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IRCOBI Conference 2018

The IRCOBI conference (The International Research Council On Biomechanics of Injury) has always been very important for the SENIORS Project. It all started in 2015 in Lyon when the IRCOBI organizers provided all that was needed to organize a first workshop. In that workshop, Marcus Wisch, the project coordinator, David Hynd and Paul Lemmen presented what we wanted to do in the project. This was the start of an extremely fruitful discussion with the most relevant worldwide experts in the field of injury biomechanics.

Since that day, the relation with the experts from the IRCOBI network was quite active. A second meeting followed in Málaga and although no meeting was organized in Antwerp in 2017, many of the project partners took the chance of the IRCOBI conference to have bilateral discussions that later on defined some of the project activities and outcome.

The relevance of IRCOBI in the field of biomechanics is out of question and they have been organizing one of the most relevant biomechanics conferences worldwide since 1973. This is of special relevance for SENIORS as one of the main advancements expected were in this specific field. Therefore, we needed to understand from the best experts the best way forward. Finally this also fructified in specific collaborations between entities and share of data that was finally used in SENIORS.

All this ended this autumn, two days before the start of the 2018 IRCOBI conference. On September 10th we organized the SENIORS final event. More than 50 automotive safety experts attended including many industry representatives and other fellow researchers.

We presented the final results of the project in two parts: occupant safety and pedestrian and cyclist safety.

Occupant safety

The occupant safety session included the results on accident statistics, the Human Body Models (HBMs) used to assess the thoracic injury of elderly and the new simulation-based approach to cover a wider range of loading conditions. This new approach represents a significant step forward in integrating virtual tools to the safety systems development process. The use of HBMs for the development of injury risk curves only using simulation-paired tests is pioneering work in the automotive safety field. A main enabler to this work is the generic test rig also developed in SENIORS that enables to have the exact same testing conditions in simulation and physical testing and fosters future research as its design is fully open and public.

This approach enabled the development of injury risk curves for the thorax area and to new criteria to assess elderly safety in cars. These results along with the new test tools developed, such as the 3D printed elderly, overweight female dummy, led to the development of recommendations for frontal impact tests to be implemented in Euro NCAP and regulation.

After that, we had three high level speakers: Jason Forman from the University of Virginia (USA), Volker Sandner from ADAC (Germany) and Philipp Wernicke from BMW (Germany).

Dr. Forman explained the injury risk functions augmentation with HBMs and matching ATD simulations and the potential future use of the generic test rig developed within SENIORS. Mr. Sandner showed the status of the MPDB Euro NCAP Frontal Impact Test procedure (2020, 2022) with focus on use of THOR dummy and expressed the need for a moderate velocity (30-35 km/h) frontal impact test. Finally, Mr. Wernicke commented on the currently available THOR chest injury risk curves/criteria and the planned ACEA activities regarding THOR injury risk curves and criteria noting possible collaborations beyond SENIORS.

We were glad to see that the research community, the industry and the consumer association embraced the project results and are already implementing some of them.

Pedestrian and cyclist safety

During the second session of the event, Oliver Zander presented the results related to the Flex PLI with Upper Body Mass (FlexPLI-UBM) developed in SENIORS. This included the design, simulation and experimental tests, showing a great potential for future implementation in consumer tests. The main issue with the current Flex PLI is the kinematics shown in physical tests. SENIORS has proven that this can be solved by implementing an upper body mass. Additionally, Alba Fornells presented the main results on the Thoracic Injury Prediction Tool (TIPT) also developed in SENIORS. This impactor, developed from the base of a EuroSID-II is at a lower development stage and in SENIORS a feasibility study has been carried out. The impactor shows promising results in predicting thoracic injuries but further development is needed to improve the impactor kinematics and rib deflection readings.

After these presentations three other experts joined us and presented the latest results of their research. Jin Seop Park from Korean NCAP (Korea) presented the roadmap for future developments and implementations in this consumer test programme. After that, Peter Martin from NHTSA (USA) outlined of the current plans for NCAP and legislation in terms of vulnerable road user safety. Finally Takahiro Isshiki from JARI (Japan) showed the latest developments and technical aspects about the aPLI.

The event was quite a success and was a perfect reflection of what SENIORS has been: an open and collaborative process towards the advancement of automotive safety.

