Inflator Performance Optimization with New PAB Concept for OMDB, LRD RAEICK, JANG HYUNDAI MOBIS KOREA YOOHOON CHOI HYUNDAI MOBIS KOREA DOOWON YANG HYUNDAI MOBIS KOREA Paper Number 17-2013 ABSTRACT A new crash mode will be introduced in the North American market If the existing 56kph frontal crashworthiness was one of the most important challenges for the manufacturer, the 90kph 15 inclined 35% overlap collision is an issue in the future. Major injuries that occurred during frontal collision were head acceleration and neck injury, while in new mode, head rotation and neck injury were major injuries. This is to protect passengers in actual crash mode based on actual accident investigation. In addition to the new crash mode, the use of new mode makes it difficult to satisfy passenger injuries with the characteristics of existing airbags. Accordingly, various tasks are being performed by the manufacturers of passive safety systems. Especially, the pressure and performance of PAB are very important because the THOR dummy located in RH side is greatly influenced by PAB performance. In this paper, we analyze the passenger Movement of the RH side and improve the injury through the airbag performance. The thor dummy of the far side is of interest in the left-leaning collision. Plus, North America regulations must also satisfy LRD testing with the same inflator and cushion. In this paper, I propose improvement of airbag which can satisfy both BRIC injury and LRD performance which are main items of OMDB crash test. Especially, we will seek improvement through the inflator optimization and new concept of cushion which is the most important factor of the passenger airbag INTRODUCTION In the new collision mode, the deformable barrier moves at 90 kph on the left side, causing a collision with the vehicle. Existing crash mode and passenger Movement are very different. To improve this, the design concept of the constraint device must be changed. As a result of the existing restraint system, the passenger injury target will not be met. Main NCAP crash mode: 56 kph Full Frontal 90KPH OMDB Dummy change: HIII 5% THOR Head injury: HIC, NECK BRIC = (max / )^2+(max / )^2+(max / )^2 (Equation 1)
CRASH and LRD REQIREMENT Figure 1. New Crash Mode (Vehicle&OMDB, Dummy, Sensor) 1) Rating method for OMDB 1-1) THOR 50% : HIC15 500, BRIC 0.71, Nij 0.39, Cd 37.9mm Less than full scale However, it is judged that Nij 0.39 is relatively easy to obtain by increasing CRITICAL VALUE when THOR 50% Nij calculation, +Fzc : 2520N->4200N, -Fzc : 3640N->6400N, +Myc : 48Nm->88.1Nm, -Myc : 72Nm->117Nm HIC Satisfaction value made easy Below is the result of the new collision mode actual vehicle with the existing restraint system 2) Regulation for LRD 2-1) Based on 6 Year HIC 700 / Nij 1 / Tension 1.49kN Figure 2. Crash Test Result (References to existing papers) The inflator pressure must be sufficient to meet the crash test performance and it is advantageous for the pressure to be low to satisfy the LRD test. As a result, collision performance and LRD performance can have conflicting inflator pressures. Therefore, in North America, a dual-type inflator is generally applied and the 1st gas is used for the LRD evaluation. However since the 1st pressure is higher than the 2nd pressure, LRD venting technology is used because the inflator does not satisfy the performance. In this paper, we will develop an inflator capable of satisfying both collision performance and LRD performance, and introduce PAB cushioning technology which can be advantageous for collision performance As with other products, passive safety devices are also an important issue, and cost reduction and weight reduction are also important issues. It is also intended to prevent the application of cylinder inflator or increase in the number of inflator
Analysis OMDB Vehicle Movement Analysis In the existing North American front 56kph fixed wall test, the Delta V including rebounding is about 63-67kph Except in special cases. In the left side OMDB collision, the X-directional acceleration is about 50kph in Delta V at the RH side. However, lateral movement (Y direction) occurs and the vehicle moves with yawing in the Y direction. The characteristics of each vehicle vary, but the average of the five models is as follows. The travel distance in the Y direction will vary from vehicle to vehicle, the vehicle was analyzed with an average approach. Analysis shows that the vehicle starts to move to 60ms. In other words, it can be seen that the passenger in the vehicle also starts moving in the Y direction with respect to the vehicle in 60 ms. In addition, a movement of about 400 mm occurs until 120 ms when passenger injury ends. In summary, the PAB is able to improve the BRIC injury by early restraining from the start of 60 ms and by controlling the lateral directional Movement of the