Key Engineering Materials Vol. 659

Abstract: In the production of netting hook, which requires wear resistance and long service life enabling the fishing net production with high efficiency, there has been some studies to achieve its forming method for high durability and designated smooth surface. The process of investment casting or known as “lost wax casting” is one of casting methods to fabricate metal part with a complex shape. Flow behavior of stainless steel grade 431 at the temperature higher than 1600°C is a critical factor in casting mold design of the lost wax process. In the study, CAST-DESINER^TM simulating software was used to analyze flow of liquid metal to clarify the solidification of SS431 which caused defects in the product. Non-preferred heat transfer phenomena and using of the unsuitable mold design normally lead to defects in casting such as misruns, cold shuts, shrinkage, pin holes and porosity. Parameters in casting such as pouring temperature, preheating temperature, preheat time, pouring rate and cooling rate were given by the current production condition. The experimental design technique for simulation analysis of casting and gating system has been designed to be consistent and appropriate to the casting part. The cross-sectional design of the runner was two types of hexagonal and circular cross-section runner. The angle of gating system was kept constant at 90 degrees to the runner. As a results of the simulations, shrinkage porosity, filling time as well as solidification time were used to evaluate the cross-sectional design of runners. It was found that a circular cross-section runner led to the shorter filling time than a hexagonal one. Furthermore, there was no remarkable difference of shrinkage porosity in all simulated conditions. However, in terms of filling time, the results depended on the combination of runner design and gating system.

Abstract: Hydrocyclone is novel optional equipment that can be applied in solid separation for crude palm oil process because of its advantage over the existing technology. Hydrocyclone is a cost-effective, continuous tool which is easy for maintenance. The objective of this research is to investigate the effect of vortex finder, inlet, and body diameter of hydrocyclone on separation efficiency of palm meal from crude palm oil by using PVC resin as the solid phase and biodiesel B5 as the liquid phase. All parameters were simulated using computational fluid dynamic, CFD. In addition, the inlet diameters were tested experimentally. The feed flow rates in both simulation and experiment were varied from 4 - 14 L/min at the constant flow ratio of 0.2. Experimental design was clearly specified. The vortex finder diameters of 3.8, 4.8, and 5.8 mm were also simulated as well as the inlet diameters of 5, 6, and 7 mm. Three sizes of body diameter of 30, 40, and 50 mm were selected as the example sizes. According to the simulation results, the smaller vortex finder, inlet, and body diameter of hydrocyclone revealed the higher separation efficiency.

Abstract: The topic of this research work was to demonstrate the feasibility of a 3D-MID concept using injection molding technique and investigate the effects of two weld line types on the structure and mechanical properties such as tensile, flexural strength and morphology. In order to obtain more understanding of the bonds between polymer and metals, two different polymer bases of polyphthalamide (PPA) with the same type and amount of filler content were produced by injection molding at the different processing conditions. A mold was designed in such a way that weld and meld line can be produced with different angles by changing as insert inside of the mold. The mechanical properties such as stiffness, tensile strength and flexural strength were determined in tensile and flexural tests, respectively. The results showed in line with the expectation of high reduction on mechanical properties in area where weld/meld lines occurred. The result of tensile test was clearly seen that weld and meld line showed a considerable influence on mechanical properties. The reduction in tensile strength was approximately 58% according to weld line types, whereas in flexural strength was approximately 62%. On the other hand, the effect of the injection times and mold temperatures on the tensile strength were marginal.

Abstract: Metal spinning process is widely used for producing complex symmetry components. Main advantage of spinning process is a lower power requirement for large deformation with good surface finish. The aim of this paper is to investigate the influences of spinning process parameters, on spinning force. A three dimensional finite element model of the spinning process of SPCC sheet was successfully developed using elastic-plastic material property. The spinning experiments were carried out on a turning lathe and spinning forces were measure forces using a piezoelectric force transducer. The finite element prediction was compared with the experimental measurements and the results agreed well. Applying the Taguchi method, the effect of four process parameters, i.e. roller diameter, spindle speed, feed rate and feed depth, on spinning force were studied. The Taguchi main effect analysis and ANOVA results show that roller diameter and feed depth are the most important factor influencing the spinning force.