The relevance of these projects and the societal impact they have in the mid and long term are not enough emphasized. Research is needed in the automotive safety field, resources are still needed. Even if the safety community accomplished great results in reducing road fatalities in the past years, if we want to achieve Vision Zero we need to double the efforts because every improvement will be twice as hard as the previous one.

You can find all the presentations and materials from the final event here.

 

SENIORS at TRA Vienna 2018

The Transport Research Arena (TRA) is a bi-annual conference co-organised by the European Commission. It is a forum for researchers, companies and public authorities active in the field of transport. Together they share and discuss new ideas, research results, technological solutions and new business models. The TRA 2018 programme included a range of different session formats that offered ample opportunity to share information on recent findings and to discuss the main current and future challenges and opportunities. In the scientific and technical sessions, a broad spectrum of research and innovation activities were discussed, ranging from basic research findings over application-oriented engineering and socio-economic aspects to policies and standards.
The TRA 2018 was organised in Vienna by the Austrian Ministry for Transport, Innovation and Technology, the Austrian Institute of Technology and AustriaTech together with the European Commission.
SENIORS had an important presence in the event by participating in the European Commission stand. There, we showcased the Female Overweight Elderly Dummy and the FlexPLI with the Upper Body Mass. This allowed us to explain the main results of the project not only to various leading figures such as Henrik Hololei (Director-General, DG MOVE – Directorate-General for Mobility and Transport) or Signe Radso (Deputy Director-General, DG RTD — Directorate-General for Research and Innovation), but also to a number of researchers interested in the field of transport.
All the materials presented during the TRA2018 are available here.

 

New generic test rig

 

Collision data analysis has revealed that elderly car occupants are at higher risk of chest injury than younger car occupants, particularly in low or moderate impact speed crashes. SENIORS aims at improving the methods to assess thoracic injury risk.

The traditional approach to develop dummy-based injury criteria and risk functions is to perform paired tests with dummies and post mortem human subjects (PMHS). However, the focus of the available PMHS test data is on higher injury levels and might not be completely representative for modern restraint systems. To overcome this limitation in the development of improved thoracic injury risk functions, a new approach has been applied in SENIORS by performing paired simulations with a THOR dummy model and human body models. The results were then compared with PMHS test data with the desired moderate loading conditions.

The results using these methods can only be fully compared if the test conditions are also comparable (within the constraints of each method). To enable this approach a new simplified and generic test rig was developed both as physical prototype and as finite-element model for testing and simulation respectively. For a more detailed description see Eggers et al. (2017). The aim was to create a more representative set-up of contemporary vehicles, ensuring good test repeatability and enabling the comparison of test results. Requirements for the generic test rig were defined from previous projects such as THORAX (Lemmen et al. 2013; Davidsson et al. 2014). It is based on the Gold Standard fixture (Shaw et al. 2009) as it is simple and easy to use in virtual testing. The new test rig is composed of: (i) a cable seat back, (ii) a foot rest, (iii) a modified seat pan design, (iv) a seatbelt system and (v) a pre-inflated driver airbag (Figure1).

 

Figure 1: Set-up of sled tests with THOR-50M

 

SEAT PAN

The seat pan used is a modified rigid seat developed in an earlier project funded by SAFER and is referred to as the SAFER seat. This seat pan aims to limit the x- and y-displacement of the occupant pelvis similar to a real vehicle seat and that is the reason why we have a seat ramp (Figure 2). More details can be found in a publication by Pipkorn et al. (2016). Also, to measure the loads between occupant and seat a 6-axis load cell was used.

Figure 2: The SAFER Seat used in the SENIORS generic test rig

While in the Gold Standard test fixture the pelvis of the occupant is restrained by a knee bolster, in the SENIORS generic test rig this is accomplished by an increased interaction between the pelvis and the SAFER seat.

BELT SYSTEM

A three-point belt system was defined with adjustable anchor points to evaluate the influence of different belt geometries on chest deflections and injury risk. At the upper shoulder belt anchor point a steel D-ring without any plastic cover was used (Figure 3), which does not need to be replaced between the tests and reduces manufacturer variability. Also, for further simplification and improved repeatability instead of a production buckle a generic one was used with a uniaxial load cell to measure the sum force of lap and shoulder belt in a reliable way (Figure 4). Moreover, a generic load limiter was integrated into the test rig which was developed by the Centre for Applied Biomechanics at the University of Virginia to achieve representative but still repeatable results (Figure 5).

