Hasil Pencarian  ::  Simpan CSV :: Kembali

"Aluminum alloys, such as A6061-T6, are widely used in engineering components. However, detailed knowledge is needed to understand the way they respond to a fracture due to mechanical loading. Fractures occur in the structural component from crack propagation, and it is important to understand the mixed mode fracture behavior of crack growth. In this research, mixed mode fracture testing was conducted on the aluminum alloy A6061-T6 by employing a compact tension shear specimen. Crack growth behavior was investigated by applying a quasi-static loading at a constant cross-head speed using a Servopulser universal testing machine. The crack growths were observed by a Keyence digital microscope, and the critical stress intensity factors of the material were examined. Results showed that the shear type of crack initiation preceded the opening-type fracture. The dimple-type fracture on the fracture surface occurred under mode I and mixed mode with a loading angle of about 60o and 75o, respectively. The transition of crack initiation behavior from the opening-type fracture to the shear-type fracture occurred at a loading angle from 15o to 30o. The experimental data followed the maximum hoop stress criterion under mode I and mixed mode at a loading angle 60o and 75o, respectively, for the compact tension shear specimen. Crack propagation behavior with three small holes occurring in a zigzag pattern ahead of the crack tip showed that crack initiation and propagation occurred only in the opening-type fracture. The experimental data followed the maximum hoop stress criterion under mode I and mixed mode with a lower mode II component at a loading angle of 75o. When the small holes occured inline, there were two types of fractures occurring: an opening fracture at crack initiation and then crack propagation caused by shear fracture."

"The 7075 aluminum alloy (a typical Al–Zn–Mg–Cu alloy) is one of the most important engineering alloys. It is mainly used in the automotive industry, in transport and aeronautics, due to its excellent strength/weight ratio. The purpose of the present research is to model the behavior of 7075 aluminum alloy and to build an experimental database to identify the model parameters. Firstly, the paper presents an experimental device of simple tensile tests and the studied material on 7075 aluminum alloy. Thus, uniaxial tensile tests are carried out in three loading directions relative to the rolling direction. From experimental hardening curves and Lankford coefficients, the mechanical properties are extracted, particularly the various fractures owing to pronounced anisotropy relating to the material. Secondly, plastic anisotropy is then modeled using the identification strategy which depends on yield criteria, hardening and evolution laws. By smoothing experimental hardening curves in the tensile tests, a selection is made in order to choose the most appropriate hardening law for the identification of the studied material. Finally, a comparison with experimental data shows that the behavior model can successfully describe the anisotropy of the Lankford coefficient."

"Aluminum alloy is one of the materials found in many applications, especially for electrical conductor materials. AlZrCe alloy reinforced by Al2O3 nanoparticles with Mg addition is proposed as one of the alternative materials to replace Aluminum Conductor Steel Reinforced (ACSR) as an aluminum conductor. Aluminum alloy Al-0.12%Zr-0.15%Ce as a master alloy was added with various weights of magnesium (Mg) from 2 to 5 wt% and was reinforced with 1.2% volume fraction of Al2O3 nanoparticles with particle sizes less than 80 nm. The molten metal matrix was blended with the reinforcement by a stirrer with a rotational speed of 500 rpm at a temperature of 750oC in an argon gas environment and casted by gravity casting. The objective of this research was to investigate the effect of magnesium on microstructural changes, electrical conductivity, and mechanical properties, such as tensile strength and hardness of the composites. The microstructure observation results showed that the greater the Mg content in composites up to 5%, the smaller the grain size of the composite matrix, wherein the grain size of the composite without Mg is 28 ?m, while the grain size of the composite with Mg of 2%, 3% and 5% are 27 ?m, 17 ?m and 9 ?m respectively. Similarly, tensile strength and hardness increased with increasing levels of Mg to 5% where the addition of 5% Mg, the tensile strength increased from 106 to 204 MPa and hardness increased from 30 to 68 BHN. In contrast, the electrical conductivity sharply decreased, due to the addition of Mg in the composite with a gradient of reduction, to 2.74% IACS (International Annealed Copper Standard) for every increasing 1% Mg. In which the electrical conductivity of the composite without Mg is 55.1% IACS and after adding 5 wt% Mg, it decreased to 41.3% IACS."

