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Technical Paper

Development of an FE Model of the Rat Head Subjected to Air Shock Loading

2010-11-03
2010-22-0011
As early as the 1950's, Gurdjian and colleagues (Gurdjian et al., 1955) observed that brain injuries could occur by direct pressure loading without any global head accelerations. This pressure-induced injury mechanism was "forgotten" for some time and is being rekindled due to the many mild traumatic brain injuries attributed to blast overpressure. The aim of the current study was to develop a finite element (FE) model to predict the biomechanical response of rat brain under a shock tube environment. The rat head model, including more than 530,000 hexahedral elements with a typical element size of 100 to 300 microns was developed based on a previous rat brain model for simulating a blunt controlled cortical impact. An FE model, which represents gas flow in a 0.305-m diameter shock tube, was formulated to provide input (incident) blast overpressures to the rat model. It used an Eulerian approach and the predicted pressures were verified with experimental data.
Technical Paper

Application of a Finite Element Model of the Brain to Study Traumatic Brain Injury Mechanisms in the Rat

2006-11-06
2006-22-0022
Complete validation of any finite element (FE) model of the human brain is very difficult due to the lack of adequate experimental data. However, more animal brain injury data, especially rat data, obtained under well-defined mechanical loading conditions, are available to advance the understanding of the mechanisms of traumatic brain injury. Unfortunately, internal response of the brain in these experimental studies could not be measured. The aim of this study was to develop a detailed FE model of the rat brain for the prediction of intracranial responses due to different impact scenarios. Model results were used to elucidate possible brain injury mechanisms. An FE model, consisting of more than 250,000 hexahedral elements with a typical element size of 100 to 300 microns, was developed to represent the brain of a rat. The model was first validated locally against peak brain deformation data obtained from nine unique dynamic cortical deformation (vacuum) tests.
Technical Paper

Development of Numerical Models for Injury Biomechanics Research: A Review of 50 Years of Publications in the Stapp Car Crash Conference

2006-11-06
2006-22-0017
Numerical analyses frequently accompany experimental investigations that study injury biomechanics and improvements in automotive safety. Limited by computational speed, earlier mathematical models tended to simplify the system under study so that a set of differential equations could be written and solved. Advances in computing technology and analysis software have enabled the development of many sophisticated models that have the potential to provide a more comprehensive understanding of human impact response, injury mechanisms, and tolerance. In this article, 50 years of publications on numerical modeling published in the Stapp Car Crash Conference Proceedings and Journal were reviewed. These models were based on: (a) author-developed equations and software, (b) public and commercially available programs to solve rigid body dynamic models (such as MVMA2D, CAL3D or ATB, and MADYMO), and (c) finite element models.
Technical Paper

Development of a Three-Dimensional Finite Element Chest Model for the 5th Percentile Female

2005-11-09
2005-22-0012
Several three-dimensional (3D) finite element (FE) models of the human body have been developed to elucidate injury mechanisms due to automotive crashes. However, these models are mainly focused on 50th percentile male. As a first step towards a better understanding of injury biomechanics in the small female, a 3D FE model of a 5th percentile female human chest (FEM-5F) has been developed and validated against experimental data obtained from two sets of frontal impact, one set of lateral impact, two sets of oblique impact and a series of ballistic impacts. Two previous FE models, a small female Total HUman Model for Safety (THUMS-AF05) occupant version 1.0ϐ (Kimpara et al., 2002) and the Wayne State University Human Thoracic Model (WSUHTM, Wang 1995 and Shah et al., 2001) were integrated and modified for this model development.
Technical Paper

Numerical Investigations of Interactions between the Knee-Thigh-Hip Complex with Vehicle Interior Structures

2005-11-09
2005-22-0005
Although biomechanical studies on the knee-thigh-hip (KTH) complex have been extensive, interactions between the KTH and various vehicular interior design parameters in frontal automotive crashes for newer models have not been reported in the open literature to the best of our knowledge. A 3D finite element (FE) model of a 50th percentile male KTH complex, which includes explicit representations of the iliac wing, acetabulum, pubic rami, sacrum, articular cartilage, femoral head, femoral neck, femoral condyles, patella, and patella tendon, has been developed to simulate injuries such as fracture of the patella, femoral neck, acetabulum, and pubic rami of the KTH complex. Model results compared favorably against regional component test data including a three-point bending test of the femur, axial loading of the isolated knee-patella, axial loading of the KTH complex, axial loading of the femoral head, and lateral loading of the isolated pelvis.
Technical Paper

