Effects of Loading Conditions and Skull Fracture on Load Transfer to Head

2017 ◽  
Vol 4 (2) ◽  
Author(s):  
Timothy G. Zhang ◽  
Kimberly A. Thompson ◽  
Sikhanda S. Satapathy
Keyword(s):  
Load Transfer ◽  
Skull Fracture ◽  
Material Model ◽  
Rigid Wall ◽  
Frontal Impact ◽  
Low Velocity ◽  
Smoothed Particle ◽  
Element Technique ◽  
Smoothed Particle Hydrodynamic ◽  
Skull Deformation

This study focuses on the effect of skull fracture on the load transfer to the head for low-velocity frontal impact of the head against a rigid wall or being impacted by a heavy projectile. The skull was modeled as a cortical–trabecular–cortical-layered structure in order to better capture the skull deformation and consequent failure. The skull components were modeled with an elastoplastic with failure material model. Different methods were explored to model the material response after failure, such as eroding element technique, conversion to fluid, and conversion to smoothed particle hydrodynamic (SPH) particles. The load transfer to the head was observed to decrease with skull fracture.

Role of Skull Fracture on Load Transfer to Brain

2016 ◽  
Author(s):  
Timothy G. Zhang ◽  
Kimberly A. Thompson ◽  
Sikhanda S. Satapathy
Keyword(s):  
Load Transfer ◽  
Skull Fracture ◽  
Material Model ◽  
Rigid Wall ◽  
Frontal Impact ◽  
Low Velocity ◽  
Element Technique ◽  
The Brain ◽  
Skull Deformation

This study focuses on the effect of skull fracture on the load transfer to brain for low velocity frontal impact of head against a rigid wall. The skull was modeled as a cortical-trabecular-cortical layered structure in order to better capture the skull deformation and consequent failure. The skull components were modeled with an elastoplastic with failure material model. Different methods were explored to model the material response after failure, such as eroding element technique, conversion to fluid, and conversion to SPH particles. The transmitted pressure in the brain was observed to increase with skull fracture.

scholarly journals A physically based material model for the simulation of friction stir welding

2020 ◽  
Vol 62 (6) ◽  
pp. 603-611
Author(s):  
Florian Panzer ◽  
Elizaveta Shishova ◽  
Martin Werz ◽  
Stefan Weihe ◽  
Peter Eberhard ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Material Model ◽  
Model Parameters ◽  
Strain Rates ◽  
Compression Tests ◽  
Friction Stir ◽  
Physically Based ◽  
Smoothed Particle ◽  
Series Aluminum Alloy ◽  
Smoothed Particle Hydrodynamic

AbstractA physically based material model, taking into account the interdependence of material microstructure and yield strength, is presented for an Al 5182 series aluminum alloy for the simulation of friction stir welding using continuum mechanics approaches. A microstructure evolution equation considering dislocation density and grain size is used in conjunction with a description of yield stress. In order to fit experimental stress-strain curves, obtained from compression tests at various strain rates and temperatures, phenomenological relationships are developed for some of the model parameters. The material model is implemented in smoothed particle hydrodynamic research code as well as in the commercial finite element code Abaqus. Simulations for various strain rates and temperatures were performed and compared with experimental results as well as between the two discretization methods in order to verify the material model and the implementation. Simulations provide not only an accurate approximation of stress based on temperature, strain rate, and strain but also an improved insight into the microstructural evolution of the material.

scholarly journals The impact of episodic outflow feedback on stellar multiplicity and the star formation efficiency

2020 ◽  
Vol 500 (3) ◽  
pp. 3594-3612
Author(s):  
P F Rohde ◽  
S Walch ◽  
S D Clarke ◽  
D Seifried ◽  
A P Whitworth ◽  
...  
Keyword(s):  
Star Formation ◽  
Hydrodynamic Simulations ◽  
The Core ◽  
Subgrid Model ◽  
High Incidence ◽  
Smoothed Particle ◽  
The Mean ◽  
Smoothed Particle Hydrodynamic ◽  
Formation Efficiency ◽  
The Impact

ABSTRACT The accretion of material on to young protostars is accompanied by the launching of outflows. Observations show that accretion, and therefore also outflows, are episodic. However, the effects of episodic outflow feedback on the core scale are not well understood. We have performed 88 smoothed particle hydrodynamic simulations of turbulent dense $1 \, {{\mathrm{M}}}_{\odot }$ cores to study the influence of episodic outflow feedback on the stellar multiplicity and the star formation efficiency (SFE). Protostars are represented by sink particles, which use a subgrid model to capture stellar evolution, inner-disc evolution, episodic accretion, and the launching of outflows. By comparing simulations with and without episodic outflow feedback, we show that simulations with outflow feedback reproduce the binary statistics of young stellar populations, including the relative proportions of singles, binaries, triples, etc. and the high incidence of twin binaries with q ≥ 0.95; simulations without outflow feedback do not. Entrainment factors (the ratio between total outflowing mass and initially ejected mass) are typically ∼7 ± 2, but can be much higher if the total mass of stars formed in a core is low and/or outflow episodes are infrequent. By decreasing both the mean mass of the stars formed and the number of stars formed, outflow feedback reduces the SFE by about a factor of 2 (as compared with simulations that do not include outflow feedback).

scholarly journals Ultra-deep tidal disruption events: prompt self-intersections and observables

