Eddy S. Siradj

Development of Steel Wire Rope – Reinforced Aluminium Composite for Armour Material Using the Squeeze Casting Process

Steel wire rope – reinforced aluminium composite - has been developed to improve the ballistic properties and mobility of armour material. Critical to obtaining ballistic resistance is that the materials must be sufficiently hard and strong, especially at the surface where a projectile will first make impact. To obtain this resistance, aluminium alloys can be strengthened by adding Cu and Mg. This research studied the ballistic properties of aluminium composites with varied Cu and Mg content. The matrix used in this study was an Al-7Si master alloy with 0.08-1.03 wt. % Mg and 0.05-3.75 wt. % Cu, both independently and in combination. A high carbon steel wire rope was used as strengthening material. The samples were produced through the squeeze casting process with a pressure of 1 MPa at semi-solid melting temperatures of 590-610 °C. The slab was then rolled for 10 % reduction to increase the hardness. Ballistic testing was performed in accordance with ASTM F1233 by using a 9 mm calibre projectile and 900 direction. Micro structural observation was conducted in the as-cast and ballistic samples, performed with optical microscope and scanning electron microscope (SEM). The results showed that squeeze casting may improve interfacial wettability and reduce void. The increase in Mg resulted in the decline of interfacial voids, but Cu addition tended to increase them. The aluminium armour was able to withstand a 9 mm calibre projectile, although some cracks were visible. The wire rope was not effective in stopping the penetration of a 7.62 mm calibre projectile.

Effect of Equal Channel Angular Pressing and Post Heating on Microstructure and Hardness of Cu-Zn 70/30

Severe plastic deformation (SPD) using various pass number of Equal Channel Angular Pressing (ECAP) experiment and followed heating at 400°C has been done for rod brass Cu-Zn 70/30 to investigate the operation on microstructure and hardness of the alloy. Optical microscopy and SEM are used to examine the microstructure change. Mechanical testing such as macro and micro hardness test is used in order to examine the change of mechanical properties. The grain structure of the alloy was refined from 34 μm to 2 μm after 4 passes ECAP and increased to 4 μm after post heating. The hardness of the alloy significantly increased from 78 Hv to 235 Hv after 4 passes and decreased to 135 Hv after post heating after ECAP. The microstructure and mechanical properties of the alloy was homogenous after 4 passes ECAP because the strain was found more homogenous.

Effect of Cooling Rate and Nb Composition on Non-Isothermal Austenite Grain Growth Kinetics in Nb-HSLA Steel during Hot Rolling

Abstract. The strength of a final product of steel is affected by its final austenite grain size.Almost applied models for grain growth based on Beck and Sellars equation , which has the isothermal condition assumption; whilst most of the materials processing take place under non-isothermal condition. The purpose of this research is to find the effect of Nb and cooling rate to the austenite grain growth model of HSLA-Nb steel to predict the Austenite grain size after hot rolling process in non-isothermal condition .The two composition of 0.019 and 0.056% Nb of HSLA-Nb was hot-rolled about 0.3-0.4 deformation at a temperature of 900-11000 C, followed by cooling rate of 7-11 0 C/s, in a time period of 25-40 second, and quenched by using water jetspray. Austenite final grain size was measured . The work shows that the higher Nb content of steel with higher cooling rate will reduce the final austenite grain size . It was also found that the new non-isothermal austenite grain growth after hot-rolled illustrated as a function of cooling rate,which obtained by modifying the previous established model by a cooling rate parameter 1/Crm, and it was more precision compared to previous grain growth equation.

PENGEMBANGAN METODE EVALUASI KEKUATAN PROFIL BAJA PERSEGI MENGGUNAKAN PEMANFAATAN GABUNGAN TEORI MEKANISME PLASTIS DAN ELASTIS = DEVELOPMENT OF STRENGTH EVALUATION METHOD OF A SQUARE HOLLOW STEEL SECTION USING THE APPLIACATION OF COMBINED THEORIES OF PLASTIC MECHANISMS AND ELASTIC APPROACH

