Tribological and Manufacturing Technologies for Unmanned Aerial Systems

The objective of this work is to provide the scientific and technology advancements to support the deployment of unmanned aerial system in assisting Army operations, which requires the best integration of propulsion systems with fuel to accomplish missions in harsh operating environments, such as high altitude, low temperature, and low air density, as well as taking-off and landing in various ground, desert, and oceanic conditions. The current UAS propulsion systems use existing ground vehicle engines, not designed to operate at the environment and mission requirements that UAS needs to achieve the desired performance in terms of efficiency, service life, robustness and resilience. Fuel, any fuel available at the field, can cause significant wear and even pre-matured failure of the propulsion systems, especially to the pumps and valve systems because during pumping, no proper lubrication can be provided to prevent rubbing of the components. Several problems need to be solved, for example, prediction of the status of contact and lubrication at the pump rubbing interfaces, severity of wear, and degree of friction; methods to lower friction in the UAS propulsion system; methods to prevent wear of critical components; technologies to mitigate problems in the current UAS systems; maintenance measures to enhance the mitigation solutions; and technologies and materials to develop new and more compact propulsion systems with high reliability and efficiency. There also exists a great opportunity to redesign the propulsion system for UAS, away from the existing concept of turbo-charged engine used in ground vehicles, to lightweight the system and to provide better thermal management. Computational design and metal-based directed energy deposition (DED) of aluminum alloys are needed in this endeavor for rapid manufacturing new designs at low cost for evaluations. Furthermore, predictive and rapid multi-scale simulation of the DED process that links material structure to process parameters to final mechanical properties of parts made plays a key role for effective material and process design. Composites structure, including a hybrid structure consisting of polymer-based composites and light-weight metals, can contribute to the effort for lightweighting the system. The challenges in designing and fabricating those composites structure include the need for understanding and predicting the behavior of those composites structure under extreme load and environmental condition, including mechanical strength, creep and fatigue behavior. An integrated computational materials engineering approach will be used for addressing those challenges using predictive science and engineering. Northwestern University is well known for its tribology and catalysis, materials, design and manufacturing work, with faculty members honored by membership of national academies, top achievement awards and best paper awards from their corresponding professional society. Faculty and students have created software platform to simulate tribological behavior, DED process and composites engineering, and have developed unique experimental instrument. In this work, the advanced computational tools will be further developed and validated to meet the objective stated above.