Global Human Body Models Consortium Research Articles

Developing Rib Bone Surrogates for High Dynamic Impact Assessment with Additive Manufacturing and Post-mortem Human Subjects (PMHS)-Based Evaluation

The conception of ballistic personal protective equipment requires a comprehensive understanding of the human body’s response to dynamic loads. The objective of this study is to develop rib bone surrogates enhancing new anthropomorphic test devices for personal protective equipment evaluation at high dynamic impacts. These are fabricated with additive manufacturing and compared to post-mortem human subjects (PMHS) data from literature. The 5th rib of the finite element Global Human Body Model Consortium (GHBMC) male 50th percentile (M50) model was extracted and transferred to a CAD model. This CAD model was divided into 30 sections with specific cortical bone thicknesses in all directions (caudal, cranial, cutaneous and pleural) from an equivalent rib of an M50 PMHS. Three different additive manufacturing technologies (direct metal laser melting, fused filament fabrication and multi jet modeling) were used to reproduce the M50 PMHS 5th rib surrogate. A total of 57 specimens were dynamically (500 mm/s) loaded to failure in a bending scenario imitating a frontal thoracic impact. Force, displacement, stiffness, and energy at failure were determined. Also, the strain distribution using 3D digital image correlation was recorded and compared to PMHS data from literature. The rib surrogates show deviations from the PMHS characteristic values. Nevertheless, there are also common characteristics in key variables to certain age groups of the PMHS data, which will facilitate the further development and improvement of adequate surrogates for a more realistic representation of the human body’s response to high dynamic loads.

Biomechanical Response of Head Surrogate With and Without the Helmet.

Measurements of brain deformations under injurious loading scenarios are actively sought. In this work, we report experimentally measured head kinematics and corresponding dynamic, two-dimensional brain simulant deformations in head surrogates under a blunt impact, with and without a helmet. Head surrogates used in this work consisted of skin, skull, dura, falx, tentorium, and brain stimulants. The head surrogate geometry was based on the global human body models consortium's head model. A base head surrogate consisting of skin-skull-brain was considered. In addition, the response of two other head surrogates, skin-skull-dura-brain, and skin-skull-dura-brain-falx-tentorium, was investigated. Head surrogate response was studied for sagittal and coronal plane rotations for impactor velocities of 1 and 3 m/s. Response of head surrogates was compared against strain measurements in PMHS. The strain pattern in the brain simulant was heterogenous, and peak strains were established within ∼30 ms. The choice of head surrogate affect the spatiotemporal evolution of strain. For no helmet case, peak MPS of ∼50-60% and peak MSS of ∼35-50% were seen in brain simulant corresponding to peak rotational accelerations of ∼5000-7000 rad/s2. Peak head kinematics and peak MPS have been reduced by up to 75% and 45%, respectively, with the conventional helmet and by up to 90% and 85%, respectively, with the helmet with antirotational pads. Overall, these results provide important, new data on brain simulant strains under a variety of loading scenarios-with and without the helmets.

Bridging the Gap: Development of frontal crash mode ATD Analogous human body models

