Impact Kinetic Energy Research Articles

The gravity of Paleolithic hunting

Topographic relief potentially played an important role in Stone Age hunting from the Middle Paleolithic onwards. Natural physical features like arroyos and cliffs, among many others, likely served as traps to stop or hinder animal movement. Yet, the presence of elevation and slope variation on a landscape means that hunters also may have been able to use terrain to hunt from on high. Here, we explored via archaeological experiment how an elevated position would have interacted with projectile weaponry via the force of gravity to influence a missile’s functional efficacy. We assessed the velocity and kinetic impact energy of two Paleolithic projectile weapon systems, the thrown javelin and the atlatl (spearthrower) and dart, at ground level and then at three-, six-, and nine-meter launch heights. The experimental results of the javelin supported our predictions. Velocity and kinetic impact energy increased as launch height increased. Unexpectedly, however, atlatl-propelled darts did not conform to our predictions, not only failing to increase dart velocity or kinetic impact energy as launch height increased but also decreasing both variables’ values. These results suggest that Paleolithic hunting with an atlatl in certain contexts likely came with consequential, and previously undocumented, opportunity costs. Our results also have implications for several aspects of archaeological interpretation in Paleolithic and post-Paleolithic contexts.

Crushing responses of carbon/glass hybrid composite tubes under dynamic compressive loads

AbstractIn this study, the axial crushing response and energy‐absorbing mechanisms of circular composite tubes, which were reinforced by carbon fiber (C10) and carbon/glass hybrids (C3G4C3), were investigated experimentally and numerically. Both samples exhibited similar crushing responses comprising delamination and intralayer shear failure. The impact kinetic energy is primarily converted into frictional and composite damage energies. C3G4C3 had poorer crashworthiness with a mean crushing force and specific energy absorption of 313.3 kN and 58.0 kJ/kg, which are by 39.3% and 30.8% less, respectively, than those of C10. The influence of glass fiber reinforced polymers (GFRP) content (hybrid ratio) and stacking sequence on tubal crashworthiness was investigated numerically. For composite tubes with a hybrid ratio of 40%, the central distribution of GFRP (C3G4C3) achieved optimal energy absorption performance. Additionally, when GFRP layers were centralized stacked, a reduction of the hybrid ratio from 60% (G3C4G3) to 20% (GC8G) helped improve the crashworthiness of the hybrid tubes, where the mean crushing force increased by 23%.Highlights Impact responses of composite tubes reinforced by carbon fiber and carbon/glass hybrids were investigated experimentally and numerically. Carbon/glass hybrid tubes exhibited lower crashworthiness. The effects of stacking sequence and hybrid ratio on the energy absorption performance were studied.

On the Role of Substrate in Hydroxyapatite Coating Formation by Cold Spray

The deposition of agglomerated hydroxyapatite (HAp) powders by low-pressure cold spray has been a topic of interest in recent years. Key parameters influencing the deposition of HAp powders include particle morphology and impact kinetic energy. This work examines the deposition of HAp powders on various metal surfaces to assess the impact of substrate properties on the formation of HAp deposits via cold spray. The substrates studied here encompass metals with varying hardness and thermal conductivities, including Al6061, Inconel alloy 625, AISI 316 stainless steel, H13 tool steel, Ti6Al4V, and AZ31 alloy. Single-track experiments offer insights into the initial interactions between HAp particles and different substrate surfaces. In this study, the results indicate that the ductility of the substrate may enhance HAp particle deposition only at the first deposition stages where substrate/particle interaction is the most critical factor for deposition. Features on the substrate associated with the first deposition sprayed layer include localized substrate deformation and the formation of clusters of HAp agglomerates, which aid in HAp deposition. Furthermore, after multiple spraying passes on the various metallic surfaces, deposition efficiency was significantly reduced when the build-up process of HAp coatings shifted from ceramic/metal to ceramic/ceramic interactions. Overall, this study achieved agglomerated HAp deposits with high deposition efficiencies (30–60%) through single-track experiments and resulted in the preparation of HAp coatings on various substrates with thickness values ranging from 24 to 53 µm. These coatings exhibited bioactive behavior in simulated body fluid.

