A critique of the THUMS lower limb model for pedestrian impact applications (original) (raw)
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A finite element model of the lower limb for simulating pedestrian impacts.
Stapp car crash …, 2005
A finite element (FE) model of the lower limb was developed to improve the understanding of injury mechanisms of thigh, knee, and leg during car to pedestrian impacts and to aid in the design of injury countermeasures for vehicle front-ends. The geometry of the model was reconstructed from CT scans of the Visible Human Project Database and commercial anatomical databases. The geometry and mass were scaled to those of a 50th percentile male and the entire lower limb was positioned in a standing position according to the published anthropometric references. A "structural approach" was utilized to generate the FE mesh using mostly hexahedral and quadrilateral elements to enhance the computational efficiency of the model. The material properties were selected based on a synthesis on current knowledge of the constitutive models for each tissue. Since no reliable data could be found in the literature for flesh, skin, and ligaments, new constitutive properties were determined from experiments on post-mortem human surrogate (PMHS) specimens. Optimization techniques were used to insure consistency among all material test and component test conditions. The validation process of the model included component level tests specific to pedestrian impact loadings from both the literature and more than 30 new PMHS tests. Overall results obtained in the validation indicated improved biofidelity relative to previously published FE models.
A Finite Element Model of the Lower Limb for Simulating Automotive Impacts
Annals of Biomedical Engineering, 2012
"A finite element (FE) model of a vehicle occupant’s lower limb was developed in this study to improve understanding of injury mechanisms during traffic crashes. The reconstructed geometry of a male volunteer close to the anthropometry of a 50th percentile male was meshed using mostly hexahedral and quadrilateral elements to enhance the computational efficiency of the model. The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The models of the femur, tibia, and leg were validated against Post-Mortem Human Surrogate (PMHS) data in various loading conditions which generates the bone fractures observed in traffic accidents. The model was then used to investigate the tolerances of femur and tibia under axial compression and bending. It was shown that the bending moment induced by the axial force reduced the bone tolerance significantly more under posterior-anterior (PA) loading than under anterior-posterior (AP) loading. It is believed that the current lower limb models could be used in defining advanced injury criteria of the lower limb and in various applications as an alternative to physical testing, which may require complex setups and high cost."
Characterization of the lower limb soft tissues in pedestrian finite element models
2005
ABSTRACT Current finite element (FE) models of the human lower extremity lack accurate material properties of the soft tissues (flesh, fat, and knee ligaments), which are needed for computational evaluation of pedestrian injuries. Medial collateral ligament (MCL) is the most frequently injured ligament in lateral impacts. Therefore, the accuracy of the viscoelastic mechanical properties of the MCL FE model is of crucial importance in modeling pedestrian impacts.
Traffic injury prevention, 2017
The goal of this study was to evaluate the biofidelity of the Total Human Model for Safety (THUMS; Ver. 4.01) pedestrian finite element models (PFEM) in a whole-body pedestrian impact condition using a well-characterized generic pedestrian buck model. The biofidelity of THUMS PFEM was evaluated with respect to data from 3 full-scale postmortem human subject (PMHS) pedestrian impact tests, in which a pedestrian buck laterally struck the subjects using a pedestrian buck at 40 km/h. The pedestrian model was scaled to match the anthropometry of the target subjects and then positioned to match the pre-impact postures of the target subjects based on the 3-dimensional motion tracking data obtained during the experiments. An objective rating method was employed to quantitatively evaluate the correlation between the responses of the models and the PMHS. Injuries in the models were predicted both probabilistically and deterministically using empirical injury risk functions and strain measures...
Development and Evaluation of A Human Lower Extremity Model
17th ESV Conference, Paper, 2001
A finite element model of the human lower extremity has been developed in this study to simulate lower extremity behavior in frontal car crashes. Precise geometry of the human lower extremity and material properties of the hard and soft tissues were ...
International Journal of Vehicle Safety, 2009
This paper investigates the effect of muscle contraction on lower extremity injuries in car-pedestrian lateral impacts. Three variables, viz. height of impact, pedestrian offset with respect to car centre and impact speed, are considered. Full-scale car-pedestrian FE simulations have been performed using the full body pedestrian model with active lower extremities (PMALE) and front structures of a car model. Two pre-impact conditions of a symmetrically standing pedestrian, representing a cadaver and an unaware pedestrian, have been simulated. It is concluded that (1) with muscle contraction risk of ligament failure decreases whereas risk of bone fracture increases; (2) ligament and bone strains are dependent on the impact location;
Development and Validation of a Mathematical Breakable Leg Model
1993
A mathematical breakable leg model was developed and implemented into the pedestrian lower extremity model. The leg model consists of two rigid-body elements connected by a "fracturable joint". The moment- deformation characteristics of the "fracturable joint" are described by the user subroutines, which were prepared and added to the MADYMO three-dimensional program system. The input data for the "fracturable joint" model originate from available biological specimen tests. Computer simulations of car-pedestrian impact with this modified pedestrian model were conducted at a speed of 31 km/h in four different configurations, and compared with previously performed human leg specimen tests. Different types of bumper compliance and bumper levels were simulated. The bumper force, the accelerations, the condyle contact forces and the ligament strains were calculated during simulations. The results showed that the modified model gave a higher biofidelity than ...
A Finite Element Model of the Foot and Ankle for Automotive Impact Applications
Annals of Biomedical Engineering, 2012
A finite element (FE) model of the foot and leg was developed to improve understanding of injury mechanisms of the ankle and subtalar joints during vehicle collisions and to aid in the design of injury countermeasures. The FE model was developed based on the reconstructed geometry of a male volunteer close to the anthropometry of a 50th percentile male and a commercial anatomical database. While the forefoot bones were defined as rigid bodies connected by ligament models, the surrounding bones of the ankle and subtalar joints and the leg bones were modeled as deformable structures. The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The whole foot and leg model was validated in different loading conditions including forefoot impact, axial rotation, dorsiflexion, and combined loadings. Overall results obtained in the model validation indicated improved biofidelity relative to previous FE models. The developed model was used to investigate the injury tolerance of the ankle joint under brake pedal loading for internally and externally rotated feet. Ligament failures were predicted as the main source of injury in this loading condition. A 12% variation of failure moment was observed in the range of axial foot rotations (±15°). The most vulnerable position was the internally rotated (15°) posture among three different foot positions. Furthermore, the present foot and ankle model will be coupled together with other body region FE models into the state-of-art human FE model to be used in the field of automotive safety.