Studi Karakteristik Fluidisasi Dan Aliran Dua Fase Padat- Gas (Pasir Besi- Udara) Pada Pipa Lurus Vertikal

Fluidization and solid â gas flow have been applied in many industrial devices, e.g. fluidized bed combustor, cyclone pre-heater, electrostatic precipitator, pneumatic conveyor and solid-fuel drying installation. This research is aimed to investigate the characteristics of fluidization and solid â gas flow of iron sand â air in a vertical tube. The iron sand particles were placed in 24 mm I.D. bed column and blown by air which had 1,0 â 1,1 kg/cm\u27 in pressure and 28,75°C in average temperature. They were lifted and moved along the column. There were given some variation, i.e. bed height, particle\u27s size, hole\u27s number of the grid and superficial velocity. Pressure drop was measured by using water column manometer. Results of this research were compared to the theoretically estimation. Result shows that the minimum fluidization velocity for particles whose mean diameter of 0,1896 mm and 0,3103 mm occurs in range of 0,13 - 0,2 m/sec. Pressure drop gradient of minimum fluidization are found in range of 18 â 24 kPa/m. While, the terminal velocity occurs at 1,8 â 2,0 m/sec. Keywords: fluidization, solid-gas flow, iron sand - air, vertical straight tube, air superficial velocity, pressure dro

Visualization of Fluidization and Solid-Gas (Iron Sand-Air) Flow Regimes in A Vertical Straight Tube

Abstract The aim of this research is to obtain fluidization and solid - gas flow regimes in a vertical straight tube of 24 mm in diameter. Iron-sand particles and air are utilized as the solid and gas phase respectively. The regimes of fluidization and solid-gas flow are recorded using digital camera. In general, results show that there are six regimes offluidization process i.e. fixed bed, particulate bed, bubble, slugging, turbulent bed, and fast fluidization. In addition, the solid-gas flow in a vertikal tube yields the dilute and dense phase.. Keywords: Fluidization, solid-gas flow, flow regimes

PENGARUH TEMPERATUR EKSTRUSI TERHADAP SIFAT FISIS, KIMIAWI DAN KEKUATAN TARIK FILAMEN ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE (UHMWPE)

Currently, fused deposition modeling (FDM) has become a popular 3D printing technique for the fabrication of polymeric parts. In this technique, a polymer filament is melted and deposited layer-by-layer to form 3-dimensional objects. However, there are still limited number of polymer types that has been successfully used as a raw material for the FDM process. Up to now, there is still no filament made from ultra high molecular weight polyethylene (UHMWPE) available in the market. Therefore, a preliminary study concerning the fabrication of such UHMWPE filament needs to be conducted. In this study, the influence of extrusion temperature used in the fabrication of UHMWPE filament on the physical, chemical, and tensile strength of such filament was studied. The extrusion process was carried out by adding polyethylene glycol (PEG) and paraffin oil (PO) to improve the processability of UHMWPE material and with temperatures of 160 oC, 170 oC, and 180 °C. The result of examination by using electron microscope revealed that extrusion process of this polymer was running stable. The characterization by using differential scanning calorimetry (DSC) indicated a decrease in the degree of filament crystallinity as the extrusion temperature decreased. The characterization by using Fourier-transform infrared spectroscopy (FTIR) indicated no changes in the chemical compositions over the filament products with the increasing extrusion temperature applied. Meanwhile, it is also indicated from this study that the maximum tensile strength decreased as the extrusion temperature got lower. In this case, the highest maximum tensile strength could be achived by the UHMWPE filament extruded with temperature of 180 °C, i.e., with an average tensile strength of 22.52 MPa

Ekstruksi dan karakterisasi filamen komposit Polylactid Acid (PLA) / Carbon Nano Tube (CNT)

