scholarly journals Computational ballistic analysis of the cranial shot to John F. Kennedy

2021 ◽  
Author(s):  
Christophe Then
Keyword(s):  
Head Injury ◽  
Mathematical Models ◽  
High Speed ◽  
Human Head ◽  
Supersonic Speed ◽  
Fracture Characteristics ◽  
X Ray ◽  
High Speed Impact ◽  
Bullet Fragmentation ◽  
The Impact

Almost 60 years after the assassination of John F. Kennedy in 1963 the majority of Americans are still reluctant to believe the official reports of commissions from 1964 and again in 1976 that determined the direction of the shot resulting in the fatal head injury. Long-withheld, confidential government files released in 2017 reignited the controversy.The present investigation computationally simulated projectile-skull impacts from the direction specified in official reports and from three other directions. Detailed geometric models of the human head and ammunition, as well as known parameters from the assassination site served as the supportive base for analysis. Constitutive mathematical models for the impact of projectile material with skull tissues at supersonic speed were employed to analyze bone and bullet fragmentation mechanics. Simulated fracture characteristics of the bone and the bullet were compared with photographic and X-ray evidence. The most likely origin of the fatal shot was determined based on the degree of corresponding deformation and fragmentation between simulation and documented evidence. Computational corroboration could be established as physically consistent with high-speed impact from the rear, as established by the official commissions. Simulations of three other speculative shot origins did not correspond to the documented evidence.

scholarly journals Effect of different helmet shell configurations on the protection against head trauma

2019 ◽  
Vol 54 (7-8) ◽  
pp. 408-415 ◽  
Author(s):  
Marta Palomar ◽  
Ricardo Belda ◽  
Eugenio Giner
Keyword(s):  
Head Trauma ◽  
High Speed ◽  
Composite Shell ◽  
Human Head ◽  
High Rate ◽  
Finite Element Models ◽  
High Speed Impact ◽  
Full Metal Jacket ◽  
The Impact ◽  
Single Combat

Head trauma following a ballistic impact in a helmeted head is assessed in this work by means of finite element models. Both the helmet and the head models employed were validated against experimental high-rate impact tests in a previous work. Four different composite ply configurations were tested on the helmet shell, and the energy absorption and the injury outcome resulting from a high-speed impact with full metal jacket bullets were computed. Results reveal that hybrid aramid–polyethylene configurations do not prevent bullet penetration at high velocities, while 16-layer aramid configurations are superior in dissipating the energy absorbed from the impact. The fabric orientation of these laminates proved to be determinant for the injury outcome, as maintaining the same orientations for all the layers led to basilar skull fractures (dangerous), while alternating orientation of the adjacent plies resulted in an undamaged skull. To the authors knowledge, no previous work in the literature has analysed numerically the influence of different stack configurations on a single combat helmet composite shell on human head trauma.

Experimental Calibration of ISV Damage Model Constants for Pure Copper for High-Speed Impact Simulation

2016 ◽  
Author(s):  
Yangqing Dou ◽  
Yucheng Liu ◽  
Wilburn Whittington ◽  
Jonathan Miller
Keyword(s):  
High Speed ◽  
Impact Analysis ◽  
Split Hopkinson Pressure Bar ◽  
Internal State ◽  
Pure Copper ◽  
Damage Model ◽  
Hopkinson Pressure Bar ◽  
Experimental Calibration ◽  
High Speed Impact ◽  
The Impact

Coefficients and constants of a microstructure-based internal state variable (ISV) plasticity damage model for pure copper have been calibrated and used for damage modeling and simulation. Experimental stress-strain curves obtained from Cu samples at different strain rate and temperature levels provide a benchmark for the calibration work. Instron quasi-static tester and split-Hopkinson pressure bar are used to obtain low-to-high strain rates. Calibration process and techniques are described in this paper. The calibrated material model is used for high-speed impact analysis to predict the impact properties of Cu. In the numerical impact scenario, a 100 mm by 100 mm Cu plate with a thickness of 10 mm will be penetrated by a 50 mm-long Ni rod with a diameter of 10mm. The thickness of 10 mm was selected for the Cu plate so that the Ni-Cu penetration through the thickness can be well observed through the simulations and the effects of the ductility of Cu on its plasticity deformation during the penetration can be displayed. Also, that thickness had been used by some researchers when investigating penetration mechanics of other materials. Therefore the penetration resistance of Cu can be compared to that of other metallic materials based on the simulation results obtained from this study. Through this study, the efficiency of this ISV model in simulating high-speed impact process is verified. Functions and roles of each of material constant in that model are also demonstrated.

