Failure modes during equal channel angular extrusion of aluminum alloy 2024
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Test
Strain Amplitude, Pct
Mean Strain, Pct
Stress Amplitude, MPa
Mean Stress, MPa
4 5 6
0.21 0.22 0.21
0.25 0.30 0.25
178 150 178
239 220 239
56.00 29.00 110.00
7
0.22
0.30
150
220
133.00
8
0.19
0.37
155
260
97.30
9
0.21
1.98
158
335
24.34
10
0.24
2.12
107
427
10.90
11
0.22
5.99
90
421
22.90
15 19 20
0.21 0.22 0.22
9.31 9.30 9.30
137 110 110
642 760 760
82.63 34.00 50.30
21
0.21
9.31
137
642
94.63
Nf ⫻ 10⫺3, Cycles
Comments
A grip grip test 4 repeated for two additional grip failures at 72 and 110 K test 5 repeated for two additional grip failures at 91 and 133 K gage; but frequency ⫽ 16 Hz
AM gage; mean strain set during reverse transformation gage; mean strain set during forward transformation gage; mean strain set during forward transformation
M
macroscopically sharp interface that was tilted to the loading axis. This means that specimens cycled in region AM contain macroscopically sharp interfaces, whereas specimens cycled in regions A and M do not contain any such interfaces. It is likely that the stresses are singular at the edges where the phase boundary meets with the physical boundary of the specimen. This can be deduced from the extensive research on free edges in bimaterial composites, as discussed in Simha and Bhattacharya.[9] It then follows that the stress concentrations at the edges of the phase boundaries may be the primary reason for the low values of the cycles-to-failure for specimens cycled in the AM region. Future studies will examine whether there is a direct correlation between the location of the phase boundaries and the region of crack initiation.
Some preliminary results were published in the Proc. Int. Conf. on Martensitic Transformations, Bariloche, Argentina, 1998. Two of the authors (RMT and NKS) thank the University of Miami Research Council for financial support. REFERENCES 1. K.N. Melton and M.O. Mercier: Acta Metall., 1979, vol. 27, pp. 137-44. 2. H. Tobushi, T. Hachisuka, S. Yamada, and P.H. Lin: Mech. Mater., 1997, vol. 26, pp. 35-42. 3. S. Miyazaki, K. Mizukoshi, T. Ueki, T. Sakuma, and Y.N. Liu: Mater. Sci. Eng., 1999, vol. A275, pp. 658-63. 4. S. Miyazaki: Engineering Aspects of Shape Memory Alloys, Butterworth-Heinemann, 1990, pp. 392-413. 5. N.K. Simha and N.H.C. Hwang: Int. J. Cardiovascular Med. Sci., 1999, vol. 2, pp. 105-11. 6. S. Miyazaki, Y. Ohmi, K. Otsuka, and Y. Suzuki: J. Phys., 1982, vol. 43, pp. C4-255-C4-260. 7. J.A. Shaw and S. Kyriakides: Acta Mater., 1997, vol. 45, pp. 683-700. METALLURGICAL AND MATERIALS TRANSACTIONS A
grip grip gage; test 19 repeated for two additional grip failures at 48.70 K, followed by gagesection failure at 50.30 K gage; test 15 was regripped to obtain a gagesection failure at 94.63 K
8. R.M. Tabanli: Ph.D. Thesis, University of Miami, Miami, FL, 2000. 9. N.K. Simha and K. Bhattacharya: J. Mech. Phys. Solids, 1998, vol. 46, pp. 2323-59.
Failure Modes during Equal Channel Angular Extrusion of Aluminum Alloy 2024 P.N. FAGIN, J.O. BROWN, T.M. BROWN, K.V. JATA, and S.L. SEMIATI
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