Volume 6, Issue 11, November – 2021 International Journal of Innovative Science and Research Technology

ISSN No:-2456-2165

Modeling and Numerical Investigation on Frontal

Airbag by Ls-Dyna : For Identify the Head Injury
Matcha Ravikumar (Author) Menda Rajesh (Guide 1)
M.tech Student, Mechanical engineering (Machine design), Head of the Department, Mechanical engineering
Sarada institute of science, technology and management, Sarada institute of science, technology and management,
Srikakulam, Andhra padesh, India Srikakulam, Andhrapadesh , India

Girijala Sirishkumar (Guide 2)

Assistant Professor , Mechanical engineering
Sarada institute of science, technology and management,
Srikakulam, Andhrapadesh , India

Abstract:- From the past few years there are many velocity). Unless an external force acts on an object, it will
accidents happening passengers are getting injured even continue to move at its current speed and in the same direction.
after the deployment of the airbag. This is mainly due to the Cars are made up of a variety of components, including the
out of position of passenger and not wearing seat belt. The vehicle itself, loose objects in the vehicle, and, of course,
Head Injury Criterion (HIC) is used to assess passenger people. If these things are not secured, they will continue to
safety during a collision. The Head Damage Criterion (HIC) move at the same pace as the car, even if the car comes to a halt
model was created to quantify the risk of head injury in due to a collision. To bring an object's momentum to a halt, a
accident conditions. Using a computer algebra system (here force must be applied over a period of time. Because the
LS-DYNA) capable of analysing results from a real-world automobile's momentum has changed instantaneously and the
car collision test. occupants have little time to react, the force required to stop an
object is extremely high when a car crashes. Any supplemental
In this project, Airbag simulation along with human restraint system's purpose is to enable the passenger stop while
head foam is carried out. Nylon material is used for Airbag causing as little damage as possible.
and material properties are given to the airbag. Human
head foam which is downloaded from LSTC website is used. The following are the main components of an airbag:
The human head foam is aligned in the direction of airbag
deployment and made to strike airbag at an initial velocity An air bag is made up of three pieces that work together to
of 35mph at different positions of the airbag. achieve this goal:
1. Bag
The primary goal of this research is to evaluate the 2. Sensor
performance of airbag deployment using finite element 3. System of inflation
methods (FEM) to manage various collision scenarios while
lowering the HIC value. 1)Bag
The bag is constructed of a lightweight nylon cloth that is
Keywords:- FEM, Airbag, HIC, Crash analysis, LS-DYNA. folded into the steering wheel, dashboard, or, more recently, the
seat or door. By the way, the powdered item ejected from their
I. INTRODUCTION sir bag is normal cornstarch or talcum powder, which is utilised
by air bag makers to keep the bags malleable and lubricated
For years, our cars' only form of passive restraint was the during storage.
reliable seat belt. There was discussion concerning their safety,
particularly in relation to minors. However, over time, the 2)Sensor
majority of the country embraced seat-belt requirements. The sensor is what tells the bag when it's time to inflate.
According to statistics, seat belts have saved thousands of lives It collaborates with the control module to identify crash and
that might otherwise have been lost in collisions. Air bags have non-crash events. The severity of the hit is measured by these
been in the works for a long time. The appeal of a soft pillow to sensors. When a collision force equal to running into a brick
land against in the event of a disaster must be strong, as the first wall at 16 to 24 kilometres per hour occurs, inflation occurs.
patent for an inflatable crash-landing device for aeroplanes was They're set up so that if there's a sudden negative acceleration,
filed during WWII. The first commercial air bags emerged in the contacts will close, alerting the control module that there's
autos in the 1980s. been a crash.

Let's go over the laws of motion again before we get into 3)Inflation system
the details. First, we know that moving objects have momentum The air bag's inflating system produces a huge volume
(which is defined as the product of an object's mass and of nitrogen gas by reacting sodium azide (NaN3) with potassium

