Simulation Of Impact Research Articles

Low speed impact simulation of explosive charge based on three-dimensional numerical manifold method

The present work addresses the challenge of evaluating the low speed impact response of polymer bonded explosive charges with three-dimensional numerical manifold method. Based on the cover-based contact theory, the contact algorithm is implemented by transforming position relationships between reference points a0 and entrance block E(A, B). Meanwhile, based on statistical micro-cracks, a Visco Scram mechanical model for the explosive charge is established. Using the classic Steven test, the influence of charge thickness, diameter, and warhead shape on the mechanical response are analyzed under low speed impact. The simulation results indicate that, increasing the thickness of the charge can effectively avoid internal damage of the explosive caused by projectile extrusion and holder confinement; Increasing the aspect ratio of the charge can alleviate the large deformation; Increasing the shape and size of the warhead can make the charge extrusion shallower, alleviating the concave shear damage of the charge. The simulation results verifies that the developed contact algorithm in this paper can effectively solve 3D impact problems, and provides guidance in the design of charge structures to some extent in the weapon system.

Shock impact simulation model along with the harmonic effect of the working device

This study analyses the impact of initial conditions on the results of numerical simulations of the fan load with underwater detonation and simultaneously typical harmonic loads from the operating device. It was shown that different initial conditions affect both displacement and velocity results. Furthermore, significant differences were indicated when comparing the results with devices without harmonic loads. The results indicate the need for more detailed analyses at the initial stage of modelling the impact resistance of devices planned for ship installation.

Numerical investigation of hypervelocity impact simulation with FEM/SPH formulation for space structures

This paper investigates the response of aluminum structures to hypervelocity impact (HVI) and the formation of debris clouds using the Adaptive Finite Element (FEM)/Smoothed Particle Hydrodynamics (SPH) method. The main objective is to accurately replicate the response of curved thin plates to various HVIs and to characterize the resulting debris cloud shapes., for representative of shielding structures against Micrometeoroids and Orbital Debris (MMOD). In particular, the effects of different solid element formulations on the adaptive method are investigated. Experimental data from the literature is used to validate the proposed model, which is then applied to a curved thin plate subjected to varying impact angles. The findings highlight the significant influence of solid element formulation on the effectiveness of the adaptive method. Moreover, a direct correlation is observed between the impact angle and the produced debris cloud shape. These results contribute to the current knowledge on HVI responses and provide valuable insights for predicting and analyzing debris cloud formation in relation to aluminum structures.

Significant risks that trigger cost overruns and delays in urban rail projects: a typical case study of Vietnam

PurposeUrban rail projects are typically large-scale transport infrastructure projects (megaprojects) which have many potential risks that can influence the strategic goals of owners. However, there is a paucity of studies which explore the impact of risks on both “urban rail” project time and cost together considering quantitative assessments. Therefore, this paper focuses on investigating critical risks and quantifying such risk impacts on urban railway project schedule and cost in practice.Design/methodology/approachA combination of qualitative and quantitative research methods comprising semi-interviews with five experts and a questionnaire survey of 132 professional respondents is used. The data were modeled using Monte Carlo Simulation to predict the probability of project schedule and cost.FindingsThe results show that 30 risk variables are categorized into seven main groups which have significant impacts on both project time and cost. Outstanding five risk variables were highlighted as follows: (1) project site clearance and land compensation; (2) design changes; (3) physical project resources; (4) contractors’ competencies and (5) project finance. Such findings were supported by Monte Carlo simulation which predicted in the worst case that the project may suffer 11.03 months’ delays and have cost overrun with a contingency of US$287.68 million.Originality/valueThis study expands our knowledge about time and cost contingency of urban metro railway implementation across developing economies and particularly within the context of Vietnam. Policymakers will not only gain an understanding about risk structure but will also recognize the significant impacts of critical risk through risk impact modeling and simulation. Such an approach provides insights into risk treatment priorities for planners so that they can proactively establish suitable strategies for risk mitigation in practice.

