Microstructure and Mechanical Properties of Ti-6Al-4V Produced by Selective Laser Sintering of Pre-alloyed Powders

The purpose of this research is to investigate the microstructure and mechanical properties of Ti6Al4V pre-alloyed powders producing by direct metal laser sintering technique. Through this research, the direct fabrication of Ti6Al4V metal parts by selective laser sintering machine has been carried out using EOS GmbH M270 equipment. Employing intricate thermo-mechanical interaction between the laser beam and the metallic powders, the machine consolidates predefined cross sections and binds the particles together to form solid parts which correspond to CAD data.The geometrical feasibility of the parts, including process accuracy were statistically analysed by simple benchmark studies. The intricate correlation between powder materials and process parameters were thoroughly investigated via fractography, metallography and standard physical testing.It was found that, SLS technologies are capable of directly producing near to full density metal parts with good mechanical properties.Ti6Al4V produced by laser sintering has very fine α+ microstructure. This fine and stable microstructure demonstrated a high yield stress and UTS with low elongation at break. The fracture surface has a dimple features typical of a ductile structure. Dimensional analyses were performed on the customised benchmark showing process accuracy below 50 m. Designated heat treatments modified the microstructure which influences the mechanical behaviour of the parts

Direct Metal Laser Sintering of Titanium implant with Tailored structure and Mechanical Properties

Direct Metal Laser Sintering has attracted much attention over the last decade for producing complex parts additively based on digital models. The capability and reliability of this process has stimulated new design concepts and has widened the manufacturing perspective of product customisation. This research work is designed to gain a deep understanding of laser sintering processing parameters, the corresponding microstructures and the mechanical properties. The main purpose is to have a body of fundamental knowledge about the laser and titanium powder material interactions, thus establishing the factors that influence the process-structure-properties relationships of the Direct Metal Laser Sintering process. Finally, a route for manufacturing customised craniofacial implants was described. This is to evaluate the DMLS processing capabilities in medical areas, particularly those parts having porous and lattice design structures. The interaction between a laser beam and the powder bed creates a distinctive structure; a ball shaped (blob) consists of solid and porous regions. All the blobs have the same shape and morphology which may well suggest that there is a tendency for the powder particles to form a spherical droplet prior to a movingless laser beam. Surrounding the melted core is a sintered region of partially melted powder particles where the powder particles were fused together to form inter-particle necks. There is a linear relation between size, weight and density of a blob and the laser power. The surface temperature obtained exceeds the melting and vaporization temperature of the titanium and this creates a hole on the top part of a blob as a result of a massive temperature rise. Laser power of 140W gives a consistent structure and hardness in a blob. Metallographic analyses of a blob’s cross-section show an α+β structure with prior-beta grains. The morphology of the lamellar structure consisted of acicular needles with a basket-weave pattern. The pores were characterised as having flat and spherical features with the size ranging from 2µm to 6µm. The micro-porosity observed may be associated with shrinkage which occurs during solidification or with the presence of entrapped gases from the atmosphere or argon gas from the shrouding environment Laser power and scan speed are the two most crucial factor controlling the laser-powder interactions. Result shows that laser power is capable of widening the processing parameters particularly the scan speed. Increased laser power causes more powder to melt thus creating a bigger melt pool. Contrary to this, increasing the scan speed reduces the interaction time thus a smaller amount of powder melts. The right combination of these two parameters results in inducing an appropriate exposure time where continuously scanned tracks can be formed. Most of the parts were successfully built using a specific volume energy density of 50Jmm⁻³, which was considered to be the optimum processing parameter for this research work. The ideal laser-material interaction time was calculated at 0.0008secs. The microstructural analysis revealed a fully lamellar structure with acicular morphology. XRD analysis confirmed the presence of α’ martensite, which explains the thermal history of a high isothermal condition and rapid cooling. The cross section of a solid part exhibited an acicular, needle-like structure with a herring bone pattern, parallel to building direction, due to directional solidification. The microstructure had a high tensile strength but with low ductility. It is also worth mentioning that a slight change in scan speed, with the intention of providing more energy density to the powder, may cause instability in the melt pool and cause deterioration in the mechanical properties. It is therefore confirmed that there is an upper limit and allowable processing window where a good balance of tensile strength and hardness in a DMLS part is achievable. A framework prior to an implant’s fabrication was established and the associated design and manufacturing software are reported. The processing route required software like MIMICS and MAGICS to manipulate the medical images and design data and equitable skills must be acquired to handle the machine in order to successfully fabricate the desired parts. Employing MAGICS new lattice function proved to be more efficient, saving time compared to a manual procedure, especially when dealing with large medical data manipulation. In conclusion, the proposed method from this study is capable of producing a customised part with the highest degree of design complexity compared with other conventional manufacturing methods. This has proved to be very suitable for manufacturing titanium medical implants, particularly craniofacial implants which require a customised and lightweight structure and at the same time still provide good mechanical propertie