The impact protection behavior of UHPC composite structure on RC columns

In order to prevent the reinforced concrete (RC) structures from being damaged under the overload impact, a new type of composite structure—ultra-high performance concrete (UHPC)–Bio-inspired honeycomb column thin-walled structure (BHTS) was designed in this paper. A scale model with a scaling factor of 1:10 was made. The experimental tests and numerical simulations of RC column and UHPC composite structure were carried out. By comparing the impact force, displacement, shear force, bending moment and energy absorption, the protective effect of the UHPC-BHTS composite structure on RC columns under lateral impact load was evaluated. Then, the failure process of RC column was analyzed, the UHPC-BHTS composite structure absorbed 76.42% of the impact kinetic energy under the higher energy input condition, the shear failure with large damage to the RC column can be converted into bending failure with small damage. At the same time, a new damage assessment method was used to evaluate the RC column. The results show that the RC column with UHPC-BHTS composite structure can effectively protects the RC column structural integrity under impact. The design and modeling methods in this research can provide a useful reference for anti-collision design in practical engineering.

An Improved Model for Prediction of Critical Velocity of Cold-Spray by First-Principles Calculations

The first-principles calculation was applied to predict the critical velocity of Cu/Al cold-spray bonding for the first time. The bonding mechanism of cold-spray was clarified by analyzing the energy variation and atomic interaction during the cold-spray impact process. Our results showed that the shear deformation played a key role in the cold-spray bonding. The atomic interaction determined the effective absorption of impact kinetic energy and finally determined the successful bonding of the cold-spray. The heterogeneous atoms absorbed the impact kinetic energy by interatomic attraction to achieve cold-spray bonding, while the homogeneous atoms absorbed the impact kinetic energy by the deformation of interface layers. An excellent agreement between the predicted critical velocity and the experimental one could be obtained, especially for the heterogeneous material cold-spray. Our present method proved to be a simple and highly efficient computing method in critical velocity prediction. Most importantly, the critical velocity for cold-spray could be predicted without using any empirical or experimental parameters.

Study on the key parameters of ice particle air jet ejector structure

Existing ice particle jet surface treatment technology is prone to ice particle adhesion during application, significantly affecting surface treatment efficiency. Based on the basic structure of the jet pump, the ice particle air jet surface treatment technology is proposed for the instant preparation and utilization of ice particles, solving the problem of ice particle adhesion and clogging. To achieve efficient utilization of ice particles and high-speed jetting, an integrated jet structure for ice particle ejection and acceleration was developed. The influence of the working nozzle position (Ld), expansion ratio (n), and acceleration nozzle diameter ratio (Dn) length-to-diameter ratio (Ln) on the ice particle ejection and acceleration was systematically studied. The structural parameters of the ejector were determined using the impact kinetic energy of ice particles as the comprehensive evaluation index, and the surface treatment test was conducted to verify the results. The study shows that under 2 MPa air pressure, the ejector nozzle parameters of n = 1.5, Dn = 4.0, Ld = 4, and Ln = 0 mm can effectively eject and accelerate the ice particles. The aluminum alloy plate depainting test obtained a larger paint removal radius and resulted in a smoother aluminum alloy plate surface, reducing the surface roughness from 3.194 ± 0.489 μm to 1.156 ± 0.136 μm. The immediate preparation and utilization of ice particles solved the problems of adhesion and storage in the engineering application of ice particle air jet technology, providing a feasible technical method in the field of material surface treatment.

Developments of 7.62 x39mm armor piercing projectiles

Abstract Calibers 7.62 x39mm are one of the most common calibers used all over the world. As a result of developments of modern armors that become lighter, and with-stand more impact kinetic energies. Consequently, the development of ammunition becomes important to increase the combat ability of used weapons to face modern armors. In this paper, some modifications are already done in construction and design of existing bullets, in which the inner cores or parts of them are replaced by harder material, tungsten carbide, instead of lead or hard steel core. Some internal and external ballistic predictions are calculated to make sure the expected developments do not affect the weapons barrels compared with the original bullets and the check of the stability during the flight are also studied by using PRODAS package Resultant depths of penetrations are compared experimentally with that of original types, the experimental results show a noticeable increase in depth of penetration compared with that of original bullets.

