Refine Your Search

Topic

Author

Search Results

Technical Paper

A Study of Cervical Spine Kinematics and Joint Capsule Strain in Rear Impacts using a Human FE Model

2006-11-06
2006-22-0020
Many efforts have been made to understand the mechanism of whiplash injury. Recently, the cervical facet joint capsules have been focused on as a potential site of injury. An experimental approach has been taken to analyze the vertebral motion and to estimate joint capsule stretch that was thought to be a potential cause of pain. The purpose of this study is to analyze the kinematics of the cervical facet joint using a human FE model in order to better understand the injury mechanism. The Total Human Model for Safety (THUMS) was used to visually analyze the local and global kinematics of the spine. Soft tissues in the neck were newly modeled and introduced into THUMS for estimating the loading level in rear impacts. The model was first validated against human test data in the literature by comparing vertebrae motion as well as head and neck responses. Joint capsule strain was estimated from a maximum principal strain output from the elements representing the capsule tissues.
Technical Paper

The Effects of Head Padding in Rear Facing Child Restraints

2005-04-11
2005-01-1839
Child restraint head padding is designed for the child's comfort under normal use. Under vehicle crash conditions, however, the padding in a rear facing child restraint may not be designed to sufficiently absorb impact energy. The objective of this paper is to evaluate the effects of various head padding conditions in rear facing child restraints in frontal impacts. Five sled tests were performed to measure the response of a CRABI 12 month dummy to different padding conditions in a rear facing child restraint. Static loading tests were performed on the padding materials. Results show that using padding of low stiffness increases head acceleration and HIC15 values.
Technical Paper

A Finite Element Model of the Lower Limb for Simulating Pedestrian Impacts

2005-11-09
2005-22-0008
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.
Technical Paper

A Study of Knee Joint Kinematics and Mechanics using a Human FE Model

2005-11-09
2005-22-0006
Posterior translation of the tibia with respect to the femur can stretch the posterior cruciate ligament (PCL). Fifteen millimeters of relative displacement between the femur and tibia is known as the Injury Assessment Reference Value (IARV) for the PCL injury. Since the anterior protuberance of the tibial plateau can be the first site of contact when the knee is flexed, the knee bolster is generally designed with an inclined surface so as not to directly load the projection in frontal crashes. It should be noted, however, that the initial flexion angle of the occupant knee can vary among individuals and the knee flexion angle can change due to the occupant motion. The behavior of the tibial protuberance related to the knee flexion angle has not been described yet. The instantaneous angle of the knee joint at the timing of restraining the knee should be known to manage the geometry and functions of knee restraint devices.
Technical Paper

Elimination of Thoracic Muscle Tensing Effects for Frontal Crash Dummies

2005-04-11
2005-01-0307
Current crash dummy biofidelity standards include the estimated effects of tensing the muscles of the thorax. This study reviewed the decision to incorporate muscle tensing by examining relevant past studies and by using an existing mathematical model of thoracic impacts. The study finds evidence that muscle tensing effects are less pronounced than implied by the biofidelity standard response corridors, that the response corridors were improperly modified to include tensing effects, and that tensing of other body regions, such as extremity bracing, may have a much greater effect on the response and injury potential than tensing of only the thoracic musculature. Based on these findings, it is recommended that muscle tensing should be eliminated from thoracic biofidelity requirements until there is sufficient information regarding multi-region muscle tensing response and the capability to incorporate this new data into a crash dummy.
Technical Paper

A Multi-Body Computational Study of the Kinematic and Injury Response of a Pedestrian with Variable Stance upon Impact with a Vehicle

2004-03-08
2004-01-1607
This research investigates the variation of pedestrian stance in pedestrian-automobile impact using a validated multi-body vehicle and human model. Detailed vehicle models of a small family car and a sport utility vehicle (SUV) are developed and validated for impact with a 50th percentile human male anthropometric ellipsoid model, and different pedestrian stances (struck limb forward, feet together, and struck limb backward) are investigated. The models calculate the physical trajectory of the multi-body models including head and torso accelerations, as well as pelvic force loads. This study shows that lower limb orientation during a pedestrian-automobile impact plays a dominant role in upper body kinematics of the pedestrian. Specifically, stance has a substantial effect on the subsequent impacts of the head and thorax with the vehicle. The variation in stance can change the severity of an injury incurred during an impact by changing the impact region.
Technical Paper

Displacement Measurements in the Hybrid III Chest

2001-03-05
2001-01-0118
This paper presents an analysis of the displacement measurement of the Hybrid III 50th percentile male dummy chest in quasistatic and dynamic loading environments. In this dummy, the sternal chest deformation is typically characterized using a sliding chest potentiometer, originally designed to measure inward deflection in the central axis of the dummy chest. Loading environments that include other modes of deformation, such as lateral translations or rotations, can create a displacement vector that is not aligned with this sensitive axis. To demonstrate this, the dummy chest was loaded quasistatically and dynamically in a series of tests. A string potentiometer array, with the capability to monitor additional deflection modes, was used to supplement the measurement of the chest slider.
Technical Paper

