Occupant Injury and Response on Oblique-Facing Aircraft Seats: A Computational Study.

Increased interest in the airline industry to enhance occupant comfort and maximize seating density has prompted the design and installation of obliquely mounted seats in aircraft. Previous oblique whole-body sled tests demonstrated multiple failures, chiefly distraction-associated spinal injuries under oblique impacts. The present computational study was performed with the rationale to examine how oblique loading induces component level responses and associated injury occurrence. The age-specific human body model (HBM) was simulated for two oblique seating conditions (with and without an armrest). The boundary conditions consisted of a 16 g standard aviation crash pulse, 45 deg seat orientation, and with restrained pelvis and lower extremities. The overall biofidelity rating for both conditions ranged from 0.5 to 0.7. The validated models were then used to investigate the influence of pulse intensity and seat orientation by varying the pulse from 16 g to 8 g and seat orientation from 0 deg to 90 deg. A total of 12 parametric simulations were performed. The pulse intensity simulations suggest that the HBM could tolerate 11.2 g without lumbar spine failure, while the possibility of cervical spine failure reduced with the pulse magnitude <9.6 g pulse. The seat orientation study demonstrated that for all seat angles the HBM predicted failure in the cervical and lumbar regions at 16 g; however, the contribution of the tensile load and lateral and flexion moments varied with respect to the change in seat angle. These preliminary outcomes are anticipated to assist in formulating safety standards and in designing countermeasures for oblique seating configurations.

An investigation of elderly occupant injury risks based on anthropometric changes compared to young counterparts.

OBJECTIVE: The objective of the study was to investigate the difference between elderly and young occupant injury risks using human body finite element modeling in frontal impacts. METHODS: Two elderly male occupant models (representative age 70-80 years) were developed using the Global Human Body Consortium (GHBMC) 50th percentile as the baseline model. In the first elderly model (EM-1), material property changes were incorporated, and in the second elderly model (EM-2), material and anthropometric changes were incorporated. Material properties were based on literature. The baseline model was morphed to elderly anthropometry for EM-2. The three models were simulated in a frontal crash vehicle environment at 56 km/h. Responses from the two elderly and baseline models were compared with cadaver experimental data in thoracic, abdominal, and frontal impacts. Correlation and analysis scores were used for correlation with experimental data. The probabilities of head, neck, and thoracic injuries were assessed. RESULTS: The elderly models showed a good correlation with experimental responses. The elderly EM-1 had higher risk of head and brain injuries compared to the elderly EM-2 and baseline GHBMC models. The elderly EM-2 demonstrated higher risk of neck, chest, and abdominal injuries than the elderly EM-1 and baseline models. CONCLUSIONS: The study investigated injury risks of two elderly occupants and compared to a young occupant in frontal crashes. The change in the material properties alone (EM-1) suggested that elderly occupants may be vulnerable to a greater risk of head and thoracic injuries, whereas change in both anthropometric and material properties (EM-2) suggested that elderly occupants may be vulnerable to a greater risk of thoracic and neck injuries. The second elderly model results were in better agreement with field injury data from the literature; thus, both anthropometric and material properties should be considered when assessing the injury risks of elderly occupants. The elderly models developed in this study can be used to simulate different impact conditions and determine injury risks for this group of our population.

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.

Deflection-based parametric survival analysis side impact chest injury risk curves AIS 2015.

