Explosive Impact Research Articles

Explosively welded SLM-AlSi10Mg/SLM-SUS316L: Unveiling superiority of interlayer welding for enhanced mechanical properties

Following the advent of three-dimensional (3D) printing technology, multi-material 3D printing has garnered significant attention due to its potential to enhance the flexibility and development of high-performance 3D printing materials. This study investigated the application of explosive welding to create multi-material 3D printed structures. Specifically, we explored the use of direct and interlayer explosive welding to fabricate SLM-AlSi10Mg/SLM-SUS316L explosive composites with the aim of further improving material properties. Our primary objective was to explore the unique interfaces and mechanical characteristics of 3D printed materials subjected to explosive impact loading. This study provides a new idea of 3D printing multi-materials, which is of great significance for the development of both explosive welding and 3D printing. The results demonstrated the feasibility of using explosive welding to create multi-material composites from 3D printed metals, including both direct and interlayer welding of SLM-AlSi10Mg/SLM-SUS316L. Interlayer welding exhibited superior mechanical performance compared to direct welding, with a 70%–250% increase in strength observed in the macro tensile shear test. Additionally, samples fabricated with a 40 mm explosive thickness displayed more stable and exceptional performance in the micro tensile test. Corrosion testing and X-ray computed tomography (XCT) analysis were employed to investigate the distribution of pores within the 3D printed materials.

Dynamic response of UHMWPE/polyurea composite plates under combined blast and ballistic impact

Combined load caused by blast impulse and fragmentation impact poses a synergetic damage threat to the protective structure. To improve the blast and ballistic impact resistance of Ultra-high molecular weight polyethylene (UHMWPE), polyurea coated Ultra-high molecular weight polyethylene structure was proposed, and the composite structures with different coating thickness and coating position were prepared. Composite projectiles formed by combining foam projectiles and steel projectiles were launched by light gas gun to simulate the combined load of explosion impact and fragmentation. Comparative experimental studies were carried out. The experimental results show that the polyurea layer has good elastic properties, preventing the excessive deformation of the PE layer. The polyurea coating position and the time interval of the combined load show significant influence on the impact resistance of the composite structure. When the load was relatively low, PE plate with polyurea coating on booth face has both the advantages of PE plate with coating on the front and back face, but when the load increased, the impact resistance potential of polyurea layer was not fully developed. With the increase of the combined load, structures with polyurea coating on the back face has a good resistance of combined impact.

A Positioning Alarm System for Explosive Impact Debris Protective Suit Based on an Accelerometer Array.

Protection suits are vital for firefighters' safety. Traditional protection suits physically protect firemen from burns, but cannot locate the position of bodily injuries caused by impact debris. Herein, we present a wearable impact debris positioning system for firefighter protection suits based on an accelerometer array. Wearable piezoelectric accelerometers are distributed regularly on the suit to detect the vibration on different body parts, which is conducive to determining the position of injured body parts. In addition, the injured parts can be displayed on a dummy body model on the upper computer with a higher localization accuracy of 4 cm. The positioning alarm system has a rapid response time of 0.11 ms, attributed to the smart signal processing method. This work provides a reliable and smart method for locating and assessing the position of bodily injuries caused by impact debris, which is significant because it enables fire commanders to rescue injured firefighters in time.

Methane plume detection after the 2022 Nord Stream pipeline explosion in the Baltic Sea

On September 26th, 2022, the detonations at the gas pipelines Nord Stream 1 and 2 resulted in some of the largest non-natural releases of methane known. The distribution of methane in the surrounding seawater and the possible effects were not apparent. To trace the pathways of methane we recorded CH4 concentrations and the isotopic signal (δ13C-CH4) in seawater, and air. A week post-explosion, we detected methane concentrations up to 4 orders of magnitude above the natural Baltic Sea background. The released fossil methane created a distinct plume with δ13C-CH4 ratios differing from natural background values. The strong water stratification preserved the distribution pattern initiated by the explosion, shown by the laterally strong concentration gradient within the plume. Our analysis encompasses three stages of the explosion's impact; the initial sea-air methane release, measurements taken during our research expedition one week later, and a third stage triggered by the shift from summer to winter conditions as an outlook on how winter mixing and microbial activity will influence the plume.

