Effect of Helmet Pads on the Load Transfer to Head Under Blast Loadings

2014 ◽  
Author(s):  
Timothy G. Zhang ◽  
Sikhanda S. Satapathy
Keyword(s):  
Load Transfer ◽  
Numerical Study ◽  
Single Layer ◽  
Blast Loading ◽  
Performance Criterion ◽  
Ballistic Performance ◽  
Commercial Code ◽  
Head Assembly ◽  
Computational Simplicity ◽  
Blast Loadings

Recent wars have highlighted the need to better protect dismounted soldiers against emerging blast and ballistic threats. Current helmets are designed to meet ballistic performance criterion. Therefore, ballistic performance of helmets has received a lot of attention in the literature. However, blast load transfer/mitigation has not been well understood for the helmet/foam pads. The pads between the helmet and head can not only absorb energy, but also produce more comfort to the head. The gap between the helmet and head due to the pads helps prevent or delay the contact between helmet shell and the head. However, the gap between the helmet shell and the head can produce underwash effect, where the pressure can be magnified under blast loading. In this paper, we report a numerical study to investigate the effects of foam pads on the load transmitted to the head under blast loading. The ALE module in the commercial code, LS-DYNA was used to model the interactions between fluid (air) and the structure (helmet/head assembly). The ConWep function was used to apply blast loading to the air surrounding the helmet/head. Since we mainly focus on the load transfer to the head, four major components of the head were modeled: skin, bone, cerebrospinal fluid (CSF) and brain. The foam pads in fielded helmets are made of a soft and a hard layer. We used a single layer with the averaged property to model both of those layers for computational simplicity. Sliding contact was defined between the foam pads and the helmet. A parametric study was carried out to understand the effects of material parameters and thickness of the foam pads.

Numerical Study of Head/Helmet Interaction due to Blast Loading

2013 ◽  
Author(s):  
Timothy G. Zhang ◽  
Sikhanda S. Satapathy ◽  
Amy M. Dagro ◽  
Philip J. McKee
Keyword(s):  
Numerical Study ◽  
Spherical Shape ◽  
Human Head ◽  
Pressure Amplitude ◽  
Blast Pressure ◽  
Geometry Model ◽  
Blast Effects ◽  
Head Assembly ◽  
Computational Simplicity ◽  
The Brain

Recent wars have heightened the need to better protect dismounted soldiers against emerging blast and ballistic threats. Traumatic Brain Injury (TBI) due to blast and ballistic loading has been a subject of many recent studies. In this paper, we report a numerical study to understand the effects of load transmitted through a combat helmet and pad system to the head and eventually to the brain during a blast event. The ALE module in LS-DYNA was used to model the interactions between fluid (air) and the structure (helmet/head assembly). The geometry model for the head was generated from the MRI scan of a human head. For computational simplicity, four major components of the head are modeled: skin, bone, cerebrospinal fluid (CSF) and brain. A spherical shape blast wave was generated by using a spherical shell air zone surrounding the helmet/head structure. A numerical evaluation of boundary conditions and numerical algorithm to capture the wave transmission was carried out first in a simpler geometry. The ConWep function was used to apply blast pressure to the 3D model. The blast pressure amplitude was found to reduce as it propagated through the foam pads, indicating the latter’s utility in mitigating blast effects. It is also shown that the blast loads are only partially transmitted to the head. In the calculation where foam pads were not used, the pressure in the skin was found to be higher due to the underwash effect in the gap between the helmet and skin, which amplified the blast pressure.

scholarly journals Enhanced ultraviolet absorption in graphene by aluminum and magnesium hole-arrays

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xueling Cheng ◽  
Yunshan Wang
Keyword(s):  
Numerical Study ◽  
Uv Spectroscopy ◽  
Single Layer ◽  
Hybrid Structure ◽  
Uv Absorption ◽  
Single Layer Graphene ◽  
Visible Range ◽  
Uv Spectrum ◽  
Hole Arrays ◽  
Uv Range

AbstractOptoelectronic devices in the UV range have many applications including deep-UV communications, UV photodetectors, UV spectroscopy, etc. Graphene has unique exciton resonances, that have demonstrated large photosensitivity across the UV spectrum. Enhancing UV absorption in graphene has the potential to boost the performance of the various opto-electronic devices. Here we report numerical study of UV absorption in graphene on aluminum and magnesium hole-arrays. The absorption in a single-layer graphene on aluminum and magnesium hole-arrays reached a maximum value of 28% and 30% respectively, and the absorption peak is tunable from the UV to the visible range. The proposed graphene hybrid structure does not require graphene to be sandwiched between different material layers and thus is easy to fabricate and allows graphene to interact with its surroundings.

scholarly journals Numerical Simulation of the Impact of the Heat Source Position on Melting of a Nano-Enhanced Phase Change Material

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1425
Author(s):  
Tarek Bouzennada ◽  
Farid Mechighel ◽  
Kaouther Ghachem ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Melting Rate ◽  
Heat Transfer Fluid ◽  
Commercial Code ◽  
Tube Position ◽  
The Impact ◽  
Change Material

A 2D-symmetric numerical study of a new design of Nano-Enhanced Phase change material (NEPCM)-filled enclosure is presented in this paper. The enclosure is equipped with an inner tube allowing the circulation of the heat transfer fluid (HTF); n-Octadecane is chosen as phase change material (PCM). Comsol-Multiphysics commercial code was used to solve the governing equations. This study has been performed to examine the heat distribution and melting rate under the influence of the inner-tube position and the concentration of the nanoparticles dispersed in the PCM. The inner tube was located at three different vertical positions and the nanoparticle concentration was varied from 0 to 0.06. The results revealed that both heat transfer/melting rates are improved when the inner tube is located at the bottom region of the enclosure and by increasing the concentration of the nanoparticles. The addition of the nanoparticles enhances the heat transfer due to the considerable increase in conductivity. On the other hand, by placing the tube in the bottom area of the enclosure, the liquid PCM gets a wider space, allowing the intensification of the natural convection.

