Impact Configuration Research Articles

Study of equi-energetic effects on the low-velocity impact and compression after impact response of carbon fiber composite tube structures

This study investigates the equi-energetic low-velocity impact (LVI) and compression after impact (CAI) response of tubular CFRP structures. Various layups and geometries are employed to understand the effects of impact energy, configurations, and damage on the CAI behavior. Low mass-high velocity (LMHV) impact results in greater absorbed energy than high mass-low velocity (HMLV). Impact damage formation, especially circumferentially, significantly affects CAI strength. Braided tubes show higher impact resistance, but weaker compressive strength compared to unidirectional/twill tubes. A new analytical model provides accurate prediction of CAI strength. This study emphasizes the importance of impact energy and lay-up configurations in CFRP design.

Impact load characterization for security barrier performance assessment through simulations using generic vehicle models

The threat stemming from the use of vehicles as a weapon in urban environments may be mitigated by employing properly designed protective structures such as bollards, street furniture or landscaping options. In order to assess the performance of a barrier resistance to a vehicle impact, the initial step involves characterizing the load on the barrier. To this aim, two recently developed generic vehicle models are utilized to conduct numerical simulations of vehicle impacts on a security barrier. Various impact configurations are examined and compared based on force-time functions. In addition to comparing the impact loadings in terms of peak forces, comparisons are also done in terms of equivalent static loads, determined by computing the dynamic load factors (DLF). The study provides new insights into the characterization of vehicle impact loads on security barriers, which could improve current engineering practices in the field.

Exploring the catastrophic regime: thermodynamics and disintegration in head-on planetary collisions

ABSTRACT Head-on giant impacts (collisions between planet-sized bodies) are frequently used to study the planet formation process as they present an extreme configuration where the two colliding bodies are greatly disturbed. With limited computing resources, focusing on these extreme impacts eases the burden of exploring a large parameter space. Results from head-on impacts are often then extended to study oblique impacts with angle corrections or used as initial conditions for other calculations, for example, the evolution of ejected debris. In this study, we conduct a detailed investigation of the thermodynamic and energy budget evolution of high-energy head-on giant impacts, entering the catastrophic impacts regime, for target masses between 0.001 and 12 M$_{{\oplus }}$. We demonstrate the complex interplay of gravitational forces, shock dynamics, and thermodynamic processing in head-on impacts at high energy. Our study illustrates that frequent interactions of core material with the liquid side of the vapour curve could have cumulative effects on the post-collision remnants, leading to fragmentary disintegration occurring at lower impact energy. This results in the mass of the largest remnant diverging significantly from previously developed scaling laws. These findings suggest two key considerations: (1) head-on planetary collisions for different target masses do not behave similarly, so caution is needed when applying scaling laws across a broad parameter space; and (2) an accurate model of the liquid-vapour phase boundary is essential for modelling giant impacts. Our findings highlight the need for careful consideration of impact configurations in planetary formation studies, as head-on impacts involve a complex interplay between thermodynamic processing, shocks, gravitational forces, and other factors.

Numerical design and experimental validation of shockless plate impact configurations for the Lagrangian analysis of armor ceramics

Ceramic materials are widely used in armor or protective structures, providing weight saving at equivalent performance in comparison to their steel counterparts. Plate-impact experiments are commonly used to investigate the dynamic behavior of ceramics under compressive loading. Using the particle velocity measured at the back of the target, some mechanical properties such as the Hugoniot elastic limit (HEL) as well as the Hugoniot curve of the material can be deduced. Nevertheless, these tests do not provide a direct measurement of the plastic hardening (post-HEL) behavior of the target. In the present work, an experimental shockless plate-impact configuration was developed and implemented to conduct a Lagrangian analysis. This configuration relies on the use of a wavy-machined flyer plate impacting a target made of a buffer, two ceramic plates of different thicknesses, and two window plates as backing. First, the use of wavy flyer plates to generate a loading ramp was validated by considering the impact of the wavy-machined flyer plate against a target, both made of 316L steel. A numerical analysis of this test was developed to confirm the pulse-shaping effect observed experimentally. Next, a ceramic, F99.7 alumina was subjected to the shockless plate impact test in Lagrangian configuration considering the same steel as a buffer and flyer plate material. These tests coupled with Lagrangian analysis enable the curve of axial-stress vs axial-strain beyond the isentropic elastic limit (IEL) to be deduced. The experimental data allow identifying the parameters of an elastoplastic with strain-hardening model to describe the behavior of the tested alumina.

