Airbag Inflation Research Articles

Restraint System Optimizations Using Diverse Human Body Models in Frontal Crashes

<div><b>Objective:</b> This study aimed to optimize restraint systems and improve safety equity by using parametric human body models (HBMs) and vehicle models accounting for variations in occupant size and shape as well as vehicle type.</div> <div><b>Methodology:</b> A diverse set of finite element (FE) HBMs were developed by morphing the GHBMC midsize male simplified model into statistically predicted skeleton and body shape geometries with varied age, stature, and body mass index (BMI). A parametric vehicle model was equipped with driver, front passenger, knee, and curtain airbags along with seat belts with pretensioner(s) and load limiter and has been validated against US-NCAP results from four vehicles (Corolla, Accord, RAV4, F150). Ten student groups were formed for this study, and each group picked a vehicle model, occupant side (driver vs. passenger), and an occupant model among the 60 HBMs. About 200 frontal crash simulations were performed with 10 combinations of vehicles (n = 4) and occupants (m = 8). The airbag inflation, airbag vent size, seatbelt load limiter, and steering column collapse force were varied to reach better occupant protection. The joint injury probability (Pjoint) combining head, neck, chest, and lower extremity injury risks was used for the design optimization. Injury risk curves were scaled based on the skeleton size and shape of each HBM.</div> <div><b>Results and Conclusions:</b> We observed that tall and heavier male occupants tend to strike through the airbag leading to higher head injury risk; older and female occupants tend to sustain higher chest injury risk, while obese occupants tend to have higher lower extremity injury risk. After design optimizations, the average <i>P</i>joint was reduced from 0.576 ± 0.218 to 0.343 ± 0.044. The airbag inflation and venting were found to be highly effective in head protection, while the belt load limit and steering column force were sensitive to chest injury risks. Conflicting parameter effects were found between head and chest injuries and among different occupants, highlighting the complexity of achieving safety equity across a diverse population. This study demonstrated the benefit of adaptive restraint systems for a diverse population.</div>

Study on Simulation Method to Determine the Inflation Threshold of Head Protective Airbag for High-speed Helicopter Pilot

Compared with ordinary helicopters, the flying speed of high-speed helicopters is increased from 350km / h to 450km / h, and the crash speed is bound to exceed 12.8m / s, which greatly increases the probability of collision injury of the pilots’ head. The equipment, such as the traditional safety belts and crashworthy seats, cannot play an effective role in protection. In order to effectively improve the crashworthy survival rate of high-speed helicopter pilots, the main method in European and American countries is to design additional head protective airbags. The paper carried out the study on the simulation method for determining the high-speed helicopter head protection airbag inflation threshold value. Based on LS-DYNA, it has established the impact simulation model of the high-speed helicopter cockpit – seat – safety belt – pilot system. At the same time, the HIC value of the dummy head (no more than 1000N) and the pull force of the shoulder strap (no more than 8890N) are taken as the objective function to simulate the collision process of the man/seat system in multiple states of the high-speed helicopter. Finally, the inflation threshold of the head protective airbag is determined, which provides a critical support for the development of the head protective airbag.

Simulative Quantification of the Supersonic Discharge Process of Cold Gas Airbag Inflators

Abstract A simulative method for quantifying the discharge process of cold gas airbag inflators is presented. The pressure, mass flow and the influences of the flow field are relevant to a robust and predictive airbag deployment. Simulations in this regard are compared and validated with experimental data. It turns out that simulated mean pressures inside the inflator deviate by 5–10% from measured data. A complex and highly turbulent flow field with supersonic and subsonic flow emerges. An influential longitudinal vortex forms in the cold gas inflator, leading to a highly dynamic discharge process. This vortex would not be found with the current state-of-the-art methods, such as the simple tank test or analytical models. It is shown that a simple turbulence model such as the k−ω shear stress transport predicts the flow field with sufficient accuracy in comparison with the large eddy simulation. Real gas effects must be taken into account inside the high-pressure reservoir, leading to a faster discharge compared to the ideal gas, due to faster moving expansion waves in the reservoir. Real gas effects outside the high-pressure reservoir seem to be negligible. A simplified simulation model was developed that uses only part of the whole cold gas inflator model and serves as a good practical approach for airbag deployment simulations, with less computational effort. Thus, the method presented here can provide high-quality inflow data for airbag deployment simulations.