Multiple objective optimal design for an electrically assisted bicycle under dynamic finite element analysis

ABSTRACT Electrically assisted bicycles have become increasingly popular in modern cities. This article presents an optimization design process to enhance the strength of an electrically assisted bicycle frame (EABF) model. This process includes several techniques such as uniform design (UD), Kriging interpolation (KGI), entropy weighting analysis (EWA), gray relational analysis (GRA), and genetic algorithm (GA). The EN 15,194 test standard is used to calculate the maximum deformation of the fork in an EABF, through falling mass (FM) and falling frame (FF) impact simulations with ANSYS/LS-DYNA software. Six geometry characteristics of an EABF are selected as control factors. The UD generates multiple simulation tests, as each control factor in the design space is continuous. Dynamic finite element analysis (FEA) is conducted to determine the maximum impact deformation (ID) of each experiment in the UD. Applying a multiple objective optimization process, the best design for an EABF is obtained. The newly designed model offers a maximum improvement of 4.20% over the original design for the largest distortion. In conclusion, the multiple objective optimization technique improves the maximum ID of an EABF.

Retinomorphic Photonic Synapses for Mimicking Ultraviolet Radiation Sensing and Damage Imaging

AbstractPhotonic synapses integrate sensing and processing within a single device, making them promising candidates for emulating the visual perception of a biological retina. Most retinomorphic photonic synapses achieve image pre‐processing by differentially responding to red, green, and blue (RGB). However, the impact of invisible ultraviolet (UV) light on the retina remains insufficiently explored, hindering the perception of the full spectrum by retinomorphic devices. Herein, a photonic synapse is constructed with strong UV absorption of Poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐(4,4′‐(N‐(4‐sec‐butylphenyl) diphenylamine)] (TFB) as photosensitive layer. The device exhibits synaptic properties of long‐term memory (LTM) and short‐term memory (STM) at different UV radiation stages. Extracting the electrical conductance of the device under UV radiation generates patterns of different resolutions, facilitating the simulation of retinal damage's impact on object perception. Moreover, an electronic eye system, incorporating the photonic synapse under UV radiation, successfully replicates pupil constriction and eye‐closing behaviors akin to those observed in a real biological eye. This result underscores the authenticity of retinomorphic devices, expending a novel concept for the future development of visuomorphic computing.

Droplet impact on doubly re-entrant structures

Doubly re-entrant pillars have been demonstrated to possess superior static and dynamic liquid repellency against highly wettable liquids compared to straight or re-entrant pillars. Nevertheless, there has been little insight into how the key structural parameters of doubly re-entrant pillars influence the hydrodynamics of impacting droplets. In this work, we carried out numerical simulations and experimental studies to portray the fundamental physical phenomena that can explain the alteration of the surface wettability from adjusting the design parameters of the doubly re-entrant pillars. On the one hand, three-dimensional multiphase flow simulations of droplet impact were conducted to probe the predominance of the overhang structure in dynamic liquid repellency. On the other hand, the numerical results of droplet impact behaviours are agreed by the experimental results for different pitch sizes and contact angles. Furthermore, the dimensions of the doubly re-entrant pillars, including the height, diameter, overhang length and overhang thickness, were altered to establish their effect on droplet repellency. These findings present the opportunity for manipulations of droplet behaviours by means of improving the critical dimensional parameters of doubly re-entrant structures.

Design Optimisation of Metastructure Configuration for Lithium-Ion Battery Protection Using Machine Learning Methodology

