The Role of Kelvin–Helmholtz Instabilities on Shaped Charge Jet Interaction With Reactive Armor Plates

2010 ◽  
Vol 77 (5) ◽  
Author(s):  
Andreas Helte ◽  
Ewa Lidén
Keyword(s):  
Parametric Study ◽  
Impact Angle ◽  
Shaped Charge ◽  
Contact Forces ◽  
Moving Plate ◽  
Protection Mechanism ◽  
Frictional Forces ◽  
The Difference ◽  
Shaped Charge Jet ◽  
The Impact

Reactive armor panels have been used for many years as very efficient add-on armor against shaped charge warheads. The main features of the defeat mechanisms of the armor are therefore well known. The origin of the irregular disturbances on the shaped charge jet, which leads to the severe fragmentation and scattering of the jet, is however not described in literature. As this scattering of the jet provides the main protection mechanism of the armor, it is of interest to understand the details of the interaction and the origin of the disturbances. Some experimental observations have been made showing that the backward moving plate often displaces the jet relatively smoothly while it is the interaction with the forward moving plate that causes the disturbances that leads to fragmentation and scattering of the jet. In this work, a mechanism for the interaction is proposed based on the theory of Kelvin–Helmholtz instabilities, which explains the origin of the disturbances on the jet due to the interaction with the forward moving plate. Numerical simulations have been performed to show the difference in the mechanisms of backward and forward moving plates when interacting with the jet. The impact angle of the plate seems to be the dominant parameter for the onset of instabilities. A parametric study has also been performed on how different interaction and material parameters influence the development of instabilities of the interface between the jet and the armor plate. The parametric study shows that low-strength jets promote development of instabilities, a tendency that is amplified by frictional forces between the materials. The influence of the plate strength is more complex due to the influence of the structural stability on the contact forces. The effect of friction and melting of the metals in the boundary layer to the development of the instabilities is discussed. A microscopic study of the edge of the penetration channel has been made, which shows that the materials have been melted during the interaction between the plate and the jet.

Education level, underemployment, and workers’ health

2021 ◽  
Author(s):  
Nan Li ◽  
Dan Wu
Keyword(s):  
Health Inequality ◽  
Economic Effect ◽  
Empirical Support ◽  
Education Level ◽  
Educational Levels ◽  
Protection Mechanism ◽  
Low Education ◽  
The Difference ◽  
The Impact ◽  
Level Group

Under the dual background of underemployment and health inequality, this paper empirically analyzes the impact of education level on underemployed workers’ health based on CLDS2016 data. The results show that underemployment is significantly related to the decline of self-rated health, increased depression tendency, and morbidity in a certain period. The results indicate that underemployment can significantly reduce the health level of workers in the low education level group and the high education level group. However, it has no significant impact on workers’ health in the middle education level group; even if we change the measurement method of indicators and consider endogeneity, the research conclusion is still robust. Moreover, this kind of health inequality mainly comes from the difference in economic effect and leisure effect of underemployment to workers with different educational levels. This paper provides empirical support for increasing the labor protection mechanism of underemployed people and reducing the health inequality caused by educational level differences.

Effect of fragment impact on shaped charge jet formation and penetration into steel target

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hakan Hafizoglu ◽  
Huseyin Emrah Konokman ◽  
Latif Kesemen ◽  
Ali Kursat Atay
Keyword(s):  
Penetration Depth ◽  
Symmetry Axis ◽  
Impact Angle ◽  
Shaped Charge ◽  
Steel Plates ◽  
Jet Formation ◽  
Target Plate ◽  
Content Type ◽  
Simulation Results ◽  
Shaped Charge Jet

Purpose This paper aims to investigate the effects of fragment impacts to shaped charge warheads in terms of shaped charge jet formation geometries and penetration performances. Design/methodology/approach In experimental process, a fragment was accelerated to a shaped charge warhead by means of a powder gun to a velocity more than 1,000 m/s, and this impact led to conical damage in the explosive of the warhead. Deformation on the warhead was visualized using X-ray technique to observe holes generated during fragment impact. Penetration test was performed against AISI 1040 steel plates with the damaged shaped charge warhead. Penetration performance of shaped charge jet, which deviated from the symmetry axis, was simulated by using SPEED software with 3-D Eulerian method to validate the numerical modelling method by comparing penetration test and simulation results of damaged warhead. Findings Simulation and test results showed good correlation for the warhead in terms of penetration depth and hole geometry at the impact surface of steel plates. In addition, the effects of the numbers and the geometries of fragment holes on shaped charge jet penetration performances were investigated with validated numerical methods. Simulation results showed that the increase in the number of fragment holes in the explosive of the warhead led to particulation of shaped charge jet that diminished penetration depth in the target plate. Additionally, simulation results also showed that the fragment hole geometry in the explosive after different fragment impact angles affected the amount of jet deviation from the symmetry axis as well as penetration depth in the target plate. Practical implications The results obtained from the current study revealed that fragment impact angle and different number of fragment impact reduced the penetration performance of shaped charge warhead by influencing the symmetry of shaped charge jet negatively. Originality/value The current study fulfils the need to investigate how fragment impact on the shaped charge warhead affect the formation symmetry of shaped charge jet as well as penetration performance by experimental and numerical methods. Penetration performance result of asymmetric jet is compared by experimental and numerical studies. A detailed methodology on numerically modelling of the effect of fragment impact angle and number of fragment impact on shaped charge jet performance is given in this study.