OBJECTIVES: The objective of this study was to reanalyze lateral postmortem human surrogate (PMHS) sled test chestband data to construct updated lateral thoracic injury risk curves (IRCs) using survival analysis. METHODS: Chestband and injury data were gathered from 16 previously conducted PMHS sled tests. Briefly, 2 chestbands were wrapped around the thorax's circumference at the levels of ribs 4 and 8. Tests were conducted at 6.7 m/s on a rigid and padded load wall fixed to the top of a rebound sled. The injuries were reclassified using the Abbreviated Injury Scale (AIS) 2015 coding scheme. Chestband signals were combined with pretest specimen measurements to calculate the chest deflection contour time history. Deflections were determined using updated processing techniques calculating the change in length of every point on the contour from the impacted side using the thorax's midpoint as the origin. Four candidate metrics were selected: the deflection from rib 4, the deflection from rib 8, the greater of the deflections from ribs 4 and 8, and the average of the deflections from ribs 4 and 8. AIS 3+ IRCs were developed considering outcomes of AIS ≥3 injuries. All injury data were uncensored, and noninjury data were right-censored. Three specimen mass-based IRCs were determined using the IRC with the lowest Brier score metric (BSM): The first corresponded to the 5th percentile female mass (49 kg), the second to the 50th percentile male mass (77 kg), and the third to the average mass of the PMHS ensemble (65 kg). RESULTS: Sixteen PMHS were used in the current study. Six specimens were right-censored, and 10 were uncensored. The average metric had the lowest BSM, and mass was a significant covariate with 50% risk of AIS3+ injury at 72mm of chest deflection. The 50% risk deflection magnitudes for the 5th percentile female (49 kg), 50th percentile male (77 kg), and PMHS ensemble (PMHS-E) (65 kg) were 59, 81, and 71 mm. IRCs for the 4 metrics and the 3 occupant masses are given. CONCLUSIONS: IRCs were developed using survival analysis, and the average of the peak deflections was found to best represent the thoracic chest deflection response. Mass-based side impact IRCs were calculated for occupants representing the WorldSID 5th percentile female and 50th percentile male anthropomorphic test device.

Sagittal plane moment responses of the THOR-05F anthropomorphic test device.

OBJECTIVE: Anthropomorphic test devices (ATD) are used in crashworthiness studies to advance safety in automotive, military, aviation, and other environments. The Test Device for Human Occupant Restraint (THOR) is an advancement over the widely used Hybrid III ATD. The female version THOR-05F is different from the male as it is not a scaled-down version of the male, and it is based on the recognition that the cervical spines (necks) of females have a different response than males. The objective of this study is to evaluate its response at dynamic rates of loading and compare it with previous postmortem human surrogate (PMHS) responses under sagittal plane bending. METHODS: The head/neck assembly was separated from the thorax, and a lower neck plate was attached to the head/neck assembly to mount the preparation to the frame of an electro-hydraulic testing device. A custom upper neck interface plate was attached to a novel angular displacement test device that converted the linear motion of the vertical electrohydraulic piston to moment loading at the occipital condyle joint. The neck was preconditioned by applying a sinusoidal 10-degree flexion-extension cycle for 90 s and then three repeat dynamic tests at a target rate of 90 Nm/s. Flexion and extension tests were performed with and without the front and rear neck cables of the THOR-05F neck. Targets were fixed to the upper neck adapter plate, occipital condyle joint, mid-spine aluminum puck, and lower neck adapter plate. The targets' three-dimensional positions were measured using a seven-camera optical motion capture system. Upper neck load cell and occipital condyle potentiometer data were sampled at 20 kHz, and loading rates were determined by calculating the sagittal moment slope between 15% and 85% of the signal. RESULTS: The mean occipital condyle angle versus sagittal moment response from the 12 tests (three tests each with and without cables and under flexion and extension) are given in the body of the manuscript. With and without cables, the loading rates for flexion tests were 89.3 ± 0.5 Nm/s and 86.3 ± 0.4 Nm/s, and for extension tests they were 90.8 ± 1.2 Nm/s and 88.0 ± 1.5 Nm/s. The average peak sagittal moments were 34.2 ± 0.3 Nm and 30.3 ± 0.2 Nm for flexion and 50.6 ± 0.3 Nm and 47.0 ± 0.3 Nm for extension tests. The mean peak occipital condyle angles were 23.5 ± 0.2 deg and 25.3 ± 0.1 deg for flexion and 22.7 ± 0.2 deg and 25.8 ± 0.1 deg for extension. CONCLUSION: Using the angular motion as a basis and comparing it with the previously conducted PMHS tests, the THOR-05F neck has approximately twice the stiffness of the human under sagittal plane bending.

