Impact Of Accidents Research Articles

Negative Effects of Unexpected Energy on Sequential Switching Shunt Regulator and Suppression Methods for High-Power Satellite

This paper deals with the negative effects produced by unexpected energy of solar array and methods of suppressing the effects for the sequential switching shunt regulator (S3R). The complex space operation conditions such as plasma environment and accidental impact are likely to cause abnormal discharge of solar array, leading to unexpected changes in the input energy of an S3R. Effects of unexpected energy on current stress and power loss of power devices, over-regulation of the S3R and quality of output voltage are represented and analyzed in this paper. A shunt regulator topology based on the switch current limiting drive (SCLSR) is then proposed to suppress current stress and power loss of power devices, thereby alleviating negative effects. Finally, simulation and experimental results are provided to illustrate the negative effects of unexpected energy and validate the proposed shunt regulator.

Impact-resistant design of RC slabs in nuclear power plant buildings

The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20–70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.

Quantitative Ground Risk Assessment for Urban Logistical Unmanned Aerial Vehicle (UAV) Based on Bayesian Network

The Unmanned Aerial Vehicle (UAV) has been used for the delivery of medical supplies in urban logistical distribution, due to its ability to reduce human contact during the global fight against COVID-19. However, due to the reliability of the UAV system and the complex and changeable operation scene and population distribution in the urban environment, a few ground-impact accidents have occurred and generated enormous risks to ground personnel. In order to reduce the risk of UAV ground-impact accidents in the urban logistical scene, failure causal factors, and failure modes were classified and summarized in the process of UAV operation based on the accumulated operation data of more than 20,000 flight hours. The risk assessment model based on the Bayesian network was built. According to the established network and the probability of failure causal factors, the probabilities of ground impact accidents and intermediate events under different working conditions were calculated, respectively. The posterior probability was carried out based on the network topology to deduce the main failure inducement of the accidents. Mitigation measures were established to achieve the equivalent safety level of manned aviation, aiming at the main causes of accidents. The results show that the safety risk of the UAV was reduced to 3.84 × 10−8 under the action of risk-mitigation measures.

Methodology for Assessing the Level of Threats when Using Small Arms against Unmanned Aerial Vehicles

The article considers a methodical approach to assessing the level of threat to the civilian population in the case of the use of small arms for shooting at unmanned aerial vehicles (UAVs). This approach is based on modeling the process of bullet flight in the vertical plane, based on the algorithm for determining the probability of accidental human impact, which allows, depending on the kinetic energy of the bullet, to calculate the probability of accidental death and probability of accidental injury. Based on the simulation, the indicators of the probability of human injuries depend on the angles of the shot, which allows to justify the restrictions when firing UAVs from small arms.

Experimental study on dynamic response of 6082-T6 aluminum alloy circular tubes under lateral low-velocity impact loading

Aluminum alloy components have been increasingly used in spatial structures in recent years for their advantages of high strength to mass ratio, great corrosion resistance, and low environmental pollution. In this study, impact tests on the 6082-T6 aluminum tube with circular hollow section were carried out to reveal its dynamic response under lateral impact loading, considering the accidental impact or terrorist attack that the aluminum alloy spatial structures may suffer. Four failure modes were observed from the test results, including “three plastic hinges” mode, crack at the impact position, crack at the support, and fracture at the support. The impact process was divided into four stages for the aluminum tubes without fracture: initial collision, coupling deformation, global deformation, and elastic recovery stages. Meanwhile, three stages including initial collision, coupling deformation, and failure stages were identified for the fractured tubes. The impact force, displacement, and surface strain were recorded and discussed in detail. Moreover, the impact energy transmitted to the aluminum tube was calculated based on the test results to investigate the energy absorption process of the tube under lateral impact loading. Finally, the influence of geometric parameter (section size and span of the tube), impact energy (initial impact velocity and hammer weight), impact position, and hammer shape on the dynamic behavior of the aluminum tube under lateral impact loading was analyzed based on the impact test results.