The market for electric vehicles (EVs) has been growing in popularity, and by 2027, it is predicted that the market valuation will reach $869 billion. To support the growth of EVs in public road safety, advances in battery safety research for EV application should achieve low-cost, lightweight, and high safety protection. In this research, the development of a lightweight, crashworthy battery protection system using an excellent energy absorption capability is carried out. The lightweight structure was developed by using metastructure constructions with an arrangement of repeated lattice cellular structures. Three metastructure configurations (bi-stable, star-shaped, double-U) with their geometrical variables (thickness, inner spacing, cell stack) and material types (stainless steel, aluminium, and carbon steel) were evaluated until the maximum Specific Energy Absorptions (SEA) value was attained. The Finite Element Method (FEM) is utilised to simulate the mechanics of impact and calculate the optimum SEA of the various designs using machine learning methodology. Latin Hypercube Sampling (LHS) was used to derive the design variation by dividing the variables into 100 samples. The machine learning optimisation method utilises the Artificial Neural Networks (ANN) and Non-dominated Sorting Genetic Algorithm-II (NSGA-II) to forecast the design that produces maximum SEA. The optimum control variables are star-shaped cells consisting of one vertical unit cell using aluminium material with a cross-section thickness of 2.9 mm. The optimum design increased the SEA by 5577% compared to the baseline design. The accuracy of the machine learning prediction is also verified using numerical simulation with a 2.83% error. Four different sandwich structure configurations are then constructed using the optimal geometry for prismatic battery protection subjected to ground impact loading conditions. An optimum configuration of 6×4×1 core cells arrangement results in a maximum displacement of 7.33 mm for the prismatic battery in the ground impact simulation, which is still less than the deformation threshold for prismatic battery safety of 10.423 mm. It is shown that the lightweight metastructure is very efficient for prismatic battery protection subjected to ground impact loading conditions.

Atmospheric Loss in Giant Impacts Depends on Preimpact Surface Conditions

Earth likely acquired much of its inventory of volatile elements during the main stage of its formation. Some of Earth’s proto-atmosphere must therefore have survived the giant impacts, collisions between planet-sized bodies, that dominate the latter phases of accretion. Here, we use a suite of 1D hydrodynamic simulations and impedance-match calculations to quantify the effect that preimpact surface conditions (such as atmospheric pressure and the presence of an ocean) have on the efficiency of atmospheric and ocean loss from protoplanets during giant impacts. We find that—in the absence of an ocean—lighter, hotter, and lower-pressure atmospheres are more easily lost. The presence of an ocean can significantly increase the efficiency of atmospheric loss compared to the no-ocean case, with a rapid transition between low- and high-loss regimes as the mass ratio of atmosphere to ocean decreases. However, contrary to previous thinking, the presence of an ocean can also reduce atmospheric loss if the ocean is not sufficiently massive, typically less than a few times the atmospheric mass. Volatile loss due to giant impacts is thus highly sensitive to the surface conditions on the colliding bodies. To allow our results to be combined with 3D impact simulations, we have developed scaling laws that relate loss to the ground velocity and surface conditions. Our results demonstrate that the final volatile budgets of planets are critically dependent on the exact timing and sequence of impacts experienced by their precursor planetary embryos, making atmospheric properties a highly stochastic outcome of accretion.

Investigation of dislocation and twinning behavior in HMX under high-velocity impact employing molecular dynamics simulations.

Under the ReaxFF/lg force field, the multiscale shock technique (MSST) was employed to investigate the decomposition behavior of perfect, dislocated, and twinned octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) at a velocity of 11 km/s. This study aimed to analyze the changes in system temperature, bond formation and breaking, variations in the number of small molecules, and the number of clusters. The results indicated that the sensitivity of dislocated HMX was the lowest, while the sensitivity of twinned and perfect HMX was comparable. Comparing the formation and breaking of bonds in HMX during the shock process, it was found that the change in the number of bonds in dislocated HMX was similar to that in perfect HMX, whereas twinning accelerated the breaking of bonds. By analyzing the changes in small molecular fragments (CO, CO2, H, H2, H2O, N2, N2H, NH2, NO, NO2, and O) during the shock process of HMX, it was found that dislocation had a relatively minor effect on the small molecular fragments, while twinning promoted the generation of CO, H, NO, and O and accelerated the decomposition of NO. A comparison of the number, weight, and atomic ratio of clusters under perfect, dislocated, and twinned conditions revealed that under the influence of shock, the number of clusters initially increased sharply and then decreased slowly. Meanwhile, compared to the perfect and dislocated explosives, the number of clusters under the twinned structure was significantly fewer, indicating that the twinned structure could reduce cluster formation. The proportion of oxygen to carbon in the twinned HMX was lower than that in the perfect and dislocated explosives, possibly due to the higher content of small molecular fragment O in twinned HMX. Different structures of HMX crystals were constructed, including twinned defect structure (with a supercell containing 6458 atoms), dislocation defect structure (with a supercell containing 2352 atoms), and perfect structure (also with a supercell containing 2352 atoms). The modeling of defect crystal structures was carried out using the Atomsk software. For the twinned defect structure, we first constructed a mirror symmetric structure of the original configuration and then merged these two structures together. For the dislocation defect structure, we shifted a segment of the originally ordered perfect crystal structure by a certain distance using Atomsk. Before conducting the simulations, we performed geometric optimization of the models using the conjugate gradient (CG) algorithm and carried out 10 ps of NVT and NPT simulations to equilibrate the energy, temperature, and other parameters within the system. Finally, a 50-ps MSST impact simulation was performed using Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS).