Pelvis injury risk curves in side impacts from human cadaver experiments using survival analysis and Brier score metrics.

Objectives: Post Mortem Human Surrogate (PMHS) experiments are used for describing tolerance and improve safety. For nearside impacts, the United States Standard Federal Motor Vehicle Safety Standards (FMVSS-214) used PMHS tests and binary regression methods to achieve these goals. Since this promulgation, Parametric Statistical Survival Modeling (PSSM) has become a de facto standard for developing injury risk curves (IRCs). This study is focused on pelvic injuries from side impacts. The objectives are as follows. Analyze impactor-based intact PMHS tests and develop IRCs at different AIS levels using the force metric and examine the effectiveness of other force-related variables on IRCs.Methods: Impactor-driven pelvic tests conducted using whole body PMHS were selected from published studies. The dataset had 63 tests. Peak force, 3-ms clip force, and impulse were used to develop IRCs for Abbreviated Injury Scores (AIS) AIS2+ and AIS3+, i.e., groups A and B. Brier Score Metric (BSM) was used for ranking metrics. 95% confidence intervals were computed, Normalized Confidence Interval Sizes (NCIS) were determined, and quality of the IRCs were obtained.Results: Impulse best described the underlying response of the pelvis. BSMs were the lowest for the impulse for both groups. At 10% and 50% probabilities, impulses were 71 Ns and 125 Ns for group A and 79 Ns and 160 Ns for group B; peak forces were 3.8 kN and 7.1 kN and 4 kN and 10 kN for groups A and B; and clip forces were 2.7 kN and 6.5 kN and 3.6 kN and 8.6 kN, for groups A and B. NCIS at discrete probability levels, qualities of risk curves, and individual IRCs are given.Conclusion: This study underscores the importance of using impulse to describe pelvis injury criteria in lateral impacts. These findings are applicable to anthropomorphic test devices, as matched pair tests are done to determine dummy-based injury criteria/injury assessment risk curves (IARCs). Although IRCs have been developed for WorldSID, it may be appropriate to use impulse-based IARCs. Because THOR is a potential device for automated vehicle environments, it may be appropriate to develop THOR-based IARCS. The present IRCs act as fundamental human-based injury criteria. These responses can also be used in human body and subsystem computational models.

Anatomically-based skeletal coordinate systems for use with impact biomechanics data intended for anthropomorphic test device development.

Post-mortem human subjects (PMHS) are frequently used to characterize biomechanical response and injury tolerance of humans to various types of loading by means of instrumentation installed directly on the skeleton. Data extracted from such tests are often used to develop and validate anthropomorphic test devices (ATDs), which function as human surrogates in tests for injury assessment. Given that the location and orientation of installed instrumentation differs between subjects, nominally similar measurements made on different PMHS must be transformed to standardized, skeletal-based local coordinate systems (LCS) before appropriate data comparisons can be made. Standardized PMHS LCS that correspond to ATD instrumentation locations and orientations have not previously been published. This paper introduces anatomically-defined PMHS LCS for body regions in which kinematic measurements are made using ATDs. These LCS include the head, sternum, single vertebrae, pelvis, femurs (distal and proximal), and tibiae (distal and proximal) based upon skeletal landmarks extracted from whole body CT scans. The proposed LCS provide a means to standardize the reporting of PMHS data, and facilitate both the comparison of PMHS impact data across institutions and the application of PMHS data to the development and validation of ATDs.

Three-dimensional kinematic corridors of the head, spine, and pelvis for small female driver seat occupants in near- and far-side oblique frontal impacts.

