Dynamic Response of a Collidant Impacting a Low Pressure Airbag

There are many uses of low pressure airbags, both military and commercial. Many of these applications have been hampered by inadequate and inaccurate modeling tools. This dissertation contains the derivation of a four degree-of-freedom system of differential equations from physical laws of mass and energy conservation, force equilibrium, and the Ideal Gas Law. Kinematic equations were derived to model a cylindrical airbag as a single control volume impacted by a parallelepiped collidant. An efficient numerical procedure was devised to solve the simplified system of equations in a manner amenable to discovering design trends. The largest public airbag experiment, both in scale and scope, was designed and built to collect data on low-pressure airbag responses, otherwise unavailable in the literature. The experimental results were compared to computational simulations to validate the simplified numerical model. Experimental response trends are presented that will aid airbag designers. The two objectives of using a low pressure airbag to demonstrate the feasibility to 1) accelerate a munition to 15 feet per second velocity from a bomb bay, and 2) decelerate humans hitting trucks below the human tolerance level of 50 G\u27s, were both met

Mini-Workshop: Analytical and Numerical Methods in Image and Surface Processing

The workshop successfully brought together researchers from mathematical analysis, numerical mathematics, computer graphics and image processing. The focus was on variational methods in image and surface processing such as active contour models, Mumford-Shah type functionals, image and surface denoising based on geometric evolution problems in image and surface fairing, physical modeling of surfaces, the restoration of images and surfaces using higher order variational formulations

Modeling of High Pressure Confined Inflatable Structures

Safety of transportation tunnels is a top priority among transportation agencies and public administrators and a very important aspect in the daily operation of a tunnel system. However, it is always a challenge to create and integrate protection systems in existing tunnels to prevent or at least mitigate the occurrence of hazardous events such as spread of smoke or noxious fumes, flooding, among others. Typically there two ways for preventing or mitigating the occurrence of hazardous events: one is the implementation of permanent solutions and, the second one, is the use of temporary solutions. Permanent solutions usually have relatively high sealing efficiency due to their solid and rigid sealing mechanisms such as bulkheads and floodgates. However, they can be extremely expensive and sometimes difficult to build or install due to physical, economical or operational constraints. On the other hand, temporary solutions, which can be relatively low cost and easy to install, offer a temporary countermeasure while permanent repairs are implemented. The development of flexible structures, such as inflatable plugs for temporary solutions is becoming a viable alternative for protection of transportation tunnels and other similar critical civil infrastructure.;The Resilient Tunnel System (RTS) is a passive tunnel protection system developed at West Virginia University (WVU). This system is intended to prevent or minimize the damage induced by hazardous events by creating a compartment to contain the threat. The Resilient Tunnel System implements inflatable structures at specific locations of the tunnel to seal up the tunnel and create a compartment to isolate the compromised region. WVU has conducted several validation tests on full scale inflatable structures designed to mitigate flooding in an actual rail transportation tunnel and in specially built testing facilities. However, testing at full scale either in an actual tunnel or in specially built testing facilities, is a very complex and resource demanding task. It can take several iterations to achieve desired results which cannot be accurately predicted in advance. Therefore, the development of numerical models using Finite Element Analysis becomes imperative in order to: first, reproduce experimental work done at WVU using different prototypes at different scales; and then use the calibrated models as predicting tool that can anticipate the outcome of experiments and eventually reduce its number due to the intrinsic complexity and cost.;This dissertation aims to present the results of the development of Finite Element Models of confined inflatable structures designed to withstand flooding pressures. Models of different prototypes were created and analyzed in order to reproduce experimental results. Numerical results show that the adjusted models can reproduce experimental results, ranging from deployment, full pressurization and induced failure, with a great degree of accuracy providing a reliable predicting tool for evaluation of alternative configurations and parametric studies

THEORETICAL AND EXPERIMENTAL STUDY OF THE INTERIOR BALLISTICS OF A RIFLE 7.62

This study aims to examine theoretically and experimentally the interior ballistics of a rifle 7.62. Three theoretical methods are employed: the Vallier-Heydenreich, which is based on empirical data tables; the lumped parameters that is represented by a differential-algebraic system of equations, describing the propellant combustion, the thermodynamics of the gas inside the gun and the projectile dynamics; and the commercial software PRODAS. The theoretical solutions furnish the pressure, the projectile velocity and the projectile position inside the gun, the maximum pressure,the muzzle velocity and the total time of the interior ballistics. The experiments measure the pressure along of the time and the projectile velocity at seven meters ahead of the barrel. The proposed lumped parameter model indicates alternatives to model the energy lost and the resistance pressure functions. The theoretical solutions are compared with experiments. A thermodynamics analysis of the energy conversion in the gun is provided. The results are analyzed and the relevance of each method is highlighted

