Hyung Yun Choi

Human Models for Crash and Impact Simulation

Publisher Summary This chapter discusses the application of computational impact biomechanics to the consequences of real world passenger car accidents on human occupants, using computer models in numerical simulations with industrial crash codes. The corresponding developments are illustrated on the subject of safety simulations of human passenger car occupants. With some adaptations, the developed models apply equally well to the simulation of pedestrian accidents and to the design for occupant safety of motorbikes, trucks, railway vehicles, airborne vehicles, seagoing vessels and more. The human models elaborated in the chapter belong to the class of finite element models. They can be adapted, specialized and packaged for other industrial applications in human ergonomics and comfort analysis and design, in situations where humans operate at their work place, as military combatants, or in sports and leisure activities and more. In the medical field, biomechanical human models can serve as a basis for the simulation and design of orthopedic prostheses, for bone fracture planning, physical rehabilitation analysis, the simulation of blood flow, artificial blood vessels, artificial heart valves, bypass operations, and heart muscle activity, and virtual organ surgery.

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

Knee fracture mechanisms in a frontal knee impact are studied experimentally using cadaver knee and analytically by computer simulation. It is shown that during rigid surface impact, a patella fracture and a split condylar fracture are observed. The split condylar fracture is generated by the patella pushing the condyles apart. These results are verified using 3-D finite element human knee model. Language: en

Experimental and Numerical Analyses of Seating Pressure Distribution Patterns

In order to assess the seating comfort design of a vehicle seat system, a full finite element occupant model, with anatomically precise features and deformable tissues, has been developed. This paper describes the experiments which were performed in order to assess the biofidelic accuracy of this model. First, static pressure distribution measurements, with human volunteers, have been performed. People of different morphological types were asked to sit on a PU foam cushion with various postures, which were captured by photographs and X-Ray measurements. Pressure sensors were used to determine the corresponding pressure distribution patterns. Then, the FE occupant model was used to simulate the same experiments, and the numerical results were compared to the experimental ones.

Human body modeling for riding comfort simulation

In order to assess the seating and riding comfort design of a vehicle seat in an objective manner, finite element occupant models with anatomically precise features have been developed. The human body models are incorporated into Pam-Comfort, a tool for automotive seat design and analysis, as parts of occupant surrogates that also include HPM I and II. In this paper, the detailed process of FE human body modeling including an effort on the implementation of new anthropometry will be introduced. The validation of some features of human body models in seating and riding comfort simulation against human experiments will be also presented.

Numerical Human Head Model for Traumatic Injury Assessment

The finite element human head model is developed for traumatic injury assessment. The model is constructed based on the precise anatomical geometry and validated with test results. In this paper, structural and physiologic explanation of human head will be introduced as well as the modeling methodology. Some of simulation results are also chosen to present major features of the model.

ANALYSIS OF DURAL-SAC OCCLUSION IN A LUMBAR SPINAL MOTION SEGMENT FE MODEL

Occlusion of dural-sac in the lumbar spine was quantitatively analyzed by utilizing one motion segment of finite element lumbar spine model developed in this study. And the mechanism of occlusion, considering both static and viscous behavior of materials, was also investigated with various loading conditions. Occlusion was quantified by calculating the cross sectional area change or volumetric changes of dural-sac. In the static analysis, it was found that less than 2 kN of compressive load could not produce dural-sac occlusion but the compression together with extension moment was more likely to produce the dural-sac occlusion. The 7.4% of occlusion was obtained when the 8 Nm of extension moment was added to 2 kN of compressive load which alone did not create any occlusion. The magnitude of occlusions was increased to 10.5% as the extension moment become to 10 Nm with the same 2 kN of compressive load. In creep analysis, 10 Nm extension, kept for 3600 seconds, induced 6.9% of occlusion and 2.4% of volume reduction in dural-sac. However, flexion moment did not produce any occlusion in dural-sac but increased the volume instead because it caused stretching of dural-sac coupled with vertebra motion. As a conclusion, occlusions resulted mainly from the slackening of ligamentum flavum and disc bulging, and the amount of occlusion was strongly dependent with loading condition and visco-elastic behavior of materials as well.

Biomechanical Discomfort Factors in Egress of Older Drivers

INTRODUCTION In order to identify and quantify various biomechanical factors that affect discomfort in ingress/egress motions of older people, we performed an experimental study by employing eight healthy elderly volunteers. The ingress and egress motions in SUV mockup was captured by 12 infrared cameras for the kinematic analysis. An assistance device was designed to give some variations in the access motions. A bar-type handle was placed at the lower part of B-pillar to provide an additional support on the left arm of the driver at the early stage of the egress motion. The volunteers were normally free to choose their own ingress/egress strategies but were required to use assistant devices for the requested cases. In this paper, the results of the kinematic analysis using a digital human model with reconstructed egress motions are introduced. The joint angle changes of lower limbs showed statistical correlations with egress motion discomfort ratings.

Modelling of ergonomics and muscular comfort

Commercially available software packages permit to position human models of various geometries in practical scenarios while respecting the anatomical constraints of the skeletal joints and of the bulk of the bodies. Beyond such features, the PAM-ComfortTM software has been conceived to provide direct access to the muscular forces needed by humans to perform physical actions where muscle force is required. The PAM-ComfortTM human models are made of multi-body linked anatomical skeletons, equipped with finite elements of the relevant skeletal muscles. The hyper-static problem of determination of muscle forces is solved by optimisation techniques. Voluntary stiffening of muscles can be added to the basic contraction levels needed to perform a specific task. The calculated muscle forces obey Hills model. The model and software have been applied in several interesting scenarios of various fields of application, such as car industry, handling of equipment and sports activities.

Estimation of conditions evoking fracture in finger bones under pinch loading based on finite element analysis.

Abstract A finger finite element (FE) model was created from CT images of a Japanese male in order to obtain a shape-biofidelic model. Material properties and articulation characteristics of the model were taken from the literature. To predict bone fracture and realistically represent the fracture pattern under various loading conditions, the ESI-Wilkins-Kamoulakos rupture model in PAM-CRASH (ESI Group S.A., Paris, France) was utilized in this study with parameter values of the rupture model determined by compression testing and simulation of porcine fibula. A finger pinch simulation was then conducted to validate the finger FE model. The force-displacement curve and fracture load from the pinch simulation was compared to the result of finger pinch test using cadavers. Simulation results are coincident with the test result, indicating that the finger FE model can be used in an analysis of finger bone fracture during pinch accident. With this model, several pinch simulations were conducted with different pinching object’s stiffness and pinching energy. Conditions for evoking finger bone fracture under pinch loading were then estimated based on these results. This study offers a novel method to predict possible hazards of manufactured goods during the design process, thus finger injury due to pinch loading can be avoided.

A Study on Characterizing a Healthy Driving Posture

Abstract : To find a healthy driving posture, in this study, survey and empirical analysis given onto measurement of car-seat angle has been performed. Among 153 male respondents, those drivers who has minimum 5 year experience and 2 hours daily driving has been selected by a multiple screening process. They were further confirmed to have no discomfort history in any body region caused by the driving task. Final 44 people verified that their actual driving posture is not significantly different (p = 0.692) from healthy one they think. And their data, accordingly, the healthy driving postures are clustered based on the same seat-cushion angle, seat-back angle and trunk-thigh angle. Conse-quently, three seat-angles of the 44 subjects showed a significant difference only with their height information which is the most effecting factor on driving posture among the physical characteristics. That is a first result categorized healthy driving posture classified physical, if it were departmentalized into additional study, could be able to reflected a factor of “healthy” on car seat design.