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As accurate measuring of head accelerations is an important aspect in predicting head injury, it is important that the measuring sensor be well-coupled to the head. Various sensors and sensor mounting schemes have been attempted in the past with varying results. This study uses a small, implantable acceleration sensor pack in the ear to study impact coupling with the human skull. The output from these ear-mounted accelerometers is compared to laboratory reference accelerometers rigidly attached to the skull of two cadaveric head specimens for both low-amplitude oscillatory tests and high-amplitude impact drop tests. The combination of sensor type and mounting scheme demonstrates the feasibility of using ear mounted sensors to predict head acceleration response. Previously reported progressive phase lag was not seen in this study, with the comparison between ear mounted accelerometers and rigidly mounted head accelerometers ranging from very good to excellent.

The exploration of impact biomechanics via data mining is investigated in this paper. The issues that are particularly pertinent to the use of data miming technology on biomechanics databases are addressed. These issues include (a) relationship between the manikin tests and human tests; (b) extension from lower impact, non-injurious conditions to high impact, injurious conditions; (c) test data versus simulation data; (d) input-output categorization; (e) input-output abstraction and representation; (f) topics for new knowledge discovery; and (g) user scenarios. Technical treatments and considerations are made on the unique characteristics and requirements involved in the biodynamics data mining. They are (a) mixture of classification and numerical prediction; (b) isolated feature space; (c) multiple dependent variables; (d) high dimensionality; (e) algorithm and parameter selection; and (f) scalable data integration and knowledge discovery.

The comfort of seat cushions has become important in many of today's high-performance USAF fighter and tactical aircraft. Experimental investigations have found that there exists a strong relationship between the human subjective discomfort rating for a seat cushion and the pressure distribution on the interface between the cushion and the buttocks. For the analysis of the contact pressure distribution, a finite element model of the human buttock was developed. The model consists of a detailed geometric description of the skin, soft tissues, and bony structures. The development of the model is described in this paper, which includes source data selection, bony structure modeling, joint modeling, soft tissue modeling, and pelvis shape morphing.

An injury risk function defines the probability of an injury as a function of certain measurable or known predictors. In this paper, wavelet analysis is employed for the non-parametric estimation of injury risk functions. After a brief introduction of the wavelet theory, the representation of density function by wavelet series is given. A procedure for the estimation of density function is described. The risk function estimation for right-censored data is investigated by introducing hazard rate function and its wavelet estimator. The use of the developed method is illustrated in a case study, where two sets of data are used: simulation data with known distribution and censoring information, and thoracic impact testing data, which are assumed to be right- censored. Comparisons are made between the wavelet-based approach and the empirical Kaplan-Meier non-parametric method.

Modeling and simulation of complex biomechanical systems can be developed to provide insight into the loading of otherwise immeasurable conditions. Ejection from an aircraft is a highly dynamic event with a risk of injury during the entire sequence. During one of the phases of ejection, spinal compression injury is a definite possibility and test manikins are used to asses this risk. However, care must be taken before accepting the relationship between the measured load in a manikin an the assumed load in a human. Human impact tests are often conducted to asses the biodynamics at a sub-injury level. Correlating these human biodynamics with manikin dynamics, can provide this relationship. To complete this correlation, modeling and simulation can be used to augment the available human test data so that the parameters of interest can be calculated. To this end, a rigid body dynamics model was constructed to represent a vertical impact for both humans and manikins.

In automobile frontal impact, given the vehicle motion and the interior free space for the occupant’s excursion, what are the optimal characteristics of restraint systems for the minimization of the peak occupant deceleration? In this paper, based on a lumped-parameter model of the occupant-vehicle system, the optimal kinematics of the occupant in frontal impact is investigated first. The optimal characteristics of passive restraint systems are then investigated in detail for three types of vehicle crash pulse: optimal pulse, constant deceleration pulse, and half-sine pulse. Optimization of the characteristics of active and pre-acting restraint systems is addressed. It is found that the optimal kinematics of the occupant in frontal impact is such that the occupant moves at a constant deceleration.

Two series of tests were conducted to investigate the performance of ejection seat cushions for safety and comfort, respectively. In the safety study, seven operational and prototype cushions were tested on the vertical deceleration tower, where the cushions were placed between the seat pan and the occupant (a 50th percentile Hybrid III manikin) and subjected to +Gz impact at 8, 10, and 12 g, respectively. In the comfort investigation, twenty volunteer subjects (12 females and 8 males) with a range of anthropometry were tested on four operational and prototype cushions over eight-hour durations. The safety performance of a cushion is evaluated by the impact transmissibility from the carriage acceleration to the peak lumbar load, whereas the sitting comfort performance is assessed in terms of the peak contact pressure and subjective survey data.

Problems with the validation of biodynamics modeling and simulation are addressed in this paper. The wavelet analysis is introduced to the point-point comparison, a way of validating biodynamic responses. Biodynamic responses from the actual tests and the model simulations are decomposed on the wavelet or wavelet packet basis. The agreement between the simulation results and test data is evaluated in terms of the signal energy distributions and the correlation functions, which are determined from the wavelet or wavelet packet decompositions. Metrics are developed for the quantitative evaluation. The multi-resolution analysis provided by the wavelet decomposition can be used to effectively handle the model validation at different levels of accuracy and detail. The use of the methods and metrics is illustrated through the validation of a finite element automobile crash model.

Validation methods for the finite element automobile crash modeling were developed using wavelet analysis. Based on the decompositions on wavelet packet bases, two types of signal energy distributions were established with respect to: (a) frequency index, and (b) time position and frequency index, which provide a common basis for the comparison between the simulation results and the test data in terms of the variation of amplitue with respect to frequency and time. Based on the decompositions on wavelet bases, correlation analysis was used to evaluate the differences in pulse shape and peak timing between the simulation results and the test data for the gross motions and major impact pulses. The use of the methods was illustrated in the validation of a 1997 Honda Accord finite element model for full frontal impact.

A methodology was developed for predicting the human response from ATD (Anthropomorphic Test Device) tests or for improving the biofidelity of the ATD response. The ATD response and human response are considered as the output of a black box system, from which the relationship between the ATD tests and human tests was established using wavelet analysis. Based on the decompositions of both responses on a wavelet packet basis, a mapping matrix is built after executing a procedure that includes de-noising and compression, energy distribution analysis, correlation analysis and regression analysis, and spectral coherence analysis and transfer function analysis. With the mapping matrix, an ATD response is modified or reconstructed into the corresponding human response. The practical use of the methodology was illustrated in the analysis of a series of lateral impact tests conducted on a horizontal impulse accelerator with an ATD and human volunteers as the test subjects.

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.

Investigations were made on computational analyses of ejection seat cushions, which include the characterization of the impact properties of ejection seat cushions, computational modeling of an ejection seat cushion system using a rigid multi-body dynamics program, parametric optimization of the cushion impact properties, and global sensitivity analysis of the safety performance of a cushion to its impact properties. The results indicate that computational analyses can be used to effectively evaluate and improve the cushion performance in the prevention and reduction of spinal injuries.

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.

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.

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.