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Technical Paper

Update of the WorldSID 50th Male Pelvic Injury Criterion and Risk Curve

Petit et al. 2015 and Lebarbé et al. 2016 reported on two studies where the injury mechanism and threshold of the sacroiliac joint were investigated in two slightly oblique crash test conditions from 18 Post Mortem Human Subjects (PMHS) tests. They concluded that the sacroiliac joint fractures were associated with pubic rami fractures. These latter being reported to occur first in the time history. Therefore it was recommended not to define a criterion specific for the sacroiliac joint. In 2012, injury risk curves were published for the WorldSID dummy by Petitjean et al. For the pelvis, dummy and PMHS paired tests from six configurations were used (n = 55). All of these configurations were pure lateral impacts. In addition, the sacroiliac joint and femur neck loads were not recorded, and the dummy used was the first production version (WorldSID revision 1). Since that time, the WorldSID was updated several times, including changes in the pelvis area.
Technical Paper

Thoracic Injury Investigation using PMHS in Frontal Airbag Out-of-Position Situations

Many studies have reported multiple rib fractures sustained by an Out-of-Position (OOP) driver subjected to a frontal airbag deployment, but the injury mechanisms and thresholds remain unclear. Two successive phases occur during the bag deployment: punch-out loading of the thorax, followed by a membrane effect (Horsch et al. 1990). The aim of this study was to investigate the thoracic injuries generated by each phase separately. Tests of nine post-mortem human surrogates (PMHS) were carried out on a static test bench using a driver side airbag module described by Petit et al. (2003). The steering wheel was replaced by a plate in order to increase the loading generated by the airbag. Three loading configurations were performed: membrane only, punch-out only, and both types combined. The membrane-only tests were performed with the thorax initially positioned at 13, 78 and 128 mm from the plate in order to vary the load magnitude.
Technical Paper

Thoracic Injury Criterion for Frontal Crash Applicable to All Restraint Systems

For several years now, car manufacturers have made significant efforts in the field of thoracic protection. After first limiting the forces in the shoulder belt to 6 kN, these forces are now usually limited to 4 kN, with airbags intentionally designed to absorb the surplus of energy. If this technology is rewarded by a considerable improvement in safety on the road, it remains penalized by the usual biomechanical criteria, when calculated on the Hybrid III and if applied to all restraint systems. To remedy this problem a new criterion, valid in all the current restraint configurations (belt, airbag only or airbag and belt) is proposed. It is based on the measurement of the shoulder belt forces and of the central deflection and consequently is directly applicable to the current dummy model (Hybrid III). The use of shoulder belt forces allows the separation of the belt and airbag contributions to the deflection.
Technical Paper

The Programmed Restraint System - A Lesson from Accidentology

Accident studies show that frontal collisions, both as regards the number of people killed and those seriously-injured, are by far the type of crash with the most serious consequences. In order to improve this situation, it is necessary to ensure that the means used to restrain occupants work as efficiently as possible, whilst preserving the occupant compartment and thus by eliminating intrusion on the occupant restrained by seat-belts and pretensioners. In frontal collisions where vehicle intrusion is minor, the main lesions caused to occupantss are thoracic, mainly rib fractures resulting from the seat-belt. In collisions where intrusion is substantial, the lower members are particularly vulnerable. In the coming years, we will see developments which include more solidly-built cars, as offset crash test procedures are widely used to evaluate the passive safety of production vehicles.
Technical Paper

The Effect of Upper Body Mass and Initial Knee Flexion on the Injury Outcome of Post Mortem Human Subject Pedestrian Isolated Legs

In the ECE 127 Regulation on pedestrian leg protection, as well as in the Euro NCAP test protocol, a legform impactor hits the vehicle at the speed of 40 kph. In these tests, the knee is fully extended and the leg is not coupled to the upper body. However, the typical configuration of a pedestrian impact differs since the knee is flexed during most of the gait cycle and the hip joint applies an unknown force to the femur. This study aimed at investigating the influence of the inertia of the upper body (modelled using an upper body mass fixed at the proximal end of the femur) and the initial knee flexion angle on the lower limb injury outcome. In total, 18 tests were conducted on 18 legs from 9 Post Mortem Human Subjects (PMHS). The principle of these tests was to impact the leg at 40 kph using a sled equipped with 3 crushing steel tubes, the stiffness of which were representative of the front face of a European sedan (bonnet leading edge, bumper and spoiler).
Technical Paper

