Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achie...Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.展开更多
In order to continuously simulate multi-pass plate rolling process,a 3-D elastic hollow-roll model was proposed and an auto mesh-refining module with data passing was developed and integrated with FE software,Marc.The...In order to continuously simulate multi-pass plate rolling process,a 3-D elastic hollow-roll model was proposed and an auto mesh-refining module with data passing was developed and integrated with FE software,Marc.The hollow-roll model has equivalent stiffness of bending resistance and deformation to the real solid and much less meshes,so the computational time is greatly reduced.Based on these,the factors influencing plate profile,such as the roll-bending force,initial crown,thermal crown and heat transfer during rolling and inter-pass cooling can be taken into account in the simulation.The auto mesh-refining module with data passing can automatically refine and re-number elements and transfer the nodal and elemental results to the new meshes.Furthermore,the 3-D modeling routine is parametrically developed and can be run independently of Marc pre-processing program.A seven-pass industrial hot rolling process was continuously simulated to validate the accuracy of model.By comparison of the calculated results with the industrial measured data,the rolling force,temperature and plate profile are in good accordance with the measured ones.展开更多
The dynamic performance and wake structure of flapping plates with different shapes were studied using multi-block lattice Boltzman and immersed boundary method.Two typical regimes relevant to thrust behavior are iden...The dynamic performance and wake structure of flapping plates with different shapes were studied using multi-block lattice Boltzman and immersed boundary method.Two typical regimes relevant to thrust behavior are identified.One is nonlinear relation between the thrust and the area moment of plate for lower area moment region and the other is linear relation for larger area moment region.The tendency of the power variation with the area moment is reasonably similar to the thrust behavior and the efficiency decreases gradually as the area moment increases.As the mechanism of the dynamic properties is associated with the evolution of vortical structures around the plate,the formation and evolution of vortical structures are investigated and the effects of the plate shape,plate area,Strouhal number and Reynolds number on the vortical structures are analyzed.The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to flapping locomotion.展开更多
Roll flattening theory is an important part of plate shape control theories for 20-high mill. In order to improve the accuracy of roll flattening calculation for 20-high mill, a new and more accurate roll flattening m...Roll flattening theory is an important part of plate shape control theories for 20-high mill. In order to improve the accuracy of roll flattening calculation for 20-high mill, a new and more accurate roll flattening model was proposed. In this model, the roll barrel was considered as a finite length semi-infinite body. Based on the boundary integral equation method, the numerical solution of the finite length semi-infinite body under the distributed force was obtained and an accurate roll flattening model was established. Coupled with roll bending model and strip plastic deformation, a new and more accurate plate control model for 20-high mill was established. Moreover, the effects of the first intermediate roll taper angle and taper length were analyzed. The tension distribution calculated by analytical model was consistent with the experimental results.展开更多
This paper focuses on the process for pillow shape plate by line heating technique, which is widely applied in the production of ship hull. Based on the analysis of primary parameters and experimental data in line hea...This paper focuses on the process for pillow shape plate by line heating technique, which is widely applied in the production of ship hull. Based on the analysis of primary parameters and experimental data in line heating process, the amount of local contraction generated by line heating has been illustrated. Then, combining with the computational result of local deformation determined by shell plate development, an optimization method for line heating parameters has been studied. This prediction system may provide rational arrangements of heating lines and technical parameters of process. By integrating the prediction system into the line heating robot for pillow shape plate, the automatic process of line heating for pillow shape plate can be achieved.展开更多
AGC system can improve the plate gauge precision,and damage the plate shape if the shape control loop is left quite open.This damage will cause wave during rolling wide-thin plate.A control strategy named shape lock-o...AGC system can improve the plate gauge precision,and damage the plate shape if the shape control loop is left quite open.This damage will cause wave during rolling wide-thin plate.A control strategy named shape lock-on method is afforded for plate shape control.This method requires APC instead of AGC at last one or two passes during rolling wide-thin plate.Approved by theory and on-line application,this method is good for the plate shape and crown control with small effect on gauge control.展开更多
