A theoretical model based on BCT lattice structure was developed. Resultant force in the BCT lattice structure was deduced, following the interaction force of two kinds of magnetic particles. According to empirical Fr...A theoretical model based on BCT lattice structure was developed. Resultant force in the BCT lattice structure was deduced, following the interaction force of two kinds of magnetic particles. According to empirical FroHlich-Kermelly law, the relationship between the magnetic induction and the magnetic field was discussed, and a predictive formula of shear stresses of the BCT lattice structure model was established for the case of small shear deformation. Compared with the experimental data for different particle volume fractions, the theoretical results of the shear stress indicate the effects of the saturation magnetization and the external magnetic field on the shear stress.展开更多
Magnetorheological (MR) fluids are now well established as one of the leading materials for use in controllable structures and systems. Commercial application of MR fluids in various fields, particularly in the vibrat...Magnetorheological (MR) fluids are now well established as one of the leading materials for use in controllable structures and systems. Commercial application of MR fluids in various fields, particularly in the vibration control, has grown rapidly over the past few years. In this paper, properties of magnetorheological (MR) fluids ,its applications in suspensions of vehicles, suspension of trains, high buildings cable-stayed bridges have been discussed. The scope of MR fluids in future, problems and some suggestions are also presented. Finally, effectiveness of MR fluids in vibration control of marine diesel engine through experiment is briefly discussed by the author.展开更多
Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40’s). The special applications ...Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40’s). The special applications of these materials as a means of noise suppression are not yet investigated. Constrained Layer Damping (CLD) sheets can be realized by incorporating EMR (ER/MR) materials. In this way, a multilayered damping sheet is obtained with adaptive (tunable) stiffness and damping characteristics. These properties are easily changed in proportion to the electric (magnetic) field applied upon the EMR layer. This notion has been introduced for semi-active vibration control problems. Herein, such panels incorporating EMR material are proposed for adaptive acoustic treatments. Modeling (simulation) of a 3-layered panel with the middle layer being EMR with adjustable properties is carried out in this paper. The tunability of transmission/absorption characteristics of these composite sheets enables us making smart panels for adaptive noise and acoustic treatments. An adaptive performance can be achieved via changing the properties of such panels, on line, according to some sensor outputs. The main objective is to develop proper models to predict the Transmission Loss (TL) of such panels. Also, the TL of this panel is compared with the middle layer of a Newtonian fluid.展开更多
Magnetorheological (MR) fluids consist of stable suspensions of magnetic particles in a carrying fluid such as water or silicone oils. The magnetorheological response of MR fluids results from the polarization induced...Magnetorheological (MR) fluids consist of stable suspensions of magnetic particles in a carrying fluid such as water or silicone oils. The magnetorheological response of MR fluids results from the polarization induced in suspended particles by application of an external magnetic field. The interaction between the induced dipoles causes the particles to form columnar structure, parallel to the applied field. These chain-like structures restrict the motion of fluids, thereby increasing the viscosity and yield stress of the MR fluids. These mechanical characteristics allow for the construction of magnetically controlled device such as the MR fluids rotary brakes. However, there has been little information published about the design of MR fluid brakes. In this paper the design of the cylindrical MR fluid brake is investigated theoretically. Bingham model is used to characterize the constitutive behaviors of the MR fluids subject to an external magnetic field. The operational principle of the cylindrical MR fluid brake is presented. The theoretical method is developed to analyze the transmission properties of the torque of the cylindrical MR fluid brake. An engineering expression for the torque is derived to provide the theoretical foundations in the design of the cylindrical MR fluid brake. Based on this equation the volume and thickness of the annular MR fluids within the brake is expressed as functions of the desired ratio of torques with saturated magnetic field and without external field, the controlled mechanical power and the MR fluid material properties. The parameters of the thickness and width of the fluid in the brake can be calculated from the obtained equations when the required mechanical power level, the desired torque ratio are specified.展开更多