Energy absorption of discretely assembled composite self-locked systems

Impact accidents cause great damage to lives and devices due to strong destructiveness and weak predictability, and accordingly, flexibility and modifiability are essential in the design of novel impact-resistant structures. To achieve this goal, two newly-designed energy absorption systems were proposed in this paper, which could be discretely assembled without boundary constraints. Quasi-static experiments and finite element method (FEM) simulations were carried out to reveal the deformation mechanism and test the usability, based on which the analytical solutions of the crushing force of the models were established adopting plastic hinge analysis and energy method. Parametric study of multiple-tube systems was conducted to reveal the effects of foam porosity and inner tube parameters on dynamic response, and the optimal design was summarized, achieving the energy absorption efficiency of 39%. The functionally graded design of composite self-locked (CSL) systems was explored, and it was proven that the system with positive stiffness gradient was optimal.

Safety assessment of large-scale all steel LNG storage tanks under wind-borne missile impact

Regarding the disastrous consequences, the large-scale all steel liquefied natural gas (LAS-LNG) storage tank is regulated to be designed to resist the potential impact of wind-borne missiles. This paper aims to study the dynamic response and damage of LAS-LNG storage tanks subjected to the accidental typical wind-borne missile impact. Firstly, six Schedule 40 pipe and flange assembly missiles weigh 36.5 kg were designed according to the specifications of BS 7777 and RG 1.76. Based on the 300 mm-caliber single-stage gas gun, the impact test was conducted with a missile striking velocity of 50 m/s. The local deformation and global response of media-filled steel tanks were assessed experimentally. Then, the commercial finite element (FE) program LS-DYNA was utilized to perform the numerical simulations considering the fluid–structure interactions. The adopted numerical algorithm, constitutive models and the corresponding parameters were validated by comparing with the test data. Finally, based on the validated finite element analyses approach, regarding the design-basis wind-borne missiles specified by the regulatory guide of U.S. Nuclear Regulatory Commission and American Nuclear Society, i.e., RG 1.76, RG 1.221 and ANSI/ANS-2.3-2011, the damage levels of the prototype Chinese Yuhuan LAS-LNG storage tank under wind-borne missile impact were assessed numerically. It indicates that the filled media in the tank would provide additional resistance to the missile impact, the present three design-basis wind-borne missiles could bring certain damage to the outer tank of the Yuhuan LNG storage, but the safety of the inner tank can be guaranteed.

Extra-axial haemorrhages in young children with skull fractures: abuse or accident?

ObjectiveInfant and toddler subdural haemorrhages (SDH) are often considered indicative of abuse or major trauma. However, accidental impact events, such as falls, cause contact extra-axial haemorrhages (EAHs). The current study...

EFEKTIFITAS PENERAPAN TILANG ELEKTRONIK TERHADAP PELANGGARAN LALU LINTAS DI WILAYAH HUKUM POLDA METRO JAYA

The use of motorized vehicles in everyday life can have a negative impact, namely congestion and traffic accidents resulting from traffic violations so that it requires law enforcement efforts which are currently using electronic ticketing, but it can become aproblem if the motorized vehicle involved in traffic violations has change ownership or be driven by someone else. This research is anempirical juridical study using a case approach. Data collection techniques through field research. The results showed that the effectiveness of the application of electronic ticketing against traffic violations in the jurisdiction of Polda Metro Jaya has notbeen maximal in overcoming traffic violations because the ETLE camera can only detect certain types of violations. Factors thataffect the effectiveness of the application of Electronic Tickets are legal substance factors that have not been regulated in the Chief of Police Regulation, law enforcement factors, facilities or facilities factors, community legal culture factors, and natural or environmental factors.

A Progressive Damage Modelling of Glass/Epoxy Cylindrical Structure Subjected to Low-Velocity Impact