On using machine learning algorithms for motorcycle collision detection

Globally, motorcycles attract vast and varied users. However, since the rate of severe injury and fatality in motorcycle accidents far exceeds that of passenger car accidents, efforts have been directed towards increasing passive safety systems. Impact simulations show that the risk of severe injury or death in the event of a motorcycle-to-car impact can be greatly reduced if the motorcycle is equipped with passive safety measures such as airbags and seat belts. For the passive safety systems to be activated, a collision must be detected within milliseconds for a wide variety of impact configurations, but under no circumstances may it be falsely triggered. For the challenge of reliably detecting impending collisions, this paper presents an investigation towards the applicability of machine learning algorithms. First, a series of simulations of accidents and driving operation is introduced to collect data to train machine learning classification models. Their performance is henceforth assessed and compared via multiple representative and application-oriented criteria.

Does the current testing standard of chest protectors warrant the devices’ protection for PTW riders in collisions?

Non-inflatable chest protector is a passive safety device to protect powered two-wheeler (PTW) riders from thorax injuries. Before being put on the market, the protectors should be qualified for the European standard tests EN1621-3:2018 which remains uncertain regarding the impact energy level, force evaluation thresholds, and impact configurations. This study aims to ascertain whether the standard EN1621-3:2018 ensures adequate chest protection for PTW riders. Thus, three generic protectors were created to qualify for standard tests and then evaluated against rider chest impact scenarios by finite element modelling. Bar-to-rider and rider-to-bar virtual impacts were simulated with a range of impact energy 50 ∼ 1563 J. In virtual standard tests, protector 1 had the lowest impact force, followed by protectors 2 and 3. In chest impact analysis, the rider with or without protector was rarely found injured under the testing standard energy level (50 J). The chest impact force was below the standard force threshold of 24 kN under all impact energy levels. Protector 3 had a generally better protection performance in terms of chest deflection than protectors 1 and 2, which were not consistent with the standard testing results. The rider chest responses in bar-to-rider impacts differed significantly from the responses in bar-to-rider impacts. Therefore, future testing standard might introduce more appropriate impact energy, force thresholds and accident-relevant impact configurations to ensure the device’s effectiveness in providing protection during PTW crashes. This study furnishes valuable insights into enhancing the design and evaluation methodologies of protective gear, thus directly contributing to the advancement of PTW rider safety.

Centre of gravity of motor vehicles

In vehicular accident reconstruction, a number of parameters need to be estimated, as commonly no specific measurement data or convenient measurement methods are available. One of these parameters is the position of a car’s centre of gravity. Depending on the impact configuration, the centre of gravity may have a significant influence on the reconstruction result. A number of regression models and rules of thumb have already been developed in the past to calculate the position of the centre of gravity. The further automotive vehicle development in recent years has led to different vehicle architectures with larger masses. This study therefore deals with developing and testing a new regression model for vehicles, distinguishing between conventional and electric drives. That is based on the analysis of 147 rollover stability measurements of road vehicles from the years 2016–2022. The model developed from these tests for the centre of gravity height shows a good fit with the measurement data and only requires knowledge of the roof height.

QCA Analysis of the Impact of Digital Economy on Export Technological Complexity: A Study Based on the Social and Economic Data of 31 Provinces in China

The digital economy, characterized by informatization and big data as key factors of production, and relying on digital technologies such as the internet and artificial intelligence, represents a new economic paradigm. Its potential to facilitate the transformation and upgrading of manufacturing industries and to enhance the technological complexity of exports necessitates empirical testing. This paper examines the association between factors related to the digital economy and the technological complexity of exports, drawing upon socioeconomic data from 31 provinces and regions in China in 2021, and employing a fuzzy-set qualitative comparative analysis approach. The findings suggest that the digital economy can indeed foster an increase in the technological complexity of exports. Human capital, research and development (R&D) capabilities, digital infrastructure, financial capital, government scale, and market size all exert a positive influence on the technological complexity of exports. The impact configurations of the digital economy on the technological complexity of exports can be classified into two main types: government-market driven R&D innovation, and digital infrastructure-led multifactor influenced. Within the latter category, four subtypes are distinguished: digital infrastructure single-factor dominance, digital infrastructure-led with weak market, digital infrastructure-led with insufficient government strength, and digital infrastructure-led with weak R&D. In areas with a higher level of digital economy, its influence on the technological complexity of exports is notably more positive. The construction of digital infrastructure and R&D capabilities are core conditions affecting whether a region can achieve a high level of technological complexity in exports. Concurrently, attracting human capital, increasing government support, and expanding market size are also factors that cannot be overlooked.

