Estimation of Appropriate Process Parameters for a Plasma Electron Beam Re-Melting Process Using Finite Element Analysis

Metal additive manufacturing using electron beam melting (EBM) process applies electron beam for heating, sintering, and melting of powders to fabricate a three-dimensional component. The component may contain residual porosity internally and may be subjected to poor surface finish externally. To improve the quality of the surface finish and densification, re-melting is conducted. The purpose of this paper was to estimate the appropriate process conditions for a plasma electron beam remelting process using heat transfer finite element analyses (FEAs). The impact of the travel speed of table and thickness of the deposited part on temperature distributions were examined. The size of molten pool was estimated from the results of the thermal FEA. From the estimated size of molten pool, the travel speed of table and the hatch spacing between remelting tracks are discussed and selected as the appropriate process conditions for electron beam re-melting process from the perspective of minimum overlapping region of the molten pool

The spare part inventory management system (SPIMS) for the profound heritage Sdn Bhd: a case study on the EOQ technique

The inventory management is an important part of supply chain management, which protects the schedule of production or maintenance towards any type of disturbance. This research emphasized on the development of the Spare Part Inventory Management System (SPIMS) for the Profound Heritage Sdn Bhd (PHSB), which is currently adopting the manual Kadex method. This automatic software used the Economic Order Quantity (EOQ) in the periodic review environment to control the inventory and the software was written using the Microsoft Visual Studio 2012. Therefore, this research will not only helps the PHSB but also increased literature on the actual implementation of the EOQ technique in the periodic review environment. This newly developed SPIMS have the ability to keep the spare parts transaction records, calculate the EOQ for each part and remind the user to purchase more spare parts at its dedicated “When to Order” date. The developed SPIMS performance was then evaluated by comparing it to the current Kadex or manual method. The method, which produced the lowest average inventories, is considered as the best method. Comparison across the overall average inventory indicated that the EOQ with zero opening balance (which represented a system that start with zero opening inventories) performs better than the Kadex method. However, the Kadex method is found to perform better than the EOQ when current opening balance is considered. The deterioration in the EOQ performance, when current opening balance is considered, is due to the fact that more data and longer time for observation is required before the EOQ reached its steady state. However, it is expected that the result similar to the EOQ with zero opening balance will be observed when the EOQ (with opening balance) reached it steady state. In addition, the EOQ also produces some shortages on the stock, which is nonexistent in the Kadex method. This problem is caused by the EOQ inability in detecting any shortages as the inventory will only be checked on a specific time interval called the “when to order” date. Due to this, an improvement on the SPIMS is needed. Rather than reviewing the inventories periodically during the “when to order” date, it is suggested that the SPIMS should adopt the continuous review/monitoring environment to optimize its performance

Modelling and control of partially shaded photovoltaic arrays

The photovoltaic (PV) array controlled by Maximum Power Point Tracking (MPPT) method for optimum PV power generation, particularly when the PV array is under partially shaded condition is presented in this paper. The system modelling is carried out in MATLAB-SIMULINK where the PV array is formed by five series connected identical PV modules. Under uniform solar irradiance conditions, the PV module and the PV array present nonlinear P-V characteristic but the maximum power point (MPP) can be easily identified. However, when the PV array is under shaded conditions, the P-V characteristic becomes more complex with the present of multiple MPP. While the PV array operated at local MPP, the generated power is limited. Thus, the investigation on MPPT approach is carried out to maximize the PV generated power even when the PV array is under partially shaded conditions (PSC). Fuzzy logic is adopted into the conventional MPPT to form fuzzy logic based MPPT (FMPPT) for better performance. The developed MPPT and FMPPT are compared, particularly the performances on the transient response and the steady state response when the array is under various shaded conditions. FMPPT shows better performance where the simulation results demonstrate FMPPT is able to facilitate the PV array to reach the MPP faster while it helps the PV array to produce a more stable output power

Forecasting of Palm Oil Fruit Delivery Quantities using the Trend Adjusted Exponential Smoothing: A case study

Palm oil industry has increasingly become the important industry for Malaysia. However, only a limited number of researches have been conducted on improving the palm oil industries. This research attempted to contribute by improving forecast activity along the palm oil industry. Specifically, this research centred on the development of forecast software for a Malaysian based palm oil estate. The developed forecasting software can be used to assist the estate manager in predicting accurately their monthly delivery quantity to the palm oil mill. The forecast technique selected for this research was the trend adjusted exponential smoothing technique. The performance of the trend adjusted exponential smoothing technique based software was then compared to the naïve method. Comparison in the performance indicated that the trend adjusted exponential smoothing produces lower root mean square error, which is equivalent to 14.6% of error produced by the naïve method. This finding emphasises the efficiency of the trend adjusted exponential smoothing in predicting the monthly delivery quantity by the palm oil estate

