平均载荷及载荷幅值对工业纯钛双轴保载疲劳行为影响

胡昌群; 赵佳禹; 常乐; 周昌玉; 贺小华

doi:10.7513/j.issn.1004-7638.2023.03.008

平均载荷及载荷幅值对工业纯钛双轴保载疲劳行为影响

doi: 10.7513/j.issn.1004-7638.2023.03.008

胡昌群^{1, 2,},
赵佳禹^{1, 2},
常乐^{1, 2},
周昌玉^{1, 2},
贺小华¹

1.
南京工业大学机械与动力工程学院, 江苏南京 211816
2.
江苏省极端承压装备设计与制造重点实验室, 江苏南京 211816

基金项目: 国家自然科学基金资助（项目号No.51975271和51905260）。

详细信息

作者简介:
胡昌群，1993年出生，男，山东莱阳人，硕士研究生，主要从事过程设备结构与强度研究，E-mail：1205431863@qq.com

中图分类号: TF823,TG146.23
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出版历程
- 收稿日期: 2022-11-18
- 刊出日期: 2023-06-30

Effects of mean load and load amplitude on biaxial dwell fatigue behavior of commercial pure titanium

Hu Changqun^{1, 2
,},
Zhao Jiayu^{1, 2},
Chang Le^{1, 2},
Zhou Changyu^{1, 2},
He Xiaohua¹

1.
School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu, China
2.
Jiangsu Key Lab of Design and Manufacture of Extreme Pressure Equipment, Nanjing 211816, Jiangsu, China

摘要

摘要: 通过室温双轴保载疲劳试验，研究了不同平均载荷及载荷幅值对工业纯钛双轴保载疲劳行为的影响。结果表明，在相同保载时间下，平均应变及应变速率随着平均载荷和载荷幅值的升高而逐渐增大。当载荷幅值一定时，蠕变应变随着平均载荷的增大而增大，当平均载荷一定时，蠕变应变随着载荷幅值的增大反而减小。分析双轴棘轮与蠕变应变之间交互作用时，发现两者始终相互制约。断口分析表明，随着平均载荷和载荷幅值的增大，疲劳条带特征逐渐消失，韧窝及撕裂棱数量显著增加，断口呈现韧性失效特征。随着平均载荷或载荷幅值的增加，等效应变幅值增加，疲劳寿命逐渐降低。与平均载荷的影响相比，疲劳寿命对载荷幅值的变化更加敏感。分别利用最大主应变、最大剪应变、Mises等效应变、最大主应力及SWT模型进行双轴保载疲劳寿命预测，其中SWT模型预测精度最高。
- 工业纯钛 /
- 非对称载荷 /
- 双轴保载疲劳 /
- 寿命预测
Abstract: Based on biaxial dwell fatigue tests at room temperature, effects of different mean loads and load amplitudes on the biaxial dwell fatigue behavior of commercial pure titanium were studied. The results show that the mean strain and strain rate increase with the increase of mean load and load amplitude under the same dwell time. When the load amplitude remains constant, the creep strain increases with the increase of the mean load. However, when the mean load remains constant, the creep strain decreases with the increase of the load amplitude. By analyzing the interaction between biaxial ratcheting and creep strain, it is found that ratcheting strain and creep strain are always restricted by each other. Fracture surface analysis shows that with the increase of mean load and load amplitude, the fatigue strip characteristics disappear gradually, and the number of dimples and tearing ridges significantly increases, exhibiting ductile failure mode. Meanwhile, with the increase of mean load or load amplitude, equivalent strain amplitude is increased, leading to the decrease of fatigue life. Compared with the effect of mean load, fatigue life is more sensitive to the variation of load amplitude. Maximum principal strain, maximum shear strain, Mises equivalent strain, maximum principal stress and SWT models are used to perform biaxial dwell fatigue life prediction, among them SWT model has the highest prediction accuracy.
- commercial pure titanium /
- asymmetric load /
- biaxial dwell fatigue /
- life prediction

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图 1 十字形试件形状及尺寸（单位：mm）

Figure 1. Optimized shape and size of the cruciform specimen

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图 2 各点应变（T_h=10 s）

Figure 2. The strain point diagram (T_h=10 s)

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图 3 非对称循环载荷下的保载疲劳X轴应变变化曲线

Figure 3. Dwell fatigue X-axis strain variation curves with asymmetric cyclic loading