Metode analisis disain yang dikembangkan didalam penelitian ini tidak menggunakan faktor keamanan sehingga dapat digunakan untuk mendisain struktur baja yang mampu mendukung beban kerja dengan berat yang seringan mungkin sehingga diperoleh struktur yang efektif dan efisien dari segi teknis dan ekonomi. Dalam penelitian ini, suatu metode cut-off strength digunakan sebagai dasar untuk memprediksi kekuatan profil baja ringan berpenampang persegi (SHS) akibat interaksi beban tekan memusat dan momen lentur. Metode cut-off strength diilustrasikan dalam bentuk dua kurva beban-defleksi plastis dan elastis, dimana nilai beban diperpotongan kedua kurva tersebut diasumsikan sebagai kekuatan teoritis profil baja SHS terhadap interaksi tekan memusat dan momen lentur. Kurva plastis dibentuk berdasarkan persamaan beban-defleksi yang dikembangkan melalui analisis kesetimbangan energi model mekanisme kerusakan plastis profil baja SHS. Sementara itu, kurva elastis dibentuk berdasarkan persamaan beban-defleksi yang dikembangkan melalui analisis non-linear elastic profil baja SHS dengan mempertimbangkan efek local buckling pada penampang profil yang tertekan. Metode analisis ini diimplementasikan dengan menggunakan perangkat lunak (software) komputer. Untuk mengukur ketelitian model analisis disain yang dikembangkan dalam penelitian ini, hasil prediksi kekuatan profil baja SHS diverifikasi menggunakan data kekuatan aktual yang dihasilkan melalui pengujian sejumlah profil baja SHS akibat interaksi beban tekan memusat dan momen lentur sampai rusak. Hasil verifikasi menunjukkan bahwa rasio data prediksi analitis dan eksperimental masih tersebar dalam batas-batas toleransi yang umum digunakan yaitu ± 20 %.

Pengaruh Substitusi Ion Mn dan Ion Co Serta Ion Ti pada Pembentukan Fasa dan Sifat Magnetik Barium Hexaferrite BaFe9(MnCo)1,5Ti1,5O19 Disintesis Melalui Rute Metallurgi Serbuk

ABSTRACT Barium hexaferrite dengan struktur molekul BaFe12O19 dikenal dengan baik sebagai magnet permanen yang memiliki sifat mekanik dan banyak menyita perhatian peneliti beberapa tahun lalu hingga sekarang. Pada penelitian ini serbuk hexaferrite dihasilkan melalui mekanisme konvensional menggunakan metoda metallurgi serbuk. Struktur kristal serbuk hexaferrite dianalisis menggunakan Difraksi X dengan sumber Co(kα) pada panjang gelombang 1.78896 ˚A sedangkan sifat magnetik material diuji dengan Permeagraph dengan medan magnet luar 1.5 Tesla. Hasil kalkulasi parameter kisi pada magnet konvensional (BaFe12O19) diperoleh hasil a = b = 5,894 A dan c = 23,210A, sedangkan pada fasa tersubstitusi memiliki perubahan pada kisaran a = b = 5,893 A – 5,899A dengan nilai c pada kisaran 23,328A sampai dengan 23.346A. Dengan adanya substitusi parsial ion Fe +3 dengan Ion Mn+2 , ion Co+2 dan ion Ti +4 terjadi penurunan sifat magnetik terutama pada koersivitas magnetik pada dari 125 kA/m (konvensional) menjadi dibawah 5 kA/m pada material tersubstitusi. Kata kunci: magnet ferrite, mikrostruktur, koersivitas, remanen, saturasi magnetik ABSTRAK Barium ferrite with hexagonal molecular BaFe12O19 is well-known for its high performance permanent magnetic and good mechanical properties and attracted attention of researchers for a long time. The hexaferrite powders were produced according to a conventional ceramic process with powder metallurgy method. Moreover, the powders were analyzed by X-ray diffraction, to detect the presence of secondary phases. The magnetic properties of the samples were measured at room temperature using Permeagraph with a maximum applied field of 1.5 T. The calculation of the lattice parameter on conventional magnets (BaFe12O19) results a = b = 5,894 A and c = 23,210 A, while the substituted phase has a range value of a = b between 5,893 A to 5,899 A, and c lattice parameter value is in the range of 23,328 ˚A to 23,346 A. With the partial substitution of Fe +3 ions by Mn+2 ions, ion Co+2 and Ti +4 ion magnetic properties decrease primarily on the magnetic coercivity from 125 kA / m (conventional) to ~ 5 kA /m in the substituted materials. Keywords: ferrite magnetic, microstructure, coersivity, remanent, magnetic saturation

Developing a Strength Analytical Method of a Thin-Walled Steel SHS Beam by Combine Theory of Plastic Mechanisms and Non-Linear Elastic

The research objective is focused in developing a strength analytical method of a thin-walled steel square pipe (Square Hollow Section/SHS) affected by the interaction of concentrated-compressive load and bending moment. This strength analytical method is based on two different approaches, namely plastic mechanisms and elastic theories. This is called the method of cut-off strength. In this research, it has also been carried out to test the strength of the investigated beam under the interaction of concentrated-compressive load and bending moment. In order to essess the accuracy of the analytical method developed, estimate data of this method is also verified by comparing it to the actual one measured from experiments. The verification indicated that the estimated data, on average, deviates from the experimental one by 5 %.