Thoracic Response to Shoulder Belt Loading: Investigation of Chest Stiffness and Longitudinal Strain Pattern of Ribs

2009-04-20
2009-01-0384
Two post-mortem human subjects were subjected to dynamic, non-injurious (up to 20% chest deflection) anterior shoulder belt loading at 0.5 m/s and 0.9 m/s loading rates. The human surrogates were mounted to a stationary apparatus that supported the spine and shoulder in a configuration comparable to that achieved in a 48 km/h sled test at the time of maximum chest deformation. A hydraulically driven shoulder belt was used to load the anterior thorax which was instrumented with a load cell for measuring reaction force and uniaxial strain gages at the 4th and 8th ribs. In addition, the deformation of the chest was measured using a 16- camera Vicon 3D motion capture system. In order to investigate the chest deformation pattern and ribcage loading in greater detail, a human finite element (FE) model of the thorax was used to simulate the tests.
Technical Paper

Internal vs. External Chest Deformation Response to Shoulder Belt Loading, Part 1: Table-Top Tests

2009-04-20
2009-01-0393
This study presents a detailed comparison of internally and externally measured chest deflections resulting from eight tests conducted on three male post mortem human subjects. A hydraulically driven shoulder belt loaded the anterior thorax under a fixed spine condition while displacement data were obtained via a high-speed 16-camera motion capture system (VICON MX™). Comparison of belt displacement and sternal displacement measured at the bone surface provided a method for quantifying effective change in superficial soft tissue depth at the mid sternum under belt loading. The relationship between the external displacement and the decrease in the effective superficial tissue depth was found to be monotonic and nonlinear. At 65 mm of mid-sternal posterior displacement measured externally, the effective thickness of the superficial tissues and air gap between the belt and the skin had decreased by 14 mm relative to the unloaded state.
Technical Paper

Comprehensive Computational Rollover Sensitivity Study Part 2: Influence of Vehicle, Crash, and Occupant Parameters on Head, Neck, and Thorax Response

2011-04-12
2011-01-1115
Fatalities resulting from vehicle rollover events account for over one-third of all U.S. motor vehicle occupant fatalities. While a great deal of research has been directed towards the rollover problem, few studies have attempted to determine the sensitivity of occupant injury risk to variations in the vehicle (roof strength), crash (kinematic conditions at roof-to-ground contact), and occupant (anthropometry, position and posture) parameters that define the conditions of the crash. A two-part computational study was developed to examine the sensitivity of injury risk to changes in these parameters. The first part of this study, the Crash Parameter Sensitivity Study (CPSS), demonstrated the influence of parameters describing the vehicle and the crash on vehicle response using LS-DYNA finite element (FE) simulations.
Technical Paper

A Study of Driver Injury Mechanism in High Speed Lateral Impacts of Stock Car Auto Racing Using a Human Body FE Model

2011-04-12
2011-01-1104
This paper analyzed the mechanisms of injury in high speed, right-lateral impacts of stock car auto racing, and interaction of the occupant and the seat system for the purpose of reducing the risk of injury, primarily rib fractures. Many safety improvements have been made to stock car racing recently, including the Head and Neck Support devices (HANS®), the 6-point restraint harnesses, and the implementation of the SAFER Barrier. These improvements have contributed greatly to mitigating injury during the race crash event. However, there is still potential to improve the seat structure and the understanding of the interaction between the driver and the seat in the continuation of making racing safety improvements. This is particularly true in the case of right-lateral impacts where the primary interaction is between the seat supports and the driver and where the chest is the primary region of injury.
Technical Paper

Occupant Kinematics and Estimated Effectiveness of Side Airbags in Pole Side Impacts Using a Human FE Model with Internal Organs

2008-11-03
2008-22-0015
When a car collides against a pole-like obstacle, the deformation pattern of the vehicle body-side tends to extend to its upper region. A possible consequence is an increase of loading to the occupant thorax. Many studies have been conducted to understand human thoracic responses to lateral loading, and injury criteria have been developed based on the results. However, injury mechanisms, especially those of internal organs, are not well understood. A human body FE model was used in this study to simulate occupant kinematics in a pole side impact. Internal organ parts were introduced into the torso model, including their geometric features, material properties and connections with other tissues. The mechanical responses of the model were validated against PMHS data in the literature. Although injury criterion for each organ has not been established, pressure level and its changes can be estimated from the organ models.
Technical Paper

Development and Validation of a Finite Element Model of a Vehicle Occupant

2004-03-08
2004-01-0325
A finite element human model has been developed to simulate occupant behavior and to estimate injuries in real-world car crashes. The model represents an average adult male of the US population in a driving posture. Physical geometry, mechanical characteristics and joint structures were replicated as precise as possible. The total number of nodes and materials is around 67,000 and 1,000 respectively. Each part of the model was not only validated against human test data in the literature but also for realistic loading conditions. Additional tests were newly conducted to reproduce realistic loading to human subjects. A data set obtained in human volunteer tests was used for validating the neck part. The head-neck kinematics and responses in low-speed rear impacts were compared between the measured and calculated results. The validity of the lower extremity part was examined by comparing the tibia force in a foot impact between the test data and simulation results.
Technical Paper