The Effect of Angle on the Chest Injury Outcome in Side Loading

Thoracic injury criteria and injury risk curves in side impact are based on impactor or sled tests, with rigid or padded surfaces while airbags are very common on current cars. Besides, the loading is generally pure lateral while real crashes or regulations can generate oblique loadings. Oblique tests were found in the literature, but no conclusion was drawn with regard to the effect of the direction on the injury outcome. In order to address these two limitations, a series of 17 side airbag tests were performed on Post Mortem Human Subjects (PMHS) at different severities and angles. The subjects were instrumented with accelerometers on the spine and strain gauges on the ribs. They were loaded by an unfolded airbag at different distances in pure lateral or 30 degrees forward. The airbag forces ranged from 1680 N to 6300 N, the injuries being up to 9 separated fractured ribs. This paper provides the test results in terms of physical parameters and injury outcome of the 17 subjects.
Technical Paper

Study of Rib Fracture Mechanisms Based on the Rib Strain Profiles in Side and Forward Oblique Impact

Rib fractures constitute a good indication of severity as there are the most frequent type of AIS3+ chest injuries. In 2008, Trosseille et al. showed a promising methodology to exhibit the rib fracture mechanisms, using strain gauges glued on the ribs of Post-Mortem Human Subjects (PMHS) and developing a specific signal analysis. In 2009, they published the results of static airbag tests performed on 50th percentile male PMHS at different distances and angles (pure lateral and 30 degrees forward oblique direction). To complete these already published data, a set of 8 PMHS lateral and oblique impactor tests were performed with the same methodology. The rib cages were instrumented with more than 100 strain gauges on the ribs, cartilage and sternum. A 23.4 kg impactor was propelled at 4.3 or 6.7 m/s. The forces applied onto the PMHS at 4.3 m/s ranged from 1.6 kN to 1.9 kN and the injuries varied from 4 to 13 rib fractures.
Technical Paper

Statistical Simulations to Evaluate the Methods of the Construction of Injury Risk Curves

Several statistical methods are currently used to build injury risk curves in the biomechanical field. These methods include the certainty method (Mertz et al. 1996), Mertz/Weber method (Mertz and Weber 1982), logistic regression (Kuppa et al. 2003, Hosmer and Lemeshow 2000), survival analysis with Weibull distribution (Kent et al. 2004, Hosmer and Lemeshow 2000), and the consistent threshold estimate (CTE) (Nusholtz et al. 1999, Di Domenico and Nusholtz 2005). There is currently no consensus on the most accurate method to be used and no guidelines to help the user to choose the more appropriate one. Injury risk curves built for the WorldSID 50th side impact dummy with these different methods could vary significantly, depending on the sample considered (Petitjean et al. 2009). As a consequence, further investigations were needed to determine the fields of application of the different methods and to recommend the best statistical method depending on the biomechanical sample considered.
Technical Paper

Side Impact: Influence of Impact Conditions and Bone Mechanical Properties on Pelvic Response Using a Fracturable Pelvis Model

This study aimed at determining the influence of impact conditions and occupant mechanical properties on pelvic response in side impact. First, a fracturable pelvis model was developed and validated against dynamic tests on isolated pelvic bones and on whole cadavers. By coupling a fixed cortical bone section thickness within a single subject's pelvis and across the population with a parametric material law for the pelvic bone, this model reproduced the pelvic response and tolerance variation among individuals. Three material laws were also identified to represent fragile, medium and strong pelvic bones for the 50th percentile male. With this model, the influence of impact mass, velocity and surface shape on pelvic response was examined. Results indicated that the shape difference between four main impactors reported in the literature has little effect on the pelvic response.
Technical Paper

Sensitivity of the WorldSID 50th and ES-2re Thoraces to Loading Configuration

An ideal injury criterion should be predictive of the risk of injury across the range of loading conditions where it may be applied. The injury risk curve associated with this criterion should be applicable to all loading conditions. With respect to side impact, the injury risk curve should apply to pure lateral or oblique loading by rigid and padded walls, as well as airbags. Trosseille et al., (2009) reported that the number of fractured ribs was higher in pure lateral impact than in forward oblique interaction with an airbag. A good dummy criterion should be able to account for this difference. To evaluate various injury criteria with the WorldSID 50th and ES-2re dummies, the dummies were exposed to the same airbag loadings as the PMHS. The criteria measured in the dummy tests were paired with the rib fractures from the PMHS tests.
Technical Paper

