Papers by Author: Mohammed Rafiq Abdul Kadir

Abstract: Linear elastic response of the bovine cortical bone has been examined under compression load. Experimental and computational methods were used to observe and predict the response of cortical bone. In computational method, two mechanical behaviors of isotropic and orthotropic were considered to simulate the cortical bone deformation. In experimental process, the specimens were designed to show maximum stiffness and strength by specifying osteon direction along loading axis during tests. The tests were controlled by displacement rate of 0.5 mm/minute and the overall stiffness responses of the structures were recorded to extract mechanical properties and also for validation aims. Finite Element Method (FEM) was used to model the linear response of the structure by using ABAQUS6.9EF. The FE results using orthotropic definition shows a good correlation with experimental data. A discussion was given based on overall stiffness and effective stress variation for both mechanical behaviors. In order to design the optimal implant structure, the presented study was proposed for prediction of bone structure deformation that attached to the orthopedic implants.

Abstract: Understanding of racket parameters is important for players to gain the best racket which could improve their games performances. This present study was aimed to investigate the effect of string tension toward performance of coefficient of restitution (COR) by neglecting the effect of racket frame stiffness. A finite element simulation of collision between ball and string-bed was performed in Abaqus explicit. The ball was dropped onto the centre of mass (CM) of the string-bed area with different values of string tension. From the results, the increasing values of string tension lead to increase values of COR. This finding will contribute to the enlargement of sweet spot in badminton racket as well as improving the player performances.

Abstract: Fixation with cannulated screw was widely accepted for management of femoral neck fracture. However, the angle of placement cannulated screw for management of femoral neck fracture still controversial. The present study aims to investigate the mechanical behavior of the cannulated screws with two different angles of placements which are 135^o and 150^o in inverted triangular configuration for management of femoral neck fracture via finite element method. Therefore, the 3D model of a proximal femur consist of femoral neck fracture was constructed from CT data images using medical image processing software. The von Mises stress distributions on the cannulated screws were compared between each screw angle placement. The result showed that the cannulated screws in inverted triangle with 135^o of placement angle have better stress distributions than 150^o placement angle.

Abstract: The use of ankle external fixator to treat pilon fracture Type III is popular amongst surgeons as it can reduce complications such as non-union and mal-union. Even though configurations of the connecting bars are important, the material also plays a major factor for a successful outcome. In this paper, the Delta external fixator with simulated ankle pilon fractures Type III were modelled and analysed under two different materials; titanium alloy and stainless steel. The finite element model includes tibia, fibula, talus, calcaneus, cuboid, navicular, three cuneiforms and five metatarsals bone. To simulate the pilon fractures Type III, a cutting segment was utilised. The ligaments were assigned with linear spring properties and cartilages were modelled using Mooney-Rivlin hyper-elastic behaviour. The Delta external fixator was designed using a three-dimensional software with two different material properties - titanium alloy and stainless steel. High von Mises stress concentrated at the pin-bone interface with the highest value observed for the titanium fixation. The results also showed less deformation for the stainless steel compared to titanium.

Abstract: Electrical Discharge Machining is a controlled process where pulsed electrical discharge is used to erode metal in a workpiece. A number of EDM power supplies utilizing different topologies have been widely developed for various applications. Nowadays, EDM process has been given a significant amount of research focus in manufacturing micro components with new low power topologies being utilized. Recently, a demand in micro machining has also extended into biomedical applications. In this paper a current mode flyback converter is implemented for micro machining biomedical component. A MATLAB/SIMULINK modeling technique of flyback converter is presented and the effectiveness of the flyback converter topology is evaluated through the simulation results obtained by varying the value of primary inductance

Abstract: Wear on Co-Cr-Mo biomedical implants is still a major issue especially for applications in articulation joints like in total ankle, knee and hip arthroplasty. Generation of excessive wear particles can coagulate in body tissues which later cause inflammation, bone loss and necrosis. Modification of implant surfaces is a common technique for increasing the hardness and thus minimizing these effects. In this study, thermal oxidation method was carried out on the Co-Cr-Mo to investigate the effects of different pretreatment processes and surface roughness on the hardness of oxide layer formed. Prior to oxidation process, all samples were annealed and pickled to remove residual stress and oxide scales respectively. The oxidation process was done inside furnace under atmospheric condition for 3 hours at 1160 °C. The metallic compositions, surface morphology and hardness of the oxide layer formed on the substrate were verified using X-ray diffraction (XRD), scanning electron microscope and micro-Vickers hardness analysis respectively. It is found that mechanical pretreatment provides oxide/carbide layer with higher hardness than chemical pretreatment method. It is believed that remnants of polishing diamond pastes trapped in roughness valleys react with metal matrix and later transform into carbides during oxidation process. In contrast, initial surface roughness of the substrate has no significant effect on the hardness of oxide/carbide layer.