Figure 3: D-ring

Figure 4: Generic buckle

Figure 5: Generic belt load limiter

 

 

 

 

 

 

 

 

 

 

GENERIC DRIVER AIRBAG

The introduction of a generic driver airbag in the set-up is one of the main improvements. It consists of a generic statically pre-inflated driver airbag, which was developed to be useable multiple times enabling distributed airbag loading to the occupant but, at the same time, avoiding production components to maximise repeatability. Also, a system to keep the pressure conditions was integrated. Moreover, an external wrap was introduced to achieve the desired shape of a standard airbag, which also kept the oscillation of the bag (Figure 6)under control. Parameters such as initial pressure, venting size or venting trig time are adjustable to simulate different conditions.

Figure 6: Generic airbag

 

TEST

We carried out several physical tests and simulations with the THOR-M dummy in the generic test set-up in different configurations (Figure 7) to adjust the restraint systems with the required parameters in order to achieve the desired loading performance. The aim was to achieve reasonable occupant kinematics and a distributed chest loading which results in a low range of AIS3+ chest injury risk. The tests were performed at:
• Two different deceleration pluses (25 km/h with an acceleration peak of 13 g and 35 km/h with an acceleration peak of 17 g)
• Three different positions of the upper shoulder belt anchor point were investigated: D1, D2 and D3

Figure 7: Physical and simulation tests with the THOR-M dummy

Moreover, these tests enabled the validation of the SENIORS generic sled model where the generic driver airbag model was integrated. Prior to that, a finite-element model of the generic driver airbag was developed and its response correlated by means of linear impactor tests at 7 m/s using an impactor mass of 22 kg (Figure 8).

 

Figure 8: Impactor test and FE-model simulation

 

CONCLUSIONS

The results observed in the THOR-M dummy tests at different configurations were more representative of the loading regarding a contemporary vehicle than most available PMHS tests. However, the parameter configuration finally proposed still showed a predicted injury risk higher than the desired moderate loading. A possible explanation might be the absence of a pretensioner which is a restraint component available in most contemporary vehicles. To achieve the desired loading with moderate severity chest loading in the future, it might be necessary to develop a generic pretensioner component.

 

References
Davidsson, J.; Carroll, J.; Hynd, D.; Lecuyer, E.; Song, E.; Trosseille, X.; Eggers, A.; Sunnevang, C.; Praxl, N.; Martinez, L.; Lemmen P. and Been, B. (2014). Development of injury risk functions for use with the THORAX Demonstrator; an updated THOR. Proceedings of IRCOBI Conference, 2014, Berlin, Germany.
Eggers A, Ott J, Pipkorn B, Bråse D, Mroz K, López Valdés F and Hynd D (2017). A generic sled test set-up for frontal occupant evaluation developed within the EU project SENIORS. Proceedings of the 25th Enhanced Safety of Vehicles (ESV) Conference, 5-8 June, Detroit, USA
Lemmen P.; Been B.; Carroll, J.; Hynd, D.; Davidsson, J.; Martinez, L.; García, A.; Vezin, P.; Eggers, A. (2013). An advanced thorax-shoulder design for the THOR dummy. Proceedings of the 23rd International Technical Conference on the Enhanced Safety of Vehicles, 2013, Seoul, Korea.
Pipkorn, Bengt; Lopez‐Valdes, Francisco J.; Juste‐Lorente, Oscar; Maza, Oscar and Sunnevång, Cecilia (2016) Study of the Kinematics of the THOR dummy in Nearside Oblique Impacts. Proceedings of IRCOBI Conference, 2016, Malaga, Spain.
Shaw, G.; Parent, D.; Purtsezov, S.; Lessley, D.; Crandall, J.; Kent, R.; Guillemot, H.; Ridella, S. A.; Takhounts, E; and Martin, P. (2009). Impact response of restrained PMHS in frontal sled tests: skeletal deformation patterns under seat belt loading. Stapp Car Crash Journal, vol. 53 (November 2009), pp. 1-48

Showcasing results of the SENIORS project at #TRA2018

SENIORS will be present at the Transport Research Arena 2018 in Vienna next week showcasing two of the main results of the project: the elderly, overweight dummy and the FlexPLI with Upper Body Mass

Elderly, overweight dummy

In order to represent a population with increased vulnerability to injury, a new Elderly ATD (EATD) has been developed further in SENIORS. The prototype EATD is also based on advanced 3D modelling and cutting-edge 3D printing techniques and materials. The EATD anthropometric specifications were determined as 70-year old, female, and weighing approximately 73 kg with a stature of 1.61 metres (Body Mass Index of 29).

