Biofidelity assessment of the GHBMC M50-O in a rear-facing seat configuration during high-speed frontal impact.

The objective of this study was to assess the biofidelity of the Global Human Body Models Consortium (GHBMC) 50th male (M50-O) v6.0 seated in an upright (25-degree recline) all-belts-to-seat (ABTS) in a 56 km/h rear-facing frontal impact. The experimental boundary conditions from the post-mortem human subjects (PMHS) tests were replicated in the computational finite element (FE) environment. The performance of the rigidized FE ABTS model obtained from the original equipment manufacturer was validated via simulations using a Hybrid III FE model and comparison with experiments. Biofidelity of the GHBMC M50-O was evaluated using the most updated NHTSA Biofidelity Ranking System (BRS) method, where a biofidelity score under 2 indicates that the GHBMC response varies from the mean PMHS response by less than two standard deviations, suggesting good biofidelity. The GHBMC M50-O received an occupant response score and a seat loading score of 1.71 and 1.44, respectively. Head (BRS = 0.93) and pelvis (BRS = 1.29) resultant accelerations, and T-spine (avg. BRS = 1.55) and pelvis (BRS = 1.66) y-angular velocities were similar to the PMHS. The T-spine resultant accelerations (avg. BRS = 1.93) and head (BRS = 2.82), T1 (BRS = 2.10) and pelvis (BRS = 2.10) Z-displacements were underestimated in the GHBMC. Peak chest deflection in the anterior-posterior deflection in the GHBMC matched with the PMHS mean, however, the relative upward motion of abdominal contents and subsequent chest expansion were not observed in the GHBMC. Updates to the GHBMC M50-O towards improved thorax kinematics and mobility of abdominal organs should be considered to replicate PMHS characteristics more closely.

Analysis of injury mechanism and thoracic response of elderly, small female PMHS in near-side impact scenarios.

OBJECTIVE: In 2020, 17% of all crash fatalities were individuals aged 65 years or older. Crash data also revealed that for older occupants, thoracic related injuries are among the leading causes of fatality. Historically, the majority of near-side impact postmortem human subjects (PMHS) studies used a generic load wall to capture external loads that were applied to PMHS. While these data were helpful in documenting biofidelity, they did not represent a realistic response an occupant would undergo in a near-side crash. The objective of this research was to test small, elderly female PMHS in a repeatable, realistic near-side impact crash scenario to investigate current injury criteria as they relate to this vulnerable population. METHOD: Ten small, elderly PMHS were subjected to a realistic near-side impact loading condition. The PMHS were targeted to be elderly females age 60+, approximately 5th percentile in height and weight, with osteopenic areal bone mineral density. Each subject was seated on a mass-production seat, equipped with a side airbag and standard three-point restraint with a pretensioner. Other boundary conditions included an intruding driver's side door. PMHS instrumentation included strain gages on ribs 3-10 bilaterally to identify fracture timing. Two chestbands were used to measure chest deflection, one at the level of the axilla and one at the level of the xiphoid process. RESULTS: Injuries observed included rib fractures, particularly on the struck side, and in multiple cases a flail chest was observed. Eight of ten subjects resulted in AIS3+ thoracic injuries, despite previously tested ATDs predicting less than a 10% chance of AIS3+ injury. Subjects crossed the threshold for AIS3 injury in the range of only 1% - 9% chest compression. Additionally, mechanisms of injury varied, as some injuries were incurred by door interactions while others came during airbag interactions. CONCLUSIONS: This research points to two areas of concern that likely require further analysis: (1) the appropriateness of potentially oversimplified PMHS testing to establish injury thresholds and define injury criteria for complicated crash scenarios; (2) the importance of identifying the precise timing of injuries to better understand the effect of current passive restraint systems.

Abdominal biofidelity assessment of 5th percentile female ATD responses relative to recently developed belt and bar loading corridors.

