Axial Impact Loading Research Articles

Study on energy absorption of paper honeycomb sandwich tube filled by polyethylene foam under axial loading

This work proposed an approach to multi-component non-metallic materials, namely regular polygonal paper honeycomb sandwich tubes filled with polyethylene (PE) foam, and focused on the influence of drop impact parameters and structural parameters on the deformation characteristics and energy absorption of the filled tubes. Axial drop impact tests were employed to exert drop impact loading on cross-sections of the specimens with a square drop weight. The results showed that the X-direction filled tube (X-DFT) had a higher crushing strength and yield strength than that of the Y-direction filled tube (Y-DFT). As the tubular cross-section edge number of the filled tube increased, the specific energy absorption (SEA) and specific total efficiency (STE) decreased. Under the same axial drop impact loading conditions, the SEA and STE of the X-DFT were superior to those of the Y-DFT. As the edge number of the tubular cross-section or the tubular length ratio increased, the SEA and STE of the filled honeycomb tube decreased significantly. While the impact energy increased, the SEA and STE of the filled tubes increased approximately linearly. This work investigated the influence of drop-impact and structural parameters on deformation characteristics and energy absorption. It is expected to provide supplementary documentation for the advancement of cushion protection technology and the optimization of product structure.

Energy Absorption of a Novel Lattice Structure‐Filled Multicell Thin‐Walled Tubes Under Axial and Oblique Loadings

Multicell design and lattice structure as filling material are two effective methods for enhancing the energy absorption performance of thin‐walled tubes. This study combines these two approaches to present a multicell tube with a novel lattice structure and investigates the energy absorption performances of these hybrid multicell tubes under axial (0°) and oblique (10°, 20°, and 30°) impact loading conditions. As filling structure, β‐Ti3Au lattice geometry with varying lattice strut diameters and the number of lattice unit cells are used, while the single and multicell thin‐walled tubes with different tube thicknesses are employed as main absorbing element. In this context, the effects of numbers of lattice unit cells, lattice strut diameter, cell numbers of the tube, and tube thickness on energy absorption performance of hybrid tubes are examined using validated nonlinear finite element models. This investigation unveils that the synergistic interplay between the multicell tubes and lattice structure during deformation significantly elevates the energy absorption performance of the hybrid structure. Notably, the findings demonstrate that multicell hybrid tubes exhibit a remarkable capacity to absorb up to 30.36% more impact energy compared to the aggregate absorption of individual components in hybrid tubes.

Experimental study on the elastic response characteristics of a rotating body under an oblique water impact load

In this study, an integrated experimental model was designed and a data acquisition system was established to capture the structural response of an elastic rotating body throughout the oblique water impact process. This established experimental methodology offers a dependable approach for gathering structural response data during the water impact process. The axial impact loads and effective stress on the rotating body throughout water impact were measured using acceleration sensor and strain gauge rosettes installed in the water impact zone of the structure, while a high-speed camera system captured the evolution of the flow field. Results from the arbitrary Lagrangian-Eulerian (ALE) numerical model were compared with those from repeated experiments, revealing good agreements. The article conducted water impact tests at different impact initial conditions, analyzing the response of the body to the impact load during water entry process across different water impact velocities and angles. Observations during the oblique water impact process revealed that the stress response at the center of the rotating body impact surface is approximately equal to that of the first water impact point, with this effect becoming more pronounced at higher velocities. This study contributes valuable experimental data for numerical investigations into the water impact of elastic structures.

Numerical simulation of response behavior and damage regularity of human lower limbs under axial impact load

Abstract Axial impacts to the lower extremities of personnel in events such as explosions and falls on the underside of vehicles, which are extremely hazardous to personnel, may result in serious injuries. Most of the current studies on human lower limb injuries from axial loading have not considered the restraining effect of the knee joint. In this paper, based on the THUMS human finite element model, the failure parameters of the tibia, calcaneus, and talus of the lower limb are added and verified. On this basis, the response behavior of the lower limbs of personnel under different axial loads is investigated, and the damage law is further analyzed and studied. It is found that the motion of human lower limbs under axial impact is divided into two phases: the axial motion phase and the rotation phase around the knee joint, and the lower limbs are mainly subjected to compression and bending loads, respectively. The duration of the axial motion phase is related to the impact velocity and the rate of change of velocity and affects the magnitude of tibial force.

