Modeling of Advanced Combat Helmet Under Ballistic Impact

2015 ◽  
Vol 82 (11) ◽  
Author(s):  
Y. Q. Li ◽  
X. G. Li ◽  
X.-L. Gao
Keyword(s):  
Experimental Data ◽  
Time History ◽  
Ballistic Impact ◽  
Medium Size ◽  
Lateral Impact ◽  
Ballistic Performance ◽  
Ballistic Impacts ◽  
Large Size ◽  
History Of ◽  
Head Form

The use of combat helmets has greatly reduced penetrating injuries and saved lives of many soldiers. However, behind helmet blunt trauma (BHBT) has emerged as a serious injury type experienced by soldiers in battlefields. BHBT results from nonpenetrating ballistic impacts and is often associated with helmet back face deformation (BFD). In the current study, a finite element-based computational model is developed for simulating the ballistic performance of the Advanced Combat Helmet (ACH), which is validated against the experimental data obtained at the Army Research Laboratory. Both the maximum value and time history of the BFD are considered, unlike existing studies focusing on the maximum BFD only. The simulation results show that the maximum BFD, the time history of the BFD, and the shape and size of the effective area of the helmet shell agree fairly well with the experimental findings. In addition, it is found that ballistic impacts on the helmet at different locations and in different directions result in different BFD values. The largest BFD value is obtained for a frontal impact, which is followed by that for a crown impact and then by that for a lateral impact. Also, the BFD value is seen to decrease as the oblique impact angle decreases. Furthermore, helmets of four different sizes—extra large, large, medium, and small—are simulated and compared. It is shown that at the same bullet impact velocity the small-size helmet has the largest BFD, which is followed by the medium-size helmet, then by the large-size helmet, and finally by the extra large-size helmet. Moreover, ballistic impact simulations are performed for an ACH placed on a ballistic dummy head form embedded with clay as specified in the current ACH testing standard by using the validated helmet model. It is observed that the BFD values as recorded by the clay in the head form are in good agreement with the experimental data.

Characteristics of a Simple Energy Absorption Transducer

1986 ◽  
Vol 108 (3) ◽  
pp. 676-683 ◽  
Author(s):  
B. T. Beck ◽  
G. L. Wedekind
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Laser Radiation ◽  
Steel Substrate ◽  
Time History ◽  
Radiation Absorption ◽  
Flux Analysis ◽  
Manganese Phosphate ◽  
History Of ◽  
Arbitrary Location

This paper presents the results of an investigation into a simple technique developed primarily for evaluating surface coating effectiveness for the absorption of a nonuniform laser radiation heat flux. Analysis suggests that if the transducer sensor is designed appropriately, and the experimental data analyzed in a particular manner, the temperature–time history of the transducer need be measured at only a single arbitrary location. These conclusions are also supported by experimental measurements of laser radiation absorption at a wavelength of 10.6 μm for polished copper, polished steel, and for a manganese–phosphate coating on a steel substrate. The absorptivities measured for the polished copper and steel agree well with other experimental data in the literature. Limitations of the measurement technique, resulting from the temperature dependence of the transducer material properties, radiation absorptivity, and combined convective and radiative heat flux, are also investigated theoretically and experimentally.

Growth and translation of a liquid-vapour compound drop in a second liquid. Part 2. Heat transfer

1989 ◽  
Vol 209 ◽  
pp. 639-660 ◽  
Author(s):  
S. T. Vuong ◽  
S. S. Sadhal
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Finite Difference Methods ◽  
Time History ◽  
Immiscible Liquid ◽  
Transport Processes ◽  
Contact Heat ◽  
Contact Heat Exchange ◽  
History Of ◽  
Single Compound

The present work is a comprehensive theoretical study of the heat transfer associated with a 3-singlet compound drop that is growing because of change of phase. The geometry is the same as in Part 1, i.e. a vapour bubble partially surrounded by its own liquid in another immiscible liquid. The attempt here is to gain fundamental understanding of the transport processes that take place in connection with direct-contact heat exchange. The fluid dynamics associated with its growth and translation is treated in Part 1. Here, that flow field solution is used to obtain the temperature field and hence the evaporation rate. The energy equation for the system consisting of a single compound drop is solved numerically by finite-difference methods. The results give the complete time history of evaporation of the drop. In addition, useful quantities such as the Nusselt number are given and compared with existing experimental data. Most of the results have good agreement with experimental data.

