The distribution and magnitude of surface substrates were investigated by finite element method and subsurface stresses of the （FEM）. The models of coating single-layer sprayed-coatings on monolithic configurations ...The distribution and magnitude of surface substrates were investigated by finite element method and subsurface stresses of the （FEM）. The models of coating single-layer sprayed-coatings on monolithic configurations with different thicknesses and elastic modulus ratios of coating to substrate were introduced, and the effects of thickness and elastic modulus ratio on the stresses were addressed. The calculation results show that the coating/substrate interface shear stress obviously decreases with increasing coating thickness, due to the location of the maximum shear stress moving away from the coating/substrate interface. At the same time, the magnitude of von Mises stress also declines in the case of thicker coatings. However, the high elastic modulus ratio results in extremely high maximum shear stress and the severe discontinuity of the von Mises stress curves, which leads to the intensive stress concentration on the coating/substrate interface. So the coating configurations with the larger coating thickness and lower difference of elastic modulus between coating and substrate exhibit excellent resistant performance of rolling contact fatigue （RCF）.展开更多
To solve the problems of divergence,low accuracy and project application of membrane wrinkling analysis,an analysis method of zero shear modulus and equivalent stiffness was proposed.This method is an improvement to t...To solve the problems of divergence,low accuracy and project application of membrane wrinkling analysis,an analysis method of zero shear modulus and equivalent stiffness was proposed.This method is an improvement to the previous method (Method I) of local coordinate transposition and stiffness equivalence.The new method is derived and the feasibility is theoretically proved.A small-scale membrane structure is analyzed by the two methods,and the results show that the computational efficiency of the new method (Method II) is approximately 23 times that of Method I.When Method II is applied to a large-scale membrane stadium structure,it is found that this new method can quickly make the second principal stress of one way wrinkled elements zero,and make the two principal stresses of two-way wrinkled elements zero as well.It could attain the correct load responses right after the appearance of wrinkled elements,which indicates that Method II can be applied to wrinkling analysis of large-scale membrane structures.展开更多
陶瓷基复合材料(ceramic matrix composites,CMC)作为一种优异的高温结构材料,在航空发动机领域得到了广泛应用。目前,依据GJB 10311—2021的双切口面内剪切实验方法存在明显局限性:切口位置处的应力集中效应导致标距区平均剪切应力计...陶瓷基复合材料(ceramic matrix composites,CMC)作为一种优异的高温结构材料,在航空发动机领域得到了广泛应用。目前,依据GJB 10311—2021的双切口面内剪切实验方法存在明显局限性:切口位置处的应力集中效应导致标距区平均剪切应力计算结果偏高,使得面内剪切模量测试结果与V形缺口剪切实验偏差可达30%。为此,本工作将数字图像相关方法(DIC)与双切口剪切实验相结合,开发一种面内剪切力学性能测试的新方法。为消除切口处应力集中的影响,提出采用有限元模型修正技术(finite element model updating,FEMU),利用DIC实测标距区内面内平均剪切应变与数值计算应变之间的方差构造目标函数,迭代获得材料的面内剪切模量。为便于工程应用,通过优化试样切口深度,实现单次实验即可获得材料的面内剪切模量和面内剪切强度,并采用SiC/SiC正交层合陶瓷基复合材料进一步验证了该实验方法的可行性和测试结果的可靠性。结果表明:该实验方法可同时准确测定陶瓷基复合材料的面内剪切模量和强度,测试结果与V形缺口实验结果偏差小于5%。相较V形缺口剪切实验,该方法实验工装和试样尺寸更小,更适用于高温面内剪切实验。SiC/SiC复合材料面内剪切应力-应变存在典型的屈服点,且屈服后剪切行为表现出典型的线性应变强化特征。展开更多
基金Project(2007AA04Z408) supported by the National High-Tech Research and Development Program of ChinaProject(50735006) supported by the National Natural Science Foundation of China
文摘The distribution and magnitude of surface substrates were investigated by finite element method and subsurface stresses of the （FEM）. The models of coating single-layer sprayed-coatings on monolithic configurations with different thicknesses and elastic modulus ratios of coating to substrate were introduced, and the effects of thickness and elastic modulus ratio on the stresses were addressed. The calculation results show that the coating/substrate interface shear stress obviously decreases with increasing coating thickness, due to the location of the maximum shear stress moving away from the coating/substrate interface. At the same time, the magnitude of von Mises stress also declines in the case of thicker coatings. However, the high elastic modulus ratio results in extremely high maximum shear stress and the severe discontinuity of the von Mises stress curves, which leads to the intensive stress concentration on the coating/substrate interface. So the coating configurations with the larger coating thickness and lower difference of elastic modulus between coating and substrate exhibit excellent resistant performance of rolling contact fatigue （RCF）.
基金Project(020940) supported by the Natural Science Foundation of Guangdong Province,China
文摘To solve the problems of divergence,low accuracy and project application of membrane wrinkling analysis,an analysis method of zero shear modulus and equivalent stiffness was proposed.This method is an improvement to the previous method (Method I) of local coordinate transposition and stiffness equivalence.The new method is derived and the feasibility is theoretically proved.A small-scale membrane structure is analyzed by the two methods,and the results show that the computational efficiency of the new method (Method II) is approximately 23 times that of Method I.When Method II is applied to a large-scale membrane stadium structure,it is found that this new method can quickly make the second principal stress of one way wrinkled elements zero,and make the two principal stresses of two-way wrinkled elements zero as well.It could attain the correct load responses right after the appearance of wrinkled elements,which indicates that Method II can be applied to wrinkling analysis of large-scale membrane structures.
文摘陶瓷基复合材料(ceramic matrix composites,CMC)作为一种优异的高温结构材料,在航空发动机领域得到了广泛应用。目前,依据GJB 10311—2021的双切口面内剪切实验方法存在明显局限性:切口位置处的应力集中效应导致标距区平均剪切应力计算结果偏高,使得面内剪切模量测试结果与V形缺口剪切实验偏差可达30%。为此,本工作将数字图像相关方法(DIC)与双切口剪切实验相结合,开发一种面内剪切力学性能测试的新方法。为消除切口处应力集中的影响,提出采用有限元模型修正技术(finite element model updating,FEMU),利用DIC实测标距区内面内平均剪切应变与数值计算应变之间的方差构造目标函数,迭代获得材料的面内剪切模量。为便于工程应用,通过优化试样切口深度,实现单次实验即可获得材料的面内剪切模量和面内剪切强度,并采用SiC/SiC正交层合陶瓷基复合材料进一步验证了该实验方法的可行性和测试结果的可靠性。结果表明:该实验方法可同时准确测定陶瓷基复合材料的面内剪切模量和强度,测试结果与V形缺口实验结果偏差小于5%。相较V形缺口剪切实验,该方法实验工装和试样尺寸更小,更适用于高温面内剪切实验。SiC/SiC复合材料面内剪切应力-应变存在典型的屈服点,且屈服后剪切行为表现出典型的线性应变强化特征。
