SAM

Upper Body Skeletal Posture of the Average Pedestrian Male from Upright High-Resolution X-ray Images – Comparison to the THUMS Pedestrian Model

SUBIT, Damien — Thu, 01 Jan 2015 00:00:00 GMT

Upper Body Skeletal Posture of the Average Pedestrian Male from Upright High-Resolution X-ray Images – Comparison to the THUMS Pedestrian Model SUBIT, Damien; PAAS, Ruth; SANDOZ, Baptiste; DAVIDSSON, Johan; LAPORTE, Sébastien No Abstract

The Contribution of Pre-impact Posture on Restrained Occupant Finite Element Model Response in Frontal Impact.

POULARD, David — Thu, 01 Jan 2015 00:00:00 GMT

The Contribution of Pre-impact Posture on Restrained Occupant Finite Element Model Response in Frontal Impact. POULARD, David; SUBIT, Damien; NIE, BINGBING; DONLON, Jean-Paul; KENT, Richard W. Objective: The objective of this study was to discuss the influence of the pre-impact posture to the response of a finite element human body model (HBM) in frontal impacts. Methods: This study uses previously published cadaveric tests (PMHS), which measured six realistic pre-impact postures. Seven postured models were created from the THUMS occupant model (v4.0): one matching the standard UMTRI driving posture as it was the target posture in the experiments, and six matching the measured pre-impact postures. The same measurements as those obtained during the cadaveric tests were calculated from the simulations, and biofidelity metrics based on signals correlation (CORA) were established to compare the response of the seven models to the experiments. Results: The HBM responses showed good agreement with the PMHS responses for the reaction forces (CORA = 0.80 ± 0.05) and the kinematics of the lower part of the torso but only fair correlation was found with the head, the upper spine, rib strains (CORA= 0.50 ± 0.05) and chest deflections (CORA = 0.67 ± 0.08). All models sustained rib fractures, sternal fracture and clavicle fracture. The average number of rib fractures for all the models was 5.3 ± 1.0, lower than in the experiments (10.8 ± 9.0). Variation in pre-impact posture greatly altered the time histories of the reaction forces, deflections and the rib strains, mainly in terms of time delay, but no definite improvement in HBM response or injury prediction was observed. By modifying only the posture of the HBM, the variability in the impact response was found to be equivalent to that observed in the experiments. The postured HBM sustained from 4 to 8 rib fractures, confirming that the pre-impact posture influenced the injury outcome predicted by the simulation. Conclusions: This study tries to answer an important question: what is the effect of occupant posture on kinematics and kinetics. Significant differences in kinematics observed between HBM and PMHS suggesting more coupling between the pelvis and the spine for the models which makes the model response very sensitive to any variation in the spine posture. Consequently, the findings observed for the HBM cannot be extended to PMHS. Besides, pre-impact posture should be carefully quantified during experiments and the evaluation of HBM should take into account the variation in the predicted impact response due to the variation in the model posture.

Experimental investigation of the effect of occupant characteristics on contemporary seat belt payout behavior in frontal impacts.

NIE, Bingbing — Fri, 01 Jan 2016 00:00:00 GMT

Experimental investigation of the effect of occupant characteristics on contemporary seat belt payout behavior in frontal impacts. NIE, Bingbing; POULARD, David; SUBIT, Damien; DONLON, Jean-Paul; FORMAN, Jason L.; KENT, Richard W. Objective: The goal of this study was to investigate the influence of the occupant characteristics on seat belt force vs. payout behavior based on experiment data from different configurations in frontal impacts. Methods: The data set reviewed consists of 58 frontal sled tests using several anthropomorphic test devices (ATDs) and postmortem human subjects (PMHS), restrained by different belt systems (standard belt, SB; force-limiting belt, FLB) at 2 impact severities (48 and 29 km/h). The seat belt behavior was characterized in terms of the shoulder belt force vs. belt payout behavior. A univariate linear regression was used to assess the factor significance of the occupant body mass or stature on the peak tension force and gross belt payout. Results: With the SB, the seat belt behavior obtained by the ATDs exhibited similar force slopes regardless of the occupant size and impact severities, whereas those obtained by the PMHS were varied. Under the 48 km/h impact, the peak tension force and gross belt payout obtained by ATDs was highly correlated to the occupant stature (P = .03, P = .02) and body mass (P = .05, P = .04), though no statistical difference with the stature or body mass were noticed for the PMHS (peak force: P = .09, P = .42; gross payout: P = .40, P = .48).With the FLB under the 48 km/h impact, highly linear relationshipswere noticed between the occupant body mass and the peak tension force (R2 =0.9782) and between the gross payout and stature (R2 =0.9232) regardless of the occupant types. Conclusions: The analysis indicated that the PMHScharacteristics showed a significant influence on the belt response, whereas the belt response obtained with the ATDs was more reproducible. The potential cause included the occupant anthropometry, body mass distribution, and relative motion among body segments specific to the population variance. This study provided a primary data source to understand the biomechanical interaction of the occupant with the restraint system. Further research is necessary to consider these effects in the computational studies and optimized design of the restraint system in a more realistic manner.

