为了进一步揭示影响泡沫封堵性能的根本原因,首先通过泡沫驱替实验研究了温度对泡沫封堵性能的影响,然后利用界面流变仪分析了界面参数随温度的变化,在此基础上,建立起泡沫封堵性能与界面性质之间的联系,考察界面性质对泡沫封堵性能的...为了进一步揭示影响泡沫封堵性能的根本原因,首先通过泡沫驱替实验研究了温度对泡沫封堵性能的影响,然后利用界面流变仪分析了界面参数随温度的变化,在此基础上,建立起泡沫封堵性能与界面性质之间的联系,考察界面性质对泡沫封堵性能的影响。结果表明:当温度由20℃升高到80℃时,泡沫封堵能力先增后减,40℃时达到最大,80℃时阻力因子减小80%以上,有效倍数降低至40℃时的六分之一。相同温度变化范围内,平衡界面张力先减后增,40℃时界面张力最小为28.6 m N×m^(-1),而扩张模量和界面弹性模量先增后减,界面黏性模量则逐渐减小,40℃时工作频率0.1 Hz对应的最大扩张模量、界面弹性模量和界面黏性模量分别为9.24、8.74、2.97 m N×m^(-1)。界面流变性表征了泡沫液膜性质,封堵性能好的泡沫应同时具有一定的高黏度和良好的弹性,界面弹性模量和界面黏性模量共同影响泡沫封堵性能;界面张力与泡沫封堵性能呈负相关关系,界面张力越小,越有利于泡沫再生,并对应越大界面模量,因而泡沫封堵性能越好。展开更多
The aim of this work is to analyze the stress distributions on a crown-luting cement-substrate system with a finite-element method in order to predict the likelihood of interfacial micro cracks, radial or circumferent...The aim of this work is to analyze the stress distributions on a crown-luting cement-substrate system with a finite-element method in order to predict the likelihood of interfacial micro cracks, radial or circumferential cracks, delamination, fracture and delamination with torsion. The contact and layer interface stresses in elastic layered half-space indented by an elastic sphere were examined using finite element method. The model consists of crown, luting cement and substrate. The solutions were carried out for three different elastic moduli of luting cement. It was placed between the cement and the substrate as a middle layer and its elastic module was chosen lower than the elastic module of crown and higher than the elastic module of dentin. An axisymmetric finite element mesh was set up for the stress analysis. Stress distributions on the contact surface and the interfaces of crown-luting cement and luting cement-dentin have been investigated for three different values of luting cement by using ANSYS. The effects of the luting cement which has three different elastic moduli on the pressure distribution and the location of interfacial stresses of the multi-layer model have been examined. The mechanism of crack initiation in the interfaces and interracial delamination was also studied quantitatively. For each luting cement, the pressure distribution is similar at the contact zone. Stress discontinuities occur at the perfect bonding interfaces of the crown-luting cement and the substrate-luting cement. The maximum stress jumps are obtained for the highest and the lowest elastic module of the luting cement. In the crown-luting cement-substrate system, failures may initiate at crown-luting cement region for luting cement with the lowest elastic module value. In addition, failures at luting cement-substrate region may occur for luting cement with the highest elastic module. In the luting cement, the medium elastic module value is more suitable for stress distribution in crown-luting cement-substrate interfaces.展开更多
Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical engineering.Basalt fiber is a new kind of environment-friendly and highperfo...Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical engineering.Basalt fiber is a new kind of environment-friendly and highperformance soil reinforcement material,and the mechanical properties of basalt fiber-reinforced soil have become a hot research topic.In this paper,we conducted monotonic triaxial and cyclic triaxial tests,and analyzed the influence of the fiber content,moisture content,and confining pressure on the shear characteristics,dynamic modulus,and damping ratio of basalt fiber-reinforced silty clay.The results illustrate that basalt fiber can enhance the shear strength of silty clay by increasing its cohesion.We find that the shear strength of reinforced silty clay reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%(optimum moisture content).Similarly,we also find that the dynamic modulus that corresponds to the same strain first increases then decreases with increasing fiber content and moisture content and reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%.The dynamic modulus is positively correlated with the confining pressure.However,the change in the damping ratio with fiber content,moisture content,and confining pressure is opposite to that of the dynamic modulus.It can be concluded that the optimum content of basalt fiber for use in silty clay is 0.2%.After our experiments,we used scanning electron microscope(SEM)to observe the microstructure of specimens with different fiber contents,and our results show that the gripping effect and binding effect are the main mechanisms of fiber reinforcement.展开更多
