Search

This study aims to determine the effect of the heat treatment process and pressing on hardness, density, and morphological changes in the microstructure of Al-Si alloys. In this study, the medium used was coconut shell charcoal with a mesh size of 80 at a heat treatment process of 400 °C and a holding time of 75 minutes. The pressing was carried out with a load of 150 N. The result of this research is an increase in the hardness of the Al-Si alloy with an average value of 133 VHN after the Heat Treatment and pressing process. In the microstructure, there is a morphological change in the Al-Si alloy with the reduction of Si elements and also an increase in the density value after the heat treatment process.

This study aims to determine the effect of the mold casting duct variations on shrinkage, porosity defects, density, hardness, and chemical composition of materials. The primary raw material uses melting secondary aluminium through a small-scale smelting furnace. Research study about three kinds of ducts: triangular duct, rectangular duct, and circular duct. The testing chemical composition uses an emission spectrometer. Research founds defects by comparing the dimensions of the original object with the specimen results of each duct variation. The density value calculates porosity defects. ASTM E10 standard Brinell test measures the hardness. Besides, ASTM E3 standard test quantifies the microstructure of the product. The highest average shrinkage is the triangular ducts at 3.68%. The least significant numbers of porosity were in rectangular ducts of 2.964 gr/ml. Higher the density value, the denser the material, and the more negligible the porosity. The density of the material affects the hardness material obtained from the results of the Brinell test. The hardness of the Brinell test brought that the rectangular duct with 102.5 BHN was the most enormous. In addition, the results showed that the chemical composition mainly contained mostly chemical elements (Al) 87.1% as the main chemical ingredient and (Si) 9.51%.

Gray cast iron has graphite flakes which makes it relatively weak and brittle. The addition of magnesium to gray cast iron resulted in nodular cast iron which has spherical graphite. The aim of this research was to investigate the changes in the microstructure and strength due to the addition of magnesium to gray cast iron. Microstructure observations were made by metallographic testing using Scanning Electron Microscopy and Energy Dispersive Spectroscopy. Tensile testing was carried out to measure the yield strength, tensile strength, and modulus of elasticity. The addition of magnesium to gray cast iron was observed to increase the yield strength by 179%, tensile strength by 238%, and decrease the modulus of elasticity by 94%.

This study presents the investigation of friction coefficient effect on stress-strain distribution of ceramic coated aeroengine specific material substrate using explicit finite element method. Half-cylinder-on-flat contact configuration subjected to normal and tangential loading is examined. Elastic ceramic coated elastic-plastic Ti-6Al-4V and Super CMV substrates are assigned to study the influence of different friction coefficient on contact pressure, von Mises stress, tangential stress and equivalent plastic strain distribution. The outcome of present research is quite revealing that stress-strain distribution response is remarkable for sliding step which experiencing significant traction compared to normal loading step. Higher possibilities of coated substrate equivalent plastic strain (plastic deformation) are registered under higher friction coefficient cases due to substantial resistance to overcome relative to tangential motion of contacting bodies.

One of the techniques to increase the hardness of aluminum alloy is by aging process. The aging process includes natural aging and artificial aging processes. This study aims to investigate the effect of artificial aging on the hardness of aluminum silicon alloys. Artificial aging is carried out at two temperature variations, namely 150 and 200 °C. Metallographic test using optical microscopy and scanning electron microscopy were performed to observe the microstructure and deposits of silicon. Investigation of the constituent elements of aluminum silicon was carried out using the Energy Dispersive X-Ray Spectroscopy technique. The mechanical properties of aluminum silicon alloys examined were hardness before aging and hardness after artificial aging at temperatures of 150 and 200 °C. Hardness testing is conducted by Rockwell B hardness testing. The hardness test results showed that the hardness before the aging process was 61.1 HRB, the hardness after artificial aging at 150 °C was 69.11 HRB and the hardness after artificial aging at 200 °C was 80.36 HRB. There was an increase in hardness after the artificial aging process was carried out.

Nodular cast iron is a type of cast iron with spheroid graphite surrounded by ferrite matrix and / or pearlite. The size of the graphite and its matrix affects the mechanical properties of the cast iron. This research was conducted to investigate the effect of Magnesium composition on strength, stiffness and toughness of nodular cast iron. Magnesium addition is performed by adding FeSiMg alloys. After that, the composition of magnesium was investigated by using spectrometry. Then tensile test was conducted to obtain the yield strength, tensile strength and modulus of elasticity. Further, impact test was performed to determine the impact energy needed to break the material. The result showed an increase of yield strength, tensile strength and stiffness and a decrease of toughness.