Free Fall Detection in UAV Missions

This research paper addresses the designing of high speed free fall detection and primary trigger generation problem as a part of an in-flight emergency technology developments for unmanned aerial vehicles. The primary trigger is the very first to be detected and to be generated with high speed and accuracy in designing protection mechanism. This trigger indicates that UAV started falling. Sequences of resulting mechanism such as airbag inflation comes secondly. Speed requirement is a deterministic factor when the flight altitude is low. In this paper a high speed analog module is proposed to achieve the primary trigger and performed relevant validation tests on linear free fall and rotational free fall which covers the majority of free fall patterns. The positive test results verify the design as a primary trigger generation module for linear and rotational free fall detection in low altitude UAV missions or which could be enhanced with additional features to form more complex system of airbag inflation in UAV in-flight emergency technology development.

Research on numerical simulation of submunition dispenser under different dispersion state

In order to study the process of submunition airbag dispersal under different dispersion state, the p-t curve of gas generator combustion obtained by closed bomb test was transformed into the mass flow rate-time curve to simulate the process of airbag inflation. As the initial condition, it was input into the finite element model of submunition dispersal established by LS-DYNA software, and the results were compared with the literature data to verify the accuracy of the calculation method. Then, through the numerical simulation of airbag dispersion of submunition with different centroid positions and initial placement angles, the simulation results show that the dispersal velocity of the submunition decreases with the increase of the offset of the centroid in the x direction and the placement angle. The peak overload decreases with the increase of centroid offset and placement angle. The angular velocity of the submunition rotating around the y axis increases with the increase of the offset of the centroid in the x direction; the velocity of submunition rotating around x axis increases with the increase of the offset of centroid in y direction.

Design and Performance Research of a Wearable Airbag for the Human Body

In this paper, an integrated wearable airbag is proposed to protect the vulnerable pedestrian during a vehicle–pedestrian collision accident. To evaluate the protection performance of this newly proposed integrated wearable airbag, the airbag inflator finite element model is first verified via an inflator tank test, and the simulated results agree very well with the test. Next, the finite element model of the vehicle–pedestrian model is established, including a simplified vehicle model and a biomechanical HBM with the integrated wearable airbag. The numerical results show the newly proposed wearable airbag can effectively protect the pedestrian by significantly reducing injuries to the head and chest. Since head injury is the most important injury type, a complete set of injury indexes is adopted to evaluate severity of head injury, including HIC15, 3 ms resultant acceleration, and intracranial pressure. To further improve the protection performance of the airbag on the HBM’s head, a parametric study is conducted towards two design parameters of the wearable airbag: inflator gas mass and pulling strap length. The parametric investigation shows 26 g gas and a 20 mm pulling strap can provide the best protection for the HBM’s head.

A method to quantify the supersonic discharge of airbag cold gas inflators

We discuss a method to quantify the supersonic discharge of airbag cold gas inflators. Since one primary quantity of interest, the mass flow with time, is not directly measurable, a combined experimental and numerical approach was chosen. Shadowgraph and schlieren images visualize the gas dynamic process. Pressure measurements were conducted inside the inflator and downstream of the outlets in the supersonic jet. In this context, a method to measure the pressure of the flow without effects of shock reflection is presented. The temperature inside the inflator was estimated using a fast response heat flux probe and assuming different scenarios for the unknown heat transfer coefficient. Then, a numerical model of the inflator was created. The experimental results served as boundary conditions and some basic sensitivities remaining unknown from the measurements were studied to verify the numerical outcome. The numerical model was verified using experimental results. Finally, the mass flow rate was derived from the numerical model and compared to an analytical model. The method can reconstruct the temporal evolution of the mass flow discharging from the inflator, the pressure and the topology of the flow field within acceptable bounds. Furthermore, the method can deliver inflow data for subsequent airbag inflation studies.Graphical abstract