目的:运用 MRI cine PC定量研究交通性脑积水脑室分流前后的脑脊液流动情况。材料和方法:在1.5T GEHorizon Signa磁共振机器上利用MRI cine PC程序,在以前实验所得的液体流速与信号强度关系公式的基础上,对16例交通性脑积水的中脑导水...目的:运用 MRI cine PC定量研究交通性脑积水脑室分流前后的脑脊液流动情况。材料和方法:在1.5T GEHorizon Signa磁共振机器上利用MRI cine PC程序,在以前实验所得的液体流速与信号强度关系公式的基础上,对16例交通性脑积水的中脑导水管、枕大孔和C2水平脑脊液流速、流量情况进行MRI cine PC检查(1.5TGE Horizon Signa),并对其中10例交通性脑积水脑室引流后的中脑导水管和枕大孔处脑脊液的流速和流量同样进行测量,并与术前进行比较。同时作为对照,对31例正常志愿者颅内中脑导水管、枕大孔和C2水平的脑脊液流速和流量进行测定。结果:交通性脑积水中脑导水管水平脑脊液流速和流量明显增快,与正常者进行统计有明显差异(P<0.05),向下峰速和向上峰速分别为47.57±16.71mm/s和44.48±19.22mm/s,向下流量及向上流量明显增大为3.142±1.055ml/s及3.143±1.055ml/s;脑脊液净流量为0±0.003ml/s。而枕大孔向下峰速和向上峰速分别为1.37±0.44mm/s和1.33±0.41mm/s,向下流量及向上流量分别为0.351±0.125ml/s及0.350±0.12lml/s;脑脊液净流量为0.001±0.007ml/s。C2水平脑脊液向下峰速和向上峰速分别为2.41±1.27mm/s和2.95±1.15mm/s,向下流量及向上流量分别为0.521±0.214ml/s和0.519±0.214ml/s;展开更多
Magnetorheological (MR) fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic...Magnetorheological (MR) fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic field, which is known as MR effect, resulting in variation of stiffness, shear modulus, damping and tribological characteristics of MR fluid. As MR effect depends on the density of particles in the fluid or the strength of a magnetic field, the experiments are conducted to evaluate the friction property under reciprocating motion by changing the types of MR fluid and the strength of a magnetic field. The material of aluminum, brass, and steel are chosen for specimen as they are the most common material in mechanical applications. The surfaces of specimen are also observed by optical microscope before and after experiments to compare the surfaces with test conditions. The comparing results show that the friction coefficient increases as the strength of a magnetic field increases in regardless of types of MR fluid or the material. Also the density of particle in MR fluid affects the friction characteristic. The results from this research can be used to improve the performance of mechanical applications using MR fluid.展开更多
This paper presents a linear shear mod magneto-rheological(MR) damper which can be applied to vibration control system.The proposed MR damper featured by a small amount of MR fluid,absence of a gas chamber or diaphrag...This paper presents a linear shear mod magneto-rheological(MR) damper which can be applied to vibration control system.The proposed MR damper featured by a small amount of MR fluid,absence of a gas chamber or diaphragm and piston with helix slotted.Because of the absence of a gas chamber or diaphragm,unnecessary damping force caused by gas compression is not generated.Magnitude and damping coefficient of damping force are two important indexes to evaluate performance of MR damper.The piston with helix slotted is developed based on mechanical analysis on rheological characteristics of MR damper,and the damping performance of MR damper with helix slotted piston is investigated through performance experiments and comparison with analytical simulation.The results indicate that helix slot may increase friction coefficient on surface of the piston,and improve the maximum damping force without reducing damping coefficient of the damper.The reflux of MR fluid may be increased by adjusting helix angle suitably,which avoids the settlement of MR fluid.展开更多
An asymmetric damping force generation algorithm is originally proposed to yield the asymmetric force-velocity characteristics for the symmetric magneto-rheological (MR) dampers. The command current is formulated in...An asymmetric damping force generation algorithm is originally proposed to yield the asymmetric force-velocity characteristics for the symmetric magneto-rheological (MR) dampers. The command current is formulated in an asymmetric manner to excite the symmetric MR dampers by employing the “on-off” control law in response to the direction of velocity, and a smooth modulation function is developed without phase shift to suppress strong transients in the damping forces caused by the current-switching discontinuity. The effectiveness of the proposed algorithm is evaluated by analyzing the dynamic responses of a quarter-vehicle suspension system with a symmetric MR-damper by modulating the command current into the asymmetric manner. The simulation results show that the proposed algorithm could achieve a better compromise between the conflicting requirements of the asymmetric damping force ratio and the force-velocity curve smoothness, and the asymmetric damping MR-suspension design can ideally improve the road holding and ride performances of vehicle motion. The proposed algorithm can be generally incorporated with a controller synthesis to realize an intelligent vehicle suspension design with the symmetric MR dampers.展开更多
基金the Ministry of Education of China(No.NCET-04-0725 and PCSIRT)
文摘A theoretical model based on BCT lattice structure was developed. Resultant force in the BCT lattice structure was deduced, following the interaction force of two kinds of magnetic particles. According to empirical FroHlich-Kermelly law, the relationship between the magnetic induction and the magnetic field was discussed, and a predictive formula of shear stresses of the BCT lattice structure model was established for the case of small shear deformation. Compared with the experimental data for different particle volume fractions, the theoretical results of the shear stress indicate the effects of the saturation magnetization and the external magnetic field on the shear stress.