Anthropomorphic variation is an important factor in computational studies using Human Body Models (HBMs), particularly regarding how such differences can influence observed kinematics and loading. Currently, a gap exists between Anthropomorphic Test Devices (ATDs) and human body models (HBMs). By necessity, there are differences in constitutive behaviors at a material level, however segment mass distribution and anthropometry differences can make matched simulations of ATDs and HBMs difficult to interpret, which has real-world implications for current or future regulatory applications. In response to this gap, we present Global Human Body Model Consortium (GHBMC) 50th percentile male models (M50-OS) analogous to Hybrid III and THOR 50th percentile male models to serve as intermediaries between the HBMs and ATDs in computational biomechanics studies.Statistical human shape models were sized to each ATD, individually, using measurement metrics from ANSUR I. The M50-OS model surface and body shape surface were then converted to both polygon data (STL) and nodal coordinates. Landmark registration was performed, and the morphed nodes were imported back into the existing M50-OS models to generate two morphed versions analogous to the ATDs. The qualification suites were obtained from each respective ATD manual and run against the baseline and morphed models. The models were also simulated in a frontal NCAP crash pulses (56 km/hr) to assess variation in loading in a regulatory crash environment. 33 simulations were run between all models. The LSTC Hybrid III version 151,214 (open access software, ANSYS, Canonsburg, PA), Adult Shape Parametric Model (open access model, UMTRI, Ann Arbor, MI), GHBMC M50-OS (Elemance, LLC, Winston-Salem, NC), Thor v2.7 (University of Virginia School of Engineering and Applied Science/NHTSA) were used in this study. All simulations were run using LS-Dyna R. 9.3.1 (ANSYS) on an in-house computational cluster.The Male 50th Percentile THOR Analogous Occupant Simplified (M50 THAN-OS) has 364 × 103 elements and weighs 77.1 kg, the Hybrid III Analogous Occupant Simplified (M50 HAN-OS) has 370 × 103 elements and weighs 79.2 kg. The M50 HAN-OS and M50 THAN-OS response data exhibited a closer match to their respective models overall when compared to the baseline M50-OS human. In the vehicle test environment, the airbag and seatbelt peaks between M50 HAN-OS and M50 Hybrid III at nearly the same time.The results indicate that the ATD analogous models exhibit more similar response characteristics to their ATD counterparts after correcting for shape and mass distribution discrepancies. The ATD analogous models therefore represent a novel means to compare anticipated biomechanical loading on an occupant under similar testing conditions that use ATDs. Furthermore, the models represent a potential bridge towards testing modes of interest that ATDs are not well suited or are not validated for, such as low speed maneuvering, or oblique and far-side modes of crash.

Effect of Torso Boundary Conditions on Spine Kinematic and Injury Responses in Head-First Impact Assessed with a 50th Percentile Male Human Body Model

<div>Computational and experimental studies have been undertaken to investigate injurious head-first impacts (HFI), which can occur during automotive rollovers. Recent studies assume a torso surrogate mass (TSM) boundary condition, wherein the first or first two thoracic vertebrae are potted and constrained to only move in the vertical loading direction. The TSM boundary condition has not been compared with a full body (FB) model computationally or experimentally for HFI. In this study, the Global Human Body Models Consortium 50th percentile male detailed human body model (M50-O, Version 6.0) was applied to compare the kinematic, kinetic, and injury response of an HFI with a TSM boundary condition (M50-TSM), and a full body boundary condition (M50-FB). Impacts (to M50-TSM and M50-FB) were simulated between the head and a rigid plate using a commercial FE code (LS-DYNA). The impact velocity of 3.1 m/s corresponded to the onset of spinal injury in diving reconstructions, and the impact velocity reported in experiments. The TSM boundary condition was simulated by applying a mass of 16 kg to the first thoracic vertebra (T1), and constraining motion to only the vertical direction. A quantitative comparison of the head and spine impact forces, spine kinematics, and prediction of hard tissue fracture was reported. The M50-TSM model demonstrated a 53.4% lower (straighter) spinal curvature 10 ms after impact, compared to the M50-FB. The lower curvature of the M50-TSM resulted in higher neck loads during that timeframe (2.26 kN M50-TSM, 1.44 kN M50-FB). The resulting hard tissue fracture in M50-TSM was attributed to direct compression at an early time (<5 ms) in the impact, while M50-FB demonstrated compression-extension fractures later (>16 ms) in the simulation. It was concluded that kinematics, kinetics, and injury response differed for the TSM and FB boundary conditions, and therefore these conditions are critical to consider when investigating HFI.</div>

Preliminary validation of the GHBMC average male occupant models and 70YO aged model in far-side impact