Optimisation of collapse in functionally graded thickness honeycomb under axial impact loading

This research investigates the collapse behaviour of a honeycomb energy absorber featuring variable wall thickness. Initially, numerical simulations were conducted to analyse the effect of wall thickness in upper and lower sections of the absorber, as well as the parameter 'n‘ that characterises the type of thickness variations within the wall, as design variables. A comprehensive database was compiled, encompassing various combinations of these parameters. Subsequently, a mathematical model was developed by fitting it to the initial data using the response surface methodology. The specific absorption energy and initial crush force were computed and utilised as the objective function for optimisation. Ultimately, by employing the Particle Swarm Optimisation (PSO) technique and applying problem constraints, an optimal configuration for the honeycomb absorber was determined, with a focus on maximising the specific absorption energy. The optimised outcome obtained from the optimisation algorithm exhibited an enhancement of approximately 11% compared to the maximum values of the input samples. Furthermore, multi-objective functions were employed during the optimisation process to identify absorber parameters that would achieve both the maximum specific absorption energy and the minimum initial peak force.

Energy absorption of a novel auxetic structure reinforced by embedding tubes

To enhance structural crashworthiness while achieving lightweight design, this paper proposes a novel configuration that embeds a thin-walled square tube into auxetic structure which can take full advantage of the interaction between the auxetic structure and embedding tubes. The finite element model of auxetic structures reinforced by embedding tubes is established and validated by the compression experiments. The crashworthiness performance of auxetic structure (AUX), auxetic structure reinforced by embedding tubes (AET), and auxetic structure-filled tubes (AFT) are compared to find that the AET have the highest energy absorption and specific energy absorption (SEA). Through parametric analysis, designing the angles between short and long beams (θ1, θ2) as 70° and 40° can contribute to the crashworthiness performance, respectively. A suitable range for long beam thickness lies between 1.4 mm and 1.6 mm, while a short beam thickness of around 1.2 mm is more effective. The specific configuration can enhance the SEA and reduces peak crushing force (PCF). Increasing the thickness of the embedded tube can improve the crashworthiness by sacrificing the weight. It is a good balance between the crashworthiness performance and weight by designing the tube thickness as 1.2 mm. An analytical model is also established to predict the energy absorption of auxetic structure reinforced by embedding tubes under axial impact loadings. The surrogate modeling technique and the NSGA-II algorithm are also employed to optimize the AET configuration. The results show that the SEA of the optimized structure can increase from 14.5 kJ/kg to 18.6 kJ/kg, while the PCF can be reduced from 164.6 kN to 124.3 kN. Therefore, the auxetic structure reinforced by embedding tubes can play a critical role in the engineering field to absorb energy.

Experimental and numerical studies on AFRP-reinforced thin-walled tubes under axial impact loading

With the increase in global threats to infrastructure, from unforeseen events particularly in steel structures, there is a growing urgency to strengthen the impact resistance of steel elements. This research aimed to investigate the potential of using AFRP (Aramid Fiber Reinforced Polymer) to improve the energy absorption and crushing resistance of thin-walled circular hollow steel (CHS) tubes subjected to axial impact loads. Key aspects of the investigation include conducting a series of experiments to evaluate the impact of AFRP layer thickness, steel tube thickness, and impact velocity on structural performance. The performance metrics were characterized by analyzing impact force versus displacement, energy absorption capacity, peak crush load, and mean crush load. The results show that AFRP strengthening significantly enhances peak load capacity, energy dissipation, and impact force absorption compared to plain steel tubes. The AFRP-strengthened specimens exhibit higher specific energy absorption (SEA) and crushing force efficiency (CFE) compared to non-strengthened specimens, with peak force increasing by 18 % to 160 % for low external energy and 14 % to 190 % for high external energy. The three-dimensional finite element (FE) model accurately predicts load-carrying capacity and AFRP failure, validated against experimental tests. This study provides quantitative evidence of the effectiveness of AFRP reinforcement in improving the crash performance of thin-walled tubes under axial impact loading, highlighting the potential for optimizing AFRP strengthening techniques in structural applications.

