Applied Mechanics and Materials Vol. 918

Abstract: A comprehensive understanding of powder flow is essential, particularly in the synthesis of additives in the solid free-forming process and dosage dispensing in pharmaceutical industries. The vibration method is the most widely used for inducing powder flow. In this method, a hopper containing powder is vibrated by a piezoelectric system to allow powder flow. However, there are several drawbacks in this method, particularly in the degree of consistency of the resulting flow. This occurs because the vibration characteristics created have a single axis direction, resulting in which can lead to powder compaction. To resolve this problem, this research is conducted to determine the flow properties of titanium powder dispensed by 2-axis vibration. The titanium (Ti) powder having a size of less than 74 μm in the powder hopper was vibrated for 15 min by a DC motor and the weight of the dispensed powder was measured to evaluate the consistency of the resulting powder flow. The result shows that the powder flow generated by the DC motor was consistent during the period of dispensing. However, the powder flow rate dropped up to 8.6% during 5-10 min of dispensing at a speed of 1800 rpm. In conclusion, the 2-axis vibration by using a DC motor could prevent the powder compacting phenomenon and ensure a consistent flow of micro-sized powders during the dispensing process.

Abstract: Direct chill (DC) casting has been considered as one of the promising casting methods that can be used to produce aluminum alloys billet. The process is conducted by pouring aluminum metal into a water-cooled mold. The billet shell begins to form when molten aluminum contact directly with the mold (this is also known as primary cooling). Afterward, the starting block is pulled downwards at a specified casting speed to achieve desired aluminum billet. The start-up phase during the DC casting process is considered a crucial step since it may determine the formation of defects in the casting products. This research aims to investigate the casting defects on the aluminum alloy that were formed during the start-up process of DC casting. The results show that the billet failed to form following the downward movement of starting block. Meanwhile, the billet tended to stick to the mold wall due to several factors, such as too low a pouring temperature, a less-round mold shape, the poor quality of the hot top and graphite ring, and the water that entered the mold during the casting process. It also noted several markers of the casting defects that occurred during the DC casting process such as liquation or bleeding, cold folding, billet stuck in the mold, butt structure, and rough billet surface.

Abstract: In the present research, the fatigue crack growth (FCG) of AISI 1020 steel with and without pre-deformation were characterized by using MTS Landmark 100 kN under fatigue loading at ratio (R) = 0.3, P_max = 0.7 and f = 10 Hz at room temperature. Tensile test results show that 6.25% pre-deformation given on the steel increases of yield strength. In contrast, the ultimate tensile strength, elastic modulus and elongation decrease. The FCG rate (da/dN) of AISI 1020 steel without pre-deformation determined at stage II is 6.12´10^-11ΔK^2.94 m/cycle and steel with 6.25% pre-deformation is 8.03´10^-10ΔK^2.02 m/cycle. According to microstructural observation for the pre-deformation steel, plastic deformation formed on the steel in the axial direction affects the FCG rate of the steel, leads to crack retardation for certain period of time. SEM fractographic observation on the fracture surface of the steel shows that a transgrannular crack length of 12 mm for 42,000 cycles occurs at ferrite grains. The steel failed when the crack length reached ~18.1 mm within 43,500 cycles and continuing up to 43,549 cyles, the steel experienced static failure.

Abstract: Metal injection molding (MIM) feedstock is composed of Cu powder and a complex binder system that consists of PA6, MgSt, and GMS with various solid loading (43-53vol%). Cu powders used are fabricated by gas and water atomization. Powder particle shapes used have spherical and dendritic shapes. Sphericity of particles can be identified by Scanning Electron Microscopy (SEM). A rheology test is used to ensure the optimum solid loading and investigate the influence of particle shape. The pseudo-plastic behavior of all the feedstock is exhibited by decreasing viscosity along with increasing shear rate for all working temperatures. In this study, rheological test result such as viscosity, flow activation energy, and flow behavior index of feedstock indicates that the optimum solid loading was selected as 43 vol%. Both gas and water atomized powders are desirable for MIM feedstock. According to the rheology behavior test, gas-atomized powders with spherical shape has better rheology stability than water-atomized powders with dendritic shape. The proper MIM feedstock was selected to solid loading 43 vol% with gas-atomized powders.

Abstract: Sand casting is a metal casting process to make a component by pouring molten metal into the sand mold. The casting process, the sand is the fundamental material used for mold making. The sand used is generally silica sand, river sand, mountain sand, and beach sand. The sand for molding must have requirements such as having formability, suitable permeability, good distribution of sand grain size, resistance to high temperatures, suitable binder composition, and sand must be cheap. This study investigated to determine the potential of Krueng Mane river sand in Aceh Indonesia for its possible use for metal casting. The important properties studied are moisture content, total clay content, grain fineness number, and grain shape. Tests are carried out following the standards and procedures defined by the American Foundrymen’s Society (AFS). Results obtained revealed that the river sand has average moisture content of 7.78 %, clay content of 3.20%, and grain fineness number (GFN) of 46. Krueng Mane river sand will be suitable for casting of casting of light steel, heavy grey steel, medium grey iron, and non-ferrous metals, with the addition of binding agent in suitable proportion.