Due to the harshness and unpredictability of the tidal site environment, the damage induced by an accidental impact should be considered in the certification of composite cylindrical structures intended to be used in the design of the composite MJM tidal turbine concept. The first part of this paper deals with the effect of different failure criteria based on quadratic stress functions on the low-velocity impact response of thick filament wound glass/epoxy cylindrical structures. A user-defined material model (VUMAT) applied to three-dimensional solid elements was implemented into the finite element software Abaqus-Explicit to explore the effect of failure criteria on the predicted dynamic response with intralaminar damage. The investigated failure criteria include the two-dimensional Hashin criteria presented by Hashin in 1973 and extended to the three-dimensional case by including analytically the out-of-plane stress terms (criteria denoted “Hashin 3D”), the three-dimensional Hashin criteria described by Hashin in 1980 (criteria denoted “Hashin 3D 1980”), the Puck matrix transverse criterion coupled to Hashin criteria (criteria denoted “Hashin-Puck”) and Chang-Chang criteria (criteria denoted “Chang & Chang 1987”). The intralaminar damage model includes damage onset based on quadratic failure criteria, damage evolution, and element deletion from the solid mesh. FEA analyses are carried out with different low-level impact energies. The numerical results show different impact responses as well as the damage characteristics particularly the matrix cracking through the thickness. In the second part the bilinear cohesive zone model (CZM) is employed for modelling the interlaminar damage. The combination of the intralaminar damage model with the interlaminar model is applied using an uncoupled methodology. By comparison with the experimental force–time curves, interface properties used in the cohesive model have been estimated numerically using a reverse methodology and a baseline FEA model. The modelling approach has proven to be capable of reproducing experimental results with good accuracy. The modelling outcomes and predicted damage are therefore intended to be applied in the design loop and development of the MJM tidal turbine prototype where thick filament wound glass/epoxy cylinders are subjected to low-velocity stones impact.

1971年近畿日本鉄道大阪線正面衝突事故をめぐる地理的基底要因

自然災害に比較して地理的基底要因への注目の少ない重大鉄道事故について，1971年近畿日本鉄道大阪線での正面衝突事故を例として5つの論点から分析した．その結果，事故現場がトンネル掘削技術と経費削減のため山間急勾配を受容して建設されたこと，勾配区間に上り列車優先で垣内信号所を特設したこと，同所の保安設備が下り列車に対して貧弱であったことが明らかになった．そして事故区間は，当該線開通が周辺村落の寒村化を促して非常時の連絡手段に乏しく，また平時から集落と鉄道との稀薄な関係が救助活動の遅れを生んだことも解明できた．

Computational assessment of nitrogen-enriched, stable and insensitive tris(1,2,4,5-tetrazin-3-yl)amine building block for energetic applications

In this work, we report an approach for designing a series of energetic compounds derived from nitrogen-rich tris(1,2,4,5-tetrazin-3-yl)amine backbone. Based on available synthetic method, nitrogen content (70.8%), heat of formation (1371 ​kJ·mol-1), density (1.67 ​g·cm-3), detonation parameters (7.75 ​km·s-1, 24.30 ​GPa), and experimentally reported high decomposition temperature (231 ​°C), less sensitivity to accidental impact (42 ​J) and friction (360 ​N) data, tris(1,2,4,5-tetrazin-3-yl)amine found to be an efficient building block for designing energetic materials. The explosophoric functional groups –NO2, –NH2, –ONO2, –NHNO2, and N3 were introduced in the tris(1,2,4,5-tetrazin-3-yl)amine framework to further improve energetic properties. All tris(1,2,4,5-tetrazin-3-yl)amine derivatives have a much higher heat of formation than TNT (2,4,6-trinitrotoluene) and RDX (1,3,5-trinitro-1,3,5-triazinane). Crucially, higher detonation velocities (>9.10 ​km·s-1) and detonation pressures (>35.20 ​GPa) were calculated for –NO2, –ONO2, and –NHNO2 substituted compounds compared to RDX. Considering the experimental and computed stability of tris(1,2,4,5-tetrazin-3-yl)amine towards high temperatures and mechanical stimuli, the entire designed molecules are expected to be less sensitive and stable for energetic applications. These advantages make tris(1,2,4,5-tetrazin-3-yl)amine an effective building block. There is no denying that the insertion of energetic functional groups will undoubtedly benefit the development of secondary explosives and propellants.

Unsupervised learning-driven intelligent fault diagnosis algorithm for high-end bearing

<p indent="0mm">Spectral kurtosis is an effective method for rolling bearing fault diagnosis. However, it is highly sensitive to common accidental impact features in engineering, which frequently leads to feature extraction failure. To solve this problem, a robust evaluation method based on unsupervised learning is proposed to calculate the kurtosis of time series under the interference of multiple sporadic impulses (MSIs). First, dynamic signal samples are divided into equal intervals according to the characteristics of high energy concentration in the time domain. Second, each block is mapped to statistical parameter feature space (SPFS). Third, based on the significant statistical difference between MSI and other components in SPFS, an isolated 2-means clustering algorithm is proposed that realizes the self-location of clustering center and self-adaptive adjustment of clustering number and identifies and suppresses blocks receiving interference in the signal step by step. Finally, kurtosis information fusion is performed for the remaining samples, excluding MSI interference. A new method for high-end bearing fault diagnosis is proposed, which is combined with the robust kurtosis evaluation method and the multi-scale decomposition method. Through simulations and actual bearing fault diagnosis, it is verified that the method can accurately extract abnormal fault features under the adverse effects of multicomponent coupling and multiple accidental impact interference and can consider intelligence, high robustness, and high computational efficiency in applications.