Analysis of the Impact Resistance Characteristics of a Power Propulsion Shaft System Containing a High-Elasticity Coupling

In research concerning the impact resistance characteristics of ship power transmission shaft systems incorporating a high-elasticity coupling, a significant challenge lies in ascertaining the displacement compensation metrics for the high-elasticity coupling. This study constructs a finite element model of the ship power transmission shaft system with an entity equivalent model of the high-elasticity coupling. Utilizing the Dynamic Design Analysis Method (DDAM) and the time-history method, the dynamic responses of the high-elasticity coupling, the propulsion shaft system, and its critical cross-sections under explosive impact loads are analyzed. The findings indicate that the maximum impact displacement of the propulsion shafting system, as calculated by DDAM, is 22.47 mm in the vertical direction at the driven end of the high-elasticity coupling. In contrast, the maximum impact displacement determined by the time-history method is 15.23 mm in the same direction. The study corroborates the precision of the high-elasticity coupling equivalent model establishment methodology and confirms that the entity equivalent model of the power transmission shaft system with a high-elasticity coupling is capable of fulfilling the criteria for a swift evaluation of impact resistance characteristics. This provides theoretical backing for the forecasting of impact resistance performance in ship propulsion shaft systems.

Study on explosion impact pressure and damage distribution law of rock powder segmented charge

The charge structure is the critical to determine the bench blasting effect of rock slope. Through theoretical calculation, model testing, and numerical simulation, a formula for calculating the stress attenuation of the axial hole wall of the segmented charging structure is proposed. Moreover, the influence mechanism of the explosive ratio and interval packing length on the internal damage distribution of the concrete of concrete specimens under a segmented charging structure of the cuttings is described. Finally, the research results are applied to the mining of a rock slope in southwest China. The research results reveal the following: 1) The pressure at the charge section is highest when the rock debris interval charge is used, and with the increase in the charge section distance, the pressure markedly decreases—sharply first before stabilizing. In the upper filling interval charge section, the minimum pressure corresponded to approximately the midway point of the filling section, and the stress distribution on the axial hole wall is concave: high at both ends and low in the middle. 2) The ratio of the upper and lower sections of the explosive column determines the form of blasting damage, and the range of blasting damage increases first and then decreases with the increase in the length of the rock debris in the interval section. 3) The field test shows that compared with the traditional blasting charge structure, the optimized segmented charge structure can reduce the blasting block rate by 13.1%. 4) Using the optimized charge structure, the explosive unit consumption can be decreased from 0.27 kg/m3 to 0.24 kg/m3, which improves the economic benefits of mining and construction of related mines.

Simulation Study of Crack Extension in Concrete Blast Walls Under Blast Impacts

To study the crack propagation law of concrete blast wall (CBW) under explosion impact, this paper uses ANSYS/LS-DYNA finite element software to numerically simulate the crack growth law under the influence of different explosion loads and explosion distances. The results show that: after the explosion, the change of composite velocity of each measuring point on the wall at a certain distance from the explosion point is mainly divided into three stages: explosive initiation stage, the composite velocity and acceleration of each measuring point are zero; In the accelerated crack growth stage, the acceleration of each measuring point reaches the peak value; At the stage of uniform crack growth, the crack will no longer accelerate its diffusion. When the explosion distance is fixed, the explosion load is positively correlated with the number of radial cracks; When the explosion load is small, there are only inconspicuous circumferential cracks in the center of the wall. When TNT equivalent is 15g, 25g, and 30g, CBW circumferential cracks increase and mainly concentrate in the center, and gradually expand outward to the boundary in the form of concentric circles. At the same time, when the explosion load is constant, the explosion distance is negatively related to the number of cracks, mainly radial cracks, while circumferential cracks are always distributed in the center of the wall. In the range of simulated explosion distance, the cracks only appear at the boundary and gradually change from square to round with the increase of explosion distance, and the crack area decreases. The research results can provide a theoretical basis for avoiding such accidents and a powerful reference for accident investigators to determine the location and intensity of explosion sources.