Research on the Vibration Damping Performance of a Novel Single-Side Coupling Hydro-Pneumatic Suspension

A mine dump truck is exposed to heavy load and harsh working environment. When the truck passes over the road bumps, it will cause the body to tilt and the tires to "jump off the ground" (JOTG), which will affect the stability and safety of the truck, and will cause impact damage to the body and suspension system. To avoid this situation, a kind of Novel Single-side Coupling Hydro-pneumatic Suspension (NSCHs) is presented. NSCHs consists of two cylinders in parallel, which are connected to the accumulator by rubber pipes and mounted on the same side of the dump truck. Theoretical analysis and experimental research were respectively carried out under the road and loading experimental condition. The experimental results show that compared to the conventional single cylinder hydro-pneumatic suspension, under the loading experiment condition, the maximum overshoot pressure of the NSCHs was reduced by 0.4 MPa and the impact oscillation time was shortened by 4.13 s, which plays the effective role in reducing vibration and absorbing energy. Further, it is found that the two cylinders are coupled during the working process, and the NSCHs system can achieve uniform loading and displacement compensation, thus the novel dump truck can avoid the occurrence of the JOTG phenomenon

Modeling the structure-permeability relationship for woven fabrics

The performance of woven fabric in many technical applications, such as airbags or reinforced composites, relates to fabric through-thickness permeability. A unified analytical model for woven fabric through-thickness permeability is proposed. It involves flow through gaps between yarns and within the yarns in terms of fabric porosity. The yarn permeability is a combination of flow along and transverse to unidirectional fibres. It is a function of fibre radius, fibre volume fraction, fibre array and crimp angle of interwoven yarns. The gap permeability is developed based on viscous and incompressible Hagen-Poiseuille flow in the gaps at low R_e values. The gap is simplified as a smooth fluid channel at the centre with slowly varying circular cross-section. The shape of the channel is approximated by a parabolic function. Volumetric flow rate is formulated as a function of pressure drop and flow channel geometry for the gap. The gap permeability is calculated thereafter according to Darcy’s law. For a woven fabric subjected to a high pressure load, an energy-based model is developed to predict the fabric out-of-plane deformation using minimum energy theory and an isotropic assumption for woven fabric. The model can predict the fabric maximum displacement and corresponding deflected profile across a diameter given a pressure load. The fabric deflection can be used to obtain the fabric elongation (strain) which results in the change of gap size, yarn width, yarn shape and fabric thickness in loose fabric (clear gaps between yarns) and the change of fibre volume fraction and crimp angle in tight fabric (overlapping yarns). The deformed fabric permeability is calculated by the unified permeability model based on the assumptions of the variation of geometric factors with deformation. If a woven fabric is subjected to a high decreasing pressure drop by air discharge, the fabric permeability is obtained by fitting pressure history and corresponding flow velocity using the Forchheimer equation. A nonlinear relationship is found between the pressure and velocity where the corresponding permeability is also called the dynamic permeability. The high pressure causes the shape of flow streamlines to vary in the gap between yarns (viewed as a converging-diverging duct). This flow behaviour is modelled by adding a non-Darcy term to Darcy’s law according to continuity theory and the Bernoulli equation. Therefore, a predictive Forchheimer equation is given for flow behaviour in a woven fabric based on the fabric geometry, structure and flow situation. The developed analytical models were verified by CFD simulations and experiments in this thesis. The comparisons showed good agreements. Sensitivity studies were conducted to understand the effects of geometric factors and mechanical properties on the fabric deformation and permeability. In this thesis, two pieces of equipment in particular were introduced for measuring the fabric dynamic permeability and fabric out-of-plane deformation. The measurements agreed well with their corresponding analytical predictions. Finally, the comparison of fabric deformation and non-Darcy flow showed the importance of fabric deformation in affecting the final fabric permeability

