Restraint Systems in Tactical Vehicles: Uncertainty Study Involving Airbags, Seatbelts and Military Gear

2017 ◽  
Author(s):  
Dorin Drignei ◽  
Zissimos P. Mourelatos ◽  
Ervisa Zhamo ◽  
Jingwen Hu ◽  
Cong Chen ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Body Size ◽  
Injury Risk ◽  
Finite Element Models ◽  
Risk Distribution ◽  
Frontal Crashes ◽  
Safety Features ◽  
The Impact

Adding advanced safety features (e.g. airbags) to restraint systems in tactical vehicles could decrease the injury risk of their occupants. The impact of frontal crashes on the occupants has been assessed recently through experimental data and finite element models. However, the number of such experiments is relatively small due to high cost. In this paper, we conduct an uncertainty study to infer the advantage of including advanced safety features, if a larger number of experiments were possible. We introduce the concept of group injury risk distribution that allows us to quantify under uncertainty the injury risk associated with advanced safety features, while averaging out the effect of uncontrollable factors such as body size. Statistically, the group injury risk distribution is a mixture of individual injury risk distributions of design conditions in the group. We infer that advanced safety features reduce the injury risk by at least two thirds in frontal crashes.

Restraint Systems in Tactical Vehicles: Uncertainty Study Involving Airbags, Seatbelts, and Military Gear

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Dorin Drignei ◽  
Zissimos P. Mourelatos ◽  
Ervisa Zhamo ◽  
Jingwen Hu ◽  
Cong Chen ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Body Size ◽  
Injury Risk ◽  
Risk Distribution ◽  
Frontal Crashes ◽  
Safety Features ◽  
The Impact

Adding advanced safety features (e.g., airbags) to restraint systems in tactical vehicles could decrease the injury risk of their occupants. The impact of frontal crashes on the occupants has been assessed recently through experimental data and finite element (FE) models. However, the number of such experiments is relatively small due to high cost. In this paper, we conduct an uncertainty study to infer the advantage of including advanced safety features, if a larger number of experiments were possible. We introduce the concept of group injury risk distribution that allows us to quantify under uncertainty the injury risk associated with advanced safety features, while averaging out the effect of uncontrollable factors such as body size. Statistically, the group injury risk distribution is a mixture of individual injury risk distributions of design conditions in the group. We infer that advanced safety features have the potential to reduce substantially injury risk in frontal crashes.

Behavior of Structures Using Simple Plastic Hinge Theory

1994 ◽  
Author(s):  
Ramakrishnan Maruthayappan ◽  
Hamid M. Lankarani
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Cantilever Beam ◽  
Reliable Method ◽  
Plastic Hinge ◽  
Element Model ◽  
Finite Element Models ◽  
Computational Program ◽  
Hinge Model ◽  
The Impact

Abstract The behavior of structures under the impact or crash situations demands an efficient modeling of the system for its behavior to be predicted close to practical situations. The various formulations that are possible to model such systems are spring mass models, finite element models and plastic hinge models. Of these three techniques, the plastic hinge theory offers a more accurate model compared to the spring mass formulation and is much simpler than the finite element models. Therefore, it is desired to model the structure using plastic hinges and to use a computational program to predict the behavior of structures. In this paper, the behavior of some simple structures, ranging from an elementary cantilever beam to a torque box are predicted. It is also shown that the plastic hinge theory is a reliable method by comparing the results obtained from a plastic hinge model of an aviation seat structure with that obtained from a finite element model.

Experimental and Numerical Plastic Response and Failure of Laterally Impacted Rectangular Plates

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
B. Liu ◽  
R. Villavicencio ◽  
C. Guedes Soares
Keyword(s):  
Finite Element ◽  
Numerical Simulations ◽  
Failure Modes ◽  
Mesh Size ◽  
Plastic Behavior ◽  
Finite Element Models ◽  
Rectangular Plates ◽  
Marine Structures ◽  
Fine Mesh ◽  
The Impact