A wearable soft robot that can alleviate the pain and fear of the wearer

Social soft robotics may provide a new solution for alleviating human pain and fear. Here, we introduce a hand-held soft robot that can be clenched by the wearer. The robot comprises small airbags that can be inflated to provide the wearer with a feeling of being clenched. We then conducted an in-depth study of 66 adults who participated in a pain research protocol using thermal stimulation to investigate the effect of wearing the robot on pain perception and fear of injections. Pain assessment scale scores for perceived pain decreased significantly (p < 0.05) when participants wore the robot compared with the baseline condition in which the robot was not worn. In addition, the saliva test results showed a downward trend in oxytocin level when the robot provided the wearer with haptic feedback via the inflation of the internal airbags in response to the wearer’s clench. Furthermore, the negative psychological state of participants, as measured using the positive and negative affect scale, improved significantly when wearing the robot. We also revealed that the salivary cortisol level, an indicator of stress, decreased significantly across all participants at the end of the experiment. In addition, participants’ fear of injections was significantly improved after participation in the experiment. These results suggest that the wearable soft robot may alleviate the human perception of pain and fear in during medical treatments, such as vaccinations.

Numerical simulation-based loaded inflation height modeling of nursing bed airbag.

In previous studies, the numerical simulation models of industrial airbags were verified to have high accuracy regarding their actual dynamics. However, numerical methods were scarcely utilized to simulate and investigate the inflation height behaviors of nursing bed airbag. For this problem, this study constructs a numerical simulation model illustrating the association between the internal pressure and inflating height of nursing bed airbag, under various external loads. Firstly, based on an averaged pressure prerequisite, an airbag dynamic model is established by the control volume approach (the air inside the airbag follows the gas state equation of Poisson's law). Besides, the elastic mechanical behaviors of airbag film material are determined according to a material constitutive model built by the quasi-static uniaxial tensile test. The obtained data are used as the boundary conditions, for the numerical dynamics modeling of the nursing bed airbag. Verification experiments clarify that this numerical modeling is accurate for describing airbag inflation behaviors, and then can be effectively applied to the design and optimization phases of nursing bed airbags. Based on the simulation modeling above, the mathematical equation of controlling airbag inflating height by its internal pressure is obtained. It provides a vital basis for the differentiated and intelligent control of the airbag nursing bed.

Photoflash and laser ignition of Al/PVDF films and additively manufactured igniters for solid propellant

Solid propellants are employed in a range of applications from the inflation of airbags to propulsion systems for rockets. The ignition of solid propellants must be carefully controlled and modified on a per-use basis due the specific ignition requirements of each application. Using tailored photoreactive materials as a source of ignition for solid propellants, or other energetic materials, could reduce the added weight and risk of traditional initiators and result in safer, more effective solid rocket motor ignition systems. This study demonstrates the tunability of the ignition delay and propagation properties of optically-sensitive, nearly full density reactive aluminum/polyvinylidene fluoride (Al/PVDF) films and additively manufactured igniters. A single printed layer of pure nano-aluminum (nAl) at ideal stoichiometry in PVDF was found to flash ignite, but frequently yielded delayed transitions in steady propagation from the igniter to the propellant. To improve the continuity and steadiness of the transition, fuel particle size, igniter thickness, and a combination of layers of nAl and micron-sized aluminum (μAl) were investigated. In printed igniters with layers of μAl, only a single layer of nAl was needed to flash ignite the material and propagate to the layers of μAl without delay. For igniters cast onto strands of ammonium perchlorate composite propellant, continuous ignition was achieved with a single layer of nAl printed atop a triple layer of μAl for the flash-activated igniters and a single layer of nAl printed atop a single and triple layer of μAl for laser-driven igniters. The nAl/PVDF layer enabled good flash or laser ignition sensitivity, while the μAl/PVDF produced more sustained heat transfer to produce a reliable ignition process.

