Verified and Validated Software for Three-dimensional (3-D) Fatigue Crack Growth and Stable Crack Extension

Award Information
Agency: Department of Defense
Branch: Air Force
Contract: FA8650-09-M-3913
Agency Tracking Number: F083-175-1487
Amount: $100,000.00
Phase: Phase I
Program: SBIR
Awards Year: 2009
Solicitation Year: 2008
Solicitation Topic Code: AF083-175
Solicitation Number: 2008.3
Small Business Information
120 Kaminer Way Pkwy., Suite A, Columbia, SC, 29210
DUNS: 147794007
HUBZone Owned: N
Woman Owned: N
Socially and Economically Disadvantaged: N
Principal Investigator
 Hubert Schreier
 Chief Executive Officer
 (803) 926-7272
Business Contact
 Stephen McNeill
Title: Chief Financial Officer
Phone: (803) 926-7272
Research Institution
Development of a software tool capable of predicting crack growth in structures with complex geometries for accurate structural life predictions and residual strength assessment is proposed. The custom crack growth simulation tool, CRACK3D, will be used as the basic code for further development and implementation. First, further enhancement of the CRACK3D module for computational geometry and topology will be performed so that CRACK3D can handle most of geometric features present in modern aircraft structures. Second, CRACK3D will be modified to contain built-in advanced computing techniques, including high performance computing FORTRAN/C++ coding, parallel computation option for running on distributed memory system and shared memory systems. Third, the three-dimensional virtual crack closure technique, 3D VCCT, will be used to calculate stress intensity factors for complex crack geometries under arbitrary mixed mode loading conditions. Fourth, the alternate superposition-based method will be used to take into account the effect of residual stress on fatigue crack growth rates. This method is simple and relatively accurate. A crack closure based approach can also be implemented for improving the accuracy of the alternate superposition-based method if accuracy becomes a concern. Finally, experimental validation of the capabilities will be performed using either existing literature or simple coupon experiments. BENEFIT: Successful completion of the proposed effort provides the foundation for conversion of CRACK3D into a form that would provide AF personnel with an efficient and effective simulation tool for assessing selected flaw criticality. Specifically, the following results are anticipated. (1)A finite element formulation of VCCT with 10-noded tetrahedral elements, implemented in CRACK3D, for simulating three-dimensional crack growth using unstructured meshes. (2)A program module for re-meshing local regions around critical crack fronts and containing internal material boundaries, for modeling crack growth in multi-material structures. (3)A program module of computational geometry and topology for updating structural geometry and topology due to crack growth in structures with arbitrary, complex geometries.(4) A theoretical model and simulation methodology of fatigue crack growth in structures under mixed mode loading conditions, implemented in CRACK3D, for prediction of fatigue crack path under general loading conditions, and (5) An enhanced software package, CRACK3D, for calculation of stress intensity factors under mixed mode loading conditions and fatigue crack growth simulation, in addition to simulation of stable tearing crack growth. Taken together, completion of these developments provides the foundation for future Phase II efforts to make the 3D fracture analysis methodology both effective and relatively easy to use. The modified version of the software package CRACK3D is intended for commercialization at the completion of the Phase II effort. To achieve this goal, various strategies will be used to publicize CRACK3D and to demonstrate its capabilities and applications. Included in this effort will be development of a relatively easy-to-use interface to allow users to utilize the power of the methodology with minimal FE meshing effort.

* Information listed above is at the time of submission. *

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