MicroCT (microtomography) quantification of microstructure related to macroscopic behaviour: Part 1 – Fatigue crack closure measured in situ in AA 2090 compact tension samples
Restricted accessResearch articleFirst published online September, 2006
MicroCT (microtomography) quantification of microstructure related to macroscopic behaviour: Part 1 – Fatigue crack closure measured in situ in AA 2090 compact tension samples
Microcomputed tomography (microCT) quantified crack opening in situ in a small compact tension specimen (AA 2090 T8E41) as a function of 3D position and of applied load. The same specimen was observed twice at two crack lengths. Some crack face areas were dominated by large asperities, while others were relatively flat. Large openings followed the sides of large asperities, with small openings elsewhere. The crack path and pattern of openings are discussed in terms of the variation in mesotexture. Before and after the crack extension, the pattern of open (and closed) voxels did not appear to change, suggesting that contact at a point near the crack tip will continue at the same portion of the fatigue cycle after the tip has receded. Testing parameters and macroscopic closure measurements link the present microCT measurements to studies in the literature.
Voxel is the abbreviation for volume element, and the size of a voxel is described in terms of the lengths of its three orthogonal edges. When these edges are equal, the voxel is ‘isotropic’, and only one dimension is required to completely define the size of an isotropic voxel.
2.
BreunigT. M.: ‘Nondestructive evaluation of damage in SiC/A1 metal/matrix composite using x-ray tomographic microscopy’, PhD thesis, Georgia Institute of Technology, Atlanta, GE, USA, 1992.
3.
BreunigT. M., StockS. R., AntolovichS. D., KinneyJ. H., MasseyW. N. and NicholsM. C.: ‘Fracture mechanics: twenty-second symposium’, ASTM STP 1131,Vol. 1, 749-761; 1992, Philadelphia, PA, ASTM.
4.
BreunigT. M., StockS. R. and BrownR. C.: Mater. Eval, 1993, 51, 596–600.
5.
GuvenilirA.: ‘Investigation into asperity induced closure in an Al-Li alloy using x-ray tomography’, PhD thesis, Georgia Institute of Technology, Atlanta, GE, USA, 1995.
6.
GuvenilirA., BreunigT. M., KinneyJ. H. and StockS. R.: Acta Mater., 1997, 45, 1977–1987.
7.
GuvenilirA. and StockS. R.: Fatigue Fract. Eng. Mater. Struct., 1998, 21, 439–450.
8.
GuvenilirA., BreunigT. M., KinneyJ. H. and StockS. R.: Philos. Trans. Roy. Soc. Lond. Ser. A, 1999, 357A, 2755–2775.
9.
GuvenilirA., StockS. R., BarkerM. D. and BetzR. A.: Proc. 4th Int. Conf. on ‘Aluminum alloys’,Vol. 2, 413-419; 1994, Atlanta, GE, Georgia Institute of Technology.
10.
MoranoR. N.: ‘Effect of R-ratio on crack closure in Al-Li 2090 T8E41, investigated non-destructively with X-ray microtomogra-phy’, Master thesis, Georgia Institute of Technology, Atlanta, GE, 1998.
11.
MoranoR., StockS. R., DavisG. R. and ElliottJ. C.: Mater. Res. Soc. Proc., 2000, 591, 31–35.
12.
MoranoR., StockS. R., DavisG. R. and ElliottJ. C.: Proc. 12th Int. Conf. on ‘Textures of metals’, (ed.SzpunarJ. A.), Vol. 2, 1106-1111; 1999, Ottawa, National Research Council of Canada.
13.
HaaseJ. D., GuvenilirA., WittJ. R. and StockS. R.: Acta Mater., 1998, 46, 4791–4799.
14.
HaaseJ. D., GuvenilirA., WittJ. R., LammM. A., and StockS. R.: ‘Mixed-mode crack behavior’, ASTM STP 1359, 160-173; 1999, Philadelphia, PA, ASTM.
15.
HaaseJ. D.: ‘Microbeam diffraction mapping of microtexture in Al-Li 2090 T8E41’, Master thesis, Georgia Institute of Technology, Atlanta, GE, 1998.
16.
RekZ. U. and StockS. R.: Adv. X-ray Anal, 2000, 44, 56–61.
17.
McClintockF. A. and ArgonA. S.: ‘Mechanical behavior of materials’; 1966, Reading, MA Addison-Wesley.
18.
BonseU., NusshardtR., BuschF., PahlR., KinneyJ. H., JohnsonQ. C., SaroyanR. A. and NicholsM. C.: J. Mater. Sci., 1991, 26, 4076–4085.
19.
TodaH., SinclairI., BuffiereJ. Y., MaireE., ConnolleyT., JoyceM., KhorK. H. and GregsonP.: Philos. Mag., 2003, 83,2429–2448.
DavisG. R. and ElliottJ. C.: J. Phys., 2003, 104, 131–
24.
KakA. C. and SlaneyM.: ‘Principles of computerized tomographic imaging’, 177-201; 2001, Philadelphia, PA, Society of Industrial and Applied Mathematics.
25.
BreunigT. M., ElliottJ. C., StockS. R., AndersonP., DavisG. R. and GuvenilirA.: ‘X-ray microscopy III’, 465–468; 1992, New York, Springer-Verlag.
26.
BreunigT. M., StockS. R., GuvenilirA., ElliottJ. C., AndersonP. and DavisG. R.: Composites, 1993, 24, 209–213.
27.
YoderG. R., PaoP. S., ImamM. A. and CooleyL. A.: Proc. 5th Aluminum-Lithium Conf.: ‘Aluminum-lithium alloys’, (ed. T. H. Sanders, Jr. and E. A. Starke, Jr.), 1033–1041; 1989, Birmingham,Materials and Component Engineering Publications.
28.
RaoK. T. V. and RitchieR. O.: Int. Mater. Rev., 1992, 37, 153–185.
29.
For gray scale in the print version read color table in the online version. Similarly where a color such as white in the print version is represented by a specific color (gold) in the online version the following is used: ‘white (online: gold)’.
30.
SureshS.: ‘Fatigue of materials’, 2nd edn; 1998, Cambridge, Cambridge University Press.
Here the term ‘mesotexture’ is used to describe crystallographic texture at the level of small groups of grains, i.e. at length scales between specimen average texture (microtexture) and the orientation of individual grains (microtexture ).
33.
IgnatievK. I.: ‘Development of x-ray phase contrast and microtomographymethods for the 3D study of fatigue cracks,’PhD thesis, Georgia Institute of Technology, Atlanta, GE, USA, 2004.
34.
IgnatievK. I., LeeW.-K., FezzaaK. and StockS. R.: Philos. Mag., 2005, 85, 3273–3300. Ignatiev et al. MicroCT quantification of microstructure: Part 1 Materials