OBJECTIVE: The objective of this study was the quantitative evaluation and comparison of the responses of the Hybrid III 5th percentile female (HIII-05F) and the 5th percentile female Test Device for Human Occupant Restraint (THOR-05F) anthropomorphic test devices (ATDs) subjected to abdominal loading conditions. METHOD: The HIII-05F and THOR-05F were subjected to 3 different abdominal loading conditions: fixed-back belt pull (low compression), fixed-back belt pull (high compression), and free-back rigid bar impact at 6 m/s. The stroke of the impact was controlled to represent injurious and noninjurious loading conditions as observed in the experiments with postmortem human subjects (PMHS). Quantitative comparisons were made between the ATD abdominal force and compression responses and biofidelity corridors obtained from matched-pair PMHS tests under identical loading conditions, using the most recent version of the NHTSA Biofidelity Ranking System (BRS). RESULTS: The overall THOR-05F BRS scores across all tests (BRS score = 1.84) indicated good biofidelity. For the belt loading test conditions, the average BRS scores for both THOR-05F (BRS scores = 1.45 and 1.34) and HIII-05F (BRS scores = 1.42 and 1.01) showed good biofidelity. For the rigid bar loading condition, the THOR-05F (BRS score = 2.74) showed better biofidelity compared to HIII-05F (BRS score = 10.63), with the HIII-05F exhibiting poor performance in this condition. The average pressures recorded by the abdomen pressure twin sensors (APTS) in the current study ranged from 45 to 130 kPa, increasing proportionally with higher stroke and loading rate. CONCLUSIONS: Overall, the THOR-05F BRS scores were better than the HIII-05F BRS scores, which suggests improved biofidelity of the THOR-05F abdomen. The abdominal insert in the HIII-05F did not provide enough room for compression, leading to higher stiffness and occupant motion as observed in the rigid bar tests. Because of practical challenges in measuring abdomen deflection in a soft ATD abdomen component, use of APTS in THOR-05F provides the ability to measure the restraint loading to the abdomen and assess the risk of abdominal injury. With good BRS scores observed in this study for THOR-05F, pressure and other measurements included in the THOR-05F may be used to develop abdominal injury risk functions in the future.

Thoracic responses and injuries to male postmortem human subjects (PMHS) in rear-facing seat configurations in high-speed frontal impacts.

Objective: One potential nonstandard seating configuration for vehicles with automated driving systems (ADS) is a reclined seat that is rear-facing when in a frontal collision. There are limited biomechanical response and injury data for this seating configuration during high-speed collisions. The main objective of this study was to investigate thoracic biomechanical responses and injuries to male postmortem human subjects (PMHS) in a rear-facing scenario with varying boundary conditions.Method: Fourteen rear-facing male PMHS tests (10 previously published and 4 newly tested) were conducted at two different recline angles (25-degree and 45-degree) in 56 km/h frontal impacts. PMHS were seated in two different seats; one used a Fixed D-Ring (FDR) seat belt assembly and one used an All Belts To Seat (ABTS) restraint. For thoracic instrumentation, strain gages were attached to ribs to quantify strain and fracture timing. A chestband was installed at the mid-sternum level to quantify anterior-posterior (AP) chest deflections. Data from the thorax instrumentation were analyzed to investigate injury mechanisms.Results: The PMHS sustained a greater number of rib fractures (NRF) in the 45-degree recline condition (12 ± 7 NRF for ABTS45 and 25 ± 18 NRF for FDR45) than the 25-degree condition (6 ± 4 NRF for ABTS25 and 12 ± 8 NRF for FDR25), despite AP chest compressions in the 45-degree condition (-23.7 ± 9.4 mm for ABTS45 and -39.6 ± 11.9 mm for FDR45) being smaller than the 25-degree condition (-38.9 ± 16.9 mm for ABTS25 and -55.0 ± 4.4 mm for FDR25). The rib fractures from the ABTS condition were not as symmetric as the FDR condition in the 25-degree recline angle due to a belt retractor structure located at one side of the seatback frame. Average peak AP chest compression occurred at 45.7 ± 3.4 ms for ABTS45, 45.6 ± 3.1 ms for FDR45, 46.7 ± 1.9 ms for ABTS25, and 46.9 ± 2.3 ms for FDR25. Average peak seatback resultant force occurred at 43.9 ± 0.9 ms for ABTS45, 44.6 ± 0.8 ms for FDR45, 42.5 ± 0.2 ms for ABTS25, and 41.5 ± 0.5 ms for FDR25. The majority of rib fractures occurred after peak AP chest compression and peak seatback resultant force likely due to the ramping motion of the PMHS, which might create a combined loading (e.g., AP deflection and upward deflection) to the thorax. Although NRF in the 45-degree reclined condition was greater than the 25-degree recline condition, similar magnitudes of rib strains were observed regardless of seat and restraint types, while strain modes varied.Conclusions: The majority of rib fractures occurred after peak AP chest compression and peak seatback force, especially in FDR25, ABTS45, and FDR45, while the PMHS ramped up along the seatback. AP chest compression, seatback load, and strain measured along the rib could not explain the greater NRF in the 45-degree recline conditions. A complex combination of AP chest deflection with upward deflection was discovered as a possible mechanism for rib fractures in PMHS subjected to rear-facing frontal impacts in this study.

