Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures,flexibility,and attractive appearance.However,the inability of controlling and regulati...Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures,flexibility,and attractive appearance.However,the inability of controlling and regulating vibrations and destroying them afterward is a challenge to scientists.In this paper,the curve shell equations and a linear quadratic regulator are adopted for the state feedback design to manage the structure vibrations in state space forms.A five-layer sandwich doubly curved micro-composite shell,comprising two piezoelectric layers for the sensor and actuator,is modeled by the fourth-order shear deformation theory.The core(honeycomb,truss,and corrugated)is analyzed for the bearing of transverse shear forces.The results show that the honeycomb core has a greater effect on the vibrations.When the parameters related to the core and the weight percentage of graphene increase,the frequency increases.The uniform distribution of graphene platelets results in the lowest natural frequency while the natural frequency increases.Furthermore,without taking into account the piezoelectric layers,the third-order shear deformation theory(TSDT)and fourth-order shear deformation theory(FOSDT)align closely.However,when the piezoelectric layers are incorporated,these two theories diverge significantly,with the frequencies in the FOSDT being lower than those in the TSDT.展开更多
We have fabricated high strength and conductivity Cu-Nb micro-composites by bundling and drawing process. The interface diffusion and microstructure of Cu-17vol% Nb composites experienced severe plastic deformation at...We have fabricated high strength and conductivity Cu-Nb micro-composites by bundling and drawing process. The interface diffusion and microstructure of Cu-17vol% Nb composites experienced severe plastic deformation at different heat treatment conditions are investigated. Diffusion at Cu/Nb interface of Nb filaments is observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The interface characteristic and edge spheroidization of Nb filaments are discussed.展开更多
Corrosion behavior of heavily drawn bundled Copper-niobium filamentarymicro-composite was studied as a function of niobium content to develop the relationship betweenmicrostructure and corrosion behavior in aqueous 30...Corrosion behavior of heavily drawn bundled Copper-niobium filamentarymicro-composite was studied as a function of niobium content to develop the relationship betweenmicrostructure and corrosion behavior in aqueous 30 percent HCl-FeCl_3 solution. TEM observationrevealed that niobium filaments were distributed regularly in copper matrix along the sides of atriangular unit cell in the transverse section and more sub-grain boundaries were absorbed atcopper/niobium phase boundaries with increasing niobium content. The corrosion potential and rate inaqueous 30 percent HCl-10 percent FeCl_3 was-680.3m V_(SHE) and 1.179 X 10^(-5)A/cm^2. Thecorrosion potential and rate decreased as increasing niobium content and FeCl_3. The yield stresscan be described as the sum of the substructure strengthening component due to elongated grains,subgrains and/or cells, the phase boundary strengthening term associated with the Hall-Petch typeinteraction between dislocations and phase boundaries and precipitate strengthening component.展开更多
The hardness measurement,optical microscopy （OM）,and transmission electron microscopy （TEM） microstructure observation on the annealing behaviors of Cu-Al2O3 （2.25 vol.% and 0.54 vol.% Al2O3） and Cu-0.52vol.%Nb ...The hardness measurement,optical microscopy （OM）,and transmission electron microscopy （TEM） microstructure observation on the annealing behaviors of Cu-Al2O3 （2.25 vol.% and 0.54 vol.% Al2O3） and Cu-0.52vol.%Nb alloys were carried out. The results show that with the increase of annealing temperature,the hardness of Cu-Al2O3 alloys decreases slowly. No change of the fiber structure formed by cold rolling in the Cu-2.25vol.%Al2O3 alloy is observed even after annealing at 900℃and the higher dislocation density can still be observed by TEM. Less combination of fiber formed by cold rolling and subgrains are observed in the Cu-0.54vol.%Al2O3 alloy annealed at 900℃. With the increase of annealing temperature,the hardness of the Cu-0.52vol.%Nb alloy exhibits a general decreasing trend,and its falling rate is higher than that of the Cu-Al2O3 alloys,indicating that its ability of resistance to softening at elevated temperature is weaker than that of the Cu-Al2O3 alloys. However,when annealed at a temperature of 300-400℃,probably owing to the precipitation strengthening of niobium,the hardness of the Cu-0.52vol.%Nb alloy arises slightly. The fibers formed by cold rolling be-come un-clear and un-straight and have less combination,and considerably more subgrains are observed by TEM.展开更多