The Influence of Surrogate Blood Vessels on the Impact Response of a Physical Model of the Brain

2004-11-01
2004-22-0012
Cerebral blood vessels are an integral part of the brain and may play a role in the response of the brain to impact. The purpose of this study was to quantify the effects of surrogate vessels on the deformation patterns of a physical model of the brain under various impact conditions. Silicone gel and tubing were used as surrogates for brain tissue and blood vessels, respectively. Two aluminum cylinders representing a coronal section of the brain were constructed. One cylinder was filled with silicone gel only, and the other was filled with silicone gel and silicone tubing arranged in the radial direction in the peripheral region. An array of markers was embedded in the gel in both cylinders to facilitate strain calculation via high-speed video analysis. Both cylinders were simultaneously subjected to a combination of linear and angular acceleration using a two-segment pendulum.
Technical Paper

Mechanical Characterization of Porcine Abdominal Organs

2002-11-11
2002-22-0003
Typical automotive related abdominal injuries occur due to contact with the rim of the steering wheel, seatbelt and armrest, however, the rate is less than in other body regions. When solid abdominal organs, such as the liver, kidneys and spleen are involved, the injury severity tends to be higher. Although sled and pendulum impact tests have been conducted using cadavers and animals, the mechanical properties and the tissue level injury tolerance of abdominal solid organs are not well characterized. These data are needed in the development of computer models, the improvement of current anthropometric test devices and the enhancement of our understanding of abdominal injury mechanisms. In this study, a series of experimental tests on solid abdominal organs was conducted using porcine liver, kidney and spleen specimens. Additionally, the injury tolerance of the solid organs was deduced from the experimental data.
Technical Paper

Computational Study of the Contribution of the Vasculature on the Dynamic Response of the Brain

2002-11-11
2002-22-0008
Brain tissue architecture consists of a complex network of neurons and vasculature interspersed within a matrix of supporting cells. The role of the relatively suffer blood vessels on the more compliant brain tissues during rapid loading has not been properly investigated. Two 2-D finite element models of the human head were developed. The basic model (Model I) consisted of the skull, dura matter, cerebral spinal fluid (CSF), tentorium, brain tissue and the parasagittal bridging veins. The pia mater was also included but in a simplified form which does not correspond to the convolutions of the brain. In Model II, major branches of the cerebral arteries were added to Model I. Material properties for the brain tissues and vasculature were taken from those reported in the literature. The model was first validated against intracranial pressure and brain/skull relative motion data from cadaveric tests.
Technical Paper

Development of a Computer Model to Predict Aortic Rupture Due to Impact Loading

2001-11-01
2001-22-0007
Aortic injuries during blunt thoracic impacts can lead to life threatening hemorrhagic shock and potential exsanguination. Experimental approaches designed to study the mechanism of aortic rupture such as the testing of cadavers is not only expensive and time consuming, but has also been relatively unsuccessful. The objective of this study was to develop a computer model and to use it to predict modes of loading that are most likely to produce aortic ruptures. Previously, a 3D finite element model of the human thorax was developed and validated against data obtained from lateral pendulum tests. The model included a detailed description of the heart, lungs, rib cage, sternum, spine, diaphragm, major blood vessels and intercostal muscles. However, the aorta was modeled as a hollow tube using shell elements with no fluid within, and its material properties were assumed to be linear and isotropic.
Technical Paper

Lower Limb: Advanced FE Model and New Experimental Data

2001-11-01
2001-22-0022
The Lower Limb Model for Safety (LLMS) is a finite element model of the lower limb developed mainly for safety applications. It is based on a detailed description of the lower limb anatomy derived from CT and MRI scans collected on a subject close to a 50th percentile male. The main anatomical structures from ankle to hip (excluding the hip) were all modeled with deformable elements. The modeling of the foot and ankle region was based on a previous model Beillas et al. (1999) that has been modified. The global validation of the LLMS focused on the response of the isolated lower leg to axial loading, the response of the isolated knee to frontal and lateral impact, and the interaction of the whole model with a Hybrid III model in a sled environment, for a total of nine different set-ups. In order to better characterize the axial behavior of the lower leg, experiments conducted on cadaveric tibia and foot were reanalyzed and experimental corridors were proposed.
Technical Paper

