MATEC Web of Conferences 184, 01007 (2018) https://doi.org/10.1051/matecconf/201818401007 Annual Session of Scientific Papers IMT ORADEA 2018
Study regarding the influence of airbag deployment time on the occupant injury level during a frontal vehicle collision
Alexandru Ionut Radu1,*, Corneliu Cofaru1, Bogdan Tolea2 and Dragoș Dima1
1Department of Automotive and Transport, Faculty of Mechanical Engineering, 500091 University “TRANSILVANIA” of Brasov, Romania 2Department of Mechanical Engineering and Automotive, 410610 University of Oradea, Romania
Abstract. The aim of this paper was to analyse the influence of airbag deployment delay upon the head of the occupant in the case of frontal collision using simulations in PC Crash and MADYMO dummy as the occupant. The study will also take into account the pretension delay of the seat-belt which is activated along with the airbag. Frontal airbags on both the passenger and the driver were analysed including the occupant kinematics during the collision. Also, to validate the simulation, a comparison was done with a real crash test. We predict that by increasing the delay of deployment, the head acceleration will increase due to the fact the head travels close to the instrument panel/steering wheel, and the force of the airbag will generate a significant acceleration upon the head. To better assess the potential injury of the occupant, the head injury criteria (HIC) will be calculated and correlated with the Abbreviated injury scale (AIS) code.
1 Introduction corn-starch) [7]. There are multiple types of airbags (front, sides, knee and curtains) [8]. The increasing number of vehicles during the last decades The head injury can be assessed by a parameter called in the urban area, as well as the intensification of HIC (Head Injury Criteria), defined by a mathematical congestions in intersections has led to considerable road- formula. The HIC criterion is a way of assessing the risk accident recordings [1]. Road traffic accident research has of a cranial trauma injury as a result of an accident. The been conducted over the years in order to study of the HIC criterion is the maximum standard value of the dynamic and kinematic behaviour of the occupant in the integral of the head acceleration. Depending on the impact phase as well as the injury assessment [2]. Since interval for which it is calculated, the HIC criterion is: the introductions of airbags, lots of lives have been saved - Unlimited - HIC; in motor vehicles crashes [3]. The airbag provides a good - 36 ms maximum - HIC36; protection for all kinds of crashes (side and frontal) that - 15 ms maximum - HIC15. could seriously injure or kill the occupants of the vehicle In order to predict the injury level of the occupant, the [4]. Huere has shown in a study that airbags can reduce HIC formula takes into account the head acceleration on head injuries by up to 82% for the 56-65 km / h range. the occupant’s head. The HIC formula is presented below Using the airbag, it was demonstrated that in 85% of [9], [10] cases, head injuries were classified as minor injuries [5]. Airbags have been demonstrated to reduce car t2 1 2.5 (1) HIC36 max[(t2 t1)( a(t)dt) accident mortality by 19%, and reduce morbidity from t1,t2 t t facial fractures and chest injuries. In purely frontal 2 2 t1 crashes, airbags reduce the fatality risk by 34% [6]. Where: t2 – final time value (s), t1 – initial time value (s), Airbags inflates when an electrical current provided a(t) – head acceleration resultant (g) by the airbag control unit is distributed to the detonator. The acceleration value, according to the impulse The ignition starts a chemical reaction that produces duration, shows a maximum limit of 40 g for the head. In nitrogen gas which rapidly inflates the nylon fabric bag. the case of pedestrians the situation is more dangerous, at After the airbag has been fully inflated, the nitrogen gas the impact with the ground, much higher head is released through small vent holes at the side when the accelerations (120 - 200 g) can cause severe injuries. The occupant’s head hits and compresses the airbag. The small head injury assessment is done using the HIC (Head holes are constructed specifically in a size and spaced out Injury Criteria) criteria in a time interval of 36 to reduce the volume of the airbag at a different rate, milliseconds for the occupant, respectively 15 ms for the depending on the type of vehicle. This gas is released pedestrian [11], [12]. alongside with dust particles that are from the material used to lubricate the airbag (typically talcum powder and
* Corresponding author: [email protected]
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). MATEC Web of Conferences 184, 01007 (2018) https://doi.org/10.1051/matecconf/201818401007 Annual Session of Scientific Papers IMT ORADEA 2018
The in ur probabilit chart shown in ig. . the main characteristics of the airbag are presented in Fig. represents the correlation of the I scale code with the 2. HIC alue as disco ered b lberto .
Fig. 2. Driver airbag technical specifications [16].
The inflation dimensions of the airbag are mm in length and mm in width. The total duration of inflation is ms during this time the massflow reaches Fig. 1. Injury potential according to HIC 36 value in correlation with the AIS scale code. . g s in the first ms then it drops to in the ne t ms. The mass of the airbag e pands from to g in The graph presents the e olution of the probabilit cur es ms. for I in ur based on HIC alue. od tolerance In ig. the technical specifications of the passenger according to the HIC criterion is and corresponds to airbag are presented in the similar wa as the dri er. It is a probabilit of of the I in ur . This to mention that on the passenger side the airbag is much increases to for HIC . The probabilit of larger. death for the occupant indicate an I and occurs at HIC abo e . ances researched the effects of airbag dela on the nec . He obser ed that the pea tension force and e tension moment in nec are well below the nec in ur critical intercept alues of and e tension moment of m proposed disco ered b HT . In contrast in the case of late airbag deplo ment the pea tension and e tension moment are well abo e the nec in ur tolerance. This suggests the high probabilit of serious Fig. 3. Passenger airbag technical specifications [16]. nec in ur with late deplo ment airbag. n anal sis b rieder and umar using accident The inflation dimensions of the passenger airbag are simulations with a irtual occupant model re ealed that mm in length mm in width and mm in height. HIC alues of the irtual dumm increased with the uring inflation the massflow goes from to . g s in increase in airbag deplo ment dela . It was obser ed a the first ms then it drops to almost in the ne t ms. percentage increase of the HIC alue b up to in The mass of the airbag e pands from to g in the e ent of an airbag deplo ment dela of ms. If the ms. It can be obser ed that the passenger airbag is time dela was ms the gas force inside the airbag throws larger that the dri er side. The technical characteristics of the occupant s head in the rear and it comes in contact with the airbags are fi ed and cannot be modified in the the head restraint causing in ur b increased acceleration program howe er there are some e parameters that can alues of the head . The stud at hand follows up this be ad usted such as the ignition time of the airbag and anal sis and test new ariants including passenger in ur seatbelt pretention. ris a seatbelt pretensioning s stem. sing this screen the ignition time could be set to a specific alue ma ing this stud possible. lso the airbag and seatbelt could be either set as acti e or one or 2 Occupant Model both set as inacti e. There are other settings can set be se The occupant is represented b a multibod dumm male such as the seatbelt configuration onl shoulder belt or th percent model integrated in C Crash lap belt and if the current crash simulation is a side used to simulate the inematics of the occupant . impact. namic simulation were conducted before in order to anal se the occupant beha iour using the 3 Methods Used model . using mathematical models of the human bod the mo ement of the bod elements can be The method in ol es running simulations in C Crash imprinted e tensi el . using the model where the ignition time of the Using this model, airbag deployment and kinematics airbag is modified in order to anal se the dela time and can be analysed for both the driver and the passenger the occupant inematics. lso to alidate the simulation along with the seatbelt pretension system. For the driver, a frontal crash test will be conducted where the airbag and seatbelt are used. The crash test in ol es a stationar
2 MATEC Web of Conferences 184, 01007 (2018) https://doi.org/10.1051/matecconf/201818401007 Annual Session of Scientific Papers IMT ORADEA 2018