Comparison of small female PMHS thoracic responses to scaled response corridors in a frontal hub impact.

OBJECTIVE: The purpose of this study was to generate biomechanical response corridors of the small female thorax during a frontal hub impact and evaluate scaled corridors that have been used to assess biofidelity of small female anthropomorphic test devices (ATDs) and human body models (HBMs). METHODS: Three small female postmortem human subjects (PMHS) were tested under identical conditions, in which the thorax was impacted using a 14.0 kg pneumatic impactor at an impact velocity of 4.3 m/s. Impact forces to PMHS thoraces were measured using a load cell installed behind a circular impactor face with a 15.2 cm diameter. Thoracic deflections were quantified using a chestband positioned at mid-sternum. Strain gages installed on the ribs and sternum identified fracture timing. Biomechanical response corridors (force-deflection) were generated and compared to scaled small female thoracic corridors using a traditional scaling method (TSM) and rib response-based scaling method (RRSM). A BioRank System Score (BRSS) was used to quantify differences between the small female PMHS data and both scaled corridors. RESULTS: Coefficients of variation from the three small female PMHS responses were less than 2% for peak force and 7% for peak deflection. Overall, the scaled corridor means determined from the TSM and RRSM were less than two standard deviations away from the mean small female PMHS corridors (BRSS < 2.0). The RRSM resulted in smaller deviation (BRSS = 1.1) from the PMHS corridors than the TSM (BRSS = 1.7), suggesting the RRSM is an appropriate scaling method. CONCLUSIONS: New small female PMHS force-deflection data are provided in this study. Scaled corridors from the TSM, which have been used to optimize current safety tools, were comparable to the small female PMHS corridors. The RRSM, which has the great benefit of using rib structural properties instead of requiring whole PMHS data, resulted in better agreement with the small female PMHS data than the TSM and deserves further investigation to identify scaling factors for other population demographics.

Biomechanical Response Targets of Adult Human Ribs in Frontal Impacts.

Thorax injuries mainly due to rib fractures have been associated with high rates of morbidity and mortality in motor vehicle crashes. Thoracic biomechanics has been studied extensively, but there are no robust biomechanical response targets for ribs that consider age, sex, body size, and vulnerability factors. The objective of this study was to generate biomechanical targets for human rib response with respect to age, sex, and body size. Two-hundred sixty-one ribs from 171 individuals were dynamically loaded to failure in anterior-posterior bending. Force and displacement at the time of fracture in young adults were greater than in older adults (p < 0.0001). Sex differences were found in those over 40 years old (p < 0.0001). Fracture force from 5th percentile female ribs was lower than 50th and 95th male (p < 0.005). Vulnerable ribs were successfully identified by examining the percentile of both force and displacement at the time of fracture in the proposed samples. The biomechanical targets generated in this study will have useful applications to computational thorax and rib models to aid in injury prevention measures.

Biomechanical Responses and Injury Assessment of Post Mortem Human Subjects in Various Rear-facing Seating Configurations.

The objective of this study was to generate biomechanical corridors from post-mortem human subjects (PMHS) in two different seatback recline angles in 56 km/h sled tests simulating a rear-facing occupant during a frontal vehicle impact. PMHS were placed in a production seat which included an integrated seat belt. To achieve a repeatable configuration, the seat was rigidized in the rearward direction using a reinforcing frame that allowed for adjustability in both seatback recline angle and head restraint position. The frame contained instrumentation to measure occupant loads applied to the head restraint and seatback. To measure PMHS kinematics, the head, spine, pelvis, and lower extremities were instrumented with accelerometers and angular rate sensors. Strain gages were attached to anterior and posterior aspects of the ribs, as well as the mid-shaft of the femora and tibiae, to determine fracture timing. A chestband was installed at the mid sternum to quantify chest deformation. Biomechanical corridors for each body and seat location were generated for each recline angle to provide data for quantitatively evaluating the biofidelity of ATDs and HBMs. Injuries included upper extremity injuries, rib fractures, pelvis fractures, and lower extremity injuries. More injuries were documented in the 45-degree recline case than in the 25-degree recline case. These injuries are likely due to the excessive ramping up and corresponding kinematics of the PMHS. Biomechanical corridors and injury information presented in this study could guide the design of HBMs and ATDs in rigid, reclined, rear-facing seating configurations during a high-speed frontal impact.

