scholarly journals Numerical Investigation on the Formation and Penetration Behavior of Explosively Formed Projectile (EFP) with Variable Thickness Liner

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1342
Author(s):  
Dong Yang ◽  
Jiajian Lin
Keyword(s):  
Shock Wave ◽  
Variable Thickness ◽  
Hollow Structure ◽  
Fe Model ◽  
Uniform Thickness ◽  
Target Plate ◽  
Impact Performance ◽  
Penetration Ability ◽  
Penetration Behavior ◽  
The Military

Explosively formed projectiles (EFPs) are widely used in civil applications and the military field for their excellent impact performance. How to give full play to the energy accumulation effect of explosives and improve the penetration performance has become the main problem of EFP design. The aim of the present study was to investigate the effect of liner structure on EFP formation and its penetration behavior. In order to achieve this, a finite element (FE) model was first established on the basis of the Lagrange and ALE method. Then, formation and penetration performance tests of EFP were performed to verify the validity and feasibility of the proposed FE model, where the configuration, velocity of EFP, and penetration diameter left on the target plate were compared. Finally, by using the proposed FE model, the entire process of the formation and penetration behavior of EFP with axial symmetrical variable thickness liners were analyzed, where spherical-segment liners with uniform and non-uniform thickness were developed. The results were drawn as follows: the numerical simulation error of EFP velocity was less than 5%, and the simulated penetration diameter was compared to the 8.6% error obtained from the experimental method. It demonstrated that the proposed FE model had higher prediction precision. After the explosive was detonated, a forward-folding EFP was formed by the liner with a thin edge thickness, while the EFP formed by the liner with uniform thickness had a backward-folded configuration. It was also found that the liner with a thin edge thickness gave the largest steady velocity of EFP, and it was the lowest by using the liner with uniform thickness. There were two types of loads generated after the formation of an EFP, those were shock wave loading and an EFP, both causing damage in the target plate during the process of an EFP’s penetration into it. The shock wave induced by liners with non-uniform thickness caused higher damage in the target plate, the maximum value of stress was reached at about 4.0 GPa. The forward-folding EFP formed by the liner with the thinnest edge thickness had the largest penetration ability. The backward-folded EFP, owing to the hollow structure, had the worst penetration ability, which failed to penetrate the target plate.

scholarly journals A Lab-Scale Experiment Approach to the Measurement of Wall Pressure from Near-Field under Water Explosions by a Hopkinson Bar

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xiongwei Cui ◽  
Xiongliang Yao ◽  
Yingyu Chen
Keyword(s):  
Shock Wave ◽  
Near Field ◽  
Underwater Explosion ◽  
Experimental System ◽  
Hopkinson Bar ◽  
Wall Pressure ◽  
Pressure Loading ◽  
Target Plate ◽  
Wave Pressure ◽  
Shock Wave Pressure

Direct measurement of the wall pressure loading subjected to the near-field underwater explosion is of great difficulty. In this article, an improved methodology and a lab-scale experimental system are proposed and manufactured to assess the wall pressure loading. In the methodology, a Hopkinson bar (HPB), used as the sensing element, is inserted through the hole drilled on the target plate and the bar’s end face lies flush with the loaded face of the target plate to detect and record the pressure loading. Furthermore, two improvements have been made on this methodology to measure the wall pressure loading from a near-field underwater explosion. The first one is some waterproof units added to make it suitable for the underwater environment. The second one is a hard rubber cylinder placed at the distal end, and a pair of ropes taped on the HPB is used to pull the HPB against the cylinder hard to ensure the HPB’s end face flushes with loaded face of the target plate during the bubble collapse. To validate the pressure measurement technique based on the HPB, an underwater explosion between two parallelly mounted circular target plates is used as the validating system. Based on the assumption that the shock wave pressure profiles at the two points on the two plates which are symmetrical to each other about the middle plane of symmetry are the same, it was found that the pressure obtained by the HPB was in excellent agreement with pressure transducer measurements, thus validating the proposed technique. To verify the capability of this improved methodology and experimental system, a series of minicharge underwater explosion experiments are conducted. From the recorded pressure-time profiles coupled with the underwater explosion evolution images captured by the HSV camera, the shock wave pressure loading and bubble-jet pressure loadings are captured in detail at 5  mm, 10  mm, …, 30  mm stand-off distances. Part of the pressure loading of the experiment at 35  mm stand-off distance is recorded, which is still of great help and significance for engineers. Especially, the peak pressure of the shock wave is captured.

