TECHNOLOGY AREAS: Air Platform, Weapons

ACQUISITION PROGRAM: Joint Strike Fighter

OBJECTIVE: Develop an automated expert based approach to accurately represent the details of a structural assembly, including fastener type, hole geometry and detailed parts.

DESCRIPTION: Aircraft structural optimization requires significant detail in the analysis models used to evaluate strength and fatigue capabilities. The aerospace industry has seen great improvement in the design and manufacturing of parts and assemblies due to advances in CAD geometry and automated manufacturing. On the analysis front, current pre-processor tools are improving in their automation of meshing a single part. However, the ability to automatically create a high fidelity analysis model of structural assemblies does not exist. During analysis, detailed models of assembled structures that include the full geometry are not attempted. Instead, simplified and inadequate models of the assembly are used, resulting in inaccurate representations of the effects on the global structure and highly inaccurate analyses. The deficiencies with the current analytical approaches can be witnessed in an array of full scale test programs with major premature failures resulting from the unexpected failure at assembly locations deemed "non-critical" during structural analysis. Such an approach leads to costly retrofits and/or program delays. The ability to perform accurate structural analysis on assembly locations the first time would allow development programs to proceed on schedule without the interruptions created by test failures.

Innovative structural simulation algorithms are sought to automate the geometry integration and allow structural joints to be represented in multiple levels of detail appropriate for the target of a given analysis. A tool is sought that could be applied organically on existing programs and by OEMs on new and existing programs to allow precise simulation of structural assemblies to better understand design details and impact of repairs and detail changes. The linkage between design/geometry and analysis should be maintained from the top level model down to the lowest level detail model. This may allow for full comprehension of the effects of design changes on all aspects of a structures performance prior to building a single part. This innovation should provide the ability to perform iteration of a design leading to optimization of structural details for efficient and maintainable designs.

PHASE I: Develop and conceptually demonstrate the proposed approach to automating the simulation of aircraft structural joints in structural analysis models.

PHASE II: Develop the algorithm(s) required to produce the prototype software tools. Demonstrate use of the prototype tools through creation of an analytical model of a selected structural component and determine its structural response under test conditions. Perform structural testing on the selected component to validate the developed structural simulation tools.

PHASE III: Implement the validated algorithm(s) and process in a released version of software. Apply this analysis tool to structural analysis applications on aircraft program structural improvement and development efforts.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: This structural analysis algorithm and process as implemented in the structural simulation software will be directly applicable to all commercial aerospace developers. The ability to perform accurate structural analysis the first time allows development programs to proceed on schedule without the interruptions created by test failures. Additionally, reliability/repairability issues can be highlighted and addressed in the design phase rather than later when the cost to fix the problem is significantly escalated.

REFERENCES:
1. J. Bortman and B. A. Szabo, Nonlinear models of fastened structural connections, Computers and Structures, 43, 909-923 (1992).

2. Lambert, John C.; Merritt, Brent J. Automated Stress Analysis - Reducing Stress Analysis Time by an Order of Magnitude, MSC 1995 World Users' Conf. Proc., Paper No. 41, May, 1995.

3. M.W. Hyer, "Effects of Pin Elasticity, Clearance, and Friction on the Stresses in a Pin-Loaded Orthotropic Plate," Virginia Polytechnic Inst. & State University, VPI-CCMS-85-04, March 1985.

4. AD-TR-61-153, "Load Deflection Characteristics of Joints," Appendix B, p. 158-170.

KEYWORDS: Structural Simulation; Structural Analysis; Structural Assembly; Fastener Analysis; Joint Analysis; FEM

TPOC: (301)342-8509
2nd TPOC: (301)342-9337