نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه مکانیک، دانشکده مکانیک، دانشگاه صنعتی سهند تبریز، تبریز، ایران
2 مهندسی مکانیک / دانشگاه صنعتی سهند تبریز
3 مرکز تحقیقات مواد پیشرفته، دانشکده مهندسی مواد، دانشگاه صنعتی سهند، تبریز، ایران
4 استادیار دانشکده مهندسی مکانیک، دانشگاه تهران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
In recent years, shape memory alloys, especially NiTi, have received a great deal of attention in industrial applications. Martensitic phase transformation in shape memory alloys is the most important factor in their unique behavior. In this paper, the formation of stress-induced martensite phase in the crack tip of superelastic NiTi (50.8% Ni) samples was investigated by using the digital image correlation method. In particular, single edge cracked specimens were subjected to fatigue mechanical loading, then the crack length and also displacement fields at the crack tip of specimens were measured by the digital image correlation technique. Control of the crack length was performed using a high magnification camera during the fatigue test. In the following, stress intensity factors were calculated according to ASTM standard E647-15. Obtained results from the fracture analysis show that fatigue threshold values are decreased with increasing the load ratio. In the present paper, for a load ratio of 0.05, during the crack propagation, the fatigue threshold value is 17 MPa m1/2, while stress intensity factor is estimated about 35 MPa m1/2 before the final failure. Also, as a new method in observation of the phase transformation, digital image correlation pictures indicated the formation of stress-induced martensite at the specimen crack tip.
کلیدواژه‌ها [English]
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