Experimental optimization of the ejector design developed for a driver’s airbag

Design modifications are tested experimentally of the compact supersonic ejector developed for the novel airbag inflation system. The base design resulting from combined numerical and experimental investigations showed itself potentially capable of inflating the 50 L airbag with three parts of entrained air volume together with one part produced by a gas generator. The base design work continues to study its technological flexibility and operational reliability by analyzing a complex flow structure within the inflator. For that, minor changes and supplements to the design were evaluated experimentally to avoid complicated numerical simulations. In particular, it was supposed that a vortex formed at the inflator inlet could significantly reduce its operational cross-section. The impact of this vortex on the airbag filling was investigated in the Laboratory for Advanced Aerodynamics using the developed pneumatic facility. The applied design improvement was found to affect the pressure distribution favorably in the inflator that increased the airbag filling by ~5%.

Analyzing Security Risks in Cyber-Physical Manufacturing Systems with Actor–Network Theory

Abstract This article suggests that actor–network theory (ANT) can reveal unique challenges and consequences of cyberattacks in manufacturing. As an approach, ANT rejects the dualism that often separates humans and nonhumans, recognizing the active role of both in affecting events. Our approach adds an important new perspective to an existing body of research that focuses on analyzing vulnerabilities in cyberspace instead of their ramifications in the material world. Drawing on the case study of a faulty airbag inflator in an automobile, we use concepts and vocabularies drawn from ANT to discuss the consequences of attacks in manufacturing, such as viewing altered products as actants with agency to alter subsequent networks (e.g., when a manufactured part is integrated into an automotive vehicle). By tracing the movement of specific materials and products through networks it is possible to elucidate how cyberattacks not only impact cyber-physical systems themselves, but also reverberate into a multitude of broader impacts, potentially endangering physical safety, shaping public opinion, and influencing economic markets. Our examination of one particular context draws on existing work that has brought ANT and cybersecurity in dialogue, but we extend this work by focusing on the role of “translation” and “depunctualization” across the lifecycle of a cyberattack in manufacturing. This analysis stresses the need for sector-specific examinations of cyberthreats, while also demonstrating the value of interdisciplinary methods like ANT that do not reify artificial dualisms in addressing for conceptualizing security risks in cyber-physical manufacturing systems.

Preliminary Study of an Adjustable, Wearable, Noninvasive Vest Providing Chest Compression to Assist with Breathing.

Respiratory muscle paralysis caused by acute cervical spinal cord injury usually leads to pulmonary ventilation dysfunction and even death from respiratory failure. In addition to invasive treatments such as mechanical ventilation, the utilization of noninvasive respiratory support equipment plays an important role in long-term assisted breathing. In this study, we describes a wearable, noninvasive vest with adjustable pressure that enables assisted breathing and with an automatic alarm, and we aims to explore its safety and effectiveness on healthy adult participants. The vest monitors the human heart rate and the blood oxygen index data in real time, the alarm is automatically activated when the data is abnormal. Eight healthy participants had no obvious discomfort during the test while wearing the vest. Lung volumes, antero-posterior diameters, and left-right diameters at the second, fourth, and sixth ribs levels were acquired before and after inflation of the vest airbag, the data acquired by the imaging analysis using chest computed tomography showed significant differences before and after the inflation (p < 0.05). Thus, The vest designed for this study can achieve uniform and effective compression of the thorax, significantly changed the size of the thorax and lungs. It is expected to be applied as noninvasive support for patients with respiratory dysfunction.

