The design of a MR damper, consisting of piston and cylinder arrangement, is presented in this paper. In this paper, a 2D axisymmetric model based on finite element method (FEM) concept has been developed on the ANSYS platform to analyze and examine the MR damper characteristics. Based on the FEM model, a prototype of the MR damper is fabricated and tested experimentally in the semi active vibration laboratory of the department. The comparison of both these model analyses indicates that the FEM based model is effectively portraying the experimental behavior of the MR damper in terms of its damping force. The results obtained in this paper will be helpful for the designers to create more efficient and reliable MR dampers and also to predict its damping force characteristics.
Nowadays, handling stability and ride comfort are considered very important features of an automotive driving. Semiactive vibration control systems in automobile suspension had received a great attention among the researchers community as the smart materials are being used in these devices. Further, these smart materials have the characteristics of rapid reversible response phenomenon at low power consumption. The smart materials have multiple properties (electrical, magnetic, mechanical, and thermal) and can also transform energy. These properties can be altered very easily using some external fields, for example, magnetic or electric, and so forth. Magnetorheological (MR) fluids are one of such smart material that exhibits drastic and reversible change in its rheological properties, for example, elasticity, plasticity, viscosity, and so forth, which mainly depend upon the intensity of the magnetic field [
Schematic representation of MR damper.
Finite element method (FEM) simulates a physical system or assembly’s behavior by dividing the geometry of the system into a large number of small elements of standard shapes, formulates system equations, applies boundary conditions in terms of loads and constraints, and then solves the modified system equations for the unknown field variables of the interest, for example, displacement, strain, stresses, temperature, magnetic flux density, and so forth. The ANSYS [
Study of the MR damper is a promising topic as it provides a controllable damping force just by varying the current in its electromagnetic coil. The current can be supplied by the battery of an automotive vehicle. A number of researchers have begun modeling and designing of these MR dampers from different aspects of design with the help of finite element method (FEM). This has resulted in different designs of MR dampers having different geometry, effective range, and working principles [ Create the physics environment. Build and mesh the model and assign physics attributes to each region within the model. Apply boundary conditions and loads, that is, excitation. Obtain the nodal solution. Review and post processing of the results.
Dimensions of prototype MR damper.
Sr. no. | Parameter | Dimensions |
---|---|---|
1 | Pole length ( |
23 |
2 | Distance between the poles ( |
22 |
3 | Radius of the piston ( |
23 |
4 | Piston rod radius ( |
06 |
5 | Radial distance from piston rod |
07 |
6 | Clearance between piston and |
01 |
7 | Thickness of the cylinder ( |
08 |
Magnetic circuit of MR damper.
The MR damper is an axisymmetric solid subjected to axisymmetric loading and thus a 2D FEM modeling is sufficient for this prototype (Figure
2D axisymmetric model of MR damper in the ANSYS.
Electrical coil cross-section.
The ANSYS software includes a variety of elements in its library and one can choose any one of these element to model the electromagnetic phenomena of the MR damper. From literature survey, it is decided to use PLANE13 element which is a 2D quadrilateral coupled-field-solid element containing four nodes. The PLANE13 element has 2D magnetic, thermal, electrical, and piezoelectric field capability with limited coupling between the fields. The element also has nonlinear magnetic capability for modeling of the
The element input data includes coordinates of the four nodes and magnetic and electrical properties of each element. The metric units are used and are specified through the EMUNIT command. The EMUNIT also determines the value of
The output solution of the software, which is associated with an element, will be in the following form: nodal degrees of freedom included in the overall nodal solution, additional element output, for example, electromagnetic components.
The element output directions are parallel to the element coordinate system. In the ANSYS software, one defines the magnetic flux density as
Figure
2D flux lines around the electromagnetic coil.
Elemental solution of the magnetic induction distribution: (a) 2D solution and (b) a spatial view.
Flux density shown around electromagnetic coil as vectors.
The ANSYS model provides the nodal solution at the clearance space of the MR damper due to its magnetic induction. In this analysis, current is varied from 0 to 0.7 A in a step of 0.1 A. The respective ANSYS result shows that magnetic flux density increases with the increase in the current applied to the MR damper. This phenomenon is shown quantitatively in Table
Magnetic flux density obtained from FEM model.