Evaluation of mental load using EEG and eye movement characteristics

Mental load is a major cause of human-induced accidents. In this study, an explosive impact sensitivity experiment was used to induce mental load. A combination of subjective questionnaires and objective prospective time-distance tests were used to judge whether subjects experienced mental load. Four indicators, namely, β, γ, mean pupil diameter, and fixation time were selected by statistical analysis and PCA for the construction of a mental load assessment model. The study found that the occipital lobe was the most sensitive to mental load, especially β and γ bands. Lastly, it was found that subjects showed different degrees of mental load for the same mental load induction task. The results of the study are applicable to the evaluation and monitoring of the mental characteristics of workers and provide a scientific basis for adjusting the mental load of workers over time to reduce the rate of accidents and enhance production efficiency.

Improving the Quality of Laser Drilling by Assisted Process Methods of Static Solution and Mist Blowing.

The use of static solution-assisted laser drilling can effectively improve hole roundness, decrease taper angle, and reduce recast layer thickness and hole wall slag adhesion. However, the enormous energy of the laser will evaporate the solution to form a suspension droplet and reduce the quality and efficiency of laser drilling. To deal with this defect, the mist-blowing method was used to reduce the influence of droplets on the taper angle and recast layer. In this work, the effect of wind speed on drilling quality was examined, and laser drilling in air, water, and NaCl solution was carried out to analyse the effect of solution composition on hole wall morphology. The results showed that a speed fan with a proper wind speed that disperses the droplets formed in the processing area can significantly reduce the refraction and scattering of the laser, and the taper angle and roundness of the drilling hole were also reduced by 15.6% and improved by 2.4%, respectively, under the wind speed of 2 m/s. The hole wall morphology showed a thicker recast layer and cracking in air, while it was thinner in water and there was little or no layer in the NaCl solution in the same current. When drilling in NaCl, the taper angle and roundness of the drilling hole were reduced by 4.13% and improved by 2.11%, respectively, compared to water. Due to the mechanical effect of the laser in the NaCl solution, the impact force on the material was much greater than that in water. The solution cavitation effect, generated by the absorption of laser energy, caused an explosive impact on the molten material adhered to the surface of the hole wall. Above all, drilling in the NaCl solution with a current of 200 A and a wind speed of 2 m/s was the optimal condition for obtaining the best processing quality.

Effect of explosion impact on the electrical performance and appearance of lithium-ion battery

In this work, the effect of the overpressure and incidence angle of shock waves on lithium-ion battery with various states of charge was studied, and the changes of electrical performance and appearance were measured accordingly. The result shows that the compression from shock wave can lead to the voltage going up and the internal resistance and capacity down; the elevated magnitude of the lithium-ion battery voltage goes up with the state of charge decreasing; the voltage increases and the internal resistance decreases with the overpressure increasing; the magnitude of battery capacity descent depends significantly on the severity of rupture disk cracking, and the capacity declines drastically corresponding to the complete failure of rupture disk; the cracked severity of rupture disk from oblique compression displays more than that from horizontal impact of shock wave; compared to 37Ah batteries, 50Ah batteries have higher safety valve damage thresholds and destruction thresholds, but are more prone to bulging. The conclusions will be of value to the establishment of safety standards for lithium-ion battery.

Research on the blockage effect in a shock tube

The shock tube is a crucial experimental apparatus in the field of explosive impact. Limited research has been conducted on the visualization of the internal flow field in shock tubes under blockage conditions, and there is a lack of comprehensive understanding of the mechanisms behind blockage effects. This paper presents experimental and numerical investigations into the propagation of shock waves inside a shock tube and their interaction with obstructive elements. Blockage effect experiments were conducted on a shock tube test platform, where pressure data were obtained through a pressure monitoring system. Additionally, schlieren imaging technology was employed to visualize the evolution of shock wave fronts. A two-dimensional numerical model of the shock tube was established using Fluent software, and the computed results exhibited excellent agreement with the experimental data, confirming the accuracy of the numerical model. The mechanism of the blockage effect was revealed through analysis of pressure-time curves and images depicting the evolution of shock wave fronts. Furthermore, adjustments to parameters on the validated numerical model allowed for analysis and comparison of different blockage ratios. The results indicate that the disturbance to the flow field caused by the blockage effect is primarily due to the reflection of shock waves between the front surface of the obstructive element and the shock tube wall. This reflection leads to differences in pressure curves compared to free-field conditions, and such differences increase with higher blockage ratios.