Numerical crashworthiness analysis of 2014 Aluminium-Silicon Carbide Particle (SiCp) foam filled Carbon Fiber-Reinforced Plastic (CFRP) tube under impact loading

Aluminium foam and Carbon Fiber Reinforced Plastic (CFRP) are widely used composite materials in automobile industries due to the benefits of lightweight and energy absorption capacity. Therefore, in this study, the numerical crashworthiness analysis of 2014 Aluminium-SiCp (2014AA-SiCp) foam filled in CFRP tube has been performed under impact loading. Quasi-static compression tests have been conducted on 2014AA-SiCp foam to extract the mechanical parameters required for numerical simulations. To understand the crushing behavior under the axial impact loading, 2014AA-SiCp foam-filled CFRP tube has been numerically modelled using ABAQUS® software. The parametric study was carried out to explore the effects of filler material, foam densities, and impact velocities on crushing behavior. It was found that load increases with the rise in foam density and impact velocity. Moreover, the deformation increases with the increase in impact velocity. Results showed that the load carrying capacity of foam filled CFRP tubes was significantly improved compared to that of empty CFRP tubes. The foam filled CFRP specimens exhibited peak load of 122 kN and an energy absorption capacity of 3012 J, showcasing an approximate improvement of 43% and 11% respectively, over the values obtained for empty CFRP tubes.

Design optimization of the bamboo-inspired foam-filled tube for high-speed train collision energy absorption

This study first developed a novel bamboo-inspired foam-filled tube (BFFT) for potential application in high-speed trains, considering the practical use conditions. The BFFT was initially designed by mimicking the macro and micro characteristics of bamboo culms and understanding their axial crushing mechanical behavior. The key bionic parameters are drawn based on the crashworthiness indices of natural bamboos with various geometric sizes and growth ages. The numerical simulation model of the BFFT under axial impact load was established and verified using simplified super folding element (SSFE) theory and drop-weight experiments. A multi-objective optimization on the BFFT was conducted to find the optimal parameter alternative, integrating experimental design method of the optimal Latin hypercube, the response surface agent model and the non-dominated sorting genetic algorithm (NSGA-II). The crashworthiness performance of the optimized BFFT was compared with the initial design scheme, a conventional circular tube and other existing energy absorbers of rail vehicles. The results indicated that the EA, SEA and IPCF values of the optimized BFFT can be improved by 150.2 %, 63.3 %, and 48.5 %, respectively, when considering the single target requirement. In comparison to the initial design scheme and conventional circular tube, the SEA value of the final optimized BFFT increased by 44.7 % and 53.0 %, respectively. The proposed novel BFFT demonstrated a superior crashworthiness, providing inspiration for enhancing and optimizing passive safety performance of high-speed trains.

Dynamic Brazilian tests of yellow sandstone under coupled static and dynamic loads

Through a series of static mechanical tests and (SHPB) dynamic impact tests, the static and dynamic mechanical parameters of rock as represented by yellow sandstone are determined, and the Holmquist-Johnson-Cook model parameters of the rock are calibrated using the test data and theoretical calculations. The feasibility of a numerical model is verified, and numerical analysis of the SHPB impact process under different radial pressure pre-loading is carried out on the basis of good verification. The results show that with increasing impact load, the degree of rock breakage increases, as does the dynamic tensile strength. With the application of increasing pre-static pressure, the dynamic tensile strength of the rock decreases gradually, and the maximum radial cumulative strain increases continuously under a given impact pressure, indicating that micro-cracks in the rock develop initially and then expand under the influence of pre-static pressure; the rock is more easily broken, and its weakening degree increases. Under coupled dynamic and static loading, the energy utilization rate of rock in the Brazilian splitting process is jointly affected by axial compression ratio and impact load. Too large a pressure ratio will reduce the strain-rate sensitivity of rock, resulting in low energy utilization rate, while too low an axial compression ratio will make the dynamic tensile strength of rock relatively high, which is not conducive to tensile failure. Therefore, on the premise of clear fracture form requirements, a suitable combination of axial compression ratio and impact velocity can improve the rock crushing effect and energy utilization rate.

Dynamic crushing behavior of a novel bi-directional gradient lattice structure under axial and oblique impact loadings

To meet the crashworthiness requirement of lightweight structures under different impact directions, a series of novel bi-directional gradient lattice structures (BD-GLSs) are proposed to improve their oblique impact resistance performance. In this paper, four types of BD-GLSs with both symmetric and asymmetric gradient topology configurations are constructed by varying the side lengths of lattice unit cells in xy-plane, and their crushing behavior under axial and oblique impact loadings are numerically investigated. The dynamic crushing behaviors are highlighted by comparing with the traditional uniform and uni-directional gradient lattice structures, which is validated via experiment studies. It is demonstrated that the specific energy absorption of the BD-GLSs with symmetric gradient topology configuration can achieve an increment of 42.26 % as compared to the uniform lattice structure. Moreover, the specific energy absorption of BD-GLSs with symmetric gradient topology configuration is 47.63 % higher than that of the uni-directional gradient lattice structure under oblique impact, which suggests that the bi-directional gradient topology can provide better crashworthiness performance under the oblique impact conditions. The symmetrical gradient topology configuration has greater bearing capacity and better crashworthiness under both axial and oblique impact loadings by comparing with other gradient topology configurations. The proposed bi-directional gradient topology configuration provides an optimal design strategy for the crashworthiness design of lightweight structures, especially in the case of unknown impact load directions, which has a great competitive advantage in crashworthiness applications.