Influence of Vehicle Body Type on Pedestrian Injury Distribution

2005-04-11
2005-01-1876
Pedestrian impact protection has been a growing area of research over the past twenty or more years. The results from many studies have shown the importance of providing protection to vulnerable road users as a means of reducing roadway fatalities. Most of this research has focused on the vehicle fleet as a whole in datasets that are dominated by passenger cars (cars). Historically, the influence of vehicle body type on injury distribution patterns for pedestrians has not been a primary research focus. In this study we used the Pedestrian Crash Data Study (PCDS) database of detailed pedestrian crash investigations to identify how injury patterns differ for pedestrians struck by light trucks, vans, and sport utility vehicles (LTVs) from those struck by cars. AIS 2+ and 3+ injuries for each segment of vehicles were mapped back to both the body region of the pedestrian injured and the vehicle source linked to that injury in the PCDS database.
Technical Paper

Development and Validation of a Finite Element Model for the Polar-II Upper Body

2006-04-03
2006-01-0684
The goal of this study was to develop and validate a finite element (FE) model of the Polar-II pedestrian dummy. An upper body model consisting of the head, neck, shoulder, thorax, and abdomen was coupled with a previously validated model of the lower limb The viscoelastic material properties of the dummy components were determined from dynamic compression tests of shoulder urethane, shoulder rubber and abdominal foam. For validation of the entire upper body, the model was compared with NHTSA response requirements for their advanced frontal dummy (Thor) including head and neck pendulum tests as well as ribcage and abdominal impact tests. In addition, the Polar-II full body FE model was subjected to simulated vehicle-pedestrian impacts that recreated published experiments. Simulated head and pelvis accelerations as well as upper body trajectories reasonably reproduced the experiment.
Technical Paper

Kinematic Analysis of Head/Neck Motion in Pedestrian-Vehicle Collisions Using 6-Degree-of-Freedom Instrumentation Cubes

2006-04-03
2006-01-0681
Given the quantity and severity of head injuries to pedestrians in vehicle-to-pedestrian collisions, human pedestrian finite element models and pedestrian dummies must possess a biofidelic head/neck response to accurately reproduce head-strike kinematics and kinetics. Full-scale pedestrian impact experiments were performed on post-mortem human surrogates (PMHS) using a mid-sized sport utility vehicle and a small sedan. Kinematics of the head and torso were obtained with a six-degree-of-freedom (6DOF) cube, which contained three orthogonally mounted linear accelerometers and three angular rate sensors. The goal of the current study was to present a methodology for analyzing the data obtained from the sensors on each cube, and to use the kinematics data to calculate spatial trajectories, as well as linear velocities and angular accelerations of the head and T1 vertebra.
Technical Paper

Research of the Relationship of Pedestrian Injury to Collision Speed, Car-type, Impact Location and Pedestrian Sizes using Human FE model (THUMS Version 4)

2012-10-29
2012-22-0007
Injuries in car to pedestrian collisions are affected by various factors such as the vehicle body type, pedestrian body size and impact location as well as the collision speed. This study aimed to investigate the influence of such factors taking a Finite Element (FE) approach. A total of 72 collision cases were simulated using three different vehicle FE models (Sedan, SUV, Mini-Van), three different pedestrian FE models (AM50, AF05, AM95), assuming two different impact locations (center and the corner of the bumper) and at four different collision speeds (20, 30, 40 and 50 km/h). The impact kinematics and the responses of the pedestrian model were validated against those in the literature prior to the simulations. The relationship between the collision speed and the predicted occurrence of head and chest injuries was examined for each case, analyzing the impact kinematics of the pedestrian against the vehicle body and resultant loading to the head and the chest.
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

Assessment of the Thor and Hybrid III Crash Dummies: Steering Wheel Rim Impacts to the Upper Abdomen

2004-03-08
2004-01-0310
This investigation explored THOR's force-deflection response to upper abdomen/lower ribcage steering wheel rim impacts in comparison to the Hybrid III and cadaver test subjects. The stationary subjects were impacted by a ballasted surrogate wheel propelled at 4 m/s, a test condition designed to approximate the upper abdomen impacting a steering wheel rim in a frontal crash. Both the standard THOR and the Hybrid III crash dummies were substantially stiffer than the cadavers. Removing THOR's torso skin and foam from the upper abdomen and replacing the standard Hybrid III abdomen with a prototype gel-filled unit produced force-deflection results that were more similar to the cadavers. THOR offers advantages over the Hybrid III because of its ability to measure abdominal deflection. THOR, with modification, would be a useful instrument with which to assess the crashworthiness of steering assemblies and restraint systems in frontal crashes.
X