Simulation of gross primary productivity and impact of drought in Liulin watershed of Taihang mountains over 2000–2020

As the largest flux in the global terrestrial carbon cycle, Gross Primary Productivity (GPP) is a key factor for the terrestrial carbon budget. Based on the eddy flux tower data, remote sensing data and the meteorological precipitation data, we calibrated three parameters of maximum light use efficiency, optimum temperature, and maximum temperature in the Vegetation Photosynthesis Model (VPM) to reproduce the GPP spatiotemporal characteristic in Liulin watershed of Taihang Mountains. We further analyzed the time lag effect and cumulative effect of the standard precipitation index (SPI) on GPP by the Pearson correlation coefficients. Results show that VPM captures the GPP characteristics of eddy flux tower observation in Liulin watershed. During the calibration period (R2 = 0.94, RMSE = 0.47 g C m-2·d-1) and validation period (R2 = 0.91, RMSE = 0.60 g C m-2 d-1), the adjusted VPM model successfully reproduced the temporal dynamics of site-observed GPP. From 2000 to 2020, VPM model can effectively reproduce the long-term variations in GPP (R2 = 0.69 vs. NIRv_GPP), with the GPP ranging from 446.4 to 828.1 g C m-2 y-1 and an average value of 545.6 g C m-2 y-1 in Liulin watershed. The GPP exhibited an increasing trend from 2000 to 2020. A mutation in the GPP occurred in 2010, with an average annual increase of 13.9 g C m-2 y-1 from 2000 to 2010 (p < 0.05), followed by an average annual increase of 10.22 g C m-2 y-1 from 2011 to 2020 (p > 0.05). The SPI effectively monitored drought events in the Liulin watershed. With a cumulative effect of 9 months and a lag effect of 6–7 months, the time lag and cumulative effects of drought had a long-term effect on GPP. It is imperative to have long-term eddy flux tower data and meteorological data to better evaluate the spatiotemporal dynamics of GPP and the impact of drought.

Fast Magnetization Vector Inversion Method with Undulating Observation Surface in Spherical Coordinate for Revealing Lunar Weak Magnetic Anomaly Feature

The three-dimensional magnetic vector structure (magnetization intensity and direction) of the planet can be effectively used to analyze the characteristics of its formation and operation. However, the quick acquisition of a large region of the magnetic vector structure of the planet with bigger observation surfaces undulation is hard and indispensable. We firstly proposed a fast magnetization vector inversion method for the inversion of a magnetic anomaly with the undulating observation surfaces in the spherical coordinate system, which first transforms the data to a plane when the data are distributed on a surface. Then, it uses a block-Toeplitz-Toeplitz-block (BTTB)-FFT to achieve fast inversion with the constraint that the magnetization intensities of the grids between the transformed observation surfaces and the terrain are zero. In addition, Gramian constraint term is used to reduce the ambiguity of the magnetic vector inversion. The theoretical model tests show that the proposed method can effectively improve the computational efficiency by 23 times in the 60 × 60 × 10 grid division compared to the conventional inversion method, and the accuracy of the two computation methods is comparable. The root-mean-square error of the magnetization intensity is only 0.017, and the angle error is within 1°. The magnetization vector structure shows that the largest crater diameter does not exceed 340 km in the Mare Australe region, the amplitude of the magnetic anomaly is much higher than the current meteorite impact simulation results, and the depth of the magnetic source is less than 10 km, which cannot be explained by the impact simulation experiments. In addition, the magnetization directions of adjacent sources differ by 122° (or 238°), and the high-frequency dynamics of the Moon as well as the short-lived dynamics may be responsible for this phenomenon. The magnetization directions of the three adjacent sources in the Mare Crisium region are close to each other and differ in depth with different cooling times, making it difficult to record the transient fields produced by meteorite impacts. In addition to the above characteristics, the magnetization direction of the magnetic sources in both regions is uniformly distributed without reflecting the dispersion of the magnetization direction of the meteorite impact magnetic field. Therefore, it can be inferred that the magnetic anomalies in these two regions are related to the generator hypothesis.

