MTS to the loading rate, while the foam filling increases the sensitivity. The inertia effect is the main reason for the dynamic enhancement of crushing force of thin-walled structures. The coupling effect of FMTS is related to the dimensions of sub-cells, the impact velocity and the foam strength. The folding pattern and deformation stability of MTS can be improved by filling foams and increasing impact velocity. The multi-cellularization by using connecting ribs is still the most effective method to improve the specific energy absorption of thin-walled structures, although it causes a size effect and reduces the robustness of deformation modes.

Experimental investigation on the impact force of the oblique water entry of a slender projectile with spring buffer

On water impact, a projectile experiences impact forces that can threaten its structural safety and the stability of its trajectory. In the engineering applications, the underwater vehicle may need to entry and exit of water several times. The elastic buffer can be used repeatedly, which meet the requirement of the scene. To mitigate the effects of a strong impact, a projectile with a spring buffer connecting its main body and disk is designed in this work. The impact force of the main body during water entry is studied experimentally. The experimental equipment and the force measurement system are newly developed by the authors. The main focus is the cavity evolution and the axial force of the main body. The cavity of the projectile with a buffer is slightly elongated and thickened compared with that without a buffer. A special necking phenomenon of the cavity is observed as the spring buffer is compacted. The effects of the spring stiffness, the disk mass, and the impact velocity on the axial force and impulse are extensively discussed. Compared with the case without a buffer, the axial force of the main body is only mitigated within a small range of stiffness values. When the stiffness increases, the axial force begins to fluctuate with a larger peak and a narrow pulse. The peak force is nearly twice that in the case without a buffer. However, the impulse is always smaller, although some fluctuations occur in the larger stiffness cases. Additionally, an increased disk mass can also mitigate the force peak and the impulse of the main body, but fluctuations also occur in cases with larger masses. The coefficients of the axial force and the impulse of the main body decrease with increasing impact velocities. The result indicates that the elastic buffer only in a narrow stiffness can effectively reduce the impact load of the water entry projectile. This study can provide references for the load reduction design of the projectile with an elastic buffer during water entry or exit.

Dynamic response characteristics of grooved cylindrical shells in Taylor impact experiments

Buffer energy absorbing structures have very high use value in daily life, industrial production, aerospace and other fields. Cylindrical shells are used as a highly efficient buffer and energy absorbing structure due to their own structure and good mechanical properties. Taylor impact experiments were conducted on three types of structural cylindrical shells (non grooved, inner grooved, and outer grooved) and numerical model was also established to study and analyze the dynamic response characteristics of the three types of structural cylindrical shells. Finally, the deformation mechanism of the cylindrical shell was analyzed theoretically to explore the impact of grooving treatment on the deformation of the cylindrical shell. The results show that with the increase of impact velocity, the length of the cylindrical shells of the three structures decreased, and the diameter of the impact end and the maximum diameter increased. Each of the three specimens had a convergence velocity(convergence velocity: The impact end diameter of cylindrical shell is the initial impact velocity at the maximum diameter), that is, when the impact velocity was greater than or equal to the convergence velocity, its maximum diameter was equal to the diameter of the impact end. When the impact velocity exceeded a certain value, the deformation modes of the three types of cylindrical shells changed. The comparison of experimental and simulation results proved the effectiveness of the numerical model. The maximum stress was always above the impact end face. It was concluded from the theoretical analysis Due to the stress concentration at the groove, the stress distribution and internal stress distribution of the cylindrical shell were affected, which in turn affected the deformation and energy absorption capacity of the cylindrical shell. At the same impact velocity, the outer grooved cylindrical shell has the shortest buffer time and the BW specimen had the most gentle buffer curve before 35μs .

Experimental study on energy release effect of reactive bullet impacting soil simulated target

To study the energy release of PTFE-Al reactive material bullets penetrating soil target, by firing the bullet with a 12.7mm ballistic gun, and using a high-speed camera to record the energy release process when impacting a simulated target, a nylon 6 plate with 5mm thickness, which has an approximate wave impedance to soil target. The result shows that when the velocity of the bullet is at 553m/s, a flame extinguishes immediately after the PTFE-Al is evoked but could not continue. With the increase of impact velocity, the secondary energy release reaction with greater strength can be realized after the first energy release of the reactive material is excited and maintained for a certain period. It is concluded that the critical velocity of the PTFE-Al reactive material impacting the soil is about 553m/s, and the energy release effect becomes more severe with the increase of impact velocity.

Trajectory deflection of noncircular cross-section projectile penetrating into metal targets

To analyze the trajectory deflection of a noncircular cross-section projectile penetrating into multiple metal targets, numerical simulations with different impact velocities, projectile tip height and charge geometry are conducted. The simulation model is established using the finite element software LS-DYNA and verified based on the experiment carried out by a single-stage light gas gun. The results show that the impact velocity significantly affects the trajectory deflection of noncircular cross-section projectile. Although the deflections may be different in direction, the magnitudes exhibit decreasing trends with the increasing impact velocity. Besides, the trajectory varies from downward deflection to upward deflection with the increase of projectile tip height, and changes significantly with the tip height ranging from 0.8mm to 1.1mm. Further, as the geometry profile of projectile remains unchanged, the ones with noncircular charge exhibit better ballistic stability as compared with the circular charge projectile. This is mainly related to the variation in projectile mass instead of the variation in moment of inertia.

CFD-DEM coupled calculation of wall wear characteristics during particles flow impacting the wall process

The continuous impact of the particles flow on the wall during industrial bulk material transport can lead to wall wear. In this paper, a physical model of the particle flow impacting the wall at different angles is established, and the wear condition of the particles flow impacting on the wall is studied by using the coupling method of CFD-DEM. Firstly, the accuracy of the erosion model is verified by the existing experimental data. Secondly, the effects of particle incidence angle, particle velocity and particle volume fraction on wall wear are analyzed by numerical calculation. The results show that the mass loss and erosion ratio of the target plate are the largest when the particle incidence angle is between 15° and 30°. When the particle incidence angle is near 45°, the maximum wear depth will appear on the wall surface. The increase of particle impact velocity led to an exponential increase in the mass loss, erosion ratio and wear depth of the target plate, but did not change the wall wear morphology. The particle volume fraction is positively correlated with the mass loss of the target plate. With the increase of particle volume fraction, the change of erosion ratio is more obvious at 90° impact, but has little effect at 45° impact. The change of particle volume fraction has an important effect on the wall wear morphology.