Airbag Inflation Research Articles

An experimental air bag test system for the study of air bag deployment Loads

An Air Bag Test System (ATS) to study air bag-occupant interactions during close proximity deployment has been developed as a research tool to experimentally simulate controllable and repeatable air bag deployments against targets with various standoff distances. The ATS was calibrated to replicate target response to an arbitrarily selected commercially-available air bag inflator type. A mathematical model was developed to describe the ATS deployment with favourable validation. The model follows an integral approach that treats the unfolding of the bag during deployment as a uniform thinning surface with specified volume-area functions. The model was used to explain the experimental data and provide insight into the energy partition during a deployment including the effects of varying inflator temperature and vent holes on target contact load. The ATS and the model were used to generate benchmark data for computational model and code development validations. One air bag type was studied giving results that are extendable to a wide variety of fleet air bags. Results provided insights on the effects of inflation energy and mass flow on target response. They show that only a very small fraction (3%) of the total deployment energy is delivered to a target. while 60% is stored in the air bag. For a sealed bag, the target response is independent of inflator temperature if the total energy is held constant. Venting reduces the target load primarily during the final pressurization (membrane) phase. For a vented bag, the target velocity decreases with higher inflator temperature.

Prediction of Airbag Inflator Performance

Prediction of Airbag Inflator Performance

Severe ocular injury associated with airbag inflation

Severe ocular injury associated with airbag inflation

Fully C1‐conforming subdivision elements for finite deformation thin‐shell analysis

AbstractWe have extended the subdivision shell elements of Cirak et al. [18] to the finite‐deformation range. The assumed finite‐deformation kinematics allows for finite membrane and thickness stretching, as well as for large deflections and bending strains. The interpolation of the undeformed and deformed surfaces of the shell is accomplished through the use of subdivision surfaces. The resulting ‘subdivision elements’ are strictly C1‐conforming, contain three nodes and one single quadrature point per element, and carry displacements at the nodes only. The versatility and good performance of the subdivision elements is demonstrated with the aid of a number of test cases, including the stretching of a tension strip; the inflation of a spherical shell under internal pressure; the bending and inflation of a circular plate under the action of uniform pressure; and the inflation of square and circular airbags. In particular, the airbag solutions, while exhibiting intricate folding patterns, appear to converge in certain salient features of the solution, which attests to the robustness of the method. Copyright © 2001 John Wiley & Sons, Ltd.

Fully C1‐conforming subdivision elements for finite deformation thin‐shell analysis

We have extended the subdivision shell elements of Cirak et al. [18] to the finite-deformation range. The assumed finite-deformation kinematics allows for finite membrane and thickness stretching, as well as for large deflections and bending strains. The interpolation of the undeformed and deformed surfaces of the shell is accomplished through the use of subdivision surfaces. The resulting ‘subdivision elements’ are strictly C1-conforming, contain three nodes and one single quadrature point per element, and carry displacements at the nodes only. The versatility and good performance of the subdivision elements is demonstrated with the aid of a number of test cases, including the stretching of a tension strip; the inflation of a spherical shell under internal pressure; the bending and inflation of a circular plate under the action of uniform pressure; and the inflation of square and circular airbags. In particular, the airbag solutions, while exhibiting intricate folding patterns, appear to converge in certain salient features of the solution, which attests to the robustness of the method.

Burn injuries caused by air bag deployment

Automobile air bags have gained acceptance as an effective measure to reduce the morbidity and mortality associated with motor vehicle accidents. As more cars have become equipped with them, new problems have been encountered that are directly attributable to the deployment of the bag itself. An increasing variety of associated injuries has been reported, including minor burns. We present two automobile drivers who were involved in front-impact crashes with air bag inflation. They sustained superficial and partial-thickness burns related to the deployment. The evaluation of these cases shows mechanisms involved in burn injuries caused by the air bag system. Most of the burns are chemical and usually attributed to sodium hydroxide in the aerosol created during deployment. Also direct thermal burns from high-temperature gases or indirect injuries due to the melting of clothing, as well as friction burns from physical contact are possible. However, the inherent risks of air bag-related burns are still outweighed by the benefits of preventing potentially life-threatening injuries.

