Human Body Finite Element Model Research Articles

Importance of impact boundary conditions and pre-crash arm position for the prediction of thoracic response to pendulum, side sled, and near side vehicle impacts

Two contemporary finite element Human Body Models (HBMs) were subjected to five lateral impact scenarios to investigate the sensitivity of thorax response to impact scenario and pre-crash arm position. The greatest increase in chest compression (UW-HBM: +140%, GHBMC-HBM: +100%) and Viscous Criterion (UW-HBM: +467%, GHBMC-HBM: +245%) occurred when the arm was aligned with the thorax in a full vehicle impact, moderate change for sled impacts, and only a minor change in response for pendulum impacts. This study highlights the importance of including full vehicle impact boundary conditions in parametric studies of occupant response in side impacts and assessing side-impact protection.

Dynamic Tensile Response of Caprine Muscles Using Split Hopkinson Pressure Bar

Computer modeling and numerical simulation has become an efficient diagnostic tool to predict the human body injuries caused due to high speed automotive impacts, blast and ballistic impacts. Soft tissues such as muscles and skin in human body are exposed to varying strain rates under dynamic loadings during impacts. The prediction of impact-induced injuries requires a thorough understanding of mechanical behaviour of soft tissues for computational modeling of human body. In the present study, uniaxial tensile tests were conducted on caprine lower extremity muscles in the strain rate range of (500s^-1-3500s^-1) using custom-made split Hopkinson pressure bar (SHPB) apparatus. The challenges in the dynamic testing of soft tissues such as measurement of weak transmitted signals, use of viscoelastic pressure bars, tensile loading of specimen and generation of constant strain rate were addressed in dynamic tensile testing of soft tissues using polymeric SHPB. The attenuation and dispersion in waves are corrected using isolated incident bar tests. The stress-strain results were determined from the reconstructed waves for the tests conducted on lower extremity caprine muscles. The muscle specimens were tested along and perpendicular to the fiber direction to study the directional dependency of tissue behaviour. The stress-strain response was found to be non-linear and significant dependant on strain rate when tested along and perpendicular to fiber direction at same strain rates. It is also observed that at the same strain rate, the specimen stress of caprine muscle along the perpendicular fiber direction is higher than that along the fiber direction. The obtained results may further be used to develop finite element human body models and safety systems for human body in high rate scenario.

THE INFLUENCE OF IMPACT SPEED ON CHEST INJURY OUTCOME IN WHOLE BODY FRONTAL SLED IMPACTS

While the seatbelt restraint has significantly improved occupant safety, the protection efficiency still needs further enhance to reduce the consequence of the crash. Influence of seatbelt restraint loading on chest injury under 40 km/h has been tested and documented. However, a comprehensive profiling of the efficiency of restraint systems with various impact speeds has not yet been sufficiently reported. The purpose of this study is to analyse the effect of the seatbelt loadings on chest injuries at different impact speeds utilizing a high bio-fidelity human body Finite Element (FE) model. Based on the whole-body frontal sled test configuration, the current simulation is setup using a substitute of Post-Mortem Human Subjects (PMHS). Chest injury outcomes from simulations are analysed in terms of design variables, such as seatbelt position parameters and collision speed in a full factorial experimental design. These outcomes are specifically referred to strain-based injury probabilities and four-point chest deflections caused by the change of the parameters. The results indicate that impact speed does influence chest injury outcome. The ribcage injury risk for more than 3 fractured ribs will increase from around 40 to nearly 100% when the impact speed change from 20 to 40 km/h if the seatbelt positioned at the middle-sternum of this study. Great injuries to the chest are mainly caused by the change of inertia, which indicates that chest injuries are greatly affected by the impact speed. Furthermore, the rib fracture risk and chest deflection are nonlinearly correlated with the change of the seatbelt position parameters. The study approach can serve as a reference for seatbelt virtual design. Meanwhile, it also provides basis for the research of chest injury mechanism.

