Applied Mechanics and Materials Vols. 773-774

Abstract: Studies of contact problem have been widely executed by researchers with variable scopes, methods and definitions. A common problem occurs while handling contact phenomena is sliding through element boundary [1], due to the discontinuity of the local coordinate between elements and a contact point [2] [3]. The common problem that occurs at an element boundary is a stable convergence result is hard to achieve [4], thus inspires authors to make a comparison of two beam methods which are Euler-Bernoulli beam theory and Timoshenko beam theory for frictionless contact problem. Authors have been investigated geometrically non-linear analysis with extremely large displacements by using Tangent Stiffness Method (TSM) [5], a robust non-linear analysis method to execute analysis and produce results with high accuracy. In this study, authors propose the modification of the beam elements with three nodes by considering the adaptation of shear deformation by Timoshenko beam theory. The modification enables the contact point to slide through the element edge smoothly and some numerical examples are provided in this study.

Abstract: A three-dimensional finite element model of unidirectional fibre reinforced composites has been investigated numerically using periodic boundary condition method. This method was used to predict the elastic mechanical behaviour of a unit cell of such composites. Periodic boundary condition was used due to its capability to represent a single unit cell similar to the neighbouring unit cells with continuous physical elements. It is assumed that the paired nodes displaced continuously without separating or interrupting other nodes during the deformation step. From the study, it was revealed that the elastic modulus agreed well with the experimental results, indicating that the present model could be used effectively.

Abstract: Polymer nanocomposites (PNC) have emerged as new materials which can show significantly enhanced mechanical properties over other polymer based materials through the addition of relatively small amounts of nanoscale additives. Rapid prototyping is impacting biomedical in several important ways. This research aims to investigate the potential of using new polymer nanocomposites (PNC) as a raw material for fused deposition modelling machine (FDM). Here, PNCs materials containing a polyamide (PA) and nanoparticles (<5wt%) will be synthesis by mechanical blending using twin extruder compounder to produce 0.85mm diameter of PNC. Dispersion analysis of the nanoparticles in the polymer matrix will be analyzed during the preparation and synthesis process. Futhermore, molecular binding and mixture structure will be investigated by using XPS analysis & Laser Raman Spectroscopy. Material will be characterized for their thermal properties using DSC and processed using FDM, the commercial rapid prototyping (RP) machine. The RP processing parameters will be established and used to produce test specimens to evaluate the mechanical properties of the PNC.

Abstract: This paper presents the results of heat and compression effects on moisture content and water absorption properties in the manufacturing of disposable plate made from Pineapple Leaf Fiber-based material (PALF). The plate was made of PALF and sugarcane bagasse waste as an alternative to polystyrenes, designed to promote the green technology effort on food packaging material. Two different specimens were produced with different compositions of PALF/sugarcane bagasse series N2T8 ( 20 wt% of Pineapple leaf fiber and 80 wt% of sugarcane bagasse ) and series N8T2 ( 80 wt% of Pineapple leaf fiber and 20 wt% of sugarcane bagasse). The specimens were produced using a hot press machine set at compressing temperatures of 50°C, 100°C and 150°C with constant pressure of 0.024 MPa for 10 minutes. Moisture content and water absorption tests were carried out on the specimens to determine the moisture content and water absorption properties. The lower water absorption was obtained for specimen N8T2 because PALF potential to water resistance. This range of properties is expected to be good enough for the requirement of disposable plate and it has the potential as a suitable raw material for strength and lightweight in the manufacturing of disposable plates.

Abstract: Compression spring is one of the most common mechanical componet being used in most mechanisms. Many criteria and constraints should be considered in designing and specifying the spring dimensions. Therefore, it has been one of the standard case studies considered to test a new optimisation algorithm. This paper introduced an optimization method named Gravitational search Algorithm (GSA) to solve the problem of weight minimization of spring. From previous studies, weight minimization of a spring has been investigated by many researcher using various optimization algorithm technique. The result of this study were compared to one of the previous studies using Particle Swarm Optimization (PSO) algorithm. Also, parametric studies were conducted to select the best values of GSA parameters, beta and epsilon. From the results obtained, it was observed that the optimum dimensions and weight obtained by GSA are better than the values obtained by PSO. The best values of beta and epsilon was found to be 0.6 and 0.01 respectively.