Finite Element Simulation of Ankle/Foot Injury in Frontal Crashes

2000-03-06
2000-01-0156
Finite element models of human body segments have been developed in recent years. Numerical simulation could be helpful when understanding injury mechanisms and to make injury assessments. In the lower leg injury research in NISSAN, a finite element model of the human ankle/foot is under development. The mesh for the bony part was taken from the original model developed by Beaugonin et al., but was revised by adding soft tissue to reproduce realistic responses. Damping effect in a high speed contact was taken into account by modeling skin and fat in the sole of the foot. The plantar aponeurosis tendon was modeled by nonlinear bar elements connecting the phalanges to the calcaneus. The rigid body connection, which was defined at the toe in the original model for simplicity, was removed and the transverse ligaments were added instead in order to bind the metatarsals and the phalanges. These tendons and ligaments were expected to reproduce a realistic response in compression.
Technical Paper

Experimental and Analytical Study of Knee Fracture Mechanisms in a Frontal Knee Impact

1996-11-01
962423
The mechanisms of knee fracture were studied experimentally using cadaveric knees and analytically by computer simulation. Ten 90 degree flexed knees were impacted frontally by a 20 kg pendulum with a rigid surface, a 450 psi (3.103 MPa) crush strength and a 100 psi (0.689 MPa) crush strength aluminum honeycomb padding and a 50 psi (0.345 MPa) crush strength paper honeycomb padding at a velocity of about five m/s. During rigid surface impact, a patella fracture and a split condylar fracture were observed. The split condylar fracture was generated by the patella pushing the condyles apart, based on a finite element model using the maximum principal stress as the injury criterion. In the case of the 450 psi aluminum honeycomb padding, the split condylar fracture still occurred, but no patella fractures were observed because the honeycomb provided a more uniform distribution of patella load. No bony fractures in the knee area occurred for impacts with a 50 psi paper honeycomb padding.
Technical Paper

A New Model Comparing Impact Responses of the Homogeneous and Inhomogeneous Human Brain

1995-11-01
952714
A new three-dimensional human head finite element model, consisting of the scalp, skull, dura, falx, tentorium, pia, CSF, venous sinuses, ventricles, cerebrum (gray and white matter), cerebellum, brain stem and parasagittal bridging veins has been developed and partially validated against experimental data of Nahum et al (1977). A frontal impact and a sagittal plane rotational impact were simulated and impact responses from a homogeneous brain were compared with those of an inhomogeneous brain. Previous two-dimensional simulation results showed that differentiation between the gray and white matter and the inclusion of the ventricles are necessary in brain modeling to match regions of high shear stress to locations of diffuse axonal injury (DAI). The three-dimensional simulation results presented here also showed the necessity of including these anatomical features in brain modeling.
Technical Paper

Finite Element Modeling of Gross Motion of Human Cadavers in Side Impact

1994-11-01
942207
Seventeen Heidelberg type cadaveric side impact sled tests, two sled-to-sled tests, and forty-four pendulum tests have been conducted at Wayne State University, to determine human responses and tolerances in lateral collisions. This paper describes the development of a simplified finite element model of a human occupant in a side impact configuration to simulate those cadaveric experiments. The twelve ribs were modeled by shell elements. The visceral contents were modeled as an elastic solid accompanied by an array of discrete dampers. Bone condition factors were obtained after autopsy to provide material properties for the model. The major parameters used for comparison are contact forces at the level of shoulder, thorax, abdomen and pelvis, lateral accelerations of ribs 4 and 8 and of T12, thoracic compression and injury functions V*C, TTI and ASA.
Technical Paper