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Volume 6, Issue 11, November – 2021 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
nitrate (KNO3). Hot nitrogen blasts inflate the air bag from its D. Deployment of Airbag:
storage location at speeds of up to 322 kilometres per hour. The The accident itself is the first stage of airbag
gas swiftly drains via a tiny hole in the bag a split second later, deployment. A variety of sensors in the car, including
deflating the bag and allowing you to move. accelerometers, impact sensors, side pressure sensors, brake
pressure sensors, and seat occupancy sensors, are activated when
A. Chemistry of Airbag: a collision occurs, whether it is frontal or lateral. The rear safety
A gas generator containing a mixture of NaN3, KNO3, sensor must close before the forward sensors to prevent airbag
and SiO2 is located inside the airbag. A series of three deployment in situations where the impact is not strong enough
chemical reactions inside the gas generator produce gas (N2) to warrant deployment. Crash sensors, also known as airbag
to fill the airbag and convert highly hazardous NaN3 to impact sensors, are important safety components for your car.
innocuous glass in the event of a head-on collision. At 300°C, The unit determines whether and how the airbags should be
sodium azide (NaN3) decomposes into sodium metal (Na) deployed. The inflation step begins when the ACU detects that
and nitrogen gas (N2). The electrical impulse generated by the deployment threshold has been met. Because a compressed
the deceleration sensor ignites the gas-generator mixture, air system would have been impractical and inefficient, engineers
generating the high-temperature environment required for devised a system based on the solid rocket booster's operating
NaN3 decomposition. The resulting nitrogen gas principle. Each airbag has a pyrotechnic device called an initiator
subsequently fills the airbag. The sodium metal (which is or electric match, which is made out of an electrical conductor
highly reactive and potentially explosive) is removed by encased in combustible material. The conductor is heated by a
turning it to a safe substance using KNO3 and SiO2. To current pulse, which ignites the combustible material. The
begin, the sodium combines with potassium nitrate (KNO3) chemical reaction that fills the nylon fabric airbag with gas is
to form potassium oxide (K2O), sodium oxide (Na2O), and triggered by this igniter. The massive amount of gas then forces
more N2 gas. The N2 produced in the second reaction also the airbag out of the steering wheel and/or dashboard at speeds of
fills the airbag, and the metal oxides mix with silicon dioxide up to 200 mph or 322 mph, requiring around 0.04 seconds to
(SiO2) in a final reaction to make safe and stable silicate complete. When you consider that the blink of an eye takes about
glass. Because first-period metal oxides like Na2O and K2O 0.2 seconds, it's a rather quick procedure. The final stage of the
are very reactive, allowing them to be the end product of an airbag process is deflation, which happens virtually immediately
airbag detonation would be dangerous. after the inflated. Special vents allow the gas to escape.

TABLE I. CHEMICAL REACTIONS IN AN II. HEAD INJURY CRITERION

AIRBAG
Reaction Although significant progress in the understanding of head injury
1 2NaN3 2Na + 3N2 processes and the introduction of airbag restraint systems has
Reaction resulted in a reduction in the number and severity of head injuries,
2 10Na + 2KNO3 K2O + 5Na2O + N2 head injury remains a primary cause of death and disability. Despite
these developments, the Head Injury Criterion (HIC), which was
Reaction K2O + Na2O + SiO2 Na2K2SiO4 adopted over twenty-five years ago, remains the only injury criteria
3 (alkaline glass) in widespread use. NHTSA recommended HIC as a substitute for
the GSI in FMVSS No. 208, and it is calculated using the formula
B. Airbag raw materials: below:
1 𝑡2 2.5
Nylon 6, 6 yarns with deniers ranging from 420 to 840 are
the most commonly used raw materials for airbag fabric. HIC= max[ ∫ 𝑎(𝑡)𝑑𝑡 ] (t2 - t1)
𝑡2 −𝑡1 𝑡1
1880 D nylon-6.6 was utilised in the side impact airbags.
For all dummy sizes, the agency proposes evaluating the HIC over
C. Sensors used in Airbags: a maximum 15 millisecond time interval, with a requirement that it not
Crash sensors can be found at the front or back of the exceed 700 for the 50th percentile male and 5th percentile female. This
vehicle, as well as in the passenger compartment. One or more will allow for a more stringent review of long-duration events while
collision sensors may be installed in a vehicle. Only forces also increasing the rig our of short-duration events where
generated in large frontal or near-frontal impacts activate the biomechanical assurance is lacking. Based on a scaling from the
sensors; they are not engaged by quick braking or driving on proposed new limit for the 50th percentile adult male dummy, we
rough or uneven pavement. There are two types of functions. recommend changing the HIC time interval to a maximum of 15
Impact sensors and Safing sensors are two types of sensors. milliseconds for all dummy sizes and revising the HIC limits by
Forward sensors can be found in a variety of positions in the proportionate amounts.
passenger compartment. Depending on the manufacturer, rear
safety sensors are installed in various positions across the The AAMA's approach for scaling HIC15 based on tissue failure
passenger compartment. Some of them are linked to the Control stresses was reviewed by the agency, and it was judged to be roughly
and Diagnostic Module. To avoid airbag deployment in similar to both the scaled HIC15 values established by finite element
circumstances where the impact is not powerful enough to analysis and the scaling technique used in the NPRM, which employs
warrant deployment, the rear safing sensor must close before tendon strength. Furthermore, because the AAMA members agreed
the forward sensors. Airbag impact sensors, also known as crash to employ the scaling strategy based on tissue failure stresses, the
sensors, are critical safety elements for your vehicle. agency recommends to scale the HIC15 performance limits using this

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Volume 6, Issue 11, November – 2021 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
method. The AAMA, on the other hand, proposed performance Mesh type = Shell mesh
criteria of more than 700 for a six-year-old child and a girl in the fifth Elements type = Mixed elements
percentile. Given the uncertainties in the scaling approaches, the Head model mesh criteria:
agency feels it would be unwise to enable a child to have a higher Nodes = 25657
limit than an adult, and hence proposes that the six-year-performance Elements = 20027
old's limit be set at 700 for HIC15. Furthermore, because the Mesh type = Hexa mesh
biomechanical data used to produce HIC included both male and Element type = Hexa
female skulls of varied sizes, and because head size and body size are
not highly associated, the agency is suggesting a single HIC15 value Open the .K file of Airbag and Head model in Ls-dyna:
of 700 for all adult dummies. The HIC15 limit is mentioned for
completeness, even though the large male Hybrid III dummy is not
included in the proposed testing for the advanced air bag SNPRM.