The purpose of this research is to investigate the corrosion resistance of 5052 aluminum alloy to increasing salinity in sea water. Salt spray chamber was used to measure and compare the corrosion rate of 5052 aluminum alloy with weight reduction method. The experiment was conducted by varying the three concentrations of NaCl solution to compare the corrosion rate of the metal. The test specimens used were aluminum alloy 5052 with length of 6 cm, width of 4 cm and thickness of 0.7 cm. The tests were carried out for 48 hours, aggressive NaCl solutions with concentrations of 3.5%, 4% and 5% were used as an artificial sea water corrosion medium and the temperature in the test chamber was maintained at 35 °C. Corrosion rate for 3.5% NaCl solution, 4% NaCl solution and 5% NaCl solution were 0.197 mm/year, 0.541 mm/year and 0.558 mm/year, respectively. The higher concentration leads to greater corrosion rate.

Logam akan mengalami perubahan fasa selama proses pengecoran, baik perubahan sifat fisis maupun mekanik yang disebabkan oleh proses pembekuan. Perubahan sifat ini antara lain dipengaruhi media pendingin yang digunakan pada saat proses pendinginan. Tujuan penelitian ini adalah untuk membandingkan variasi temperatur pendinginan terhadap kekerasan hasil coran aluminium karena sifat fisis dan mekanis suatu logam sangat penting dalam kontruksi permesinan. Maka dalam penelitian ini digunakan media pendinginan yang berbeda yaitu : Air dengan suhu 15°C, Air dengan suhu 27°C dan Air dengan suhu 55°C. Dari pengujian kekerasan benda uji dengan media pendinginan air suhu 15°C mempunyai nilai kekerasan yang lebih baik dibanding air dengan suhu 27°C dan 55°C. Dari hasil pengujian komposisi kimia terdapat 17 unsur, tetapi hanya 4 unsur yang paling berpengaruh pada aluminium cor yaitu Si, Fe, Cu, dan Zn yang paling dominan. Dilihat dari unsur yang ada pada material ini dapat digolongkan logam aluminium paduan seng (Al-Zn).

Hip Joint is located between the hip and the base of the upper femur. Diseases such as osteoarthritis and rheumatoid arthritis can cause total replacement of hip joints with prosthesis. Hip joint prosthesis’s components consist of acetabular cup, femoral head, and femoral stem. One of acetabular cup material is a polymer. Therefore, injection molding is one of the processes that can be used to produce it. The problem that often arises is a product defect due to shrinkage. Regarding to shrinkage, the research will investigate the effect of water cooling on the shrinkage of the product’s size in the injection molding process of making acetabular cup. The work begins with the manufacture of molds, then two injections of liquid polypropylene are carried out into the mold. The first injection is for mold without cooling and the second with cooling. The resulting shrinkage is then compared. The shrinkage measurement of the outer part of the product is taken from three directions, namely the product’s height, the product’s outer diameter in the direction of y axis, and the outer diameter of the product in the direction of z axis. For the interior of the product with a half-ball shape, shrinkage measurements are carried out by measuring the average radius. Test result shows that shrinkage in injection molding testing with cooling is lower than injection molding testing without cooling. The average shrinkage of the product’s height on the test with cooling is 1.224%, while the test without cooling is 1.591%. The average shrinkage of the outer diameter in the direction of y axis on the test with cooling is 1.857%, while the test without cooling is 2.32%. The average shrinkage of the outer diameter in z axis on the test with cooling is 1.83%, while the test without cooling is 2.369%. Measurement the average shrinkage of the product’s radius is also obtained the similar trend. The test with cooling obtains the average shrinkage of the product’s radius of 0.825%, while the test without cooling is 1.267%.

Plastic product development requires dimensional accuracy in the product. One method to improve the accuracy of dimension is by making a mold that has a uniform cooling channel following the contour of the cavity, so that the direction of product shrinkage on cooling cycle can be uneven. The existing solid-type mold has several limitations on the cooling channel system. Meanwhile, products with complicated shapes mostly require cooling channel that follows the shape of the cavity (conformal). Type of conformal cooling channels can be made by the method of manufacturing each layer laminate plate arranged with adhesive into a single unit (laminated steel tooling) and the method of using a resin molding mixed with metal powder in which there is a pipe that follows the shape of the cavity (soft tooling). The present study compares the shrinkage of plastic products made from three types of mold, namely: a solid mold with straight cooling channel, laminated steel tooling with conformal cooling channel, and soft tooling with conformal cooling channel. Analysis of shrinkage measurement products includes high direction and inside diameter and outside diameter of elongated cylindrical products. Three types of mold were made, namely mold with a straight cooling channel, laminated steel tooling mold with conformal channel, and soft tooling mold with conformal channel. Three specimens were made from each mold. Plastic material for injection was Polypropylene. The volume of cooling channels between the straight-type channel and conformal was set equal. Data were collected after the injected products were stored for 24 hours. The results show that the percentage of both shrinkage lamination conformal cooling system and soft tooling is smaller when compared to that of a straight cooling system. Moreover, the shrinkage difference of diameter dimension on the X axis and Y axis is insignificant. It proves that the lamination conformal cooling systems and soft tooling are more optimal in controlling the shrinkage dimensions of the product.