scholarly journals Simulating Lateral Drift of a Shaped Charge Jet in ALEGRA

2019 ◽  
Author(s):  
Matthew J. Coppinger ◽  
W. Casey Uhlig ◽  
John H. J. Niederhaus
Keyword(s):  
Velocity Gradient ◽  
Explosive Charge ◽  
Shaped Charge ◽  
Analytical Models ◽  
Depth Of Penetration ◽  
Lateral Drift ◽  
The Difference ◽  
Shaped Charge Jet ◽  
Jet Axis ◽  
Penetration Velocity

Abstract Shaped charge jet (SCJ) research has long been an active area for industrial, academic, and defense organizations. Traditionally, the depth of penetration (DOP) has been one of the most important metrics for the evaluation of shaped charge jet performance, and early 1D analytical penetration models based on hydrodynamic penetration were created with this metric in mind [1]. As the standoff of a shaped charge jet increases, the DOP reaches a maximum and then begins to decrease. A simple 1D hydrodynamic penetration model must account for the totality of the jet material on axis penetrating, and as a result experimental DOP at longer standoffs is lower than the analytical models predicted. Some analytical models reasoned that since a velocity gradient evolves as a SCJ forms, contributions to penetration from jet material below a minimum jet or penetration velocity should be eliminated. These were better able to account for the difference between analytical hydrodynamic and experimental DOPs [2]. The actual difference between analytical hydrodynamic penetration theory and experimentally recorded values is now regarded to be a result of 3D phenomena including particle tumbling and motion transverse to the jet axis known as lateral drift [2]. The origins of these 3D phenomena have been attributed to sources including variability in the uniformity of the explosive charge or the microstructure of the liner [2,3].

Investigation on the Impact and Penetration Performance of the Particulated Jet into Concrete Targets

2019 ◽  
Author(s):  
Qi-feng Zhu ◽  
Qiang-qiang Xiao ◽  
Zheng-xiang Huang ◽  
Xu-dong Zu ◽  
Xin Jia
Keyword(s):  
Titanium Alloys ◽  
Nickel Titanium ◽  
Shaped Charge ◽  
Ti Alloy ◽  
Depth Of Penetration ◽  
Experiment Method ◽  
Coherent Jet ◽  
Shaped Charge Jet ◽  
The Impact ◽  
Penetration Depths

Abstract In this study, the performance of titanium alloys (TC21, TC1), nickel-titanium (Ni-Ti) alloy, and zirconium-niobium (Zr-Nb) alloy lined shaped charge impact and penetration into concrete targets are investigated experimentally. Shaped charge jet radiographs reveal that the resulting jets of titanium alloys and Ni-Ti alloy exhibit particulate, radially dispersed behaviors, whereas that of the Zr-Nb alloy is coherent. Cavity diameters, penetration depths and parameters of the impact craters generated by the jets were analyzed using the depth of penetration (DOP) experiment method. Data indicate that the particulated jet causes more extensive damage to the surface of the concrete targets compared to the coherent jet. The penetration depth decreases to some degree, but the cavity diameter increases significantly. Penetration efficiency varies with degree of dispersion of the particulated jet and, as such, is also sensitive to stand-off distance.

Study on Shaped Charge Jet Initiation of Solid Rocket Motors

2019 ◽  
Author(s):  
Hao CUI ◽  
Rui GUO ◽  
Pu SONG ◽  
Jinsheng XU ◽  
Xiaohui GU ◽  
...  
Keyword(s):  
High Speed ◽  
Shaped Charge ◽  
Solid Rocket Motors ◽  
Rocket Motors ◽  
Jet Impact ◽  
Solid Rocket ◽  
Battlefield Environment ◽  
Shaped Charge Jet ◽  
The Impact ◽  
Jet Initiation

Abstract In order to study the mechanism of initiation of solid rocket motors under the impact of shaped charge jets, a shaped charge jet initiation test was experimentally studied to evaluate the safety of the motor under attack in the battlefield environment. The ex-perimental results indicated that the motor had a detonation reaction under the shaped charge jet impact. The response of the mo-tor was recorded by a high-speed camera. In addition, the mechanism of initiation of the propellant charge was evaluated using by numerical simulations. Pressure-time and reaction-time curves of propellants were analyzed in this paper.

Evaluation of the impact of public investment programs on social and economic performance of territories

2019 ◽  
pp. 109-123
Author(s):  
I. E. Limonov ◽  
M. V. Nesena
Keyword(s):  
Bayesian Modeling ◽  
Positive Impact ◽  
Public Investment ◽  
Difference In Differences ◽  
The Public ◽  
Export Activity ◽  
Regional Investment ◽  
The Difference ◽  
The Impact ◽  
Development Institution

The purpose of this study is to evaluate the impact of public investment programs on the socio-economic development of territories. As a case, the federal target programs for the development of regions and investment programs of the financial development institution — Vnesheconombank, designed to solve the problems of regional development are considered. The impact of the public interventions were evaluated by the “difference in differences” method using Bayesian modeling. The results of the evaluation suggest the positive impact of federal target programs on the total factor productivity of regions and on innovation; and that regional investment programs of Vnesheconombank are improving the export activity. All of the investments considered are likely to have contributed to the reduction of unemployment, but their implementation has been accompanied by an increase in social inequality.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

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