Theoretical simulation of combustion processes of airbag inflators

Combustion and inflation processes of pyrotechnic airbag inflators are simulated by a theoretical model and numerical code developed in this study. The theoretical model considers the ignition and combustion of gas generation propellants of an inflator located in a constant-volume discharge tank. The model is based on the transient conservation equations of mass, species and energy for the combustion chamber of the inflator and the discharge tank. In addition, the model also includes the propellant burning rate law, the ignition model of gas generation propellants, real gas equation of state, effect of mass and energy fluxes from the igniter to the combustion chamber, heat transfer correlations and filter clogging processes. The theoretical model is solved by a numerical code. The calculated results agree well with experimental data. Simulation results indicate that the gas properties in the combustion chamber and the discharge tank change in different fashions owing to the large difference in the volumes of the two regions. In general, the gas properties in the discharge tank vary slowly, continuously and almost monotonically. It is found that the increase in the pressure exponent of the burning rate law and the inertia coefficient of the filter will increase the peak pressures in both regions. The major effect of an increasing mass flowrate from the igniter is the introduction of a local pressure peak in the combustion chamber at the very beginning of the combustion processes.

Detailed simulation of the Airbag Inflation Process Using a Coupled CFD/FE Method

There is increasing pressure to reduce injuries and fatalities by effectively using airbags for side impact and out-of-position impact loading conditions. The simulation of these scenarios is particularly difficult as the occupant is interacting with the airbag at early times during the airbag deployment when the detailed behaviour of the airbag can have a significant effect. A new airbag inflation simulation capability that overcomes this problem has been integrated into the crash simulation software MADYMO. This allows accurate simulation of the gas flow within the airbag throughout the inflation and unfolding process. The new module uses CFD techniques to numerically model the interior volume of the airbag in detail. The pressure field within the airbag is directly coupled to the standard WYMO FE model of the airbag. Hence, the acceleration and movement of the airbag and any bodies in contact with it can be predicted more accurately.

Mathematical Simulation of Airbag Inflation by Low Temperature Gas Generator Products

A mathematical model is described analyzing the processes during the combustion of a solid propellant gas generator for airbags. Results on parameter variations are presented. For porous and granulate charges the dynamic parameters of the gas flow and the progress of the ignition of the propellant are determined. Mathematische Simulation der Airbagfüllung durch die Produkte eines Niedertemperatur-Gasgenerators Es wird ein mathematisches Modell beschrieben, das die Vorgänge beim Abbrand eines festen Treibstoffes in Airbag-Gasgeneratoren analysiert. Ergebnisse von Parametervariationen werden dargestellt. Für poröse und granulare Ladungen wurden die dynamischen Parameter der Gasströmungen und der Fortschritt der Anzündung des Treibstoffes bestimmt. Simulation mathématique du déploiement d'un coussin gonflable avec les produits d'un générateur de gaz basse température On décrit un modèle mathématique qui analyse les processus lors de la combustion d'un propergol solide dans des générateurs de gaz d'airbag. On présente des résultats en fonction des variations de paramètres. On a déterminé les paramètres dynamiques de l'écoulement gazeux et la progression de l'allumage du propergol pour des charges poreuses et granulaires.

Small Female Upper Extremity Interaction with a Deploying Side Air Bag

This paper presents a study characterizing the interaction between a deploying side air bag and a small female upper extremity. The results are based on twelve tests with small female cadavers, and fifteen tests with the instrumented SAE 5th percentile female upper extremity attached to the 5th percentile Hybrid III female dummy. The upper extremity was loaded by a deploying seat mounted thoracic side air bag in a static test environment. Three inflators were used that varied in peak pressure and pressure onset rate. Despite kinematic differences between the dummy and cadaver, the moments recorded in the cadaver and dummy were similar. Chondral and osteochondral fractures in the cadaver elbow joints were identified in seven of the twelve cadaver tests, while a simple fracture of the distal humerus head was observed in one test. A linear logistic regression analysis was performed to correlate occurrence of recorded injury and the test parameters. Injury risk functions were constructed using age, forearm acceleration, elbow moment, and air bag inflator level as variables.