The Analysis and Improvement for Side Impact of Car Body Structure

2013 ◽  
Vol 456 ◽  
pp. 38-42
Author(s):  
Ai Hong Gong ◽  
Ming Mao Hu
Keyword(s):  
Side Impact ◽  
Fe Model ◽  
Body Structure ◽  
Impact Performance ◽  
Car Body ◽  
Euro Ncap ◽  
Virtual Test ◽  
Structure Improvement ◽  
Moving Deformable Barrier ◽  
The Impact

Based on the finite element (FE) model and Moving Deformable barrier (MDB) model of a car side impact, the virtual test of the side impact was conducted with HYPERWORK software according to Euro-NCAP regulation. Then the impact performance was evaluated in both deformation and response curve of the car body, and the problem of the crashworthiness in designing the side structure was analyzed. Finally, the structure improvement with CATIA for the side crashworthiness was proposed. Keywords: CAE analyze, Side impact, Improvement

scholarly journals Ballistic Impact Performance of SiC Ceramic-Dyneema Fiber Composite Materials

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Kai-Kuang Wu ◽  
Yu-Liang Chen ◽  
Jau-Nan Yeh ◽  
Wei-Lun Chen ◽  
Chia-Shih Lin
Keyword(s):  
Composite Material ◽  
Simulation Analysis ◽  
Fiber Composite ◽  
Areal Density ◽  
Target Plate ◽  
Composite Target ◽  
Impact Performance ◽  
Ballistic Resistance ◽  
Sic Ceramic ◽  
The Relationship

This study investigated the ballistic resistance of a composite target plate fabricated by combining SiC ceramic with the Dyneema fiber. To achieve a light-weight target plate that conforms to the US National Institute of Justice level four (NIJ IV) standards, minimal areal density analysis was conducted to obtain the optimal SiC ceramic-Dyneema fiber thickness combination. This study used energy absorption to analyze the ballistic resistance of the target plates. To drastically reduce experimental costs, most of this work employed ANSYS/LS-DYNA software to conduct finite element numerical simulations. First, ballistic experiments that conformed to NIJ IV standards were conducted to verify the simulation parameter configurations. Subsequently, the correlation function of the relationship between the combined thickness of the composite material and its ballistic resistance was determined through the experimental design, which effectively reduced the simulation analysis time. According to simulation experiments and regression analysis, the equation for the relationship between the combined thickness of the composite material and its ballistic resistance was EAhc,hf=−6276.5+500.6hc+1512.6hf+30.7hchf−8.1hc2−113.6hf2, though there were limitations to its application. From the numerical analysis results, 8.1940 mm SiC ceramic and 6.9637 mm Dyneema fiber were determined to constitute the optimal thickness combination for a composite that features a minimal areal density and which conforms to NIJ IV standards. The combination was verified to be consistent with the numerical simulation analysis results.

scholarly journals The Fluid-Solid Interaction Dynamics between Underwater Explosion Bubble and Corrugated Sandwich Plate

2016 ◽  
Vol 2016 ◽  
pp. 1-21
Author(s):  
Hao Wang ◽  
Yuan Sheng Cheng ◽  
Jun Liu ◽  
Lin Gan
Keyword(s):  
Shock Wave ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Numerical Models ◽  
Near Field ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Bubble Collapse ◽  
Fe Model ◽  
Wave Load

Lightweight sandwich structures with highly porous 2D cores or 3D (three-dimensional) periodic cores can effectively withstand underwater explosion load. In most of the previous studies of sandwich structure antiblast dynamics, the underwater explosion (UNDEX) bubble phase was neglected. As the UNDEX bubble load is one of the severest damage sources that may lead to structure large plastic deformation and crevasses failure, the failure mechanisms of sandwich structures might not be accurate if only shock wave is considered. In this paper, detailed 3D finite element (FE) numerical models of UNDEX bubble-LCSP (lightweight corrugated sandwich plates) interaction are developed by using MSC.Dytran. Upon the validated FE model, the bubble shape, impact pressure, and fluid field velocities for different stand-off distances are studied. Based on numerical results, the failure modes of LCSP and the whole damage process are obtained. It is demonstrated that the UNDEX bubble collapse jet local load plays a more significant role than the UNDEX shock wave load especially in near-field underwater explosion.

The Simulation Study on Degree of Protection/Damage under Blast Loads

2012 ◽  
Vol 271-272 ◽  
pp. 1229-1233
Author(s):  
Yun Chen ◽  
Hua Wang ◽  
Shun Shan Feng
Keyword(s):  
Metal Plate ◽  
Structure Design ◽  
Blast Loads ◽  
Target Plate ◽  
Pressure Impulse ◽  
Degree Of Protection ◽  
The Military ◽  
Target Metal ◽  
Important Basis ◽  
Good Agreement

The degree of protection/damage of the target is an important basis for the target structure design. In the military field, the target can be equivalent to a target metal plate with the certain thickness. The degree of protection can be divided through the effect of target plate under blast loads. Considering the reflected parameters, the reflected pressure-impulse criterion can be used to assess the damage caused by the blast. Through the combination of theoretical analysis and numerical simulation, the target plate’s pressure-impulse diagrams of different degrees are obtained. The results of the experiments and simulations are found in good agreement, which validates the numerical model.