Automobile air bag inflation system based on fast combustion reaction

Current automobile air bag inflator technology is complex, expensive and environmentally unsafe. A new and novel air bag inflator based on fast combustion reactions of methane-oxygen mixtures has been developed and studied. The thermodynamics and mass flow parameters of this new inflator have been modeled and found to be in agreement with experimental results. The performance of the fast combustion inflator was evaluated in terms of pressure-time relationships inside the inflator and in a receiving tank simulating an air bag as well as the temperature-time relationship in the tank. In order to develop this fast combustion inflator, several critical issues were studied and evaluated. These included the effects of stoichiometry, initial mixture pressure and extreme hot and cold conditions. Other design and practical parameters, such as burst disk thickness and type, ignition device, tank purging gas, concentration of carbon monoxide produced and severity of temperature in the tank were also studied and optimized. Several inflator sizes were investigated and found to meet most of the requirements for a successful air bag inflator. A theoretical and integrated model has been developed to simulate the transient pressure and temperature as well as the mass flow rate from the inflator to the tank. The model is based on the change in the internal energy inside the inflator and the receiving tank as the mass flows from the inflator to the tank. The model utilizes the Chemical Equilibrium Compositions and Applications code developed by NASA to estimate the equilibrium conditions in the inflator. A large volume of experimental results made at different conditions were found to be in agreement with the integrated model. The fast combustion inflator developed during this research is simple in principle and construction and is environmentally attractive

Airbag system for hip-fracture protection due to falls: mechanical system design and development.

Chan Cheung Shing.Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.Includes bibliographical references (leaves 88-90).Abstracts in English and Chinese.Abstract --- p.iiAcknowledgements --- p.ivTable of Contents --- p.vList of Figures --- p.viiiList of Tables --- p.xiiAbbreviations and Notations --- p.xiiiChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Background and Objective --- p.1Chapter 1.2 --- Contribution --- p.4Chapter 1.3 --- Thesis Outline --- p.5Chapter Chapter 2 --- System Architecture --- p.6Chapter 2.1 --- Conceptual Design --- p.6Chapter 2.2 --- Sensing Device and Fall-Detection Algorithm --- p.7Chapter 2.3 --- Mechanical Part --- p.10Chapter Chapter 3 --- Mechanical Design --- p.11Chapter 3.1 --- Similar Products --- p.11Chapter 3.1.1 --- Airbag Restraining Systems in Automobiles --- p.11Chapter 3.1.2 --- Airbag Jackets for Motorcycle and House Riders --- p.12Chapter 3.2 --- Mechanism adopted --- p.12Chapter 3.2.1 --- Time Requirement of Inflator --- p.12Chapter 3.2.2 --- Mechanism and Design --- p.13Chapter 3.2.3 --- Actuator --- p.14Chapter 3.2.4 --- Punch --- p.15Chapter 3.2.5 --- Airbags --- p.18Chapter 3.2.6 --- Other Mechanisms Tried --- p.19Chapter 3.3 --- Prototype --- p.21Chapter 3.3.1 --- Implementation --- p.21Chapter 3.3.2 --- Demonstration --- p.23Chapter Chapter 4 --- Inflation Estimation --- p.25Chapter 4.1 --- Theory and Model --- p.25Chapter 4.2 --- Validation of Model --- p.28Chapter 4.2.1 --- Testing Equipment --- p.28Chapter 4.2.2 --- Preprocessing of Pressure Sensor Outputs --- p.28Chapter 4.2.3 --- Validation for Basic Equations --- p.29Chapter 4.2.4 --- Adjustment of Discharge Coefficients --- p.36Chapter 4.2.5 --- Validation for Discharging to a Fixed Volume --- p.40Chapter 4.2.6 --- Estimation of the Size of Airbag's Leakage Hole --- p.45Chapter 4.2.7 --- Validation for Discharging to an Airbag --- p.47Chapter 4.2.8 --- Time Delay due to Addition of a Pipe --- p.52Chapter 4.3 --- Summary of Experiments --- p.53Chapter 4.4 --- Limitation of Model --- p.54Chapter 4.5 --- Prediction of Inflation Time and Airbag Pressure --- p.55Chapter 4.5.1 --- Effects of Orifice Size and Vent Size on Airbag Pressure and Volume --- p.55Chapter Chapter 5 --- Force Attenuation Estimation --- p.58Chapter 5.1 --- Theory and Model --- p.58Chapter 5.1.1 --- Kelvin-Voigt Model --- p.59Chapter 5.1.2 --- Standard Linear Solid Support Model --- p.59Chapter 5.2 --- Simple Testing for Validation --- p.61Chapter 5.3 --- Summary of Experiment --- p.64Chapter 5.4 --- Estimation --- p.64Chapter 5.4.1 --- Force Attenuation Ability of Prototype --- p.64Chapter 5.4.2 --- Minimum Airbag Volume and Pressure Required to Reduce the Force --- p.65Chapter Chapter 6 --- Future Work --- p.66Chapter 6.1 --- Impact Test for Airbag System --- p.66Chapter 6.2 --- The Effective Mass of the Target User --- p.67Chapter 6.3 --- The Motion Data Collection --- p.68Chapter 6.4 --- Modification in the Inflator --- p.69Chapter Chapter 7 --- Conclusion --- p.70Appendix A Review of Basic Thermodynamics and Fluid Dynamics --- p.72Chapter A.1 --- Thermodynamics --- p.72Chapter A.2 --- Fluid Mechanics: Incompressible and Compressible Flow --- p.75Appendix B Derivation of Equations --- p.77Chapter B.1 --- Mass Flow Rate Equations --- p.77Chapter B.2 --- Relationship between Rate of Changes of Airbag Pressure and Volume --- p.80Chapter B.3 --- Pressure Change of Compressed Gas Cylinder --- p.82Chapter B.4 --- Dominating Factors in the Mass Flow Rate Equation --- p.83Appendix C Dimensions of Inflator --- p.85Appendix D Experimental Data --- p.8

