Investigation of THOR-AV 5F Biofidelity in Sled Test Conditions with A Semi-Rigid Seat.

THOR-AV 5F, a modified THOR-5F dummy, was designed to represent both upright and reclined occupants in vehicle crashworthiness studies. The dummy was evaluated in four test conditions: a) 25° seatback, 15 km/h, b) 25° seatback, 32 km/h, c) 45° seatback, 15 km/h, d) 45° seatback, 32 km/h. The dummy's biomechanical responses were compared against those of postmortem human subjects (PMHS) tested in the same test conditions. The latest National Highway Traffic Safety Administration (NHTSA) BioRank method was used to provide a biofidelity ranking score (BRS) for each data channel in the tests to assess the dummy's biofidelity objectively. The evaluation was categorized into two groups: restraint system and dummy. In the four test conditions, the restraint system showed good biofidelity with BRS scores of 1.49, 1.47, 1.15, and 1.79, respectively. The THOR-AV 5F demonstrated excellent biofidelity in three test conditions: 25° seatback, 15 km/h (BRS = 0.76); 25° seatback, 32 km/h (BRS = 0.89); and 45° seatback, 32 km/h (BRS = 0.93). In the fourth test condition, 45° seatback, 15 km/h, the dummy demonstrated good biofidelity with a BRS score of 1.06. The dummy demonstrated good durability. No damage was identified with a full inspection conducted after the tests.

Small Female Occupant Response in Reclined and Upright Seated Postures in Frontal Impacts.

The objective of this study was to compare the kinematics of the head-neck, torso, pelvis, and lower extremities and document injuries and their patterns to small female occupants in frontal impacts with upright and reclined postures using an experimental model. Six postmortem human surrogates (PMHS) with a mean stature of 154 ± 9.0 cm and mass of 49 ± 12 kg were equally divided between upright and reclined groups (seatback: 25 deg and 45 deg), restrained by a three-point integrated belt, positioned on a semirigid seat, and exposed to low and moderate crash velocities (15 km/h and 32 km/h respectively). The response between the upright and reclined postures was similar in magnitude and curve morphology. While none of the differences were statistically significant, the thoracic spine demonstrated increased downward (+Z) displacement, and the head demonstrated an increased horizontal (+X) displacement for the reclined occupants. In contrast, the upright occupants showed a slightly increased downward (+Z) displacement at the head, but the torso displaced primarily along the +X direction. The posture angles between the two groups were similar at the pelvis and different at the thorax and head. At 32 km/h, both cohorts exhibited multiple rib failure, with upright specimens having a greater number of severe fractures. Although MAIS was the same in both groups, the upright specimens had more bi-cortical rib fractures, suggesting the potential for pneumothorax. This preliminary study may be useful in validating physical (ATDs) and computational (HBMs) surrogates.

The effect of a moderately reclined seat-back angle on the kinematics of the Large-Omnidirectional Child Anthropomorphic Test Device with and without a belt-positioning booster in frontal crashes.

OBJECTIVE: The effect of reclined seatbacks during frontal crashes in children seated on a belt-positioning booster (BPB) is not understood. Therefore, the aim of this study is to examine submarining in reclined child occupants with and without a BPB and with and without a simulated pre-pretensioner (PPT). We used the Large Omnidirectional Child (LODC) Anthropomorphic Test Device (ATD) seated on a production vehicle seat with and without a moderately reclined seatback angle during sled-simulated frontal vehicle crashes. METHODS: Ten sled-simulated frontal impact tests were performed (24 g peak, 80 ms duration, 56 km/h delta-V). An adjustable D-ring anchor simulated a seat integrated belt. A fixed load-limited 3-point seatbelt webbing system was used to secure the LODC to a vehicle seat and booster seat. We compared the following conditions: a) BPB vs no-BPB and b) 25° versus 45° seatback angles, c) PPT, vs no-PPT in 45° seatback condition, each test was repeated. Abdominal forces (left and right), seatbelt loads, Anterior-Superior-Illiac-Spine forces (ASIS, upper and lower, left and right), and pelvis rotation were analyzed. RESULTS: Average peak abdominal pressures were smaller in both nominal and moderate recline positions in the BPB (25°: 73.7 kPa, 45°: 82.5 kPa) compared to the no-BPB conditions (25°: 168.4 kPa, 45°: 339.1 kPa). In the 45° recline no-BPB conditions, both the peaks of the lap belt force and ASIS forces occurred early and a rapid reduction in those forces followed. This change in the lap belt and ASIS forces accompanied a rearward rotation of the pelvis. During the reduction of ASIS and lap belt forces, there was an increase in abdominal pressure suggesting that the lap belt moved upward, off the ASIS, and into the abdominal pressure sensor. There was a slight reduction in head and knee excursion with the PPT. These results suggest the presence of submarining in the 45° recline no-BPB conditions but not in the 45° recline with the BPB. CONCLUSIONS: The BPB could be beneficial when the seatback is moderately reclined. The differences during the moderate recline between the BPB and no-BPB conditions also indicate that the BPB could prevent submarining in moderately reclined seats.