Dewasa ini teknologi additive manufacturing (AM) mengalami perkembangan yang pesat. Salah satu metode additive manufacturing yang saat ini populer di berbagai belahan dunia adalah metode fused deposition modelling. Prinsip kerja metode ini adalah dengan cara mengekstrusi material filamen polimer yang meleleh dan sudah melewati temperatur rekristalisasinya melalui sebuah nozzle, kemudian produk akan terbentuk secara lapis demi lapis yang dibentuk melalui gerakan relatif dari meja mesin. Dalam pengaplikasiannya, material filamen dapat dibuat dalam bentuk komposit sehingga diperoleh sifat-sifat unik tertentu sehingga dapat digunakan pada bidang-bidang tertentu. Salah satunya adalah pada bidang kesehatan, sebagai pembuatan implan atau jaringan tubuh dengan memiliki kekuatan yang tinggi dan bersifat biodegradable. Pada penelitian ini, dilakukan pembuatan filamen komposit PLA-CNT dengan metode ekstrusi. Proses ekstrusi dilakukan dengan variasi temperatur 143, 145, dan 147ºC dengan memberi tambahan polyethylene glycol (PEG) sebagai plasticizer untuk meningkatkan fleksibilitas dan workability. Hasil pengamatan dengan scanning electron microscope (SEM) mengindikasikan bahwa proses ekstrusi berjalan kurang stabil karena terdapat tekstur permukaan yang bergelombang. Dari pengujian karakterisasi differential scanning calorimetry (DSC), derajat kristalinitas pada variasi ekstrusi filamen PLA-CNT mengalami peningkatan seiring meningkatnya temperatur ekstrusi. Pada pengujian karakterisasi fourier transform infrared spectroscopy (FTIR) terdapat perubahan komposisi kimia pada filamen yang signifikan, yang juga sejalan dengan degradasi sifat mekanis. Variasi filamen dengan temperatur ekstrusi 147ºC memiliki nilai kekerasan paling tinggi yaitu sebesar 40,50 MPa

Comparison of Surface Characteristics of Medical-grade 316L Stainless Steel Processed by Sand-blasting, Slag Ball-blasting and Shot-blasting Treatments

In this research, a comparative study was carried out to examine the surface characteristics of medical-grade 316L stainless steel after blasting treatments by using angular silica particles, spherical slag balls and spherical metallic shot. The surface roughness, morphology, elemental composition and microhardness distribution of the stainless steel were determined and the possible mechanisms in the evolution of the surface characteristics of the steel exposed to the blasting treatments were established. The results showed that all the blasting treatments conducted in this research increased the roughness and hardness of the steel surface. In this case, the roughest stainless steel surface was achieved by the slag ball-blasting treatment, but the stainless steel with the hardest surface and the thickest hard subsurface layer was obtained by the shot-blasting treatment. On the basis of the findings in this research it can be concluded that the physical properties and surface morphology of particles or shot used in the blasting treatment are critical parameters in determining the surface characteristics of blasted stainless steel

Finite Element Analysis of Osteosynthesis Miniplate for the Reconstruction of Parasymphyseal Compound Fracture

In the last two decades, the use of osteosynthesis miniplate has been growing to aid the healing process and reconstruction of fractured mandibular bone. In principle, the plate is used to provide stable fixation of the fractured bone tissue during the healing process and reconstruction. Based on earlier studies, it is noted that arrangements and geometry of the osteosynthesis miniplate played a critical role in determining the stability of the fractured mandibular bone, as well as the miniplate. In this research, a simulation with finite element method (FEM) was carried out to investigate the influence of the number of holes in an osteosynthesis miniplate on the stability of fractured mandibular bone and the corresponding miniplate after the implantation. For this purpose, a set of osteosynthesis miniplate with three different configurations was taken for simulation using a three-dimensional (3D) model of mandibular bone generated from the patient through computed tomography (CT). The result of the simulation showed that all the miniplates with three configurations tested were stable enough to prevent movement of fractured mandibular bone. Moreover, fixation with a pair of miniplates having four screw holes demonstrated the desired result; as indicated by the lowest value of displacement, pressure on the bone surface and pressure on the miniplate