Based on the wave radiation and diffraction theory, this paper investigates a new type breakwater with upper arcshaped plate by using the boundary element method(BEM). By comparing with other three designs of plate ty...Based on the wave radiation and diffraction theory, this paper investigates a new type breakwater with upper arcshaped plate by using the boundary element method(BEM). By comparing with other three designs of plate type breakwater(lower arc-shaped plate, single horizontal plate and double horizontal plate), this new type breakwater has been proved more effective. The wave exiting force, transmission and reflection coefficients are analyzed and discussed. In order to reveal the wave elimination mechanism of this type of breakwater, the velocity field around the breakwater is obtained. It is shown that:(1) The sway exciting force is minimal.(2) When the ratio of the submergence and wave amplitude is 0.05, the wave elimination effect will increase by 50% compared with other three types of breakwater.(3) The obvious backflow is found above the plate in the velocity field analysis.展开更多
In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power ...In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.展开更多
Multi- pass spray deposition shows apparent advantages in preparing large scale plates with rapid solidification. Shape model is promoted to obtain excellent shape. Three dimensional mathematical models considering mo...Multi- pass spray deposition shows apparent advantages in preparing large scale plates with rapid solidification. Shape model is promoted to obtain excellent shape. Three dimensional mathematical models considering motion of atomization cone and substrate, deposition distance and atomization parameters were used to predict deposited plate’s shape. The results can be used to optimize the process parameters.展开更多
In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a p...In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a plate-shaped absorber is given in this paper.In the example,the frequency of the full-size measurement ranges from 2.0 GHz to 2.4 GHz,the thickness of the full-size absorber is 1 mm and the scale ratio is 1/5.A two-layer scale absorber is obtained by the proposed method.The thickness values of the bottom and top layer are 0.4 mm and 0.5 mm,respectively.Furthermore,the scattering properties of a plate model and an SLICY model are studied by FEKO to verify the effectiveness of the designed scale absorber.Compared with the corresponding values from the theoretical scale model,the average values of the absolute deviations in 10 GHz～12 GHz are 0.53 d Bm^2,0.65 d Bm^2,0.76 d Bm^2 for the plate model and 0.20 d Bm^2,0.95 d Bm^2,0.77 d Bm^2 for the SLICY model while the incident angles are 0°,30°,and 60°,respectively.These deviations fall within the Radar cross section（RCS） measurement tolerance.Thus,the work in this paper has important theoretical and practical significance.展开更多
Improvement from the pseudo-elastic effect of shape memory alloy （SMA） on the low-velocity impact （LVI） resistance of a composite plate is investigated by the finite element method （FEM）. The stiffness matrix of...Improvement from the pseudo-elastic effect of shape memory alloy （SMA） on the low-velocity impact （LVI） resistance of a composite plate is investigated by the finite element method （FEM）. The stiffness matrix of the dynamic finite element equation is established step by step and the martensite fraction is obtained at each time step. The direct Newmark integration method is employed in solving the dynamic finite element equation, while the impact contact force is determined using the modified Hertz＇s law. It is found that SMA can effectively improve the performance of a composite structure subjected to low-velocity impact. Numerical results show that the deflection of a SMA-hybrid composite plate has been reduced approximately by thirty percent when the volume fraction of the embedded SMA reaches 0.3.展开更多
Aerodynamics of circular plate- and circular ring-shaped squeeze film hearings is analyzed in detail, yielding analytic expressions for the pressure distribution of these hearings. Several formulae for these hearings ...Aerodynamics of circular plate- and circular ring-shaped squeeze film hearings is analyzed in detail, yielding analytic expressions for the pressure distribution of these hearings. Several formulae for these hearings are modified using the developed method. The paper also gives numerical results oj pressure distribution and load-hearing capacities of these hearings.展开更多
The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the su...The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the supposition that the stresses in each plate can be approximated by a plane stress condition. The results obtained are verified by numerical calculation of FEM.展开更多
At the present time, ultrasonic motors have been developed for a variety of purposes such as linear motion drives and rotational drives. The elaboration of an ultrasonic motor is time-consuming, because it is develope...At the present time, ultrasonic motors have been developed for a variety of purposes such as linear motion drives and rotational drives. The elaboration of an ultrasonic motor is time-consuming, because it is developed adapting on its application. In this study, a new ultrasonic motor structure that combines a piezoelectric element and a metallic plate is elaborated. The driving principle of this motor is that the metal plate is bent to an inchworm shape and rotates the rotor when the piezoelectric element is stretched. The objective of this study is to verify the functioning of the new motor experimentally.展开更多