The objective of the current study was to perform a preliminary validation of the Global Human Body Models Consortium (GHBMC) average male occupant models, simplified (M50-OS) and detailed (M50-O) and the 70YO aged model in Far-side impacts and compare the head kinematics against the PMHS responses published by Petit et al. (2019). The buck used to simulate the far-side impacts comprised a seat, headrest, center console plate, leg support plate, and footrest plate with rigid material properties.The three occupant models were gravity settled onto the rigid seat and belted with a 3-point seatbelt. Positioning details of the PMHS were followed in the model setup process. A deceleration pulse with ΔV of 8 m/s was applied. The far-side crash simulations were performed with and without the addition of a plexiglass cover around the setup similar to the experimental setup. The head kinematics were extracted from the models for comparison against the PMHS data. Peak head displacements in Y and Z axes from the three models were compared to the PMHS data in addition to the head rotation along X axes. The peak head displacement values for the M50-OS, M50-O, and M50-O 70YO aged models are 594.10 mm, 568.44 mm, and 567.90 mm along Y and 325.21 mm, 402.66 mm, and 375.92 mm respectively along Z when the plexiglass cover is included in the test. The peak head rotation values for the M50-OS, M50-O, and M50-O 70YO aged models are 95.64°, 122.15°, and 129.08° respectively when the plexiglass cover is included in the test. The three occupant models capture the general trend of the PMHS data. The detailed occupant models have higher head rotation compared to the simplified model because of the deformable structure of the spine and intervertebral discs modeled. These three occupant models can be used for further parametric studies in this condition to study the influence of restraint parameters.

Assessment of finite element human body and ATD models in estimating injury risk in far-side impacts using field-based injury risk

The objective of this study was to assess the ability of finite element human body models (FEHBMs) and Anthropometric Test Device (ATD) models to estimate occupant injury risk by comparing it with field-based injury risk in far-side impacts. The study used the Global Human Body Models Consortium midsize male (M50-OS+B) and small female (F05-OS+B) simplified occupant models with a modular detailed brain, and the ES-2Re and SID-IIs ATD models in the simulated far-side crashes. A design of experiments (DOE) with a total of 252 simulations was conducted by varying lateral ΔV (10-50kph; 5kph increments), the principal direction of force (PDOF 50°, 60°, 65°, 70°, 75°, 80°, 90°), and occupant models. Models were gravity-settled and belted into a simplified vehicle model (SVM) modified for far-side impact simulations. Acceleration pulses and vehicle intrusion profiles used for the DOE were generated by impacting a 2012 Camry vehicle model with a mobile deformable barrier model across the 7 PDOFs and 9 lateral ΔV’s in the DOE for a total of 63 additional simulations. Injury risks were estimated for the head, chest, lower extremity, pelvis (AIS 2+; AIS 3+), and abdomen (AIS 3+) using logistic regression models. Combined AIS 3+ injury risk for each occupant was calculated using AIS 3+ injury risk estimations for the head, chest, abdomen, and lower extremities. The injury risk calculated using computational models was compared with field-based injury risk derived from NASS-CDS by calculating their correlation coefficient. The field-based injury risk was calculated using risk curves that were created based on real-world crash data in a previous study (Hostetler et al., 2020). Occupant age (40 years), seatbelt use (belted occupant), collision deformation classification, lateral ΔV, and PDOF of the crash event were used in these curves to estimate field injury risk. Large differences in the kinematics were observed between HBM and ATD models. ATD models tended to overestimate risk in almost every case whereas HBMs yielded better risk estimates overall. Chest and lower extremity risks were the least correlated with field injury risk estimates. The overall risk of AIS 3+ injury risk was the strongest comparison to the field data-based risk curves. The HBMs were still not able to capture all the variance but future studies can be carried out that are focused on investigating their shortfalls and improving them to estimate injury risk closer to field injury risk in far-side crashes.

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.

