It is of great practical importance to analyze the shakedown of shell structures under cyclic loading, especially of those made of strain hardening materials.In this paper, same further understanding of the shakedown ...It is of great practical importance to analyze the shakedown of shell structures under cyclic loading, especially of those made of strain hardening materials.In this paper, same further understanding of the shakedown theorem for kinematic hardening materials has been made, and it is applied to analyze the shakedown of shell structures Though the residual stress of a real stale is related to plastic strain, the time-independent residual stress field as we will show in the theorem may be unrelated to the time-independent kinematically admissible plastic strain field For the engineering application, it will lie much more convenient to point this out clearly and definitely, otherwise it will be very difficult. Also, we have proposed a new method of proving this theorem.The above theorem is applied to the shakedown analysis of a cylindrical shell with hemispherical ends. According to the elastic solution, various possible residual sfcss and plastic strain Jlelds, the shakedown analysis of the structure can be reduced to a mathematical programming problem.The results of calculation show that the shakedown load oj strain hardening materials is about 30-40% higher than that of ideal plastic materials. So it is very important to consider the hardening of materials in the shakedown analysis,for it can greatly increase the structure design capacity, and meanwhile provide ascicntific basis to improve the design of shell structures.展开更多
In this paper, the nonlinear analysis of stability of functionally graded ma- terial (FGM) sandwich doubly curved shallow shells is studied under thermo-mechanical loads with material properties obeying the general ...In this paper, the nonlinear analysis of stability of functionally graded ma- terial (FGM) sandwich doubly curved shallow shells is studied under thermo-mechanical loads with material properties obeying the general sigmoid law and power law of four ma- terial models. Shells are reinforced by the FGM stiffeners and rest on elastic foundations. Theoretical formulations are derived by the third-order shear deformation theory (TSDT) with the von Karman-type nonlinearity taking into account the initial geometrical im- perfection and smeared stiffener technique. The explicit expressions for determining the critical buckling load and the post-buckling mechanical and thermal load-deflection curves are obtained by the Galerkin method. Two iterative algorithms are presented. The effects of the stiffeners, the thermal element, the distribution law of material, the initial imper- fection, the foundation, and the geometrical parameters on buckling and post-buckling of shells are investigated.展开更多
Copper/liquid microcapsule composite coatings with polyvinyl alcohol (PVA), gelatin or methyl cellulose (MC) as shell materials were prepared by electrodeposition. The influence of shell materials on the corrosion...Copper/liquid microcapsule composite coatings with polyvinyl alcohol (PVA), gelatin or methyl cellulose (MC) as shell materials were prepared by electrodeposition. The influence of shell materials on the corrosion resistance of the composite coatings in 0.1 M H2SO4 was investigated by means of electrochemical techniques, scanning electron microscopy (SEM), and energy dispersion spectrometry (EDS). The results show that the participation of microcapsules can enhance the corrosion resistance of the composite coatings compared with the traditional copper layer. Based on the analysis of electrochemical test results, the release ways of microcapsules were deduced. Gelatin and MC as the shell materials of microcapsules are easy to release quickly in the composite coating. On the contrary, the releasing speed of PVA microcapsules is relatively slow due to their characteristics.展开更多
An analytical method for the three-dimensional vibration analysis of a functionally graded cylindrical shell integrated by two thin functionally graded piezoelectric (FGP) layers is presented. The first-order shear ...An analytical method for the three-dimensional vibration analysis of a functionally graded cylindrical shell integrated by two thin functionally graded piezoelectric (FGP) layers is presented. The first-order shear deformation theory is used to model the electromechanical system. Nonlinear equations of motion are derived by considering the von Karman nonlinear strain-displacement relations using Hamilton's principle. The piezoelectric layers on the inner and outer surfaces of the core can be considered as a sensor and an actuator for controlling characteristic vibration of the system. The equations of motion are derived as partial differential equations and then discretized by the Navier method. Numerical simulation is performed to investigate the effect of different para- meters of material and geometry on characteristic vibration of the cylinder. The results of this study show that the natural frequency of the system decreases by increasing the non-homogeneous index of FGP layers and decreases by increasing the non-homogeneous index of the functionally graded core. Furthermore, it is concluded that by increasing the ratio of core thickness to cylinder length, the natural frequencies of the cylinder increase considerably.展开更多
By using the energy criterion in [3], the impact torsional buckling for the rigid plastic cylindrical shell is studied. The linear dynamic torsional buckling equations for the rigid plastic shell is drived, and the cr...By using the energy criterion in [3], the impact torsional buckling for the rigid plastic cylindrical shell is studied. The linear dynamic torsional buckling equations for the rigid plastic shell is drived, and the critical impact velocity is given.展开更多
Encapsulation in food industry serves several functions including masking of undesirable color/flavor/taste, preservation of unstable constituents, incor<span style="font-family:Verdana;">poration of a...Encapsulation in food industry serves several functions including masking of undesirable color/flavor/taste, preservation of unstable constituents, incor<span style="font-family:Verdana;">poration of additional functional and nutritional components and site-specific</span><span style="font-family:Verdana;"> release of encapsulated ingredients at a controlled time and rate. The knowledge of microencapsulation in other sectors like pharmaceutical industry is well advanced;however, more understanding is required to harvest the maximum benefits from food industry. This paper started with highlighting the gradual progress of microencapsulation process in food industry and ended up with some invaluable suggestions for future works. In the body, the paper reviews the major techniques of food encapsulation, choices of coating materials and the performance measurement methods of food encapsulation. Future trends, scopes and aspects of microencapsulation process in food manufacturing sector are also presented as the necessary recommendations for future researches. The article would help the microencapsulated food manufacturers to choose the target oriented encapsulates and suitable encapsulation technique.</span>展开更多
文摘It is of great practical importance to analyze the shakedown of shell structures under cyclic loading, especially of those made of strain hardening materials.In this paper, same further understanding of the shakedown theorem for kinematic hardening materials has been made, and it is applied to analyze the shakedown of shell structures Though the residual stress of a real stale is related to plastic strain, the time-independent residual stress field as we will show in the theorem may be unrelated to the time-independent kinematically admissible plastic strain field For the engineering application, it will lie much more convenient to point this out clearly and definitely, otherwise it will be very difficult. Also, we have proposed a new method of proving this theorem.The above theorem is applied to the shakedown analysis of a cylindrical shell with hemispherical ends. According to the elastic solution, various possible residual sfcss and plastic strain Jlelds, the shakedown analysis of the structure can be reduced to a mathematical programming problem.The results of calculation show that the shakedown load oj strain hardening materials is about 30-40% higher than that of ideal plastic materials. So it is very important to consider the hardening of materials in the shakedown analysis,for it can greatly increase the structure design capacity, and meanwhile provide ascicntific basis to improve the design of shell structures.