OBJECTIVES: Analyses of recent automotive accident data indicate an increased risk of injury for small female occupants compared to males in similar accidents. Females have been shown to be more susceptible to spinal injuries than males. To protect this more vulnerable population, advanced anthropomorphic test devices (ATDs) and computer human body models are being developed and require biofidelity curves for validation. The aim of this study is to generate female-specific 3D kinematic corridors in near- and far-side oblique frontal impacts for the head, spine, and pelvis. METHODS: Eight specimens were procured and prescreened for mass, stature, and quantitative computed tomography bone mineral density and preexisting injuries to minimize biologic variability. Sets of 4 noncolinear retroreflective targets were placed on the back of the head; dorsal spine at T1, T8, and L2; and posterior sacrum. Instrumented computed tomography scans were obtained to measure the orientation and position of the markers relative to anatomic fiducials. The specimens were placed on a buck representative of a generic automotive driver's seat environment designed to minimize lower-extremity and pelvic motion. The buck was oriented such that the buck centerline was seated 30° from the impact vector in either a near- or far-side oblique frontal configuration. Preposition of the occupant was specified to the 50th percentile male H-point location, thigh and tibial angles, and torso angle. Impact was delivered via a servo-acceleration sled to the base of the buck with a 30 km/h 9 g trapezoidal pulse. Occupants were restrained by a standard 3-point belt that had a custom load-limiter device set to 2 kN at the D-ring side of the shoulder belt. Target motion was recorded at 1 kHz using a 3D optical motion capture system. Anatomic motion of the head, spine, and pelvis was calculated relative to the seat, and the average response was determined from 4 near-side and 4 far-side tests. The borders of the corridor were determined by calculating a standard deviational ellipse in the x, y, and z planes at each time step. RESULTS: Plots of the biofidelity corridors for near- and far-side tests are shown in planes parallel to the seat from the lateral, rear, and overhead directions. Averaged peak excursions in the fore/aft and lateral directions are compared for the near- and far-side corridors. Near-side female and male tests are similarly compared. CONCLUSIONS: In general, average peak excursions were greater in the far-side configuration than in the near-side configuration. Peak excursion results compared well with similar tests conducted on male postmortem human subjects (PMHS). The kinematic corridors developed in the current study serve as a set of biofidelity corridors for the development of current and future physical and computational surrogates.

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.

Responses and Injuries to PMHS in Side-Facing and Oblique Seats in Horizontal Longitudinal Sled Tests per FAA Emergency Landing Conditions.

The objective of the present exploratory study is to understand occupant responses in oblique and side-facing seats in the aviation environment, which are increasingly installed in modern aircrafts. Sled tests were conducted using intact Post Mortem Human Surrogates (PMHS) seated in custom seats approximating standard aircraft geometry. End conditions were selected to represent candidate aviation seat and restraint configurations. Three-dimensional head center-of-gravity linear accelerations, head angular velocities, and linear accelerations of the T1, T6, and T12 spinous processes, and sacrum were obtained. Three-dimensional kinematics relative to the seat were obtained from retroreflective targets attached to the head, T1, T6, T12, and sacrum. All specimens sustained spinal injuries, although variations existed by vertebral level. While the tension mechanism was associated with cervical spine injuries, complex distraction-coupled with bending and tension was attributed to thoracolumbar spine injuries. Skeletal fractures to the ribcage were attributed to compression induced by the restraint from the seatbelt, the presence of the armrest, and/or severe motions of the unconstrained torso. Pelvic injuries were also attributed to restraint offered by the lap belt on the accelerating torso-pelvis complex in the absence of the armrest. Lower extremity injuries occurred due to the unconstrained motion (flailing mechanism). These results serve as an initial dataset to understand the kinematics of different body regions, injuries and patterns, and potential injury mechanisms describing PMHS responses in the aviation environment.

Evaluation of kinematics and injuries to restrained occupants in far-side crashes using full-scale vehicle and human body models.