Decision‐making analysis in post‐fire and explosion aftermath assessment tool: A fuzzy cognitive mapping approach

AbstractThis assessment tool was created to generate a decision‐making support system and assessment approach for a post‐fire (aftermath) and blast explosion impact. It uses a multidecision analysis neural network. Multidecision analysis is very crucial as the judgment of the assessment relies not only on engineering input but also on many contributing factors, such as lead time for replacement. This article outlines the framework for post‐incident explosion and fire‐damaged assessment using evaluation acceptance criteria and judgment that streamlines the process. Grounded theory (GT) and fuzzy cognitive mapping (FCM) techniques are presented and evaluated. Overall, this study aims to develop how the project organizations can ensure safety and asset integrity decision‐making by identifying hindrances and later developing a multicriteria analysis framework for the post‐incident assessment phase of implementation.

Assessing Feed-Forward Backpropagation Artificial Neural Networks for Strain-Rate-Sensitive Mechanical Modeling.

The manufacturing processes and design of metal and alloy products can be performed over a wide range of strain rates and temperatures. To design and optimize these processes using computational mechanics tools, the selection and calibration of the constitutive models is critical. In the case of hazardous and explosive impact loads, it is not always possible to test material properties. For this purpose, this paper assesses the efficiency and the accuracy of different architectures of ANNs for the identification of the Johnson-Cook material model parameters. The implemented computational tool of an ANN-based parameter identification strategy provides adequate results in a range of strain rates required for general manufacturing and product design applications. Four ANN architectures are studied to find the most suitable configuration for a reduced amount of experimental data, particularly for cases where high-impact testing is constrained. The different ANN structures are evaluated based on the model's predictive capability, revealing that the perceptron-based network of 66 inputs and one hidden layer of 30 neurons provides the highest prediction accuracy of the effective flow stress-strain behavior of Ti64 alloy and three virtual materials.

Impact of the 4th of August Beirut explosion mass casualty incident on a university hospital microbial Flora

BackgroundFollowing the Beirut explosion, our university hospital received at least 350 casualties. Subsequently, infection control standard practices were compromised. Concerns for Multi-Drug Resistant Organisms (MDROs) infections in injured patients and a resulting hospital outbreak were raised. The objectives of the study were to compare the rate of hospital growing MDROs 6 months before and 6 months after the Beirut explosion, to identify emerging microorganisms and to evaluate the change in surgical infection prevention practices.MethodsThis is a retrospective chart review of patients with hospital acquired infections (HAI) admitted to the hospital before and after the Beirut explosion. The study was conducted between February 4, 2020 and January 4, 2021. Excluded patients were those transferred from other hospitals and those with community acquired infections. The primary outcome was to identify the rate of growing MDROs post explosion. The secondary outcomes were identifying antibiotics used for surgical prophylaxis in patients requiring surgeries and patients diagnosed with a HAI. Therefore, patients were divided in three groups. Control group included patients admitted with explosion-related injuries on that same day. Patients admitted and between February 4 and August 4 and diagnosed with HAI were compared to those admitted post August 4 with explosion-related HAI and to patients diagnosed with non-explosion-related HAI between August 4 and January 4, 2021. An estimated rate of 18-22% MDRO was needed to achieve a statistical significance with 80% power and 0.05 α. Pearson Chi square test was used to analyze the primary outcome.ResultsA total of 82 patients with 150 cultures were included in this study. Data showed an increase in the rate of MDRO after the explosion with 37.1% of the cultures taken before the explosion and 53.1% after the explosion (p = 0.05). When comparing the types of HAI in both groups, culture sites were significantly different between pre- and post-explosion patients (p = 0.013). However, both groups had similar types of microbes (p = 0.996) with an increase in candida related infections.ConclusionThese findings confirmed that the Beirut explosion impact on antimicrobial resistance was similar to combat zone incidence, where an increase in MDROs rate such as Escherichia coli (E.Coli) and Stenotrophomonas maltophilia, in addition to the increase in candida related infections.