Nozzle fouling in cold spray: Material transfer between Ni particles and WC-Co substrates at shallow impact angles and elevated surface temperatures

Experimental and theoretical investigations of nozzle clogging in WC-Co cold spray nozzles using nickel powder were conducted. Computational fluid dynamics (CFD) was used to show that the highest particle impact kinetic energy density occurs just downstream of the nozzle throat, where clogging is common. CFD also showed particles impact the nozzle wall at angles between 0.3°–5°, with smaller particles having higher velocities and temperatures. An experimental setup was used to investigate the effects of substrate temperature, surface roughness, and incidence angles on material deposition. Scanning electron microscopy revealed nickel particles smeared on the substrate surface, with more deposition on smoother surfaces. Energy dispersive X-ray spectroscopy (EDS) showed more nickel deposited at higher substrate temperatures and lower impact angles. Finite element simulations indicated nickel powder reaches temperatures above its melting point while sliding along the WC-Co substrate and predicted localized melting. Particle smearing is identified as the cause of nozzle clogging based on experimental and simulation results.

Impact of a Projectile on Fabrics – An Experimental Test Method

Fabric manufacturers are striving to produce value-added, high-end technical fabrics, such as smart textiles, protective clothing and accessories for sports, where the performance of the fabric has become a decisive factor. Fabric impact resistance is one such property of importance. Therefore the development of a suitable method to predict the impact on the fabric at the point of fabric development is of great importance. In this article, the authors have attempted to design and develop a test method to predict fabric impact more accurately. A mathematical model has been developed to show the relationship between impact force, impact velocity and the depth of penetration on impact. Finally, test equipment has been developed to measure the impact based on the developed model. The indentation depth on impact was measured against both impact velocity and kinetic energy, and the experimental impact force was calculated against the impact velocity. It was found that the impact velocity of the projectile affects both the impact on fabric and indentation into the backing material as well as the energy absorbed by the fabric. The energy absorption also increased with impact velocity and higher velocities caused greater damage. No great variation in temperature was detected.

Damage behaviour of rail flash-butt welding joints under controlled impact kinetic energy

Rail welded joints are a critical component of seamless railway tracks, and they are essential for maintaining the continuity and smoothness of the tracks. However, they also represent weak points in the entire track, which makes these areas susceptible to frequent damage and rail breaks. This study employs an impact wear testing platform with controlled energy to compare and analyse the impact wear characteristics of three different locations (i.e., weld zone, heat-affected zone and base material) on the U75VG flash-butt welding joint. Results indicate significant differences in material properties, such as hardness and microstructure, within different zones of the flash welded rail joints, which leads to varying impact damage behaviours. The heat-affected zones, which are located on both sides of the weld zone, exhibit the weakest ability to resist impact deformation. Thus, these areas are the most vulnerable in the entire welded rail joint and are prone to damages, such as squat. In general, damage in different zones of the welded joint gradually evolves from plastic deformation and local pitting into fatigue wear with delamination as the main failure mechanism, while the surface of the heat-affected zone tends to develop an oxide debris layer. The distinct damages observed in different zones of the welded joint pose challenges to the problem of track irregularities. This study offers a theoretical framework for predicting the evolution of damage in welded joints.

Impact resistance behaviors of boride reinforced Ti-6Al-4 V functionally graded materials: Experimental and numerical analysis