A Novel Approach to Scaling Age-, Sex-, and Body Size-Dependent Thoracic Responses using Structural Properties of Human Ribs.

Thoracic injuries are frequently observed in motor vehicle crashes, and rib fractures are the most common of those injuries. Thoracic response targets have previously been developed from data obtained from post-mortem human subject (PMHS) tests in frontal loading conditions, most commonly of mid-size males. Traditional scaling methods are employed to identify differences in thoracic response for various demographic groups, but it is often unknown if these applications are appropriate, especially considering the limited number of tested PMHS from which those scaling factors originate. Therefore, the objective of this study was to establish a new scaling approach for generating age-, sex-, and body size- dependent thoracic responses utilizing structural properties of human ribs from direct testing of various demographics. One-hundred forty-seven human ribs (140 adult; 7 pediatric) from 132 individuals (76 male; 52 female; 4 pediatric) ranging in age from 6 to 99 years were included in this study. Ribs were tested at 2 m/s to failure in a frontal impact scenario. Force and displacement for individual ribs were used to develop new scaling factors, with a traditional mid-size biomechanical target as a baseline response. This novel use of a large, varied dataset of dynamic whole rib responses offers vast possibilities to utilize existing biomechanical data in creative ways to reduce thoracic injuries in diverse vehicle occupants.

Sources of Variability in Structural Bending Response of Pediatric and Adult Human Ribs in Dynamic Frontal Impacts.

Despite safety advances, thoracic injuries in motor vehicle crashes remain a significant source of morbidity and mortality, and rib fractures are the most prevalent of thoracic injuries. The objective of this study was to explore sources of variation in rib structural properties in order to identify sources of differential risk of rib fracture between vehicle occupants. A hierarchical model was employed to quantify the effects of demographic differences and rib geometry on structural properties including stiffness, force, displacement, and energy at failure and yield. Three-hundred forty-seven mid-level ribs from 182 individual anatomical donors were dynamically (~2 m/s) tested to failure in a simplified bending scenario mimicking a frontal thoracic impact. Individuals ranged in age from 4 - 108 years (mean 53 ± 23 years) and included 59 females and 123 males of diverse body sizes. Age, sex, body size, aBMD, whole rib geometry and cross-sectional geometry were explored as predictors of rib structural properties. Measures of cross-sectional rib size (Tt.Ar), bone quantity (Ct.Ar), and bone distribution (Z) generally explained more variation than any other predictors, and were further improved when normalized by rib length (e.g., robustness and WBSI). Cortical thickness (Ct.Th) was not found to be a useful predictor. Rib level predictors performed better than individual level predictors. These findings moderately explain differential risk for rib fracture and with additional exploration of the rib's role in thoracic response, may be able contribute to ATD and HBM development and alterations in addition to improvements to thoracic injury criteria and scaling methods.

Quantification of Skeletal and Soft Tissue Contributions to Thoracic Response in a Dynamic Frontal Loading Scenario.

Thoracic injuries continue to be a major health concern in motor vehicle crashes. Previous thoracic research has focused on 50th percentile males and utilized scaling techniques to apply results to different demographics. Individual rib testing offers the advantage of capturing demographic differences; however, understanding of rib properties in the context of the intact thorax is lacking. Therefore, the objective of this study was to obtain the data necessary to develop a transfer function between individual rib and thoracic response. A series of non-injurious frontal impacts were conducted on six PMHS, creating a loading environment commensurate to previously published individual rib testing. Each PMHS was tested in four tissue states: intact, intact with upper limbs removed, denuded, and eviscerated. Following eviscerated thoracic testing, eight individual mid-level ribs from each PMHS were removed and loaded to failure. A simplified model in which ribs of each thorax are treated as parallel springs was utilized to evaluate the ability of individual rib response data to predict each subject's eviscerated thoracic response. On average across subjects, denuded thoraces retained 89% and eviscerated thoraces retained 46% of intact force. Similarly, denuded thoraces retained 70% and eviscerated thoraces retained 30% of intact stiffness. The rib model did not adequately predict eviscerated thoracic response but provided a better understanding of the influence of connective tissue on a rib's behavior with-in the thorax. Results of this study could be used in conjunction with the database of individual rib test results to improve thoracic response targets and help assess biofidelity of current anthropomorphic test devices.

