An improved lower leg multibody 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.
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 ...
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 ...
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.
Pilot study on proximal femur strains during locomotion and fall-down scenario
The most common and severe type of fracture among the elderly is known as a proximal femur fracture. Aging-related bone loss is one of the major contributing factors to increased chances of bone fracture. Specific exercises can be used to strain bones and increase bone strength to counter the effects of bone loss. The flexible multibody simulation approach can be used as a non-invasive method for estimating bone strains caused by physical activity. This method was recently used to analyze the strain of locomotion in regards to human femur and tibia leg bones. The current study focuses on strain analysis of the femoral neck. The research test person was a clinically healthy 65-year old Caucasian male. The computed tomography was used to build a geometrically accurate finite element model of the femur with inhomogeneous material properties derived from the voxel data. The anthropometric data was used to model the musculoskeletal system of the test person. The multibody skeletal model was utilized to estimate loading on the femoral neck during walking, which represents a routine daily activity. The flexible multibody simulation results were compared to strains that occurred during a simulated fall onto the greater trochanter of the femur. The fall simulation was made entirely using finite element software. Results from the finite element analysis were compared with the previous study showing that the test person does not belong to the high-risk hip fracture group. Finally, the estimated strains gathered from the walking simulation were compared to the strain values from the simulated fall-down scenario.
Journal of Biomechanics, 2009
Injuries due to backward fall apart from sideways fall are a major health problem, particularly among the aged populations. The objectives of this study was to evaluate the responses to changing body configurations (angle between the trunk and impacting floor as 01, 151, 451 and 801) during backward fall, based on a previously developed CT-scan-derived 3D non-linear and non-homogeneous finite element (FE) model of pelvis-femur-soft tissue complex with simplified biomechanical representation of the whole body. Under constant impact energy, these FE models evaluated the pelvic injury situations on the basis of peak impact force (7.64-16.74 kN) and peak principal compressive strain (more than 1.5%), consistent with the clinically observed injuries (sacral insufficiency, coccydynia). Also the change in location of peak strain and increase in peak impact force for changing configurations from 01 to 801 indicated the effect of whole body inertia during backward fall. It was also concluded that the inclusion of sacro-iliac and acetabular cartilages in the above FE models will further reduce above findings marginally (9.2% for 151 fall). These quantifications would also be helpful for a better design and development of safety structures such as safety floor for the nursing home or home for the aged persons.
Flexible multibody simulation approach in the analysis of tibial strain during walking
Journal of Biomechanics, 2008
ABSTRACT Strains within the bone tissue play a major role in bone (re)modeling. These small strains can be assessed using experimental strain gage measurements, which are challenging and invasive. Further, the strain measurements are, in practise, limited to certain regions of superficial bones only, such as the anterior surface of the tibia. In this study, tibial strains occurring during walking were estimated using a numerical approach based on flexible multibody dynamics. In the introduced approach, a lower body musculoskeletal model was developed by employing motion capture data obtained from walking at a constant velocity. The motion capture data was used in inverse dynamics simulation to teach the muscles in the model to replicate the motion in forward dynamics simulation. The maximum and minimum tibial principal strains predicted by the model were 490 and -588 microstrain, respectively, which are in line with literature values from in vivo measurements. In conclusion, the non-invasive flexible multibody simulation approach may be used as a surrogate for experimental bone strain measurements and thus be of use in detailed strain estimations of bones in different applications.
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.
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."