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机构地区:[1]四川理工学院,自贡643000 [2]过程装备与控制工程四川省高校重点实验室,自贡643000
出 处:《应用力学学报》2015年第2期276-281,355-356,共6页Chinese Journal of Applied Mechanics
基 金:四川理工学院培育项目(2012PY15);四川省教育厅项目(13ZA0129);过程装备与控制工程四川省高校重点实验室基金(GK201205)
摘 要:为了提高疲劳-蠕变寿命的预测精度,首次从裂纹扩展角度出发引入有效应变能密度增量,利用应力-应变迟滞回线所围图形的正值面积对其进行了定义和计算。计算表明,有效应变能密度增量与加载的应力、速率、保载时间、材料性质及疲劳-蠕变的速率相关,且随压应力增加而增大。通过将有效应变能密度增量与裂纹的长度之积定义为裂纹扩展的控制参量,建立了疲劳-蠕变下的裂纹扩展速率方程,并由此导出了疲劳-蠕变寿命与有效应变能密度增量之间的关系式。该式中的疲劳与蠕变有效应变能密度增量交叉项恰好反映了疲劳与蠕变的交互作用。最后,采用该式对1.25Cr0.5Mo钢在540℃时不同应力控制下的疲劳-蠕变寿命进行了预测,发现83.3%的预测值在实验值的1.3倍分散带以内,预测结果良好。In order to improve the accuracy of fatigue-creep life prediction, the increment of strain energy density(effective strain energy density increment) is adopted as damage parameter of the material, which equals to the area enclosed by the hysteresis loops of stress-strain. The effective strain energy density increment is determined by the loading stress, loading rate, holding time, properties of material and the rate of fatigue-creep, and increases with the increment of compressive stress. By the definition of the product of effective strain energy density increment with crack length as the control parameter of the crack propagation, the fatigue crack growth rate modelof the fatigue-creep is established, and hence, the relationship between the fatigue-creep life and effective strain energy density increment is derived. This cross term of fatigue-creep strain energy density increment in the relationship just describes the interaction of fatigue and creep. The fatigue-creep life of the 1.25Cr0.5Mo steel under the stress control at 540℃ is predicted by the relationship. Calculated result shows a good agreement with the experimental data within the 1.3times scatter band for the 83.3% predicted values.
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