文摘Magnetorheological (MR) fluids are now well established as one of the leading materials for use in controllable structures and systems. Commercial application of MR fluids in various fields, particularly in the vibration control, has grown rapidly over the past few years. In this paper, properties of magnetorheological (MR) fluids ,its applications in suspensions of vehicles, suspension of trains, high buildings cable-stayed bridges have been discussed. The scope of MR fluids in future, problems and some suggestions are also presented. Finally, effectiveness of MR fluids in vibration control of marine diesel engine through experiment is briefly discussed by the author.
文摘Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40’s). The special applications of these materials as a means of noise suppression are not yet investigated. Constrained Layer Damping (CLD) sheets can be realized by incorporating EMR (ER/MR) materials. In this way, a multilayered damping sheet is obtained with adaptive (tunable) stiffness and damping characteristics. These properties are easily changed in proportion to the electric (magnetic) field applied upon the EMR layer. This notion has been introduced for semi-active vibration control problems. Herein, such panels incorporating EMR material are proposed for adaptive acoustic treatments. Modeling (simulation) of a 3-layered panel with the middle layer being EMR with adjustable properties is carried out in this paper. The tunability of transmission/absorption characteristics of these composite sheets enables us making smart panels for adaptive noise and acoustic treatments. An adaptive performance can be achieved via changing the properties of such panels, on line, according to some sensor outputs. The main objective is to develop proper models to predict the Transmission Loss (TL) of such panels. Also, the TL of this panel is compared with the middle layer of a Newtonian fluid.
文摘Magnetorheological (MR) fluids consist of stable suspensions of magnetic particles in a carrying fluid such as water or silicone oils. The magnetorheological response of MR fluids results from the polarization induced in suspended particles by application of an external magnetic field. The interaction between the induced dipoles causes the particles to form columnar structure, parallel to the applied field. These chain-like structures restrict the motion of fluids, thereby increasing the viscosity and yield stress of the MR fluids. These mechanical characteristics allow for the construction of magnetically controlled device such as the MR fluids rotary brakes. However, there has been little information published about the design of MR fluid brakes. In this paper the design of the cylindrical MR fluid brake is investigated theoretically. Bingham model is used to characterize the constitutive behaviors of the MR fluids subject to an external magnetic field. The operational principle of the cylindrical MR fluid brake is presented. The theoretical method is developed to analyze the transmission properties of the torque of the cylindrical MR fluid brake. An engineering expression for the torque is derived to provide the theoretical foundations in the design of the cylindrical MR fluid brake. Based on this equation the volume and thickness of the annular MR fluids within the brake is expressed as functions of the desired ratio of torques with saturated magnetic field and without external field, the controlled mechanical power and the MR fluid material properties. The parameters of the thickness and width of the fluid in the brake can be calculated from the obtained equations when the required mechanical power level, the desired torque ratio are specified.