Rib Geometry Explains Variation in Dynamic Structural Response: Potential Implications for Frontal Impact Fracture Risk.

The human thorax is commonly injured in motor vehicle crashes, and despite advancements in occupant safety rib fractures are highly prevalent. The objective of this study was to quantify the ability of gross and cross-sectional geometry, separately and in combination, to explain variation of human rib structural properties. One hundred and twenty-two whole mid-level ribs from 76 fresh post-mortem human subjects were tested in a dynamic frontal impact scenario. Structural properties (peak force and stiffness) were successfully predicted (p < 0.001) by rib cross-sectional geometry obtained via direct histological imaging (total area, cortical area, and section modulus) and were improved further when utilizing a combination of cross-sectional and gross geometry (robusticity, whole bone strength index). Additionally, preliminary application of a novel, adaptive thresholding technique, allowed for total area and robusticity to be measured on a subsample of standard clinical CT scans with varied success. These results can be used to understand variation in individual rib response to frontal loading as well as identify important geometric parameters, which could ultimately improve injury criteria as well as the biofidelity of anthropomorphic test devices (ATDs) and finite element (FE) models of the human thorax.

Evaluation of a coplanar 6a3ω configuration in the Hybrid III 50th percentile male head.

OBJECTIVES: In order to understand the mechanisms of traumatic brain injury (TBI) and develop proper safety measures, it is essential that accurate instrumentation methods are utilized. The brain injury criterion (BrIC) has been developed and validated to predict brain injuries in combination with the head injury criterion (Takhounts et al. 2011, 2013). Because the validated BrIC is heavily dependent on angular motion, the accuracy of any head instrumentation technique should be judged in part by its ability to measure angular motion. The main objective of this study was to evaluate a method of accurately measuring 6-degree-of-freedom (DOF) anthropomorphic test device (ATD) head kinematics using a coplanar 6 accelerometers and 3 angular rate sensors (6a3ω) configuration. METHODS: A coplanar 6a3ω configuration (c6a3ω) was implemented via a newly designed fixture. The c6a3ω fixture was placed at the center of gravity (CG) of a Hybrid III 50th percentile ATD (HIII 50) head. In addition, a tetrahedron fixture with 9 installed accelerometers (tNAAP) was externally mounted on the posterior surface of the HIII 50 skull cap. The c6a3ω setup also allowed for comparison to the 3a3ω configuration (i3a3ω) by subsequently treating the c6a3ω fixture as an i3a3ω fixture by only using accelerations and angular rates from select sensors. A total of 63 tests were conducted by impacting the head-neck apparatus at various high speeds and directions by a pneumatic ram. Normalized root mean square deviation (NRMSD), peak differences, and uncertainty were used for quantitative evaluation of the 3 configurations (e.g., c6a3ω, i3a3ω, and tNAAP). RESULTS: The average NRMSD and peak differences between the calculated angular accelerations were less than 5% between the tNAAP and the c6a3ω with 5.6% of uncertainty but greater than 18% for NRMSD and 20% for the peak differences between the tNAAP and i3a3ω with 58.2% uncertainty. Average NRMSD and peak differences between transformed resultant linear accelerations and gold standards (accelerations directly measured by accelerometers at the origin of tNAAP or c6a3ω fixtures) were also calculated. The c6a3ω had both NRMSD and peak differences less than 3% (uncertainty of 2.5%), and i3a3ω had NRMSD, peak values, and uncertainty on the order of 20% and higher. The tNAAP was slightly less accurate than the c6a3ω for transformed accelerations (NRMSD and peak differences <6%, uncertainty of 4.6%) and showed NRMSD and peak differences in the 7-8% range for angular velocity and rotation (uncertainty of 4.3 and 6.7%, respectively). CONCLUSIONS: The c6a3ω configuration exhibited much better accuracy for calculating angular acceleration and transformed linear acceleration than the i3a3ω configuration. The tNAAP showed slightly less accurate transformed linear acceleration than the c6a3ω and was demonstrated to have less accuracy than c6a3ω and i3a3ω for calculating angular velocity and rotation. The c6a3ω configuration could be a potential alternative to specialized NAAP ATD heads because all kinematics can be measured near the head CG, and 6a3ω instrumentation provides the most comprehensive 6DOF kinematics (i.e., accelerations, velocities, and displacements) with accuracy.