Influence of bone microstructure on the mechanical properties of skull cortical bone – A combined experimental and computational approach

BORUAH, Sourabh — Sun, 01 Jan 2017 00:00:00 GMT

Influence of bone microstructure on the mechanical properties of skull cortical bone – A combined experimental and computational approach BORUAH, Sourabh; SUBIT, Damien; PASKOFF, Glenn R; SHENDER, Barry S.; CRANDALL, Jeff R.; SALAZAR, Robert S. The strength and compliance of the dense cortical layers of the human skull have been examined since the beginning of the 20th century with the wide range in the observed mechanical properties attributed to natural biological variance. Since this variance may be explained by the difference in structural arrangement of bone tissue, micro-computed tomography (μCT) was used in conjunction with mechanical testing to study the relationship between the microstructure of human skull cortical coupons and their mechanical response. Ninety-seven bone samples were machined from the cortical tables of the calvaria of ten fresh post mortem human surrogates and tested in dynamic tension until failure. A linear response between stress and strain was observed until close to failure, which occurred at 0.6% strain on average. The effective modulus of elasticity for the coupons was 12.01 ± 3.28 GPa. Porosity of the test specimens, determined from μCT, could explain only 51% of the variation of their effective elastic modulus. Finite element (FE) models of the tested specimens built from μCT images indicated that modeling the microstructural arrangement of the bone, in addition to the porosity, led to a marginal improvement of the coefficient of determination to 54%. Modulus for skull cortical bone for an element size of 50 μm was estimated to be 19 GPa at an average. Unlike the load bearing bones of the body, almost half of the variance in the mechanical properties of cortical bone from the skull may be attributed to differences at the sub-osteon ( < 50 μm) level. ANOVA tests indicated that effective failure stress and strain varied significantly between the frontal and parietal bones, while the bone phase modulus was different for the superior and inferior aspects of the calvarium. The micro FE models did not indicate any anisotropy attributable to the pores observable under μCT.

Will Automated Driving Technologies Make Today's Effective Restraint Systems Obsolete ?

SUBIT, Damien — Sun, 01 Jan 2017 00:00:00 GMT

Will Automated Driving Technologies Make Today's Effective Restraint Systems Obsolete ? SUBIT, Damien; VEZIN, Philippe; SANDOZ, Baptiste; LAPORTE, Sébastien Autonomous driving will trigger a shift in the epidemiology of road traffic injuries that is raising concerns for public health and requires the design of new strategies for the protection of vehicle occupants. Indeed, today's effective protection systems were developed for crashes caused primarily by human errors, and they may be ineffective or even injurious in the new typology of crashes that will arise with the increasing level of automation in vehicles. There is a need to continuously analyze and forecast vehicles behavior on roads as automated driving technologies spread and get updated, to design effective countermeasures and address ethical and public health challenges.

Biofidelity Corridors for Sternum Kinematics in Low-Speed Side Impacts

SUBIT, Damien — Thu, 01 Jan 2015 00:00:00 GMT

Biofidelity Corridors for Sternum Kinematics in Low-Speed Side Impacts SUBIT, Damien; MÖHLER, Felix; PIPKORN, Bengt Objective: Field data show that side impact car crashes have become responsible for a greater proportion of the fatal crashes compared to frontal crashes, which suggests that the protection gained in frontal impact has not been matched in side impact. One of the reasons is the lack of understanding of the torso injury mechanisms in side impact. In particular, the deformation of the rib cage and how it affects the mechanical loading of the individual ribs have yet to be established. Therefore, the objective of this study was to characterize the ribcage deformation in side impacts by describing the kinematics of the sternum relative to the spine. Methods: The 3D kinematics of the 1st and of the 5th or 6th thoracic vertebrae and of the sternum were obtained for three Post Mortem Human Subjects (PMHS) impacted laterally by a rigid wall traveling at 15 km/h. The experimental data were processed to express the kinematics of the sternum relative to the spine throughout the impact event. Methods were developed to interpolate the kinematics of the vertebrae for which experimental data were not available. Results: The kinematics of the sternocostal junction for ribs 1 to 6 as well as the orientation of the sternum were expressed in the vertebra coordinate systems deﬁned for each upper thoracic vertebra (T1 to T6). Corridors were designed for the motion of the sternum relative to each vertebra. In the experiments, the sternum moved upward for all rib levels (1 to 6), and away from the spine with an amplitude that increased with the decreasing rib level (from rib 1 to rib 6). None of the differences observed in the kinematics could be correlated to the occurrence of rib fractures. Conclusions: This study provides both qualitative and quantitative information for the ribcage skeletal kinematics in side impact. This data set provides the information required to better evaluate computational models of the thorax for side impact simulations. The corridors developed in this study provide new bioﬁdelity targets for the impact response of the ribcage. This study contributes to augmenting the state of knowledge of the human chest deformation in side impact to better characterize the rib fracture mechanisms.