OBJECTIVE: The objective of the current study was to perform a parametric study with different impact objects, impact locations, and impact speeds by analyzing occupant kinematics and injury estimations using a whole-vehicle and whole-body finite element-human body model (FE-HBM). To confirm the HBM responses, the biofidelity of the model was validated using data from postmortem human surrogate (PMHS) sled tests. METHODS: The biofidelity of the model was validated using data from sled experiments and correlational analysis (CORA). Full-scale simulations were performed using a restrained Global Human Body Model Consortium (GHBMC) model seated on a 2001 Ford Taurus model using a far-side lateral impact condition. The driver seat was placed in the center position to represent a nominal initial impact condition. A 3-point seat belt with pretensioner and retractor was used to restrain the GHBMC model. A parametric study was performed using 12 simulations by varying impact locations, impacting object, and impact speed using the full-scale models. In all 12 simulations, the principal direction of force (PDOF) was selected as 90°. The impacting objects were a 10-in.-diameter rigid vertical pole and a movable deformable barrier. The impact location of the pole was at the C-pillar in the first case, at the B-pillar in the second case, and, finally, at the A-pillar in the third case. The vehicle and the GHBMC models were defined an initial velocity of 35 km/h (high speed) and 15 km/h (low speed). Excursion of the head center of gravity (CG), T6, and pelvis were measured from the simulations. In addition, injury risk estimations were performed on head, rib cage, lungs, kidneys, liver, spleen, and pelvis. RESULTS: The average CORA rating was 0.7. The shoulder belt slipped in B- and C-pillar impacts but somewhat engaged in the A-pillar case. In the B-pillar case, the head contacted the intruding struck-side structures, indicating higher risk of injury. Occupant kinematics depended on interaction with restraints and internal structures-especially the passenger seat. Risk analysis indicated that the head had the highest risk of sustaining an injury in the B-pillar case compared to the other 2 cases. Higher lap belt load (3.4 kN) may correspond to the Abbreviated Injury Scale (AIS) 2 pelvic injury observed in the B-pillar case. Risk of injury to other soft anatomical structures varied with impact configuration and restraint interaction. CONCLUSION: The average CORA rating was 0.7. In general, the results indicated that the high-speed impacts against the pole resulted in severe injuries, higher excursions followed by low-speed pole, high-speed moving deformable barrier (MDB), and low-speed MDB impacts. The vehicle and occupant kinematics varied with different impact setups and the latter kinematics were likely influenced by restraint effectiveness. Increased restraint engagement increased the injury risk to the corresponding anatomic structure, whereas ineffective restraint engagement increased the occupant excursion, resulting in a direct impact to the struck-side interior structures.

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.

Cervical spine injuries, mechanisms, stability and AIS scores from vertical loading applied to military environments.

PURPOSE: The purpose of this study was to determine injuries to osteo-ligamentous structures of cervical column, mechanisms, forces, severities and AIS scores from vertical accelerative loading. METHODS: Seven human cadaver head-neck complexes (56.9 ± 9.5 years) were aligned based on seated the posture of military soldiers. Army combat helmets were used. Specimens were attached to a vertical accelerator to apply caudo-cephalad g-forces. They were accelerated with increasing insults. Intermittent palpation and radiography were done. A roof structure mimicking military vehicle interior was introduced after a series of tests and experiments were conducted following similar protocols. Upon injury detection, CT and dissection were done. Temporal force responses were extracted, peak forces and times of occurrence were obtained, injury severities were graded, and spine stability was determined. RESULTS: Injuries occurred in tests only when the roof structure was included. Responses were tri-phasic: initial thrust, secondary tensile, tertiary roof contact phases. Peak forces: 1364-4382 N, initial thrust, 165-169 N, secondary tensile, 868-3368 N tertiary helmet-head roof contact phases. Times of attainments: 5.3-9.6, 31.7-42.6, 55.0-70.8 ms. Injuries included fractures and joint disruptions. Multiple injuries occurred in all but one specimen. A majority of injury severities were AIS = 2. Spines were considered unstable in a majority of cases. CONCLUSIONS: Spine response was tri-phasic. Injuries occurred in roof contact tests with the helmeted head-neck specimen. Multiplicity and unstable nature of AIS = 2 level injuries, albeit at lower severities, might predispose the spine to long-term accelerated degenerative changes. Clinical protocols should include a careful evaluation of sub-catastrophic injuries in military patients.

