13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- 4. Conclusions Fatigue crack growth test were conducted in order to evaluate the effect of residual stress field on crack growth propagation. The results are as follows: (1) The extensometer can be installed tightly on the specimen by using the modified jig with magnet. The test results indicate that the accuracy of crack opening stress measurement is improved. (2) Stress ranges between 50 MPa and 75 MPa does not clearly affect the acceleration ratio for crack growth rate against the base material. On the other hand, in the case of = 25 MPa, the effect of residual stress on the acceleration ratio for crack growth rate against the base material is relatively high. This means the acceleration and deceleration of crack growth rate for that situation is also high. In this test, the acceleration ratio of the crack growth rate for the FSW panel against the base material is 3.7. References [1] G. Bussu, P E. Irving, Static and fatigue performance of Friction Stir Welded 2024-T351 aluminum joints, Proceedings of 1st International Symposium on Friction Stir Welding, 1999. [2] K. Kuwayama, M. Asakawa, T. Okada, T. Nakamura, S. Machida, S. Fujita, Fatigue crack propagation property of friction stir welded 2024-T3 aluminum alloy, APISAT 2009, CD. [3] T. Okada, K. Kuwayama, S. Fujita, M. Asakawa, T. Nakamura, Properties of fatigue crack propagation in friction stir welded 2024-T3 aluminum alloy, ICAF 2009, pp. 899-908 [4] S. Fujita, M. Asakawa, T. Okada, T. Nakamura, S. Machida, K. Kuwayama, Evaluation of FSW Fatigue Crack Growth Rate Based on Crack Closure Phenomenon, APISAT 2010, CD. [5] T. Noguchi, M. Asakawa, T. Okada, T. Nakamura, S. Machida, K. Kuwayama, S. Fujita, Property for Fatigue Crack Propagation of Friction Stir Welded 2024-T3 Aluminum Alloy, APISAT 2012; CD. [6] American Society for Testing and Material, Standard Test Method for Measurement of Fatigue Crack Growth Rates, ASTM E647-08, 2008 [7] Y. Chung, J. Song, Improvement of ASTM compliance offset method for precise determination of crack opening load, International Journal of Fatigue 31, 2009, pp.809-819 [8] W. Elber, The Significance of Fatigue Crack Closure, ASTM STP 486, 1971 [9] J.Schijve, Some Formulas for the Crack Opening Stress Level, Engineering Fracture Mechanics, 1981, pp.461-465.
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