SwRI will be exhibiting at the ASIP Conference, booth no. 8.
Southwest Research Institute® (SwRI®) is an independent, nonprofit, applied research and development organization that has supported Aircraft Structural Integrity Programs for more than 40 years. Our work in the field spans the entire range of ASIP tasks, including providing in-flight recording of aircraft loads; static strength, finite element, and damage tolerance analyses; inspection and repair option development; corrosion prevention and control; and developing the digital thread processes to document all of that for the fleet. We provide a complete range of testing, such as detailed metallurgy and fractography, material property tests, and full-scale aircraft static and fatigue tests. We also develop NASGRO®, the most widely used fracture mechanics and fatigue crack growth software in the world, which includes fracture mechanics models for more than 100 different structural configurations. Our array of ASIP engineering services supports all types of aircraft structures.
Please join us for the following presentations:
Monday, Dec. 2
1:00 p.m. – 5:00 p.m.
Training
“Practical Risk Analysis Using PROF,” Laura Hunt
PROF is a widely-used software tool for conducting probabilistic structural risk analysis of USAF weapon systems. This course will demonstrate how to properly build a PROF input using the results of a damage tolerance analysis and inspection information, then interpret the single flight probability of failure (SFPOF) results for risk analysis. The course will review best practices from the PROF manual, MIL-STD-1530, and tips and tricks from the instructors’ own experience. Advanced topics include EIDS/IFS distribution development, sensitivity analysis, Freudenthal vs. Lincoln SFPOF methods, and continuing damage analyses. About the instructors: Laura Hunt, P.E. is a Lead Engineer at Southwest Research Institute (SwRI) in San Antonio, TX. She has fifteen years’ experience conducting probabilistic risk analysis for the USAF including over ten years leading T-38 risk analysis efforts with PROF. In addition to risk analysis, she aids in damage tolerance analyses and fleet management studies for the T-38 and A-10 aircraft. Dr. Marcus Stanfield is a Lead Engineer at SwRI onsite at Hill AFB. He also performs risk analysis with PROF, teardown studies, damage tolerance analysis, and designs and analyzes structural components and modifications.>/p>
Tuesday, Dec. 3
2:30 p.m. – 3:00 p.m.
Session
“Evolving Discontinuity State for the F16 Falcon and Successful Sustainment Methodologies,” Paul Clark
The relevancy of materials and processes and how these relate to the idea of rogue flaws is critically important to airworthiness and structural integrity. This presentation will introduce the concepts of an Initial Discontinuity State (IDS) as well as the Evolving Discontinuity State (EDS). An associated case study will relate to the F-16 Fighting Falcon and discuss sustainment challenges and successful fleet management for the Canopy Sill Longeron (CSL). The IDS of a design is mainly comprised of geometric discontinuities as needed for the part’s purpose, and includes manufacturing, assembly, and intrinsic microstructural discontinuities. The geometry tends to have the most significant contribution with features such as radii, open holes, holes filled with fasteners, etc. Manufacturing and assembly also can contribute significantly to the IDS. Finally, the microstructure generally has the smallest sized discontinuities yet the most populous. The discontinuity state can change over time; it evolves with time, usage, maintenance, general wear, and degradation. This is referred to as the Evolving Discontinuity State (EDS) and as such, EDS attempts to capture the changing IDS as it evolves with time, usage, and maintenance. This presentation will focus on the CSL of the F-16 Fighting Falcon; it will provide examples of the IDS and show how EDS must be considered through the sustainment process for successful ASIP fleet management.
Thursday, Dec. 5
10:00 a.m. – 10:30 a.m.
Session
“A10 Nose Landing Gear Door Hinge Failure Assessment,” Michael Worley
The A-10 System Program Office (SPO) engineering team performed a failure assessment and damage tolerance analysis (DTA) of the hinge fitting for the nose landing gear (NLG) aft door. This was done in response to an NLG door departure in flight during a routine training sortie operating inside the normal operational envelope of the aircraft. An analysis team was tasked to determine the root cause of failure and subsequent inspection requirements for the hinge fitting. The presentation demonstrates how organic Air Force capabilities are leveraged to perform failure analyses, finite element modeling (FEM), and multi-point crack growth analyses to validate results and help define inspection criteria for fleet management. The fracture surface revealed multiple crack origins and heavy corrosion which obscured striation data in the region believed to be the primary crack. The materials lab at Hill AFB was able to perform striation counting at multiple points along the secondary fracture surface to correlate with analysis. Finite element analysis (FEA) was used to model stress fields in the part at the crack location(s), leveraging legacy stress analysis reports to help determine appropriate loads. Because of the complicated geometry and loading of the hinge, a custom multi-point fracture mechanics model was utilized to correlate the crack growth rates in the analysis to the available measured rates on the failed hinge. Then a second multi-point fracture mechanics model was ultimately utilized to generate crack growth curves from a crack originating at the higher-stress primary crack location. The resulting crack growth curves, along with the applicable detectable flaw size, will be used to manage fleet inspection requirements thus reducing the risk of future in-flight failures. Additionally, this evaluation informs the SPO as to how service usage might align or misalign with legacy design assumptions.
For more information, please contact Luciano Smith.