Abstract: A 3-D numerical simulation is performed to study the flow dynamics and mixing characteristics between two different kinds of fluid within T-shaped micro-mixers. Water and ethanol are selected as the mixing fluids due to its application in calibrating the ultrasound imaging equipment. The present work focuses on the effects of inlet velocity and aspect ratio of the mixing channel. The Reynolds number is varied from 0.1 to 300 and the aspect ratio in the range between 0.2 and 1. The flow of interest is laminar, steady and without chemical reaction. It is found that at low Reynolds number, the stratified flow character is presented. As the velocity inlet increases, the mixing efficiency is decreased. However, for the Reynolds number greater than 100 the mixing efficiency is increased due to the buildup vortex structure. Furthermore, when increasing the Reynolds number, the pressure drop significantly increases. Thus, it is seen that both the inlet velocity and aspect ratio significantly affect the mixing efficiency and pressure drop.

Abstract: Motorbike shock absorbers of gravity die cast aluminum A356.0 alloy were being imported in the as-cast condition and later on machined at local foundries and workshops by sub-vendors to achieve the required dimensions and on many occasions a nearly complete solid block was cast and machined to achieve the desired shape but this process not only lowered the metallic yield but also the high machining costs and time required made it very uneconomical. Motorbike shock absorbers are critical vehicle components which are always under load and must never fail suddenly without warning therefore they need to be free of defects like shrinkage and micro-porosity. The thin wall thickness of 6mm and troublesome nature of cores required makes this component quite difficult for the conventional metal caster. The current research paper deals with the methoding, die designing, modeling and simulation, optimization and finally casting of these components following the data produced by the former. Initially a single piece per mold was suggested but later on considering the economics of the project two pieces i.e. left and right were recommended to be cast from a single sprue in each die with a vertically parted permanent die mold. For the methoding calculations the Thermal modulus has been used instead of the conventional casting modulus and for gating the naturally pressurized system is incorporated. Throughout the simulation process a significant number of iterations were made to achieve the final design which ensured a laminar flow of liquid aluminum below the critical velocity limit; the actual die casting results yielded good comparison with the simulation studies showing shrinkage cavity away from the risers and micro-porosity only in ingates.

Abstract: The various methods of silicon wet etching techniques, which utilize ultrasonic agitation to reduce pyramidal hillocks in etched patterns, were evaluated in NaOH+IPA solution. The comparison of the etching methods composed of; 1.) no agitation + sample horizontally orientated, 2.) ultrasonic agitation + sample horizontally orientated, 3.) ultrasonic agitation + sample vertically orientated, and 4.) ultrasonic with rotation agitation + sample vertically orientated. It was found that the percentages of the etched patterns presenting hillocks after etching were 100%, 79.77%, 32.67% and 2.62%, respectively. Ultrasonic coupled with rotation agitation along with the sample vertically orientated is the most powerful etching technique, offering a high yield of smooth etched surface. The difference in etch rate between without agitation and applying ultrasonic agitation was not observed in this experiment, as it was operated in a solution temperature 60-65°C and a 275nm/min etch rate was achieved. The theories that relate to each evaluated method are also discussed.

Abstract: The demand of remaining life assessment of the boilers arises from technical, economic, and legal reasons. Creep is major damage mechanism of primary superheat tube boiler during prolong operation at high temperature and pressure in a water tube boiler. This paper presents the calculation method for the remaining life assessment due to creep damage. The service-exposed primary superheat tube made of 2.25Cr-1Mo steels. During scheduled inspection, wall thickness measurement, metallographic investigation by replica technique, design data and operating condition were used to estimate the remaining life in the form of creep damage accumulation rate calculated from life fraction using Larson-Miller Parameter. The results indicate that the primary superheat tubes satisfy in extension service life. By attaining an accurate and timely discussion of the results, the engineer can manage the maintenance and inspection schedule for the critical part in the boiler.