"Aluminum magnesium seri 5083 H112 banyak diaplikasikan untuk industri perkapalan. Hal tersebut dikarenakan aluminum memiliki kekuatan spesifik yang tinggi serta ketahanan korosi yang baik. Namun pada proses penyambungan berupa pengelasan banyak terjadi permasalahan berupa porositas serta menurunnya sifat mekanis terutama daerah terpengaruh panas. Mengacu kepada pengecoran, pemberian getaran pun diaplikasikan pada penelitian pengelasan dengan menggunakan kawat las ER 4043 ini. Sumber getaran berasal dari sebuah meja getar dan diatur getarannya sebesar 30 Hz. Pengujian yang dilakukan yakni pengujian tarik, metalografi, kekerasan mikro, radiografi-visual, dan image analysis. Dari hasil penggetaran nilai kekerasan daerah las dan juga kekuatan tarik meningkat dengan butir dari lasan yang halus pada tiap kecepatan las, 300 mm/menit dan 400 mm/menit. Jumlah porositas pun berkurang dengan dilakukannya penggetaran sebesar 30 Hz.

---

5083 series aluminum magnesium is widely used for marine industrial. It is caused aluminum has high spesific strength and good corrosion resistance. However, at process of welding many of porosity occured in the aluminum and it decrease the mechanical properties especially in HAZ (Heat Affected Zone). At casting process of aluminum, there is one method that can reduce the porosity by giving vibration while casting is performed. So this method is tried to be aplicated at this research which is using ER 4043 as welding wire. Vibration that used is around 30 Hz. Tensile test, metallography, micro hardness, radiography-visual test, and image analysis was used for characterize mechanical properties and porosity content at weldment. The higher average result of tensile test and microhardness for ER 4043 filler weldment for vibrated specimen and porosity content decreased for specimen with welding speed 300 mm/minute and 400 mm/minute. And finer grain has found at microstructure of weldment after welded with vibration."

"Aluminum matrix composite (AMC) menjadi material yang sangat potensial bagi aplikasi industri ketika terdapat kebutuhan untuk mendapatkan kombinasi sifat ringan dengan sifat lainnya yang menunjang seperti kekuatan, kekakuan, ketahanan aus, konduktivitas listrik dan termal tinggi, dan koefisien ekspansi termal rendah. Namun material AMC sangat rentan terkena korosi pitting dan galvanik, yang disebabkan oleh pembentukan pasangan galvanik antara matriks dan penguat, serta terbentuknya mikrostruktur pada interface penguat/matrix. Anodisasi merupakan proses modifikasi permukaan yang potensial untuk meningkatkan ketahanan korosi AMC dengan menghasilkan lapisan oksida berpori. Namun, adanya penguat dalam AMC menghalangi pembentukan lapisan oksida protektif dengan mendorong terbentuknya cavity dan retak mikro. Oleh karena itu, metode cerium sealing digunakan untuk memperbaiki cacat pada lapisan oksida hasil anodisasi, sehingga dapat meningkatkan ketahanan korosi pada lingkungan yang sangat agresif.Penelitian ini bertujuan untuk menganalisis pengaruh parameter proses yakni temperatur dan rapat arus anodisasi terhadap pembentukan lapisan anodik berpori. Anodisasi dilakukan pada tiga temperatur yakni 25°C,0°C dan -25°C dengan variasi rapat arus 25,20 dan 15 mA/cm2. Pengujian kekerasan mikro Vickers digunakan untuk mengetahui sifat mekanik lapisan anodik. Pengamatan struktur mikro menggunakan FE-SEM untuk mengetahui morfologi permukaan dan mengukur ketebalan lapisan anodik.Hasil pengujian menunjukkan penurunan temperatur dan rapat arus akan meningkatkan kekerasan permukaan lapisan anodik alumina dimana kekerasan tertinggi adalah 427 HV yang didapat pada temperatur -25°C dengan rapat arus 15mA/cm2. Penurunan temperatur dan rapat arus juga relatif akan meningkatkan kerapatan dan keseragaman permukaan hasil anodisasi. Serta penurunan temperatur hingga 0°C akan meningkatkan ketebalan lapisan oksida dimana ketebalan terbesar adalah 14,13 μm yang yang didapat pada temperatur 0°C dengan rapat arus 25mA/cm2. Namun ketebalan kembali menurun pada saat diturunkan ke temperatur -25°C.