基金Project supported by the Vietnam National Foundation for Science and Technology Development(No.107.02-2015.11)
文摘In this paper, the nonlinear analysis of stability of functionally graded ma- terial (FGM) sandwich doubly curved shallow shells is studied under thermo-mechanical loads with material properties obeying the general sigmoid law and power law of four ma- terial models. Shells are reinforced by the FGM stiffeners and rest on elastic foundations. Theoretical formulations are derived by the third-order shear deformation theory (TSDT) with the von Karman-type nonlinearity taking into account the initial geometrical im- perfection and smeared stiffener technique. The explicit expressions for determining the critical buckling load and the post-buckling mechanical and thermal load-deflection curves are obtained by the Galerkin method. Two iterative algorithms are presented. The effects of the stiffeners, the thermal element, the distribution law of material, the initial imper- fection, the foundation, and the geometrical parameters on buckling and post-buckling of shells are investigated.
基金supported by the National Natural Science Foundation of China (No. 50771010)
文摘Copper/liquid microcapsule composite coatings with polyvinyl alcohol (PVA), gelatin or methyl cellulose (MC) as shell materials were prepared by electrodeposition. The influence of shell materials on the corrosion resistance of the composite coatings in 0.1 M H2SO4 was investigated by means of electrochemical techniques, scanning electron microscopy (SEM), and energy dispersion spectrometry (EDS). The results show that the participation of microcapsules can enhance the corrosion resistance of the composite coatings compared with the traditional copper layer. Based on the analysis of electrochemical test results, the release ways of microcapsules were deduced. Gelatin and MC as the shell materials of microcapsules are easy to release quickly in the composite coating. On the contrary, the releasing speed of PVA microcapsules is relatively slow due to their characteristics.
基金supported by the University of Kashan(Nos.574613/01 and 574619/02)
文摘An analytical method for the three-dimensional vibration analysis of a functionally graded cylindrical shell integrated by two thin functionally graded piezoelectric (FGP) layers is presented. The first-order shear deformation theory is used to model the electromechanical system. Nonlinear equations of motion are derived by considering the von Karman nonlinear strain-displacement relations using Hamilton's principle. The piezoelectric layers on the inner and outer surfaces of the core can be considered as a sensor and an actuator for controlling characteristic vibration of the system. The equations of motion are derived as partial differential equations and then discretized by the Navier method. Numerical simulation is performed to investigate the effect of different para- meters of material and geometry on characteristic vibration of the cylinder. The results of this study show that the natural frequency of the system decreases by increasing the non-homogeneous index of FGP layers and decreases by increasing the non-homogeneous index of the functionally graded core. Furthermore, it is concluded that by increasing the ratio of core thickness to cylinder length, the natural frequencies of the cylinder increase considerably.
基金Project supported by the National Natural Science Foundation of China
文摘By using the energy criterion in [3], the impact torsional buckling for the rigid plastic cylindrical shell is studied. The linear dynamic torsional buckling equations for the rigid plastic shell is drived, and the critical impact velocity is given.
文摘Encapsulation in food industry serves several functions including masking of undesirable color/flavor/taste, preservation of unstable constituents, incor<span style="font-family:Verdana;">poration of additional functional and nutritional components and site-specific</span><span style="font-family:Verdana;"> release of encapsulated ingredients at a controlled time and rate. The knowledge of microencapsulation in other sectors like pharmaceutical industry is well advanced;however, more understanding is required to harvest the maximum benefits from food industry. This paper started with highlighting the gradual progress of microencapsulation process in food industry and ended up with some invaluable suggestions for future works. In the body, the paper reviews the major techniques of food encapsulation, choices of coating materials and the performance measurement methods of food encapsulation. Future trends, scopes and aspects of microencapsulation process in food manufacturing sector are also presented as the necessary recommendations for future researches. The article would help the microencapsulated food manufacturers to choose the target oriented encapsulates and suitable encapsulation technique.</span>