Modeling of an Air Bag Inflator Based on Combustion of Methane-Oxygen Mixture

A new air bag inflator based on the combustion reactions of methane-oxygen mixtures has been developed and modeled. The performance of this inflator was evaluated in terms of pressure-lime relationships inside the inflator and in a receiving tank simulating an air bag as well as the temperature-time relationship in the tank. A theoretical model has been developed to simulate the transient pressure, temperature and 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 lank 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 and the mass fractions of the product species. The model predicts the pressures and temperatures inside the inflator and the tank as a function of time. The predicted results were in good agreement with the experimental results. This model can predict transient pressures and temperatures with an accuracy of ±15%. The present modeling approach can be applied to a range of combustible gas mixtures, including hydrocarbon-oxygen, hydrogen-air and others.

A Multi-Mission Launcher System for Next Generation Surface Combatants

ABSTRACT A multi-mission launcher system called the Modular Horizontal Launcher System (MHLS) is presented. This conceptual design fulfills the requirements of next generation surface combatants and places emphasis on reduced manning, maintenance, and life cycle cost. The cornerstone of MHLS is a common, scaleable, and adaptable modular architecture simplifying the ship integration process and introduction of new munitions. MHLS features commercial off-the-shelf/non-developmental item (COTS/NDI) technologies that reduce development cost and accelerate system introduction. MHLS components include all-up-round (AUR) launch canisters that serve as both shipping containers and launch tubes, and a robust distributed electronic architecture that allows simultaneous communication with all applicable weapon control systems. Separate canister configurations for cold launch of munitions, using COTS automotive airbag inflators as impulse mechanisms, and hot launch of munitions are envisioned. MHLS is currently in a proof-of-concept phase of system development that brought about a torpedo launch capability demonstration. Concept explorations, airbag inflator launcher models, and successful proof-of-concept testing render the MHLS a highly viable and cost effective alternative for next generation surface ship launcher implementation.

Flame Propagation Processes in a Simulated Combustor for Heated-Gas Airbag Inflators

An experimental investigationwas conducted to study the  amepropagationprocesses of premixedhydrogen/air  ames in a test rig simulating conditions in heated-gas in ators for the advancement of the hybrid airbag device. Themajorobjectivewas to observe the couplingphenomenaof the igniter discharge and  amepropagationprocess under different test conditions.Using high-speed cinematography, the  ame-front propagationspeed was found to be governed by the trajectory of the ejected igniter disk. Initial concentration of hydrogenhas a dominanteffect on the pressure–time history in the combustor. It was found that, for marginally lean mixtures, the occurrence of the nonreproducible feature of the second pressure hump, during the chamber depressurization process, was caused by the strong coupling between the igniter disk trajectory and the wake- ow induced reactions of entrained gases.

Otologic injuries caused by airbag deployment

Airbags are clearly successful at mitigating injury severity during motor vehicle accidents. Deployment unfortunately has introduced new injury-causing mechanisms. A retrospective review of 20 patients who sustained otologic injuries resulting from airbag inflation was conducted. The most common symptoms were hearing loss in 17 (85%) and tinnitus in 17 (85%). Objective hearing loss was documented in 21 of 24 (88%) subjectively affected ears; this included unilateral and bilateral sensorineural, unilateral conductive, and mixed hearing losses. Ten patients (50%) had dysequilibrium. Four subjects (20%) had a tympanic membrane perforation; each required surgical closure. Ear orientation toward the airbag was found to be associated with hearing loss ( P = 0.027), aural fullness ( P = 0.039), and tympanic membrane perforation ( P = 0.0004). A wide variety of airbag-induced otologic injuries occur and may have long-term sequelae. It is important for health care personnel to be aware of these potential problems. (Otolaryngol Head Neck Surg 1999;121:367-73.)