The impact resistant behaviors of boride reinforced Ti-6Al-4 V functionally graded materials prepared by spark plasma sintering (SPS) with compositional gradients of 90°, 84°, 82°and 79° were investigated based on the experimental test and the finite element method. The material constitutive parameters of the boride reinforced Ti-6Al-4 V alloys with different TiB2 contents were determined, and the Johnson Holmquist Ceramics (JH-2) model and a cohesive contact model were established and developed to predict the crack propagation and the impact resistance behaviors of the materials. The calculated results agreed well with the split Hopkinson press bar (SHPB) experimental results. The optimum material composition gradient design scheme with a continuous transition property from a high-toughness end to a high-strength end along the thin-thickness direction was determined. The G84 (0, 0, 15, 30 wt% TiB2) had the best impact resistance, with Young's modulus of 55505±5 GPa, compressive strength of 2045±5 MPa, and microhardness ranging from 535±5HV to 1246±5HV, exhibiting high strength and hardness at a high-strength end that can prolong the interaction time between the impactor and the materials, while the elongation of 39 % at its high-toughness end can cause tensile deformation, consuming impact kinetic energy efficiently. Combined with the experimental and numerical analysis results, the impact resistance and the crack-alleviated mechanisms of boride reinforced Ti-6Al-4 V functionally graded materials were discussed. Reducing the compositional gradient can alleviate the difference in coefficients of thermal expansion between composites, which may lead to strengthen the reflected wave, lower the compression wave, and suppress high-strength end failure efficiently, meaning of relieving the stress concentration under extreme service conditions. Moreover, the effects of the presence of the borides, such as in situ-formed TiB, remained TiB2at al., the dislocation defects and the whisker-like TiB on the armour materials resist fracture and layer cracking were also analyzed. This work provided a method for designing high performance of boride reinforced Ti-6Al-4 V functionally graded materials with high impact resistance and thin thickness.

Novel thermo-mechanical triggers processed by friction stir to enhance the crashworthiness of an automobile crash-box

Thin-walled tubular structures, also known as crash-boxes, are found to be efficient in dissipating kinetic energy of external impact. It is observed that the conventional aluminium square crash-boxes are characterized by higher initial peak crushing force and low crush force efficiency. In this work, a novel concept of inducing “Thermo-Mechanical Triggers” (TMTs) at discrete locations in a conventional aluminium square crash-box to enhance its crashworthiness behaviour is studied. TMTs are induced with the help of “Friction Stir Processing” (FSP), which is a localized heat treatment. The material properties of a crash-box are modified wherever TMTs are induced using FSP. The effect of changes in the location and the number of TMTs along the length of an aluminium crash-box is examined. By triggering a conventional square crash-box with TMTs, significant improvement is observed in its crashworthiness performance. The improvements are: (1) a 24% reduction in the initial peak force and (2) a 23% increase in the crush force efficiency. Therefore, TMTed crash-boxes will prove to be effective in enhancing passenger safety, which is a major concern in the automobile industry. The crashworthiness performance of a TMTed crash-box can be improved further by optimizing both the location and the number of TMTs.

Experimental study on rock-breaking characteristics of advanced premixed abrasive water jet

ABSTRACT To investigate the rock-breaking characteristics of the advanced premixed abrasive water jet, experiments of abrasive water jet eroding granite were carried out. The micro-failure morphology of erosion pits was observed and analyzed by CT (Computerized Tomography) and SEM (Scanning Electron Microscope). The results show that the difference in erosion effect caused by different rock breaking pressures is due to the difference in impact kinetic energy. The higher the jet pressure, the higher the impact kinetic energy of abrasive particles, and the erosion effect is enhanced. The difference in erosion effect caused by abrasive types is that the harder abrasives produce greater cutting force on the rock and consume less fracture surface energy. The CT scanning results show that the conical crack at the bottom is caused by the stamping action of abrasive particles and expands rapidly under the action of a water wedge, the action of reflective particles makes the erosion holes appear spindle-shaped. The results of SEM show that the sidewalls of the erosion pit are dominated by the cutting and fatigue-crushing effects of reflected abrasives. The bottom of the erosion pit is mainly driven by the punching action of the incident abrasive.