Impact resistance and energy absorption ability of bio-mimetic thin-walled structures with hollow columns under impact loading

With the increasing damage of lives and properties caused by impact accidents, thin-walled tubes have been widely employed to make energy-absorbing structures in the field of automotive engineering due to their lightweight and energy absorption ability. In this work, we proposed three kinds of thin-walled bio-mimetic tubes inspired by horsetail plants and investigated the energy absorption abilities of the above structures with hollow columns under impact loading by means of the finite-element method. The effect of three factors, including column diameter, wall thickness, and impact angle, on the energy absorption characteristics of the bio-mimetic structure, is discussed. The primary outcome of this research is a design method for the use of thin-walled multi-cell tubes for an energy absorption device where impact loading is expected. It was also found that the energy absorption performances of the hexagonal structures are better than that of the triangular and quadrilateral ones. Moreover, the results revealed that the absorbed energy by thin-walled bio-mimetic structures shows more dependence on the impact angle than on the wall thickness of the tube.

Numerical simulations of nuclear fuel reprocessing plant subjected to the free drop impact of spent fuel cask and fuel assembly

This paper aims to numerically evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA). Based on our recently conducted 1/3 scaled free drop test of SFC, the adopted numerical algorithms, constitutive models and parameters are verified and further applied to the refined numerical simulations of the prototype plant under accidental impact. Total nine free drop scenarios are considered, including the SFC drop onto the center of the removable slab, groove of the removable slab and center of the inverted U-shaped slab/autoclaved aerated concrete (AAC) composite protective structure as well as the FA drop onto the center of the bottom slab in spent fuel pool. The damage and vibrations of nuclear fuel reprocessing plant, as well as the energy absorption capacities of the trailer, AAC blocks layer, waterproof steel liner and water within the loading shaft are assessed. It indicates that, (i) the free drop impact of SFC results in perforation of the impacted region and extensive damage of the removable slab, while the free drop impact of FA only induces a shallow cratering of the bottom slab in spent fuel pool; (ii) the trailer absorbs about 90% of the impact energy and reduce the damage of the impact region effectively, but the overturn of which may result in the tip-over impact of SFC on the surrounding walls; (iii) when considering the effects of the waterproof steel liner and water within the loading shaft, the impact energy of SFC reduces by at least 54%, and the bottom slab is effectively protected; (iv) the vibrations caused by the impact of FA are slighter than that caused by the impact of SFC, and the trailer reduces the peak accelerations of nuclear fuel reprocessing plant by 26.3%–68.91%.

Design optimization of a novel negative Poisson's ratio non-module battery pack system considering crashworthiness and heat dissipation

Considering volumetric energy density (VED), crashworthiness and heat dissipation, this paper explores a novel battery pack system containing a non-module battery pack (cells to pack, CTP) and two negative Poisson's ratio (NPR) tubular structures. The CTP is designed to maximize the battery pack's VED by removing the module components and assembling the large-size battery cells into the pack. On this basis, the NPR tubular structures consisting of NPR anti-collision block and NPR radiator are installed on both sides of the CTP to meet the crashworthiness and heat dissipation requirements. In detail, the NPR anti-collision block is employed to protect the NPR-CTP system in side pole impact accident, and the NPR radiator filled with cooling water can dissipate heat with outside air. Furthermore, a many-objective optimization methodology integrating an improved radial basis function (PSO-RBF) neural network model and the third-generation nondominant sorting genetic algorithm (NSGA-III) is used to search the optimized NPR-CTP system. The results show that the initial NPR-CTP system has better crashworthiness and heat dissipation than the other CTP systems, and the comprehensive performance of the optimized NPR-CTP system has been effectively strengthened.