Impacts on Crash Cushions—Analysis of the Safety Performance of Passenger Cars with Improved Safety Equipment Compared with Test Vehicles Based on Assessment Criteria as Defined in EN 1317

To assess the safety performance of crash cushions, guidelines or standards are used. Real-life accident conditions might deviate substantially from the approval test conditions. The objective of this study is to evaluate occupant safety in passenger cars in the event of an impact against a crash cushion. Real-life accident configurations deviate significantly from the impact configurations used in the approval test EN 1317. In four different tests, two vehicles regularly used in EN 1317 and two vehicles with improved safety equipment (airbag, pretensioner, and load limiter) are used. The impact speed is 100 km/h, whereas the crash cushion is designed for an impact speed of 80 km/h. One configuration is defined as a full overlap, and one has a 50% offset. The ASI (Acceleration Severity Index), THIV/OIV (Theoretical Head Impact Velocity/Occupant Impact Velocity), and PHD/ORA (Post Head Deceleration/Occupant Ride down Acceleration) are calculated from the acceleration signals. The offset impact was more serious for both the regularly used vehicle and the vehicle with improved safety equipment. Vehicles with improved safety equipment do not have any influence on these criteria. It is apparent that new occupant safety technologies will not have any influence on occupant safety performance. The criteria currently in use are more likely to be of use for assessing vehicle performance rather than occupant safety.

High-Compression Crash Simulations and Tests of PLA Cubes Fabricated Using Additive Manufacturing FDM with a Scaling Strategy

Impacts due to drops or crashes between moving vehicles necessitate the search for energy absorption elements to prevent damage to the transported goods or individuals. To ensure safety, a given level of acceptable deceleration is provided. The optimization of deformable parts to absorb impact energy is typically conducted through explicit simulations, where kinetic energy is converted into plastic deformation energy. The introduction of additive manufacturing techniques enables this optimization to be conducted with more efficient shapes, previously unachievable with conventional manufacturing methods. This paper presents an initial approach to validating explicit simulations of impacts against solid cubes of varying sizes and fabrication directions. Such cubes were fabricated using PLA, the most used material, and a desktop printer. All simulations could be conducted using a single material law description, employing solid elements with a controlled time step suitable for industrial applications. With this approach, the simulations were capable of predicting deceleration levels across a broad range of impact configurations for solid cubes.

Controlled interlaminar crack initiation in thin notched laminated thermoplastic composites under impact loading: A first step towards unitary layer recovery

The recycling of composite materials is nowadays a major challenge as it is systematically associated with a downcycling due to the reduction of the fiber length. However, recent works demonstrated that the delamination-based recovery of the unitary layers of laminated structures with preserved mechanical properties is possible under dedicated loading conditions. The presented work aims at investigating this innovative process and in particular the interlaminar crack initiation from a straight notch milled in the material by using an impact loading; further crack extension to recover the complete lamina being the following step of the process. A Split Hopkinson Bar setup has been used in a Direct Impact configuration and a dedicated test setup has been implemented to impose translational and rotational kinematics to the impacted side of the tested specimens in order to enable crack initiation and propagation over a few millimeters. Imposing translational kinematics to the impacted side of the specimen has been shown to induce cracks in a reproducible manner. Numerical simulation results explain the more favorable conditions provided by the translational kinematic.

Detailed analysis of a deep learning energy forecast model considering different input units and dimensions

The use of smart buildings technologies in residential houses, commonly referred to as smart homes, can benefit the operation and management of the buildings as well and its users. The application of energy related models in smart buildings can improve building sustainability and efficiency, but, usually, requires the existence of energy forecasting models capable of providing accurate and precise information. In this paper, it was studied how different input configurations of an energy forecasting model impact its performance by considering multiple error metrics. The conducted study allowed a detailed analysis of each input configuration to see which one is better suitable to be integrated with the smart grid management platform developed by the authors, which is also presented in this paper. The results demonstrate that the inputs’ units and dimensions have impact on the forecast error, indicating that accumulative Wh values are potentially better for the energy forecast model considered.