Mitigation Effect of Vertical Walls on a Wharf Model Subjected to Tsunami Bores

2017 ◽  
Vol 11 (03) ◽  
pp. 1750004 ◽  
Author(s):  
Cheng Chen ◽  
Bruce W. Melville ◽  
N. A. K. Nandasena ◽  
Asaad Y. Shamseldin ◽  
Liam Wotherspoon
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Vertical Wall ◽  
Time History ◽  
Conservation Of Energy ◽  
Inundation Depth ◽  
History Of ◽  
Vertical Walls ◽  
Predicted Values ◽  
Different Characteristics

An experimental study was carried out to investigate the mitigation effect of vertical walls on a wharf model subjected to tsunami bores. Dam-break waves were generated in a flume to simulate tsunami bore propagation, the bore characteristics were observed, and the tsunami pressures on vertical walls and a wharf model were measured. Results indicate different characteristics for bores traveling on wet-bed and dry-bed. The tsunami bore impact on a vertical wall was shown to exhibit four stages, and the time-history of the pressure exhibits three phases accordingly. Based on the law of conservation of energy, an equation for estimating the pressure exerted on the mid-point of the wall was proposed with coefficient of 1.8–2.4, and found to be suitable in this experimental range. Based on experimental data, an equation of the mitigation effect of vertical walls on tsunami was proposed as a function of the inundation depth, the wall height and the deck height. The predicted values from the equation are generally within [Formula: see text] of the measured values.

scholarly journals Numerical simulation of GLARE 4A fiber-metal laminates subjected to ballistic impact

2018 ◽  
Vol 188 ◽  
pp. 01017
Author(s):  
George Bikakis ◽  
Nikolaos Tsigkros ◽  
Emilios Sideridis ◽  
Alexander Savaidis
Keyword(s):  
Impact Load ◽  
Impact Damage ◽  
Impact Resistance ◽  
Time History ◽  
Ballistic Impact ◽  
Fiber Metal Laminates ◽  
Ballistic Impacts ◽  
Fiber Metal ◽  
Force Time ◽  
The Impact

This article deals with the evaluation of the ballistic resistance of GLARE 4A fiber-metal laminates subjected to high velocity impact by a cylindrical projectile. Important impact variables such as the ballistic limit, the impact load and the absorbed energy time histories are predicted using the ANSYS LS-DYNA software. The simultaneous existence of various impact damage mechanisms, which is unique in fiber-metal laminates, is demonstrated using the numerical results. Each of the mechanisms absorbs a part of the initial impact energy and contributes to the high ballistic impact resistance the materials. With reference to the considered GLARE 4A panels, the behavior of the transient impact load is analyzed and useful conclusions are drawn. It is found that the maximum impact load is applied at the beginning of ballistic impacts, during the initial local indentation of the panels under the projectile. It is substantially higher than the following peak values of the impact force time history. It is revealed that during the beginning of ballistic impacts, the impulse of the collision increases as the thickness of the panels is increased. The work done by the impact load during the local indentation stage is also an increasing function of the panels’ thickness.

Effects of Curvature and Architecture on Ballistic Performance of UHMWPE Helmets

2019 ◽  
Author(s):  
Timothy G. Zhang ◽  
Lionel R. Vargas-Gonzalez ◽  
James C. Gurganus ◽  
Sikhanda S. Satapathy
Keyword(s):  
Experimental Data ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Test Data ◽  
Ballistic Impact ◽  
Ballistic Performance ◽  
Impact Experiments ◽  
Ultra High Molecular Weight

Abstract Ballistic impact experiments were conducted on three types of Ultra-high-molecular-weight polyethylene (UHMWPE) helmets. The three types of helmets had the same geometry, but different fiber orientations in the rear layers. The test data were used to evaluate the effects of architectures. Five impact locations were chosen to understand the effects of impact locations and curvatures. The experimental data from flat and cylindrically curved UHMWPE panels were also used to compare with the helmet test data.

URANS Simulation of ONR Tumblehome Parametric Rolling in Regular Head Waves

2019 ◽  
Author(s):  
Zhiguo Zhang ◽  
Lixiang Guo ◽  
Shuang Wang ◽  
Ye Yuan ◽  
Can Chen
Keyword(s):  
Experimental Data ◽  
Time History ◽  
Head Wave ◽  
Ship Motions ◽  
Parametric Rolling ◽  
Wave Characteristic ◽  
Head Waves ◽  
History Of ◽  
Onr Tumblehome ◽  
Regular Head Waves

Abstract In this paper, an in-house CFD code HUST-Ship is used for the numerical simulation of parametric rolling phenomena of ONR Tumblehome in regular head wave. Preliminary resistance and roll decay simulations at Fr = 0.2 were carried out and compared with existed INSEAN experimental data. Following, three DOFs’ ship motions in regular head wave with an initial roll angle of 30 degrees was calculated to examine the possibility of occurrence of parametric rolling. Finally, a simulation without initial roll disturbance was performed to investigate its influence to the steady roll amplitude. By conducting fast Fourier transform of the time history of motions, forces and moments, the characteristics are analyzed and co-related with wave frequency. Results can be concluded that the in-house code has the ability to perform the parametric rolling simulation, and that the final steady roll amplitude is not affected by the initial disturbance. In addition, heave and pitch motions are dominantly affected by wave characteristic, roll frequency is about half that of wave, and that forces and moments in x direction exhibit high-order non-linearity.