Oblique Loading in Post Mortem Human Surrogates from Vehicle Lateral Impact Tests using Chestbands.

While numerous studies have been conducted to determine side impact responses of Post Mortem Human Surrogates (PMHS) using sled and other equipment, experiments using the biological surrogate in modern full-scale vehicles are not available. The present study investigated the presence of oblique loading in moving deformable barrier and pole tests. Threepoint belt restrained PMHS were positioned in the left front and left rear seats in the former and left front seat in the latter condition and tested according to consumer testing protocols. Three chestbands were used in each specimen (upper, middle and lower thorax). Accelerometers were secured to the skull, shoulder, upper, middle and lower thoracic vertebrae, sternum, and sacrum. Chestband signals were processed to determine magnitudes and angulations of peak deflections. The magnitude and timing of various signal peaks are given. Vehicle accelerations, door velocities, and seat belt loads are also given. Analysis of deformation contours, peak deflections, and angulations indicated that the left rear seated specimen were exposed to anterior oblique loading while left front specimens in both tests sustained essentially pure lateral loading to the torso. These data can be used to validate human body computational models. The occurrence of oblique loading in full-scale testing, hitherto unrecognized, may serve to stimulate the exploration of its role in injuries to the thorax and lower extremities in modern vehicles. It may be important to continue research in this area because injury metrics have a lower threshold for angled loading.

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.

Vertical accelerator device to apply loads simulating blast environments in the military to human surrogates.

The objective of the study was to develop a simple device, Vertical accelerator (Vertac), to apply vertical impact loads to Post Mortem Human Subject (PMHS) or dummy surrogates because injuries sustained in military conflicts are associated with this vector; example, under-body blasts from explosive devices/events. The two-part mechanically controlled device consisted of load-application and load-receiving sections connected by a lever arm. The former section incorporated a falling weight to impact one end of the lever arm inducing a reaction at the other/load-receiving end. The "launch-plate" on this end of the arm applied the vertical impact load/acceleration pulse under different initial conditions to biological/physical surrogates, attached to second section. It is possible to induce different acceleration pulses by using varying energy absorbing materials and controlling drop height and weight. The second section of Vertac had the flexibility to accommodate different body regions for vertical loading experiments. The device is simple and inexpensive. It has the ability to control pulses and flexibility to accommodate different sub-systems/components of human surrogates. It has the capability to incorporate preloads and military personal protective equipment (e.g., combat helmet). It can simulate vehicle roofs. The device allows for intermittent specimen evaluations (x-ray and palpation, without changing specimen alignment). The two free but interconnected sections can be used to advance safety to military personnel. Examples demonstrating feasibilities of the Vertac device to apply vertical impact accelerations using PMHS head-neck preparations with helmet and booted Hybrid III dummy lower leg preparations under in-contact and launch-type impact experiments are presented.

Force corridors of post mortem human surrogates in oblique side impacts from sled tests.

