2021 Fiscal Year Annual Research Report
Assessment of short fatigue crack closure behavior in Ti-6Al-4V alloy using 3D imaged-based CPFEM simulation
| Project/Area Number |
21J12176
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| Research Institution | Kyushu University |
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Principal Investigator |
TUBEI Valary 九州大学, 工学府, 特別研究員(DC2)
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| Project Period (FY) |
2021-04-28 – 2023-03-31
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| Keywords | Fatigue / Short crack / Crack closure / 3D/4D observation / X-ray tomography |
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| Outline of Annual Research Achievements |
This study’s goal is to develop a crystal plasticity FEM (CPFEM) model that simulates short fatigue crack closure behavior based on real 3D crack morphology. The aim to understand closure mechanisms and how microstructure can be manipulated such that closure is enhanced hence realizing materials that are difficult to fracture.
So far, we have analyzed 3D crack growth and closure behavior and evolution with time (4D) using X-ray tomography. Crack growth was observed to vary with crack extension caused by evolution of crack morphology and its interaction with Ti-6Al-4V alloy phases (α and α+β) with distinct inherent crack growth resistance. It was found that inclined and overlapped crack segments which occurred mainly in α+β showed early crack closure and subsequently low crack growth rate. These results indicate that certain microstructure may promote the formation of a complex crack morphology which contribute to fracture resistance. Further analysis will be done using CPFEM simulations.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The main objectives of this study are:
1.To assess crack closure behavior in 3D using X-ray tomography: So far, data for assessing the relationship between local 3D crack growth and closure behavior has been acquired successfully. The data analysis has been completed and the results are currently being prepared for publication.
2.To develop an image based CPFEM model that simulates short crack closure in relation to the underlying microstructure. The aim is to understand how to control the closure mechanisms ultimately realizing materials that are difficult to fracture: Currently the crack and microstructure model is being prepared to carry out the simulations. It is expected that the simulation will be completed within the 2022 fiscal year.
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| Strategy for Future Research Activity |
To promote this study, first a complete analysis of crack closure mechanisms in relation with the underlying microstructure will be done using the CPFEM model that is currently being prepared. From this, understand how microstructure can be manipulated i.e., during processing such that crack closure is enhanced to realize materials that are difficult to fracture. Secondly, the results of this study will be presented in conferences (both domestic and international) and published in an international journal.
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