Post-heat treatment of electrochemically carburized low-carbon steel

Limited studies are available on post-heat treatment (tempering/annealing) of electro­chemically carburized low-carbon steel, which can relieve internal stresses induced by the quenching process. In this study, the electrochemical carburization was carried out using the electrolyte mixture of sodium carbonate (Na2CO3) and sodium chloride (NaCl) under a CO2 gas environment and 800 °C. The samples were then quenched in either water or oil. The peak hardness of the water-quenched sample (WQ) was higher than the oil-quenched sample (OQ). Comparatively, post-heat treated (tempered and annealed) samples showed lower peak hardness compared to quenched samples. An optical microscope was used to observe microstructural changes, while X-ray diffraction (XRD) was used to examine metal phases within all samples. The full width at half maximum (FWHM) of the martensite peak supported the stress relief in both tempered and annealed samples. Scanning electron microscope (SEM) with energy dispersive X-ray (EDX) was applied to determine the elemental composition of as received and electrochemically carburized and quenched low-carbon steel samples. The carbon content of the WQ sample was relatively higher than the OQ sample, whereas the tempered samples showed higher carbon content compared to the annealed samples, but both were lower than for quenched samples. Electrochemical carburization increased the carbon content and improved the hardness, while the tempering or annealing process relieved internal stresses that resulted in the hardness reduction

Plastic straining and concomitant microstructure recrystallization of Ni-Cu alloy in the undercooled condition

Microstructure and microtexture of rapidly solidified undercooled Ni-Cu alloys were investigated. The characteristic undercooling of Ni80Cu20 alloy was determined as 45K, 90K and 160K. Dendrite deformation due to rapid solidification led to strong deformation microtexture. Due to recrystallization upon annealing after recalescence, many subgrains were formed in the microstructure. Further, annealing the quenched alloy at 900℃, new microtextures and subgrains were formed, which was due to recrystallization and dislocation network rearrangement. The results of comparative experiment proved the recrystallization mechanism of the microstructure refinement in the non-equilibrium solidification structure of the undercooled binary alloy

Microstructure transition and grain refinement mechanism of undercooled alloys

The solidification microstructures of undercooled Ni90Cu10 alloys under different undercoolings were studied systematically by means of melt coating and cyclic superheating. In the obtained undercooling range, the solidification structures of the two undercooled alloys have similar transformation processes, and there are two kinds of grain refinement structures under the conditions of low undercooling and high undercooling, respectively. The microstructures of the two grain refinement processes were analyzed in more detail by electronic backscattering diffraction technique. Under the condition of small undercooling, dendrite remelting is considered to be the main reason of grain refinement. However, under the condition of high undercooling, the existence of annealing twins and obvious migration of grain boundary are important evidences for the occurrence of recrystallization process

Development of Mixed Vertical Axis Wind Turbine (MVAWT) for low wind condition

Small-scaled renewable energy generation such as micro-hydro and domestic solar panel has become the recent trend of research in order to achieve sustainable energy generation and to eliminate the reliance of geographical selection and large farm area. As for the case of wind energy, a wind turbine that can operate at low wind condition are desirable. This paper presents a mixed design for Vertical Axis Wind Turbine comprises of Savonius and Darrieus rotors, being assembled together as a single rotor turbine. The mixed wind turbine model (MVAWT) was fabricated and tested in our lab as prove of concept. Experiments conducted on 5 MVAWT’s configurations and being compared to a standalone Darrieus turbine with +3 degree pitch angle, showed promising result in lowering the self-start speed of the Darrieus turbine. It was observed that all the positive pitch angle MVAWTs has started to rotate at lower wind speed (about 1.8 m/s) while the standalone Darrieus turbine was only started to rotate at wind speeds more than 3.0 m/s. However, the lower self-start were also being compensated by lower turbine rotational speed. With the low self-start speed in the MVAWT, it will enable the wind energy capture for a longer period of time at a low wind condition site. This development should lead to an interesting research on optimizing the mixture of Savonius and Darrieus turbine for a localized low wind speed conditions in the future

Flow instability of dope solution in hollow fiber spinning process for different flow channel length

The study demonstrated the effect of different flow channel length on the spinneret with respect to the ceramic hollow fiber membrane morphology. A smartly designed spinneret is utilized for the spinning process where the nozzle used can be change to different length via the use of adapters. Thus, allowing the effect of having different flow channel length to be investigated. Three spinneret adapters with different nozzle length were fabricated at 29 mm, 34 mm, and 39 mm. Ceramic hollow fiber membrane is produced using these configurations in the spinning process. Then, the micrographic cross sections of hollow fiber membranes is investigated using Scanning Electron Microscope (SEM) where it shows finger like, dense layer and damage structure morphology. Out of the samples investigated, hollow fiber membrane spun using 39 mm nozzle length produce the best concentricity. CFD simulation is initiated to study the flow behavior inside the flow channel to correlate with that of the experimental result attained

Shredder machine for plastic recycling: A review paper

Plastic pollution has become a global concern due to poor plastic waste disposal management. As an alternative, independent recycling efforts are necessary. A Plastic shredder machine is a preliminary machine used to cut plastic waste into small pieces before turning it into useful products. The concept design of the shredder machine that is currently available is fairly similar. The shaft and blades are the critical components in the shredder machine that determines its performance. The geometry and orientation of the blades that were fitted into the single or double shafts were found to directly affect the shredding performance. Therefore, this article aims to review the various geometry and orientations of the blades that give direct effect on the shredding performance, as well as identifying the research gaps related to the shredder machine for plastic waste materials