Papers by Keyword: Squeeze Mode

Abstract: The braking system is among the most significant active safety systems in a vehicle application for preventing injuries and property damage. Whether for light or heavy vehicles, brakes are no longer a small issue whereas it becomes a crucial problem to maintain the safety and to avoid the unpredictable cases especially on the road. Advanced technology in automotive industry has produced a new coming design of Magnetorheological (MR) brake which a field change is triggered off by changing the current in the coils exciting the magnetic field. MR fluid is one of the members of smart material which applicable usage to achieve the standard of rotary high speed similar as the existing brake disc in hydraulic system. A new MR brake disc was proposed using the squeeze mode rather than only conventional mode at the upper and lower rotating rotor. Parameters that have been considered are the types of MR fluid, selection of magnetic material, non-magnetic material and coil configurations. Then a finite elements analysis was performed to analyse the result of magnetic circuit and magnetic field strength within the MR brake configuration. MRF-140CG has been selected to represent the fluid to enhance the maximum magnetic flux density. The results showed that AISI 1020 and Stainless Steel 316 meet the requirement of material selection of magnetic and non-magnetic. Indirectly, yield stress has been significant increase when the magnetic field strength rises at certain value. Therefore, intention on design innovation of MR brake is useful to efficient control by upgrading function of those parameters which has been presented.

Abstract: This paper presents a magnetorheological (MR) brake design by using additional squeeze working mode to an existing conventional rotational shear. The MR brake was designed with consideration given to a new concept of braking mechanism with the help of magnetic simulation. Important parameters such as disc brake dimensions, clearance gap and electromagnetic coil configuration were taken into account when constructed the MR brake. Simulation results showed that the magnetic field strength was at best by having the magnetic coil beside the non-magnetic material, which was located at the end of the outer diameter. Meanwhile, the value of magnetic field was greater than when a small squeeze gap was applied. Eventually, the design will provide an opportunity to study and consequently understand on how the MR fluids react to such operating condition in order to be realized in the MR brake.

Abstract: This paper presents the effects of magnetorheological (MR) fluid parameters, bidisperse ratio, carrier fluid viscosity and particle volume fraction, on its mechanical behaviour using statistical investigation. Silicone oil-based MR fluid samples were compressed using universal testing machine (UTM) in a vertical direction. A set of eight experiments was designed by Design Expert 7 software in which was conducted at two levels for each factor. Stress-strain curves that obtained from the compression test were then analysed by testXpert analyser software. The responses in terms of maximum stresses at 0.75 of strain were extracted from the curves. The result indicated that a combination of high bidisperse ratio and particle volume fraction, and a low carrier fluid viscosity could produce a high compressive stress. The findings are important to be considered in designing squeeze mode MR fluid actuators.

Abstract: In this paper, effects of critical parameters, namely initial gap, squeezing speed and applied current were statistically investigated on the mechanical behaviour of MR fluid in squeeze mode. A set of 17 experiments was designed using Design Expert 7 software to gather data from response surface methodology (RSM). The responses in terms of compression modulus were then calculated. An MRF132-DG was used as a sample in each experiment. The experiments were conducted under compression stress mode using universal testing machine (UTM). Stress-strain curves were analysed using the machine integrated TestXpert analyser software package. The stress-strain curves of MR fluid under squeeze have produced a shear thickening behaviour at 13.54 MPa of the highest stress at 0.75 of strain. A correlation between the three parameters and the stress-strain properties was specified. The results showed that the initial gap and supplied current were significantly produced a high compression modulus for the MR materials. These findings are important to enhance the capability of the squeeze MR devices to operate at its best performance. High compressive stress is crucial for most magnetorheological (MR) materials, particularly in squeeze mode devices.

Abstract: In our earlier work, test equipment has been designed, simulated and fabricated to perform experiment on MR fluids in squeeze mode. Preliminary results were gathered and presented for the purpose of validating the test equipment. Therefore, in this paper, a further systematic investigation of MR fluids in squeeze mode has been carried out. As a result, MR fluids experienced rheological changes in three stages during compression and tension. Fluid-particles separation phenomenon was the main caused for the unique behaviour of MR fluids. Particle chains depended on the structure transformation in which the carrier fluid movement can be controlled by changing the magnetic field strength.