Numerical simulation on dynamic compression properties of sandstone under axial static preload

In this study, through a series of static mechanical tests and split Hopkinson pressure bar (SHPB) dynamic impact tests, the static and dynamic mechanical parameters of yellow sandstone are determined, and the Holmquist–Johnson–Cook model parameters of the rock are determined by the test data and theoretical calculation. The feasibility of a numerical model is verified, based on which the SHPB impact process under different axial pressure is subjected to numerical analysis. The results show that with increasing impact load, the degree of rock breakage increases, and the dynamic compressive strength and dynamic elastic modulus increase continuously. With the application and increase of axial pressure, the dynamic compressive strength and dynamic elastic modulus of the rock decrease gradually under the same impact load, and the maximum cumulative strain keeps increasing, indicating that under the influence of axial pressure, micro-cracks in the rock have initially developed and expanded. With increasing axial pressure, the rock is more vulnerable to breakage, and its weakening degree keeps increasing. The energy utilization rate of one-dimensional dynamic and static combined loading is affected by the axial compression ratio and impact load. At low axial compression ratio, the rock has high impact resistance but high energy utilization rate; at high axial compression ratio, the rock has low impact resistance but low energy utilization rate. Therefore, the combination of axial compression ratio and impact velocity can improve the crushing effect and energy utilization rate on the premise of clear crushing form requirements.

Energy absorption characteristics of a novel hierarchical cross tube under axial impact loading

Energy absorption characteristics of a novel hierarchical cross tube under axial impact loading

Calculation of the initial peak loads on thin-walled circular tubes with internal and external staggered grooves under low-velocity impacts

Thin-walled cylindrical tube structures with particular defects exhibit more stable energy absorption characteristics and lower initial peak loads when subjected to axial impact. The present study systematically investigates the effect of the depth, width, and number of grooves in both internal and external groove structures on the energy absorption characteristics of thin-walled cylindrical tubes made of A6061 under axial impact loading. An expression for predicting the initial peak load is formulated, and its validity is confirmed through experimentation and extrapolation. The results indicate that augmenting the depth, width and quantity of grooves can lower the initial peak load, and the depth of grooves bears the most pronounced impact. The initial load hypothesis is congruent with both experiments and simulations, with a initial peak error of just -7.64%. To affirm the generality of the theoretical computations, eight distinct groups of elongated structural simulations were compared, and the initial peak load's error was scarcely above 10%. This study serves as a point of reference for designing energy-absorbing structures with internal and external grooves when subjected to low-velocity axial impact.

Wave propagation in beams with functionally graded porosity distribution under highly transient axial and transverse impacts

Recent advances in the manufacturing process provide a possibility of fabricating a new generation of porous materials denoted by functionally graded porous materials (FGPM). This paper aims to present a time domain analysis of wave propagation through the porous structures with functionally graded porosity distribution, which has not been completely studied before. For this purpose, the beams with different functionally graded porosity distributions subjected to both axial and transverse tip impact loads with a high-frequency content are investigated. The shear deformable cantilevered functionally graded porous beams with various porosity distributions through the beam thickness are studied. The governing differential equations are derived using the Hamiltonian principle based on the Timoshenko beam theory. A locking-free first-order shear deformable beam element is used to derive the finite element formulation of the equations. The Newmark time integration method is used to perform a time domain analysis of the equations of motion and to investigate the transient response of the beams. The axial and transverse wave propagation characteristics through functionally graded (FG) porous beams are found using time domain analysis of the results. Deflection and velocity time histories of the tip and each point of the beam, reflection time, and variation of support reactions are obtained. The influences of the porosity magnitude and porosity distribution on the wave propagation characteristics and overall time responses are investigated. The results reveal that porosity distribution has a significant effect on the wave amplitude, wave speed, and reflection from the boundary. Also, this study can help in a better understanding of porous structures' behavior subjected to high-transient impact loads in different engineering applications.