Obese Occupant Response in Reclined and Upright Seated Postures in Frontal Impacts.

The American population is getting heavier and automated vehicles will accommodate unconventional postures. While studies replicating mid-size and upright fore-aft seated occupants are numerous, experiments with post-mortem human subjects (PMHS) with obese and reclined occupants are sparse. The objective of this study was to compare the kinematics of the head-neck, torso and pelvis, and document injuries and injury patterns in frontal impacts. Six PMHS with a mean body mass index of 38.2 ± 5.3 kg/m2 were equally divided between upright and reclined groups (seatback: 23°, 45°), restrained by a three-point integrated belt, positioned on a semi-rigid seat, and exposed to low and moderate velocities (15, 32 km/h). Data included belt loads, spinal accelerations, kinematics, and injuries from x-rays, computed tomography, and necropsy. At 15 km/h speed, no significant difference in the occupant kinematics and evidence of orthopedic failure was observed. At 32 km/h speed, the primary difference between the cohorts was significantly larger Z displacements in the reclined occupant at the head (190 ± 32 mm, vs. 105 ± 33 mm p < 0.05) and femur (52 ± 18 mm vs. 30 ± 10 mm, p < 0.05). All the moderate-speed tests produced at least one thorax injury. Rib fractures were scattered around the circumference of the rib-cage in the upright, while they were primarily concentrated on the anterior aspect of the rib-cage in two reclined specimens. Although MAIS was the same in both groups, the reclined specimens had more bi-cortical rib fractures, suggesting the potential for pneumothorax. While not statistical, these results suggest enhanced injuries with reclined obese occupants. These results could serve as a data set for validating the response of restrained obese anthropometric test device (ATDs) and computational human body models.

Belt-induced abdominal injuries in recent frontal impact CIREN cases.

OBJECTIVE: The objective is to report sex-related variation in 3-point belt-related abdominal injuries in Crash Injury Research Engineering Network (CIREN) cases. METHODS: A query of CIREN cases was made for those with the highest ranked Collision Deformation Classification (CDC) to the front plane, a principal direction of force (PDOF) ±20° from 0°, and Abbreviated Injury Scale (AIS) 2+ abdomen injuries attributed to the seat belt. Patterns of injury were categorized as above the crest of the ilium, injuries below the crest of the ilium, and injuries above and below the ilium. This was done in the context of autonomous vehicle occupant kinematics testing results. Twelve 5th and 95th percentile 3-point belt-restrained postmortem human subjects were subjects; test speeds and recline angles varied. Abdomen injuries were anticipated; none were observed. RESULTS: Thirty-five occupants with belt-related abdominal injuries were identified. Seventeen case occupants sustained an injury only within the pelvic contents: 5 women and 12 men. Nine of the 17 were at or above the 81st percentile for height, 13 were between the 62nd and 80th percentile for height, and 4 were less than the 50th percentile for height. CONCLUSIONS: The stature component of the body mass index (BMI) appears to be a plausible candidate for an independent variable that is a contributing factor explaining the incidence of pelvic contents injuries when a 3-point belt-restrained occupant is involved in a frontal impact.

Delta-v slope as an indicator of injury.

OBJECTIVE: This study's objective was to examine a crash severity characteristic and the relationship as an indicator of abdominal injury causation. METHODS: Data were analyzed from 23 CIREN case vehicles involved in a frontal type collision, had an AIS 2+ abdominal injury, and contained an electronic data recorder (EDR) download. Data was downloaded from the NHTSA and IIHS crash test databases for comparison. Data was run through a MATLAB algorithm calculating the maximum velocity-time profile slope. This data was compared to the available crash tests. RESULTS: The CIREN vehicle EDR velocity-time slopes ranged from 233 m/s2 to 434 m/s2 for crashes with a delta-v range of 42 km/h to 77 km/h. NHTSA NCAP comparable data was available for all cases, and the slopes ranged from 263 m/s2 to 405 m/s2 calculated from the collected accelerometer. Three comparable tests were available from the IIHS database and the calculated slopes ranged from 252 m/s2 to 298 m/s2. Four test vehicles had EDR data, two each from NHTSA and IIHS and slopes ranged from 245 m/s2 to 281 m/s2. The crash test EDRs slope calculations were lower than the accelerometer data. Nine of the 12 case vehicles had slope values lower than the comparable NCAP accelerometer velocity-time slopes. CONCLUSIONS: Vehicle velocity-time profile can be beneficial to examine the characteristics of crash severity and potential injury. This small sample of field crashes did not indicate a clear relationship of abdominal injury related to crash severity measured by the EDR delta-v slope. EDR results can be considered when determining crash severity, but the limitations need to be understood.