Design and low-velocity impact behavior of an origami-bellow foldcore honeycomb acoustic metastructure

The ancient art of origami has inspired the design and fabrication of numerous acoustic and energy-absorption mechanical metamaterials and metastructures. This study introduces an origami-inspired honeycomb acoustic metastructure designed for engineering applications that demand both high impact resistance and effective sound absorption. This acoustic metastructure is formed by bonding a panel containing periodically distributed perforated holes and a panel without perforations to a periodical array of trapezoidal origami-bellow units. Acoustic wave propagation and drop-weight impact simulations are conducted to investigate the acoustic performance and low-velocity impact behavior of the metastructure. The results show that the origami-bellow honeycomb structure exhibits superior sound absorption capacity over two frequency ranges, outperforming the conventional honeycomb-core sandwich structure. Furthermore, it is shown that, in comparison with both the conventional hexagonal honeycomb-core and the Miura-ori foldcore sandwich structures, the proposed acoustic metastructure demonstrates higher levels of impact resistance and energy absorption capacity. We also show that the mechanical performance of the introduced metastructure under low-velocity impact loads can be further enhanced by increasing the story height of the origami-bellow units. Besides, the matrix material of the origami foldcore can be tailored to suit various scenarios, providing noise control and collision robustness for a diverse range of engineering applications.

Effect of Equation of State and Cutoff Density in Smoothed Particle Hydrodynamics Simulations of the Moon-forming Giant Impact

The amount of vapor in the impact-generated protolunar disk carries implications for the dynamics, devolatilization, and moderately volatile element isotope fractionation during lunar formation. The equation of state (EoS) used in simulations of the giant impact is required to calculate the vapor mass fraction (VMF) of the modeled protolunar disk. Recently, a new version of M-ANEOS (Stewart M-ANEOS) was released with an improved treatment of heat capacity and expanded experimental Hugoniot. Here, we compare this new M-ANEOS version with a previous version (N-SPH M-ANEOS) and assess the resulting differences in smoothed particle hydrodynamics (SPH) simulations. We find that Stewart M-ANEOS results in cooler disks with smaller values of VMF and in differences in disk mass that are dependent on the initial impact angle. We also assess the implications of the minimum “cutoff” density (ρ c ), similar to a maximum smoothing length, that is set as a fast-computing alternative to an iteratively calculated smoothing length. We find that the low particle resolution of the disk typically results in >40% of disk particles falling to ρ c , influencing the dynamical evolution and VMF of the disk. Our results show that the choice of EoS, ρ c , and particle resolution can cause the VMF and disk mass to vary by tens of percent. Moreover, small values of ρ c produce disks that are prone to numerical instability and artificial shocks. We recommend that future giant impact SPH studies review smoothing methods and ensure the thermodynamic stability of the disk over simulated time.

In-Silico Model Validation of Impact on a Composite Helmet Shell

Abstract Numerical impact simulation plays a critical role in the development and improvement of helmet systems. Due to the curvature of the helmet, the selection of impact position on the helmet may affect the ability to correlate results between numerical models and experimental results. In this study, high-velocity impact simulations were performed on composite plates, as well as a model of a modern composite helmet to validate helmet model performance. Results of the composite plate simulation show a non-converging increase in composite deformation with mesh refinement, indicating that model validation is a function of both material properties and mesh selection. Results of impact on the helmet model show that the calculated deformation of the helmet increases by up to 35% with a 20 mm change in impact position. The positional variation of helmet deformation is most pronounced on the front of the helmet. Due to the significant effect that impact position has on helmet deformation, the numerical model validation cannot be performed against experimental tests of a “small” sample size.