Experimental and numerical study of a RC member under a close-in blast loading

2016 ◽  
Vol 127 ◽  
pp. 145-158 ◽  
Author(s):  
Ramón Codina ◽  
Daniel Ambrosini ◽  
Fernanda de Borbón
Keyword(s):  
Numerical Study ◽  
Blast Loading

Effect of Varied Layer-Content/Thickness on Ballistic Performance of a Functionally Graded Al2O3/ZrO2 Material

2018 ◽  
Vol 928 ◽  
pp. 243-248 ◽  
Author(s):  
Yu Liang Chen ◽  
Chin Yu Huang
Keyword(s):  
Energy Absorption ◽  
Ceramic Composite ◽  
Single Layer ◽  
Areal Density ◽  
Wave Impedance ◽  
Functionally Graded ◽  
Ballistic Performance ◽  
Graded Material ◽  
Stress Damage ◽  
Transmission And Reflection

This study compared the ballistic performance of alumina (Al2O3)/ zirconia (ZrO2) functionally graded material (FGM) specimens with various levels of thickness and ZrO2 content and a pure Al2O3 single-layer ceramic composite (PCM). Ballistic tests were conducted with 0.3-inch armor-piercing (AP) projectiles, and finite element code LS-DYNA was used to examine energy absorption, stress distribution, and ceramic cone failure in the specimens. The findings are as follows: First, regarding energy absorption per unit of areal density, the 5% FGMs had the highest ballistic performance, which increased by up to 8%. By contrast, the ballistic performance of the 15% FGMs declined significantly to lower than that of the PCM. Second, the capability of the ceramic cone to withstand stress damage and projectiles was significantly greater in the 5% FGMs than in the 15% FGMs. Third, the wave impedance variations increased with the ZrO2 content in each layer, thereby enhancing the interactions between impact waves and aggravating ceramic damage. Thus, the intensities of transmission and reflection waves in the 15% FGMs increased, thereby causing reductions in its ballistic performance.

scholarly journals Numerical Simulations of V-Shaped Plates Subjected to Blast Loadings: A Validation Study

2016 ◽  
Vol 10 (11) ◽  
pp. 203
Author(s):  
Mohd Zaid Othman ◽  
Qasim H. Shah ◽  
Muhammad Akram Muhammad Khan ◽  
Tan Kean Sheng ◽  
M. A. Yahaya ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Variable Mass ◽  
Blast Loading ◽  
Experimental Results ◽  
Average Difference ◽  
Simulation Results ◽  
Blast Loadings ◽  
Carrier Vehicle ◽  
Good Agreement

A series of numerical simulations utilizing LS-DYNA was performed to determine the mid-point deformations of V-shaped plates due to blast loading. The numerical simulation results were then compared with experimental results from published literature. The V-shaped plate is made of DOMEX 700 and is used underneath an armour personal carrier vehicle as an anti-tank mine to mitigate the effects of explosion from landmines in a battlefield. The performed numerical simulations of blast loading of V-shaped plates consisted of various angles i.e. 60°, 90°, 120°, 150° and 180°; variable mass of explosives located at the central mid-point of the V-shaped vertex with various stand-off distances. It could be seen that the numerical simulations produced good agreement with the experimental results where the average difference was about 26.6%.

Numerical study on dynamic behaviors of NRC slabs in containment dome subjected to close-in blast loading

2019 ◽  
Vol 135 ◽  
pp. 269-284 ◽  
Author(s):  
Chunfeng Zhao ◽  
Qiang Wang ◽  
Xin Lu ◽  
Jingfeng Wang
Keyword(s):  
Numerical Study ◽  
Blast Loading ◽  
Dynamic Behaviors

Numerical Simulations of Heat Transfer and Fluid Flow for a Rotating High-Pressure Turbine

2006 ◽  
Author(s):  
F. Mumic ◽  
L. Ljungkruna ◽  
B. Sunden
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Fluid Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Models ◽  
High Pressure Turbine ◽  
Experimental Heat ◽  
Commercial Code ◽  
Stator Vane

In this work, a numerical study has been performed to simulate the heat transfer and fluid flow in a transonic high-pressure turbine stator vane passage. Four turbulence models (the Spalart-Allmaras model, the low-Reynolds-number realizable k-ε model, the shear-stress transport (SST) k-ω model and the v2-f model) are used in order to assess the capability of the models to predict the heat transfer and pressure distributions. The simulations are performed using the FLUENT commercial software package, but also two other codes, the in-house code VolSol and the commercial code CFX are used for comparison with FLUENT results. The results of the three-dimensional simulations are compared with experimental heat transfer and aerodynamic results available for the so-called MT1 turbine stage. It is observed that the predictions of the vane pressure field agree well with experimental data, and that the pressure distribution along the profile is not strongly affected by choice of turbulence model. It is also shown that the v2-f model yields the best agreement with the measurements. None of the tested models are able to predict transition correctly.

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