Penelitian ini bertujuan untuk mengetahui kualitas bahan yang digunakan pada empat merk bearing (SKF, FMB, NKK, dan JAL) berdasarkan data-data pengujian sifat- sifat mekanik serta struktur intern (struktur mikro) pada benda uji tersebut dan dapat membandingkan ketahanan dan kekuatan keempat merk bearing tersebut berdasarkan analisis pengujian terhadap kegunaannya. Pengujian yang dilakukan meliputi pengujian kekerasan menggunakan alat Micro Vickers Hardness Tester, pengamatan struktur mikro menggunakan alat Olympus Metallurgical Microscope dan Olympus Phtomicrographics Systems, serta pengujian kekasaran permukaan menggunakan alat Surfcorder. Pengujian kekerasan maupun struktur mikro dilakukan pada bagian cincin luar bantalan (outer bearing) dan ball bearing. Sedangkan pengujian kekasaran permukaan hanya pada bagian outer bearing. Setelah dilakukan semua pengujian dapat disimpulkan bahwa berdasarkan kekuatan, kekerasan (ketahanan aus) serta kekasaran permukaan pada bagian outer bearing dan ball bearing maka merk yang memenuhi kualitas optimum adalah merk FMB karena sudah mencukupi dengan parameter kerja bantalan sehingga membuat umur pakai lebih panjang pada aspek penggunaan yang sama. Kata kunci: bearing, kekerasan, struktur mikro, kekasaran permukaan ABSTRACT This study aims to determine the quality of materials used in four bearing brands (SKF, FMB, NKK, and JAL) based on data testing of mechanical properties as well as internal structure (micro structure) on the specimens and can compare the endurance and the strength of the four brands bearings based on the test analysis of its usefulness. The tests include hardness testing using the Micro Vickers Hardness Tester tool, microstructure observation using Olympus Metallurgical Microscope and Olympus Phtomicrographics Systems, and surface roughness testing using Surfcorder tool. Hardness testing and microstructure are performed on outer bearing and ball bearing parts. While the surface roughness testing only on the outer bearing. After all tests, it can be concluded that based on strength, hardness (wear resistance) and surface roughness on outer bearing and ball bearings, the brand that meets the optimum quality is the FMB brand because it is sufficient with the bearing working parameters that make longer life on the same aspect of use. Keywords: bearing, strengthness, microstructure, surface roughness

In this work, a laminated structure of Cr-Ni coating was prepared using electroplating on carbon steel substrates. Two baths of chrome and nickel electrolyte solutions were prepared to deposit laminated Cr and Ni layers. Chrome was firstly plated on a steel substrate in constant routes whereas nickel was subsequently electroplated on the Cr coating using varied plating times. The effect of Ni plating time on the thickness, hardness and wear specific of the Ni layer was investigated. The results show that an increase of plating times increased the thickness and hardness of the Ni layer, but reduced the wear specific. This study showed that Ni can be a potential candidate as a material replacement for chromium plating maintenance.

Hard chromium coatings has long been considered as the most used electrodeposited coating in several industrial applications such as in petrochemistry, oil and gas industries. When hard coatings used in fastener components, the sliding contact during fastening operation produces high tensile stresses on the surface which can generate microcracks. For component used in high oxidation and corrosion environment, deep cracks cannot be tolerated. In this work, a laminated structure of Cr-Cu coating was prepared using electroplating on carbon steel substrates. Two baths of chrome and copper electrolyte solutions were prepared to deposit Cr as the first layer and Cu as the second layer. The effect of current voltages on the thickness, hardness and specific wear rate of the Cu layer was investigated. The results show that an increase of the current voltages increased the thickness and hardness of the Cu layer, but reduced the specific wear rate. This study showed that the use of Cu can be a potential candidate as a laminated structure Cr-Cu for chromium plating.Hard chromium coatings has long been considered as the most used electrodeposited coating in several industrial applications such as in petrochemistry, oil and gas industries. When hard coatings used in fastener components, the sliding contact during fastening operation produces high tensile stresses on the surface which can generate microcracks. For component used in high oxidation and corrosion environment, deep cracks cannot be tolerated. In this work, a laminated structure of Cr-Cu coating was prepared using electroplating on carbon steel substrates. Two baths of chrome and copper electrolyte solutions were prepared to deposit Cr as the first layer and Cu as the second layer. The effect of current voltages on the thickness, hardness and specific wear rate of the Cu layer was investigated. The results show that an increase of the current voltages increased the thickness and hardness of the Cu layer, but reduced the specific wear rate. This study showed that the use of Cu can be a potential candidate as...