---

Aluminum matrix composites (AMC) become potential materials for transport application where there is an obvious need for combination of weight saving and other properties, i.e. high specific strength, high specific stiffness, electrical and thermal conductivities, low coefficient of thermal expansion and wear resistance. However they are generally susceptible to corrosion in various environments, due to galvanic reactions between the reinforcements and the matrix, and selective corrosion on the interface due to the formation of new compounds. Anodizing has been considered as a potential modification treatment for enhancing corrosion resistant of AMC by forming porous anodic oxide on the surface area.

This study aims to analyze the influence of anodizing process parameters which is temperature and current density on the formation of porous anodic coating, Anodizing process has been done at three different temperatures which are 25°C,0°C and -25°C with variation of current density at 25,20 and 15 mA/cm2. Vickers microhardness testing was used to determine the mechanical properties of anodic layer. Observation of microstructure using FE-SEM to determine surface morphology and to measure anodic layer thickness.

Test results showed that decreasing temperature and current density would increase surface hardness of aluminium anodic layer. The highest surface hardness was 427 HV which was got by anodizing at temperature -25°C with using 15 mA/cm2 of current density. Decreasing temperature and current density would also relatively increasing density and make the surface smoother and looks more uniform. Decreasing temperature until 0°C would increase thickness of the oxide layer where the highest thickness was 14,13 μm which was got by anodizing at temperature 0°C with using 25 mA/cm2 of current density. But the thickness would decrease when the temperature was decreased to -25°C."

"Paduan aluminium silikon banyak digunakan dalam berbagai aplikasi industri, khususnya industri otomotif. Namun, kehadiran unsur besi dapat menyebabkan terbentuknya senyawa intermetalik yang dapat menurunkan sifat mekanis paduan. Modifikasi senyawa intermetalik dapat dilakukan dengan meningkatkan laju pendinginan dan penambahan unsur tertentu, salah satunya logam tanah jarang. Pada penelitian ini, digunakan simultaneous thermal analysis untuk mengamati pengaruh laju pendinginan terhadap pembentukan fasa intermetalik beta pada paduan AlFe7Si dengan penambahan lantanum sebanyak 0,3%, 0,6%, dan 1%. Mikroskop optik juga digunakan untuk mengamati hasil mikrostruktur dari paduan. Hasil menunjukkan bahwa penambahan La yang optimum adalah pada konsentrasi 0,3% dalam mengurangi ukuran fasa intermetalik beta.

---

Aluminium silicon alloys are widely used in several industrial applications, especially in automotive industry. However, the presence of iron could cause the formation of intermetallic compounds which would reduce the mechanical properties of the alloy. Modification of intermetallic compounds can be done by increasing the solidification rate and adding certain elements, for example, rare earth elements. In this study, simultaneous thermal analysis was used to find out the effect of cooling rate on the formation of beta intermetallic phase in AlFe7Si alloy added with lanthanum at 0,3%, 0,6%, and 1%. Optical microscopy was also used to observe the microstructure of this alloy. Results showed that the optimum addition of lanthanum was at 0,3% to reduce the size of beta intermetallic phase."

"Aluminium sebagai bahan konduktor sangatlah luas pengaplikasiannya. Salah satunya adalah untuk kebutuhan kabel transmisi tinggi. Semaikin hari kriteria yang harus dimiliki kabel transmisi ini semakin tinggi, mengingat kebutuhan listrik yang semakin meningkat. Didalam penelitian ini akan dibahas mengenai pembuatan serta pengkarakterisasian material komposit AlZrCe/Al2O3 nano partikel dengan metode pengecoran aduk untuk keperluan kabel transmisi.Di dalam matriks, zirkonium akan menambah ketahanan panas sedangkan cerium akan menjaga konduktivitas listrik agar tidak turun dan diharapakan penambahan partikel Al2O3 akan meningkatkan kekuatan tarik dari komposit ini. Magnesium sebesar 5 wt% ditambahkan sebagai unsur peningkat kemampubasahan antara matriks dan penguat.Didapatkan bahwa penambahan Al2O3 akan meningkatkan kekuatan tarik, menurunkan konduktivitas listrik dan menurunkan koefisien muai panas komposit ini. Titik optimal untuk mendapatkan sifat mekanik listrik dan panas yang paling baik didapatkan pada fraksi volume 1,2% Al2O3. Daerah antarmuka yang didapatkan oleh seluruh sampel pengujian tidaklah baik, sehingga data yang dihasilkan belum bisa optimal dan sesuai dengan harapan.