AISI TYPE S2

Alloy Digest ◽  
1982 ◽  
Vol 31 (12) ◽  
Keyword(s):  
Physical Properties ◽  
Tensile Properties ◽  
Tool Steel ◽  
Shock Loading ◽  
Heat Treating ◽  
Medium Size ◽  
Hard Case ◽  
Large Size ◽  
Steel Mills ◽  
Aisi Type

Abstract AISI Type S2 is a water-hardening tool steel with extreme toughness and resistance to shock loading. Even at a hardness of Rockwell C 59-60, it will bend before it breaks. When hardened in medium-size and large-size pieces, it acquires a hard case and a tough core. Sizes under 3/4-inch (19mm) diameter will water harden to the center. The extreme toughness of Type S2 makes it suitable for use in many applications where no other tool steel will hold up. Its many uses include chisels, rivet busters, spike mauls, screw drivers, punches and sledges. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, and joining. Filing Code: TS-408. Producer or source: Tool steel mills.

PROGRAM OF PREDICTION AND MANAGEMENT OF COINTEGED DYNAMIC ECONOMIC PROCESSES BASED ON THE CYBERNETIC APPROACH

2019 ◽  
Author(s):  
Olena Bundak ◽  
Nataliia Zubovetska
Keyword(s):  
Computer Program ◽  
Pair Correlation ◽  
Time History ◽  
Critical Area ◽  
Concrete Object ◽  
Graphic Arts ◽  
Ex Post ◽  
History Of ◽  
Successive Change ◽  
Rms Errors

A method and computer program ConRow, which prognostication of development of the dynamically CPLD economic transients is executed by, is described in the article. Such prognostication of economic processes is very important in the cases when their development can result in undesirable consequences, that to go out in the so-called critical area. Extrapolation in a critical area with the use of information about the conduct of the system at an area, near to it, allows to estimate to the lead through of experiment in the critical area of his consequence. For the imitation of conduct of object the function of review is set on entrance influence. For a concrete object this function can express, for example, dependence of change of level sale from time-history of charges on advertising and set as a numeral row. Statistics as a result of analysis of row are represented in a table, where the level of meaningfulness is set statistician, and also parameters of the handed over criteria. The graphic reflection of information is intended for visualization of analysis. Here represented on the points of graphic arts, the crooked smoothing which are calculated as полиномиальные regressions is added. The best approaching is controlled by sight on the proper graph, and also by minimization of their rms errors. Models of prognostication by sight and as formulas represented on graphic arts, the middle is here determined tailings and their chance is checked up on statistics of signs. After the got models determined also and prognosis values of influences and reviews. Establishing an order models of Сr(p) of co integrate regression is carried out separate custom controls. The coefficient of clay correlation of ruФ shows by itself pair correlation between lines with a successive change in relation to each other on a size to лагу of l = 1, 2, 3 . The program was tested on the example of ex-post prognosis at establishing an integration connection and possibility of prognostication of growth of nominal average monthly settlings on the basis of these statistical indexes of consumer inflation in Ukraine.

scholarly journals Comparison of Novel Seismic Protection Devices to Attenuate the Earthquake Induced Energy

Actuators ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 73
Author(s):  
Osman Hansu ◽  
Esra Mete Güneyisi
Keyword(s):  
Lateral Displacement ◽  
Time History ◽  
Seismic Protection ◽  
Base Shear ◽  
Seismic Demands ◽  
Nonlinear Time History Analyses ◽  
History Of ◽  
Protection Devices ◽  
Nonlinear Time History ◽  
Better Than

This study addresses an alternative use of viscous dampers (VDs) associated with buckling restrained braces (BRBs) as innovative seismic protection devices. For this purpose, 4-, 8- and 12-story steel bare frames were designed with 6.5 m equal span length and 4 m story height. Thereafter, they were seismically improved by mounting the VDs and BRBs in three patterns, namely outer bays, inner bays, and all bays over the frame heights. The structures were modeled using SAP 2000 software and evaluated by the nonlinear time history analyses subjected to the six natural ground motions. The seismic responses of the structures were investigated for the lateral displacement, interstory drift, absolute acceleration, maximum base shear, and time history of roof displacement. The results clearly indicated that the VDs and BRBs reduced seismic demands significantly compared to the bare frame. Moreover, the all-bay pattern performed better than the others.

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