Efficiency and seismic safety of constructing underground structures in complex rock masses

Purpose. To develop new resource-saving method of underground construction and evaluate how effective it is, to set thresholds for safe seismic ground vibrations which accompany explosions during breaking in mine workings. Methodology. The work used method of analysing mining and geological conditions of workings, field surveys of rock conditions in face, experiments are conducted on rock samples taken from blasting sites, more detailed data are obtained on rock properties, type and direction of development of crack systems along the workings cross-section by funneling method and approved research methods in accordance with current State Standards. Findings. Research has been carried out to determine main features of physical and mechanical properties of rocks, fracture and tectonic structure of rock mass and development of fracture systems. According to the results of ejection funnel parameters, the anisotropy coefficient was calculated, and according to data on identification of crack systems and their density, fracture coefficient was calculated. The experimental data obtained were used to adjust rational distances between contour boreholes and along the entire cross-section of working face. Based on corrected drilling and blasting operations (DBO), experimental explosions were carried out in workings. It was established that the borehole utilisation rate (BUR) was 0.95–0.97, uniformity of rock mass crushing was achieved, and explosive material consumption was reduced by 10–15 %. Instrumental measurements of explosion impact in workings proved seismic ground vibrations at protected facilities amounted to 0.4 cm/s with a duration of 0.05 s, which did not exceed the State Standard. Originality. Optimal DBO parameters are substantiated based on changes in numerical parameters of anisotropy and fracture coefficient, as well as radius of fracture zone along the cross-section of working face. The idea of forming a shielding zone along the contour of workings with explosive charges having an elongated symmetrical cut was confirmed and technically implemented. Practical value. Laboratory and field research results are fundamental for designing borehole layouts along workings and refer to major initial data used to justify design parameters of blasting chart.

Gas explosion impact behavior and disaster analysis based on structural failure: Numerical modeling

For gas leakage explosion accidents that occur in high blockage environments, the failure of building structures often leads to the evolution of explosion waves becoming unpredictable, resulting in the amplification of accident consequences. In this paper, a severe gas leakage and explosion accident in Beijing is analyzed using computational fluid dynamics (CFD) method, and the disasters of the accident are evaluated based on the evolution of physical quantities. The laws of propagation and impact damage of explosion waves based on structural failure are also summarized. Based on the numerical analysis results, the explosion of 4.0–4.1 m3 combustible gas is sufficient to destroy a large number of walls with a maximum indoor overpressure of 1.130 bar and create a high-pressure injury area of 10 m and a high-temperature injury area of 14 m outdoors. The impact behaviours of explosion waves are closely related to the building structures and obstacle characteristics. Structures whose spatial direction is the same as the propagation direction of the initial wave suffer less damage, and similar obstacle characteristics on both sides of structures reduce damage. The disorder of gas explosion intensity leads to the unpredictable failure direction and process of building structures, and the collapse direction of component may be opposite to the path of initial explosion wave; Outdoors, the gas flow rate of several hundred meters and the peak dynamic pressure of 0.5 bar caused all the glass of two buildings to break. Therefore, a reasonable pressure relief area and sufficient safety distance become the key measures to prevent and mitigate the disaster of civil explosion accidents. The research results can provide scientific basis for the investigation and loss prevention of explosion accidents, as well as safety assessments in the process industries.

Study on damage of the macrostructure of the cochlea under the impact load.

Due to the tiny and delicate structure of the cochlea, the auditory system is the most sensitive to explosion impact damage. After being damaged by the explosion impact wave, it usually causes long-term deafness, tinnitus, and other symptoms. To better understand the influence of impact load on the cochlea and basilar membrane (BM), a three-dimensional (3D) fluid-solid coupling finite element model was developed. This model accurately reflects the actual spatial spiral shape of the human cochlea, as well as the lymph environment and biological materials. Based on verifying the reliability of the model, the curve of impact load-amplitude response was obtained, and damage of impact load on the cochlea and the key macrostructure-BM was analyzed. The results indicate that impact wave at middle frequency has widest influence on the cochlea. Furthermore, impact loading causes tears in the BM and destroys the cochlear frequency selectivity.

