Faris Tarlochan

Mechanical and physical behavior of newly developed functionally graded materials and composites of stainless steel 316L with calcium silicate and hydroxyapatite

This study aimed to investigate the structural, physical and mechanical behavior of composites and functionally graded materials (FGMs) made of stainless steel (SS-316L)/hydroxyapatite (HA) and SS-316L/calcium silicate (CS) employing powder metallurgical solid state sintering. The structural analysis using X-ray diffraction showed that the sintering at high temperature led to the reaction between compounds of the SS-316L and HA, while SS-316L and CS remained intact during the sintering process in composites of SS-316L/CS. A dimensional expansion was found in the composites made of 40 and 50 wt% HA. The minimum shrinkage was emerged in 50 wt% CS composite, while the maximum shrinkage was revealed in samples with pure SS-316L, HA and CS. Compressive mechanical properties of SS-316L/HA decreased sharply with increasing of HA content up to 20 wt% and gradually with CS content up to 50 wt% for SS-316L/CS composites. The mechanical properties of the FGM of SS-316L/HA dropped with increase in temperature, while it was improved for the FGM of SS-316L/CS with temperature enhancement. It has been found that the FGMs emerged a better compressive mechanical properties compared to both the composite systems. Therefore, the SS-316L/CS composites and their FGMs have superior compressive mechanical properties to the SS-316L/HA composites and their FGMs and also the newly developed FGMs of SS-316L/CS with improved mechanical and enhanced gradation in physical and structural properties can potentially be utilized in the components with load-bearing application.

Effect of geometrical parameters on the performance of longitudinal functionally graded femoral prostheses.

This study aimed to assess the performance of different longitudinal functionally graded femoral prostheses. This study was also designed to develop an appropriate prosthetic geometric design for longitudinal functionally graded materials. Three-dimensional models of the femur and prostheses were developed and analyzed. The elastic modulus of these prostheses in the sagittal plane was adjusted along a gradient direction from the distal end to the proximal end. Furthermore, these prostheses were composed of titanium alloy and hydroxyapatite. Results revealed that strain energy, interface stress, and developed stress in the femoral prosthesis and the bone were influenced by prosthetic geometry and gradient index. In all of the prostheses with different geometries, strain energy increased as gradient index increased. Interface stress and developed stress decreased. The minimum principal stress and the maximum principal stress of the bone slightly increased as gradient index increased. Hence, the combination of the femoral prosthetic geometry and functionally graded materials can be employed to decrease stress shielding. Such a combination can also be utilized to achieve equilibrium in terms of the stress applied on the implanted femur constituents; thus, the lifespan of total hip replacement can be prolonged.

Comparison of various functionally graded femoral prostheses by finite element analysis

This study is focused on finite element analysis of a model comprising femur into which a femoral component of a total hip replacement was implanted. The considered prosthesis is fabricated from a functionally graded material (FGM) comprising a layer of a titanium alloy bonded to a layer of hydroxyapatite. The elastic modulus of the FGM was adjusted in the radial, longitudinal, and longitudinal-radial directions by altering the volume fraction gradient exponent. Four cases were studied, involving two different methods of anchoring the prosthesis to the spongy bone and two cases of applied loading. The results revealed that the FG prostheses provoked more SED to the bone. The FG prostheses carried less stress, while more stress was induced to the bone and cement. Meanwhile, less shear interface stress was stimulated to the prosthesis-bone interface in the noncemented FG prostheses. The cement-bone interface carried more stress compared to the prosthesis-cement interface. Stair climbing induced more harmful effects to the implanted femur components compared to the normal walking by causing more stress. Therefore, stress shielding, developed stresses, and interface stresses in the THR components could be adjusted through the controlling stiffness of the FG prosthesis by managing volume fraction gradient exponent.

Thalamic Visual Prosthesis

Glaucoma is a neurological disorder leading to blindness initially through the loss of retinal ganglion cells, followed by loss of neurons higher in the visual system. Some work has been undertaken to develop prostheses for glaucoma patients targeting tissues along the visual pathway, including the lateral geniculate nucleus (LGN) of the thalamus, but especially the visual cortex. This review makes the case for a visual prosthesis that targets the LGN. The compact nature and orderly structure of this nucleus make it a potentially better target to restore vision than the visual cortex. Existing research for the development of a thalamic visual prosthesis will be discussed along with the gaps that need to be addressed before such a technology could be applied clinically, as well as the challenge posed by the loss of LGN neurons as glaucoma progresses.

