Prediction of the swing fatigue life of flexible joint based on cracking energy density
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摘要:
为准确预测柔性接头的摆动疲劳寿命,将开裂能密度作为驱动弹性件疲劳裂纹扩展的损伤参量,借助材料的疲劳裂纹扩展试验和单轴拉伸疲劳试验建立了柔性接头的摆动疲劳寿命预测模型,并用有限元分析结果计算了柔性接头在12.3 MPa、6°摆角工况下的开裂能密度,进而对柔性接头的摆动疲劳寿命进行预测。结果表明:预测试验工况下柔性接头的摆动疲劳寿命为107次,实测寿命为120次,两者较为一致,且预测的裂纹位置和开裂平面与实际试验的失效位置较为吻合。模型预测柔性接头的摆动疲劳寿命与实测疲劳寿命之比为1/1.12,分布在2倍分散因子之内,满足工程疲劳寿命的预测要求。
Abstract:In order to accurately predict the swing fatigue life of flexible joint, the cracking energy density (CED) was used as the damage parameter to drive the fatigue crack growth of elastomers. The swing fatigue life prediction model of flexible joint was established by means of fatigue crack growth test and uniaxial tensile fatigue test. The CED of flexible joint under 12.3 MPa and 6° swing angle was calculated by using the finite element analysis results, and then the swing fatigue life of flexible joint was predicted. The results showed that the predicted swing fatigue life of the flexible joint under the test condition was 107 cycles, which was consistent with the measured fatigue life of 120 cycles, and the predicted crack location and crack plane were in good agreement with the failure position of test. The ratio of predicted life to measured life was 1/1.12 within the double dispersion factor, which was acceptable in engineering.
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表 1 纯剪试件静强度试验结果
Table 1. Static strength test results of pure shear specimens
试件编号 拉断应变εsb/% 拉断应力
σst/MPa拉断应变能密度Wb/MPa 临界撕裂能
Tc/(kJ/m2)a1(h0=7.06 mm) 87.57 0.5103 0.4410 3.1136 a2(h0=7.45 mm) 95.64 0.5015 0.4666 3.4759 a3(h0=6.51 mm) 85.23 0.5108 0.4333 2.8206 表 2 硅橡胶单轴拉伸疲劳试验结果
Table 2. Results of uniaxial tensile fatigue test of silicone rubber
编号 εmax/% εmin/% Nf,max/cycles Nf,min/cycles Nf,avg/cycles 1 200 0 4536 3657 4088 2 250 0 3065 2435 2776 3 300 0 1923 1437 1660 4 350 0 1593 1177 1349 5 400 0 1108 786 963 表 3 柔性接头摆动疲劳寿命试验工况信息
Table 3. Condition of swing fatigue life test of flexible joint
环境温度/℃ 试验压强/MPa 摆动频率/Hz 摆角幅值/(°) 23±2 12.3 1 ±6 表 4 弹性件材料本构模型拟合参数
Table 4. Constitutive parameter of elastomer
本构参数 μ1/10−5 α1 μ2 α2 拟合值 1.83663 10.303 21.539 0.02659 表 5 柔性接头预测疲劳寿命与实测寿命对比
Table 5. Comparison between predicted fatigue life and measured fatigue life of flexible joint
预测开裂单元 开裂能密度峰值
Wc,max/MPa开裂方位角
θ/rad预测寿命
Nf,pre/cycles实测寿命
Nf,test/cyclesNf,pre/Nf,test No.7505 5.585 θ=0,±π 107 120 1/1.12 -
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