Kurosh Darvish

Limiting performance analysis of toepan padding for mitigating lower limb injuries

Abstract The potential application of using toepan padding for the prevention and reduction of lower limb injuries is investigated computationally in this paper. A two-mass lower limb injury model is developed on the basis of impact tests using post-mortem human surrogates. A limiting performance analysis is used to find the best possible physical performance and characteristics of passive and active padding for the minimization of peak tibia force. Computational results indicate that, for the prevention and reduction of lower limb injuries, the active padding is superior to the passive padding.

Development and Validation of a Finite Element Model of the Lower Limb

Pedestrians struck by a vehicle frequently sustain lower limb injuries. Moreover, the biomechanics of the lower limb under lateral impact influences the trajectory of the pedestrian and subsequent injuries to the pelvis, thorax, and head. In order to increase the understanding of injury mechanisms in the lower limb, a finite element (FE) model of the lower limb was developed. The geometry of the bones and flesh was originally obtained from the Visible Human Project Database and was scaled to a 50th percentile male. The geometry of the knee ligaments was originally obtained from the 3D-CAD-Browser Database and was scaled according to the published anatomical data to align with the bones and the corresponding insertion sites. The FE mesh consists mostly of hexahedral elements which was developed using a structural mesh generator. The material and failure properties were initially selected from the literature and were later tuned based on the validation tests. The FE model was validated using the literature data and several cadaveric component tests performed specifically for model development and evaluation. The validation tests included quasi-static and dynamic lateral three-point-bend tests of the femur and the leg with flesh, and lateral four-point-bend tests of the knee joint.Copyright

Changes in Viscoelastic Properties of Brain Tissue Due to Traumatic Injury

In this study, changes in viscoelastic material properties of brain tissue due to traumatic axonal injury (TAI) were investigated. The impact acceleration model was used to generate diffuse axonal injury in rat brain. TAI in the corticospinal (CSpT) tract in the brain stem was quantified using amyloid precursor protein immunostaining. Material properties along the CSpT were determined using an indentation technique. The results showed that the number of injured axons at the pyramidal decussation (PDx) was approximated 10 times higher than in the ponto-medullary junction (PmJ). The instantaneous elastic response was reduced approximately 70% at PDx compared to 40% at PmJ and the relaxation was uniformly reduced approximately 30%, which were attributed to the effect of injury on tissue properties. Application of a visco-elastic-plastic model that changes due to TAI can significantly alter the results of computational models of brain injury.© 2004 ASME

Fluid-Structure Interaction in Finite Element Modeling of Traumatic Aortic Rupture

Traumatic Aortic Rupture (TAR) during automobile crashes is one of the leading causes of fatality. In this study, the physical parameters and mechanisms of aortic rupture in dynamic pressure loading condition were investigated using different numerical approaches in a finite element model, including Eulerian, Arbitrary Lagrangian-Eulerian (ALE), and Smoothed Particle Hydrodynamics (SPH) formulations. The TAR models were compared against in vitro experiments and predicted the most probable location of rupture at the isthmus as indicated in the literature.Copyright

Reducing Occupant Injury in Frontal Crashes for a Low-Floor City Bus

In this research, the effect of beam buckling in a predefined direction is used to reduce occupant injuries in frontal crashes of an ultra-low-floor (ULF) city bus. In ULF buses, the floor structure consists of several longitudinal long beams, which in case of a frontal crash may buckle due to the axial impact. The direction of rotational acceleration of the driver seat due to buckling is highly affected by the position of the driver seat. A finite element model of an ULF bus was developed using LS-Dyna. The driver model, a Hybrid III 50th male dummy with deformable jacket and abdomen, was restrained to the seat with a 3-point belt. An Elastic-Plastic material model was used for the bus structure to investigate the buckling behavior of the beam elements. Using diagonal beams to guide the buckling in a desired direction, rewarding results were achieved in reducing the occupant injuries. For example, with an extra diagonal beam under the seat, the driver’s HIC15 was reduced from 739 to 415.7 and HIC36 from 791 to 700.6.Copyright

Analysis and Modeling of Aortic Tissue Material Properties

A hyperelastic material with linear viscoelasticity was used to characterize the mechanical behavior of aortic tissue based on literature and new experimental data. It was shown that the previous data led to contradictory uniaxial and biaxial responses. A set of new material properties were identified which closely described the experimental data for strains below 40%.Copyright