FlexPLI-UBM

A pedestrian torso mass surrogate (UBM – upper body mass) was developed in SENIORS to update the current FlexPLI impactor to significantly change the impact response of the lower limb. The starting point for the improvement of the UBM and the development of a test procedure were comparative simulations with THUMS and the FlexPLI-UBM against generic vehicle frontends. The FlexPLI-UBM shows an improved qualitative and quantitative correlation with Human Body Model simulations. It can be used for the assessment of femur injuries, thus also addressing higher front-end geometries, and for an improved assessment of angled impact areas.

You can visit us at the @EuropeanCommission stand (E02).

 

 

Improving Human Body Models for better elderly protection

The simulation process has gained importance over the last decades for the cost-effective and reliable development of vehicle safety systems. The use of updated Human Body Models (HBMs) is key in the development process in order to deliver trustworthy simulations so that impact protection can be improved. One of the main objectives of the SENIORS project is to investigate and develop HBMs representative for older car occupants.

In the event of a car crash, elderly people tend to suffer more injuries in the thoracic area than other car occupants. For this reason, the improvements developed in SENIORS are focused on the thoracic rib cage for the car occupants, especially on the particularities on rib geometry of elderly people.

The main changes in the body of elderly and overweight people regarding the thorax anatomy are specific geometrical and material property changes. The figure below shows the ribcage geometry for a 35-year-old (blue), the original HBM (green) and a 75-year-old (red).

Overlay of the morphed rib cages in comparison to the original THUMS TUC V3.0.1

Figure 1: Overlay of the morphed rib cages in comparison to the original THUMS TUC V3.0.1

We used one of the most broadly used HBMs in the automotive industry, the THUMS TUC occupant model, to implement age-related material changes and rib cage geometry modifications. For the latter, we used almost 1,000 medical computer tomography scans from ICAM that generated 2D and 3D parameters for a better fitted geometry and consequently more accurate representation of elderly HBM.

Once the HBM was improved, it was time to assess the impact of these changes on the HBM. Using a simplified test condition (table-top seat-belt loading) and sled simulations with the aged model, we found a low effect on stiffness response, but we demonstrated an effect on rib peak strain, which is the most important predictor for rib fractures. Based on this finding, the improved HBM was adopted for further investigations related to rib fracture risk within the subsequent tasks of the SENIORS project.

Positioning of the GHBM on the table-top setup

Figure 2: Positioning of the GHBM on the table-top setup

 

Shortly before a crash, people tend to have a muscular reaction by pushing their arms against the steering wheel. This phenomenon, known as bracing, can have an effect on injury probability. HBMs can also be used to study this effect. To improve the HBMs in this area, in some cases the low-speed volunteers test was used to predict the response of elderly occupants during braking events (similar to what happens after the activation of an AEB system). We then compared these results with the outcome of simulations with HBMs. The correlation of the model output against the experiment was successful, although there is still some room for improvement.

As people age, often their BMI tends to increase (their weight increases), therefore overweight people is also a specific area of interest in SENIORS. The analysed particularities of overweight people are the lower rib angle, the rotation of ribs towards a more horizontal configuration and the tendency to have “rounder” ribs. The figure below shows the shape of the ribs for different weights, from 40 kg (in dark blue) to 175 kg (in red).

Effect of weight on 2D rib shape using a 50 YO, 162 cm female configuration as fixed baseline (source: Holcombe et al. (2017))

Figure3: Effect of weight on 2D rib shape using a 50 YO, 162 cm female configuration as fixed baseline (source: Holcombe et al. (2017)).

 

To study the effect this geometrical change has on potential injuries in car crashes, we compared a simulation of an average female occupant model with a modified overweight female occupant. We used the female occupant as it is more representative of elderly people. The results showed that, for the same seat position, the distance between the head and the instrumental panel for the overweight occupant was less than for the standard occupant and thus increased the risk of injuries in case of bottoming-out the airbag. Moreover, we also found higher neck forces and moments.

All these findings point in the same direction: the diversity of car occupants needs to be considered to improve their safety and HBMs can support this work greatly.

 

 

 

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