Thermal response of DP600 dual-phase steel under ultrasonic fatigue loading

Abstract

The present work employed in situ infrared thermography to investigate the thermal response and dissipative mechanisms of a dual-phase steel under ultrasonic tension-compression fatigue testing. A classical thermal response occurred for stress amplitudes below 247 MPa but an abnormal thermal response was observed for stress amplitudes above 247 MPa, in that the temperature stabilized after a steep increase of up to $ 350°C. The mean dissipated energy per cycle was estimated based on temperature measurements using the heat diffusion equation. The relationship between the mean dissipated energy per cycle and the stress amplitude was studied, and mechanisms related to the observed thermal response were discussed.

Correlation of the high and very high cycle fatigue response of ferrite based steels with strain rate-temperature conditions

“…However, the effect of heat generation cannot be impeded for all materials under ultrasonic fatigue loading even by cooling the specimen and using a pulse-pause mode [20e22]. The presence of inevitable heating effects under ultrasonic tests at high stress amplitudes has been already confirmed in a previous work of the authors for ferritic-martensitic steel [23]. Peng et al [21] stated that for structural steels with low tensile strength the specimen is prone to heating and burning at high stress amplitudes even by employing intermittent loading along with cooling systems.…”

“…For ultrasonic testing with 20-kHz frequency, the deformation regime depends on stress amplitude because of the presence of strong self-heating discussed in Ref. [23]. For the stress amplitudes below the fatigue limit (60 MPa< s a < 260 MPa), for which no strong heating occurred (T < 40 C), the maximum strain rate ranges from 36 s À1 to 156 s À1 .…”

“…However, in our case, as the loading conditions (temperature and strain rate) correspond to the athermal regime, no significant strain rate effect is expected. In the case of dual-phase steel under high temperature cycling, dynamic strain aging is known to occur [23], which results in increasing the yield and tensile strengths of the material. In other words, in spite of the high mobility of screw dislocations in the athermal deformation regime, because of the high temperature, interstitial carbon atoms diffuse around the dislocations and restrict their movements temporarily.…”

“…The strain rate amplitude was calculated as _ ε a ¼ 2pf sa E . Concerning the temperature, when self-heating developed during ultrasonic tests, the temperature was considered as the mean temperature before rupture [23,24,26]. In the case of low frequency tests, when no temperature information was provided, the tests were considered to be carried out at room temperature, RT (~22 C) without any self-heating.…”

Relationship to Corrosion Resistance-Thermal Fatigue Boiler Tubes with the Heat of the Defect Structure

“…В процессе термоциклирования наличие температурных градиентов приводит к термическим напряжени-ям. Анализ теплопроводности для прогнозирования термомеханической усталости, теплового сопротивления, оценки срока службы трубных элементов, работающих в условиях тепловой усталости, был представлен в модельной оценке в работах [10][11][12]. Авторы работы [13] показа-ли, что теплопроводность структурных составляющих в процессе термообработки ограничи-вает размеры фаз, что затрудняет получение желаемой микроструктуры.…”