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The use of digital human modeling in optimal injury prevention and reduction was studied and is described in this paper. The optimal injury prevention and reduction was treated as an optimization problem of a biomechanical system consisting of the safety unit and occupant. The issues of incorporating the Articulated Total Body (ATB) model, a digital human modeling tool, into an optimization process for the modeling and simulation of the biomechanics of the occupant were addressed. Modifications were made on the ATB source code, turning it into a subroutine that can be used in optimization. General considerations were also given to the creation of an interface that uses ATB as an analysis tool in the approximate optimizations. As a practical engineering application, the optimization of the ejection seat cushion impact properties for the minimization of the risk of spinal injuries was investigated.

The performance of inflatable toepan padding for mitigating lower limb injuries was investigated. A rigid multi-body model was used to describe the scenario of an occupant in an automobile frontal crash with toepan intrusion. The emphasis was placed on the lower limb responses during impact. The interaction between the lower limbs and the inflatable toepan padding was described by the contact between the feet and the load distribution plate of the padding. Computational simulations were performed to analyze the effects of the controlled motion of this plate on the lower limb impact responses.

This paper presents efforts made on the computational modeling and simulation of out-of-position occupant-airbag interaction. The airbag was modeled using the finite element method with LSDYNA. Static airbag deployment tests were performed to support and validate computational modeling efforts. A 50-segment rigid body model was developed for the 5th percentile Hybrid-III female dummy using the Articulated Total Body (ATB) model program. This occupant model allows for the detailed simulation of occupant responses in several body regions. The system that describes out-of-position occupant-airbag interaction in frontal crashes, including airbag, occupant, and major vehicle structures, was modeled through the integration of the rigid body occupant model with the finite element airbag model using the function provided by LSDYNA. The biodynamics of the occupant-airbag interaction were simulated for unbelted occupant sled impacts and two out-of-position static deployment impacts.

Critical in vehicle crash simulations, human body data sets include mass, moments of inertia (MOIs), and ellipsoid size for each body segment, and location and resistive torque properties for each joint. The Generator of Body Data (GEBOD) program generates these human data sets for use in multibody programs. The objective of this study was to validate GEBOD estimates by directly measuring whole-body inertial properties of 69 volunteers and comparing the results with values calculated by the Articulated Total Body (ATB) model using GEBOD data sets. While the predicted whole-body center of gravity (CG) averaged within 1 cm of the measured values in the horizontal direction, vertically the errors were much larger. The predicted principal MOI were consistently 5%-30% lower than the measured values.

The capability to predictively simulate occupant dynamics in vehicle rollover crashes using the Articulated Total Body (ATB/CVS) model was validated using the results of two controlled automobile rollover crash tests. The ATB model requires the occupant's inertial, geometric, and resistive joint torque properties, the vehicle interior geometry and motion, the contact characteristics for the occupant and vehicle interactions, and the seat belt characteristics. The validation was done by first simulating one test and adjusting the contact and belt properties to obtain good comparison with the test results. Then subsequent tests were simulated using the same properties, but changing only the input vehicle kinematics. Each occupant simulation used the standard Hybrid III data set and measured vehicle interior geometry. The vehicle kinematics were generated by simulating the vehicle dynamics with the ATB model. In one rollover, roof crush significantly affected the occupant's motion.

To demonstrate the Articulated Total Body (ATB) model's capability to predict complex rollover accidents, a rollover accident was selected from the National Accident Sampling System (NASS) and simulated. This paper focuses on the simulation of the vehicle's dynamics which can in turn be used to specify the vehicle motion for occupant simulations. The selected accident case involved a pickup truck, crashing at high speed and completing three rolls. The pickup truck was modeled as a single rigid segment with fifteen contact hyperellipsoids rigidly attached to it. These hyperellipsoids were sized and positioned to approximate the exterior surfaces of the pickup truck. The force-deflection functions were defined based upon previous simulations of rollover tests. The initial conditions were defined to match the data in the NASS accident report as closely as possible.

The objective of this study was to mathematically model several proposed vehicle glazing materials using derived force-deflection characteristics, validate the models' dynamic behavior, and use the resulting glazing models in simulations of occupant dynamics during vehicle rollover. Simulations were performed with the three-dimensional, multibody dynamics program, the Articulated Total Body (ATB) model. The contact characteristics of side windows of tempered glass; polymethyl methacrylimide, also referred to as PMMI; and polycarbonate; as well as windshields from Ford Tempos and Jeeps, were developed from headform impact tests. These characteristics were first validated by performing simulations of the headform impact tests, and were then included in rollover simulations. Previously validated simulations of belted driver and unbelted passenger dynamics during an actual rollover accident were used as the baseline simulations.

Computer simulations of occupant dynamics are ideal for conducting parametric studies evaluating injury countermeasures. A rollover accident was selected from the National Accident Sampling System (NASS) for simulation to validate the Articulated Total Body (ATB) model's capability to predict occupant dynamics during rollover accidents and to gain insight into injury mechanisms. Simulations of both the driver and passenger occupants which may be used in future countermeasure studies are performed. In the selected accident, a pickup truck rolled multiple times, the belted driver had minor injuries and the unrestrained passenger was ejected with fatal injuries. The body properties for both occupants were obtained using the Generator of Body Data (GEBOD) program based on their weights, heights, and sexes. The interior configuration of the vehicle compartment was modeled based on measurements taken from another vehicle of the same model.

Sophisticated computer simulation of human response during various violent force exposure situations requires not only the validated programs, but also high quality databases, especially the data sets that characterize human body structures. Although anthropometric surveys and stereophotometric studies have been performed to create geometric and inertial property databases for the human body, there have been limited efforts on establishing the joint kinematics and resistive torque data sets. This paper presents the development, implementation, and validation of the human articulating joint model parameters for crash dynamics simulations. Measured human joint data on the voluntary range of motion and passive resistive torques were used to mathematically model the shoulder, elbow, hip, knee, and ankle joints.

Side-facing seats are present in a variety of aircraft. During impact, these seats load the occupants in a different manner than typical forward-facing seats, namely the occupants are exposed to a lateral impact. In order to minimize injury during a crash, it is necessary for the occupants to prepare themselves and be situated in a position for maximum protection. In an effort to understand occupant initial position in a side-facing seat, a 3-D rigid-body model was developed of a side-facing seat configuration with three occupants, using the Articulated Total Body (ATB) program. The occupants were seated side-by-side in webbed troop-style seats, and each occupant was restrained by a lap belt. Three different initial occupant positions were studied, and each of the three occupants in a given simulation were seated in the same position. A 10 G lateral pulse with an approximate duration of 200 ms was applied to the vehicle.