Simulation and analytical modeling of high-speed droplet impact onto a surface

The fluid dynamics of liquid droplet impact on surfaces hold significant relevance to various industrial applications. However, high impact velocities introduce compressible effects, leading to material erosion. A gap in understanding and modeling these effects has motivated this study. We simulated droplet impacts on solid surfaces and proposed a new analytical model for impact pressure and droplet turning line, targeting at predictions for enhanced cavitation. The highly compressed liquid behind the droplet expands sideways, causing lateral jetting. As the droplet encounters a shock wave, it reflects as a rarefaction wave, leading to low-pressure zones within the droplet. These zones converge at the droplet's center, causing cavitation, which, upon collapse, induces another shock wave, contributing to erosion. Using the well-established model for the low-velocity impact shows a significant discrepancy. Hence, an analytical model for the turning line radius is introduced, incorporating the lateral jetting's characteristic length scale. Comparing our model with existing ones, our new model exhibits superior predictive accuracy.

Analysis of Pluviograms Recorded in the Area of a Phosphogypsum Heap at Wiślinka, Poland

Abstract The paper is devoted to the long-term project concerning monitoring and stability analysis of a 40 m high phosphogypsum heap located at Wiślinka, Poland. The research presented in the paper focused on collecting and processing rainfall data, which subsequently allows us to perform numerical simulation of rainfall impact on heap’s behaviour. Such analysis requires time history of rainfall intensity, that is recorded by an automatic precipitation station. Since this is not common monitoring equipment, the characteristics of the station installed in the immediate vicinity of the heap are presented, and the data obtained in two experiments conducted in the laboratory are discussed. The analysis revealed that di erences between introduced and measured total rain are as large as 10% for very heavy rains. Moreover, the recorded maximum rainfall intensity often includes errors. The data processing procedure to obtain time history of rainfall intensity is presented on the basis of data collected in the first half of the hydrological year 2023 (the first period of the station’s operation). The total precipitation registered was 107 mm, and the maximum daily rain was only 26 mm. However, first single and multi-stage rainfall models for the Wiślinka region that would be applied into numerical simulations are presented.

Design optimization of anti-splashing targets and simulation of droplet impact on it

Natural surfaces have micro and nanostructures that affect the splashing behavior of water droplets falling on them. Synthetic surfaces mimicking this natural phenomenon have been previously reported. The objective of our current work is to design such surfaces and fine-tune the fluid splashing behavior using three-dimensional simulation tools. We have designed and simulated splashing behavior on geometrically patterned micro scale surfaces using the volume of fluid method within the commercial software Ansys Fluent. Surfaces with microscale pillars of different heights, geometrical shapes, layouts as well as tip designs were simulated with the goal of minimizing fluid splash. We found that certain pillar models produce less splashes than others. We have further optimized array structures for fluid splashing diameter and velocity. Behavior at different falling angles and fluid types are also investigated in multi-pillar models. The results indicate that a non-uniform structured surface decreases the speed and energy of the falling droplet. We have reported here three finalized designed models that are 35%, 63.5%, and 69% effective in reducing velocity compared to a flat surface model.

Numerical simulation of damage to the deformed state of the coating slab of a special structure

In this paper, we strived to the goal to ensure various special structures against damage factors of high-explosive blast. Together with application of combined blast protection devices, we considered reinforcement of constructive elements and simulated the impact and interaction of detonating projectile with reinforced concrete wall. Various packages of computational mechanics which belong to ANSYS family were applied to numerical simulations, as well as the developed numerical model of reinforced media which can be effective in development of combined blast-protective structures for urban environment. Protection devices based of developed blast-protective structures combine influence of blast-absorbing multiphase media with durability of rigid reinforced base constructions, so the numerical simulation of blast wave reflection and projectile impact are also necessary for their research and development. Our computational results, achieved in this study, have shown that, owing to reinforcement, the considered coating slab retained its integrity, though some cracking and ejection of concrete really occurred.

无人反潜平台空投入水冲击仿真分析

无人反潜平台空投入水冲击仿真分析