Cold spray deposition of high density polyethylene composite powders

In this paper, we investigate the use of the cold spray additive manufacturing technique to deposit micron-sized composite particles of high-density polyethylene (HDPE) compounded with either micron or nanometer sized particles of silicon dioxide (SiO2) or copper (Cu). In this study, the mass fraction of the SiO2 and copper particles added into the final composite powders was varied between 0.5 % and 9.1 % and the deposition efficiency of each composite powder was measured. Deposition of the composite powders onto an HDPE substrate was successful even at the highest particle loadings tested. In each case, an optimal mass fraction of silicon dioxide or copper particles was observed with a maximum value of deposition efficiency larger than that of the pure HDPE. For the silicon dioxide composite powders, the deposition efficiency nearly doubled compared to the pure HDPE powders. The improvement of deposition efficiency at moderate particle loadings is likely due to the increase in the impact kinetic energy of the particles resulting from the increase in the density of the composite powders. While the decrease in deposition efficiency at high particle loadings is likely the result of the increased coverage of the silicon dioxide and copper particles on the surface of the HDPE powders limiting the interaction between the HDPE of the composite powder with the HDPE substrate. SEM images show that it is possible to create a smooth, dense, and uniform thin-film polymer composite coating using cold spray.

Optimization strategy for flexible barrier structures: investigation and back analysis of a rockfall disaster case in southwestern China

Abstract. Field investigations and back analyses were conducted on a rockfall hazard. The flexible barrier protection system constructed along the roadside was damaged by the rockfall impact and lost its mitigation ability. Vital physical characteristics such as rockfall trajectory and kinetic energy were presumed based on the data from the aerial survey and the slope digital model. A numerical model, including slope, rockfalls, and flexible barrier, was created and thus the impacting process was reproduced. It demonstrates that the impact kinetic energy of the rockfall is only around 40 % of its design protection energy. The improper connections of members are the leading causes of damage, which prevent the flexible barrier from producing significant deformation and reduce its capacity to absorb impact force. The damage can be avoided by changing the connections of the members to improve the ability of the nets and ropes to slide and deform. The calculation results indicate that the impact resistance of the optimized model is 3 times better than the actual project. The findings can be used as a guide when designing a flexible protection system that performs better.

High‐velocity impact resistance of the carbon fiber composite grid sandwich structures

AbstractThe carbon fiber composite grid sandwich structure represents an innovative category of lightweight composite sandwich structures, showcasing remarkable attributes including reduced weight, high‐specific strength, exceptional specific stiffness, and robust design flexibility. Using ABAQUS, the high‐velocity impact performance of carbon fiber composite grid sandwich structure is numerically simulated. This study delved into examining the impact patterns arising from various factors, including the equivalent density, height, and geometric configuration of the core layer. Additionally, the effects of the impact punch's initial velocity, size, and impact position on the high‐speed impact resistance performance of the carbon fiber composite grid sandwich structure were explored. The fracture absorption work of the structure and the kinetic energy attenuation rate of the impact punch are positively correlated with the equivalent density, height of the structural core layer, as well as the initial velocity and dimensions of the impact punch. Notably, the square carbon fiber composite grid sandwich structure was most significantly influenced by the equivalent density of the core layer, while the mixed carbon fiber composite grid sandwich structure was most sensitive to variations in core layer height and punch size. When impacted at the intersection of the ribs, compared with the central position between the two ribs, the structure shows enhanced fracture absorption energy and greater impact kinetic energy attenuation rate.Highlights The structure was modeled based on the interlocking assembly process. The high‐velocity impact resistance of the structure was studied. Different structural parameters were designed for the core layer to study. The initial velocity, size and impact position of the punch were involved.

Numerical investigation of the low velocity impact behavior of CFRP laminates

The impact response and failure mechanism of carbon fiber reinforced composite laminates under low velocity impact was investigated using ABAQUS®. A finite element model was developed based on the progressive damage theory to study the impact response of CFRP laminates with hemispherical impactor. The impact tests were conducted on cross-ply (0/90)2s and quasi-isotropic, QI (0/45/-45/90)s laminates with different impact velocities. From the numerical simulation, the damage initiation and propagation in the CFRP laminates were found in terms of damage location, size and shape. The intra-laminar damages such as fiber and matrix damages were predicted using in-built Hashin criterion of ABAQUS®. The traction separation based cohesive surface modelling approach was utilized for capturing the inter-laminar failure initiation and propagation induced by impact loading. The numerical results of different impact energy levels were analysed for different failure modes for varying impact force, displacement and kinetic energy. The total volume of fiber damage and the total area of delamination were calculated for each laminate sequence. From numerical simulations, it was observed that the delamination was less on cohesive surfaces above the mid-thickness plane due to high compression through the thickness. The fiber damage was found at 65 J of impact energy. The first load drop was observed in the cross-ply laminates due to the delamination between lamina 5 and 6. The study revealed that the QI laminates had higher impact resistance and smaller damage zone than the cross-ply laminates.