Rib Cage Strain Pattern as a Function of Chest Loading Configuration

Rib fractures are the most frequent types of AIS3+ chest injuries and constitute a good indication of severity. However, the behavior of the rib cage is not well documented, and though chest external measurements are often provided in the literature, the strains of the ribs themselves during a crash remain unknown. In order to address this issue, a test protocol was developed, where the ribs of 8 PMHS were equipped with up to 96 strain gauges. In a first series of 3 tests, the subjects were seated upright and their chests were loaded by a 23.4 kg impactor propelled at 4.3 m/s in 0° (pure frontal), 60° (oblique) and 90° (pure lateral) directions. In a second series of 3 tests, the subjects were loaded by the deployment of an unfolded airbag in the same 3 directions. Finally, a third series of 2 tests was performed with airbags at different distances from the subjects, in a pure lateral direction. This paper presents the results of the tests and an analysis of the strain patterns.
Technical Paper

Relation Between Sacroilium and Other Pelvic Fractures Based on Real-World Automotive Accidents

The study firstly aimed at looking whether sacroilium (SI) fractures could be sustained as unique pelvic injuries in side impact real world automotive accidents. Secondarily, the sacroilium fractures observed in conjunction with other pelvic fractures were analyzed to investigate the existence of injury association patterns. Two real world accident databases were searched for SI fractures. The occupants selected were front car passengers older than 16, involved in side, oblique or frontal impact, with AIS2+ pelvic injuries. In frontal impact, only the belted occupants were selected. The cases were sorted by the principal direction of force (dof) and the type of pelvic injury, namely SI, pubic rami, iliac wing, acetabulum, pubic symphysis, and sacrum injuries. The relation between SI and pubic rami injuries were investigated first. The first database is an accident database composed of cases collected in France by car manufacturers over a period of approximately 40 years.
Technical Paper

Reference PMHS Sled Tests to Assess Submarining of the Small Female

In the last decade, extensive efforts have been made to understand the physics of submarining and its consequences in terms of abdominal injuries. For that purpose, 27 Post Mortem Human Subject (PMHS) tests were performed in well controlled conditions on a sled and response corridors were provided to assess the biofidelity of dummies or human body models. All these efforts were based on the 50th percentile male. In parallel, efforts were initiated to transfer the understanding of submarining and the prediction criteria to the THOR dummies. Both the biofidelity targets and the criteria were scaled down from the 50th percentile male to the 5th percentile THOR female. The objective of this project was to run a set of reference PMHS tests in order to check the biofidelity of the THOR F05 in terms of submarining. Three series of tests were performed on nine PMHS, the first one was designed to avoid submarining, the second and third ones were designed to result in submarining.
Technical Paper

Reference PMHS Sled Tests to Assess Submarining

Sled tests focused on pelvis behavior and submarining can be found in the literature. However, they were performed either with rigid seats or with commercial seats. The objective of this study was to get reference tests to assess the submarining ability of dummies in more realistic conditions than on rigid seat, but still in a repeatable and reproducible setup. For this purpose, a semi-rigid seat was developed, which mimics the behavior of real seats, although it is made of rigid plates and springs that are easy to reproduce and simulate with an FE model. In total, eight PMHS sled tests were performed on this semi-rigid seat to get data in two different configurations: first in a front seat configuration that was designed to prevent submarining, then in a rear seat configuration with adjusted spring stiffness to generate submarining. All subjects sustained extensive rib fractures from the shoulder belt loading.
Technical Paper

Proposed Method for Development of Small Female and Midsize Male Thorax Dynamic Response Corridors in Side and Forward Oblique Impact Tests

