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Published on: May 18, 2015
Validation of a Finite Element Ovine Thorax Model in the High-Rate Non-Penetrating Blunt Impact Environment
Juliette M Caffrey1, Grace K Liverett1, B Wade von Kleeck1
1Biomedical Engineering, Wake Forest University School of Medicine, Winston-Salem, NC 27101, United States.
Introduction:
The current safety standard, 44 mm maximum backface deformation, for high-rate non-penetrating blunt impacts (NPBIs) is based on preliminary data and does not account for differences in injury risk for different organs. Therefore, further studies are needed to develop a more robust understanding of the injury mechanism of NPBI and injury risk. Live animal testing allows for the quantification of injury outcomes from insult to injury; however, it is limited by instrumentation, time, and cost. Finite element modeling can overcome these limitations and assist in the interpretation of experimental results. This study sought to validate a finite element ovine thorax model (FE-OTM) against experimental data for high-rate NPBIs.
Materials And Methods:
The experimental testing consisted of 20 impacts with initial velocities of about 40 m/s, maximum impact depths from 20 to 60 mm, impact angles of 0 to 25 degrees from the spine normal in the caudal direction, and 2 different impactor head shapes. Each experimental test measured impactor displacement through high-speed video and axial strain on the impactor's shaft. Further analysis was used to determine the peak force, transferred energy, and imparted impulse. A subject-specific validation matrix was run on the FE-OTM v2.0 in which the model was scaled to match the gross dimensions of each experimental test, the impactor was aligned to match the impact angle, and the impactor's motion was defined based on the experimental displacement versus time trace.
Results:
The peak force, transferred energy, and imparted impulse were compared between the FE-OTM and experiments using cross-correlation and linear regression. The results found slopes of 1.03, 1.74, and 1.97 and R2 values of 0.92, 0.94, and 0.95 for force, energy, and impulse, respectively. The high R2 values indicated that the model has a strong linear relationship with the experimental results.
Conclusions:
Therefore, the model has been validated for high-rate NPBI impacts. Future work will use this model to develop organ specific strain-based injury metrics for high-rate NPBIs and expand model application to other environments.