Influence of the strain rate on the Surface Integrity on 42CrMo4 generated by machine hammer peening

Machine hammer peening is as well as deep rolling known to smoothen the surface, strain hardening and for inducing high compressive residual stresses in high depths in the surface and subsurface layer of steel. Although the beneficial effects of this manufacturing technology are well described, the influence of the strain rate on the surface and subsurface properties of machine hammer peened steel has yet to be examined. In this study three different kinetic impact energy levels and three different hammer diameters – resulting in nine different strain rates - are applied. For specimens made of hardened 42CrMo4 (AISI 4140), the analysis of the surface and subsurface properties by means of metallographic cross-sections and XRD measurements indicate that a variation of the strain rate mainly affects the depth effect at high levels of compressive residual stresses.

Experimental and numerical study on the lightweight design of load-bearing energy absorption structure for subway train

The load-bearing underframe is widely utilized on the crashworthiness design of subway trains. However, studies on load-bearing underframes mainly focused on conceptual design and structural optimization, and didn't consider the combination of bearing loads during the normal operation and absorbing impact kinetic energy under collisions. In addition, the traditional load-bearing underframe for subway trains is mainly made of stainless steel, which has a relatively large self-weight and cannot meet the requirement of lightweight design. To address these limitations, this paper presents a novel lightweight aluminum alloy load-bearing underframe with the alternative thin-walled energy absorption component, which can both satisfy the function of bearing loads and energy absorption. Firstly, the impact tests and numerical simulations are conducted to compare the crashworthiness of the energy absorption component, i.e., the thin-walled square tube made of S304 (abbreviated as S3N4) and aluminum alloy 5083P-O (abbreviated as A3N4). The result shows that S3N4 has higher energy absorption and mean crushing force, and A3N4 is 56.94 % lower than S3N4 in initial peak crushing force and 53.79 % higher in special energy absorption. Then, the aluminum alloy thin-walled tube is adopted on the novel load-bearing underframe and the parameter study on the wall thickness and number of diaphragms for the energy absorption component is conducted. The result reveals that the 5083P-O thin-walled tube with 5 mm wall thickness and 4 diaphragms can provide the stable and ordered deformation mode and high energy absorption. Finally, a real vehicle impact test is conducted to verify the crashworthiness of the optimized load-bearing underframe, which shows that the deformation modes and mechanical responses are consistent with the numerical simulation. The proposed aluminum alloy load-bearing underframe energy absorption structure can be adopted on subway trains.

Numerical analysis of dynamic collapse response of beam–column substructures under impact loads

To investigate the collapse resistance performance of steel-frame structures at varying scale ratios, numerical simulations were performed to scrutinize the influence of different scale ratios on the dynamic response of beam–column substructures subjected to impact loads. In this study, two drop-hammer impact tests were modeled and simulated, their results were compared, and the accuracy of the finite element modeling method was verified. Concurrently, a detailed model of a double half-span beam–column substructure was established to examine the effect of impact energy variations (altering the mass and velocity of the drop hammer) on the structural impact force and vertical displacement. This study analyzed variations in the impact force, impact time history, vertical displacement, internal forces, and energy absorption for models with different scale ratios when altering the impact energy. Finite element analysis results indicated that the impact velocity of the drop hammer affected the peak impact force of the substructure, whereas the drop-hammer mass influenced the force plateau and impact duration. Both the impact duration and maximum vertical displacement were positively correlated with the impact of the drop hammer and were approximately linearly positively correlated with the impact kinetic energy, resulting in the establishment of a linear fitting model between the maximum vertical displacement and the impact energy. For scaled-down substructures, variations in the impact energy could be achieved by adjusting the drop-hammer impact velocity (drop height). A proposed scale ratio for the substructure drop-hammer impact anti-collapse test is provided.