passenger for a long time up to 120 ms TABLE1. Y Direction Movement according to time Figure 3. Vehicle Movement (Y Direction) Passenger Injury and Movement Analysis The Movement of passengers also depends on the Movement of the vehicle. Rebounding injuries are not taken into consideration, and injuries of passengers generally occur between 60 ms and 120 ms. At the 50ms, it was not easy to improve with the airbag, so the start time of the passenger injury was 60ms. This means that from the moment the vehicle travels in the Y direction by 50 mm in 60 ms, the airbag can limit the head Movement in the Y direction, thereby improving the BRIC injury. It is not easy to improve the Y-direction Movement in the existing airbag shape, and the volume increases in the Y direction or the X direction with respect to the existing airbag, and new technology is applied. Passenger injury characteristics in LRD test The results of analysis of the injury characteristics of the 5 - car model, 6 - year - old pile are as follows. In Head on IP mode, Neck Compression is the main cause of injury. In Chest on IP mode, Tension is the main cause of injury. Generally speaking, in Head on ip mode, the maximum injury time is usually 40ms before and Chest on IP occurs before 60ms. Since the 1st pressure characteristic and the cushion pressure are a very important part of the LRD performance, it is assumed that the early inflator characteristic is a key factor in improving the LRD performance
Method In order to simultaneously improve collision response and LRD performance, the first thing we have done is optimizing the inflator. In order to satisfy the increased volume of the airbag cushion, optimization work was carried out to reduce the 1st inflation gas volume and increase the Full pressure (1 st + 2 nd Pressure) In general, at the development stage, the inflator takes a long time to improve the performance, so the performance is improved in the cushion and the like. However, it is necessary to optimize the performance of the inflator from the beginning of development of the airbag system to strengthen the performance of the airbag. First, the inflator was improved to fill the increased cushioning volume for collision response and improve the LRD performance as follows. It is considered that the performance effect can be improved by the simplest method. In some cases, it may be argued that using of cylinder inflator or inflator increases due to the excessive volume of the cushion. In this paper, we will cover the contents to improve the performance of the inflator to prevent the application of cylinder inflator or increase in the number of inflator. The 1st pressure is minimized to improve the LRD performance and to increase the Full pressure to increase the PAB cushion volume to improve the OMDB crash performance. In addition, we will introduce new cushioning technology to improve OMDB collision performance in the next section. The inflator optimization concept is shown in Figure 4 below. Simply put, I want to lower the 1st pressure as much as possible and the full pressure as much as possible. More specifically, the 1st pressure before 50 ms is lowered, and the 1st + 2nd pressure after 60 ms is higher. CAE Tank Test Figure 4. Gas Volume Concept Over Time The CAE was carried out to find the proper value of the 1st pressure by time. New # 1 and New # 2 values compared to existing mass production specifications. The New # 1 specification was targeted as a test to lower the 50ms upstream pressure which is most sensitive to LRD performance test. New # 2 specification did not go into production due to a problem with the actual inflator manufacturing. Considering the characteristics of inflator production, we set the pressure target as # 1. Figure 5. CAE Result for Inflator Pressure
LRD CAE TEST The pressure of 370kpa was reduced to 310kpa on the basis of 50ms, and the LRD analysis test was performed according to the pressure, and the improvement effect was confirmed. The LRD vent was not applied in the test. It is in 6-year-old Chest on IP mode. The results of the LRD analysis test with the improved inflator are as follows. It can be confirmed that the LRD injury is improved by the pressure reduction. TABLE 2. LRD Test Result (CAE) SLED CAE TEST Based on development experience, the maximum pressure was aimed at 600kpa. Depending on the folding of the cushion, etc., it is based on the history of the company being developed or the history of other companies - Existing inflator pressure: 450 ~ 500kpa & 100L - Cylinder type or additional number) : 700kpa & 150L cushion - Optimized inflator pressure: 600kpa & 120L cushion volume The CAE test applied the new technology of cushion to inflator applying 600kpa pressure. PAB is a device that controls the lateral movement of the dummy by placing the chamber in the direction of the inboard. We were able to confirm the optimal volume and function of the chamber. It was judged that the optimized inflator is suitable for 120L cushion and applied new technology. The main cushion is about 100L and the chamber is installed in the cushion to add 20L. The chamber has a vent that allows gas to pass through it, and it is a vent that keeps the pressure in the chamber closed when the vent is closed. The name was called the closed chamber. The structure is as follows. It is a comparative test between Figure 6 applied a 5L chamber to a 100L cushion and Figure 7 applied a 10L chamber to a 100L main cushion. The results show that Wz value and BRIC are improved at 20L chamber. Figure 6. Small Chamber Figure 7. Big Chamber