Autonomous Vehicles

This edited volume, Autonomous Vehicles, is a collection of reviewed and relevant research chapters, offering a comprehensive overview of recent developments in the field of vehicle autonomy. The book comprises nine chapters authored by various researchers and edited by an expert active in the field of study. All chapters are complete in itself but united under a common research study topic. This publication aims to provide a thorough overview of the latest research efforts by international authors, open new possible research paths for further novel developments, and to inspire the younger generations into pursuing relevant academic studies and professional careers within the autonomous vehicle field

Modeling the structure-permeability relationship for woven fabrics

The performance of woven fabric in many technical applications, such as airbags or reinforced composites, relates to fabric through-thickness permeability. A unified analytical model for woven fabric through-thickness permeability is proposed. It involves flow through gaps between yarns and within the yarns in terms of fabric porosity. The yarn permeability is a combination of flow along and transverse to unidirectional fibres. It is a function of fibre radius, fibre volume fraction, fibre array and crimp angle of interwoven yarns. The gap permeability is developed based on viscous and incompressible Hagen-Poiseuille flow in the gaps at low R_e values. The gap is simplified as a smooth fluid channel at the centre with slowly varying circular cross-section. The shape of the channel is approximated by a parabolic function. Volumetric flow rate is formulated as a function of pressure drop and flow channel geometry for the gap. The gap permeability is calculated thereafter according to Darcy’s law. For a woven fabric subjected to a high pressure load, an energy-based model is developed to predict the fabric out-of-plane deformation using minimum energy theory and an isotropic assumption for woven fabric. The model can predict the fabric maximum displacement and corresponding deflected profile across a diameter given a pressure load. The fabric deflection can be used to obtain the fabric elongation (strain) which results in the change of gap size, yarn width, yarn shape and fabric thickness in loose fabric (clear gaps between yarns) and the change of fibre volume fraction and crimp angle in tight fabric (overlapping yarns). The deformed fabric permeability is calculated by the unified permeability model based on the assumptions of the variation of geometric factors with deformation. If a woven fabric is subjected to a high decreasing pressure drop by air discharge, the fabric permeability is obtained by fitting pressure history and corresponding flow velocity using the Forchheimer equation. A nonlinear relationship is found between the pressure and velocity where the corresponding permeability is also called the dynamic permeability. The high pressure causes the shape of flow streamlines to vary in the gap between yarns (viewed as a converging-diverging duct). This flow behaviour is modelled by adding a non-Darcy term to Darcy’s law according to continuity theory and the Bernoulli equation. Therefore, a predictive Forchheimer equation is given for flow behaviour in a woven fabric based on the fabric geometry, structure and flow situation. The developed analytical models were verified by CFD simulations and experiments in this thesis. The comparisons showed good agreements. Sensitivity studies were conducted to understand the effects of geometric factors and mechanical properties on the fabric deformation and permeability. In this thesis, two pieces of equipment in particular were introduced for measuring the fabric dynamic permeability and fabric out-of-plane deformation. The measurements agreed well with their corresponding analytical predictions. Finally, the comparison of fabric deformation and non-Darcy flow showed the importance of fabric deformation in affecting the final fabric permeability