The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared b...The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared based on an SMA plate, and combined into a GMF-SMA composite plate. The Van der Pol item is improved to explain the hysteretic phenomena of GMF and SMA, and the nonlinear dynamics model of a GMF-SMA composite cantilever plate subjected to in-plane stochastic excitation is developed. The stochastic stability of the system is analyzed, and the steady-state probability density function of the dynamic response of the system is obtained. The condition of stochastic Hopf bifurcation is discussed, the reliability function of the system is provided, and then the probability density of the first-passage time is given. Finally, the stochastic optimal control strategy is proposed by the stochastic dynamic programming method. Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the system＇s reliability is improved through stochastic optimal control, and the first- passage time is delayed. A GMF-SMA composite plate combines the advantages of GMF and SMA, and can reduce vibration through passive control and active control effectively. The results are helpful for the engineering applications of GMF-SMA composite plates.展开更多
By applying the Heaviside function, the equations governinglaminated plates possess- ing spatially distributed piezoelectricpatches have been established. Based on these equations, static shapecontrol of laminated pla...By applying the Heaviside function, the equations governinglaminated plates possess- ing spatially distributed piezoelectricpatches have been established. Based on these equations, static shapecontrol of laminated plates is discussed. BY using a genetic andcollocation algorithm, the opti- mal locations and scales of thesepiezoelectric patches have been selected. Numerical examples are pre-sented to illustrate the efficiency of the algorithm and thepiezoelectric actuators.展开更多
A novel A1GaN/GaN high electron mobility transistor （HEMT） with a source-connected T-shaped field-plate （ST-FP HEMT） is proposed for the first time in this paper. The source-connected T-shaped field-plate （ST-FP...A novel A1GaN/GaN high electron mobility transistor （HEMT） with a source-connected T-shaped field-plate （ST-FP HEMT） is proposed for the first time in this paper. The source-connected T-shaped field-plate （ST-FP） is composed of a source-connected field-plate （S-FP） and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP （S-FP HEMT） shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications.展开更多
The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-...The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-Al SMA engendered dezincification corrosion in Tyrode'ssolution. The anodic active current densities as well as electrochemical dissolution sensitivity ofthe electroless plated Ni-P Cu-Zn-Al SMA increased with NaCl concentration rising, pH of solutiondecreasing and environmental temperature uprising. X-ray diffraction analysis indicated that aftersurface modification by electroless plated Ni-P, an amorphous plated film formed on the surface ofCu-Zn-Al SMA. This film can effectively isolate matrix metal from corrosion media and significantlyimprove the electrochemical property of Cu-Zn-Al SMA in artificial Tyrode's solution.展开更多
基金Projects(51104043,51374067)supported by the National Natural Science Foundation of ChinaProject(2012CB619506)supported by the National Basic Research Program of ChinaProject(N120409002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.
基金Project(20050248007) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘In order to continuously simulate multi-pass plate rolling process,a 3-D elastic hollow-roll model was proposed and an auto mesh-refining module with data passing was developed and integrated with FE software,Marc.The hollow-roll model has equivalent stiffness of bending resistance and deformation to the real solid and much less meshes,so the computational time is greatly reduced.Based on these,the factors influencing plate profile,such as the roll-bending force,initial crown,thermal crown and heat transfer during rolling and inter-pass cooling can be taken into account in the simulation.The auto mesh-refining module with data passing can automatically refine and re-number elements and transfer the nodal and elemental results to the new meshes.Furthermore,the 3-D modeling routine is parametrically developed and can be run independently of Marc pre-processing program.A seven-pass industrial hot rolling process was continuously simulated to validate the accuracy of model.By comparison of the calculated results with the industrial measured data,the rolling force,temperature and plate profile are in good accordance with the measured ones.
基金supported by the National Natural Science Foundation of China(11372304 and 11132010)the 111 Project(B07033)
文摘The dynamic performance and wake structure of flapping plates with different shapes were studied using multi-block lattice Boltzman and immersed boundary method.Two typical regimes relevant to thrust behavior are identified.One is nonlinear relation between the thrust and the area moment of plate for lower area moment region and the other is linear relation for larger area moment region.The tendency of the power variation with the area moment is reasonably similar to the thrust behavior and the efficiency decreases gradually as the area moment increases.As the mechanism of the dynamic properties is associated with the evolution of vortical structures around the plate,the formation and evolution of vortical structures are investigated and the effects of the plate shape,plate area,Strouhal number and Reynolds number on the vortical structures are analyzed.The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to flapping locomotion.