Development and preliminary validation of computationally efficient and detailed 50th percentile female human body models

ObjectiveNo vehicle testing standard (physical or computational) employs a mid-sized female human surrogate, despite discrepancies related to injury outcomes for female occupants amongst all vehicle users. We detail the design and preliminary validation of 50th percentile female (F50) computational human body models (HBMs) based on Global Human Body Models Consortium (GHBMC) models. MethodData for the target geometry was collected as part of the initial generation of GHBMC models. Imaging, surface data, and 15 anthropomorphic measures from a living female subject (60.8 kg and 1.61 m) served as the baseline for model development. Due to the role rib cage geometry plays in biomechanical loading, rib cage morphology from secondary retrospective data was leveraged to identify an average female rib cage based on gross anatomical features. A female rib cage was selected from an existing dataset closest to the mean depth, height, and width of the set, considering only those aged 20 – 50 years. The selected subject among this secondary set also exhibited a 7th rib angle and sternum angle within 5% of the mean measurements, and within the range of previously reported studies. The GHBMC 5th percentile, small female detailed (high biofidelity) and simplified (computationally efficient) models were morphed to match the F50 subject body surface, selected bones, and mean rib cage using established thin plate spline techniques. The models were validated vs. previously published literature studies with an emphasis on rib cage response. Model data was compared to 47 channels of experimental data across four biomechanical hub simulations, two sled test simulations (one of which included all female PMHS), and two robustness simulations to test stability. Model results were mass scaled to the average of the reported corridors. Objective evaluation was conducted using CORA.IRB approval was obtained for all prospective and retrospective data collected or used. The target rib cage was selected from retrospective image data used in prior studies (n = 339 chest CT scans). ResultsThe morphed HBMs closely matched the target geometry. The detailed and simplified models had masses and element counts of 61.2 kg and 61.8 kg, and 2.8 million and 0.3 million, respectively. The mass difference is due to a coarser mesh in the simplified model. The simplified model ran 23 times faster than the detailed model on the same hardware. Each model exhibited stability in robustness tests, and the average CORA scores were 0.80 and 0.72 in the detailed and simplified models, respectively. The models performed well in frontal impacts against PMHS corridors after mass scaling. ConclusionsNumerous recent studies underscore poorer injury outcomes for female vehicle occupants compared to males. While such outcomes are multifactorial, the average female models introduced in this work offer a novel tool within a widely used family of HBMs to reduce the outcome gap in terms of injury for all drivers. HBMs can be deployed in safety studies or in future regulatory requirements faster and more economically than a resized or newly designed ATDs aimed at the same target population.

Lower Extremity Validation of a Human Body Model for High Rate Axial Loading in the Underbody Blast Environment.

While the use of Human Body Models (HBMs) in the underbody blast (UBB) environment has increased and shown positive results, the potential of these models has not been fully explored. Obtaining accurate kinematic and kinetic response are necessary to better understand the injury mechanisms for military safety applications. The objective of this study was to validate the Global Human Body Models Consortium (GHBMC) M50 lower extremity using a combined objective rating scheme in vertical and horizontal high-rate axial loading. The model's lower extremity biomechanical response was compared to Post Mortem Human Subjects (PMHS) subjects for vertically and horizontally-applied high rate axial loading. Two distinct experimental setups were used for model validation, comprising a total of 33 distinct end points for validation. A combined Correlation and Analysis (CORA) score that incorporates CORA, time-to-peak (TTP) and peak magnitude of the experimental signals and ISO TS 18571 was used to evaluate the model response. For the horizontal impacts, the combined CORA scores were 0.80, 0.84, and 0.81 for compression, force, and strain respectively. For the vertical impacts combined CORA scores for the knee Z force, compression and heel Z displacement ranged from 0.70-0.81, 0.87-0.91, and 0.82-0.99 respectively. The GHBMC lower extremity model showed good agreement with PMHS experimental data in the horizontal and vertical loading environment in 33 unique tests. The accuracy is demonstrated by using the ISO TS 18571 standard and a combined CORA score that takes into consideration the peak and time to peak of the signal. The results of this study show that GHBMC v 6.0 HBM lower extremity can be used for kinetic and kinematic predictions in the UBB environment.

