Grants and Contracts Details
Description
This project addresses the quantitative relationship between short fatigue crack resistance and the
twist component of crack plane deflection across either the particle-matrix interface or grain
boundary, in order to quantify short fatigue crack growth in 3 dimensions in a planar slip alloy,
such as AA2026, 2524 and 2099 Al alloys. A focused ion beam will be employed first to
fabricate a micro-notch which has a controlled twist angle with the primary slip plane in a coarse
grain of the alloy, and second to make serial cross-sections of fractured particles found in the
sample surface after fatigue. The resistance to the micro-crack growth from the notch will be
extracted from the measurement of crack growth rate as a function of the twist angle, which is
critical for the development of a quantitative microstructure-based model for short fatigue crack
growth. The 3 dimensional effects of the surface particles on fatigue crack initiation and early
growth will be quantitatively studied from reconstruction of the 3 dimensional geometries of the
particles using the serial cross-sections. The twist angle and driving force along the particle
interface will be calculated from EBSD measurement and the reconstructed 3 dimensional
geometries of these particles. Incorporation of both the resistance and driving force in PI’s
crystallographic model, the growth behavior of the micro-crack from a particle in the surface will
be quantified in 3 dimensions in the alloys. Consequently, a microstructure-based model will be
established to calculate the S-N curve for an alloy, given the grain structure and texture in the
alloy. Therefore, using this model, the desirable microstructure and texture will be identified for
the optimum high cycle fatigue properties in the alloys.
The technical merits of this project include: 1) Quantification of the relationship between crack
resistance and crack plane twist angle across a grain boundary, 2) incorporation of the 3
dimensional effects of microstructure in a crystallographic model for quantification of short
fatigue crack growth, 3) the model will allow identification of the desirable microstructure and
texture for the optimum resistance to fatigue damage in an alloy, and 4) revelation of the
mechanism for the difference in micro-crack growth behaviour between different particles on
surface. Broader Impacts: The improvement of the fatigue properties of Al alloys, as a result of
this project, can have significant impact on the aerospace and automotive industries, and as such
the proposed research could lead to a wider impact on society; 2) the alloy industry as a whole
will also benefit from the methodology, to be developed in this project, since it will advance alloy
design by identification of the desirable microstructure and texture that lead to optimum fatigue
resistance in high performance alloys; and 3) development of well trained young technical
graduates for the Aluminum, Automotive and Aerospace Industries. The PI will integrate the
research work into his teaching activities by developing two projects, related to the findings from
the project, for use in his MSE courses. Undergraduate students will also participate in this
project to make 3-D animation models for crack growth across grain boundaries, 3-D
microstructure and X-ray diffraction, etc. These models will be made available on a webpage,
together with the latest results from the project, for access by the public. The PI will organize
symposium series on fatigue damage in metallic materials at the TMS annual meetings, to
disseminate effectively the findings from this project among the researchers from the research
community and engineers from alloy industry.
Status | Finished |
---|---|
Effective start/end date | 9/1/12 → 2/28/17 |
Fingerprint
Explore the research topics touched on by this project. These labels are generated based on the underlying awards/grants. Together they form a unique fingerprint.