Izwan Ismail

Fluid–Particle Separation of Magnetorheological Fluid in Squeeze Mode

In squeeze mode, magnetorheological (MR) fluids exhibit a unique behaviour when compression load is applied. The MR fluids were assumed to experience fluid–particle separation phenomenon, where magnetic particles and carrier fluid were separated at some extent of compression. In this study, the establishment of this phenomenon has been carried out. A cyclic compression test was performed on hydrocarbon-based MR fluid, where a video camera was used to record the expelling fluid. Solidified samples of epoxy-based MR fluid were then prepared and the cured samples were sectioned, mounted and prepared for metallographic study. Images extracted from the recorded video have shown that there was a separation of carrier fluid during compression where a brighter colour of fluid was observed expelling from the testing region. Furthermore, analyses of the micrographs demonstrated the increment of the particle distribution along compression process. The separation process was responsible for the variability of particle volume fraction in order to achieve desirable stresses.

Compressive and tensile stresses of magnetorheological fluids in squeeze mode

Magnetorheological (MR) fluid exhibits a perceptible change of rheological properties in reaction to external magnetic field. The MR fluids are currently enjoying renewed interest within the technical community in terms of the fundamental and applied research. MR fluids behaviour in squeeze mode is one of the areas that remain unknown as compared to valve and shear modes. Therefore, this paper presents stress-strain relationships of MR fluids under compression and tension tests. The results demonstrated that MR fluid corresponded to the changes in compressive and tensile stresses due to the changes in magnetic field strength. The compressive stresses were found to be much higher than the tensile stresses for the same experimental parameters. The behaviour of the MR fluids were dependent on the types of the carrier fluid and magnetic field strength. Furthermore, combinations of the stress-strain curves under quasi-static compression and tension modes were matched with the curves under dynamic loading.

Magnetic Circuit Simulation for Magnetorheological (MR) Fluids Testing Rig in Squeeze Mode

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.

An Experimental Investigation of Magnetorheological (MR) Fluids under Quasi-Static Loadings

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.

Fluid-Particle Separation of Magnetorheological (MR) Fluid in MR Machining Application

The presented work is an investigation of fluid-particle separation phenomena and compression stress resistance performance of magnetorheological (MR) fluids under squeeze mode. The squeeze mode is very significant to MR machining application. Material used in this study was silicone oil based MR fluid with 20% volume fraction of carbonyl iron particle. Compression test was performed by integrating the developed squeeze mode testing rig with a 50 kN Universal Testing Machine (UTM). The tests were conducted at constant speed and current. Each test was conducted at an initial gap of 2 mm and was stopped at a final gap of 0.5 mm. Force-displacement data was recorded and was analysed using TestExpert® II software. Full factorials with 27 experiments were designed using Design Expert 7 software. Three factors investigated in the design of experiments were carrier fluid viscosity, supplied current, and compression speed. Responses measured were strain energy and compression stress at maximum strain. Macro images of the phenomenon were recorded and evaluated qualitatively. From the compression stress-strain results, carrier fluid viscosity was significant to vary the MR fluid properties. The observed phenomenon shows that fluid-particle separation occurred in the low viscosity carrier fluid, low compression speed and high applied current. The parameters effect on strain energy and compression stress suggests that the fluid-particle separation is significant to the squeeze mode MR fluid performance. The relationship between stress resistance performance and fluid-particle separation phenomena were significant in designing innovative MR fluid devices.

Microstructural analysis of hot press formed 22MnB5 steel

This paper presents a microstructural study on hot press formed 22MnB5 steel for enhanced mechanical properties. Hot press forming process consists of simultaneous forming and quenching of heated blank. The 22MnB5 steel was processed at three different parameter settings: quenching time, water temperature and water flow rate. 22MnB5 was processed using 33 full factorial design of experiment (DOE). The full factorial DOE was designed using three factors of quenching time, water temperature and water flow rate at three levels. The factors level were quenching time range of 5 - 11 s, water temperature; 5 - 27°C and water flow rate; 20 - 40 L/min. The as-received and hot press forming processed steel was characterised for metallographic study and martensitic structure area percentage using JEOL Field Emission Scanning Electron Microscopic (FESEM). From the experimental finding, the hot press formed 22MnB5 steel consisted of 50 to 84% martensitic structure area. The minimum quenching time of 8 seconds was required to obtain formed sample with high percentage of martensite. These findings contribute to initial design of processing parameters in hot press forming of 22MnB5 steel blanks for automotive component.

Effects of Nano Copper Additive on Thermal Conductivity of Magnetorheological Fluid at Different Environment Temperature

Low thermal conductivity of magnetorheological (MR) fluid limits its potential to be applied in high temperature environment. Recently, enhancing thermal conductivity of similar fluids through addition of nanocopper has attracted to address the problem. This paper presents the effects of nanocopper addition on thermal conductivity properties of MR fluid at different environment temperatures. The nanocopper added MR fluid samples were synthesized with carbonyl iron powder in hydraulic oil. The samples were then stabilized with addition of fumed silica and were homogenized using ultrasonic bath. Thermal conductivity of the samples and references material was measured using thermal property analyser. The environment temperature of the samples was controlled by waterbath incubation method. The results showed that enhancement of thermal conductivity with the presence of copper nanoparticles was higher at 40 vol% of CIP compared to 20 vol% of CIP and a slight variation in thermal conductivity of MR fluid was observed in environment temperatures of 30–70°C. This finding leads to development of new class of magnetorheological fluid with enhanced thermal properties.

Effect of Sintering Temperature on Functionally Graded Nickel/Alumina Plate

Functionally graded material that consists of gradually changed dual-phase compositions along the thickness direction of its structure has been introduced as an answer to sharp interfaces problems occur while the processing. In order to observe the morphological and shrinkage due to the sintering process, the Ni/Al2O3 FG samples were manufactured via powder metallurgy routes under argon atmosphere. This study reveals that the sintering temperature does affects the sintering behaviors including the microstructures and radial dimensions of the FG plates. The numerical simulation is found to be useful to predict the stress concentration area within the structures and consequently improve the design of the FG plates.

Full Factorial Design to Study Material Parameters of Magnetorheological Fluid

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.

Investigation of mechanical performance of squeezed magnetorheological fluid using response surface method

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.