Experimental and numerical results of drop weight impact test are presented on the plastic behavior and fracture of rectangular plates stuck laterally by a mass with a hemispherical indenter. Six specimens were tested in order to study the influence of the impact velocity and the diameter of the indenter. The impact scenarios could represent abnormal actions on marine structures, such as ship collision and grounding or dropped objects on deck structures. The tests are conducted on a fully instrumented impact tester machine. The obtained force-displacement response is compared with numerical simulations, performed by the LS-DYNA finite element solver. The simulations aim at proposing techniques for defining the material and restraints on finite element models which analyze the crashworthiness of marine structures. The mesh size and the critical failure strain are predicted by numerical simulations of the tensile tests used to obtain the mechanical properties of the material. The experimental boundary conditions are modeled in order to represent the reacting forces developed during the impact. The results show that the critical impact energy until failure is strongly sensitive to the diameter of the striker. The shape of the failure modes is well predicted by the finite element models when a relatively fine mesh is used. Comments on the process of initiation and propagation of fracture are presented.

Trabecular Surface Remodeling Simulation for Cancellous Bone Using Microstructural Voxel Finite Element Models

2001 ◽  
Vol 123 (5) ◽  
pp. 403-409 ◽  
Author(s):  
Taiji Adachi ◽  
Ken-ichi Tsubota ◽  
Yoshihiro Tomita ◽  
Scott J. Hollister
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Cancellous Bone ◽  
Applied Load ◽  
Morphological Changes ◽  
Finite Element Models ◽  
Structural Level ◽  
Loading Direction ◽  
Surface Remodeling ◽  
Trabecular Surface

A computational simulation method for three-dimensional trabecular surface remodeling was proposed, using voxel finite element models of cancellous bone, and was applied to the experimental data. In the simulation, the trabecular microstructure was modeled based on digital images, and its morphological changes due to surface movement at the trabecular level were directly expressed by removing/adding the voxel elements from/to the trabecular surface. A remodeling simulation at the single trabecular level under uniaxial compressive loading demonstrated smooth morphological changes even though the trabeculae were modeled with discrete voxel elements. Moreover, the trabecular axis rotated toward the loading direction with increasing stiffness, simulating functional adaptation to the applied load. In the remodeling simulation at the trabecular structural level, a cancellous bone cube was modeled using a digital image obtained by microcomputed tomography (μCT), and was uniaxially compressed. As a result, the apparent stiffness against the applied load increased by remodeling, in which the trabeculae reoriented to the loading direction. In addition, changes in the structural indices of the trabecular architecture coincided qualitatively with previously published experimental observations. Through these studies, it was demonstrated that the newly proposed voxel simulation technique enables us to simulate the trabecular surface remodeling and to compare the results obtained using this technique with the in vivo experimental data in the investigation of the adaptive bone remodeling phenomenon.

Techniques in Finite Element Modeling of Helmeted-Head Biomechanics

2009 ◽  
Author(s):  
Andrzej Przekwas ◽  
X. G. Tan ◽  
Z. J. Chen ◽  
Xianlian Zhou ◽  
Debbie Reeves ◽  
...  
Keyword(s):  
Finite Element ◽  
Brain Injury ◽  
Injury Risk ◽  
High Energy ◽  
Dense Layer ◽  
Hard Material ◽  
Absorption Mechanism ◽  
Military Applications ◽  
Main Components ◽  
The Impact

Generally a helmet comprises two main components: the shell and the fitting system. Despite the variations in designs due to the different usage requirements, typically helmets are intended to protect the user’s head through an energy absorption mechanism. The weight and volume are important factors in helmet design since both may alter the injury risk to the head and neck. The helmet outer shell is usually made of hard material that will deform when it is hit by hard objects. This action disperses energy from the impact to lessen the force before it reaches the head. The fitting system frequently includes a dense layer that cushions and absorbs the energy as a result of relative motion between the helmet and the head. A balance needs to be achieved on how strong and how stiff a helmet should be to provide the best possible protection. If a helmet is too stiff it can be less able to prevent brain injury in the kinds of impacts that may occur. If it is too flexible or soft, it might not protect the user in a violent, high-energy crash. For military applications, the requirements for helmet performance may be even more demanding. Not only do helmets have to protect a Soldier’s head from blunt impacts, but helmets also are expected to provide mounting platforms for ancillary devices and to function in ballistic and blast events as well.