High-speed impacts of slender bodies into non-smooth, complex fluids

2018 ◽  
Vol 861 ◽  
Author(s):  
Ishan Sharma
Keyword(s):  
Penetration Depth ◽  
High Speed ◽  
Complex Fluids ◽  
Laboratory Data ◽  
Impact Speed ◽  
High Speed Impact ◽  
Smooth Complex ◽  
Theoretical Predictions ◽  
Slender Bodies ◽  
The Impact

We present a simple hydrodynamical model for the high-speed impact of slender bodies into frictional geomaterials such as soils and clays. We model these materials as non-smooth, complex fluids. Our model predicts the evolution of the impactor’s speed and the final penetration depth given the initial impact speed, and the material and geometric parameters of the impactor and the impacted material. As an application, we investigate the impact of deep-penetrating anchors into seabeds. Our theoretical predictions are found to match field and laboratory data very well.

scholarly journals Simulation of Bullet Fragmentation and Penetration in Granular Media

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5243
Author(s):  
Froylan Alonso Soriano-Moranchel ◽  
Juan Manuel Sandoval-Pineda ◽  
Guadalupe Juliana Gutiérrez-Paredes ◽  
Usiel Sandino Silva-Rivera ◽  
Luis Armando Flores-Herrera
Keyword(s):  
Kinetic Energy ◽  
Granular Media ◽  
Elastic Collision ◽  
Smooth Particle Hydrodynamics ◽  
X Ray ◽  
Bullet Fragmentation ◽  
Particle Hydrodynamics ◽  
The Moment ◽  
Physical Phenomena ◽  
The Impact

The aim of this work is to simulate the fragmentation of bullets impacted through granular media, in this case, sand. In order to validate the simulation, a group of experiments were conducted with the sand contained in two different box prototypes. The walls of the first box were constructed with fiberglass and the second with plywood. The prototypes were subjected to the impact force of bullets fired 15 m away from the box. After the shots, X-ray photographs were taken to observe the penetration depth. Transient numerical analyses were conducted to simulate these physical phenomena by using the smooth particle hydrodynamics (SPH) module of ANSYS® 2019 AUTODYN software. Advantageously, this module considers the granular media as a group of uniform particles capable of transferring kinetic energy during the elastic collision component of an impact. The experimental results demonstrated a reduction in the maximum bullet kinetic energy of 2750 J to 100 J in 0.8 ms. The numerical results compared with the X-ray photographs showed similar results demonstrating the capability of sand to dissipate kinetic energy and the fragmentation of the bullet caused at the moment of impact.

Evaluation of the Impact Formulae for Rigid Projectile Striking on Concrete Target

2011 ◽  
Vol 368-373 ◽  
pp. 894-900 ◽  
Author(s):  
Hao Wu ◽  
Qin Fang
Keyword(s):  
Penetration Depth ◽  
Empirical Formula ◽  
High Strength Concrete ◽  
High Speed ◽  
High Strength ◽  
Local Damage ◽  
High Speed Impact ◽  
Rigid Projectile ◽  
Semi Empirical ◽  
The Impact

Based on the large amounts of field impact tests with different projectile nosed shapes, the abilities of the existing classical empirical and semi-empirical impact formulae in predicting the local damage of normal and high strength concrete targets (NSCT & HSCT) under the strike of rigid projectile were evaluated. It finds that, firstly, for the penetration depth, the Forrestal and Chen & Li semi-empirical formulae, BRL and Whiffen empirical formulae are advised for the NSCT under the impact of ogive nosed projectile; and Chen & Li semi-empirical formula and ACE empirical formulae are advised for the NSCT under the impact of special nosed projectile; the dimensionless penetration depth of NSCT increases linearly with the non-dimensional impact factor. Secondly, for the penetration depth, Chen & Li semi-empirical formula is advised for the HSCT under the mid-to-high speed impact, and the existing formulae are not applicable while the speed of the projectile was relatively low. Thirdly, for the perforation mode of the target, the BRL and Chang empirical formulae are advised for the NSCT, and the Chen semi-empirical formula, ACE and BRL empirical formulae are advised for the HSCT.