---

Aluminum as conductor material is very broad applicability. One of them is to demand of high-voltage overhead transmission lines. The requirements that must be owned of high-voltage overhead transmission lines are getting higher these days, because the electric needs are increasing. In this research will be investigated about fabrication and characterization AlZrCe/Al2O3(np) using stir casting process for overhead cable transmission.

In the matrix, zirconium will be increase heat resistance, cerium will keep the value of electrical conductivity in order not to decrease and the addition of Al2O3 particles is expected to increase the tensile strength of the composite. Magnesium 5 wt% was adding as wettability agent.

The results showed that the addition of Al2O3 will increase the tensile strength, decrease electrical conductivity and decrease coefficient thermal expansion of this composite. The optimal value for get the best of mechanical, electrical and thermal properties is obtained at 1.2% Al2O3 volume fraction. Interface areas obtained by the entire sample testing is not good, so the resulting data can not be optimal and appropriate expectations."

"The Aluminum 7075 (Al 7075) alloy is a precipitation hardening material instead of a strain hardening material. These mechanical properties are of a particular microstructure obtained by thermo-mechanical treatments. Among other things, this is a complicated microstructure which is responsible for the mechanical performance. The evolution of the mechanical properties of aluminum alloys is dependent on aging time parameters after heat treatment. In this study, the material has undergone a tempering heat treatment followed by a series of tensile tests. The experimental data (tensile curves in three directions during maturation time) is used to describe the evolution of the mechanical characteristics in terms of loading directions and maturation time, denoted respectively as: ? and t. The tensile curves are the source of data to begin the problem of identifying the behavior law of studied material using Barlat’s model and Hollomon’s isotropic hardening law. Thus, from the identified parameters (anisotropy coefficients and hardening coefficients), the evolution of the Lankford coefficient, deformation rate and load surfaces during the maturation time for three load directions (0°: rolling direction, 45° and 90°) are described. This study allows optimizing the response of the aluminum alloy to plastic strains, resulting from forming processes measured against the best time during maturation and the best load direction."

"Penghalus butir sering diaplikasikan pada pengecoran aluminium karena mampu meningkatkan kualitas dan mengurangi reject. Salah satu metode pengecoran yang sering digunakan untuk menghasilkan produk aluminium adalah low pressure die casting (LPDC). Namun, siklus LPDC yang mencapai 4 jam dikhawatirkan dapat menyebabkan fading pada penghalus butir. Penelitian ini dimaksudkan untuk mengetahui waktu fading yang terjadi pada penghalus butir Al-5Ti-1B yang ditambahkan pada paduan AC4B hasil LPDC. Fading dapat diamati melalui perubahan kekerasan, kekuatan tarik, struktur mikro serta tingkat kegagalan bocor paduan aluminium AC4B.Pada penelitian ini ditunjukan bahwa dengan semakin lamanya waktu tahan, maka kekerasan dan kekuatan tarik akan menurun, sedangkan keuletan dan lebar secondary dendrite arm spacing (SDAS) pada foto mikro akan meningkat. Penelitian ini juga menunjukan bahwa fading sudah terjadi antara jam ke 0 dan jam ke 1. Selain itu, pengamatan struktur mikro paduan AC4B dengan menggunakan Scanning Electron Microscopy (SEM) dan Energy Dispersive X-RaY Analysis (EDAX) menunjukan keberadaan titanium pada paduan sebagai indikasi dari adanya partikel penghalus butir.

---

Grain refiner is usually applied for aluminum casting to improve quality and reduce rejection. One of casting methods that commonly used to produce aluminum is low pressure die casting (LPDC). One cycle of production of LPDC with ~450 kg capacity may take up 4 hours. Therefore, using grain refiner in LPDC process might cause fading. Aim of this research is to understand the fading time of Al-5Ti-1B grain refiner during LPDC. Fading was observed through the changes of hardness, tensile strength and microstructure. Percentage of leakage in the trial of AC4B cylinder head production was also evaluated.

The results show that the longer the holding time, the lower hardness and the tensile strength of AC4B alloy. On the other hand, the longer the holding time, the higher the ductility & secondary dendrite arm spacing (SDAS). This indicates that fading had occurred before 1 hour. In addition; microstructure observation by using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDAX) shows the presence of titanium in the alloy which indicates that titanium may act as the nucleant for solidification process."