TC4 ELI钛合金高低周疲劳性能及寿命预测模型
High and Low Cycle Fatigue Performance and Life Prediction Model of TC4 ELI Titanium Alloy
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摘要: 在室温下对TC4 ELI钛合金进行应变控制(应变比为−1,应变幅分别为0.4%,0.6%,0.8%)低周疲劳试验和应力控制(应力比为0.1,最大应力分别为600,700,800 MPa)高周疲劳试验,研究了TC4 ELI钛合金在室温条件下的低周和高周疲劳性能。基于有效能量密度,建立了试验合金高低周疲劳寿命统一预测模型,并用室温条件下的疲劳寿命数据进行验证。结果表明:不同应变幅条件下的低周疲劳裂纹源均发生在试验合金表面;高周疲劳裂纹在最大应力为600 MPa时倾向萌生于试验合金次表面,在最大应力为700,800 MPa时倾向萌生于表面。92%的低周和高周疲劳预测寿命数据落在±3.0误差带范围内,说明建立的疲劳寿命模型具有较高的预测精度。Abstract: Strain-controlled low-cycle fatigue test (with strain ratio of −1 and strain amplitudes of 0.4%, 0.6%, and 0.8%) and stress-controlled high-cycle fatigue test (with stress ratio of 0.1 and maximum stresses of 600, 700, and 800 MPa) were conducted on TC4 ELI titanium alloy at room temperature to investigate its low-cycle and high-cycle fatigue performance. Based on the effective energy density, a unified fatigue life prediction model for both low-cycle and high-cycle fatigue was developed and validated by fatigue life data at room temperature. The results show that the low-cycle fatigue crack initiation sites were located on the test alloy surface under different strain amplitudes. The high-cycle fatigue crack initiated at the subsurface under the maximum stress of 600 MPa, and at the surface under the maximum stress of 700 and 800 MPa. 92% of the predicted low-cycle and high-cycle fatigue life data fell within the error band of ±3.0, indicating that the developed fatigue life model had high predictive accuracy.