基金the Iranian Nanotechnology Development Committee for their financial supportUniversity of Kashan for supporting this work by Grant No. 1223097/10the micro and nanomechanics laboratory by Grant No. 14022023/5
文摘Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures,flexibility,and attractive appearance.However,the inability of controlling and regulating vibrations and destroying them afterward is a challenge to scientists.In this paper,the curve shell equations and a linear quadratic regulator are adopted for the state feedback design to manage the structure vibrations in state space forms.A five-layer sandwich doubly curved micro-composite shell,comprising two piezoelectric layers for the sensor and actuator,is modeled by the fourth-order shear deformation theory.The core(honeycomb,truss,and corrugated)is analyzed for the bearing of transverse shear forces.The results show that the honeycomb core has a greater effect on the vibrations.When the parameters related to the core and the weight percentage of graphene increase,the frequency increases.The uniform distribution of graphene platelets results in the lowest natural frequency while the natural frequency increases.Furthermore,without taking into account the piezoelectric layers,the third-order shear deformation theory(TSDT)and fourth-order shear deformation theory(FOSDT)align closely.However,when the piezoelectric layers are incorporated,these two theories diverge significantly,with the frequencies in the FOSDT being lower than those in the TSDT.
基金Key Program of National Natural Science Foundation of China (51031002)
文摘We have fabricated high strength and conductivity Cu-Nb micro-composites by bundling and drawing process. The interface diffusion and microstructure of Cu-17vol% Nb composites experienced severe plastic deformation at different heat treatment conditions are investigated. Diffusion at Cu/Nb interface of Nb filaments is observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The interface characteristic and edge spheroidization of Nb filaments are discussed.
文摘Corrosion behavior of heavily drawn bundled Copper-niobium filamentarymicro-composite was studied as a function of niobium content to develop the relationship betweenmicrostructure and corrosion behavior in aqueous 30 percent HCl-FeCl_3 solution. TEM observationrevealed that niobium filaments were distributed regularly in copper matrix along the sides of atriangular unit cell in the transverse section and more sub-grain boundaries were absorbed atcopper/niobium phase boundaries with increasing niobium content. The corrosion potential and rate inaqueous 30 percent HCl-10 percent FeCl_3 was-680.3m V_(SHE) and 1.179 X 10^(-5)A/cm^2. Thecorrosion potential and rate decreased as increasing niobium content and FeCl_3. The yield stresscan be described as the sum of the substructure strengthening component due to elongated grains,subgrains and/or cells, the phase boundary strengthening term associated with the Hall-Petch typeinteraction between dislocations and phase boundaries and precipitate strengthening component.
文摘The hardness measurement,optical microscopy （OM）,and transmission electron microscopy （TEM） microstructure observation on the annealing behaviors of Cu-Al2O3 （2.25 vol.% and 0.54 vol.% Al2O3） and Cu-0.52vol.%Nb alloys were carried out. The results show that with the increase of annealing temperature,the hardness of Cu-Al2O3 alloys decreases slowly. No change of the fiber structure formed by cold rolling in the Cu-2.25vol.%Al2O3 alloy is observed even after annealing at 900℃and the higher dislocation density can still be observed by TEM. Less combination of fiber formed by cold rolling and subgrains are observed in the Cu-0.54vol.%Al2O3 alloy annealed at 900℃. With the increase of annealing temperature,the hardness of the Cu-0.52vol.%Nb alloy exhibits a general decreasing trend,and its falling rate is higher than that of the Cu-Al2O3 alloys,indicating that its ability of resistance to softening at elevated temperature is weaker than that of the Cu-Al2O3 alloys. However,when annealed at a temperature of 300-400℃,probably owing to the precipitation strengthening of niobium,the hardness of the Cu-0.52vol.%Nb alloy arises slightly. The fibers formed by cold rolling be-come un-clear and un-straight and have less combination,and considerably more subgrains are observed by TEM.