Effectiveness of center-mounted airbag in far-side impacts based on THOR sled tests.

Objective: The study aimed to evaluate the protection offered by a center-mounted airbag in far-side impacts using the Test device for Human Occupant Restraint (THOR) anthropometric test device (ATD). Methods: A rigid buck was designed based on a production vehicle. The buck consisted of a rigid seat, center console, dash, and far-side door structure. The center console and dash were covered with paper honeycomb (152 kPa), and the far-side door structure was covered with Ethafoam 220 padding material. The airbag was mounted on the seat, to the right of the occupant. The THOR-M50 ATD was positioned according to the standard seating procedure and restrained using a standard 3-point seat belt with a pretensioner and retractor. The buck was mounted on an acceleration sled in 2 orientations. Four tests at 45° (oblique) and 2 tests at 90° (lateral) orientations were conducted. Tests were performed with and without an airbag at 30 km/h delta-V and 14 g acceleration. The head accelerations, neck forces and moments, thoracic accelerations and forces, pelvis accelerations, anterior superior iliac spine (ASIS) forces and moments, and belt webbing loads were obtained from sensors, and the external kinematics was obtained using an optical motion capture system and high-speed digital cameras. Results: With the center-mounted airbag, in 90° and 45° tests, reductions were observed for the following parameters: head lateral excursions by 6% and 11%, head vertical excursions by 19% and 26%, and peak head resultant accelerations by 36% and 11%. Other regional accelerations, forces, and moments were also reduced for both impact angles. A reduction in seat belt forces with the airbag was observed in 90° tests. Conclusion: The center-mounted airbag reduced the ATD excursions and accelerations in the 45° and 90° tests, thus reducing the risk of injury due to contact with the intruding structure. The results of this study may assist in designing countermeasures for vehicles in far-side impact.

THOR dummy chest deflection response in oblique and lateral far-side sled tests.

Objective: The focus of this study is side impact. Though occupant injury assessment and protection in nearside impacts has received considerable attention and safety standards have been promulgated, field studies show that a majority of far-side occupant injuries are focused on the head and thorax. The 50th percentile male Test Device for Human Occupant Restraint (THOR) has been used in oblique and lateral far-side impact sled tests, and regional body accelerations and forces and moments recorded by load cells have been previously reported. The aim of this study is to evaluate the chestband-based deflection responses from these tests. Methods: The 3-point belt-restrained 50th percentile male THOR dummy was seated upright in a buck consisting of a rigid flat seat, simulated center console, dashboard, far-side side door structure, and armrest. It was designed to conduct pure lateral and oblique impacts. The center console, dashboard, simulated door structure, and armrest were covered with energy-absorbing materials. A center-mounted airbag was mounted to the right side of the seat. Two 59-gage chestbands were routed on the circumference of the thorax, with the upper and lower chestbands at the level of the third and sixth ribs, respectively, following the rib geometry. Oblique and pure lateral far-side impact tests with and without airbags were conducted at 8.3 m/s. Maximum chest deflections were computed by processing temporal contours using custom software and 3 methods: Procedures paralleling human cadaver studies, using the actual anchor point location and actual alignment of the InfraRed Telescoping Rods for the Assessment of Chest Compression (IR-TRACC) in the dummy on each aspect-that is, right or left,-and using the same anchor location of the internal sensor but determining the location of the peak chest deflection on the contour confined to the aspect of the sensor; these were termed the SD, ID, and TD metrics, respectively. Results: All deformation contours at the upper and lower thorax levels and associated peak deflections are given for all tests. Briefly, the ID metrics were the lowest in magnitude for both pure lateral and oblique modes, regardless of the presence or absence of an airbag. This was followed by the TD metric, and the SD metric produced the greatest deflections. Conclusion: The chestbands provide a unique opportunity to compute peak deflections that parallel current IR-TRACC-type deflections and allow computation of peak deflections independent of the initial point of attachment to the rib. The differing locations of the peak deflection vectors along the rib contours for different test conditions suggest that a priori attachment is less effective. Further, varying magnitudes of the differences between ID and TD metrics underscore the difficulty in extrapolating ID outputs under different conditions: Pure lateral versus oblique, airbag presence, and thoracic levels. Deflection measurements should, therefore, not be limited to an instrument that can only track from a fixed point. For improved predictions, these results suggest the need to investigate alternative techniques, such as optical methods to improve chest deflection measurements for far-side occupant injury assessment and mitigation.