Abstract: It is strongly desirable for the vehicle to improve passenger safety and at the same time to reduce the weight of the vehicles. A hollow section for the body structure of automobiles is studied. A high strength steel sheet is used to make the hollow sections in this studied, which are typically joined by resistance spot welding have insufficient energy absorption because the joins are not continuous. Thus, to overcome this problem, the hollow section is joined using the hemming process. The high strength steel hollow sections joined by hemming and resistance spot welding were then examined by tensile and fatigue tests. The hollow section with hemmed joins showed better performance in both tests. The overlapping joins of the hemmed hollow section have greater strength as compared to the resistance of spot welding joins.

Abstract: A hydroxyapatite is known as one of vital materials and common use in biomedical field and concentrated in clinical area. In relation to the above, the development of hydroxyapatite powder becomes an attractive research lines due to simplify in produce it. Thus in this paper the researcher stress out about Hydroxyapatite powder gained from the natural sources or so called as the waste of Tilapia bone and scales. The raw bones of and scale were undergo to crushing process to form in powder size (0.2 mm) then analysed by X-ray Diffraction (XRD) to identified the mineralogy of raw bone. Moreover the powder of fish bone and scales also go through to Scanning Electron Microscope (SEM) machine to analyse the microstructure of the powder while EDS act as device to determine the chemical composition of the sample powder. Sample powder then forward calcination process at selected temperature range to as a cheaper method in obtained hydroxyapatite raw sources. The range of calcination temperatures are between 800°C to 1000 °C. The sample preparation were analysed in both condition before and after calcination process by using XRD, SEM and EDS. The HAP crystalline composition of tilapia bones for raw powder and at 800 °C are similar with HAP pattern (JDS 00-009-0432) and the chemical reaction is Ca₅(PO4)₃(OH) then at temperature 900 and 1000 similar to HAP pattern (JDS 00-055-0592) with chemical reaction equal to Ca₁₀(PO4)₆(OH)₂.

Abstract: Carbon brush has been developed for several decades for electric machines in microelectronic era. It is the electromechanical that connect the circuit to generate an electric motor. Mineral graphite always used as a raw material in producing carbon brush beside the uses of charcoal. This study is propose to use a coconut shell (CS) as waste material that can be recycle and sustainable to produce a carbon pre-cursor. This research is conducted to minimize the percentage of graphite or charcoal as a raw material in producing a carbon brush by replaced a CS as a raw material and produce a carbon brush for railway application. Several process such as baking, crushing, sieving, mixing, compacting and sintering are used in this study to produce a carbon brush. The formation of the carbon (C) had been produced by reaction of combustion in nitrogen atmosphere with 800°C temperature to produce carbon pre-cursor. The carbon brush sample then been prepared by mixing a copper powder and epoxy resin with different ratio of mixture. The suitable percentage of epoxy resin that could form a solid cylindrical shape was 15 %. Sample of carbon brush had been baked at 800°C to form the highest carbon. In this study, copper powder can produce a better conductivity where the sample can permit current flow through it. By using 60 % copper powder, the sample produce less porosity which resulted for high density. Lesser the pores of carbon brush sample produce low resistivity and high conductivity.

Abstract: The problem of natural convection fluid flow and heat transfer of TiO₂-water nanofluid inside of two differentially-heated square ducts is analysed numerically by finite difference method. The outer duct is maintained at a constant temperature T_c, while the inner duct is kept at higher constant temperature T_h. The effect of the Rayleigh number, Ra and the nanoparticle volume fraction, φ on the heat transfer and Nusselt number, Nu are investigated and compared to previous study.

Abstract: Computational modelling of dissolved gas bubble formation and growth in supersaturated solution is essential for various engineering applications, including flash vaporisation of petroleum crude oil. The common mathematical modelling of bubbly flow only caters for single liquid and its vapour, which is known as cavitation. This work aims to simulate the bubble nucleation and growth of dissolved CO₂ in water across a cavitating nozzle. The dynamics of bubble nucleation and growth phenomenon will be predicted based on the hydrodynamics in the computational domain. The complex interrelated bubble dynamics, mass transfer and hydrodynamics was coupled by using Computational Fluid Dynamics (CFD) and bubble nucleation and growth model. Generally, the bubbles nucleate at the throat of the nozzle and grow along with the flow. Therefore, only the region after the throat of the nozzle has bubbles. This approach is expected to be useful for various types of bubbly flow modelling in supersaturated condition.