文摘目的:运用 MRI cine PC定量研究交通性脑积水脑室分流前后的脑脊液流动情况。材料和方法:在1.5T GEHorizon Signa磁共振机器上利用MRI cine PC程序,在以前实验所得的液体流速与信号强度关系公式的基础上,对16例交通性脑积水的中脑导水管、枕大孔和C2水平脑脊液流速、流量情况进行MRI cine PC检查(1.5TGE Horizon Signa),并对其中10例交通性脑积水脑室引流后的中脑导水管和枕大孔处脑脊液的流速和流量同样进行测量,并与术前进行比较。同时作为对照,对31例正常志愿者颅内中脑导水管、枕大孔和C2水平的脑脊液流速和流量进行测定。结果:交通性脑积水中脑导水管水平脑脊液流速和流量明显增快,与正常者进行统计有明显差异(P<0.05),向下峰速和向上峰速分别为47.57±16.71mm/s和44.48±19.22mm/s,向下流量及向上流量明显增大为3.142±1.055ml/s及3.143±1.055ml/s;脑脊液净流量为0±0.003ml/s。而枕大孔向下峰速和向上峰速分别为1.37±0.44mm/s和1.33±0.41mm/s,向下流量及向上流量分别为0.351±0.125ml/s及0.350±0.12lml/s;脑脊液净流量为0.001±0.007ml/s。C2水平脑脊液向下峰速和向上峰速分别为2.41±1.27mm/s和2.95±1.15mm/s,向下流量及向上流量分别为0.521±0.214ml/s和0.519±0.214ml/s;
基金Supported by Basic Science Research Program of National Research Foundation of Korea,Ministry of Education,Science and Technology of the Korean(Grant No.NRF-2015R1D1A1A09060901)Ministry of Science,ICT and Future Planning,Korea,under Convergence Information Technology Research Center(Grant No.IITP-2015-H8601-15-1003) supervised by Institute for Information&Communications Technology PromotionAdvanced Technology Center R&D Program funded by the Ministry of Trade,Industry&Energy of Korea(Grant No.10048876)
文摘Magnetorheological (MR) fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic field, which is known as MR effect, resulting in variation of stiffness, shear modulus, damping and tribological characteristics of MR fluid. As MR effect depends on the density of particles in the fluid or the strength of a magnetic field, the experiments are conducted to evaluate the friction property under reciprocating motion by changing the types of MR fluid and the strength of a magnetic field. The material of aluminum, brass, and steel are chosen for specimen as they are the most common material in mechanical applications. The surfaces of specimen are also observed by optical microscope before and after experiments to compare the surfaces with test conditions. The comparing results show that the friction coefficient increases as the strength of a magnetic field increases in regardless of types of MR fluid or the material. Also the density of particle in MR fluid affects the friction characteristic. The results from this research can be used to improve the performance of mechanical applications using MR fluid.
基金Sponsored by the National Natural Science Foundation of China(Grant No.11372803)
文摘This paper presents a linear shear mod magneto-rheological(MR) damper which can be applied to vibration control system.The proposed MR damper featured by a small amount of MR fluid,absence of a gas chamber or diaphragm and piston with helix slotted.Because of the absence of a gas chamber or diaphragm,unnecessary damping force caused by gas compression is not generated.Magnitude and damping coefficient of damping force are two important indexes to evaluate performance of MR damper.The piston with helix slotted is developed based on mechanical analysis on rheological characteristics of MR damper,and the damping performance of MR damper with helix slotted piston is investigated through performance experiments and comparison with analytical simulation.The results indicate that helix slot may increase friction coefficient on surface of the piston,and improve the maximum damping force without reducing damping coefficient of the damper.The reflux of MR fluid may be increased by adjusting helix angle suitably,which avoids the settlement of MR fluid.
基金This project is supported by Senior Visiting Scholarship of Chinese Scholarship Council, China(No.20H05002) Provincial Naturial Science Foundation of Education Commission of Jiangsu, China(No.03KJB510072)Doctoral Scholarship of Concordia University, Canada.
文摘An asymmetric damping force generation algorithm is originally proposed to yield the asymmetric force-velocity characteristics for the symmetric magneto-rheological (MR) dampers. The command current is formulated in an asymmetric manner to excite the symmetric MR dampers by employing the “on-off” control law in response to the direction of velocity, and a smooth modulation function is developed without phase shift to suppress strong transients in the damping forces caused by the current-switching discontinuity. The effectiveness of the proposed algorithm is evaluated by analyzing the dynamic responses of a quarter-vehicle suspension system with a symmetric MR-damper by modulating the command current into the asymmetric manner. The simulation results show that the proposed algorithm could achieve a better compromise between the conflicting requirements of the asymmetric damping force ratio and the force-velocity curve smoothness, and the asymmetric damping MR-suspension design can ideally improve the road holding and ride performances of vehicle motion. The proposed algorithm can be generally incorporated with a controller synthesis to realize an intelligent vehicle suspension design with the symmetric MR dampers.