Opportunities for crash and injury reduction: A multiharm approach for crash data analysis.

OBJECTIVE: A multiharm approach for analyzing crash and injury data was developed for the ultimate purpose of getting a richer picture of motor vehicle crash outcomes for identifying research opportunities in crash safety. METHODS: Methods were illustrated using a retrospective analysis of 69,597 occupant cases from NASS CDS from 2005 to 2015. Occupant cases were analyzed by frequency and severity of outcome: fatality, injury by Abbreviated Injury Scale (AIS), number of cases, attributable fatality, disability, and injury costs. Comparative analysis variables included precrash scenario, impact type, and injured body region. RESULTS: Crash and injury prevention opportunities vary depending on the search parameters. For example, occupants in rear-end crash scenarios were more frequent than in any other precrash configuration, yet there were significantly more fatalities and serious injury cases in control loss, road departure, and opposite direction crashes. Fatality is most frequently associated with head and thorax injury, and disability is primarily associated with extremity injury. Costs attributed to specific body regions are more evenly distributed, dominated by injuries to the head, thorax, and extremities but with contributions from all body regions. Though AIS 3+ can be used as a single measure of harm, an analysis based on multiple measures of harm gives a much more detailed picture of the risk presented by a particular injury or set of crash conditions. CONCLUSIONS: The developed methods represent a new approach to crash data mining that is expected to be useful for the identification of research priorities and opportunities for reduction of crashes and injuries. As the pace of crash safety improvement accelerates with innovations in both active and passive safety, these techniques for combining outcome measures for insights beyond fatality and serious injury will be increasingly valuable.

Male and female WorldSID and post mortem human subject responses in full-scale vehicle tests.

OBJECTIVE: This study compares the responses of male and female WorldSID dummies with post mortem human subject (PMHS) responses in full-scale vehicle tests. METHODS: Tests were conducted according to the FMVSS-214 protocols and using the U.S. Side Impact New Car Assessment Program change in velocity to match PMHS experiments, published earlier. Moving deformable barrier (MDB) tests were conducted with the male and female surrogates in the left front and left rear seats. Pole tests were performed with the male surrogate in the left front seat. Three-point belt restraints were used. Sedan-type vehicles were used from the same manufacturer with side airbags. The PMHS head was instrumented with a pyramid-shaped nine-axis accelerometer package, with angular velocity transducers on the head. Accelerometers and angular velocity transducers were secured to T1, T6, and T12 spinous processes and sacrum. Three chest bands were secured around the upper, middle, and lower thoraces. Dummy instrumentation included five infrared telescoping rods for assessment of chest compression (IR-TRACC) and a chest band at the first abdomen rib, head angular velocity transducer, and head, T1, T4, T12, and pelvis accelerometers. RESULTS: Morphological responses of the kinematics of the head, thoracic spine, and pelvis matched in both surrogates for each pair. The peak magnitudes of the torso accelerations were lower for the dummy than for the biological surrogate. The brain rotational injury criterion (BrIC) response was the highest in the male dummy for the MDB test and PMHS. The probability of AIS3+ injuries, based on the head injury criterion, ranged from 3% to 13% for the PMHS and from 3% to 21% for the dummy from all tests. The BrIC-based metrics ranged from 0 to 21% for the biological and 0 to 48% for the dummy surrogates. The deflection profiles from the IR-TRACC sensors were unimodal. The maximum deflections from the chest band placed on the first abdominal rib were 31.7 mm and 25.4 mm for the male and female dummies in the MDB test, and 37.4 mm for the male dummy in the pole test. The maximum deflections computed from the chest band contours at a gauge equivalent to the IR-TRACC location were 25.9 mm and 14.8 mm for the male and female dummies in the MDB test, and 37.4 mm for the male dummy in the pole test. Other data (static vehicle deformation profiles, accelerations histories of different body regions, and chest band contours for the dummy and PMHS) are given in the appendix. CONCLUSIONS: This is the first study to compare the responses of PMHS and male and female dummies in MDB and pole tests, done using the same recent model year vehicles with side airbag and head curtain restraints. The differences between the dummy and PMHS torso accelerations suggest the need for design improvements in the WorldSID dummy. The translation-based metrics suggest low probability of head injury. As the dummy internal sensor underrecorded the peak deflection, multipoint displacement measures are therefore needed for a more accurate quantification of deflection to improve the safety assessment of occupants.