Pricing warrant by using binomial model: comparison between historical and implied volatility / Khairu Azlan Abd Aziz… [et al.]

A warrant is a security that allows the holder to buy and sell the underlying share at a fixed price until expiry date. Warrant price will always fluctuates since the underlying share also fluctuates. Hence, determining the warrant price is the main problem among the investors in Malaysia. This research is focusing on pricing the warrant for five companies that were listed in Bursa Malaysia. The companies were chosen randomly from UiTM DataStream. The selected companies were Boon Koon Sdn Bhd, Hovid Bhd, Kelington Bhd, ML Global Bhd and Tropicana Corporation Bhd. The data contained underlying share, interest rate, exercise price and actual warrant price. This research aims to define the price of warrant by using Binomial model. Historical volatility and implied volatility were used in this research whereby volatility is the movement of the underlying share price. This research aims at comparing the actual warrant price with the calculated warrant price. The data were computed manually by using Microsoft Excel and the comparison was made between the two type of volatilities to give the nearest value of calculated warrant price to the actual warrant price. The nearest value was assumed the best value for this research. The result was made by analyzing the line graphs and comparing between historical volatility and implied volatility with actual warrant price. Mean Square Error was used to support the results that were obtained from the line graphs. In the end, implied volatility yielded better results compared to historical volatility

A cross sectional 3D evaluation of the morphology of the hyoid bone

Hyoid bone which has no bony articulation serves as maintaining the . airway, swallowing and preventing regurgitation in our body. Hyoid bone is very much related to dentistry as the tongue and floor of the mouth are connected to it. Obiectives: In this study we aimed to determine the hyoid bone and epiglottis level in relation to cervical spine of subjects without craniofacial abnormality from different age groups

Fuzzy Logic to Evaluate Significant Factors Affecting Students’ Academic Performance Through Online Distance Learning

Online distance learning is becoming more and more popular and more preferred among students. In order to develop efficient strategies and solutions for introducing online distance learning, higher education institutions should be aware of the needs and expectations of their students. In the current study, students from University of Technology MARA will investigate which factors that affect the execution of online distance learning for academic performance. Time management, learning environment, internet connection, and learning method are among the factors under consideration, as determined by a literature review. The information was gathered through an online survey of 331 students whose academic performance is affected by online distance learning. An expert system based on fuzzy logic has been developed to determine which factors have the greatest influence on students' academic performance in online distance learning. According to the results obtained using the MATLAB software, one of the most important factors influencing students' academic performance in online distance learning is time management. The findings of this study will help students to improve time management in order to improve students’ academic performance

The Assessment of Quran Reciting Competitions Using the Fuzzy Evaluation Method

A Quran Reciting Competition evaluates a participant's performance based on several factors, including Tajweed, Tarannum, Fasohah, and Vocal Quality. Participants in the Quran Reciting Competition are usually assigned a point value of 100, with each point representing a linguistic word or label such as 'Exceptional' ,'Excellent',  'Fairly Good' and so on. Evaluating participant performance seems difficult because it involves human decision-making, which is imprecise, ambiguous, and unpredictable. This study employed the fuzzy evaluation method to assess participants' performance at a Quran Reciting Competition in Klang. In this manner, the membership function graph was used to determine the membership value of each satisfaction level. The satisfaction level of each participant's mark was then computed. At the end, the fuzzy markings with linguistic values would be obtained. The proposed method provides an alternative approach that is reasonable and intelligent in assessing competitors' performance. This method is practical because it can increase the satisfaction of participants and assist the panels in making more reliable decisions during the competition

