TECH FOCUS AREAS: Biotechnology Space TECHNOLOGY AREAS: Bio Medical; Air Platform OBJECTIVE: This topic will focus on development and validation of a high-fidelity DoD-defined 5th percentile female finite element human body model for use in the evaluation of aircraft safety system performance and injury prediction during high dynamic loading events. DESCRIPTION: The Airworthiness process for aircraft safety systems and aircrew flight equipment safety evaluations requires data specific to the likelihood of injury of both large male and small female occupants. Historic methods for acquiring these data includes the use of USAF-modified hybrid III manikins undergoing a series of specific high dynamic loading events while collecting data on the manikin response for evaluation. Not only is the required testing extremely costly but the facilities required to perform the tests are few, resulting in difficulties meeting program schedules and ultimately a delay in providing capabilities to the warfighter. Advancements in finite element modeling and the ability to accurately model human interaction within environments has led to an increased use of such methods during the development process of various system types. The most complex of these models utilize magnetic resonance imaging (MRI) and computerized tomography (CT) imaging techniques to develop subject specific computer aided design (CAD) geometries of all major organs, bones and subject musculature. From these high-fidelity CAD models, finite element meshes are derived and individual components combined using various techniques to create the detailed human body model. Consisting of upwards of 3 million nodes and elements, these models are capable of providing insight into things from lower extremity fractures to head injuries and many things in between. The primary driver for the development of these models for safety evaluations, however, is the automotive industry, and with differing loading cases as well as certification criteria, there are still gaps if these are to be utilized for aircraft development. Mainly, the primary focus for human body model development thus far has been on high fidelity 50th percentile male models. While there have been small efforts looking into female human body model development as well as morphing existing 50th percentile male models to various anthropometries (5th through 95th percentile males), there has not been an extensive effort to directly generate a high-fidelity DoD defined 5th percentile female (103 lbs, Joint Primary Aircraft Training System Case 7 anthropometry) model and validate that model for aerospace level loading in the Gx, Gy and Gz directions. Not only would the development of such a model aide in the development and evaluation of new aircrew flight equipment and safety systems by reducing the cost and time required for certification, but it also directly supports the current Air Force Acquisition (SAF/AQ) initiative for digital engineering, the Biomedical and Air Platform Technology Areas, as well as the Biotechnology Technology Focus area. PHASE I: For the Phase I effort, contractors shall develop and execute a plan for establishing end user requirements and develop a proof-of-concept model to illustrate functionality. The proof-of-concept model should incorporate geometries generated directly from a DoD defined 5th percentile female human body. The level of detail desired in the model should be determined through discussion with the end user and any simplifications to tissue morphology, interactions and/or connections should be agreed upon before implementation in the model. The model should demonstrate realistic joint motions, hard/soft tissue connections and tissue response in end user specified loading scenarios. Validated material properties shall be used for all materials being modeled as defined in related literature. At the conclusion of the effort, a functional version of the model shall be delivered to the end user along with a perpetual license for operation, if required. PHASE II: Contractors awarded a Phase II shall mature their 5th percentile female human body model to include active musculature throughout and validate the model response against human subject and cadaver data for both the active and passive muscle states, respectively. Requirements for validation should be discussed with the end user and the data utilized for comparison agreed upon. The model should demonstrate the ability to accurately predict gross kinematic response during defined loading events such as aircraft hard landings, crash and occupant ejections. The model should also provide the ability to further investigate localized forces/moments and accelerations in regions of interest defined by the end user and the ability to utilize that data in the injury predictions equations provided by the USAF. The environment chosen to house the model shall contain a graphical user interface (GUI) that allows for quickly modifying model position to adjust for different seated and standing postures. The model shall also contain the ability to incorporate interactions with external structures, such as aircraft crew member seats and/or ejection seats. At the conclusion of the effort, a validated, functional 5th percentile female model with active and passive musculature along with a GUI to enable model re-posturing/repositioning shall be delivered to the end user along with a perpetual license for model operation, if required. PHASE III DUAL USE APPLICATIONS: Phase III awardees shall build upon their Phase II 5th percentile female model to expand model fidelity and functionality. The GUI shall also be expanded to allow for easy creation of critical aircrew restraint systems, such as standard aircrew harnesses and lap belts, as well as modifications to the occupant environment. The final deliverable will contain a validated 5th percentile female finite element model with the ability to model active and passive musculature. A supported GUI will be provided to enable easy re-posturing of the model as well as generation of restraint systems and additional structures, such as seats and standard aircrew flight equipment of interest, to include aircrew helmets and helmet mounted displays. Typical scenarios agreed upon by the contractor and end user shall be pre-programmed into the GUI for quick setup and/or the appropriate setup files provided for an equivalent ease of use. At the conclusion of the effort, a functional version of the model shall be delivered to the end user along with a perpetual license for operation, if required. This capability will provide the ability to evaluate the injury potential for high dynamic loading scenarios specific to small female occupants for use in evaluating new aircraft safety system design, aircrew flight equipment design, as well as existing safety system modifications. Potential avenues for transition include Air Force, Navy and Army Aircraft Program Offices for use in Safe-to-Fly evaluations as well as any commercial air and spacecraft manufacturers that have requirements related crash safety standards for certification. REFERENCES: Brinkley J.W., 1985, Acceleration Exposure Limits for Escape System Advanced Development, SAFE Journal, Vol. 25, No.2, 1985; Nichols J.P. Overview of Ejection Neck Injury Criteria, Proceedings of the 44th Annual SAFE Symposium, pp. 159-171, Reno NV, Oct 2006; EZFC Crew Systems Bulletin 16-001. November 2016; Iwamoto M. Development of a Finite Element model of 5th Percentile Female with Multiple Muscles and its Application to Investigation on Impact Responses of Elderly Females. 23rd International Technical Conference on the Enhanced Safety of Vehicles, Seoul, South Korea, 2013; Davis, M. Development and Full Body Validation of a 5th Percentile Female Finite Element Model. January, 2017; Osth, Jonas. The VIVA OpenHBM Finite Element 50th Percentile Female Occupant Model: Whole Body Model Development and Kinematic Validation. IRCOBI Conference, 2017; Gayzic, Francis. Development of a Full Human Body Finite Element Model for Blunt Injury Prediction Utilizing a Multi-Modality Medical Imaging Protocol. January, 2012. KEYWORDS: finite element modeling; human body modeling; 5th percentile female; crash safety; aircraft ejection; head injury; neck injury; spine injury; ejection injury