Biofidelity Evaluation of the THOR and Hybrid III 50th Percentile Male Frontal Impact Anthropomorphic Test Devices.

The objective of this study is to present a quantitative comparison of the biofidelity of the THOR and Hybrid III 50th percentile male ATDs. Quantitative biofidelity was assessed using NHTSA's Biofidelity Ranking System in a total of 21 test conditions, including impacts to the head, face, neck, upper thorax, lower oblique thorax, upper abdomen, lower abdomen, femur, knee, lower leg, and whole-body sled tests to evaluate upper body kinematics and thoracic response under frontal and frontal oblique restraint loading. Biofidelity Ranking System scores for THOR were better (lower) than Hybrid III in 5 of 7 body regions for internal biofidelity and 6 of 7 body regions for external biofidelity. Nomenclature is presented to categorize the quantitative results, which show overall good internal and external biofidelity of the THOR compared to the good (internal) and marginal (external) biofidelity of the Hybrid III. The results highlight the excellent internal and external biofidelity of the THOR thorax.

Biomechanical Responses of PMHS Subjected to Abdominal Seatbelt Loading.

Past studies have found that a pressure based injury risk function was the best predictor of liver injuries due to blunt impacts. In an effort to expand upon these findings, this study investigated the biomechanical responses of the abdomen of post mortem human surrogates (PMHS) to high-speed seatbelt loading and developed external response targets in conjunction with proposing an abdominal injury criterion. A total of seven unembalmed PMHS, with an average mass and stature of 71 kg and 174 cm respectively were subjected to belt loading using a seatbelt pull mechanism, with the PMHS seated upright in a freeback configuration. A pneumatic piston pulled a seatbelt into the abdomen at the level of the umbilicus with a nominal peak penetration speed of 4.0 m/s. Pressure transducers were placed in the re-pressurized abdominal vasculature, including the inferior vena cava (IVC) and abdominal aorta, to measure internal pressure variation during the event. Jejunum tear, colon hemorrhage, omentum tear, splenic fracture and transverse processes fracture were identified during post-test anatomical dissection. Peak abdominal forces ranged from 2.8 to 4.7 kN. Peak abdominal penetrations ranged from 110 to 177 mm. A force-penetration corridor was developed from the PMHS tests in an effort to benchmark ATD biofidelity. Peak aortic pressures ranged from 30 to 104 kPa and peak IVC pressures ranged from 36 to 65 kPa. Updated pressure based abdominal injury risk functions were developed for vascular Pmax and Pmax*Pmax.

The Large Omnidirectional Child (LODC) ATD: Biofidelity Comparison with the Hybrid III 10 Year Old.

When the Hybrid III 10-year old (HIII-10C) anthropomorphic test device (ATD) was adopted into Code of Federal Regulations (CFR) 49 Part 572 as the best available tool for evaluating large belt-positioning booster seats in Federal Motor Vehicle Safety Standard (FMVSS) No. 213, NHTSA stated that research activities would continue to improve the performance of the HIII-10C to address biofidelity concerns. A significant part of this effort has been NHTSA's in-house development of the Large Omnidirectional Child (LODC) ATD. This prototype ATD is comprised of (1) a head with pediatric mass properties, (2) a neck that produces head lag with Zaxis rotation at the atlanto-occipital joint, (3) a flexible thoracic spine, (4) multi-point thoracic deflection measurement capability, (5) skeletal anthropometry representative of a seated child, and (6) an abdomen that can directly measure belt loading. The objective of this study was to evaluate the LODC by comparing its body region and full-body responses to both standard HIII-10C responses and pediatric biomechanical data. In body region tests, the LODC (BioRank = 1.21) showed improved biofidelity over the HIII-10C (BioRank = 2.70). The LODC also exhibited kinematics more similar to pediatric PMHS kinematics in a reconstruction test. In FMVSS No. 213 tests, the LODC was observed to have lower HIC values with the absence of hard chin-to-chest contacts, indicating that chin-to-chest contact severity is mitigated in the LODC design. LODC abdomen pressures and belt penetrations discriminated between restraint conditions. These results suggest the LODC has biofidelic characteristics that make it a candidate for improved assessment of injury risk in restraint system development.