Vibration Control of Variable Thickness Plates With Embedded Acoustic Black Holes and Dynamic Vibration Absorbers

2015 ◽  
Author(s):  
Xiuxian Jia ◽  
Yu Du ◽  
Kunmin Zhao
Keyword(s):  
Vibration Control ◽  
Variable Thickness ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Response Level ◽  
Control Approach ◽  
Dynamic Vibration ◽  
Vibration Responses ◽  
Dynamic Vibration Absorbers ◽  
Acoustic Black Holes

In the past decade, plate-like structures embedded with one or more acoustic black hole (ABH) features have been developed as a promising passive approach for structural sound and vibration control. In this study, the concept of combining dynamic vibration absorbers (DVAs) and the ABH effect is proposed to further improve the vibration control effectiveness of a variable thickness plate. A finite element (FE) model is developed to analyze the vibration response of a plate embedded with both ABHs and DVAs under point force excitations. To demonstrate the effectiveness of different vibration control approaches, the vibration responses of plates of uniform thickness, variable thickness embedded with ABH features, variable thickness embedded with both ABH features and damping layers, and variable thickness embedded with both ABH features and DVAs are compared experimentally. It is shown that, in the frequency range considered in the current study which is up to 6.4 kHz, the uniform plate presents high average velocity response level. On the other hand, although 11.5% lighter, the variable thickness plate integrated with both ABH and DVA features results in the lowest response level. Results in this study demonstrate the potential of combing DVAs and ABHs together as an effective lightweight noise and vibration control approach.

Improve Lower Leg Impact Performance Considering Pedestrian Protection

2011 ◽  
Vol 109 ◽  
pp. 70-74
Author(s):  
Jin Hua Chen ◽  
Xiang Dong Huang
Keyword(s):  
Finite Element ◽  
Lower Leg ◽  
Fe Model ◽  
Test Results ◽  
Pedestrian Protection ◽  
Impact Performance ◽  
Front Structure ◽  
Energy Absorbing

To improve the lower leg impact performance of the vehicle bumper in the collision of vehicle to pedestrian, the finite element (FE) model of a vehicle front structure was developed, and correlated with the test results. The lower legform impactor FE model was used to investigate the performance of the vehicle bumper at different structure conditions. It was finally determined that vehicle to lower legform impact performance can be improved by reducing the energy absorbing foam stiffness and modifying the bumper bracket structure to enlarge the collapse space.

scholarly journals Biologically inspired crack delocalization in a high strain-rate environment

2011 ◽  
Vol 9 (69) ◽  
pp. 665-676 ◽  
Author(s):  
Christian Knipprath ◽  
Ian P. Bond ◽  
Richard S. Trask
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Structural Characteristics ◽  
Fe Model ◽  
Impact Performance ◽  
Biological Design ◽  
Matrix Properties ◽  
Rate Environment ◽  
Energy Absorbing

Biological materials possess unique and desirable energy-absorbing mechanisms and structural characteristics worthy of consideration by engineers. For example, high levels of energy dissipation at low strain rates via triggering of crack delocalization combined with interfacial hardening by platelet interlocking are observed in brittle materials such as nacre, the iridescent material in seashells. Such behaviours find no analogy in current engineering materials. The potential to mimic such toughening mechanisms on different length scales now exists, but the question concerning their suitability under dynamic loading conditions and whether these mechanisms retain their energy-absorbing potential is unclear. This paper investigates the kinematic behaviour of an ‘engineered’ nacre-like structure within a high strain-rate environment. A finite-element (FE) model was developed which incorporates the pertinent biological design features. A parametric study was carried out focusing on (i) the use of an overlapping discontinuous tile arrangement for crack delocalization and (ii) application of tile waviness (interfacial hardening) for improved post-damage behaviour. With respect to the material properties, the model allows the permutation and combination of a variety of different material datasets. The advantage of such a discontinuous material shows notable improvements in sustaining high strain-rate deformation relative to an equivalent continuous morphology. In the case of the continuous material, the shockwaves propagating through the material lead to localized failure while complex shockwave patterns are observed in the discontinuous flat tile arrangement, arising from platelet interlocking. The influence of the matrix properties on impact performance is investigated by varying the dominant material parameters. The results indicate a deceleration of the impactor velocity, thus delaying back face nodal displacement. A final series of FE models considered the identification of an optimized configuration as a function of tile waviness and matrix properties. In the combined model, the optimized configuration was capable of stopping the ballistic threat, thus indicating the potential for bioinspired toughened synthetic systems to defeat high strain-rate threats.

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