A novel modeling approach for finite element human body models with high computational efficiency and stability: application in pedestrian safety analysis

The purpose of the current study was to develop and validate a finite element (FE) pedestrian model with high computational efficiency and stability using a novel modeling approach. Firstly, a novel modeling approach of using hollow structures (HS) to simulate the mechanical properties of soft tissues under impact loading was proposed and evaluated. Then, an FE pedestrian model was developed, employing this modeling approach based on the Total Human Model for Safety (THUMS) pedestrian model, named as THUMS-HS model. Finally, the biofidelity of the THUMS-HS model was validated against cadaver test data at both segment and full-body level. The results show that the proposed hollow structures can simulate the mechanical properties of soft tissues and the predictions of the THUMS-HS model show good agreement with the cadaver test data under impact loading. Simulations also prove that the THUMS-HS model has high computational efficiency and stability. The proposed modeling approach of using hollow structures to simulate the mechanical properties of soft tissues is plausible and the THUMS-HS model could be used as a valid, efficient and robust numerical tool for analysis of pedestrian safety in vehicle collisions.

A Method to Use Kriging With Large Sets of Control Points to Morph Finite Element Models of the Human Body.

As developing finite element (FE) human body models for automotive impact is a time-consuming process, morphing using interpolation methods such as kriging has often been used to rapidly generate models of different shapes and sizes. Kriging can be computationally expensive when many control points (CPs) are used, i.e., for very detailed target geometry (e.g., shape of bones and skin). It can also lead to element quality issues (up to inverted elements) preventing the use of the morphed models for finite element simulation. This paper presents a workflow combining iterative subsampling and spatial subdivision methodology that effectively reduces the computational costs and allows for the generation of usable models through kriging with hundreds of thousands of control points. As subdivision introduces discontinuities in the interpolation function that can cause distortion of elements on the boundaries of individual subdivision areas, algorithms for smoothing the interpolation over those boundaries are proposed and compared. Those techniques and their combinations were tested and evaluated in a scenario of mass change on the detailed 50th percentile male model of the global human body models consortium (GHBMC): the model, which has body mass index (BMI) 25.34, was morphed toward a statistical surface model of a person with body mass index 20, 22.7 and 35. 234 777 control points were used to successfully morph the model in less than 15 min on an office PC. Open source implementation is provided.

Restraint systems considering occupant diversity and pre-crash posture

Objective Use volunteer data and parametric finite element (FE) human body models to investigate how restraint systems can be designed to adapt to a diverse population and pre-crash posture changes induced by active safety features. Methods Four FE human models were generated by morphing the midsize male GHBMC simplified model into geometries representing a midsize male, midsize female, short obese female (BMI 40 kg/m2), and large obese male (BMI 40 kg/m2) based on statistical skeleton and body shape geometry models. Each human model was positioned in a generic vehicle driver environment using two occupant pre-crash postures based on volunteer test results including one resulting from 1-g abrupt braking events. Improved restraint designs were manually developed for each occupant model in a 56 km/h frontal crash condition by adding a knee airbag, adjusting the shoulder belt load limit, steering column force, and driver airbag properties (tethers, inflation, and vent size). The improved designs were then tested at both pre-crash postures. Injury risks for the head, neck, chest, and lower extremities were analyzed. Results Human size and shape dominated the occupant injury measures, while the pre-crash-braking induced posture had minimal effects. Some of the safety concerns observed for large occupants include head strike-through the airbag and a conflict between head and chest injuries, which were mitigated by a stiffer restraint system with properly-tuned driver airbag. Chest injuries were a prominent safety concern for female occupants, mitigated by a softer seatbelt and smaller airbag size near the chest. Obese occupants exhibited a higher likelihood of lower extremity injuries indicating a need for a knee airbag. A diverse set of improved restraint designs were effective in lowering injury risks, indicating that restraint adaptability is necessary for accounting for occupant diversity. Conclusions This study investigated the effects of occupant size and shape variability, posture, and restraint design on injury risk for high-speed frontal crashes. More forward initial postures due to active safety features may decrease head, neck, and lower extremity injury risk, but may also increase chest injury risk. Safety concerns observed for large occupants include head strike-through and a conflict between head and chest injuries. Obese occupants had higher knee-thigh-hip injury risk. New restraints that adapt to occupant size and body shape may improve crash safety for all occupants. Further investigation is needed to confirm and extend the findings of this study.