Design of the Airbag Inflation System Applicable to Conventional and Autonomous Vehicles

The emergency transformation of various aspects of life and business these days requires prompt evaluation of autonomous vehicles. One of the primary reassessments deals with the applicability of the vehicle passive safety system to the protection of arbitrarily positioned passengers. To mitigate possible risks caused by the simultaneous deployment of several big airbags, a new principle of their operation is required. Herein, the aspirated inflator for a driver airbag is developed that can provide 50L-airbag inflation within 30–40 ms. As a result, about 3/4 of the air is to be entrained into an airbag from the vehicle compartment. The process is initiated by a supersonic pulse jet (1/3 air volume) generated pyrotechnically. Then the Prandtl–Meyer problem formulation enables guiding linear and angular dimensions of the essential parts of the device. Accordingly, a family of experimental models of varied geometry is fabricated and tested to determine their operational effectiveness in a range of motive pressure within ~ 3–7 MPa. Experiments are performed on a specially designed facility equipped with compressed-air tanks and a high-speed valve to mimic the inflator operation with the pyrotechnic gas generator. The aspirated inflator operability is characterized using multivariate measurements of pressure fields, high-speed video-recording of the airbag inflation process, and evaluation of aspiration (entrainment) ratio. The average volume aspiration ratio measured at 300 K is found to reach 2.8 and it’s expected to almost double at 1200 K.

Distributed Fiber Optic Strain Sensing for Geomechanical Monitoring: Insights from Field Measurements of Ground Surface Deformation

In recent years, distributed fiber optic strain sensing (DFOSS) technology has demonstrated a solution for continuous deformation monitoring from subsurface to surface along the wellbore. In this study, we installed a single-mode optical fiber cable in a shallow trench to establish an effective technique for ground surface deformation mapping. We conducted three experimental field tests (iron plate load, water tank filling up load, and airbag inflation) in order to confirm the strain sensitivity of DFOSS for static loads, dynamic overload, excavation, subsidence, and uplift. This paper also presents two installation methods to couple the fiber cable with the ground under various environmental conditions; here, the fiber cable was installed in a shallow trench with one part buried in the soil and another part covered with cement. Our results suggest that covering the cable with cement is a practical approach for installing a fiber cable for ground surface deformation monitoring. By combining this approach with wellbore DFOSS, accurate surface–subsurface deformation measurements can be obtained for three-dimensional geomechanical monitoring of CO2 storage and oil and gas fields in the future.

Numerical Investigation of Pyrotechnical Initiators and Their Impact in Airbag Inflator Applications: Ballistic Modeling and Functional Analysis

A numerical model describing the ballistic behavior of a commercially used initiator is presented in this article. This model was built on the principle of conservation of mass and energy in the multi-phase framework incorporated with multi-loaded conditions. After obtaining the information about the grain size distribution in each composite, a fixing factor was proposed based on the surface area ratio of the composites. Thus, the solid propellant burning process based on distributed grain size was described, and the burn rate parameters of the applied pyrotechnic compositions were re-evaluated for different preconditioned temperature levels according to Vieille’s law. The influence of bridge wire and initiator metal cap was further modeled concerning their characteristic properties according to the observed measurements. The validation of the entire initiator model in the closed bomb test showed quantitative agreement with the measured pressure evolution, while the parameter study for evaluating the ballistic sensitivity of each component delivered some insights into the product development process. Furthermore, the configuration of a cold gas inflator was utilized to evaluate the initiator impact for a realistic application, where the shock wave intensity during deployment serves the main function in the inflator design. Incorporated with CFD simulations to capture the shock wave propagation, 0D-3D coupling strategy for initiator ballistics to inflator configuration was realized. Besides, the simulation results reflected the physical conditions in a proper manner. In particular, the parameter study led to a better understanding of interactions between inflator components, which were barely possible to be quantified through the measurements. The proposed initiator model could also be used in combination with other mechanical principles as a component of pyrotechnic devices such as pin-puller, electric line cutters, or airbag inflators. The detailed information gained in describing the physical properties enabled us to assess the existing design quantitatively and to have better control of the product quality.