Closing Vent Concept The volume of the chamber increased by 20L and the test was performed by applying the new cushion technology. First, I will briefly explain the new technology of cushioning. The chamber was attached to the existing PAB anterior cushion. The chamber on the inboard (LH) side is about 8L and restricts the movement of the passenger head in the inboard direction. In order to fill the internal pressure, a vent is present to inflate the chamber, and after the chamber swells, the vent is closed to maintain the internal pressure. The concept of reducing the head rotation by preventing the left-ward(lh) movement of the passenger's head due to the high internal pressure of the chamber. There is also a 12L chamber on the outboard, which swells up through an open vent. It is a structure for early restraint of passengers. In some cases, 12L chamber on the outboard is possible to be deleted. The concept is shown in Figure 8. below. Figure 8. New PAB Concept Inflator optimization First, we set up 3 parameter for 1 st pressure and five parameters for 1 st + 2 nd pressure optimization. The amount of 1st gas to improve LRD performance was set as a factor of 1st Propellant, booster and diffuser. The amount of full(1 st + 2 nd ) Propellant to improve OMDB was 1st Propellant amount, 2nd Propellant amount, booster, diffuser and TTF. The parameter settings and levels are as follows. Noise factors are not covered in this paper, but deviations due to deviations between products, especially due to the characteristics of the explosives. - 1st pressure: Mixing level (1 factor 4 level, 2 factor 2 level) _ large the better characteristics) - Full pressure: Mixed level (1 factor 4 level, 1factor 3 level, 3 factor 2 level) _ the smaller the better characteristics) TABLE 3. Taguchi Method / L8 Orthogonal Array
The test was carried out with a 60L Tank machine. The 1st pressure was 285kpa based on 50ms similar to the optimal value of analysis. Full pressure resulted in 600kpa based on experience As mentioned earlier. Table 4. 1 st Gas Optimized Result (Left) / 1 st + 2 nd Gas Optimized Result (Right) Figure 9. 1 st Gas Graph Figure 10. 1 st + 2 nd Gas Graph The main influencing factor is the propellant, which is remarkable compared to other factors. See Figure 11~12 below. The final optimized graph is shown in Figure 13 Figure 11. Main Effect for 1 st Gas Pressure Figure 12. Main Effect for 1 st + 2 nd Gas Pressure Figure 13. Final Graph
LRD VEHICLE TEST RESULT LRD vents are in use by many companies. The best approach for airbags that can cause multiple deviations is judged to be a robust design that is insensitive to deviations. The test was conducted under the worst condition without applying the LRD vent, and the results were similar to those of the CAE evaluation. The inflator 1st pressure results were similar to the CAEl results. In the chest on ip mode, you can see that the tension Injury is greatly reduced, which is a test mode to demonstrate that the inflator pressure has been lowered. Figure 14. LRD Test View Table 5. LRD Test Result Sled Final Test Results with New Inflator and New PAB A sled test was conducted using an improved inflator and a new PAB concept. For comparison with existing products, chambers were applied to the cushion shape of existing products and tested. The collision pulse and vehicle movement of existing similar vehicles were reproduced. BRIC injuries start at 60ms, and after 120ms, no maximum occurred. It is possible to confirm that the head rotation is reduced by improving the movement of the head in the inboard direction (LH). The results showed that the Wx and Wz injuries were improved and BRIC injuries were improved by about 0.32. Wy is not improved. Figure 15. Sled Test Result Graph