Finite Element Analysis of Impact-Induced Damage in Pressurized Hybrid Composites Pipes

The high mechanical performance of filament wound hybrid composite pipes can be adversely affected by their low resistance to accidental impact. Loads of dynamic origin are dangerous and cause consequences on the operation of pipes because the damage is often not detected and can affect the structural integrity of composite pipes. In this work, a finite element (FE) model of pressurized hybrid composite pipe is developed and performed to predict the damage initiation and evolution under low-velocity impact through simulations with ABAQUS/Explicit. Hashin’s failure theory is used as failure criterion. At the first stage, load–time histories, and impactor displacement time limits are estimated in an FE model. The numerical results are confronted with the experimental values published in the literature. Once the model was validated, damage initiation and propagation were analyzed, where it is observed that damage mainly occurs by matrix cracking, damage evolution in the matrix in tension, compression and shear are presented and discussed in detail.

Evaluation of Head Injury Criteria for Injury Prediction Effectiveness: Computational Reconstruction of Real-World Vulnerable Road User Impact Accidents.

This study evaluates the effectiveness of various widely used head injury criteria (HICs) in predicting vulnerable road user (VRU) head injuries due to road traffic accidents. Thirty-one real-world car-to-VRU impact accident cases with detailed head injury records were collected and replicated through the computational biomechanics method; head injuries observed in the analyzed accidents were reconstructed by using a finite element (FE)-multibody (MB) coupled pedestrian model [including the Total Human Model for Safety (THUMS) head–neck FE model and the remaining body segments of TNO MB pedestrian model], which was developed and validated in our previous study. Various typical HICs were used to predict head injuries in all accident cases. Pearson’s correlation coefficient analysis method was adopted to investigate the correlation between head kinematics-based injury criteria and the actual head injury of VRU; the effectiveness of brain deformation-based injury criteria in predicting typical brain injuries [such as diffuse axonal injury diffuse axonal injury (DAI) and contusion] was assessed by using head injury risk curves reported in the literature. Results showed that for head kinematics-based injury criteria, the most widely used HICs and head impact power (HIP) can accurately and effectively predict head injury, whereas for brain deformation-based injury criteria, the maximum principal strain (MPS) behaves better than cumulative strain damage measure (CSDM0.15 and CSDM0.25) in predicting the possibility of DAI. In comparison with the dilatation damage measure (DDM), MPS seems to better predict the risk of brain contusion.

NUMERICAL ESTIMATION OF DAMAGE CAUSED BY THE IMPACT OF AN EXERCISE TORPEDO ON A SUBMARINE PRESSURE HULL STRUCTURE

Torpedo combat and evasion training exercises using trials torpedoes are valuable but involve significant risks to the target submarine in the event of an accidental impact. This paper presents a study of impacts of a nominal heavyweight torpedo against a nominal submarine pressure hull, simulated using the nonlinear explicit finite element analysis code LS-Dyna. The model is validated against experimental work published by the Australian Defence Science and Technology Organisation, then expanded to a segment of a full-size submarine. Impacts were simulated at torpedo speeds of 30, 40 and 50 knots. It was found that the 30 knot impact produced no plastic deformation in the pressure hull, while the 40 and 50 knot impacts produced permanent dents of several mm depth. Reference is made to DNV GL submarine structures rules to suggest that these dents will not impair operational capability.

Crashworthiness design of car threshold based on aluminium foam sandwich structure

During a side impact accident of an automobile, the automobile threshold plays an important role in maintaining the living space of passengers, and thus the crashworthiness design of thresholds may effectively improve the crash safety of the car. Inspired by the excellent load carrying and energy absorption capacity of foam-filled double tubes, a sandwich threshold which is composed of an original threshold, an aluminium foam and a square tube was proposed. Finite element simulation was carried out to study the three-point bending behaviour of sandwich thresholds and the influence of the tube shape on the bending resistance of sandwich thresholds. The results show that the bending capacity of sandwich thresholds first increases and then decreases with the increase of the outer length of the square tube. The average bending capacity of the sandwich threshold can be increased by 185%, while the filling mass is only 17.2% of the original threshold. Besides, the filling scheme of foam in corners was introduced to realise the lightweight design, which not only ensures the improvement of the bending resistance of the filled threshold but also greatly reduces the mass of the filling structure. The three-point bending experiments were also performed to test the foam corner-filled threshold. Finally, through the vehicle side pole impact simulation using the component modelling method, it is verified that the sandwich and foam corner-filled threshold can effectively improve the crashworthiness of the car.