A COMPARATIVE STUDY OF PARAMETRIC MODELS OF MAGNETORHEOLOGICAL FLUID SUSPENSION DAMPERS
Magnetorheological dampers more commonly called, MR dampers, are being developed for a wide variety of applications where controllable damping is desired. MR damper is an intelligent damper, which is used as automobile suspension for vibration control. MR fluids represent a class of smart materials whose rheological properties change in response to the application of a magnetic field. MR fluid dampers are new type of vibration control elements, having the advantages of rapid damping and stiffness changing in the presence of an applied magnetic field. MR dampers have received a great deal of attention in the last two decades due to their being a potential technology to conduct semi-active control. It is therefore vitally important to understand the dynamic behavior of such devices whose nonlinear hysteresis is a rather complicated phenomenon. Models can accurately represent the behaviour of MR dampers are essential in understanding the operation and working principles of the device. Such models can eliminate a great deal of uncertainties during the design process, which can subsequently enable control strategies for the damper to be developed efficiently and reliably. In this paper, MR fluid structure, damper description and parametric models have been presented.
Harmonic analysis of a magnetorheological damper for vibration control
Semi-active control systems are becoming more popular because they offer both the reliability of passive systems and the versatility of active control systems without imposing heavy power demands. In particular, it has been found that magnetorheological (MR) fluids can be designed to be very effective vibration control actuators, which use MR fluids to produce controllable damping force. The objective of this paper is to study a single-degree-of-freedom (SDOF) isolation system with an MR fluid damper under harmonic excitations. A mathematical model of the MR fluid damper with experimental verification is adopted. The motion characteristics of the SDOF system with the MR damper are studied and compared with those of the system with a conventional viscous damper. The energy dissipated and equivalent damping coefficient of the MR damper in terms of input voltage, displacement amplitude and frequency are investigated. The relative displacement with respect to the base excitation is also quantified and compared with that of the conventional viscous damper through updating the equivalent damping coefficient with changing driving frequency. In addition, the transmissibility of the MR damper system with semi-active control is also discussed. The results of this study are valuable for understanding the characteristics of the MR damper to provide effective damping for the purpose of vibration isolation or suppression.
Repressive coping before and after diagnosis of breast cancer
Objective: The aim was to investigate to which extent emotional repression is a premorbid coping tendency of cancer patients and/or a coping response to the threat posed by a cancer diagnosis. The results of one previous study of breast cancer patients suggest the latter possibility, and our aim was to replicate and extend these findings.