에이징 효과를 고려한 알루미늄 합금의 저주기 피로수명 예측

초록

In recent years, various lightweight materials have been used to automobile engine components according to the development of a high-performance internal combustion engine together with high fuel efficiency. On the other hand, these materials may lead to a change in mechanical properties at high pressure and high temperature which affects the durability of the engine components. In this study, the low-cycle fatigue (LCF) tests were conducted by using the aged aluminum alloy for a piston of an automobile engine, and then the fatigue life prediction based on cyclic visco-plasticity theory were verified by comparing with the experimental data. The LCF tests were carried out at different temperature 25°C and 250°C, using aluminum specimens aged initially at 250°C for 200 hours and non-aged specimens. From the results of the experiment, the stabilized hysteresis curve of the aged specimen showed that the plastic strain range increased. Conversely, the stress and the fatigue life decreased compared with those of the non-aged specimen under the same temperature and strain amplitude conditions. Furthermore, the numerical analysis using life prediction model facilitates the several behaviors to be modeled such as cyclic hardening, softening, and visco- plasticity within 10% of error accuracy as well as the LCF life to be predicted within 2 factors. Conclusionally, by employing the change of mechanical properties resulting from aging effects of aluminum alloy used in the engine piston into the fatigue life prediction model based on cyclic visco-plasticity theory, the methodology for the prediction of material behavior and low-cycle fatigue life adequately has been proposed.

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