Current (A) | Magnetic flux density (Tesla) |
---|---|
0.1 | 0.053 |
0.2 | 0.106 |
0.3 | 0.158 |
0.4 | 0.211 |
0.5 | 0.264 |
0.6 | 0.317 |
0.7 | 0.370 |
Magnetic flux density versus current (ANSYS model).
The damping force of the MR damper is calculated for the FEM model using the magnetic flux densities generated by the ANSYS. For this purpose, the relationship is developed between the shear stress (
According to the Bingham plastic model [
The researchers [
Damping force at various current levels for FEM model and experimental damping force.
Current (A) | Damping force— |
Damping force— |
---|---|---|
0.10 | 206.38 | 224.40 |
0.20 | 303.20 | 327.66 |
0.30 | 371.95 | 394.36 |
0.40 | 418.33 | 436.77 |
0.50 | 448.02 | 463.14 |
0.60 | 466.67 | 481.73 |
0.70 | 480.06 | 504.65 |
Based on the dimensions as selected in Table
(a) Components of the prototype MR damper, (b) assembly of piston and piston rod, (c) assembled piston and its rod with copper winding covered with cloth, and (d) assembly of MR damper.
Experimental setup for the testing of MR damper (mounted).
The schematic diagram of the experimental setup.
The laboratory consists of an electrodynamic vibration (EDV) shaker having a rated sine force of 2000 N with a frequency range of 1 to 3500 Hz. The rated peak to peak amplitude of the EDV shaker is 20 mm. The amplitude of the vibration is set at a desired value by varying the gain of the vibration test system. The EDV shaker can be operated manually or by PC based control mode. The shaker can also be used either for horizontal or vertical vibrational analysis. The shaker is controlled by PC based digital vibration controller cum analyzer having built-in signal conditioner unit. The shaker setup has a compatible PC based data acquisition and instrumentation system which gives the data in the form of force, velocity, displacement, and acceleration in real time manner. The system also includes a mechanical loading frame on which the damper is mounted vertically. The initial position of the piston in the cylinder of the MR damper is controlled either manually or by PC based control system. The piston is positioned near the bottom end of the cylinder of the MR damper during its experimental performance analysis. The test is performed for number of cycles at a fixed frequency of 1 Hz having the same gain which is set by vibration test system. The test is repeated under the same condition but at different current values supplied to the electromagnetic coil of the MR damper. The current is monitored and supplied through wonder box kit supplied by LORD Corp., Inc., USA [
Comparison of damping force of the both models.
The MR fluids are the most commonly used fluids in MR dampers to achieve variable damping coefficient. In this paper, FEM modeling has been carried out on ANSYS platform for the fabricated MR damper. The total damping force has been determined using the magnetic flux density values obtained from the ANSYS analysis. Then, experimental damping force is obtained by performing the tests on the prototype MR damper in the laboratory at different input current. On comparison of these two modeling results, it is observed that the total damping forces of both models are giving nearly the same values over a wide range of input currents. It is observed from the various graphical results that the total maximum damping force experienced by the damper is around 500 N which occurs at 0.7 A. It is concluded from this work that the FEM model effectively portrays the experimental behavior of a MR damper. The analysis adopted in this paper is adequate enough for the control and design of a MR damper. The results obtained in this paper will help the designers to create more efficient and reliable MR dampers and also to predict the damping force within the permissible error of engineering analysis.
Effective cross-sectional area of piston
Magnetic flux density
Diameter of the piston
Damping force
Friction force component
Viscous force components
Induced yield stress
Total damping force
Radial distance from piston rod to coil width
Current
Pole length
Volumetric flow rate
Radius of the piston
Diameter of the piston rod
Clearance between piston and cylinder
Distance between the poles
Piston rod radius
Thickness of the cylinder
Mean circumference of the damper’s annular flow path
Viscosity
Absolute permeability of the vacuum
Relative permeability
Shear yield stress
Piston velocity.
The authors declare that there is no conflict of interests regarding the publication of this paper.