Development and Validation of a Mathematical Breakable Leg Model (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 bumper model with dynamic contact stiffness for simulations of pedestrian legform impacts
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2013
Car-to-pedestrian accidents have become a global problem, and car manufacturers have made great efforts to redesign the car for pedestrian protection. For fast computer simulations of pedestrian legform-to-bumper impacts, which are usually needed for the large design-of-experiments matrix, quite a number of simplified bumper models have been built to represent detailed finite element models adopted from full-vehicle models. However, it has been a difficult balance between simplifying the structure to achieve fast computation and keeping the essential characteristics to obtain valid results. This paper documents a development and validation of a simplified bumper system model. The spring stiffness properties are determined by considering the loading rate effect and the local deformation effect of the vehicle's frontend structure, which is essential for legform impact simulations. To validate the simplified bumper system model, the simulation results from the simplified bumper system model and from a detailed bumper system model are compared. This study also indicates that, to improve the responses of the legform bending and shear, the vehicle's bumper should be modelled as two separate spring systems since the impact interaction is within the knee joint centre of the legform.
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."
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;
Accident Analysis & Prevention, 1994
for a pedestrian were conducted as a preliminary study for the purpose of developing a subsystem test procedure for the assessment of car-front aggressiveness to pedestrian legs. Four mechanical substitutes for a pedestrian were used in the tests: the leg of a rotationally symmetrical pedestrian dummy (RSPD) as the representation of a subsystem, a HYBRID-II pedestrian dummy, a modified HYBRID-II pedestrian dummy equipped with a steel bar serving as knee joint, and a RSPD -HYBRID-IIP combined dummy in which the lower part of the RSPD and the upper part of the HYBRID-IIP were connected by a joint in such a way that the movements of the upper part were similar tc those in cadaver tests. In the tests the following were evaluated: (i) the influence of vehicle shape on knee response and on vehicle impact force; (ii) the influence of the upper body mass on knee response and on vehicle impact forces; (iii) the influence of the bumper system on knee response, the kinematics of pedestrian mechanical substitute, and on vehicle impact forces; (iv) the influence of pedestrian mechanical substitute characteristics on its kinematics and knee response, and on vehicle impact forces. This paper describes a primary concept when subsystem test methods for the assessment of car-front aggressiveness to pedestrian iegs in-a car-pedestrian collision are considered.
Assesment of the Injury Severity of the Pedestrian Lower Limbs at the Collision with a Vehicle
ANNALS OF THE ORADEA UNIVERSITY. Fascicle of Management and Technological Engineering., 2015
The purpose of the paper is to determine the severity of the injury that may appear at the collision of the frontal part of a vehicle with the pedestrian's lower limbs. In this study the bio-mechanic model of the lower limbs was constructed, in order to determine the bending moment of the tibia. The collision forces that were used as input data were collected from a simulation performed in a traffic accident reconstruction software. The developed multi-body simulation is considering all forces acting on the lower limb. The injury severity is estimated using the bending moment of the tibia.
Upper Leg impactor modelling for Pedestrian Test simulation using F.E.M. explicit codes
Between 1977 and 1980, mainly in the United States and in Australia, independent research centres began to process several statistical data on accidents between vehicles and pedestrians, taking care, obviously, to pedestrians' injury. That problem in the early 80' became also interesting for European research centres. In 1990 a research group of EEVC (European Enhanced Vehicle-Safety Committee) had examined statistical data of past twenty years and scientific research published about this topic, and had presented several documents about "pedestrian test" procedures. In reference papers of this twenty years period (1977-97) and in documents of EEVC, the scientists describe a proposed test for upper-leg impact; it is represented by the impact of a standardised impactor (that simulate the human leg/pelvis) on car front-part; those documents have been updated in 1994, 1998 and finally in 2002 while Euro-NCAP, since 1998 had used them to realize, in specialized laborato...
A critique of the THUMS lower limb model for pedestrian impact applications
13th European LS-DYNA Conference 2021, 2021
The Total Human Model for Safety (THUMS) is widely used for biomechanics research and validated at the component and full-body levels. Nonetheless, some authors have reported differences in predictions between the model and real-life injuries, particularly in the lower limbs. This study aims to perform an extensive critique of the THUMS lower limb and identify areas for improvement. The THUMS model was assessed across quasi-static and dynamic validation tests to understand geometry, material properties and response to impact. The study has highlighted that the THUMS' geometry is comparable to published cadaveric data for bones and ligaments, but soft tissues (muscle, adipose and skin) and fascia have significant simplifications. The bones' material properties are evidence-based and vary appropriately according to anatomical site. Bone failure is permitted through element deletion; however, the unusually transverse fracture pattern predicted in THUMS is seldom seen in clinical practice. The simplified soft tissue model cannot fail, making it unable to replicate the extensive damage seen in high energy open fractures. Ligament injury is a frequent result of an impact to the pedestrian lower limb, often at the bone-tendon interface, yet the failure location seen in the THUMS model is mid-substance. In summary, THUMS makes an excellent attempt to model the lower limb; nonetheless, some work is still required to increase biofidelity. Improvements in soft tissue geometry and material properties and fracture pattern modelling represent apparent areas for development.
Lower Leg impactor modelling for Pedestrian Test simulation using F.E.M. explicit codes
In late 70', mainly in the United States and in Australia, independent research centres had processed several statistical data on accidents between vehicles and pedestrians, taking care, obviously, to pedestrians' injury. That problem in the early 80' became also interesting for European research centres. In 1990 a research group of EEVC (European Enhanced Vehicle-Safety Committee) had examined statistical data of past twenty years and scientific research published about this topic, and had presented several documents about "pedestrian test" procedures. In reference papers of period of twenty years (1977-97) and in documents of EEVC, the scientists describe a proposed test for lower-leg impact; it is represented by the impact of a standardised impactor (that simulate the human leg) on car front-part; those documents have been updated in 1994, 1998 and finally in 2002 while Euro-NCAP, since 1998 had used them to realize, in specialized laboratories, tests for gi...
International Journal of Crashworthiness, 2010
This paper investigates the effect of muscle contraction on lower extremity injuries for pedestrian walking posture in a carpedestrian lateral impact at low speed. The full body model, pedestrian model with active lower extremities (PMALE), which was configured in a symmetric standing posture, has been repositioned in the walking posture. Finite-element simulations have then been performed using the PMALE in walking posture and front structures of a car. Two impact configurations, i.e. impact on the right and left legs, have been simulated. Two pre-impact conditions, that of a symmetrically standing pedestrian, representing a cadaver and an unaware pedestrian have been simulated for both the impact configurations. Stretch-based reflexive action was included in the simulations for an unaware pedestrian. It is concluded that (1) with muscle contraction, the risk of ligament failure decreases whereas the risk of bone fracture increases; (2) in lateral impacts, MCL could be considered as the most vulnerable and LCL as the safest ligament; and (3) for a walking pedestrian, PCL would be at a higher risk in the case of impact on the rear leg, whereas ACL would be at a higher risk if car strikes the front leg.