Inverse material characterisation of human aortic tissue for traumatic injury in motor vehicle crashes

Traumatic aortic rupture (TAR) resulting due to motor vehicle crashes (MVC) accounts for about 10%–20% fatalities. This article presents the outcome of our findings of the non-linear stress–strain response and strain rate-dependent behaviour of the aortic tissue under crash like impacts. This study uses both finite element (FE) modelling and experimental testing to enhance the understanding of injury mechanisms associated with TAR. Accurate material properties are essential for correct FE model predictions. Therefore, the objective of the current study was to experimentally characterise and identify a suitable constitutive model and model parameters for aortic tissue that can be incorporated into FE human body models for studying aortic rupture. Inverse characterisation and genetic algorithms (GA) were used to train the FE model to simulate real-life scenarios applying loading in multiple directions. A total of 32 uniaxial tensile tests were conducted on human aortic tissues along with the longitudinal and circumferential directions by loading at different strain rates ranging up to 200/s. The engineering stress–strain relationship obtained for human aorta in the longitudinal and circumferential directions via uniaxial tensile tests demonstrated an approximately bilinear behaviour and strain rate dependency in both directions. The higher stresses and modulus in the circumferential direction as compared to longitudinal direction demonstrates the anisotropic behaviour of the tissue. A constitutive model has been developed and implemented via user subroutine (UMAT) in LS-DYNA that accounts for the strain rate-dependent effects and bilinear behaviour observed in the aortic tissue. A FE model of the experimental set-up was developed, and the parameters of the model were estimated using a GA-based inverse mapping technique. The developed model enables investigation of the mechanical response of the aortic tissue under crashes and other high rate loading conditions. The work is based on the premise that a reliable constitutive model coupled with a FE model of the aorta shall help predict TARs.

In vitro compressive properties of skeletal muscles and inverse finite element analysis: Comparison of human versus animals

Virtual finite element human body models have been widely used in biomedical engineering, traffic safety injury analysis, etc. Soft tissue modeling like skeletal muscle accounts for a large portion of a human body model establishment, and its modeling method is not enough explored. The present study aims to investigate the compressive properties of skeletal muscles due to different species, loading rates and fiber orientations, in order to obtain available parameters of specific material laws as references for building or improving the human body model concerning both modeling accuracy and computational cost. A series of compressive experiments of skeletal muscles were implemented for human gastrocnemius muscle, bovine and porcine hind leg muscle. To avoid long-time preservation effects, all experimental tests were carried out in 24 h after that the samples were harvested. Considering computational cost and generally used in the previous human body models, one-order hyperelastic Ogden model and three-term simplified viscoelastic quasi-linear viscoelastic (QLV) were selected for numerical analysis. Inverse finite element analysis was employed to obtain corresponding material parameters. With good fitting records, the simulation results presented available material parameters for human body model establishment, and also indicated significant differences of muscle compressive properties due to species, loading rates and fiber orientations. When considering one-order Ogden law, it is worthy of noting that the inversed material parameters of the porcine muscles are similar to those of the human gastrocnemius regardless of fiber orientations. In conclusion, the obtained material parameters in the present study can be references for global human body and body segment modeling.

The effect of adipose tissue material properties on the lap belt-pelvis interaction: A global sensitivity analysis

The lap belt-pelvis interaction is one of the main factors influencing the risk for abdominal and lower extremity injuries during vehicular crashes. To numerically study the lap belt-pelvis interaction, biofidelic representation of subcutaneous adipose tissue appears essential, especially for obese occupants with a thick layer of adipose tissue. Therefore, in this study, a finite element model is constructed and a newly developed material model for adipose tissue from the previous work is implemented to study the mechanism of lap belt-pelvis interaction and how subcutaneous adipose tissue affects this. Global Sensitivity Analysis (GSA) is used to determine which aspects of the mechanical properties of adipose tissue play a major role in the lap belt-pelvis interaction. It is found that, firstly, the incompressibility condition of adipose tissue is the most influential parameter. Secondly, the nonlinear elastic and viscoelastic properties are influential because of experiencing large deformation. The findings of this study are meaningful for vehicular injury-oriented characterization of adipose tissue as well as improving the biofidelity of finite element human body models for human safety.

