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Impact and Penetration of Thin Aluminum 2024 Flat Panels at Oblique Angles of IncidenceThe U.S. Federal Aviation Administration (FAA) and the National Aeronautics and Space Administration (NASA) are actively involved in improving the predictive capabilities of transient finite element computational methods for application to safety issues involving unintended impacts on aircraft and aircraft engine structures. One aspect of this work involves the development of an improved deformation and failure model for metallic materials, known as the Tabulated Johnson-Cook model, or MAT224, which has been implemented in the LS-DYNA commercial transient finite element analysis code (LSTC Corp., Livermore, CA) (Ref. 1). In this model the yield stress is a function of strain, strain rate and temperature and the plastic failure strain is a function of the state of stress, temperature and strain rate. The failure criterion is based on the accumulation of plastic strain in an element. The model also incorporates a regularization scheme to account for the dependency of plastic failure strain on mesh size. For a given material the model requires a significant amount of testing to determine the yield stress and failure strain as a function of the three-dimensional state of stress, strain rate and temperature. In addition, experiments are required to validate the model. Currently the model has been developed for Aluminum 2024 and validated against a series of ballistic impact tests on flat plates of various thicknesses (Refs. 1 to 3). Full development of the model for Titanium 6Al-4V is being completed, and mechanical testing for Inconel 718 has begun. The validation testing for the models involves ballistic impact tests using cylindrical projectiles impacting flat plates at a normal incidence (Ref. 2). By varying the thickness of the plates, different stress states and resulting failure modes are induced, providing a range of conditions over which the model can be validated. The objective of the study reported here was to provide experimental data to evaluate the model under more extreme conditions, using a projectile with a more complex shape and sharp contacts, impacting flat panels at oblique angles of incidence.
Document ID
20160000816
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Ruggeri, Charles R. (NASA Glenn Research Center Cleveland, OH, United States)
Revilock, Duane M. (NASA Glenn Research Center Cleveland, OH, United States)
Pereira, J. Michael (NASA Glenn Research Center Cleveland, OH, United States)
Emmerling, William (William J. Hughes Technical Center Atlantic City, NJ, United States)
Queitzsch, Gilbert K., Jr. (Federal Aviation Administration Washington, DC, United States)
Date Acquired
January 14, 2016
Publication Date
April 1, 2015
Subject Category
Aeronautics (General)
Metals And Metallic Materials
Report/Patent Number
GRC-E-DAA-TN19892
E-19035
NASA/TM-2015-218484
DOT/FAA/TC-15/7
Funding Number(s)
WBS: WBS 544163.04.01.03.01.02
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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