Cemented Wellbore Experiments Reveals That Cement Interface Debonding Modeling Overestimate Potential Leakage Rates

2020 ◽  
Author(s):  
Zachary Speer ◽  
Jarrett Wise ◽  
Runar Nygaard ◽  
Geir Hareland ◽  
Eric Ford ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Models ◽  
Interface Debonding ◽  
Finite Element Models ◽  
Wellbore Integrity ◽  
Cement Interface ◽  
Abandoned Wells ◽  
Numerical Finite Element ◽  
Physical And Chemical

Abstract Leakage pathways may develop in wellbores during construction, production, or during and after plug and abandonment (P&A). These pathways are created due to events and conditions during cementing operations, or because of physical and chemical changes after cementing such as changes in temperature and wellbore pressures, and deterioration of the cement. Common leakage pathways develop inside the cement sheath, or as microannuli along the cement-tubing interface. Numerous evidence exists showing that wellbores leak, but there is no verified method to determine if a well will leak or not. To ensure long term wellbore integrity, leakage risks need to be evaluated for plugged and abandoned wells. To evaluate leakage risks from plugged and abandoned wells, numerical finite element models have been developed and used to investigate leakage scenarios during the life of the well. Currently, little work has been done to verify finite element numerical models with experimental data regarding flowpath size in cement sheaths. The aim of this paper is to model previously published experimental data to determine if the finite element models can accurately predict leakage potentials. Two lengths of cemented annuli were modeled, each with conventional and expanding cement to replicate the Aas et. al. [1] experiments. The numerical results show that the simulated microannuli overestimate flow rate compared to experimental data, indicating that flow path dimensions and/or fluid friction factor does not accurately represent the fluid flow in the experiments.

scholarly journals On the Biomechanics of Cardiac S-Looping in the Chick: Insights From Modeling and Perturbation Studies

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Ashok Ramasubramanian ◽  
Xavier Capaldi ◽  
Sarah A. Bradner ◽  
Lianna Gangi
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
The Body ◽  
Congenital Defects ◽  
Finite Element Models ◽  
Heart Tube ◽  
Dorsal Wall ◽  
Embryonic Developmental Stage ◽  
Cervical Flexure ◽  
Shape Changes

Cardiac looping is an important embryonic developmental stage where the primitive heart tube (HT) twists into a configuration that more closely resembles the mature heart. Improper looping leads to congenital defects. Using the chick embryo as the experimental model, we study cardiac s-looping wherein the primitive ventricle, which lay superior to the atrium, now assumes its definitive position inferior to it. This process results in a heart loop that is no longer planar with the inflow and outflow tracts now lying in adjacent planes. We investigate the biomechanics of s-looping and use modeling to understand the nonlinear and time-variant morphogenetic shape changes. We developed physical and finite element models and validated the models using perturbation studies. The results from experiments and models show how force actuators such as bending of the embryonic dorsal wall (cervical flexure), rotation around the body axis (embryo torsion), and HT growth interact to produce the heart loop. Using model-based and experimental data, we present an improved hypothesis for early cardiac s-looping.

scholarly journals Finite Element Simulations of the ID Venous System to Treat Venous Compression Disorders: From Model Validation to Realistic Implant Prediction

2021 ◽  
Author(s):  
Alissa Zaccaria ◽  
Francesco Migliavacca ◽  
David Contassot ◽  
Frederic Heim ◽  
Nabil Chakfe ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Element Model ◽  
Venous System ◽  
Venous Compression ◽  
Risk Of Rupture ◽  
Model Reliability ◽  
The Impact ◽  
Force Displacement ◽  
Realistic Geometry

AbstractThe ID Venous System is an innovative device proposed by ID NEST MEDICAL to treat venous compression disorders that involve bifurcations, such as the May-Thurner syndrome. The system consists of two components, ID Cav and ID Branch, combined through a specific connection that prevents the migration acting locally on the pathological region, thereby preserving the surrounding healthy tissues. Preliminary trials are required to ensure the safety and efficacy of the device, including numerical simulations. In-silico models are intended to corroborate experimental data, providing additional local information not acquirable by other means. The present work outlines the finite element model implementation and illustrates a sequential validation process, involving seven tests of increasing complexity to assess the impact of each numerical uncertainty separately. Following the standard ASME V&V40, the computational results were compared with experimental data in terms of force-displacement curves and deformed configurations, testing the model reliability for the intended context of use (differences < 10%). The deployment in a realistic geometry confirmed the feasibility of the implant procedure, without risk of rupture or plasticity of the components, highlighting the potential of the present technology.