(a) F_a=1200 N； (b) F_a=1300 N； (c) F_a=1400 N ；(d) F_m=1700 N ；(e) F_m=1800 N ；(f) F_m=1900 N

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图 4 非对称载荷下蠕变应变曲线

(a)X轴蠕变应变曲线；(b) Y轴蠕变应变曲线

Figure 4. Creep strain curves under asymmetric loading

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图 5 非对称载荷下双轴应变变化曲线

X轴应变变化曲线：(a)F_a=1300 N， F_m=1800 N；(c)F_a=1300 N， F_m=1900 N；(e)F_a=1400 N， F_m=1900 N；Y轴应变变化曲线：(b)F_a=1300 N， F_m=1800 N；(d)F_a=1300 N， F_m=1900 N；(f)F_a=1400 N， F_m=1900 N

Figure 5. Biaxial strain variation curves under asymmetric loading

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图 6 不同平均载荷及载荷幅值下断口形貌

Figure 6. Fracture morphology under different mean loads and load amplitudes

(a) F_a=1200 N，F_m=1700 N ；(b) F_a=1400 N，F_m=1700 N； (c) F_a=1400 N， F_m=1900 N

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图 7 疲劳断口SEM形貌(F_a=1200 N，F_m=1700 N)

(a)裂纹源区；(b)裂纹扩展区；(c)疲劳辉纹；(d)瞬断区

Figure 7. SEM images of fatigue fracture( F_a=1200 N，F_m=1700 N )

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图 8 疲劳断口SEM形貌(F_a=1400 N，F_m=1700 N)

(a)裂纹源区；(b)裂纹扩展区；(c)疲劳辉纹；(d)瞬断区

Figure 8. SEM images of fatigue fracture (F_a=1400 N，F_m=1700 N)

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图 9 疲劳断口SEM形貌(F_a=1400 N，F_m=1900 N)

(a)裂纹源区；(b)裂纹扩展区；(c)疲劳辉纹；(d)瞬断区

Figure 9. SEM images of fatigue fracture( F_a=1400 N，F_m=1900 N )

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图 10 保载疲劳寿命与等效应变幅值随平均载荷的变化

Figure 10. Variation of dwell fatigue life and equivalent strain amplitude with different mean loads

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图 11 保载疲劳寿命与等效应变幅值随载荷幅值的变化

Figure 11. Variation of dwell fatigue life and equivalent strain amplitude with different load amplitudes

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图 12 不同预测模型的寿命预测结果曲线

(a) 最大主应变； (b) 最大剪应变； (c) Mises等效应变；(d) 最大主应力； (e) SWT

Figure 12. Comparisons between predicted results by different models and experimental results

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表 1 TA2在不同平均载荷及载荷幅值下的双轴保载疲劳试验方案

Table 1. Biaxial dwell fatigue test scheme of TA2 under different average loads and load amplitudes

编号	F_m/N	F_a/N	半寿命周次				N_f
编号	F_m/N	F_a/N	Δε_x/%	Δε_ν/%	Δε_Z/%	Δε_eq/%	N_f
1	1700	1200	0.448	0.354	-0.802	0.8038	6013
2	1800	1200	0.413	0.392	−0.805	0.8051	4420
3	1 900	1200	0.431	0.405	−0.836	0.8361	570
4	1700	1300	0.403	0.415	−0.818	0.8180	2638
5	1800	1300	0.435	0.407	−0.842	0.8422	1484
6	1 900	1300	0.472	0.423	−0.895	0.8954	360
7	1700	1400	0.454	0.429	−0.883	0.8831	968
8	1800	1400	0.477	0.451	−0.928	0.9281	130
9	1 900	1400	0.649	0.456	−1.105	1.1106	34

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表 2 不同预测模型的参数取值

Table 2. Parameter values of different prediction models

预测模型	A	b
最大主应变	1.2938	−0.05884
最大剪应变	1.0347	−0.06581
Mises等效应变	1.3559	−0.05953
最大主应力	552.8398	−0.01735
SWT	715.9432	−0.07639

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表 3 不同寿命预测模型的预测误差

Table 3. Prediction errors of different life prediction models

预测模型	平均误差/%
最大主应变	58.50
最大剪应变	69.33
Mises 等效应变	59.75
最大主应力	68.54
SWT	34.07

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