Combining protective clothes with human body models for finite element ballistic impact simulations

The ballistic deformation of an ultra-high-molecular-weight (UHMW) polyethylene (PE) composite has been subjected numerically to a multi-layered soft ballistic fabric package modelled upon the body contours of the Global Human Body Models Consortium (GHBMC) human body models M50-P and F05-P. The results of the clothing-body-interaction have been investigated and compared to the behavior of anthropomorphic surrogate models made from ballistic clay. For building the fabric model in donned shape, a single ply of woven fabric material has been converted upon the anthropomorphic body contour by subjecting it to a quasi-deep drawing process. After the fabric deformation, the shaped layer was duplicated 20 times and shifted outwards to build the fabric model, representing a multi-layered soft ballistic fabric package. The results of the ballistic impact simulation show that the response of the human body models (HBMs) is much more compliant than the behavior of the surrogate models. The deformation of the female HBM in terms of penetration depth and diameter of the affected impact region is slightly more severe than the deformation of the male counterpart with respect to identical impact conditions.

Response of small female and midsize male models with active musculature in pre-crash maneuvers and low-speed impacts

Objective The objectives of this study were to evaluate computationally efficient small female (54.1 kg, 149.9 cm) and midsize male (78.4 kg, 174.9 cm) models with active muscles using volunteer sled test data in a frontal-oblique loading direction and check their response in crash mitigating maneuvers using field test data. Methods The Global Human Body Models Consortium small female (F05-OS+Active) and midsize male (M50-OS+Active) simplified occupant models with active musculature were used in this study. The data from a total of 48 previously published sled test experiments were used to simulate a total of 16 simulations. The experimental study recorded occupant responses of six small female and six midsize male volunteers (n = 12 total) in two muscle conditions (relaxed and braced) at two acceleration pulses representing pre-crash braking (1.0 g) and a low-speed impact (2.5 g). Each model’s kinematics and reaction forces were compared with experimental data. Along with sled test simulations, both of these models were simulated in abrupt braking, lane change, and turn and brake events using literature data. A total of 36 field test simulations were carried out. A CORA analysis was carried out using reaction load and displacement time-history data for sled test simulations and head CG displacement time-history was used for field test simulations. Results The occupant peak forward and lateral excursion results of both active models reasonably matched the volunteer data in the low-speed sled test simulations for both pulse severities. The differences between the active and control models were statistically significant (p-value < 0.05) based on the results of Wilcoxon signed-rank tests using peak forward and lateral excursion data. The average CORA scores calculated for the sled test (sled test: M50-OS+Active= 0.543, male control= 0.471, F05-OS+Active= 0.621, female control= 0.505) and field test (M50-OS+Active= 0.836, male control= 0.466, F05-OS+Active= 0.832, female control= 0.787) simulations were higher for active models than control. Conclusions The responses of the F05-OS+Active and M50-OS+Active models were better than control models based on overall CORA scores calculated using both sled and field tests. The results highlight their ability to predict occupant kinematics in crash-mitigating maneuvers and low-speed impacts in the frontal, lateral and frontal-oblique directions.

Modular incorporation of deformable spine and 3D neck musculature into a simplified human body finite element model

Spinal injuries are a concern for automotive applications, requiring large parametric studies to understand spinal injury mechanisms under complex loading conditions. Finite element computational human body models (e.g. Global Human Body Models Consortium (GHBMC) models) can be used to identify spinal injury mechanisms. However, the existing GHBMC detailed models (with high computational time) or GHBMC simplified models (lacking vertebral fracture prediction capabilities) are not ideal for studying spinal injury mechanisms in large parametric studies. To overcome these limitations, a modular 50th percentile male simplified occupant model combining advantages of both the simplified and detailed models, M50-OS + DeformSpine, was developed by incorporating the deformable spine and 3D neck musculature from the detailed GHBMC model M50-O (v6.0) into the simplified GHBMC model M50-OS (v2.3). This new modular model was validated against post-mortem human subject test data in four rigid hub impactor tests and two frontal impact sled tests. The M50-OS + DeformSpine model showed good agreement with experimental test data with an average CORrelation and Analysis (CORA) score of 0.82 for the hub impact tests and 0.75 for the sled impact tests. CORA scores were statistically similar overall between the M50-OS + DeformSpine (0.79 ± 0.11), M50-OS (0.79 ± 0.11), and M50-O (0.82 ± 0.11) models (p > 0.05). This new model is computationally 6 times faster than the detailed M50-O model, with added spinal injury prediction capabilities over the simplified M50-OS model.