Supersonic ejectors for novel airbag inflation systems

2. pressure and temperature control within a vehicle since most of the gas enters the airbag from the passenger compartment

Sodium Azotetrazolate: A Novel Environmental-friendly Hydrogen-free Gas-Generating Pyrotechnics

Gas-generating pyrotechnics are widely used in airbag inflator, pre-tensioner seat belt, deep-water salvage, fire extinguishing bomb, etc. However, for maintaining prolonged high-pressure, specific gas-generating pyrotechnics are required that are capable of producing water-vapor-free gaseous products to avoid the decrease of pressure caused by the condensation of water vapor. Currently, only sodium azide (NaN3)-based gas-generating pyrotechnics can meet the demand, but its application is limited due to its toxic effects. In this work, a sodium-azotetrazolate-based (STZ-based) eco-friendly and hydrogen-free gas-generating pyrotechnics was presented. A typical STZ-based gas-generating pyrotechnics was NaNO3/STZ gas-generating pyrotechnics, which could generate 321.04 L/kg clean and non-toxic gas composed of N2 and CO2 without any water vapor. The burning characteristics, including the ignition delay, maximum pressure and burning time of NaNO3/STZ gas-generating pyrotechnics was determined by conducting a closed vessel test. NaNO3/STZ gas-generating pyrotechnics showed a stable combustion process, lower ignition delay, higher burning rate, and the maximum pressure produced is 1.7 times of that of NaN3/Fe2O3. Thus, STZ exhibited great potential as gas-generating pyrotechnics, which could be applied, especially where a stable pressure is required for a long time.

Development of a compact pulsed ejector: performance assessment from measured aerodynamic characteristics

The investigation aims at the development of an efficient ejector applicable to the inflation system of automobile airbags. The work consists in the design of the ejector together with an appropriate testing facility and a measurement complex. The experiment is planned in three parts, measurement of pressure fields, high-speed video recording of the airbag inflation using the designed ejector, and measurement of the entrainment (aspiration) ratio. For that, a few basic elements are built. They are the pneumatic facility with a specially designed high-speed valve as its key element, the data acquisition, and processing system controlled remotely to analyze pressure probe rake signals, and the stand to measure entrainment ratio values depending on the ejector geometry and motive pressure values.To satisfy the given engineering requirements, supersonic pulse aspirators are developed in various design versions, manufactured, and tested in the Laboratory for Advanced Aerodynamics. Analysis of a number of experimentally obtained results showed their good mutual concordance and a possibility to get the “cold-gas” aspiration ratio, A=3.16 – 1.57, depending on the motive pressure. The new device has obvious advantages compared to the conventional pyrotechnic type: (1) provides their safe operation with big airbags of the autonomous car, (2) eliminates injuries to occupants since aspirated airbags stop inflating on contact with any object within a vehicle.

Evaluation on substitution of conventional azide based fuel materials with an alternate one in an airbag system – A review

In an automobile vehicle, azide based conventional fuels are used for airbag inflation. The exposure of sodium azide leads to several health issues such as hypotension, indigestion, breathing difficulties, eyes burning, itching, drowsiness etc. This made the focus shifted towards finding out a non azide fuel suitable for an airbag inflation. This paper discusses about the selection and procedural implementation of a suitable non azide fuel for an airbag gas generants by forming a ranking matrix. Ranking matrix were formed based on the economic and hazardous parameters such as toxicity, instability and inflammability factors. The detailed literature survey on the different non-azide fuels available and performance evaluation techniques showed that Differential scanning calorimetry (DSC), Thermogravimetry (TG), Accelerating Rate Calorimetry (ARC) were used for evaluating the thermal parameters such as peak pressure, heat of formation, burning rate, pressure rate and decomposition temperature. The review was found useful to select various modelling and numerical techniques proposed by researchers for calculating the kinetic parameters such as activation energy, pre-exponential factor and reaction rate. These performance parameters of the conventional azide fuels can be kept as a bench mark while evaluating the non azide fuel. This review aids the researchers to choose a non azide fuel based on ranking matrix and to carry out performance analysis for a possible substitution of conventional azide based airbag fuels.