# A Female Multi-Body Head-and-Neck Model and Validation for Rear Impact Simulations
###### Abstract
[25] built a finite element model representing the 50 th percentile female head and neck comprising a ligamentous cervical spine with a rigid head and Hill-type muscle elements. The rear-impact simulations did not incorporate muscle activation. Human head-neck models must provide biofidelic responses to be effective. Therefore, these models must be validated against volunteer responses [26]. [PERSON] et al. [27] determined the responses of both genders in rear impact tests using volunteers. [PERSON] et al. [17] also examined the dynamic kinematic responses of female and male volunteers in equivalent rear impact conditions. In light of all this information, the differences due to gender have been examined and problems addressed for about two decades. Most previous studies were based on the 5 th percentile female, which was scaled from male models. Therefore, the female population is not represented efficiently, and the injury risk for females is still a great concern in rear impact conditions. In the last seven years, state-of-the-art female models have been developed comprising 50 th percentile female finite element human-body models and 50 thpercentile female physical dummies. These female models are aimed to be used primarily for rear impact testing, as described in the following four paragraphs. [PERSON] [28] worked on the 50 th percentile female finite element human-body model ViVA OpenHBM built at the Chalmers University of Technology, Gothenburg, Sweden. ViVA OpenHBM model is an average female with a stature of 161.6 cm and a mass of 60.8 kg. In his research, different control strategies in muscle activation were studied together with the optimization of control gains to match volunteer response data obtained from the Japan Automobile Research Institute, Tsukuba, Ibaraki, Japan (JARI) rear impact tests [29]. Although the height of the volunteers was similar to that of the ViVA OpenHBM model, the volunteers were 12 kg lighter, thus, the volunteers did not exactly represent an average female. Furthermore, only two volunteers were available to validate the female model, which was a shortcoming. There were considerable differences between the model and volunteer displacements; the slopes of the displacement curves were not in agreement as well. Hence, the female model needed improvement. In a follow-up study [30], the ViVA OpenHBM female FE model was improved by better tuning the parallel damping element in the Hill muscle model; consequently, they obtained better agreement with the volunteer kinematics. In this follow-up study, the aim was to validate the female model against volunteer data at three different severities; however, they did not present the displacements of the volunteers versus the female model at the highest severity test with a delta velocity of 10 km/h. In the latest research on EvaRID [31] (which is a finite element dummy model for the average female), four different real-world crash pulses were applied to the same seat in order to investigate the differences in the responses of EvaRID and BioRID II FE models. In this reconstruction of four different accidents, the injury criteria values were lower for EvaRID in contrast to BioRID II, even though the female occupants had experienced more severe whiplash symptoms than the male occupants in the corresponding real-world accidents. It was concluded that the neck and torso of BioRID II were more susceptible to extension because of their size and mass; hence, it was suggested that lower injury criteria thresholds should be used for EvaRID. This study has limitations, considering that the investigation of only four accident reconstructions might not be enough to draw general conclusions. In the real-world case, the posture of the occupants with respect to the seat could vary. A prototype physical dummy called BioRID P50F has recently been designed [32] to represent an average female based on the body parts of the average male dummy BioRID II.