基金Item Sponsored by National Natural Science Foundation of China(51474190)Natural Sceince Foundation of Hebei Province of China(E2015203311)
文摘Roll flattening theory is an important part of plate shape control theories for 20-high mill. In order to improve the accuracy of roll flattening calculation for 20-high mill, a new and more accurate roll flattening model was proposed. In this model, the roll barrel was considered as a finite length semi-infinite body. Based on the boundary integral equation method, the numerical solution of the finite length semi-infinite body under the distributed force was obtained and an accurate roll flattening model was established. Coupled with roll bending model and strip plastic deformation, a new and more accurate plate control model for 20-high mill was established. Moreover, the effects of the first intermediate roll taper angle and taper length were analyzed. The tension distribution calculated by analytical model was consistent with the experimental results.
文摘This paper focuses on the process for pillow shape plate by line heating technique, which is widely applied in the production of ship hull. Based on the analysis of primary parameters and experimental data in line heating process, the amount of local contraction generated by line heating has been illustrated. Then, combining with the computational result of local deformation determined by shell plate development, an optimization method for line heating parameters has been studied. This prediction system may provide rational arrangements of heating lines and technical parameters of process. By integrating the prediction system into the line heating robot for pillow shape plate, the automatic process of line heating for pillow shape plate can be achieved.
基金Item Sponsored by National Natural Science Foundation of China(50104004)
文摘AGC system can improve the plate gauge precision,and damage the plate shape if the shape control loop is left quite open.This damage will cause wave during rolling wide-thin plate.A control strategy named shape lock-on method is afforded for plate shape control.This method requires APC instead of AGC at last one or two passes during rolling wide-thin plate.Approved by theory and on-line application,this method is good for the plate shape and crown control with small effect on gauge control.
基金financially supported by the National Key Basic Research Program of China(Grant No.2013CB036101)the National Natural Science Foundation of China(Grant No.11702054)
文摘Based on the wave radiation and diffraction theory, this paper investigates a new type breakwater with upper arcshaped plate by using the boundary element method(BEM). By comparing with other three designs of plate type breakwater(lower arc-shaped plate, single horizontal plate and double horizontal plate), this new type breakwater has been proved more effective. The wave exiting force, transmission and reflection coefficients are analyzed and discussed. In order to reveal the wave elimination mechanism of this type of breakwater, the velocity field around the breakwater is obtained. It is shown that:(1) The sway exciting force is minimal.(2) When the ratio of the submergence and wave amplitude is 0.05, the wave elimination effect will increase by 50% compared with other three types of breakwater.(3) The obvious backflow is found above the plate in the velocity field analysis.
基金supported by the National Basic Research Programof China (2011CB711102)the National Natural Science Foundation of China (10672017,11002045)
文摘In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.
文摘Multi- pass spray deposition shows apparent advantages in preparing large scale plates with rapid solidification. Shape model is promoted to obtain excellent shape. Three dimensional mathematical models considering motion of atomization cone and substrate, deposition distance and atomization parameters were used to predict deposited plate’s shape. The results can be used to optimize the process parameters.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61601299 and 11404213)the Shanghai Municipal Science and Technology Commission,China(Grant Nos.17210730900 and 15ZR1439600)the Defense Industrial Technology,China(Grant No.B2120132001)
文摘In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a plate-shaped absorber is given in this paper.In the example,the frequency of the full-size measurement ranges from 2.0 GHz to 2.4 GHz,the thickness of the full-size absorber is 1 mm and the scale ratio is 1/5.A two-layer scale absorber is obtained by the proposed method.The thickness values of the bottom and top layer are 0.4 mm and 0.5 mm,respectively.Furthermore,the scattering properties of a plate model and an SLICY model are studied by FEKO to verify the effectiveness of the designed scale absorber.Compared with the corresponding values from the theoretical scale model,the average values of the absolute deviations in 10 GHz～12 GHz are 0.53 d Bm^2,0.65 d Bm^2,0.76 d Bm^2 for the plate model and 0.20 d Bm^2,0.95 d Bm^2,0.77 d Bm^2 for the SLICY model while the incident angles are 0°,30°,and 60°,respectively.These deviations fall within the Radar cross section（RCS） measurement tolerance.Thus,the work in this paper has important theoretical and practical significance.