Experimental and Modeling Studies for Understanding Shoe-Floor-Contaminant Friction and Designing for Slip-Resistance

2012 ◽  
Author(s):  
Kurt Beschorner
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Boundary Lubrication ◽  
Viscous Fluids ◽  
Finite Element Models ◽  
Sliding Speed ◽  
Friction Coefficients ◽  
Real Area Of Contact ◽  
Lubrication Regime ◽  
Real Area

Insufficient friction at the shoe-floor interface causes a large number of slip and falling accidents each year. Developing solutions for enhancing shoe-floor-contaminant friction requires understanding the mechanisms that contribute to slippery surfaces. Over the past several years, our research group has conducted several experimental and modeling studies to reveal the critical tribological mechanisms contributing to shoe-floor-contaminant friction. This extended abstract will discuss the findings of these studies to: 1) determine the lubrication regime(s) that is/are most relevant to under-shoe conditions during slipping; 2) quantify how under-shoe conditions, shoes and flooring affect the two main contributions to boundary lubrication: adhesion and hysteresis; and 3) describe how this information can be used to design slip-resistant shoes and flooring. To identify the lubrication regime, interfacial pressures at the shoe-floor-contaminant interface were measured and coefficient of friction was monitored. Low viscous fluids and shoes with at least 2mm of tread were found to have negligible interfacial pressures and moderate friction coefficients (0.07–0.40). Untreaded shoes combined with high viscous fluids led to high interfacial pressures that supported up to 40% of the normal load and low friction coefficients (<0.01). These results suggest that mixed/elasto-hydrodynamic lubrication is relevant in some untreaded conditions but that boundary lubrication is relevant for most other conditions. In boundary lubrication, the primary factors contributing to friction are adhesion and hysteresis. Experimental data and finite element models demonstrate that hysteresis friction increases with floor roughness and the ratio of shoe to floor hardness. Adhesion friction is dependent on real area of contact and the shear stress required to break junctions. Experimental data suggests that adhesion is dependent on the fluid lubricant, sliding speed, floor roughness and shoe material. Finite element models confirm that a reduction in the real area of contact occurs with increasing floor roughness and sliding speed, consistent with the experimental adhesion effects. Ensuring that the shoe-floor-fluid interface is operating in the boundary lubrication regime requires establishing minimum tread threshold for fluid lubricants that are likely to be found in a given environment. Designing a high hysteresis shoe-floor combination is preferred because it is relatively unaffected by fluid contaminants or under-shoe conditions (i.e. sliding speed). Therefore, ensuring a minimum tread depth is used along with increasing floor roughness and shoe to floor hardness may be effective in addition to minimum tread thresholds.

HYPER-ELASTIC PARAMETER ESTIMATION OF HUMAN HEEL-PAD: A FINITE ELEMENT AND EVOLUTIONARY BASED ALGORITHM

2012 ◽  
Vol 12 (03) ◽  
pp. 1250034 ◽  
Author(s):  
M. M. KHANI ◽  
H. KATOOZIAN ◽  
K. AZMA ◽  
I. NASEH ◽  
A. H. SALIMI
Keyword(s):  
Experimental Data ◽  
Genetic Algorithm ◽  
Finite Element ◽  
Nonlinear Material ◽  
Elastic Behavior ◽  
Diabetic Patients ◽  
Initial Contact ◽  
Heel Pad ◽  
Hyper Elastic ◽  
The Impact

The heel-pad as a biological shock absorber has an important role in the initial contact phase of gait cycle dissipating the impact forces resulted in locomotion. An axisymmetric finite element model of human heel-pad has been generated and the heel-pad experimental data deduced from a published force-deflection graph of the same specimen (Iain R. Spears, Janice E. Miller-Young), Iterative identification task has been used to extract nonlinear material properties describing hyper-elastic behavior of heel-pad. The genetic algorithm was incorporated into estimation process using an interface program. Two parameters of hyper-elastic materials potential energy function represented by Mooney–Rivlin were determined by using the genetic algorithm technique to minimize the displacement error between the experimental data and the corresponding finite element results after a considerable number of iterations. The result can be used for design and construction of synthetic heel-pad and therapeutic foot wear as well as insoles, especially for diabetic patients.

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