Study on steel fiber synergistically reinforced cellular concrete explosion‐proof effect in an underwater near‐field environment

AbstractBased on the static and dynamic test results of steel fiber synergistically reinforced cellular concrete (SFSRCC) under a complex stress state, the yield surface equation and strain rate effect are modified to construct a modified Holmquist–Johnson–Cook (HJC) model suitable for the dynamic compression behavior characteristics of SFSRCC, and the modified HJC model is verified. At the same time, a finite width SFSRCC protective layer–roller compacted concrete (RCC) slab–water–explosive multimedia coupling model is established to explore the influence of setting different thicknesses of the SFSRCC protective layer (0, 0.1, 0.2, and 0.3 m) on the explosion‐proof performance and effect of the RCC slab structure. The results show that the heavy stress–strain curves and dynamic failure modes of the SFSRCC under different strain rates are in good agreement with the experimental results. The maximum errors of peak stress and peak strain between the simulation results and the experimental results are 1.04% and 6.6%, respectively, which confirms the validity of the HJC correction model and the accuracy of the simulation results. After setting different thicknesses of the protective layer, the RCC slab blast crater depth is reduced by 56.7%, 80%, and 93.3% compared with that at 0.18 m without a protective layer program, and almost no damage to the back explosion surface occurs. The failure volume ratio of the protected RCC slab structure gradually decreases from 38.53% to 3.24% with increasing protective layer thickness, and the protected RCC slab shows only slight damage after setting the protective layer. When the thickness of the protective layer is 0.3 m, the damage of the protected RCC slab structure is distributed in the surface area, which has little effect on the structural safety. These results show that the additional SFSRCC protective layer under the condition of underwater near‐field explosion can significantly reduce the damage degree of the slab structure and improve the explosion‐proof performance of the protected RCC slab structure. This research offers a theoretical reference for the explosion‐proof material selection and design of hydraulic structures and explosion‐proof application of SFSRCC under the action of underwater explosion impact loads.

Numerical investigation on dynamic behavior and damage mechanisms of fiber metal laminates subjected to combined explosion and fragments loading

Fiber metal laminates (FMLs) are widely applied as protective structures in various high-tech industries owing to their excellent impact resistance. This paper presents an explicit finite element (FE) simulation to investigate the dynamic damage behavior of carbon fiber-reinforced aluminum laminates (CRALLs) under combined explosion and fragment loading. Johnson-Cook model is utilized to capture the damage response of aluminum material; 3D Hashin failure criteria are applied to predict the damage evolution of fiber composite material considering the high strain rate effect; cohesive elements are incorporated to simulate the inter-laminar delamination phenomena. The effectiveness of the proposed numerical model is verified through a comparison with available experimental data in ballistic impact conditions. In addition, a thorough analysis of the dynamic behavior and damage mechanism of FMLs is conducted, and the impact performance is extensively discussed in terms of the influences of explosion distance and explosion mass. This work serves as a valuable reference for future numerical studies on the explosive impact resistance of other FMLs structures.

Dynamic stability of concrete structures with varying sections to underwater contact explosion: A case study of gravity dams

Concrete structures with varying sections are widely used in the fields of ocean engineering, hydraulic engineering and civil engineering. And the damage mechanism of variable-section structures to underwater contact explosion, which involves localized damage by explosion impact and instability by overall structural vibration, is very complex. The gravity dam is taken as an example, the coupled analysis model for gravity dams under underwater contact blast is established, a prototype test on the dynamic response of a gravity dam under underwater explosion is conducted to verify the reliability of the fluid-solid interaction method, and the reliability of the concrete dynamic damage model adopted in this paper is validated by a small-scale field test on the internal blast damage of a gravity dam. The damage mechanism of gravity dams subjected to underwater contact explosion is analyzed. A stability analysis method for gravity dams to underwater contact explosion is proposed, which allows simultaneous consideration of the dam stability in the blast-induced vibration phase and the static phase after damage. The dynamic stability performance of gravity dams to underwater contact explosion is analyzed. And a stability assessment criterion that could be used to assess the safety level of dams at various stages is presented.