Abstract: Recent advances in the research of magnetorheological (MR) fluid based devices have indicated the opportunities for squeeze mode devices using the smart fluids. The mode seems suitable for small amplitude and high force applications. Therefore, it is of a research and engineering interest to explore the model of a controlled squeeze mode MR mount (damper). As such, in the paper the authors highlight the model of a squeeze mode hydraulic mount, then present the simulation results in the form of dynamic stiffness and damping vs. frequency plots, respectively.

Abstract: A Magneto-rheological(MR) fluid damper based on squeeze model is put forward. The squeeze flow differential equation is obtained. Navier slip condition is considered on two boundary surfaces and compatible condition is established. The radial velocity profile and the radial pressure distributions are derived respectively. The mathematical expression of damping force is devloped. In order to verify rationality of analytical method, MR fluid damper based on squeeze mode is designed and fabricated according to technical requirements of engine vibration isolation system. The experimental damping forces from MTS870 Electro-hydraulic Servo with sine wave excitation show that analytical method proposed in this paper is feasible and has the reference value to design MR fluid damper based on squeeze mode.

Abstract: In this study, a testing rig in squeeze was designed and developed with the ability to conduct various tests especially for quasi-static squeezing at different values of magnetic field strength. Finite Element Method Magnetics (FEMM) was utilized to simulate the magnetic field distribution and magnetic flux lines generation from electromagnetic coil to the testing rig. Tests were conducted with two types of MR fluid. MRF-132DG was used to obtain the behaviour of MR fluid, while synthesized epoxy-based MR fluid was used for investigating the magnetic field distribution with regards to particle chains arrangement. Simulation results of the rig design showed that the magnetic flux density was well distributed across the tested materials. Magnetic flux lines were aligned with force direction to perform squeeze tests. Preliminary experimental results showed that stress-strain pattern of MR fluids were in agreement with previous results. The epoxy-based MR samples produced excellent metallographic samples for carbonyl iron particles distributions and particle chain structures investigation.

Abstract: This paper presents experimental investigations of three MR fluid types under the influence of several factors in tension loading mode. One MR fluid was water-based, MRF-241ES, while the other two were both hydro-carbon based, MRF-132DG and MRF-122-2ED. The magnetic properties of the MR fluids varied significantly due to a higher particle density in the water-based MR fluid compared to the hydrocarbon-based MR fluids. Tension as a squeeze mode, is as an operational mode where two flat parallel surfaces, standing opposite to each other, are pulled apart from each other by an external force, acting along the path of the magnetic flux lines. The experiments were performed in a vertical direction in the environment of a DC magnetic field. Stress-strain curves of the MR fluids under tension showed similar characteristics despite the fact that different types of the carrier fluids were used. The results revealed that the magnitude of the stress, for a given strain value, depended on the applied current and the initial gap size. It was found that, for higher applied currents and smaller initial gap sizes, there were larger stress values. However, the tensile speed had no significant effect on the stress-strain curves of MR fluids.

Abstract: Meniscus dynamic behaviors, as well as its optimal waveform of driving signal, in a squeeze mode piezoelectric inkjet device are studied in this paper. To use the squeeze mode piezoelectric inkjet device as a drop-on-demand dispenser, the driving signal is trapezium waveform. The parameters in a trapezium waveform of the driving signal include rise time (trise), dwelling time (tdwell), fall time (tfall) and voltage (Vp). Among these parameters, the most important parameter of driving signal is the dwelling time. To demonstrate the importance of dwelling time, a LED signal synchronized with the driving signal is used to visualize the instantaneous meniscus shape under a microscope. Experimental results show the meniscus oscillation at beginning and droplet ejection at the later phase. It is found there is an optimal dwelling time. At the optimal dwelling time, droplet ejects in a minimum time and its ejection velocity reaches the maximum. The optimal dwelling time can be further identified it relates to a pressure wave oscillation within the device. The optimal dwelling time can be approximated as the length (L) of the piezoelectric inkjet device divide by the speed of sound (c) in the dispensed fluid.