To develop region-specific force corridors in side impacts under oblique loadings using post mortem human surrogates (PMHS). Unembalmed PMHS were positioned on a sled. Surrogates contacted a segmented, modular/ scalable load-wall to isolate region-specific forces (shoulder, thorax, abdomen, pelvis). Heights and widths of segmented load-wall plates were adjustable in sagittal and coronal planes to accommodate anthropometry variations. Load cells were used to gather region-specific forces. Tests were conducted at 6.7 m/s. Peak forces and times of attainments, and standard corridors (mean ± 1 SD) are given for the four torso regions and summated forces. The mean age, stature, and total body mass of the five male PMHS were: 56.6 ± 4.4 years, 183 ± 3.5 cm and 70.6 ± 9.0 kg. Peak pelvis forces were the greatest, followed by thorax, abdomen and shoulder. Sequence of times of attainments of peak forces initiating from pelvis increased rostrally to abdomen to thorax and shoulder regions. Corridors were tight in all regions, except shoulder. As previous force corridors were based solely on pure-lateral impacts and region-specific forces were not extracted, the present oblique responses using anthropometry-specific load-wall design can be used to develop injury criteria and evaluate the biofidelity of dummies.

Determination of peak deflections from human surrogates using chestbands in side impact tests.

To understand the biomechanics of the human body in motor vehicle environments, physical models including anthropomorphic test devices (ATD) and biological models (postmortem human surrogates) are used, and sled tests are conducted. Deflection is often used as a biomechanical variable to characterize the effects of impact loading and derive injury criteria. The objective of the present study was to evaluate different techniques and recommend a methodology to determine the peak thorax and abdominal deflections from temporal contours using chestbands in oblique lateral impacts. The side impact ATD WorldSID representing human surrogates was positioned on a seat. The seat was rigidly fixed to the platform of an acceleration sled. The oblique load-wall fixed to the sled consisted of separate and adjustable plates to contact the shoulder, thorax, abdomen, and pelvis. Two 59-gage chestbands were wrapped on the thorax and abdomen. Tests were conducted at low, medium, and high velocities (3.4, 6.7, and 7.5m/s) and three methods, termed the spine-sternum, bilateral, and spine-box, were used to determine the global peak deflection and its angulation. Results indicated that all three methods produced very similar angulations, for all velocity tests, and at both thorax and abdominal regions. However, maximum deflections were the lowest in the spine-sternum, followed by bilateral and spine-box methods, with one exception. Based on the development of deflection contours, locations used in the definitions of the origin, and accuracy in identifying critical locations/points in time-varying contours, results of the present study indicate that the bilateral method is the optimum procedure to determine the oblique peak deflection vector in biomechanical tests.

Comparison of AIS 1990 update 98 versus AIS 2005 for describing PMHS injuries in lateral and oblique sled tests.

This study analyzed skeletal and organ injuries in pure lateral and oblique impacts from 20 intact post mortem human surrogate (PMHS) sled tests at 6.7 m/s. Injuries to the shoulder, thorax, abdomen, pelvis and spine were scored using AIS 1990-1998 update and 2005. The Injury Severity Scores (ISS) were extracted for both loadings from both versions. Mean age, stature, total body mass and body mass index for pure lateral and oblique tests: 58 and 55 years, 1.7 and 1.8 m, 69 and 66 kg, and 24 and 21 kg/m(2). Skeletal injuries (ribs, sternum) occurred in both impacts. However, oblique impacts resulted in more injuries. Pure lateral and oblique impacts ISS: 0 to 16 and 0 to 24, representing a greater potential for injury-related consequences in real-world situations in oblique impacts. Internal organs were more involved in oblique impacts. ISS decreased in AIS 2005, reflecting changes to scoring and drawing attention to potential effects for pre-hospital care/medical aspects. Mean AIS scores for the two load vectors and two AIS coding schemes are included. From automotive crashworthiness perspectives, decreases in injury severities might alter injury risk functions with a shift to lower metrics for the same risk level than current risk estimations. This finding influences dummy-based injury criteria and occupant safety as risk functions are used for countermeasure effectiveness and cost-benefit analyses by regulatory bodies. Increase in organ injuries in oblique loading indicate the importance of this vector as current dummies and injury criteria used in regulations are based on pure lateral impact data.

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.