Application of Fuzzy Analytic Hierarchy Process (FAHP) for the Selection of Best Student Award

The Best Student Award is an award that students, particularly those who perform best, look forward to receiving. It recognized students who have achieved success in both academic and extra-curricular activities during their undergraduate years. However, there are other challenges in the student selection decision such as having trouble in selecting the student with what characteristic features should be considered and prioritized. Hence, the management needs to take the initiative to make students more satisfied with the new process and result. This study aims to determine the important factors and sub-factors needed to select the student for the best student award and rank them according to the most important influence level. To achieve the objective, the Fuzzy Analytic Hierarchy Process (FAHP) has been used to determine ranking factors including Cumulative Grade Point Average (CGPA), soft skills that students possess, discipline, and participation in extra-curricular activities. Each factor comprises three sub-factors. The primary data was collected by distributing questionnaires to six experts, consisting of three (3) academic administrators and three (3) student administrators using Google Forms. Discipline, with a normalized weight of 0.363, is the most important factor in students' selection of excellent students. With a normalized weight of 0.485, the sub-factor teaching and learning process is the most essential for CGPA. With a normalized weight of 0.445, self-confidence is the most important sub-factor under soft skills. Subfactors free from disciplinary action (normalized weight 0.414) are significant for the factor of discipline and committing (normalized weight 0.482) is significant for the factor of extra-curricular activities. Based on this outcome, it shows that Fuzzy AHP is a method that can assist experts to decide under complicated situations and precisely rank all factors and sub-factors. High satisfaction among students with selection decisions will most likely lead to their high and extraordinary fighting spirit

Nasyid Competition Assessment Using Fuzzy Evaluation Method

The nasyid competition evaluates a participant's performance based on several factors, including Voice, Music, Lyrics, and Performance. Participants in the nasyid competition are usually assigned a point value of 100, with each point representing a linguistic word such as “Perfect”, “Spectacular”, “Very Good” and so on. Evaluating participant performance is especially difficult because it involves human decision-making, which is imprecise, ambiguous, and unpredictable. This study employs the fuzzy evaluation method to assess participant performance at a nasyid competition held in Kedah. In this manner, the membership function graph was used to determine the membership value of each satisfaction level. When fuzzy numbers are used, the fuzzy markings are created more consistently. The satisfaction level of each participant’s mark would then be computed. In the end, the fuzzy markings with linguistic value would be obtained. The proposed assessment method has a bright future in evaluating those participants’ performance because it provides an alternative approach to assessing performance

Selecting The Effective Ways to Prevent COVID-19 From Spreading Using Fuzzy AHP Method

The COVID-19 pandemic has had a significant impact on global health and economies. This study aims to identify highly effective prevention strategies for mitigating the spread of COVID-19 using the Fuzzy Analytic Hierarchy Process (FAHP) method. The FAHP is a fuzzy logic-based extension of the Analytic Hierarchy Process (AHP) technique, allowing for the consideration of both tangible and intangible criteria. The study focuses on seven key criteria: social/physical measures, health monitoring, avoidance of unnecessary contact, hygiene practices, immunity/fitness, healthy diet, and sharing personal items. By involving three decision-makers, including a nurse, a Medical Officer (MO), and a Medical Assistant (MA), the relative weights of these criteria are calculated using pair-wise comparisons and Buckley's approach. The findings reveal that hygiene emerges as the most critical factor in preventing the spread of COVID-19, followed by social/physical measures and health monitoring. The study provides valuable insights for policymakers and healthcare professionals in selecting and implementing effective preventive measures to control the spread of COVID-19

A cross sectional 3D evaluation of the morphology of the hyoid bone

Hyoid bones is a uniqe structure which lies between and thyroid cartilag