A simulation-based study for optimizing proportional-integral-derivative controller gains for different control strategies of an active upper extremity model using experimental data

This study investigates the effect of PID controller gains, reaction time, and initial muscle activation values on active human model behavior while comparing three different control strategies. The controller gains and reaction delays were optimized using published experimental data focused on the upper extremity. The data describes the reaction of five male subjects in four tests based on two muscle states (relaxed and tensed) and two states of awareness (open and closed eye). The study used a finite element model of the left arm isolated from the Global Human Body Models Consortium (GHBMC) average male simplified occupant model for simulating biomechanical simulations. Major skeletal muscles of the arm were modeled as 1D beam elements and assigned a Hill-type muscle material. Angular position control, muscle length control, and a combination of both were used as a control strategy. The optimization process was limited to 4 variables; three Proportional-Integral-Derivative (PID) controller gains and one reaction delay time. The study assumed the relaxed and tensed condition require distinct sets of controller gains and initial activation and that the closed-eye simulations can be achieved by increasing the reaction delay parameter. A post-hoc linear combination of angle and muscle length control was used to arrive at the final combined control strategy. The premise was supported by variation in the controller gains depending on muscle state and an increase in reaction delay based on awareness. The CORA scores for open-eye relaxed, closed-eye relaxed, open-eye tensed, and closed-eye tensed was 0.95, 0.90, 0.95, and 0.77, respectively using the combined control strategy.

Development and Validation of an Active Muscle Simplified Finite Element Human Body Model in a Standing Posture.

Active muscles play an important role in postural stabilization, and muscle-induced joint stiffening can alter the kinematic response of the human body, particularly that of the lower extremities, under dynamic loading conditions. There are few full-body human body finite element models with active muscles in a standing posture. Thus, the objective of this study was to develop and validate the M50-PS+Active model, an average-male simplified human body model in a standing posture with active musculature. The M50-PS+Active model was developed by incorporating 116 skeletal muscles, as one-dimensional beam elements with a Hill-type material model and closed-loop Proportional Integral Derivative (PID) controller muscle activation strategy, into the Global Human Body Models Consortium (GHBMC) simplified pedestrian model M50-PS. The M50-PS+Active model was first validated in a gravity standing test, showing the effectiveness of the active muscles in maintaining a standing posture under gravitational loading. The knee kinematics of the model were compared against volunteer kinematics in unsuited and suited step-down tests from NASA's active response gravity offload system (ARGOS) laboratory. The M50-PS+Active model showed good biofidelity with volunteer kinematics with an overall CORA score of 0.80, as compared to 0.64 (fair) in the passive M50-PS model. The M50-PS+Active model will serve as a useful tool to study the biomechanics of the human body in vehicle-pedestrian accidents, public transportation braking, and space missions piloted in a standing posture.

A validated lower extremity model to investigate the effect of stabilizing knee components in pedestrian collisions.

Lower extremity injuries account for over 50% of pedestrian orthopedic injuries in car-to-pedestrian collisions. Pedestrian finite element models are useful tools for studying pedestrian safety, but current models use simplified knee models that exclude potentially important stabilizing knee components. The effect of these stabilizing components in pedestrian impacts is currently unknown. The goal of this study was to develop a detailed lower-extremity model to investigate the effect of these stabilizing components on pedestrian biomechanics. In this study the Global Human Body Model Consortium male 50th percentile pedestrian model lower body was updated to include various stabilizing knee components, enhance geometric anatomical accuracy of previously modeled soft tissue structures, and update hard and soft tissue material models. The original and updated models were compared across 13 validation tests and the updated model reported significantly (p = 0.01) larger CORA scores (0.73 ± 0.15) than the original model (0.56 ± 0.20). To investigate the effect of the new stabilizing knee components the updated model had its stabilizing components severed. The severed and intact models were impacted by the EuroNCAP SUV and family car models at 30 and 40 km/h. The intact and severed models reported nearly identical head impact times, wrap around distances, and lower-extremity injury outcomes in all four impacts, but the stabilizing components reduced the varus knee angle of the secondarily impacted leg by up to 4.9°. The stabilizing components may prevent secondary impacted leg injuries in lower intensity impacts but overall had little effect on pedestrian biomechanical outcomes.