Abstract: Sustainability is one of the most challenging concepts in the global mining industry. The purpose of this is to limit the harmful effects of mineral extraction on the environment and at the same time to meet the present and future needs of civilization. Therefore, we should blaze the path leading to sustainability and supply security, as well as identify the factors affecting these concepts. Thus, in this paper, the main factors are listed and defined. They are divided into two main categories: the positives and the negatives. The positives are the longevity of the minerals' mining, the index of the annual met need, the environmental-social condition of the resources, and the condition of the resources in friend countries. Also, the negative ones are the harmful chemicals released, the energy required per ton of minerals, annual CO2 emitted per ton, and recyclability. Accordingly, the factors can be used to make a strategic plan for the future of the minerals supply of a country. So, the framework developed leads the authorities to find the solutions to the sustainability of minerals' supply and increase the security of mining productions.

Abstract: It is well-known that silica sand is a special type of quartz sand that is suitable for glass fabrication due to its high silica content and low content of iron oxide. In this work, chemical analysis has been carried out on a sand sample from the Nong Phok site, Roi Et province, northeastern Thailand. The geological resources show that this site possesses a surface-to-near surface sand deposit. The grain of fine white sand consists of clear crystals. The grain shape is mainly angular-to-round. Chemical analysis shows that the sand contains more than 99 wt% silica and small amounts of Al, Ca, Ti, and Zr which is in agreement with international standards for glass production. The sand has been used as raw material for the fabrication of soda-lime, lead crystal, and lead-free high refractive index glasses. The colorless and various colored glass products have been satisfactorily used in domestic art and glass manufacturers which promotes local employment and economics.

Abstract: Blasting has been adjudged as the cheapest method of hard rock fragmentation. The itinerary of rock breakage through blasting in open pit mines is a complex portent which is measured via various variables and parameters. This research investigates the impact of short burden and spacing on blasting output with the aim of establishing a more suitable and economically viable approach. Trials and proposed methods were adopted to investigate blasting geometry results. Results obtained showed that the trials method of 1.2 m by 1.2 m and proposed blasts method of 2.0 m by 2.0 m burden and spacing at 9m depth, covered areas were 80.64 m² and 99.36 m² respectively, while at 12 m depth with same blasting geometry covered 224 m² and 276 m² respectively. The first trial and proposed blasts methods using burden and spacing of 1.2 m by 1.2 m produced 2,583.71 tons and 2,387.62 tons respectively. Hence, with the use of 2.0 m by 2.0 m burden and spacing, the blasts operations produced 7,176.96 tons and 6,632.28 tons respectively. Meanwhile, the results revealed that, short burden (≤ 1.2 m by 1.2 m) threatens safety in which flyrocks are spawned and it’s dangerous to equipment and personnel, at the same time, the areas covered, quantity produced (i.e. volume) and the tonnage were small compared to the engineering control methods. However, it was found that the trials blast methods were not economically worthwhile in terms of explosive consumption compared to the proposed measure of the geometry.

Abstract: The main aim of this study on silica sand using a spiral concentrator using the design of experiments DOE) approach is to improve the silica content of the tailing sand for the glassmaking process. Three significant operational parameters of the spiral concentrator, namely feed rate (t/h), solid feed (wt.%), and splitter position (cm), were investigated to observe their effects on the SiO₂ grade (%) and recovery of SiO₂ (%) in the middlings using Design of Experiments (DOE). The raw sample was sieved to prepare the feed sample in the size range of -600+75µm, which was the suitable particle size range for the glassmaking process. The SiO₂ grade (%) of each middling fraction from 3³ test runs was determined from XRF analysis. The analysis determined that the feed rate and weight of the solid feed (wt.%) significantly affected the separation, while the splitter position in the investigated range (4.5-5.5cm) showed a negligible effect on the percentage and recovery of SiO₂ in the middling fraction. It was observed that a maximum SiO₂ grade of 94.98% was achieved at a solid feed of 25%, feed rate of 0.63 t/h, and splitter position of 5.5cm. The highest SiO₂ recovery of 89.74% was achieved at the solid feed of 15%, feed rate of 0.45t/h, and splitter position of 5.0cm. A trade-off between the optimized results for SiO₂ Grade (%) and recovery of SiO₂ (%) responses using overlaid contour plots suggested a feed rate of 0.58 t/h of feed rate and 25 wt. % solid feed regardless of the splitter position. The customized range of parameters is expected to produce 94.51% SiO₂ grade (%) and 80.11% recovery of SiO₂ in the middling fraction.