SKD 61 Material Surface Treatment with Electric Discharge Machining Using Cu, CuCr & Graphite Electrodes and Dielectric Fluid Jatrophacurcas

The emergence of white layer in each process of Electric Discharge Machining (EDM) becomes the focus of attention of the experts. It is harder than the base metal would be advantageous to withstand friction engine components, such as the plastic molding industry. From various studies it has been reported that the increase in the value of hardness of white layer either due to migration of the electrode material and dielectric fluid to the white layer. This paper discusses the influence of electrodes Cu, CuCr and graphite as well as jatrophacurcas dielectric fluid to the surface of the material SKD 61, microhardness of the white layer, Tool Wear Rate (TWR) of Material Removal Rate (MRR), Surface roughness (Ra) and the microstructure. Initial studies conducted are the transesterification and characterization of jatrophacurcas to determine the dielectric strength and the content of metal elements. Furthermore, the EDM testing is done to dies steel of SKD 61 using the electrodes of Cu, CuCr and Graphite. The use of jatrophacurcas yield the best MRR when using Graphite electrodes followed Cu last CuCr. While the smallest TWR produced by Cu electrode, CuCr and then the highest is Graphite. The relative wear which is the ratio TWR with MRR, for the three types of electrodes is always great at a small current then decreases and then tends to be stable with the increase of electric current. Jatrophacurcas for the three types of electrodes provide higher TWR than kerosene. This means that migration of materials is beneficial because larger material, but in terms of the geometric accuracy of the product can lead to decreasing of dimensional tolerances. Vickers hardness values of white layer is achieved by CuCr electrodes, Graphite lowest. Microstructural observation results of EDM white layer using graphite electrodes produce a more uniform thickness than the white layer using Cu and CuCr electrodes. The conclusion of this study that jatrophacurcas can be used as a dielectric fluid in EDM process, because electrode wear during EDM process is relatively high compared with kerosene that is mean more profitable in the surface treatment process of dies steel of SKD 61.

Deformation Behaviour of Silicon Carbide Reinforced Al-7Si Composite after Balistic Impacts

The deformation after ballistic impact loading of silicon carbide reinforced aluminium alloy composite is investigated in this research. The composite consists of 10 % volume fraction of silicon carbide particulate in a matrix of Al-7Si-Mg-Zn alloy and were produced through the squeeze casting process with a pressure of 1 MPa at semi-solid melting temperatures of 590-610 °C. The mechanical property of the composite was examined with hardness test. The ballistic tests were performed with two types of projectiles, 9 mm and 5.56 mm calibre of projectiles. Furthermore the deformed surfaces were studied with optical microscopy. During ballistic testing, the 9 mm projectile did not pierce the composite plate although the test resulted in significant cracks on the backside of the plate. The cross section observation of the plate showed ductile deformation in the matrix and silicon carbide particulates give significant rule in withstanding the penetration of the projectile. By contrast, the 5.56 mm projectile pierced through the composite and caused a brittle fracture of the matrix.

Effect of Rolling Direction to the Strength of a Thin-Walled Steel SHS Beam under Concentrated-Compressive Load and Bending Moment

In this research, it has been carried out the development of a strength analytical method of a thin-walled steel square pipe (Square Hollow Section/SHS) affected by the interaction of concentrated-compressive load and bending moment then it verified by experimental approach. The experimental approach was consisted of measuring a basic material property and the strength of the investigated SHS pipe. The basic material property identified parallel to rolling direction (0o) and perpendicular to rolling direction (90o). The analytical data obtained from cut-off strength method is generally scattered within the acceptable limits of ± 20 % and tends to be in unconservative region. The actual data measured from experiments shows that SHS beam with t = 0.6 mm and longitudinal axis parallel to the rolling direction of base material has higher strength compared to the one of the SHS beam with t= 0.6 mm and longitudinal axis perpendicular to the rolling direction, meanwhile the SHS beam with t= 1.2 mm is tends to be equal. This means that the rolling direction of base material can be considered to be a parameter in the strength design of a thin-walled SHS beam

Effect of Hydrogen Charging on Microstructure Morphology of Warm Rolled Low Carbon Steel

Warm rolled deformation is one of deformation technique to improve the strength of steels through the refining grain size of ferritic microstructure. In application, low carbon steel which used in structural industry need some protection against corrosion attack, cathodic protection is usually applied combining with coating. Cathodic protection creates reduction reaction which produces hydrogen, and the hydrogen atom may diffuse into the crystal lattice lead to the Hydrogen Induced Cracking. The present study is to observe the morphology of microstructure influenced by hydrogen charging as the source of hydrogen which attacks the steel surface, and observed by Optical Microscopy and Scanning Electron Microscopy. After warm rolling of 650oC and 35% deformation, ferrite grain size is smaller than bulk material and the hardness value increasing. After tensile test of hydrogen charged steel found the ductile fracture, it means the smaller the ferrite grains size, the resistance of hydrogen attack is increase.