Grooves and Cross Section Effects on Energy Absorption of S-Shaped Tubes Under Axial Quasi-Static and Impact Loading

Grooves and Cross Section Effects on Energy Absorption of S-Shaped Tubes Under Axial Quasi-Static and Impact Loading

Evaluating Pelvis Response During Simulated Underbody Blast Loading.

In recent conflicts, blast injury from landmines and improvised explosive devices (IEDs) has been the main mechanism of wounding and death. When a landmine or IED detonates under a vehicle (an under-body blast), the seat acceleration rapidly transmits a high load to the pelvis of the occupants, resulting in torso and pelvic injury. Pelvic fractures have high mortality rates, yet their injury mechanism has been poorly researched. Three (3) fresh-frozen male pelvic specimens were tested under axial impact loading. The pelvis was impacted mounted upside down by dropping a 12 kg mass at target impact velocities ranging from 1 to 8.6 m/s with time to peak velocity ranging from 3.8 to 5.8 ms. Resulting fractures were broadly categorized as involving a bilateral pubis rami fracture, a bilateral ischium fracture, and sacroiliac joint disruption. The study provides insights into the type and severity of pelvic injury that may occur over a range of under-body blast (UBB)-relevant loading profiles.

Numerical investigation on energy absorption characteristics of impact-resistant lightweight structure of bio-mimetic micro aerial vehicle

With the increasing development of micro aerial vehicle, the impact resistance of the structure has gradually become a research hotspot. The beetle's exoskeleton not only provides important protection for its body and flexible wings but also ensures its good flight performance. Therefore, the beetle's exoskeleton has become an important research content in the field of bio-mimetic micro aerial vehicles. In this study, taking the internal structure of the beetle's exoskeleton as the research object, a kind of bio-mimetic lightweight thin-walled impact-resistant structure that can be used in the micro aerial vehicle is proposed. The energy absorption characteristics of the bio-mimetic structure under axial impact loading are calculated and analyzed by the numerical simulation method, and the important parameters such as impact angle, protective layer thickness, and wall thickness are optimized and discussed. The main results include that the filling method of the hollow column has a certain correlation with the energy absorption characteristics of the structure under different impact angles, and among the different cross-sectional shapes, the hollow column with a circular cross-sectional configuration has the best energy absorption ability. In addition, as the internal space of the structure increase exponentially, the decrease of specific energy absorption value of the bio-mimetic structure is relatively small. Finally, the wall thickness with good energy absorption characteristics is about 1.5 mm, while the preferred span length of the structure is between 90 and 120 mm.

Development and Optimization of a High-Frequency Axial-Torsional Composite Percussion Drilling Tool for Enhanced Impact Technology

Summary A high-frequency axial-torsional composite percussion drilling tool is designed to enhance the drilling efficiency by delivering high-frequency axial and torsional impact loads directly to the drill bit. The impact performance and influencing factors of the tool are analyzed via the large eddy simulation method, and a scaled-down experiment on the pulse nozzle structure is conducted. The analysis reveals that after design optimization, the tool achieves high-frequency axial and torsional impacts of 421 and 284 Hz, respectively, at an inlet flow rate of 30 kg/s. Additionally, the unilateral amplitudes of the axial and torsional impact loads reach 1511 N and 19.3 N·m, respectively, with a pressure drop of 2.998 MPa. Furthermore, the similarity degree between the parameters derived from the experiment and numerical analysis is close to or exceeds 70%, demonstrating the reliability and precision of the numerical analysis results. Overall, this study sets a baseline for high-frequency impact technology, paving the way for further advancements in drilling efficiency.

Simplified impact force models for novel FRP-steel–concrete composite columns under axial impact loading

This study aims to investigate the axial impact resistance of FRP tube-confined concrete-encased cross-shaped steel column (FCCSC). The numerical simulations were conducted utilizing the ABAQUS software. The finite element (FE) models developed in this study were validated and upgraded by fitting the relevant test data of FRP-confined concrete-filled steel tube (FCFST). Subsequently, a significant number of models were established and executed with four variable parameters, namely impact mass, impact velocity, concrete strength and FRP tube thickness. Based on the analysis results, typical axial impact states were summarized and defined. Then, the simplified impact force time history models were developed for predicting the dynamic responses of FCCSCs subjected to axial impact loads. The dynamic damage index for axial impact resistance and the corresponding design flow of FCCSCs also have been proposed.