PSI - Issue 2_A

Jaewoong Jung et al. / Procedia Structural Integrity 2 (2016) 2989–2993 Author name / Structural Integrity Procedia 00 (2016) 000–000

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pulsed electric current, significantly. However, it became almost the same as the behavior of untreated specimen in high K max . From the result, it is considered that when the stress intensity becomes larger than about 0.91 MPam 1/2 , the concentration of electric current is decreased at the fatigue crack tip. It means that the electric current is not enough to melt the fatigue crack. On the other hand, the crack growth rates at the electric current density of 150 A/mm 2 were faster than that of untreated one as shown Fig. 3(b). From the SEM micrograph, it is considered that the rapid crack propagation was caused by the thermal damage. As a result, it was clarified that the fatigue crack growth behavior was influenced by the application of electric current. Furthermore, it could be considered that the fatigue life was increased by the delay effect of the fatigue crack propagation. 4. Conclusions The effect of pulsed electric current on fatigue crack was examined in this study. The fatigue life was increased by the application of electric current with the density level of 90 A/mm 2 . However, when the density becomes too high, that is 150 A/mm 2 , the fatigue life was decreased compared to the untreated specimen. The fracture surfaces and the fatigue crack behaviors were influenced by the application of electric current. With the electric current density of 90 A/mm 2 , the crack growth rates were decreased by inducing local melting. On the other hand, with 150 A/mm 2 , the crack growth rates were increased due to thermal damage. Consequently, it is considered that the fatigue life was increased by the delay effect of fatigue crack growth. References Kapenko, G., Kuzin, O, Tkachev, V., Rudenko, V., 1976. Influence of an electric current upon the low-cycle fatigue of steel. Doklady Physics 21, 159-160. Conrad, H., White, J., Cao, W., Lu, X., Sprecher, A, 1991. Effect of electric current pulses on fatigue characteristics of polycrystalline copper. Materials Science and Engineering, A 145, 1-12. Salandro, W., Jones, J., McNeal, T., Roth, J., Hong, S., Smith, M., 2010. Formability of Al 5xxx sheet metals using pulsed current for various heat treatments. Journal of Manufacturing Science and Engineering 132, 051016-1-11. Roh, J., Seo, J., Hong, S., Kim, M., Han, H., Roth, J., 2014. The mechanical behavior of 5052-H32 aluminum alloys under a pulsed electric current. International Journal of Plasticity 58, 84-99. Hosoi, A., Nagahama, T., Ju, Y., 2012. Fatigue crack healing by a controlled high density electric current field. Material Science and Engineering, A 533, 38-42. Zhou, Y., Zeng, Y., He, G., Zhou, B., 2001. The healing of quenched crack in 1045 steel under electropulsing. Journal of Material Research 16, 17-19. Raju, I., Newman, J., 1979. Stress-intensity factors for a wide range of semi-elliptical surface cracks in finite-thickness plates. Engineering Fracture Mechanics 11, 817-829. Newman, J., Raju, I., 1981. An empirical stress-intensity factor equation for the surface crack. Engineering Fracture Mechanics 15, 185-192. Qin, R., Su, S., 2002. Thermodynamics of crack healing under electropulsing. Journal of Materials Research 17, 2048-2052. Zhou, Y., Guo, J., Gao, M., He, G., 2004. Crack healing in a steel by using electropulsing technique. Materials Letters 58, 1732-1736. Ritchie, R., Yu, W., Bucci, R., 1989. Fatigue crack propagation in ARALL LAMINATES: Measurement of the effect of crack-tip shielding from crack bridging. Engineering Fracture Mechanics 32, 361–377.