2019 ◽  
Vol 488 (4) ◽  
pp. 5267-5278 ◽  
Author(s):  
Siva Darbha ◽  
Eric R Coughlin ◽  
Daniel Kasen ◽  
Chris Nixon
Keyword(s):  
Close Agreement ◽  
Tidal Disruption ◽  
X Ray ◽  
Analytic Estimate ◽  
Smoothed Particle ◽  
Solar Type ◽  
General Relativistic ◽  
Low Mass ◽  
Smoothed Particle Hydrodynamic ◽  
Schwarzschild Radius

ABSTRACT A star approaching a supermassive black hole (SMBH) can be torn apart in a tidal disruption event (TDE). We examine ultra-deep TDEs, a new regime in which the disrupted debris approaches close to the black hole’s Schwarzschild radius, and the leading part intersects the trailing part at the first pericentre passage. We calculate the range of penetration factors β versus SMBH masses M that produce these prompt self-intersections using a Newtonian analytic estimate and a general relativistic (GR) geodesic model. We find that significant self-intersection of Solar-type stars requires β ∼ 50–127 for M/M⊙ = 104, down to β ∼ 5.6–5.9 forM/M⊙ = 106. We run smoothed particle hydrodynamic (SPH) simulations to corroborate our calculations and find close agreement, with a slightly shallower dependence on M. We predict that the shock from the collision emits an X-ray flare lasting t ∼ 2 s with L ∼ 1047 erg s−1 at E ∼ 2 keV, and the debris has a prompt accretion episode lasting t ∼ several minutes. The events are rare and occur with a rate $\dot{N} \lesssim 10^{-7}$ Mpc−3 yr−1. Ultra-deep TDEs can probe the strong gravity and demographics of low-mass SMBHs.

scholarly journals Numerical–Experimental Correlation of Impact-Induced Damages in CFRP Laminates

2019 ◽  
Vol 9 (11) ◽  
pp. 2372 ◽  
Author(s):  
Andrea Sellitto ◽  
Salvatore Saputo ◽  
Francesco Di Caprio ◽  
Aniello Riccio ◽  
Angela Russo ◽  
...  
Keyword(s):  
Numerical Model ◽  
Composite Laminates ◽  
Transverse Direction ◽  
Material Model ◽  
Low Velocity ◽  
Cfrp Laminates ◽  
Experimental Correlation ◽  
Out Of Plane ◽  
Impact Phenomena ◽  
The Impact

Composite laminates are characterized by high mechanical in-plane properties and poor out-of-plane characteristics. This issue becomes even more relevant when dealing with impact phenomena occurring in the transverse direction. In aeronautics, Low Velocity Impacts (LVIs) may occur during the service life of the aircraft. LVI may produce damage inside the laminate, which are not easily detectable and can seriously degrade the mechanical properties of the structure. In this paper, a numerical-experimental investigation is carried out, in order to study the mechanical behavior of rectangular laminated specimens subjected to low velocity impacts. The numerical model that best represents the impact phenomenon has been chosen by numerical–analytical investigations. A user defined material model (VUMAT) has been developed in Abaqus/Explicit environment to simulate the composite intra-laminar damage behavior in solid elements. The analyses results were compared to experimental test data on a laminated specimen, performed according to ASTM D7136 standard, in order to verify the robustness of the adopted numerical model and the influence of modeling parameters on the accuracy of numerical results.

Numerical Simulation of Wave Breaking Over a Submerged Step with SPH Method

2018 ◽  
Vol 01 (02) ◽  
pp. 1840005 ◽  
Author(s):  
Hongjie Wen ◽  
Bing Ren ◽  
Guoyu Wang ◽  
Yumeng Zhao
Keyword(s):  
Wave Breaking ◽  
Sph Method ◽  
Vertical Distributions ◽  
Sph Model ◽  
Smoothed Particle ◽  
Mean Water Level ◽  
The Mean ◽  
Wave Maker ◽  
Wave Induced ◽  
Smoothed Particle Hydrodynamic

Wave breaking over a submerged step with a steep front slope and a wide horizontal platform is studied by smoothed particle hydrodynamic (SPH) method. By adding a momentum source term and a velocity attenuation term into the governing equation, a nonreflective wave maker system is introduced in the numerical model. A suitable circuit channel is specifically designed for the present SPH model to avoid the nonphysical rise of the mean water level on the horizontal platform of the submerged step. The predicted free surface elevations and the spatial distributions of wave height and wave setup over the submerged step are validated using the corresponding experimental data. In addition, the vertical distributions of wave-induced current over the submerged step are also investigated at both low and high tides.

Dynamic Energy Absorption Performances of Rain Forest Vehicle (RFV) under Frontal Impact

2014 ◽  
Vol 67 (3) ◽  
Author(s):  
M. S. Othman ◽  
Z. Ahmad
Keyword(s):  
Energy Absorption ◽  
Impact Energy ◽  
Impact Loading ◽  
Rain Forest ◽  
Experimental Testing ◽  
Rigid Wall ◽  
Crash Analysis ◽  
Frontal Impact ◽  
Frontal Section ◽  
The Impact

This paper treats the crash analysis and energy absorption response of Rain Forest Vehicle (RFV) subjected to frontal impact scenario namely impacting rigid wall and column. Dynamic computer simulation techniques validated by experimental testing are used to carry out a crash analysis of such vehicle. The study aims at quantifying the energy absorption capability of frontal section of RFV under impact loading, for variations in the load transfer paths and geometry of the crashworthy components. It is evident that the proposed design of the RFV frontal section are desirable as primary impact energy mitigation due to its ability to withstand and absorb impact loads effectively. Furthermore, it is found that the impact energy transmitted to the survival room may feasibly be minimized in these two impact events. The primary outcome of this study is design recommendation for enhancing the level of safety of the off-road vehicle where impact loading is expected.   

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