Search Results

The Hybrid III family of dummies is used to estimate the response of an occupant during a crash. One recent area of interest is the response of the neck during air bag loading. The biomechanical response of the Hybrid III dummy's neck was based on inertial loading during crash events, when the dummy is restrained by a seat belt and/or seat back. Contact loading resulting from an air bag was not considered when the Hybrid III dummy was designed. This paper considers the effect of air bag loading on the 5th percentile female Hybrid III dummies. The response of the neck is presented in comparison to currently accepted biomechanical corridors. The Hybrid III dummy neck was designed with primary emphasis on appropriate flexion and extension responses using the corridors proposed by Mertz and Patrick. They formulated the mechanical performance requirements of the neck as the relationship between the moment at the occipital condyles and the rotation of the head relative to the torso.

The responses of the THOR and the Hybrid-III ATDs to head and neck loading due to a deploying air bag were investigated. Matched pair tests were conducted to compare the responses of the two ATDs under similar loading conditions. The two 50th percentile male ATDs, in the driver as well as the passenger positions, were placed close to the air bag systems, in order to enhance the interaction between the deploying air bag and the chin-neck-jaw regions of the ATDs. Although both ATDs nominally meet the same calibration corridors, they differ significantly in their kinematic and dynamic responses to interaction with a deploying air bag. The difference between the structural designs of the Hybrid-III's and the THOR's neck appears to result in significant differences in the manner in which the loads applied on the head are resisted.

Restraint systems play an important role in managing the energy of occupants during a crash event. Belt and airbag systems complement each other in order to gradually decelerate the occupant. However, the seating position of the 5th percentile female and 50th percentile male occupants forces the need to manage this energy in different ways. MADYMO simulation of a generic vehicle-restraint system with a driver side 5th and a 50th percentile Hybrid III dummy were done for a typical frontal impact. The belt system had a retractor/load limiter, but no pretensioner. The effect of airbag fabric porosity, inflation rate and seat belt load limiting ability were evaluated for both occupants. Parameters examined that affect system rebalancing to achieve the highest star rating were HIC and 3ms Chest acceleration.

While the Hybrid III anthropomorphic test device (ATD) family has experienced a lengthy period of development, and is an essential part of vehicle safety regulation, several issues associated with the ATD's head/neck design and the neck dynamic response due to airbag loading have been identified. As a result, the response of the Hybrid III neck under a number of airbag loading conditions could be an “artifact” of the ATD and not representative of the live human. One area of concern relates to the method of incorporating the human neck muscles into the neck response and how this affects the out-of-position (OOP) tests mandated in the new FMVSS 208. The results of a series of sled and OOP tests are presented in this paper to elaborate on the nature and the magnitude of the ATD's neck response “artifact”. In addition, the complication associated with balancing in-position and OOP requirements as a result of this “artifact” is highlighted.

The relationship of the airbag fire-distribution as a function of impact velocity to the airbag fire-time is studied through the use of an optimization procedure. The study is conducted by abstracting the sensor algorithm and its associated constraints into a simple mathematical formulation. An airbag fire objective function is constructed that integrates the fire-rate and fire-time requirements. The function requires the input of a single acceleration time history; it produces an output depending on the airbag fire condition. Numerical search of the optimal fire threshold curve is achieved through parameterizing this curve and applying a modified simplex search optimization algorithm that determines the optimal threshold function parameters without computing the complete objective function in the parameter space. Numerical results are given to show the effectiveness and potential difficulties with the automatic search scheme.

A statistical theory is used to quantify the amount of information transmitted from a transducer (i.e., accelerometer) to the air bag controller during a vehicle crash. The amount of information relevant to the assessment of the crash severity is evaluated. This quantification procedure helps determine the effectiveness of different testing conditions for the calibration of sensor algorithms. The amount of information in an acceleration signal is interpreted as a measure of the ability to separate signals based on parameters that are used to assess the severity of an impact. Applications to a linear spring-mass model and to actual crash signals from a development vehicle are presented. In particular, the comparison of rigid barrier (RB) and offset deformable barrier (ODB) testing modes is analyzed. Also, the performance of front-mounted and passenger compartment accelerometers are compared.

A comparison of the NHTSA advanced dummy and the Hybrid III is presented in this paper based on their performance in repeated sled tests under 3 different restraint systems. The restraint systems considered are: the airbag alone, the 3-point belt alone, and a combined use of the airbag and the 3-point belt. Various time-histories pertaining to accelerations, angular velocities, deflections and forces have been compared between the two dummies in order to study their repeatability. The Hybrid III appears to be more repeatable than the NHTSA advanced dummy in its response in one case, that of restraint with the 3-point belt alone. The response of the NHTSA advanced dummy in other two restraint modes, the airbag alone and the combination of 3-point belt and airbag, appears to be no less repeatable than that of Hybrid III in this series of tests.

Nij, a function of upper neck forces and moment, plays a dominant role in the vehicle's star rating under the new NHTSA NCAP front impact program. This is mainly due to an artifact in the mapping of the Nij into the “risk” value used in the star rating, and the fact that the neck region is not weighted appropriately to reflect its real world significance relative to the other body regions in the NCAP rating. New test data also show that compared with the 50th male driver Nij, the 5th female passenger Nij is significantly more challenging to contain and therefore it is more dominant in the star rating. This paper describes the Hybrid III dummy head and neck impact response and provides a method to determine the external force acting on the head. The force and its acting point on the head are determined from head acceleration, angular acceleration, and the upper neck forces.