A Framework for Developing Innovative Problem-Solving and Creativity Skills for Engineering Undergraduates

Background and Purpose Problem-solving and creativity skills are a set of skills that are highly looked for in today’s engineers. Globalization and the rapid pace of technology growth, including awareness on sustainability, have created the needs for such skills. However, the traditional method of rote teaching does not facilitate these skills well, especially in the Middle East and North Africa (MENA) region. Hence, a framework is proposed that encompasses the content, delivery method, and assessment, in the hope of instilling these skills in engineering undergraduates. The framework is developed for the MENA region but is generic enough to be applicable to other regions.

New vehicle bumper design for pedestrian protection during Impact

This study discusses the influence of the active bumper design on the performance of the selected current bumper in terms of pedestrian protection by using finite element method. The legform impactor is used to test the bumper models created according to EEVC/WG regulations (European Enhanced Vehicle-Safety Committee). The simulation was performed using LS-DYNA. The lower leg injury risk was discussed based on the performance of the bumper. Results of the study show a significant improvement in the bumper performance to mitigate the impact injury of the pedestrians lower leg.

Surface Alloying in Silver-Cobalt through a Second Wave Solution Combustion Synthesis Technique

Herein, we report the synthesis of silver-cobalt nanopowders using three different modes of solution combustion synthesis, and we present the effects of the synthesis conditions on particle morphology. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectrophotometer (UV-vis), Transmission electron microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS) to understand the structural and elemental properties. When Co is synthesized over Ag in a second wave of combustion, peak shifts observed in XRD and XPS show a change in the cell parameters and prove the existence of a strong electronic interaction between Ag and Co. Better control of mixing and alloying through the second wave combustion synthesis mode (SWCS) was evident. The sequence of combustion affects the structure and composition of the material. SWCS reduces the amount of carbon content, as compared to single-stage combustion, and the combustion of carbon is followed by a rearrangement of atoms.

Numerical and Experimental Investigation on Corrugation Geometry for Metallic Tubes under Lateral Loading

Energy absorption devices are being used to protect structures from severe damages and reduce injury to occupants during accidents. The integrated characteristics of crash absorption devices can be classified as high energy absorption capacity, light-weight, and cost-effective. One of the thin-walled structures which has drawn the attention of scientists is corrugated tube structure. In this paper, the effect of corrugation geometry on the crushing parameters of an aluminum corrugated tube is investigated. In this regard, different elliptical corrugation shapes were deemed and the compression response was numerically evaluated under lateral quasi-static loading. Finally, the crashworthiness parameters were extracted and compared to determine the influence of corrugation shape on the crashworthy response. Our results showed that using vertical elliptical corrugation decrease the densification point. Moreover, there is a gradual enhancement of mean crushing load by moving from the horizontal elliptical corrugations to the vertical ones. Also, by modifying of corrugation shape, the stress variation pattern changes, significantly.

Synthesis of Highly Efficient Bifunctional Ag/Co3O4 Catalyst for Oxygen Reduction and Oxygen Evolution Reactions in Alkaline Medium

Ag/Co3O4 catalysts using three different modes of solution combustion synthesis were developed and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy to identify crystallite size, oxidation state, composition, and morphology. Cyclic voltammetry and linear sweep voltammetry measurements for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) confirm the bifunctionality of the electrocatalysts. The electrochemical evaluation indicates that a synergic effect between Ag and Co enhances the activity through the fast breaking of O–O bond in the molecular oxygen to enhance the reduction mechanism. The high content of cobalt (Co) in the catalyst Ag/Co3O4-12, synthesized by second wave combustion, improves the activity for ORR, and the reaction mechanism follows a 3.9 number of electron transfer in overall reaction. The kinetic and limiting current densities of Ag/Co3O4-12 are maximum when compared to those of other Ag/Co3O4 catalysts and are very close to commercial Pt/C. Moreover, the maximum current density of OER for Ag/Co3O4-12 makes it a promising candidate for various bifunctional electrocatalytic applications such as fuel cells and metal–air batteries.