High and Low Speed Impact Characteristics of Nanocomposites

2015 ◽  
Vol 1105 ◽  
pp. 62-66 ◽  
Author(s):  
Saud Aldajah ◽  
Yousef Haik ◽  
Kamal Moustafa ◽  
Ammar Alomari
Keyword(s):  
High Speed ◽  
Impact Resistance ◽  
Absorption Capacity ◽  
Impact Testing ◽  
Energy Absorption Capacity ◽  
Low Speed ◽  
High Speed Impact ◽  
Bulletproof Vest ◽  
Impact Characteristics ◽  
The Impact

Nanocomposites attracted the attention of scientists due to their superior mechanical, thermal, chemical and electrical properties. This research studied the impact of adding carbon nanotubes (CNTs) to the woven Kevlar laminated composites on the high and low speed impact characteristics. Different percentages of CNTs were added to the woven Kevlar-Vinylester composite materials. An in-house developed drop weight testing apparatus was utilized for the low speed impact testing. Two different concentrations of the CNTs were added to a 15-layer woven Kevlar laminates, 0.32 wt% and 0.8 wt%. The results showed that: The 0.32 wt % CNT sample enhanced the interlaminar strength of the composite without enhancing the energy absorption capacity whereas, the 0.8 wt % CNT sample did not improve the impact resistance of the Kevlar composite.For the high speed impact tests, a bulletproof vest was prepared using woven Kevlar, resin, and CNTs at 1.5 w% percentage. The ballistic shooting was carried out by a professional shooter using a 30 caliber and 9 mm bullets for the tests. The CNT bulletproof sample bounced back the 30 caliber copper alloy bullet with no penetration.

Impact Behaviour of Composite Materials by Using Low and High Speed Impact Tests

2012 ◽  
Vol 445 ◽  
pp. 189-194
Author(s):  
Enver Bulent Yalcin ◽  
Volkan Gunay ◽  
Muzeyyen Marsoglu
Keyword(s):  
Composite Materials ◽  
High Speed ◽  
Impact Test ◽  
Woven Fabrics ◽  
Impact Behaviour ◽  
High Speed Impact ◽  
Impact Tests ◽  
Data Acquisition Software ◽  
Damage Process ◽  
The Impact

The study presents the need for instrumented testing to optimizing materials against impact forces. The objective of the study is how the impact behaviour of composite materials is investigated by slow and high speed impact tests. Instron Dynatup 9250HV and Instron Dynatup 8150 Impact test machines (Fig.1.) are used which are located in TUBITAK-MRC, Materials Institute , Impact Test Laboratory". The damage process in composite materials under low and high velocity impact loading and the impact energy-displacement properties of the composite materials were investigated. Composite samples were produced by woven fabrics. The results are given as graphs and tables. The Impulse Data Acquisition software is used to send the data to computer.

scholarly journals Preparation of poly(ionic liquid)/multi-walled carbon nanotube fillers using divinylbenzene as a linker to enhance the impact resistance of polyurethane elastomers

RSC Advances ◽  
2022 ◽  
Vol 12 (3) ◽  
pp. 1777-1787
Author(s):  
Zehui Xiang ◽  
Fan Hu ◽  
Xueyan Wu ◽  
Fugang Qi ◽  
Biao Zhang ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Carbon Nanotube ◽  
High Speed ◽  
Impact Resistance ◽  
Polyurethane Elastomers ◽  
High Speed Impact ◽  
Multi Walled Carbon Nanotube ◽  
Carbon Nanotube Composite ◽  
Poly Ionic Liquid ◽  
The Impact

Schematic diagram of multi-walled carbon nanotube composite ionic liquid synergistically enhancing the high-speed impact resistance of polyurethane elastomer.

scholarly journals Growth and instability of the liquid rim in the crown splash regime

2014 ◽  
Vol 752 ◽  
pp. 485-496 ◽  
Author(s):  
G. Agbaglah ◽  
R. D. Deegan
Keyword(s):  
Thin Film ◽  
High Speed ◽  
Unstable Mode ◽  
Linear Stability Theory ◽  
Scaling Relations ◽  
X Ray ◽  
X Ray Imaging ◽  
Secondary Droplets ◽  
The Impact ◽  
Good Agreement

AbstractWe study the formation, growth and disintegration of jets following the impact of a drop on a thin film of the same liquid for $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{We}<1000$ and $\mathit{Re}<2000$ using a combination of numerical simulations and linear stability theory (Agbaglah, Josserand & Zaleski, Phys. Fluids, vol. 25, 2013, 022103). Our simulations faithfully capture this phenomena and are in good agreement with experimental profiles obtained from high-speed X-ray imaging. We obtain scaling relations from our simulations and use these as inputs to our stability analysis. The resulting predictions for the most unstable wavelength are in excellent agreement with experimental data. Our calculations show that the dominant destabilizing mechanism is a competition between capillarity and inertia but that deceleration of the rim provides an additional boost to growth. We also predict over the entire parameter range of our study the number and timescale for formation of secondary droplets formed during a splash, based on the assumption that the most unstable mode sets the droplet number.

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