The influence of child restraint lower attachment method on protection offered by forward facing child restraint systems in oblique loading conditions.

OBJECTIVE: The research objective was to quantify the influence of child restraint lower attachment method on head kinematics, head impact potential, and head, neck, and thorax injury metrics for a child occupant secured in a forward-facing child restraint system (FFCRS) in oblique side impacts. METHODS: Fifteen sled tests were conducted with a Q3s seated in an FFCRS secured to the center position on a production small SUV bench seat. Three lower attachment methods were evaluated: rigid ISOFIX, a flexible single loop lower anchors and tethers for children (LATCH) webbing routed through the vehicle belt path of the FFCRS, and dual flexible LATCH webbing attachments on either side of the FFCRS. All were tested with and without a tether with one repeat test in each test condition. The same model FFCRS was used for all tests; only the attachment method varied. The vehicle bench seat was fixed on the sled carriage at 80° (from full frontal). The input pulse was the proposed FMVSS 213 side impact pulse scaled to a 35 km/h delta-v. Two-way analysis of variance (ANOVA) was used to evaluate the effect of lower attachment and tether use on 3 outcome metrics: lateral head excursion, neck tension, and neck lateral bending. Data included anthropomorphic test dummy (ATD) head excursions, head linear accelerations and angular velocities, neck loads and moments, thoracic accelerations, lateral chest deflections, lower anchor loads, and tether webbing loads. ATD head kinematics were collected from 3-dimensional motion capture cameras. RESULTS: Results demonstrated a reduction in injury measures with the rigid ISOFIX and dual webbing attachment compared to the single webbing attachment with decreased lateral head excursions (331, 356, and 441 mm for the rigid ISOFIX, dual webbing, and single webbing systems, respectively, P <.0001), neck tension (1.4, 1.6, and 2.2 kN, P <.01), and neck lateral bending (31.8, 38.7, and 38.0 Nm, P =.002). The tether had a greater influence on lateral head excursion for the FFCRS with flexible webbing attachments than those with the rigid attachment, with the tether forces being highest with the single webbing attachment. Lateral head excursions were significantly lower and lateral neck bending moments were significantly higher with tether use (P <.0001) across all lower attachments. The effect of tether on neck tension was mixed, only showing an increased effect with the rigid ISOFIX system. CONCLUSION: The CRS lower attachment system influenced occupant kinetics. The results indicate that CRS attached to the vehicle via rigid and dual webbing systems exhibit improved kinematics by reducing the rotation and tipping seen with the single webbing attachment. This leads to reduced lateral head excursions and neck tension values. The advantages of the tether in reducing lateral head excursion in side impacts are most pronounced with the flexible webbing attachments. With tether use low in the United States, a dual webbing type FFCRS attachment system may be a better attachment method than single webbing and provide a simpler engineering solution than rigid ISOFIX attachment.

Protection of children in forward-facing child restraint systems during oblique side impact sled tests: Intrusion and tether effects.

OBJECTIVE: Testing was conducted to quantify the kinematics, potential for head impact, and influence on head injury metrics for a center-seated Q3s in a forward-facing child restraint system (FFCRS) in oblique impacts. The influences of a tether and intruded door on these measures were explored. METHODS: Nine lateral oblique sled tests were conducted on a convertible forward-facing child restraint seat (FFCRS). The FFCRSs were secured to a bench seat from a popular production small SUV at the center seating position utilizing the lower anchor and tether for children (LATCH). The vehicle seat was fixed on the sled carriage at 60° and 80° from full frontal (30° and 10° forward rotation from pure lateral) providing an oblique lateral acceleration to the Q3s and FFCRS. A structure simulating an intruded door was mounted to the near (left) side of vehicle seat. The sled input acceleration was the proposed FMVSS 213 lateral pulse scaled to a 35 km/h delta-V. Tests were conducted with and without the tether attached to the FFCRS. RESULTS: Results indicate the influence of the tether on kinematics and injury measures in oblique side impact crashes for a center- or far-side-seated child occupant. All tests without a tether resulted in head contact with the simulated door, and 2 tests at the less oblique angle (80°) with a tether also resulted in head contact. No head-to-door contact was observed in 2 tests utilizing a tether. High-speed video analysis showed that the head moved beyond the CRS head side wings and made contact with the simulated intruded door. Head injury criterion (HIC) 15 median values were 589 without the tether vs. 332 with the tether attached. Tests utilizing a tether had less lateral head excursion than tests without a tether (median 400 vs. 442 mm). CONCLUSION: These tests demonstrate the important role of the tether in controlling head excursion for center- or far-side-seated child occupants in oblique side impact crashes and limiting the head injury potential with an intruded door. The tether may not influence the kinematics of a near-side-seated occupant as strongly where the vehicle door or side structure interacts with the CRS and influences its motion. The results indicate that there may be an opportunity to improve child head kinematics and head protection in oblique side impacts through different CRS attachment methods and/or alternative vehicle side structure protection or padding.