文摘为了进一步揭示影响泡沫封堵性能的根本原因,首先通过泡沫驱替实验研究了温度对泡沫封堵性能的影响,然后利用界面流变仪分析了界面参数随温度的变化,在此基础上,建立起泡沫封堵性能与界面性质之间的联系,考察界面性质对泡沫封堵性能的影响。结果表明:当温度由20℃升高到80℃时,泡沫封堵能力先增后减,40℃时达到最大,80℃时阻力因子减小80%以上,有效倍数降低至40℃时的六分之一。相同温度变化范围内,平衡界面张力先减后增,40℃时界面张力最小为28.6 m N×m^(-1),而扩张模量和界面弹性模量先增后减,界面黏性模量则逐渐减小,40℃时工作频率0.1 Hz对应的最大扩张模量、界面弹性模量和界面黏性模量分别为9.24、8.74、2.97 m N×m^(-1)。界面流变性表征了泡沫液膜性质,封堵性能好的泡沫应同时具有一定的高黏度和良好的弹性,界面弹性模量和界面黏性模量共同影响泡沫封堵性能;界面张力与泡沫封堵性能呈负相关关系,界面张力越小,越有利于泡沫再生,并对应越大界面模量,因而泡沫封堵性能越好。
文摘The aim of this work is to analyze the stress distributions on a crown-luting cement-substrate system with a finite-element method in order to predict the likelihood of interfacial micro cracks, radial or circumferential cracks, delamination, fracture and delamination with torsion. The contact and layer interface stresses in elastic layered half-space indented by an elastic sphere were examined using finite element method. The model consists of crown, luting cement and substrate. The solutions were carried out for three different elastic moduli of luting cement. It was placed between the cement and the substrate as a middle layer and its elastic module was chosen lower than the elastic module of crown and higher than the elastic module of dentin. An axisymmetric finite element mesh was set up for the stress analysis. Stress distributions on the contact surface and the interfaces of crown-luting cement and luting cement-dentin have been investigated for three different values of luting cement by using ANSYS. The effects of the luting cement which has three different elastic moduli on the pressure distribution and the location of interfacial stresses of the multi-layer model have been examined. The mechanism of crack initiation in the interfaces and interracial delamination was also studied quantitatively. For each luting cement, the pressure distribution is similar at the contact zone. Stress discontinuities occur at the perfect bonding interfaces of the crown-luting cement and the substrate-luting cement. The maximum stress jumps are obtained for the highest and the lowest elastic module of the luting cement. In the crown-luting cement-substrate system, failures may initiate at crown-luting cement region for luting cement with the lowest elastic module value. In addition, failures at luting cement-substrate region may occur for luting cement with the highest elastic module. In the luting cement, the medium elastic module value is more suitable for stress distribution in crown-luting cement-substrate interfaces.
基金Project(51978674) supported by the National Natural Science Foundation of ChinaProject(2017G008-A) supported by the China Railway Corporation Science and the Technology Development Project。
文摘Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical engineering.Basalt fiber is a new kind of environment-friendly and highperformance soil reinforcement material,and the mechanical properties of basalt fiber-reinforced soil have become a hot research topic.In this paper,we conducted monotonic triaxial and cyclic triaxial tests,and analyzed the influence of the fiber content,moisture content,and confining pressure on the shear characteristics,dynamic modulus,and damping ratio of basalt fiber-reinforced silty clay.The results illustrate that basalt fiber can enhance the shear strength of silty clay by increasing its cohesion.We find that the shear strength of reinforced silty clay reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%(optimum moisture content).Similarly,we also find that the dynamic modulus that corresponds to the same strain first increases then decreases with increasing fiber content and moisture content and reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%.The dynamic modulus is positively correlated with the confining pressure.However,the change in the damping ratio with fiber content,moisture content,and confining pressure is opposite to that of the dynamic modulus.It can be concluded that the optimum content of basalt fiber for use in silty clay is 0.2%.After our experiments,we used scanning electron microscope(SEM)to observe the microstructure of specimens with different fiber contents,and our results show that the gripping effect and binding effect are the main mechanisms of fiber reinforcement.