Bimolecular collision outcomes on multidimensional potential energy surfaces: infrared spectroscopy and activation of NO-alkane collision complexes.

In bimolecular collisions between open-shell radicals and increasingly-larger alkanes, the relative impact configurations open the possibility of reactive and nonreactive outcomes that are isomer specific. To model the interaction potential between molecular scattering partners, observables are needed from experiments that can quantify both the initial molecular orientations and internal energies on multidimensional potential energy surfaces. Recent work by our group demonstrated that upon infrared (IR) excitation, the dynamics of the nitric oxide-methane collision complex (NO-CH4) are dependent on the initial monomer geometries, as small changes in configuration substantially affect the energies, electronic couplings, and predissociation pathways due to the Jahn-Teller effect. This study focuses on the isomer-specific scattering mechanisms between NO and ethane (C2H6), encoded in the spectroscopic and dynamical signatures of the NO-C2H6 collision complex. IR action spectroscopy with 1 + 1 resonance-enhanced multiphoton ionization of NO products was employed to characterize the fundamental CH stretch transitions of NO-C2H6, as well as to initiate the nonreactive decay mechanisms of the complex. Furthermore, velocity map imaging (VMI) was utilized to explore the dynamics prior to and following IR excitation of NO-C2H6, imprinted on the NO photoproducts. This work compares the dynamics from NO-C2H6 and NO-CH4 vibrational predissociation, in which substantial differences are observed in the energy exchange mechanisms during the evolution of the collision complexes to products.

Collisions between Drones and Rotorcraft: Modeling of the Crash Response of Battery Packs

Drones operating in an urban environment pose a potential collision threat to rotorcraft. In this paper, the battery pack of the DJI MAVIC 2 ZOOM is analyzed since the battery is considered to be the greatest threat due to its high weight and stiffness. Following a pyramid-type building block approach, a high-fidelity model simulation was developed for LSDYNA based on a wide range of experiments, ranging from quasi-static material tests to quasi-static component tests up to high-velocity impact experiments. The high-fidelity model allows the prediction of damage in potential collision scenarios between a high-speed rotorcraft and the battery pack of the drone. For the particular impact configuration analyzed within this paper, the drone battery does not cause catastrophic failure of the windshield of the rotorcraft.

Handling inevitable collision states by Advanced Driver Assistance Systems functions: software-in-the-loop performance assessment of an injury risk-based logic in a “lane departure” scenario

The downward trend in the number of fatalities and serious injuries related to road accidents depends on the implementation of increasingly performing Advanced Driver Assistance Systems (ADAS) in the circulating fleet. The greatest benefit of the adoption of ADASs like Autonomous Emergency Braking (AEB) consists in limiting the frequency of impacts. However, in Inevitable Collision States (ICSs), the decrease in impact closing speed guaranteed by the AEB may not reduce the Injury Risk (IR) for the occupants: IR is a function of the vehicle’s velocity change in the collision () – a combination of impact closing speed and impact eccentricity. The work virtually analyses, in lane departure ICS scenarios, the performance of an adaptive steering and braking intervention logic based on instantaneous IR minimization. The adaptive logic reduces IR compared to the absence of intervention (down to 80 times lower) and to the AEB (down to 40 times lower) by leading the ego vehicle toward eccentric impact configurations. It is highlighted that full activation of the steer-by-wire system in 0.3 s allows the adaptive logic to also reduce the frequency of impacts; it is further evidenced that employing a function capable of modulating the braking level to minimize IR entails disadvantages from the IR perspective compared to the AEB: efficient intervention strategies on the steering are the only alternative for increasing the safety provided by high-performance ADASs. Finally, compared to previous literature, the study highlights high efficiencies of the adaptive logic in a wide range of ICS scenarios.

Preliminary evaluation of a passive safety device concept for the protection of riders

Powered Two-Wheeler riders are over-represented in crash statistics worldwide, and currently available safety solutions have not triggered a decreasing trend. A new device concept, comprised of a wearable vest with belt stripes sewn on the back and fastened to the motorcycle frame through a metal cable, was developed to save riders’ lives. The objective of this paper is the evaluation of its protective effectiveness in a set of representative crash configurations selected from the ISO 13232 database. The configurations were reproduced in a multibody environment, and each of them was characterised through the following parameters: the impact speeds, contact points, relative heading angle, and the Boolean presence of the safety device. The preliminary evaluation revealed encouraging outcomes as several body regions reported reduced injury indices. However, the benefits depended on the speed range and impact configuration. Overall, the benefits outweighed the additional risks in the selected accident database.