The effect of posterior tethers on the biomechanics of proximal junctional kyphosis: The whole human finite element model analysis

Little is known about the effects of posterior tethers on the development of proximal junctional kyphosis (PJK). We evaluated the ability of posterior tethers to the proximal motion segment stiffness in long instrumented spinal instrumentation and fusion using a whole body human FE model. A series of finite element (FE) analysis of long segmental spinal fusion (SF) from the upper thoracic vertebra (T1) or lower thoracic vertebra (T9) to the sacrum with pedicle screws and rods were performed using an entire human body FE model (includes 234,910 elements), and compressive stresses (CS) on the anterior column, and tensile stresses (TS) on the posterior ligamentous complex (PLC) in the upper-instrumented vertebra (UIV) and the vertebra adjacent to the UIV (UIV + 1) were evaluated with posterior tethers or without posterior tethers. The models were tested at three T1 tilts (0, 20, 40 deg.), with 20% muscle contraction. Deformable material models were assigned to all body parts. Muscle-tendon complexes were modeled by truss elements with a Hill-type muscle material model. The CS of anterior column decreased with increasing T1 slope with tethers in both models, while the CS remained relatively large in T9 model compared with T1 model (T1 UIV; 0.96 to 1.56 MPa, T9 UIV; 4.79 to 5.61 MPa). The TS of the supraspinous ligament was markedly reduced in both T1 and T9 models with posterior tethers (11–35%). High vertebral CS on UIV and UIV + 1 were seen in the T9 UIV model, and the TS on the PLC were increased in both UIV models. Posterior tethers may decrease PJK development after SF with a proximal thoracic UIV, while both posterior tethers and vertebral augmentation may be necessary to reduce PJK development with a lower thoracic UIV.

Human lumbar spinal column injury criteria from vertical loading at the base: Applications to military environments

The objective of this study was to determine force-based lumbar spine injury criteria due to vertical impact using Post Mortem Human Surrogate (PMHS) experiments. Mounted personnel in military vehicles sustain loads from the pelvis in combat events such as underbody blast loadings. Forty-three post mortem human subject thoracolumbar spinal columns were obtained, screened for pre-existing trauma, bone mineral densities (BMDs) were determined, pre-test radiological images were taken, fixed at the ends in polymethylmethacrylate, load cells were attached to the ends of the fixation, positioned on custom vertical accelerator device based on a military-seating posture, and impacted at the base. Posttest images were obtained, and gross dissection was done to confirm injuries, classified into single and multilevel groups, groups A and B. Axial and resultant forces at the thoracolumbar (proximal) and lumbosacral (distal) joints were used as response variables to develop lumbar spine injury risk curves using parametric survival analysis. The Brier score metric was used to rank the variables. Age, BMD, column length, and vertebral body and intervertebral disc areas were used as covariates. The optimal metric describing the underlying response to injury was the distal resultant force for group A and proximal axial force for group B specimens. Force-BMD for group A and force-body area for group B were the best combinations. The IRCs with ±95% confidence intervals and quality of risk curves are given in the paper, and they serve as lumbar spine injury criteria. The present human cadaver Injury Risk Curves (IRCs) can be used to conduct matched pair tests to obtain dummy-based injury assessment risk curves/values to predict injury. The present IRCs can be used in human body finite element models. The relationship between covariates and primary forces presented in this study contribute to a better understanding of the role of demographic, geometric, and material factors to impact acceleration loading.