Air bag-related ocular injuries: an overview

Abstract Air bags have become a valuable commodity in automobile safety. They are responsible for saving thousands of lives every year. With the increased use of air bags, there have been more ocular injuries related to air bag inflation. The purpose of this summary is to provide primary eye care practitioners with a review of these reported ocular injuries and their appropriate management. This review also stresses the importance that patients who present with air bag trauma undergo a complete eye examination.

Dynamic response of the Hybrid III three year old dummy head and neck during side air bag loading

This paper presents the results from 14 tests designed to evaluate the response and injury potential of a Hybrid III three year old dummy subject to loading by a deploying seat mounted side air bag. An instrumented Hybrid III three year old dummy was used for tests in two different occupant positions chosen to maximize head and neck loading. Four seat mounted thoracic side air bags were used that varied only in the level of inflator output. The National Highway Traffic Safety Administration's neck injury criteria for complex loading were modified to include moment values for both anterioposterior and lateral directions. The results indicate that side air bags may be designed so that the forces and moments in the child dummy's neck are below injury threshold values during a side air bag deployment. While there is considerable uncertainty as to the validity of published injury criteria owing to the lack of child biomechanical data, this study demonstrates the sensitivity of child response to initial position which provides insight into placement and geometry of side airbag systems. Furthermore, the data indicate a relationship between airbag inflator properties and child dummy response for a given airbag geometry.

Noise trauma from air bags.

Air bags have contributed substantially to the safety of car occupants in road accidents, but concern exists that they may inflate unnecessarily in low speed crashes. Previous articles have reported eye, face, upper limb, and chest injuries caused by air bag inflation. In this report, researchers describe two cases of hearing loss and persistent tinnitus that may have resulted from air bag inflation in low speed collisions. Neither subject sustained other injuries.

Two case reports of possible noise trauma after inflation of air bags in low speed car crashes

Air bags have contributed substantially to the safety of car occupants in road accidents, but concern exists that they may inflate unnecessarily in low speed crashes.1 Previous articles have reported...

Automobile airbag impulse noise: Otologic symptons in six patients

Automobile airbag safety systems have successfully reduced the number of occupant injuries from motor vehicle accidents. Unfortunately, airbags are also associated with some inherent risk, including a high-amplitude, short-duration noise from airbag deployment. A review of the available research in the automobile industry indicates that the peak amplitude of this noise may exceed 170 dB sound-pressure level. Despite the increasingly wide application of airbags in automobiles, there have been no previous reports of airbag-related otologic injuries. The authors have encountered six patients with otologic symptoms that appear to be related to airbag impulse noise. Five of these patients have documented hearing loss, one patient reported persistent tinnitus, and two patients have significant dysequilibrium. Although permanent hearing loss from airbag noise appears to be rare, temporary threshold shifts are probably much more common. It is important, therefore, that the clinician be aware of the noise associated with airbag inflation and the possibility of acoustic trauma from these safety devices.

Human auditory response to an air bag inflation noise: Has it been 30 years?

Once upon a time, over 30 years ago, 100 subjects volunteered for exposure to high level impulsive noises generated by the inflation of prototype automobile safety air bags. The government mandated that passive restraint systems, beyond seat belts, be introduced in passenger automobiles within 2 years. The only reasonable candidate was the air bag system, however, none were fully developed for automobile production. One concern was the effect of inflation noise on the auditory systems of vehicle occupants. Ninety-one volunteers qualified for the study; nine were rejected by an otolaryngologist because of head colds, congestion, and upper respiratory infections. Subjects facing forward in the rear seat of a small automobile experienced the noise of simultaneous inflation of a 9-cf passenger air bag and a 2.5-cf driver air bag. The median peak pressure level of the impulsive noises was 168 dB obtained with an overall measurement system ranging from 30 Hz (microphone low frequency cutoff) to 40 000 Hz. The dynamic range was 180 dB. Post-exposure auditory system evaluations included external auditory canals, eardrum membranes, verbal communications-auditory perception, aural discomfort, TTS, and PTS. Results are discussed in terms of the conditions of the exposures, the measurements, and the study population. [Work supported by DOT, National Highway Safety Bureau.]