Jong B. Lee

Effect of Assumed Stiffness and Mass Density on the Impact Response of the Human Chest Using a Three-Dimensional FE Model of the Human Body

The mass density, Youngs modulus (E), tangent modulus (Et), and yield stress (sigma y) of the human ribs, sternum, internal organs, and muscles play important roles when determining impact responses of the chest associated with pendulum impact. A series of parametric studies was conducted using a commercially available three-dimensional finite element (FE) model, Total HUman Model for Safety (THUMS) of the whole human body, to determine the effect of changing these material properties on the predicted impact force, chest deflection, and the number of rib fractures and fractured ribs. Results from this parametric study indicate that the initial chest apparent stiffness was mainly influenced by the stiffness and mass density of the superficial muscles covering the torso. The number of rib fractures and fractured ribs was primarily determined by the stiffness of the ribcage. Similarly, the stiffness of the ribcage and internal organs contributed to the maximum chest deflection in frontal impact, while the maximum chest deflection for lateral impact was mainly affected by the stiffness of the ribcage. Additionally, the total mass of the whole chest had a moderately effect on the number of rib fractures.

Head Injuries in Airbag-Equipped Motor Vehicles with Special Emphasis on AIS 1 and 2 Facial and Loss of Consciousness Injuries

Objectives:Safety of the airbag supplemental restraint system (airbag) is a well-known concern. Although many lives are saved each year through airbag use, injuries continue to occur, especially to the head. Airbag safety research has focused primarily on severe injuries, while minor and moderate injuries have been largely ignored. Methods:In this study, 205,977 injury cases from the 1995 to 2001 National Automotive Sampling System (NASS)/ Crashworthiness Data System (CDS) were surveyed to determine the prevalence of AIS 1 and 2 facial and brain loss of consciousness (LOC) injuries and determine if these injuries are a concern. The query was focused on frontal impacts in vehicles equipped with airbags. Only occupants wearing appropriate seatbelts were included in this study so that the airbag would provide occupant protection under optimal conditions. Of the 205,977 injury cases studied, 2.4% met this criterion. Results: From the data gathered, the trends seem to indicate an increase in these specific injuries, both in terms of the total number and the proportion to all injury cases. In 1995, AIS 1 and 2 head injuries accounted for 96.5% of all head injuries caused by airbags. By 2001, the percentage had risen 3.0% to 99.5%. Injuries occurring in vehicles equipped with first-generation versus second generation airbags were compared, and data seem to suggest that there is a higher rate of minor and moderate head injuries when occupants are in second-generation airbag-equipped vehicles, even when appropriate lap and shoulder belts are used. Conclusions:The short timeframe surveyed prevents drawing meaningful conclusions about statistical significance, but the graphical representations of the data in this study underscore an urgent need for further investigation based on current trends in order to understand the issue of minor and moderate head injury prevention in regard to airbags.

Abdominal injury patterns in motor vehicle accidents: A survey of the NASS database from 1993 to 1997

The purpose of this study was to determine patterns of abdominal injuries using the publicly available National Automotive Sampling System (NASS) database. Data from the NASS database for the years between 1993 and 1997 were extracted in order to gain an enhanced understanding of abdominal injury patterns resulting from vehicular collisions. The liver was most frequently injured due to contact with components in the front of the passenger compartment, such as the steering assembly and the instrument panel. Injuries to the spleen frequently resulted from contact with components on the left side of the passenger compartment. When considering only contact with components on the sides of the passenger compartment, the liver was injured more frequently due to contact with components on the right side of the passenger compartment while contact with components on the left side of the passenger compartment were more likely to result in injuries of the spleen. A more in-depth survey of the NASS database will be needed to determine if the asymmetrical features of human anatomy must be considered in the design of crash test dummies and mathematical models used in the evaluation of abdominal impact protection in automotive accidents.

A Partially Validated Finite Element Whole-Body Human Model for Organ Level Injury Prediction

A finite element whole-body human model, which represents a 50th percentile male, was developed by integrating three detailed human component models previously developed at Wayne State University (WSU): a thorax model with detailed representation of the great vessels [1], an abdomen model [2], and a shoulder model [3]. This new model includes bony structures such as scapulae, clavicles, the vertebral column, rib cage, sternum, sacrum, and illium and soft tissue organs such as the heart, lungs, trachea, esophagus, diaphragm, kidneys, liver, spleen, and all major blood vessels including the aorta. In addition to model validations already reported at the component level, the new whole-body model was further validated against two sets of experimental data reported by Hardy [4]. In these experiments, human cadavers were loaded either by a seatbelt or by a surrogate airbag about the mid-abdomen, approximately at the level of umbilicus. It is believed that exercising a validated human model is an inexpensive and efficient way to examine potential injury mechanisms. In some cases, this can provide insight into the design of subsequent laboratory experiments.Copyright