A seated human model for predicting the coupled human-seat transmissibility exposed to fore-aft whole-body vibration

Occupant discomfort, induced by vibration transmitted through a vehicle seat, can be evaluated by measuring vibration on the contact interface between the occupant and seat. In the previous study (Ittianuwat et al., 2016), measuring five contact points of the back-backrest, including centre point (ISO 2631-1), was considered as an important factor for assessing occupant comfort in frequencies where seat structure resonances occur. To enhance occupant vibration comfort in the early seat design stage, predicting the dynamic response of the coupled human-seat system on various contact locations is necessary. In this study, a low order seated human body Finite Element (FE) model was developed for predicting vibration transmissibility of the human-seat system in frequencies up to 30 Hz. Throughout the optimization process, the parameters of the model were obtained by comparing measured transmissibilities of the occupied vehicle seat system. The human-seat system vibration modes were also compared and verified with measured data by calculating MAC (Modal Assurance Criterion). The results showed that two human body vibration modes coupled with foam were observed below 10 Hz, and two coupled human and seat structure fore-aft modes were observed at around 20.1 Hz and 21.9 Hz. Fore-aft transmissibility of the model at various locations of contact provided reasonable correlation with the measured data. The developed low order human model enables the prediction of the fore-aft transmissibility on various back-backrest contact locations up to 30 Hz. This showed the capability of improving occupant's vibration comfort by predicting transmissibilities of the human-seat system in the early stage of developing a new vehicle seat.

Validating diverse human body models against side impact tests with post-mortem human subjects

This study aimed at evaluating the ability of morphed finite element (FE) human body models (HBMs) to reproduce the impact responses of post-mortem human subjects (PMHS) with various stature and shape. Ten side impact tests previously performed using seven PMHS under 3 m/s and 8 m/s impact velocities were selected for model evaluation. With weight, stature, sex, and age of PMHS, seven FE HBMs were developed by morphing the midsize male THUMS model into the target geometries predicted by the statistical skeleton and external body shape models. The model-predicted force histories, accelerations along the spine, and deflections in the chest and abdomen were compared to the test data. For comparison, simulations in all testing conditions were also conducted with the original midsize male THUMS, and the results from the THUMS simulations were scaled to the weight and stature from each PMHS. The CORrelation and Analysis (CORA) was used to evaluate the model accuracy, with CORA scores close to one indicating excellent agreement. Ten simulations using the morphed models exhibited 0.80 ± 0.01, 0.80 ± 0.01, 0.78 ± 0.02, and 0.78 ± 0.02 CORA scores for the impact forces to the thorax, abdomen, iliac-wings, and greater-trochanter, respectively; the corresponding CORA scores with the original THUMS were markedly lower at 0.60 ± 0.06, 0.69 ± 0.05, 0.71 ± 0.05, and 0.69 ± 0.04; while those for the scaled THUMS were 0.65 ± 0.05, 0.71 ± 0.05, 0.73 ± 0.05, and 0.72 ± 0.02, also lower than the morphed models. Across all simulations, the morphed HBMs demonstrated significantly higher accuracy than the THUMS with or without scaling. These results suggested the necessity of accounting for size and shape effects on predicting human responses in side impacts.

Effects of active muscle forces on driver’s lower-limb injuries due to emergency brake in various frontal impacts

Accident data shows that driver’s kinematics response in real accidents can be significantly different from that in dummy or cadaver tests because of driver’s muscle contraction. In this study, a finite element human-body model consisting of an upper body of a dummy model and a lower limb–pelvis biomechanical model with three-dimensional active muscles was developed to investigate in depth the lower-limb injuries. Driver’s emergency reaction during frontal impact was simulated by modelling muscle active contraction based on a series of volunteer experimental tests. Besides, a realistic impact environment with the response of the restraint system and the invasion of the driver’s compartment was established in this study. The results show that muscle contraction can cause extra loads on lower limbs during the impact, which can increase the injury risk of lower limbs. As for the femur injury, muscle contraction caused an additional 1 kN axial load on the femur, and the femur resultant bending moment of active models was also higher by about 10–40 N m. Besides, the tibial index of the model with muscle activation was about 0.1 higher. In addition, the results indicate that the femur injury is strongly related to the combined action of both axial force and bending moment. The variation of the injury tolerance along the tibia shaft should be considered when evaluating the tibia injury. Overall, the current lower-limb injury criteria can be still the lack of robustness.