Abstract: Wear debris and metal ion release generated during application of biomedical devices would cause adverse cellular response, inflammation and pain in the human body. Modifying of implant surface with rutile structure is one of the methods to reduce these problems. In the present study, an attempt was made to evaluate the effect of thermal oxidation temperature on surface morphology and structure of the Ti13Nb13Zr biomedical material. The substrates were heated at varied temperatures of 550°C, 700°C and 850°C for 9 hours and cooled inside muffle furnace at a constant rate of 5oC/min. Scanning electron microscopy and x-ray diffractive were employed to evaluate the surface morphology and analyze the structure of the oxidized substrates respectively. All thermally oxidized samples exhibit the presence of oxides without spallation regardless of the thermal oxidation temperatures. Surface morphology of oxidized substrates changes from smooth to nodular particles-like shape when the oxidation temperature increases from low to high. Rutile structure dominants the surface area when the substrate is thermally oxidized at 850 °C.

Abstract: The objective of this study was to prepare a basic contributed model in beam to examine this novel composition supposed to apply for acetabular cup. Injection molding process used to manufacture of the component whereas ultrasonic welding was utilized to joint two components. Molding and welding value parameters were carried out by trial and error process. Strength bonding of two components was evaluated by single cantilever beam (SCB) test. The Interfacial fracture energy attained by single cantilever beam (SCB) test was exceeded over 1800 after 70 mm crack propagation.

Abstract: In this study, blends of ultra high molecular weight polyethylene/high density polyethylene/polyethylene glycol (UHMWPE/HDPE/PEG) and the composites containing Hydroxyapatite (HA) as reinforcement filler were prepared via single screw extruder nanomixer followed by compression moulding. PEG (2phr) was used as processing aid and HA loadings were varied from 10 to 50 phr. HDPE and PEG were introduced to improve the extrudability of UHMWPE. Rheological behavior was studied via capillary rheometer while flexural and izod impact tests were conducted in order to investigate the mechanical properties of the blends and composites. Melt viscosity of the blends was found to decrease with increasing shear rate indicating a pseudoplastic behaviour. Incorporation of PEG shows a synergism effect on the reduction of blends viscosity. Blend of 40% UHMWPE/ 60% HDPE/ 2 phr PEG was chosen as the optimum blend composition with a balance properties in terms of the mechanical properties and processability. The incorporation of HA fillers from 10 to 50 phr into the blend resulted in the increase of flexural modulus and flexural strength with a slight decline of impact strength values. It can be concluded that the composites having adequate strength and modulus within the range of cancellous bone properties were succesfully developed to be used as biomedical implant devices.

Abstract: The biomaterial composites consisting of a polymer with a matrix addition of particulate bioactive phase that analogous to the bone microstructure had been extensively studied as a substitute for human’s hard and soft tissues. In this work, HA reinforced HDPE composite (HDPE/HA) was made, with HA contents being up to 50 phr using single screw extruder nanomixer for the compounding process, and later followed by the injection moulding. These characteristics of the HDPE/HA composites were examined using various techniques including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile testing. Mechanical and thermal properties of the composite are differed when the amount of HA incorporated into the composite were varied. It is shown that HA particles were well dispersed and homogeneously distributed within the HDPE matrix. The elastic modulus and tensile strength were increased when the HA volume percentage increased from 10 phr to 50 phr with corresponding decreases in elongation at break. However no significant influence on thermal stability was found with increasing HA loadings. The enhancement of bioactivity has been proved while incorporation of HA into HDPE composite. SEM-EDX image showed the bulk formation of apatite layers on the composite surface with 30 wt% HA after 7 days immersed in simulated body fluid (SBF) solution. These results suggest the great potential of the composites for a range of temporary application in which bone bonding ability is a desired property.