Table 6. Sled Test Result.. Figure 16. Sled Test View Reference. Frontal Sled Test Result New NCAP is subject to a frontal test with a 5% dummy. The difference with the existing test is that the seat track is moved backwards and the BRIC value is measured. The new inflator and the new cushion were applied and the results were as follows. Table 7. Sled Test Result (Frontal) CONCLUSIONS I tried to improve LRD performance and OMDB collision performance by optimizing important inflator performance which is the most basic of airbag performance. LRD performance has been found to improve performance without lowering the inflator pressure and without applying LRD vents. For neuronal response, the PAB volume is basically increased and the inflator pressure needs to be increased. It also explained the new cushioning technology to limit passenger's Y-axis movement and showed test results. It is necessary to increase the reliability of data through actual vehicle evaluation in the future, and additional tests for the products available by the inflator maker will be necessary. REFERENCES [1] James Saunders 2015 NHTSA OBLIQUE CRASH TEST RESULTS: VEHICLE PERFORMANCE AND OCCUPANT INJURY RISK ASSESSMENT IN VEHICLES WITH SMALL OVERLAP COUNTERMEASURES ESV Paper Number: 15-0108 [2] National Highway Traffic Safety Administration (NHTSA), Department of DEPARTMENT OF TRANSPORTATIONNational Highway Traffic Safety Administration New Car Assessment Program [Docket No. NHTSA-2015-0119]
CAR TO CAR FRONT CRASH EQUIVALENT PROTOCOL Marc Peru, Marie Estelle Caspar, Richard Zeitouni. PSA Groupe, France Marc Dieudonné, Pierre Couvidat, ACTOAT, France Paper number 17-0282 ABSTRACT The target of front crash protocols is to finally represent a «Car to Car» (C2C) impact, which is the most frequent configuration in real life. But C2C is a too complex and costly configuration to be applied on experimental and even numerical point of view. Particularly, a numerical C2C simulation will require many finite elements (F.E.) and so heavy calculation time (with in addition, more numerical bug risks, because modeling the front interface between the 2 cars is complex ) ; and also, the Post calculation analysis is much more heavy ( 2 different cars to be analyzed + twice as biomecanic criteria if dummies models are implemented). Furthermore, some specific criteria (specially compatibility criteria) can t be rated during a C2C crash test, because they need a deformable barrier (which represents a medium car of the market) to be measured : as car front face aggressiveness characteristics, and global car s stiffness (dynamometric force measurement on barrier trolley). The goal of this study is to define the front crash protocol which responds the best at the following problem: -to represent the physics of C2C front crashes -to be easier to use in car design process For that purpose, we will follow the method below : FIRST, we will carry out a theoretical study of the C2C front crash, in order to understand its physical main phenomenon, under 3 different and complementary aspects: -Mathematical aspect with simple models, -Numerical aspect with F.E. calculations, -Experimental aspect with C2C tests analysis. SECONDLY, we will exploit the obtained results, in particular: -Mathematical models to well represent kinematics and global interaction of each car, PERU 1
-Numerical modelling to be efficient to qualify energy absorption, front face interaction area and Pulse of the tested car, -Experimental results to be able to give global physical characteristics usable in car design. THEN, we will discuss and answer to the following questions: -Limitations and disadvantages of theoretical and numerical approaches, -What is the best relevant protocol to represent a C2C front crash and if it is reliable (comparison with others protocols and parametric studies), -How to provide a better compatibility. Finally, we will conclude and open the field. The numerical study was conducted with the cooperation of ACTOAT company and the C2C tests at UTAC laboratory. CONTEXT The accidentology situation shows that the C2C front collisions are the most serious and frequent cases. Of course, there are some cases where geometrical compatibility won t be possible to improve (as the example of a low sedan car and a truck collision): Figure 2 : geometrical comparison oh height of bumper beam & sub-frame Figure 1 : exemple of Bad compatibility impossible to redduce But majority of collisions involve current sedan cars themselves, everywhere in the world. That is the reason why we have first studied the State of the Art, by making a comparison between the geometrical design of front face of a great number of cars (with mixing their mass, size, height differences) : Conclusion : in Japanese and European car markets, majority of cars have a good structural engagement divided into 2 different areas : a lower areas (lower load path or longer sub-frame) and a upper area (bumper structural beam) ; more than one half of the cars haven t still extended their structural engagement in the lower area and still remain aggressive : PERU 2