Computational Assessment of Positional Sensitivity to Injury in Spacecraft Occupants

Spacecraft occupants are susceptible to injury from sudden loads, such as those experienced during landing. Most injury biomechanics investigations assume perfect seated posture and consistent seated position. However, this assumption is unrealistic, as offsets from these presumed postures and placements are likely during impacts. In this computational study, the Global Human Body Model Consortium’s simplified 5thpercentile female and 50th and 95th-percentile male anthropometric models were seated and restrained in three positions: nominal, (“perfect” posture and placement); and 10 millimeters and 25.4 millimeters forward of the seatback. Biodynamic responses to simulations involving vertical accelerations were analyzed for positional sensitivity. The 5th-percentile female was most susceptible to neck injury due to compressive forces. In 50th and 95th-percentile males, upper spinal intervertebral forces were positively correlated to seated position (increasing 13% for 25.4mm forward offset). Analysis of head excursions and knee splay data indicates potential whiplash and the need for conformal seating, respectively.

Implementation and calibration of active small female and average male human body models using low-speed frontal sled tests

Objective The objective of this study was to implement active muscles in a computationally efficient small female finite element model (54.1 kg, 149.9 cm) suitable for predicting occupant response during precrash braking and low-speed frontal sled tests. We further calibrate and compare its results against an average male model (78.4 kg, 174.9 cm) using the same developmental approach. Methods The active female model (F05-OS + Active) was developed by adding active skeletal muscle elements (n = 232) to the Global Human Body Models Consortium (GHBMC) 5th percentile female simplified occupant model (F05-OS v2.3). The muscle properties and physiological cross-sectional area (PCSA) for each muscle were taken from the M50-OS + Active v2.3 model but PCSAs were mass scaled to a 5th percentile female. A total of 8 simulations were conducted; 2 acceleration pulses (1.0 g and 2.5 g), 2 models (F05-OS + Active and M50-OS + Active), and 2 muscle states (activation and control; e.g., no activation). Each model’s kinematics and reaction forces were compared with experimental data. Occupant responses of 6 5th percentile female and 6 50th percentile male volunteers (n = 12 total) were used. The data depict occupant response in precrash braking and low-speed frontal sled tests in a rigid test buck. All procedures were reviewed and approved by the Virginia Tech institutional review board. Each volunteer was in a relaxed state before the applied acceleration. Results The occupant peak forward excursion results of both active models reasonably match the volunteer data for both pulse severities. The differences between active and control models were found to be significant by Wilcoxon signed-rank test (p < .05). The reaction loads of the active and control models lie within the experimental corridors. Conclusions To the authors’ knowledge, this study is the first to concurrently calibrate and compare equivalently developed computational models of females and males in precrash and low-speed impacts. The modeling approach is capable of capturing the varied kinematics observed in the relaxed condition, which may be an important factor in studies focused on the effects of low-g vehicle dynamics on the occupant position. Finally, the computationally efficient modeling approach is imperative given the long duration (>500 ms) of the events simulated.

Assessment of brain injury characterization and influence of modeling approaches

In this study, using computational biomechanics models, we investigated influence of the skull-brain interface modeling approach and the material property of cerebrum on the kinetic, kinematic and injury outputs. Live animal head impact tests of different severities were reconstructed in finite element simulations and DAI and ASDH injury results were compared. We used the head/brain models of Total HUman Model for Safety (THUMS) and Global Human Body Models Consortium (GHBMC), which had been validated under several loading conditions. Four modeling approaches of the skull-brain interface in the head/brain models were evaluated. They were the original models from THUMS and GHBMC, the THUMS model with skull-brain interface changed to sliding contact, and the THUMS model with increased shear modulus of cerebrum, respectively. The results have shown that the definition of skull-brain interface would significantly influence the magnitude and distribution of the load transmitted to the brain. With sliding brain-skull interface, the brain had lower maximum principal stress compared to that with strong connected interface, while the maximum principal strain slightly increased. In addition, greater shear modulus resulted in slightly higher the maximum principal stress and significantly lower the maximum principal strain. This study has revealed that using models with different modeling approaches, the same value of injury metric may correspond to different injury severity.