基金Project supported by the Key Project for Science and Technology Study of Ministry of Education of China (No.00085).
文摘Improvement from the pseudo-elastic effect of shape memory alloy （SMA） on the low-velocity impact （LVI） resistance of a composite plate is investigated by the finite element method （FEM）. The stiffness matrix of the dynamic finite element equation is established step by step and the martensite fraction is obtained at each time step. The direct Newmark integration method is employed in solving the dynamic finite element equation, while the impact contact force is determined using the modified Hertz＇s law. It is found that SMA can effectively improve the performance of a composite structure subjected to low-velocity impact. Numerical results show that the deflection of a SMA-hybrid composite plate has been reduced approximately by thirty percent when the volume fraction of the embedded SMA reaches 0.3.
文摘Aerodynamics of circular plate- and circular ring-shaped squeeze film hearings is analyzed in detail, yielding analytic expressions for the pressure distribution of these hearings. Several formulae for these hearings are modified using the developed method. The paper also gives numerical results oj pressure distribution and load-hearing capacities of these hearings.
文摘The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the supposition that the stresses in each plate can be approximated by a plane stress condition. The results obtained are verified by numerical calculation of FEM.
文摘At the present time, ultrasonic motors have been developed for a variety of purposes such as linear motion drives and rotational drives. The elaboration of an ultrasonic motor is time-consuming, because it is developed adapting on its application. In this study, a new ultrasonic motor structure that combines a piezoelectric element and a metallic plate is elaborated. The driving principle of this motor is that the metal plate is bent to an inchworm shape and rotates the rotor when the piezoelectric element is stretched. The objective of this study is to verify the functioning of the new motor experimentally.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11272229 and 11302144)the Ph.D.Programs Foundation of the Ministry of Education of China(Grant No.20120032120006)the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.13JCYBJC17900)
文摘The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared based on an SMA plate, and combined into a GMF-SMA composite plate. The Van der Pol item is improved to explain the hysteretic phenomena of GMF and SMA, and the nonlinear dynamics model of a GMF-SMA composite cantilever plate subjected to in-plane stochastic excitation is developed. The stochastic stability of the system is analyzed, and the steady-state probability density function of the dynamic response of the system is obtained. The condition of stochastic Hopf bifurcation is discussed, the reliability function of the system is provided, and then the probability density of the first-passage time is given. Finally, the stochastic optimal control strategy is proposed by the stochastic dynamic programming method. Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the system＇s reliability is improved through stochastic optimal control, and the first- passage time is delayed. A GMF-SMA composite plate combines the advantages of GMF and SMA, and can reduce vibration through passive control and active control effectively. The results are helpful for the engineering applications of GMF-SMA composite plates.
文摘By applying the Heaviside function, the equations governinglaminated plates possess- ing spatially distributed piezoelectricpatches have been established. Based on these equations, static shapecontrol of laminated plates is discussed. BY using a genetic andcollocation algorithm, the opti- mal locations and scales of thesepiezoelectric patches have been selected. Numerical examples are pre-sented to illustrate the efficiency of the algorithm and thepiezoelectric actuators.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574112,61334002,61306017,61474091,and 61574110)the Natural Science Basic Research Plan in Shaanxi Province,China(Grant No.605119425012)
文摘A novel A1GaN/GaN high electron mobility transistor （HEMT） with a source-connected T-shaped field-plate （ST-FP HEMT） is proposed for the first time in this paper. The source-connected T-shaped field-plate （ST-FP） is composed of a source-connected field-plate （S-FP） and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP （S-FP HEMT） shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications.
文摘The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-Al SMA engendered dezincification corrosion in Tyrode'ssolution. The anodic active current densities as well as electrochemical dissolution sensitivity ofthe electroless plated Ni-P Cu-Zn-Al SMA increased with NaCl concentration rising, pH of solutiondecreasing and environmental temperature uprising. X-ray diffraction analysis indicated that aftersurface modification by electroless plated Ni-P, an amorphous plated film formed on the surface ofCu-Zn-Al SMA. This film can effectively isolate matrix metal from corrosion media and significantlyimprove the electrochemical property of Cu-Zn-Al SMA in artificial Tyrode's solution.
