钛合金Ti-6Al-4V室温保载-疲劳寿命预报方法研究
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摘要
在考虑小裂纹效应的基础上提出室温下保载-疲劳寿命预报模型。利用该模型对钛合金Ti-6Al-4V的疲劳寿命、不同应力水平和不同保载时间下的保载-疲劳寿命进行预报,并与相应试验结果进行对比和分析。该模型较好地描述了钛合金材料在不同保载时间和应力水平下疲劳和保载-疲劳寿命变化规律。在相同保载时间下,随着应力水平的降低,保载-疲劳寿命与疲劳寿命之间的差异降低,直至相同(应力为0.6σy)。随着应力水平的增加,保载-疲劳寿命与疲劳寿命之间的差异增加。在相同应力水平下,随着保载时间的增加,保载-疲劳寿命呈指数降低,但存在一个饱和时间值。达到该值后,保载-疲劳寿命保持不变。模型的预报值与相应的试验结果吻合较好,表明该模型对钛合金Ti-6Al-4V的保载-疲劳寿命具有良好的预报能力。
A prediction method of the dwell-fatigue life at room temperature is presented in this paper considering the effect of small crack. Fatigue life, dwell-fatigue life under different hold time and stress of titanium alloys Ti-6 Al-4 Vare are predicted with this dwell-fatigue life prediction model. Then, the prediction results are compared with corresponding test data in order to verify the reliability of the model. The results show that the model can predict the fatigue life of titanium alloy Ti-6 Al-4 V well. Furthermore, the prediction model can reflect the change rules of titanium alloy dwell-fatigue life under different hold time and stress. Dwell-fatigue life is consistent with fatigue life(0.6σy) with the decrease of stress under the same hold time. Difference between the dwell-fatigue life and the fatigue life is increased with the increase of stress. The dwell-fatigue life of titanium alloys Ti-6 Al-4 V decreases exponentially with the increase of hold time under the same stress; but a saturation value of hold time is existing. Besides, good agreement between test data and prediction results validates the reasonability of the model.
A prediction method of the dwell-fatigue life at room temperature is presented in this paper considering the effect of small crack. Fatigue life, dwell-fatigue life under different hold time and stress of titanium alloys Ti-6 Al-4 Vare are predicted with this dwell-fatigue life prediction model. Then, the prediction results are compared with corresponding test data in order to verify the reliability of the model. The results show that the model can predict the fatigue life of titanium alloy Ti-6 Al-4 V well. Furthermore, the prediction model can reflect the change rules of titanium alloy dwell-fatigue life under different hold time and stress. Dwell-fatigue life is consistent with fatigue life(0.6σy) with the decrease of stress under the same hold time. Difference between the dwell-fatigue life and the fatigue life is increased with the increase of stress. The dwell-fatigue life of titanium alloys Ti-6 Al-4 V decreases exponentially with the increase of hold time under the same stress; but a saturation value of hold time is existing. Besides, good agreement between test data and prediction results validates the reasonability of the model.
引文
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[2]POURIAN M H,BRIDIER F,PILVIN P,et al.Prediction of crack initiation sites in alpha Ti-alloys microstructures under Dwell-Fatigue using cellular automaton simulation method[J].International Journal of Fatigue,2015,85:85-97.
[3]BACHE M R,COPE M,DAVIES H M,et al.Dwell sensitive fatigue in a near alpha titanium alloy at ambient temperature[J].International Journal of Fatigue,1997,19(93):83-88.
[4]BACHE M R.A review of dwell sensitive fatigue in titanium alloys:the role of microstructure,texture and operating conditions[J].International Journal of Fatigue,2003,25(9–11):1079-1087.
[5]MILLER W H,CHEN R T,STARKE E A.Microstructure,creep,and tensile deformation in Ti-6Al-2Nb-1Ta-0.8Mo[J].Metallurgical Transactions,1987,18(8):1451-1468.
[6]EVANS W J,BACHE M R.Dwell-sensitive fatigue under biaxial loads in the near-alpha titanium alloy IMI685[J].International Journal of Fatigue,1994,16(7):443-452.
[7]TOUBAL L,BOCHER P,MOREAU A.Dwell-fatigue life dispersion of a near alpha titanium alloy[J].International Journal of Fatigue,2009,31(3):601-605.
[8]陈传尧.疲劳与断裂[M].华中和科技大学出版社,2002.
[9]WANG F,CUI W.Experimental investigation on dwell-fatigue property of Ti–6Al–4V ELI used in deep-sea manned cabin[J].Materials Science&Engineering A,2015,642(905):136-141.