Shear Stress Distribution in the Porcine Brain due to Rotational Impact

1994-11-01
942214
Two-dimensional finite element models for three coronal sections of the porcine brain have been developed and the results were compared with injury data from animal experiments performed at the University of Pennsylvania (Ross et al, 1994). The models consisted of a three-layered skull, dura, CSF, white matter, gray matter and ventricles. Model I, a section at the septal nuclei and anterior commissure level, contains 490 solid elements and 108 membrane elements. Model II, a section at the rostral-thalamic level, contains 644 solid elements and 130 membrane elements. Model III, a section at the caudal hippocampal level, contains 548 solid elements and 104 membrane elements. Plane strain conditions were assumed for all models. Material properties of the brain were taken from previous human brain models, but the white matter was assumed to be about 60% stronger than the gray matter with the same Poisson's ratio.
Technical Paper

Finite Element Modeling of Direct Head Impact

1993-11-01
933114
A 3-D finite element human head model has been developed to study the dynamic response of the human head to direct impact by a rigid impactor. The model simulated closely the main anatomical features of an average adult head. It included the scalp, a three-layered skull, cerebral spinal fluid (CSF), dura mater, falx cerebri, and brain. The layered skull, cerebral spinal fluid, and brain were modeled as brick elements with one-point integration. The scalp, dura mater, and falx cerebri were treated as membrane elements. To simulate the strain rate dependent characteristics of the soft tissues, the brain and the scalp were considered as viscoelastic materials. The other tissues of the head were assumed to be elastic. The model contains 6080 nodes, 5456 brick elements, and 1895 shell elements. To validate the head model, it was impacted frontally by a cylinder to simulate the cadaveric tests performed by Nahum et. al. (8).
Technical Paper

Lower Abdominal Tolerance and Response

1986-10-27
861878
Twelve unembalmed human cadavers were tested for lower abdominal injury tolerance and mechanical response. The impacts were in an anterior-to-posterior direction and the level of impact was primarily in the lower abdomen at the L3 level of the lumbar spine. The impactor mass was either 32 kg or 64 kg. The impactor face was a 25 mm diameter aluminum bar, with the long axis of the bar parallel to the width of the cadaver body. In this paper, mechanical response is presented in terms of force-time and penetration-time histories, and force vs. abdominal penetration cross-plots. Injury tolerance is described in terms of post-impact necropsy findings and AIS ratings. Based on our studies, the lower abdomen of the unembalmed human cadaver is much less stiff than is suggested by previous research, and the stiffness is velocity and mass dependent, as is suggested by the correlation coefficients presented in this paper. Force-time history and force-penetration response corridors are presented.
Technical Paper

Lower Limb Biomechanics

1986-10-01
861924
Normal motion of the lower limbs is discussed in this paper. The biomechanics of human gait has been studied experimentally using an instrumented walkway and analytically by means of mathematical models. Experimental methods for measuring ground reaction forces and limb kinematics are discussed. If limb kinematics are known, they can be used to compute the resultant joint forces and moments, using equations of motion which are algebraic in form. To obtain limb kinematics from the differential equations of motion, the problem is generally redundant, the degree of redundancy being equal to the number of unknown joint moments. The computation of muscle, ligament and bone contact forces from known resultant loads is also a redundant problem because there are more unknowns than there are available equations. For these there is no general consensus regarding the best objective function to be minimized.
Technical Paper

Regional Tolerance to Impact Acceleration

1985-04-01
850852
Human tolerance data have been acquired gradually over the past 25 years and are available for several body regions. There is now sufficient information to design restraint systems which can prevent serious injuries to the user and which have low injury-causing potential. This paper reviews recent research on injury mechanisms and injury tolerance. Most of the research was aimed at solving problems in automotive safety systems. Specific tolerance data for the following body regions are presented: head, chest, spine and lower extremities.
Technical Paper

Mathematical Model of an Airbag for a Three-Dimensional Occupant Simulation

1972-02-01
720036
A mathematical model of an airbag restraint system for automobile drivers, including the simulation of the simultaneous collapse of the steering column, has been developed. The model is designed to work in conjunction with a three-dimensional occupant model. It is capable of assessing the relative effects of airbag size, pressure, deployment rate, venting area, contact force, steering column collapse force, and column collapse distance. The results of the model are compared with experimental runs in which anthropometric dummies were used as test subjects. Good correlation was obtained for torso kinematics. The model can be conveniently used for a parametric study to aid the design of airbag restraint systems.
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