The tolerance of the human body to automobile collision impact - a systematic review of injury biomechanics research, 1990-2009.

FORMAN, Jason L. — Thu, 01 Jan 2015 00:00:00 GMT

The tolerance of the human body to automobile collision impact - a systematic review of injury biomechanics research, 1990-2009. FORMAN, Jason L.; LOPEZ-VALDEZ, Francisco J.; DUPREY, Sonia; BOSE, Dipan; DE DIOS, Eduardo Del Pozo; SUBIT, Damien; GILLISPIE, Tim; CRANDALL, Jeff R.; SEGUI-GOMEZ, Maria Road traffic injuries account for 1.3 million deaths per year world-wide. Mitigating both fatalities and injuries requires a detailed understanding of the tolerance of the human body to external load. To identify research priorities, it is necessary to periodically compare trends in injury tolerance research to the characteristics of injuries occurring in the field. This study sought to perform a systematic review on the last twenty years of experimental injury tolerance research, and to evaluate those results relative to available epidemiologic data. Four hundred and eight experimental injury tolerance studies from 1990–2009 were identified from a reference index of over 68,000 papers. Examined variables included the body regions, ages, and genders studied; and the experimental models used. Most (20%) of the publications studied injury to the spine. There has also been a substantial volume of biomechanical research focused on upper and lower extremity injury, thoracic injury, and injury to the elderly – although these injury types still occur with regularity in the field. In contrast, information on pediatric injury and physiological injury (especially in the central nervous system) remains lacking. Given their frequency of injury in the field, future efforts should also include improving our understanding of tolerances and protection of vulnerable road users (e.g., motorcyclists, pedestrians).

Orientation of the Intercostal Muscle Fibers in the Human Rib Cage

SUBIT, Damien — Thu, 01 Jan 2015 00:00:00 GMT

Orientation of the Intercostal Muscle Fibers in the Human Rib Cage SUBIT, Damien; GLACET, Agnès; HAMZAH, Mohsin; CRANDALL, Jeff Great improvement was achieved to protect vehicle occupants in case of a motor vehicle crashes thanks to the development of restraint systems such as seat belts and airbags . These systems increase the mechanical coupling between the human body and the vehicle to minimize the risk of severe injuries to the thorax and the head during a crash. As a result, they may induce injuries, such as rib fractures because of the loading applied to the thorax by the seat belt. Predict- ing and preventing injuries to the thorax is of particular interest as severe injuries occurred predominantly in the thorax in side impact (Welsh et al. 2009) and in elderly subjects. Significant efforts were put in the development of computational finite element models of the thorax to accurately predict the rib fractures created because of an impact (Li et al. 2010). While the mechanical response of the individual human ribs has been widely studied (Charpail et al. 2005; Kindig 2009), only few studies reported on the contribution of the inter- costal muscles (ICM) on the rib cage impact response (Vezin & Berthet 2009). Furthermore, computational studies designed to assess the con- tribution of the ICM in the thorax impact response had to face the lack of detailed description of the ICM structure such as their thickness, and their fiber orientation (Poulard & Subit 2015). Therefore, the goal of this study was to measure the orientation of the fibers in the ICM layers in the human thorax .

Will automated driving technologies obsolete today's effective restraint systems?

SUBIT, Damien — Sun, 01 Jan 2017 00:00:00 GMT

Will automated driving technologies obsolete today's effective restraint systems? SUBIT, Damien; VÉZIN, Philippe; SANDOZ, Baptiste; LAPORTE, Sébastien Autonomous driving will trigger a shift in the epidemiology of road traffic injuries that is raising concerns for public health and requires the design of new strategies for the protection of vehicle occupants. Indeed, today’s effective protection systems were developed for crashes caused primarily by human errors, and they may be ineffective or even injurious in the new typology of crashes that will arise with the increasing level of automation in vehicles. There is a need to continuously analyze and forecast vehicles behavior on roads as automated driving technologies spread and get updated, to design effective countermeasures and address ethical and public health challenges.