Age and sex alone are insufficient to predict human rib structural response to dynamic A-P loading.

Thoracic injuries from motor vehicle crashes (MVCs) are common in children and the elderly and are associated with a high rate of mortality for both groups. Rib fractures, in particular, are linked to high mortality rates which increase with the number of fractures sustained. Anthropomorphic test devices (ATDs) and computational models have been developed to improve vehicle safety, however these tools are constructed based on limited physical datasets. To-date, no study has explored variation of rib structural properties across the entire age spectrum with data obtained using the same experimental methodology to allow for comparison. One-hundred eighty-four ribs from 93 post mortem human subjects (PMHS) (70 male, 23 female; ages 4-99) were subjected to dynamic bending tests simulating a frontal impact to the thorax. Structural mechanical properties were calculated and a multi-level statistical model quantified the sample variance as explained by age and sex. Displacement (δX), peak force (Fpeak), linear structural stiffness (K), energy absorption to fracture (Utot), and plastic properties including post-yield energy absorption (UPl), plastic displacement (δPl), and the ratio of elastic to secant stiffness (K-ratio) all showed negative relationships with age, while only Fpeak, K, and Utot were dependent on sex. Despite these relationships being statistically significant, only 7-39% of variance is explained by age and only 3-17% of variance is explained by sex. This demonstrates that variability in bone properties is more complex than simply chronological age- and sex-dependence and should be explored in the context of biological mechanisms instead.

The effect of age on the structural properties of human ribs.

Traumatic injury from motor vehicle crashes is a major cause of morbidity and mortality in the United States. The thorax is particularly at risk in motor vehicle crashes and is studied extensively by the injury biomechanics community. Unfortunately, most samples used in such research generally do not include children or the very elderly, despite the common occurrence of thorax injuries at both ends of the age spectrum. Rib fractures in particular, are one of the most common injuries, especially in the elderly, and can greatly affect morbidity, mortality, and quality of life. As the proportion of older adults in the population increases, such age-related fragility fractures will continually grow as a worldwide problem. Additionally, the risk of rib fracture significantly increases with age with confounding deleterious effects. Studies on elderly ribs are not uncommon, however very few studies exist which explore the mechanical properties and behavior of immature human bone, especially of ribs. Previous research identifying rib properties has provided useful information for numerous applications. However, no study has included a comprehensive sample of all ages (pediatric through elderly) in which ribs are tested in the same repeatable set-up. The goal of this study is to characterize differences in rib structural response across the age spectrum. One-hundred forty excised ribs from 70 individuals were experimentally tested in a custom-built pendulum fixture simulating a dynamic frontal impact. The sample includes individuals of ages ranging from six to 99 years old and includes 58 males and 12 females. Reported data include fracture location, displacement in the X and Y directions at fracture (δX, δY), force at fracture (FX), and linear structural stiffness (K). δX and K exhibit a statistically significant linear decrease with age (p<0.0001). FX reveals a trend in which a peak is reached in the young adult years (25-40). Detailed mechanical property data, as provided here, will prove useful for application in computational modeling efforts, which are vital to help prevent injury and to understand injury mechanisms from childhood through old age.

The response of pediatric ribs to quasi-static loading: mechanical properties and microstructure.

Traumatic injury is a major cause of death in the child population. Motor vehicle crashes account for a large portion of these deaths, and a considerable effort is put forth by the safety community to identify injury mechanisms and methods of injury prevention. However, construction of biofidelic anthropomorphic test devices and computational models for this purpose requires knowledge of bone properties that is difficult to obtain. The objective of this study is to characterize the relationship between mechanical properties and measures of skeletal development in the growing rib. Anterolateral segments of 44 ribs from 12 pediatric individuals (age range: 5 months to 9 years) were experimentally tested in three-point bending. Univariate mixed models were used to assess the predictive abilities of development-related variables (e.g., age, stature, histomorphometry, cross-sectional geometry) on mechanical variables (material and structural properties). Results show that stature, in addition to age, may be a reliable predictor of bone strength, and that histomorphometry has potential to explain bone properties and to further our understanding of fracture mechanisms. For example, percent secondary lamellar bone (%Sd.Ar) successfully predicts peak force (F P) and Young's modulus (E). Application of these findings is not restricted to injury biomechanics, but can also be referenced in forensic and anthropological contexts.