Numerical Analysis of the Biomechanical Characteristics and Impact Response of the Human Chest

The mass density, Young’s modulus (E), tangent modulus (Et ) and yield stress (σy ) of the human ribs, sternum, internal organs and muscles play important roles when determining impact responses of the chest associated with pendulum impact. A series of parametric studies was conducted using a commercially available three-dimensional finite element (FE) model, Total HUman Model for Safety (THUMS) of the whole human body, to determine the effect of changing these material properties on the impact force, chest deflection, and the number of rib fractures and fractured ribs. Results from this parametric study indicate that the initial chest stiffness was mainly influenced by the mass density of the muscles covering the torso. The number of rib fractures and fractured ribs were primarily determined by E, Et and σy of the ribcage and sternum. Similarly, the E, Et and σy of the ribcage, which is defined as the bony skeleton of the chest, and sternum and E of the internal organs contributed to the maximum chest deflection in frontal impact, while the maximum chest deflection for lateral impact was mainly affected by the E, Et and σy of the ribcage.Copyright

A Parametric Study on Gravity-Induced Brain Shift Using a Three-Dimensional FE Model of the Human Brain

The mass density, shear modulus, bulk modulus and decay constant of brain tissues play important roles when calculating gravity-induced brain shift during brain surgery. A parametric study was conducted to determine the effect of these properties on gravity-induced brain shift, using a three-dimensional (3D) finite element (FE) model of the human brain that was developed at Wayne State University (WSU). Results from this parametric study indicate that the magnitude of brain shift altered significantly due to changes in a combination of the shear modulus and bulk modulus of the brain.Copyright

Numerical Investigation of Injury Biomechanics of the Thorax and Lower Extremities Under Different Restraint Systems Using Wayne State University Human Model

Although newer vehicles are equipped with airbags and there is a high percentage of vehicular occupants who are wearing seatbelts, injuries to the thorax and lower extremities accounted for 33% of all occupant injuries. Moreover, when considering the frequency of injuries with a severity on the Abbreviated Injury Scale (AIS) of 3 to 6 (heretofore referred to as AIS 3+), injuries to the chest and lower extremities accounted for a total of approximately 43% of all occupants with these injuries. Consequently, a more detailed study of injury risks to these two body regions is called for. A series of numerical studies has been conducted to simulate a frontal crash using a three-dimensional (3D) finite element (FE) whole body human model representing a 50th percentile male to estimate the injury risks to the thorax and lower extremities. Three different combinations of restraint systems were simulated along with the no restraint condition. Results indicate that injury risks to the thorax were much higher in an unrestrained driver compared to those of a driver restrained by either the airbag only, three-point belt only, or combined airbag and three-point belt condition. On the other hand, injury risks to the lower extremities in occupants without any restraint or airbag only were greater than those restrained by three-point belt only or combined airbag and three-point belt. The combined airbag and three-point belt system simulated in this study showed the lowest injury risks to the thorax and lower extremities.Copyright

A Parametric Study on Injuries to the Knee-Thigh-Hip Complex Using a Three-Dimensional FE Model of the Human Body and Knee Airbag

Although extensive biomechanical studies have been conducted on the knee-thigh-hip (KTH) complex to improve our understanding of its injury mechanisms, injury risks to the KTH complex due to the knee airbag have not been characterized so far. In this study, a detailed three-dimensional (3D) finite element (FE) model of a 50th percentile male KTH complex was integrated into a previously developed torso model and used to simulate frontal crashes with and without a generic knee airbag. The FE model of the KTH complex explicitly represented the ilium, ischium, sacrum, articular cartilage, femoral head, femoral neck, femoral shaft, femoral condyles, patella, patella tendon, and the rest of the leg. The Design of Experiments (DOE) method based on Taguchi’s approach was adopted in this study. The three vehicular interior design parameters considered were knee airbag pressure, knee airbag volume and impact speed. Each of these parameters were assigned three design levels to simulated to predict their respective effects on the potential of KTH injury in a frontal impact.Copyright

Advanced Human Modeling for Impact Simulation

This paper summarizes component models of the human body, from head to foot, developed at WSU over the last decade. All of these models were validated against global response data obtained from relevant cadaveric tests. This report summarizes the capabilities and limitations of these models and points the direction for future developments.Copyright