Dynamic tests of the protective and security barrier system probar

The purpose of this paper is to present a series of dynamic tests for testing the protective and security barrier of the PROBAR system, developed by STRIX Chomutov, a.s., according to the PAS 68:2013 standard. The goal of the tests was to assess how the obstacle resist impacts and whether it can absorb the energy exerted on it. Verification of the mechanical properties of the device was performed in two types of impact configurations. Emphasis was placed on the behaviour of both the obstacle and the vehicle during the impact and in the short time interval after the collision. In terms of criteria for evaluating the impact tests, it can be stated that Test 2 exceeded the Theoretical Head Impact Velocity (THIV) criterion by 20 km h−1, while Test 1 did not exceed the limit value. However, all values for other criteria (ASI, PHD, HIC, 3ms) were within the specified limits, and the safety barrier met the required criteria which allows to be certificated.

Investigating the Chemical Stability of Electrospray Plumes During Particle Collisions

Electrospray thrusters fulfill the main propulsion requirements for long-term small-satellite missions. However, the molecules present in the plume are susceptible to collisions, chemical reactions, and fragmentation, which may introduce different new species with various mass-to-charge ratios inside the plume. Prediction of the byproducts that appear upon collisions is of prime importance to predicting the evolution of the plume and estimating the performance and the lifetime expectancy of the thruster. In this work, we use molecular dynamics simulations to investigate monomer–neutral collisions at different impact configurations, impact energies, and impact parameters, and we provide the mass spectra of the resulting species. We predict that 1) collisions within a center-of-mass distance of 6 Å can result in momentum exchange and molecular fragmentation, 2) higher-energy impacts produce more byproducts, and 3) heavy molecules (e.g., 1-ethyl-3-methylimidazolium [EMI] and BF4) are more likely to result from weak collisions (<30 eV), whereas light molecules (e.g., H, F, and CH3) are more likely to result from strong collisions. Collisional fragmentation is shown to negatively affect key performance indicators, including reductions in thrust, specific impulse, and propulsive efficiency. This phenomenon potentially accounts for the observed discrepancies in experimental measurements of current and mass loss rates.

A novel bio-inspired helmet with auxetic lattice liners for mitigating traumatic brain injury

The human head is most vulnerable to injury during activities such as road traffic and sports. To mitigate the risk of traumatic brain injury (TBI), helmets serve as an important protective device. This study proposes a hedgehog biomimetic helmet with auxetic lattice liners in the shape of a hemisphere. The helmeted head impact configuration is built based on a high bio-fidelity head-neck finite element model incorporated into our novel helmet model. Biomechanical responses including acceleration, intracranial pressure, and von Mises strain of head are extracted from the simulation model to assess TBI risks. The results indicate that the helmet featuring auxetic lattice liners outperforms those without liners or with other liner designs, offering superior protection. Compared to the threshold, the novel helmet design was found to reduce the head injury criterion value by 72.65%. Additionally, parametric studies of lattice’s bar radius for uniform and graded auxetic lattice liners are discussed. Finally, this study also carries out the optimization design of lattice strut radius and height, resulting in a lightweight auxetic lattice liner with superior protective performance. The outcomes of this study extend the application of auxetic materials and provide guidance for designing helmet liners that better mitigate TBI.

Design of a low-velocity impact framework for evaluating space-grade materials

Material deformation and failure under impact loading is a subject of active investigation in space science and often requires very specialized equipment for testing. In this work, we present the design, operational analysis and application of a low-velocity (∼100m/s) projectile impact framework for evaluating the deformation and failure of space-grade materials. The system is designed to be modular and easily adaptable to various test geometries, while enabling accurate quantitative evaluation of plastic flow. Using coupled numerical methods and experimental techniques, we first establish an operating procedure for the system. Following this, its performance in two complementary impact configurations is demonstrated using numerical and experimental analysis. In the first, a Taylor impact test is performed for predicting the deformed shape of a cylindrical projectile impinging on a rigid substrate. In the second, deformation of a plate struck by a rigid projectile is evaluated. In both cases, physics-based models are used to interpret the resulting fields. We present a discussion of how the system may be used both for material property estimation (e.g., dynamic yield strength) as well as for failure evaluation (e.g., perforation and fracture) in the same projectile impact configuration.