III. METHODOLOGY

CATIA V5's associativity allows users to make design

modifications at any point during the product development
process, and downstream deliverables are automatically
updated. This capacity streamlines product development
processes by allowing concurrent engineering design, analytical,
and manufacturing engineers to work in simultaneously.
Fig.3. Airbag and Head model in Ls-prepost
A. Dimensions for the Airbag:
B. Boundary conditions for Airbag and Head model:
Outer diameter = 330mm
Inner diameter = 30mm
Material inputs:
Thickness = 0.38mm
Material used = Nylon 6.6 yarn
Segment length = 30mm
Density = 7.8×10-7kg/mm3
Poisson’s ratio = 0.3
Damping coefficient = 0.30

Shell inputs:
Shear factor = 1.0
Thickness = 0.38mm
Temperature = 800°C
Head model inputs:
Velocity = 35mph

Fig 1. Airbag model in CATIA V5 Software Mass flow rate inputs graph:

By importing the Airbag model and head model in

Hypermesh then it will appear in interface. Then have to mesh
the Airbag with shell mesh and Head model was already meshed
by biotechnology field persons by Hexa mesh.

Fig.4. Mass flow rate curve

Output requests:

Termination time = 30ms

Database>ASCII-option= Airbag statistics (DT 0.1)
Global statistics (DT 0.1)
Material energies (DT 0.1)
Fig 2. Meshed components BINARY_D3PLOT = DT 0.1
Airbag mesh criteria: C. Analytical calculations:
Nodes = 6834 The expression to calculate HIC value
Elements = 6920 HIC(d) = 0.75446 (Free motion of head form HIC) + 166.4

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 Volume 6, Issue 11, November – 2021 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
𝑚𝑎𝑥 1 𝑡 2.5
HIC = 𝑡 𝑡 {[𝑡 −𝑡 ∫𝑡 2 𝑎(𝑡)𝑑𝑡] (𝑡2 − 𝑡1 )}
1, 2 2 1 1

From the plot, the average value of acceleration for the time
interval of 𝑡1 = 12 ms and 𝑡2 = 27 ms is 51 mm/ms2 from the
graph.
𝑚𝑎𝑥 1 27 2.5
HIC = 𝑡 𝑡 {[ ∫ 51] (27 − 12)}
1, 2 27−12 12
𝑚𝑎𝑥
HIC = 𝑡 𝑡 {[0.0666 × 765]2.5 (27 − 12)}
1, 2 Fig.6. Air bag deployment at t = 17ms
HIC = 278.55

By using this HIC value, Calculate HIC(d) value

HIC(d) = 0.75446 (Free motion of head form HIC) + 166.4
HIC(d) = 0.754446 (278.55) + 166.4
HIC(d) = 376.55

The HIC36 value obtained from LS-PrePost for third case is

285.36 and HIC(d) value is 381.7.

The HIC36 value obtained from Analytical calculations

for third case is 278.55 and HIC(d) value is 376.55. There is Fig.7. Air bag deployment at t = 30ms
small variation in the HIC value obtained from LS-PrePost and
Analytical calculations which is acceptable. B. Output graphs:

IV. RESULTS

In this study, the use of LS-DYNA simulation to analyse

airbag deployment and HIC value was attempted. The airbag
has two sections and is generic. The inflator is attached to the
inner compartment, which has a hole in the middle of the rear.
The inner compartment and the outer compartment are
connected by this aperture. The air bag fully inflates in 26
milliseconds. The simulation takes 30 milliseconds in total.
Figures 5,6 and 7 demonstrate the findings of the multi-domain
technique for this deploying airbag at a certain period and at the
Fig.8. HIC value curve
end of the analysis.

The Head Injury Criterion (HIC) value of 381.7 was

produced using the LS- PREPOST programme, and LS-POST
was used to view the data after post processing. The output
values of velocity, pressure, internal energy, mass flow rate,
temperature, kinetic energy, internal energy, and total energy
are observed, as well as the velocity, pressure, internal energy,
mass flow rate, temperature, kinetic energy, internal energy, and
total energy values.

A. Airbag deployment: Fig.9. Velocity output curve

Fig.5. Air bag deployment at t = 9ms Fig.10. Pressure output curve

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Volume 6, Issue 11, November – 2021 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
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