In addition, the «soft impacts» is a too restrictive hypothesis; more realistic is to introduce a part of «elastic impacts» with the introduction of restitution coefficients (normal and tangent coefficients: en et et) : Figure 3 : example of deficit structural engagement in a real C2C front crash But today, the current crashtest protocols using normalized impactors (rigid wall or offset deformable barrier) aren t able to show correctly this interaction phenomenon between 2 different cars. So it is a worldwide highest safety priority to define and use a protocol which can correctly represent a C2C front crash : this is the goal of our following study. METHODOLOGY First, we carry out a theoretical study of the C2C front crash, in order to understand its physical main phenomenon, under 3 complementary aspects : Figure 4 : mathematical modeling of a C2C with 6 degrees of freedom We apply the impulsions theory at each car : Mathematical Approach A Simple One-Dimensional Model By applying the momentum conservation and the «soft impacts» hypotheses, we can calculate the change of Delta velocity of each car : And also the kinetic momentum theory : This simple formula only gives us some orders of scale ; for example : in a CAR vs TRUCK crash, the mass ratio is high (e.g. a collision involving a truck of 40000kg mass and a heavy car of 2000kg mass, yields a mass ratio of 20:1) : the change of velocity of the car will be multiplied by 20 compared to the truck. A Mathematical Improved Model In real accidentology, the most current case is a CAR to CAR crash with a partial overlap (50% of the width); so to be more precise, we need to take in consideration the rotation phenomenon of each car. PERU 3
Then, we write the kinematics conditions with restitution coefficients which gives us 2 another equations : Figure 5 : C2C front crash with F.E. method Debugging the CAR to CAR model has been difficult and had taken a lot of time; but the final results are relevant: physical behaviour of cars and their deformation modes are symmetric : We have now 6 independent equations with 6 degrees of freedom : it is therefore mathematically possible to solve the problem. We write this equation s system on matrix formulation : Figure 6 : Compared analysis of each car results Where : Intrusion and pulse levels are comparable between the 2 cars : this is physically relevant and so a check for our calculation : We can also solve this equation s system and therefore obtain all the velocities components of each car. Numerical Simulations We have realized in 2016 a FINITE-ELEMENTS (F.E.) modelling of a midsize sedan car. Indeed, this kind of car represents an average car among the whole motor vehicle fleet and also the most widespread car. The first simulation consists in 2 identical cars, with 50% overlap, car against car at opposite 50km/H velocity. Figure 7 : Compared detailed results of each car Experimental Method In context of FIMCAR (Frontal Impact and Compatibility) Group [1], a study about comparison of different crash protocols was conducted (ODB 40% CEVE front crash, 0 RW front crash, PDB barrier different versions & speed) and led up to the new M-PDB (Mobile Progressive Deformable Barrier) protocol : PERU 4
mass (1577 kg as such an average car), and then, we make variation on the car 2 mass : between 850 kg (supermini car) and 2500 kg (heavy car). Figure 8 : M-PDB Front Crash protocol An in-depth analysis were also conducted on a «Supermini» car population in order to rate the relevance of M-PDB protocol about partnerprotection. In order to evaluate the test severity, different test pulses for Supermini cars were compared (all tests coming from FIMCAR database): Figure 10 : Results velocity curves of model Remark: when the masses are the same, the delta velocity of the 2 cars is of course the same (crossing point of the 2 curves) : this is a check of the validity of our mathematical model. Figure 9 : Extract from FIMCAR Data Base One first observation was that M-PDB pulses were intermediate between RW Pulse (NHTSA) and ODB CEVE Pulse (CEE) : on one side, the crash duration of a RW front test is very short because it show a immediate stop of the engine against the rigid wall ; on the other side, the crash duration of a ODB CEVE front test is longer because the CEVE barrier stiffness is now too soft compared to new cars generations. As a conclusion, FIMCAR chose the M-PDB protocol [2] to be more representative of a CAR to CAR crash test because the PDB Barrier (ADAC version), with its progressive stiffness, allows to represent the engine impact on the other car and the increase of car body stiffness at the end of crash (cockpit resistance); moreover, it can qualify and measure the «car compatibility» with the footprint of the tested car inside the barrier. RESULTS Mathematical Study We programed and solved this matrix system: we obtain the final velocities of the 2 cars and therefore the delta velocity of each car. In order to exploit this