Age targeted human body models indicate increased thoracic injury risk with aging

Objective The objective of this study is to generate age targeted versions of the male and female Global Human Body Models Consortium (GHBMC) occupant human body models (HBMs), to validate each in frontal impacts, and to assess rib fracture probability of each. Methods Six age targeted models were developed based on the GHBMC average male and small female occupant models (M50-O v6.0 and F05-O v6.0, respectively). All age targeted models were modified to represent population means for height, weight, shape, and relevant material properties. The thin plate spline method was used to morph models, and material properties were modified using available literature. Validation focused on chest response. Models were evaluated in a rigid body frontal chest impact at 6.7 m/s. Furthermore, the male and female age targeted models were evaluated against published data from 40 km/hr and 30 km/hr frontal sled tests respectively. Results Chest deflections and landmark kinematics reasonably matched the respective corridors in the M50-O and F05-O aged models. Regional probability of rib fracture was assessed using probabilistic methods based on cortex strain. Increasing rib fracture with age was observed in both impacts for both sexes. For the rigid chest impact, the M50-O 70YO resulted in 10 ribs exceeding 50% probability of fracture whereas the younger ages reported 4 to 6 ribs exceeding the same probability. In the same simulation, the F05-O 70YO resulted in 8 regions exceeding 50% probability of rib fracture as opposed to 3 and 0 such regions at the youngest ages. Sled simulation demonstrated similar trends. The 70YO age adjusted models best aligned with the reported extent of fractures from the referenced PMHS studies, which tend to be composed of subjects of advanced age. Conclusions Age targeted HBMs demonstrated increased fracture probability with age when subjected to equivalent impacts. Gross model kinematics approximate PMHS data but showed little difference between targeted age models. The findings indicate that while gross kinematics are unaffected by age-targeting models, such models can capture trends of increased thoracic injury risk observed in experimental and field studies, and further suggest their potential use to target interventions for vulnerable driving populations, such as older adults.

Development and Validation of a New Anisotropic Visco-Hyperelastic Human Head Finite Element Model Capable of Predicting Multiple Brain Injuries

This paper reports on the latest refinement of the Finite Element Global Human Body Models Consortium 50th percentile (GHBMC M50) adult male head model by the development and incorporation of a new material model into the white matter tissue of the brain. The white matter is represented by an anisotropic visco-hyperelastic material model capable of simulating direction-dependent response of the brain tissue to further improve the bio-fidelity and injury predictive capability of the model. The parameters representing the material were optimized by comparing model responses to seven experimentally reported strain responses of brains of postmortem human subjects (PMHS) subjected to head impact. The head model was subjected to rigorous validation against experimental data on force–deflection responses in the skull and face, intracranial pressure, and brain strain responses from over 34 PMHS head impact experiments. Crash-induced injury indices (CIIs) for facial bone fracture, skull fracture, cerebral contusion, acute subdural hematomas (ASDHs), and diffuse brain injury were developed by reconstructing 32 PMHS and real-world injury cases with the model. Model predicted maximum principal strain (MPS) and stress were determined as fracture CIIs for compact bone and spongy bones, respectively, in the skull and face. Brain responses in terms of MPS, MPS rates, and pressure distribution in injury producing experimental impacts were determined using the model and analyzed with logistic regression and survival analysis to develop CIIs for brain contusions, diffuse brain injuries, and ASDH. The statistical models using logistic regression and survival analysis showed high accuracy with area under the receiver operating curve greater than 0.8. Because of lack of sufficient moderate diffuse brain injury data, a statistical model was not created, but all indications are that the MPS rate is an essential brain response that discriminates between moderate and severe brain injuries. The authors stated that the current GHBMC M50 v.6.0 is an advanced tool for injury prediction and mitigation of injuries in automotive crashes, sports, recreational, and military environments.