Evaluating thoracolumbar spine response during simulated underbody blast impact using a total human body finite element model

In a study of spine injuries in Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) from 2001-09, spinal fractures sustained by mounted soldiers accounted for 26% of all injuries, and of that, 43% were caused by explosions [1]. The thoracolumbar region is the most vulnerable area of the spine [2], and injuries are often incapacitating, making egress from vehicles difficult. Injury prediction from such events continues to remain a challenge due to the limited availability of studies specifically focused on underbody blasts (UBB) and criteria on related injuries. This study focuses on developing and validating the spine response of an updated 50th percentile male Global Human Body Models Consortium (GHBMC) Finite Element (FE) model using instrumented post-mortem human subject (PMHS) laboratory tests under two unique conditions. The model was validated against response corridors created using scaled thoracic (T12, T8, T5, T1) and sacrum (S1) spine Z-axis accelerations obtained from WSU whole-body PMHS tests. The scores for the updated spine model ranged from 0.557 – 0.756 for condition 1 (Seat- 4 m/s in 10 ms; Floor- 6 m/s in 5 ms) and 0.639–0.849 for condition 2 (Seat- 4 m/s in 55 ms; Floor- 8 m/s in 2 ms). The PMHS tests sustained spinal injuries in the thoracolumbar region. The validated model indicates high stress and strain concentrations at the same locations, providing an explanation for the fractures sustained in the PMHS tests.

Evaluation of finite element human body models for use in a standardized protocol for pedestrian safety assessment

Objective: Finite element human body models (HBMs) must be certified for use within the EuroNCAP pedestrian safety assessment protocol. We demonstrate that the Global Human Body Model Consortium (GHBMC) simplified pedestrian series of HBMs meet all criteria set forth in Technical Bulletin (TB) 024 (v 1.1 Jan. 2019) for model certification. We further explore variation in head contact time (HIT) and location by HBM size and impact speed across 48 full body impact simulations.Methods: The EuroNCAP Pedestrian Protocol (v. 8.5, Oct. 2018) assesses the overall safety of adult and child pedestrians by outlining a variety of physical tests and finite element simulations using HBMs. These tests are designed to assess the efficacy of vehicle safety technology such as active bonnets. The 50th percentile male simplified pedestrian model (M50-PS, H:175 cm, W:74.5 kg), six-year-old (6YO-PS, H:117 cm, W:23.4 kg), 5th percentile female (F05-PS, H:150 cm, W:50.7 kg), and 95th percentile male (M95-PS, H:190 cm, W:102 kg) were simulated through the suite of cases totaling 48 simulations (12 each). The process gathers three kinematic trajectories and contact force data from designated anatomical locations. The impacting vehicles include a family car (FCR), multi-purpose vehicle (MPV), roadster (RDS), and sports utility vehicle (SUV), all provided by TU Graz, Vehicle Safety Institute as part of the Coherent Project, each simulated at 30 kph, 40 kph, and 50 kph. Each simulation underwent a 23-point pre-simulation check and post-simulation model response comparison. The posture of all HBMs met criteria consisting of 15 measures. All simulations were conducted in LS-Dyna R. 7.1.2.Results and Conclusions: All simulations normal terminated. For each of the simulations, sagittal plane coordinate histories of the center of the head, 12th thoracic vertebrae, and center of acetabulum were compared with standard corridors and did not exceed the tolerance of 50 mm deviation. Head contact time was also compared with the reference values and did not exceed the tolerance interval of +3.5% and -7%. Comparison of contact forces was required for monitoring purposes only. The head contact time of the models for each simulation was recorded and compared by model size, impact speed, and vehicle geometry. Head contact times varied by roughly 3-fold, were lowest for the child model, and showed the greatest sensitivity for the tallest stature model (M95-PS). As stated in the certification process, other body sizes within a model family qualify for certification if the 50th percentile male model passes, provided that model sizes meet the required posture.

A Computationally Efficient Finite Element Pedestrian Model for Head Safety: Development and Validation.