mathematical model, we fix the car 1 Using the velocities found by our model, we can now calculate the residual kinematic energy of cars at the end of crash. If we suppose that stiffness of cars is identical (case of crash between the same cars), we can also calculate the delta of kinematic energy of each car. Then, making the hypothesis that crushing distance is equally divided between the two cars, we can assume that delta of kinematic energy is equal to absorbed energy for each car. We applied the same mass variation for the car 2, car 1 mass is fixed: Figure 11 : Results energy curves of model Thus, we show the «mass aggressiveness» phenomenon: absorbed energy is directly influenced by the difference of cars mass. Then, we introduce the Ratio of absorbed energy between CAR 2 and CAR 1, and we take the mass of car 1 as a parameter. PERU 5
Figure 12 : Ratio absorbed energy with mass parameter Of course, a difference of stiffness of the car can also still makes even worst the mass aggressiveness, because, generally heavy cars have also higher stiffness. Conclusion: We can see that small cars are always put at a disadvantage compared to the bigger ones. As it is well known that there is a strong relationship between delta velocity and occupant injury risks, small and light cars which have higher injury risk, due to this mass aggressiveness. Figure 13 : Car absorbed energy comparison of different F.E. calculations results Secondly, we chose the most representative protocol in term of car pulse: we consider the pulse of our CAR to CAR font crash and we successively compare it to the Pulse of the other main protocols: Numerical Study We search now the most representative protocol in term of absorbed energy, using the followed method: First, we have calculated the EES with the following formula: We find 48km/h (a few less than the M-PDB protocol); this is a confirmation of the FIMCAR conclusions : 50km/h speed of the M-PDB protocol is lightly more severe than the current others protocols and a speed of 56km/h would be too high to represent a CAR to CAR real crash. Then, we have compared the energy absorption curves, functions of time, between the different front crash protocols, on our medium size sedan car (1577 kg with two THOR dummies inside): Figure 14 : Successively comparison of different F.E. calculations results on Pulse criteria PERU 6
Conclusion: We can see that CAR to CAR is different from: deduct it from global displacement and finally separate each car displacement: -0, RW Front Crash : crash duration too short and medium value of pulse too stiff -40%, CEVE ODB Front Crash: crash duration too long and medium value of pulse too smooth The conclusion is clear: M-PDB Protocol with a speed of 50km/h is the most representative protocol of our CAR to CAR result (in term of absorbed energy, car pulse and intrusions). Testing Study and Tests As the M-PDB test let us measure dynamometric Force, It is possible to predict global FORCE / Displacement at the exchange area of the two cars in combining together the two characteristic of cars with a simple mechanical principle : the car which deformed is the one which have the lower stiffness. Figure 17 : Displacement separation method applied on test results Below, we can see the comparison of crushing characteristics (Force / crushing distance) of each car : Figure 15 : case of a C2C frontal impact against cars with different stiffness We apply this method to a real CAR to CAR front crash Peugeot 3008 vs Renault CLIO (test conducted by UTAC): Figure 18 : Crushing characteristic of each car We see that stiffness of those 2 cars are near : force level of front unit at the beginning and also, force level of cockpit at the end of crash. Nevertheless, Peugeot 3008 and Renault CLIO have different silhouettes (medium SUV for 3008, small Sedan car for CLIO), this CAR to CAR test shows that those cars are quite «compatible» due to the combination of 2 principles: a good structural engagement and a near stiffness. Only mass aggressiveness stills remain because it can t be reduced. LIMITATIONS AND DISCUSSION Figure 16 : C2C Peugeot 3008 vs Renault CLIO (performed by UTAC) We first calculate the global displacement of the 2 cars together (solid movement) and after, we Limitation of theoretical and F-E Calculations We have seen that results of mathematical models are only useful to understand phenomenon and give us order of scales. PERU 7