Recycling of Magnesium Alloy Scrap by Remelting and Chemical De-coating Process

The growing demands of magnesium (Mg) based materials had risen new challenges related to disposal of unused parts and a huge amount of waste made by such metals. Attempts to recycle the scrap of these materials through remelting had become one of the preferred choices. However, a series of preliminary steps should be carried out to reduce the impurities as well as to maintain the quality of the casted ingot, for instance, by applying de-coating for removing paints or coating substrates at the scrap surface prior to remelting. In this research, the effects of chemical reagent de-coating on the properties of ingot obtained from recycling Mg scrap were studied. A commercial paint removal liquid was preferred as the reagent for removing paint layers over the Mg scrap surface. The de-coated scrap was then remelted in a conventional furnace with NaCl powder as the fluxing layer. The results of this study noticed the importance of chemical de-coating process to reduce the impurity contents in the ingot which might be originated from the coating or paint substrates covering the Mg scrap. Meanwhile, the density and hardness of the Mg ingot processed without de-coating were obviously higher than that had been cleaned previously with paint removing agent

Karakterisasi Billet Paduan Magnesium Hasil Daur Ulang dengan Metode Direct Chill Casting

Direct chill casting merupakan proses pengecoran semi kontinyu yang menghasilkan produk berbentuk billet, ingot, dan lain-lain. Penelitian ini bertujuan untuk mengaplikasikan direct chill casting sebagai metode daur ulang scrap magnesium. Material yang digunakan adalah scrap paduan magnesium yang dilebur kembali menggunakan tungku krusibel dan dilanjutkan dengan proses pengecoran menggunakan metode direct chill (DC) casting. Proses pengecoran dilakukan bertahap dengan mengunakan kecepatan pengecoran sebesar 56 mm/menit, 100 mm/menit dan 82 mm/menit. Temperatur tuang magnesium paduan sebesar 720°C dengan debit air pendingin konstan sebesar 11,4 liter/menit. Billet  hasil DC casting dengan kecepatan pengecoran sebesar 82 mm/menit memiliki cacat visual yang lebih sedikit dibandingkan dengan billet hasil DC casting dengan kecepatan pengecoran sebesar 56 mm/menit dan 100 mm/menit. Persentase porositas terendah dihasilkan dari kecepatan pengecoran 82 mm/menit, yakni sebesar 0,7%. Struktur mikro yang dihasilkan dari proses DC casting berbentuk dendritik. Kekerasan billet tertinggi dihasilkan pada kecepatan pengecoran 100 mm/menit yaitu sebesar 329 HVN atau 3,23 GPa.

EFFECT OF SURFACE MECHANICAL ATTRITION TREATMENT ON ROUGHNESS AND WETTABILITY OF AISI 316L

Surface roughness and wettability determines the rate and quality of protein adsorption and cells adhesion on biomaterial. A rough- and hydrophilic-surface are better for adsorption of specific proteins and promotion of the following biological processes than a smooth- and hydrophobicone. This paper discusses the effect of surface mechanical attrition treatment (SMAT) on the roughness andwettability of AIS1316L. The polished samples were treatedfor 0 - 20 minutes. The result shOtt'sthat SMA Tprocess enhances surface roughness and decreases droplet contact-angle. Increasing of SMAT duration enhances microhardness of the sample's surface and subsurface, and yields a relatively smooth surface that reduces hydrophilicity of A/SI316L.</p

Fabrication of Metallic Biomedical Scaffolds with the Space Holder Method: A Review

Bone tissue engineering has been increasingly studied as an alternative approach to bone defect reconstruction. In this approach, new bone cells are stimulated to grow and heal the defect with the aid of a scaffold that serves as a medium for bone cell formation and growth. Scaffolds made of metallic materials have preferably been chosen for bone tissue engineering applications where load-bearing capacities are required, considering the superior mechanical properties possessed by this type of materials to those of polymeric and ceramic materials. The space holder method has been recognized as one of the viable methods for the fabrication of metallic biomedical scaffolds. In this method, temporary powder particles, namely space holder, are devised as a pore former for scaffolds. In general, the whole scaffold fabrication process with the space holder method can be divided into four main steps: (i) mixing of metal matrix powder and space-holding particles; (ii) compaction of granular materials; (iii) removal of space-holding particles; (iv) sintering of porous scaffold preform. In this review, detailed procedures in each of these steps are presented. Technical challenges encountered during scaffold fabrication with this specific method are addressed. In conclusion, strategies are yet to be developed to address problematic issues raised, such as powder segregation, pore inhomogeneity, distortion of pore sizes and shape, uncontrolled shrinkage and contamination