Head injuries are often fatal or of sufficient severity to pedestrians in vehicle crashes. Finite element (FE) simulation provides an effective approach to understand pedestrian head injury mechanisms in vehicle crashes. However, studies of pedestrian head safety considering full human body response and a broad range of impact scenarios are still scarce due to the long computing time of the current FE human body models in expensive simulations. Therefore, the purpose of this study is to develop and validate a computationally efficient FE pedestrian model for future studies of pedestrian head safety. Firstly, a FE pedestrian model with a relatively small number of elements (432,694 elements) was developed in the current study. This pedestrian model was then validated at both segment and full body levels against cadaver test data. The simulation results suggest that the responses of the knee, pelvis, thorax, and shoulder in the pedestrian model are generally within the boundaries of cadaver test corridors under lateral impact loading. The upper body (head, T1, and T8) trajectories show good agreements with the cadaver data in vehicle-to-pedestrian impact configuration. Overall, the FE pedestrian model developed in the current study could be useful as a valuable tool for a pedestrian head safety study.

Finite element reconstruction of real-world pedestrian accidents using THUMS pedestrian model

Finite element (FE) human body models, though providing effective means for vehicle design and assessment from the safety point of view, are still under development stage due to their limited validation. These models have been validated for cadaveric test data available in the literature for different parts. However, it has been identified that the reconstruction of the real-world accident using these FE models is required in order to evaluate their biofidelity and robustness for real crash scenarios. Hence, in the present study FE reconstruction of three real-world pedestrian accidents from RAIDS, UK database using the THUMS pedestrian model has been carried out to study the behaviour of the model during the real-world crash scenario and evaluate its biofidelity. Methodology of reconstruction has been divided into two steps: estimation of unknown kinematic parameters related to crash conditions by kinematic reconstruction using multibody simulation, and FE estimation of injuries using the THUMS pedestrian model. Because, lower extremities are most commonly injured body part in pedestrian accidents, the present work focuses on lower extremity injuries. From the reconstruction study, it has been observed that kinematic and injury response of the THUMS lower extremities model shows good conformance with the actual crash data, in terms of both kinematic and injury response.

Current playground surface test standards underestimate brain injury risk for children

Playgrounds surface test standards have been introduced to reduce the number of fatal and severe injuries. However, these test standards have several simplifications to make it practical, robust and cost-effective, such as the head is represented with a hemisphere, only the linear kinematics is evaluated and the body is excluded. Little is known about how these simplifications may influence the test results. The objective of this study was to evaluate the effect of these simplifications on global head kinematics and head injury prediction for different age groups. The finite element human body model PIPER was used and scaled to seven different age groups from 1.5 up to 18 years old, and each model was impacted at three different playground surface stiffness and three head impact locations. All simulations were performed in pairs, including and excluding the body. Linear kinematics and skull bone stress showed small influence if excluding the body while head angular kinematics and brain tissue strain were underestimated by the same simplification. The predicted performance of the three different playground surface materials, in terms of head angular kinematics and brain tissue strain, was also altered when including the body. A body and biofidelic neck need to be included, together with suitable head angular kinematics based injury thresholds, in future physical or virtual playground surface test standards to better prevent brain injuries.

Far-side occupant responses based on current US side-impact protocol using finite element human body models

Most of the applied vehicle side-impact occupant protection research to date has concentrated on near-side occupants. Currently, no regulation exists in North America for the far-side occupant protection. Real-world crash data has shown that occupants seated on the non-struck side, defined as 'far-side' occupants, are still subjected to a risk of injuries. The objective of this study is to investigate body responses for the far-side occupant using current US side impact protocols. Current side impact protocol in the USA is designed to meet side Moving Deformable Barrier (MDB) and fixed oblique pole impact. Two seating cases are addressed; the first case consisted of a far-side occupant in the first row (single occupant) to evaluate the interaction of the occupant to the structure. The second case, a near-side occupant, was added to the far-side occupant (two occupants in a row) to study the interaction of the occupant-to-occupant. A finite element human body model (50th male) was used as a far-side and near-side occupant. Simulation results indicated that the LINCAP barrier could potentially produce the significant head rotational acceleration and thoracic rib deflection if the far-side occupant was included in the existing near-side crash protocols.