Concerning F.E. calculations, some difficulties comes from this kind of modeling: -First problem: calculations time but also time to prepare/debug models are too extensive: no compatible to use it, every day, in iterative design process. Figure 20 : Trolley & barrier modelling Trolley PARAMETERS influence : Iterations are conducted, modifying trolley s parameters to study their dispersion on the kinematics of trolley & car: Figure 19 : Time comparison between different kind of F.E. calculations -Second problem : there is a paradox between the complexity of the C2C model itself and the limited results than it can provide for the car design ; indeed, with this kind of FE-model, it is difficult to separate the absorbed energy between each car, and quite impossible to sum the global Force that one car applies to the other one. -Trolley parameters influence: the most influent parameter is the Y- position between barrier and trolley: indeed, on the side of the impact, barrier must cover the wheel of the trolley in order to well represent the interaction between barrier & car and so their kinematics (rotation in the real direction of rotation) : Selection Of The Protocol Efficient For Car Design We have identified the M-PDB protocol as the most relevant in terms of global kinematics, absorbed energy, Pulse variations & intrusions values In addition, this protocol can give to us the 2 main physical characteristics required by an automotive car maker, at the beginning of a new project: - target of energy to be absorbed (to reserve crushing area dimensions), - Force/displacement target law (to design members of front unit of the car) But now, we have to make sure of its repeatability and physic stability. So we ran a complete parametric study on crash conditions & trolley parameters, barrier characteristics and car physical behaviour. Figure 21 : trolley & car kinematics comparison The other trolley s parameters (mass distribution, center of gravity location, tire stiffness ) are less influent. Barrier PARAMETERS influence : -Height of barrier influence : for sedan cars, we found that the value of the top of the barrier has only a small influence on the car deformations and we have found a better stability with the PDB ADAC Barrier version TROLLEY and CRASH conditions : Trolley loading a PDB type barrier (ADAC version) was modelized as following : PERU 8
How To Provide A Better Compatibility As a car maker, we can use these previous results to lead the design of one future car: energy absorption target, force / displacement characteristic, structural engagement area and stiffness of front unit and cockpit are the input data to guide a preliminary draft. Figure 22 : Barrier & car interaction comparison In particular, a lower load path is a good way to make sure a good structural engagement (the first condition to a good compatibility) as we can see with the C2C Peugeot 3008 / Renault CLIO : Car dispersion influence : Car behavior influence: results on car behavior are only small dispersed (but we have used a car model which has a stable behavior) : Figure 24 : Lower load paths efficient for a good structural engagement In a first sight, between those 2 cars, compatibility seems to be quite GOOD. Figure 25 : Peugeot 3008 & Renault CLIO after C2C test (UTAC) Figure 23 : Dispersion analysis on car behavior CONCLUSIONS PERU 9
The purpose of Compatibility in front crash is to represent a C2C front crash which is the most frequent configuration in real accidentology. But C2C is a too complex and costly configuration to be applied on experimental and even numerical point of view. Furthermore, some specific criteria can t be directly measured during a C2C test or FEcalculation, as global force entrance between Cars and Barrier, distribution of forces and absorbed energy at the interface between cars. Yet, an automotive car maker needs to use simplified, relevant and quick tools to be efficient in preliminary drafts design of future cars. That is the reason why we have first developed simplified mathematical models which allow us to forecast and quantify the kinematic parameters of the 2 cars (delta velocity and energy variation): we used them to study the «mass aggressiveness» phenomenon, showing the disadvantage for small cars. Then, we have determined that the M-PDB 50km/h 50% is the most representative of the C2C configuration (regarding the pulse point of view); we have studied also the repetitiveness/ dispersion of this protocol. Finally, we have analyzed the phenomenon of structural interaction between front faces of cars; we have used a method to extract «Force / crushing distance» and other physical characteristics which can explain the «geometrical and stiffness aggressiveness» phenomenon. Of course, the field of compatibility still remains large and open, but this study gives us the efficient physical parameters as input data to specify and design the future cars at PSA Groupe. TECHNICAL REFERENCES : [1] -FIMCAR : FINAL REPORT = Review and Metric Development (2013 : Ignacio Lazaro, Nicolas Vié, Robert Thomson, Holger Schwedheim) [2] -The Development of a Mobile Deformable Barrier Test Procedure (2012 : Richard Schram : TNO) [3] -EU-Project FIMCAR : Synthesis of test procedure (2011 : Thorsten Adolph, Marcus Wisch) PERU 10