The Influence of Enhanced Side Impact Protection on Kinematics and Injury Measures of Far- or Center-Seated Children in Forward-Facing Child Restraints.

OBJECTIVE: To evaluate the influence of forward-facing child restraint systems' (FFCRSs) side impact structure, such as side wings, on the head kinematics and response of a restrained, far- or center-seated 3-year-old anthropomorphic test device (ATD) in oblique sled tests. METHODS: Sled tests were conducted utilizing an FFCRS with large side wings and with the side wings removed. The CRS were attached via LATCH on 2 different vehicle seat fixtures-a small SUV rear bench seat and minivan rear bucket seat-secured to the sled carriage at 20° from lateral. Four tests were conducted on each vehicle seat fixture, 2 for each FFCRS configuration. A Q3s dummy was positioned in FFCRS according to the CRS owner's manual and FMVSS 213 procedures. The tests were conducted using the proposed FMVSS 213 side impact pulse. Three-dimensional motion cameras collected head excursion data. Relevant data collected during testing included the ATD head excursions, head accelerations, LATCH belt loads, and neck loads. RESULTS: Results indicate that side wings have little influence on head excursions and ATD response. The median lateral head excursion was 435 mm with side wings and 443 mm without side wings. The primary differences in head response were observed between the 2 vehicle seat fixtures due to the vehicle seat head restraint design. The bench seat integrated head restraint forced a tether routing path over the head restraint. Due to the lateral crash forces, the tether moved laterally off the head restraint reducing tension and increasing head excursion (477 mm median). In contrast, when the tether was routed through the bucket seat's adjustable head restraint, it maintained a tight attachment and helped control head excursion (393 mm median). CONCLUSION: This testing illustrated relevant side impact crash circumstances where side wings do not provide the desired head containment for a 3-year-old ATD seated far-side or center in FFCRS. The head appears to roll out of the FFCRS even in the presence of side wings, which may expose the occupant to potential head impact injuries. We postulate that in a center or far-side seating configuration, the absence of door structure immediately adjacent to the CRS facilitates the rotation and tipping of the FFCRS toward the impact side and the roll-out of the head around the side wing structure. Results suggest that other prevention measures, in the form of alternative side impact structure design, FFCRS vehicle attachment, or shared protection between the FFCRS and the vehicle, may be necessary to protect children in oblique side impact crashes.

Injury potential at center rear seating positions in rear-facing child restraint systems in side impacts.

Head injuries occur to occupants of rear-facing child restraint systems in side impacts. This study examined the head injury potential of center-seated occupants using sled tests at change in velocities of 35, 29 and 24 km/h. Other parameters included combinations of with and without a simulated door. A twelve-month-old child dummy was used in combination, convertible and infant rear-facing child restraint systems. Head excursions and head injury criteria (HIC) were obtained. In 35 km/h tests without simulated door, head excursions ranged from 568 to 655 mm, exceeding the simulated door intrusion plane. HIC ranged from 87 to 157, below the 390 limit. At this velocity but with the simulated door, HIC ranged from 804 to 1297. Head excursions ranged from 424 to 480 mm. In 29 and 24 km/h tests, the dummy and child restraint system impacted the simulated door. HIC ranged from 275 to 604 and 141 to 314, and head excursions ranged from 388 to 470 mm and 365 to 460 mm, respectively. Far-side belt loads were 2.4-3.2 kN and 1.7-2.3 kN for the 35 km/h tests without and with the simulated door, and 1.5-2.1 kN and 1.0-1.6 kN for 29 and 24 km/h tests with the simulated door. These findings indicate that occupants in the center seating position in smaller/medium-size vehicles may impact an intruding door and sustain head injuries. A need exists for better protection/attachment methods for center positioned rear-facing child restraint systems to reduce the injury potential in side impacts at velocities greater than 29 km/h.