连续丝束剪切(Continuous Tow Shearing, CTS)铺放技术是一种新的变角度层合板制作技术,这种新技术能显著减少丝束铺放过程中产生的丝束重叠和间隙等缺陷,然而,采用CTS技术铺设时,层合板的厚度将随着纤维角度的变化而变化.本文基于一阶...连续丝束剪切(Continuous Tow Shearing, CTS)铺放技术是一种新的变角度层合板制作技术,这种新技术能显著减少丝束铺放过程中产生的丝束重叠和间隙等缺陷,然而,采用CTS技术铺设时,层合板的厚度将随着纤维角度的变化而变化.本文基于一阶剪切变形理论并应用Chebyshev-Ritz法对这种变厚度的变角度复合材料层合板的热屈曲问题进行了研究.假设纤维方向角沿板的长度方向按照线性变化,获得了均匀温度变化时变厚度层合板的临界热屈曲荷载.通过与现有文献的比较验证了本文方法的正确性,并进一步讨论了纤维铺设技术、纤维方向角的变化以及边界条件的不同对变角度复合材料层合板的临界屈曲温度的影响.研究结果表明,在体积相同的情况下,采用CTS铺设较传统的自动丝束铺放(AFP)可以进一步提升变角度层合板的临界屈曲温度.本文的研究结果可为变角度复合材料的设计提供一定的参考.展开更多
A rotating axisymmetric circular nanoplate is modeled by the Mindlin plate theory.The Mindlin plate theory incorporates the nonlocal scale and strain gradient effects.The shear deformation of the circular nanoplate is...A rotating axisymmetric circular nanoplate is modeled by the Mindlin plate theory.The Mindlin plate theory incorporates the nonlocal scale and strain gradient effects.The shear deformation of the circular nanoplate is considered and the nonlocal strain gradient theory is utilized to derive the governing differential equation of motion that describes the out-of-plane free vibration behaviors of the nanoplate.The differential quadrature method is used to solve the governing equation numerically,and the natural frequencies of the out-of-plane vibration of rotating nanoplates are obtained accordingly.Two kinds of boundary conditions are commonly used in practical engineering,namely the fixed and simply supported constraints,and are considered in numerical examples.The variations of natural frequencies with respect to the thickness to radius ratio,the angular velocity,the nonlocal characteristic scale and the material characteristic scale are analyzed in detail.In particular,the critical angular velocity that measures whether the rotating circular nanoplate is stable or not is obtained numerically.The presented study has reference significance for the dynamic design and control of rotating circular nanostructures in current nano-technologies and nano-devices.展开更多
Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and ste...Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.展开更多
The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures hav...The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carded out to investigate the influence of essential parameters on the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.展开更多
文摘连续丝束剪切(Continuous Tow Shearing, CTS)铺放技术是一种新的变角度层合板制作技术,这种新技术能显著减少丝束铺放过程中产生的丝束重叠和间隙等缺陷,然而,采用CTS技术铺设时,层合板的厚度将随着纤维角度的变化而变化.本文基于一阶剪切变形理论并应用Chebyshev-Ritz法对这种变厚度的变角度复合材料层合板的热屈曲问题进行了研究.假设纤维方向角沿板的长度方向按照线性变化,获得了均匀温度变化时变厚度层合板的临界热屈曲荷载.通过与现有文献的比较验证了本文方法的正确性,并进一步讨论了纤维铺设技术、纤维方向角的变化以及边界条件的不同对变角度复合材料层合板的临界屈曲温度的影响.研究结果表明,在体积相同的情况下,采用CTS铺设较传统的自动丝束铺放(AFP)可以进一步提升变角度层合板的临界屈曲温度.本文的研究结果可为变角度复合材料的设计提供一定的参考.
基金supported by the Natural Science Foundation of China(No.11972240)the China Postdoctoral Science Foundation(No.2020M671574)the University Natural Science Research Project of Anhui Province(No.KJ2018A0481).
文摘A rotating axisymmetric circular nanoplate is modeled by the Mindlin plate theory.The Mindlin plate theory incorporates the nonlocal scale and strain gradient effects.The shear deformation of the circular nanoplate is considered and the nonlocal strain gradient theory is utilized to derive the governing differential equation of motion that describes the out-of-plane free vibration behaviors of the nanoplate.The differential quadrature method is used to solve the governing equation numerically,and the natural frequencies of the out-of-plane vibration of rotating nanoplates are obtained accordingly.Two kinds of boundary conditions are commonly used in practical engineering,namely the fixed and simply supported constraints,and are considered in numerical examples.The variations of natural frequencies with respect to the thickness to radius ratio,the angular velocity,the nonlocal characteristic scale and the material characteristic scale are analyzed in detail.In particular,the critical angular velocity that measures whether the rotating circular nanoplate is stable or not is obtained numerically.The presented study has reference significance for the dynamic design and control of rotating circular nanostructures in current nano-technologies and nano-devices.
文摘Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.
文摘The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carded out to investigate the influence of essential parameters on the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.