Despite the increasing knowledge of the thorax mechanics, the effects of inter-individual differences on the mechanical response are difficult to take into account. Several methods are available in the literature to refine the biofidelity corridors or to extrapolate them to other populations (eg: children, small females, large males). Because of the lack of concrete cases, the relevance of the assumptions is rarely investigated. In 2014, Baudrit et al. published data on thorax dynamic responses of small female and midsize male Post Mortem Human Subjects in side and forward oblique impact tests. The impactor mass was 23.4 kg for all the tests and the nominal impact speed was 4.3 m/s. The diameter of the rigid disk was 130 and 152 mm respectively for the small female specimens and for the midsize male specimens. The authors found that the maximum impact force was a function of the total body mass for each loading.
Technical Paper

New Reference PMHS Tests to Assess Whole-Body Pedestrian Impact Using a Simplified Generic Vehicle Front-End

This study aims to provide a set of reference post-mortem human subject tests which can be used, with easily reproducible test conditions, for developing and/or validating pedestrian dummies and computational human body models against a road vehicle. An adjustable generic buck was first developed to represent vehicle front-ends. It was composed of four components: two steel cylindrical tubes screwed on rigid supports in V-form represent the bumper and spoiler respectively, a quarter of a steel cylindrical tube represents the bonnet leading edge, and a steel plate represents the bonnet. These components were positioned differently to represent three types of vehicle profile: a sedan, a SUV and a van. Eleven post-mortem human subjects were then impacted laterally in a mid-gait stance by the bucks at 40 km/h: three tests with the sedan, five with the SUV, and three with the van.
Technical Paper

Neck Injury Criteria for Children from Real Crash Reconstructions

In view of the lack of data concerning child protection, an accidentological and experimental work was engaged. The goal of this international research involving experts from seven countries was two-fold: In one hand, to establish protection principles, gathering and analysing real crashes involving restrained children. In the other hand, to identify and to quantify injury mechanisms in order to increase knowledge on child tolerances. To realize this second part, real crash reconstructions were performed, in order to correlate observed injuries with recorded parameters on dummies. This paper mainly presents four real crashes with the corresponding reconstructions. A special analysis of injury mechanisms in relation with their respective pertinent parameters is then proposed.
Technical Paper

Methodological Aspects of an Experimental Research on Cerebral Tolerance on the Basis of Boxers' Training Fights

In order to obtain data about human head tolerance, the APR Laboratory of Biomechanics has developed a specific methodology for volunteer boxers. These ones are used because they expose themselves, in their normal body activities, to direct head impacts similar in nature to those experienced by vehicle occupants under crash conditions. This paper describes the specific experimental technique that permits association of the severity of the blows, measured in terms of physical parameters, to corresponding physiological effects, measured in medical terms.
Technical Paper

Laboratory Reconstructions of Real World Frontal Crash Configurations Using the Hybrid III and THOR Dummies and PMHS

Load-limiting belt restraints have been present in French cars since 1995. An accident study showed the greater effectiveness in thorax injury prevention using a 4 kN load limiter belt with an airbag than using a 6 kN load limiter belt without airbag. The criteria for thoracic tolerance used in regulatory testing is the sternal deflection for all restraint types, belt and/or airbag restraint. This criterion does not assess the effectiveness of the restraint 4 kN load limiter belt with airbag observed in accidentology. To improve the understanding of thoracic tolerance, frontal sled crashes were performed using the Hybrid III and THOR dummies and PMHS. The sled configuration and the deceleration law correspond to those observed in the accident study. Restraint conditions evaluated are the 6 kN load-limiting belt and the 4 kN load-limiting belt with an airbag. Loads between the occupant and the sled environment were recorded.
Technical Paper

Kinematics and Dynamics of the Pelvis in the Process of Submarining using PMHS Sled Tests

This study focused on a better understanding and characterization of the submarining phenomenon that occurs in frontal crashes when the lap belt slides over the anterior superior iliac spine. Submarining is the consequence of the pelvis kinematics relative to the lap belt, driven by the equilibrium of forces and moments applied to the pelvis. The study had two primary purposes; the first was to provide new PMHS data in submarining test configurations, the second was to investigate the Hybrid II and Hybrid III dummies biofidelity regarding submarining. Several Post Mortem Human Subject (PMHS) studies have been published on this subject. However, the lack of information about the occupant initial positioning and the use of car seats make it difficult to reconstruct these tests. Furthermore, the two dummies are rarely compared to PMHS in submarining test configurations. A fifteen frontal sled test campaign was carried out on two Anthropomorphic Test Devices (ATDs) and nine PMHS.