Papers by Author: Abdul Ghani Olabi

Abstract: The only grouting material used for anchoring cemented arthroplasties to contiguous bones is PMMA (Polymethyl methacrylate) bone cement. In this study the flow of bone cement through porous cancellous bone is modelled to determine the degree of penetration in total hip replacement using FIDAP simulation software. Power law viscosity model is used with constant consistency index and power law index less than 1 for pseudoplastic behaviour of Simplex P® and Zimmer bone cement. The effect of bone cement amount has been investigated under four different prosthesis insertion velocity 5, 10, 15 and 20 mm/s. The result shows that the depth of penetration increases with decreasing bone cement amount. In the case of Zimmer bone cement more penetration through cancellous bone was observed than Simplex P® bone cement.

Abstract: PMMA (Polymethyl methacrylate) bone cement is currently the only material used for anchoring cemented arthroplasties to contiguous bones. The aim of this work is to model the flow of bone cement through porous cancellous bone to study the degree of penetration in total hip replacement using FIDAP simulation software. Two different viscosity models have been used (a) power law with constant consistency index and power law index less than 1 for pseudoplastic behaviour of Simplex P® and Zimmer bone cement; (b) FORTRAN subroutine for time dependent rheopectic behaviour of CMW3 and Zimmer bone cement. For each type of bone cement the effect of prosthesis insertion velocity have been investigated under four different values 5, 10, 15 and 20 mm/s. It has been observed that the depth of penetration increases with increasing prosthesis insertion velocity. On the other hand, the maximum pressure in bone cement decreases with increasing prosthesis insertion velocity. It has been observed that there is more penetration through cancellous bone for pseudoplastic behaviour than rheopectic behaviour of bone cement.

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 the last years many researchers were concentrating to develop and design new unconventional metal forming processes. Among such new technologies, tube hydroforming was proved as one of the most promising. Geometry of the tube and die were found to have significant effects on the hydroformed part. In this work, Response surface method was used based on data provided by Finite element modeling to construct a model for the bulge height as a function of geometrical factors for T-type bi-layered tube hydroforming. Interaction effects were analyzed and discussed.

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: Magnetostriction is the deformation that spontaneously occurs in ferromagnetic materials when an external magnetic field is applied. In applications broadly defined for actuation, magnetostrictive material Terfenol-D (Tb0.3Dy0.7Fe1.9) possesses intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency. These are some of the essential parameters required for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption compared with the traditional solenoid fuel injection system. A prototype CNG fuel injector assembly was designed which included magnetostrictive material Terfenol-D as the actuator material. A 2D cross-sectional geometry of the injector assembly, which incorporated both linear and non-linear magnetic properties of the corresponding materials, was modeled in ANSYS for 2D axisymmetric magnetic simulation. Subsequently, a 3D replica of the CNG flow conduit was modeled in GAMBIT with the resultant injector lift. The meshed conduit was then simulated in FLUENT using the 3D time independent segregated solver with the Standard k  , the Realizable k   and RSM turbulence models to predict the mass flow rate of CNG to be injected. Eventually, the simulated flow rate was verified against mathematically derived static flow rate required for a standard automotive fuel injector considering standard horsepower, BSFC and injector duty cycle.

Abstract: In applications broadly defined for actuation, magnetostrictive materials possess intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency, which are some of the essential parameters for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption. This paper investigates the application of Terfenol-D as a magnetostrictive actuator material for CNG fuel injection actuation. A prototype fuel injector assembly, including Terfenol-D as the core actuator material, was modeled in both Finite Element Method Magnetics (FEMM) and ANSYS Electromagnetics simulation softwares for 2D magnetics simulation. Preferably, FEMM was used in order to determine the coil-circuit parameters and the required flux density or applied magnetic field to achieve the desired magnetostrictive strain, consequently, the injector needle lift. The FEMM magnetic simulation was carried out with four different types of AWG coil wires and four different coil thicknesses of the entire injector assembly in order to evaluate the relationship between the different coil types and thicknesses against the achieved strain or injector lift. Eventually, the optimized parameters derived from FEMM were inserted into ANSYS Electromagnetics to compare the variation of results between these two simulation environments.

Abstract: In this paper, the behaviours of three types of MR fluids under quasi-static loadings in tension mode were investigated. One type of water-based and two types of hydrocarbon-based MR fluids were activated by a magnetic field generated by a coil using a constant value of DC electrical current. Experimental results in terms of stress-strain relationships showed that the MR fluids had distinct unique behaviours during the tension process. A high ratio of solid particles to carrier liquid in the MR fluid is an indication of high magnetic properties. The water-based MR fluid had a relatively large solid-to-liquid ratio. At a given applied current, a significant increase in tensile stress was obtained in this fluid type. On the other hand, the hydrocarbon-based MR fluids had relatively lower solid to liquid ratios, whereby, less increases in tensile stress were obtained. The behaviours of MR fluids were dependent on the relative movement between the solid magnetic particles and the carrier fluid. A complication occurs because, in the presence of a magnetic field, there will be a tendency of the carrier fluid to stick with the magnetic particle

Abstract: Establishing the relationship between process parameters and the magnitude of residual stresses is essential to determine the life of welded components. It is the aim of this paper to develop mathematical models to assess residual stresses in the heat-affected zone of dissimilar butt jointed welds of AISI304 and AISI1016. These models determine the effect of process parameters on maximum residual stress. Laser power, travel speed and focal position are the process input parameters. Plates of 3 mm thick of both materials were laser welded using a 1.5 kW CW CO2 Rofin laser as a welding source. Hole-drilling method was used to compute the maximum principal stress in and around the HAZ of both sides of the joint. The experiment was designed based on a three factors five levels full central composite design (CCD). Twenty different welding runs were performed in a random order, 6 of them were centre point replicates and the maximum residual stresses were calculated for each sample. Design-expert software was used to fit the experiential data to a second order polynomial. Sequential F test and other adequacy measures were used to check the model’s performance. The results show that the developed models explain the residual stress successfully. Using the developed models, the main and interaction effect of the process input variables on the residual stresses at either side of the weld were investigated. It is found that all the investigated laser parameters are affecting the performance of the residual stress significantly.