Pengembangan material komposit berbasis logam pada dunia industri cukup potensial untuk memenuhi akan komponen-komponen permesinan. Dengan adanya perkembangan bahan yang sangat pesat, maka dituntut untuk menghasilkan bahan ringan dan murah yang merupakan persyaratan utama dalam dunia industri pembuatan komponen-komponen mesin. Hal ini memunculkan inovasi baru dalam pembuatan Aluminium Matrix Composite (AMC) yang berbasis matrik Alumunium dengan penguat Silicon Carbon dan Al2O3 partikel. Metode yang digunakan dalam penelitian adalah dengan proses powder metalurgi dan variasi komposisi penguat komposit. Awal proses komposit dibuat dengan variasi komposisi matrik Aluminium dengan penguat SiC+Al2O3 dalam komposit. Komposisi Aliminium : 80% wt dengan variasi penguat 20% wt. Pembuatan material uji dilakukan dengan proses metalurgi serbuk dimana gaya tekan 25 N. Variasi perlakuan waktu sintering adalah 1 jam dan 3 jam pada temperatur 500oC, 550oC dan 600oC. Pengujian karakteristik dilakukan untuk menggetahui sifat fisik dan mekanik komposit. Hasil penelitian adalah dengan penambahan komposisi persen berat SiC dan Alumina (Al2O3) memberikan pengaruh pada sifat fisik dan mekanik komposit. Dimana densitas dan keausan meningkat terjadi pada setiap penambahan Alumina (Al2O3) itu sendiri. Sebaliknya porositas menurun dengan meningkatnya komposisi penguat. Hubungan antara sifat fisik dan mekanik dari masing-masing komposisi penguat SiCw dan Al2O3 pembentuk komposit yang dibuat, memberikan densitas 2.589 gr/cm3 dan keausan yang terjadi 0,005 gr pada perlakuan sintering 600oC dengan waktu tahan 3 jam.
The material of composite hybrid Al / (SiCw + Al2O3) is a mixture of fine aluminium powder as a matrix while Silicon Carbide whiskers (SiCw) and Alumina (Al2O3) as reinforcement. Powder metallurgy method is used to manufacture composites according to the form of test specimens. Testing without treatment and after sintering treatment with temperature parameters and sintering time of 500 and 600°C at holding time 6 hours. This research was conducted to know the properties of thermal conductivity, hardness, density and SEM analysis after sintering process. The results show that the sintering process that has been carried out can provide a percentage increase and affect the composite properties. Improved thermal, hardness and density occurs due to stronger or denser interface bonds between the matrix and reinforcement influenced by increasing sintering temperatures, so sintering processes can affect composites on physical and mechanical properties.
Pack carburizing merupakan suatu proses laku panas untuk memperoleh pengerasan hanya pada bagian permukaan dengan menggunakan media carburizer padat. Dengan memberikan temperatur pemanasan dan waktu penahanan yang tepat diharapkan dapat meningkatkan umur lelah suatu material baja St.42. Metode pada penelitian ini mengunakan pack carburizing padat berupa serbuk, yang dibuat dalam bentuk kotak dan didalamnya diisi serbuk carbon. Penelitian ini membahas tentang pengaruh waktu penahanan dan temperatur pack carburizing terhadap umur lelah baja ST 42 dengan menggunakan variasi temperatur pemanasan adalah : 850, 900 dan 950°C dan waktu penahanan 4, 6 dan 8 jam. Kedua variabel ini diamati pengaruhnya terhadap umur lelah. Berdasarkan hasil penelitian bahwa waktu penahanan dan temperatur pack carburizing berpengaruh nyata terhadap umur lelah, dimana umur lelah tertinggi yaitu pada 993.089 cycle pada temperatur pemanasan 950 °C dan waktu penahanan 8 jam. Umur lelah paling rendah adalah 440.613 cycle terjadi pada temperatur pemanasan 850 °C dan waktu penahanan 4 jam. Pack carburizing is a hot-selling process to obtain only hardening on the surface by using solid carburizer media. Providing proper heating temperature and retention time is expected to increase the fatigue life of a steel material of St.42. The method in this study using a solid pack carburizing of powder, which is made in the form of a box and inside it is filled with carbon powder. This study discusses the effect of detention time and pack carburizing temperature on ST 42 fat age by using variation of heating temperature are: 850, 900 and 950?C and holding time 4, 6 and 8 hours. Both of these variables were observed to influence the fatigue life. Based on the result of research that the holding time and temperature of pack carburizing have a significant effect on fatigue life, where the highest fatigue age is 993,089 cycles at heating temperature 950 ?C and 8 hours of detention time. The lowest fatigue period was 440,613 cycles occurring at a heating temperature of 850 ?C and a 4 hour detention time.
Proses pelapisan krom keras merupakan proses akhir atau tahap penyelesaian pada kebanyakan pembuatan komponen agar tidak cepat aus, seperti pada poros, pasak, ring piston, silinder, bearing dan crank shaf. Dalam bidang industri sifat mekanik yang banyak diperlukan pada logam yang dipergunakan adalah kemampuannya untuk tahan aus dan tahan korosi yang mana kita ketahui logam mempunyai reaksi yang sangat aktif terhadap perubahaan temperatur dan cuaca, maka perlu dilakukan pelapisan sehingga kemungkinan suatu bahan logam terkena korosi bisa dihambat. Bahan spesimen yang di gunakan adalah Baja St 60 (C 0.40%; Mn 7%; Si 0.28%; P+S 0.09%; Fe 98,53%) dengan variasi tegangan listrik: 4, 6, dan 8 volt, untuk variasi waktu elektroplating krom keras 30, 45, dan 60 menit. Pengujian yang dilakukan dengan pengukuran ketebalan lapisan menggunakan skala foto mikro dan menghitung ketebalan lapisan permukaan. Hasil penelitian menunjukkan bahwa semakin tinggi tegangan listrik yang digunakan dan semakin lama waktu proses pelapisan krom keras maka meningkat ketebalan lapisannya. Ketebalan lapisan permukaan yang paling tebal didapatkan pada tegangan 8 volt dengan waktu pelapisan 60 menit dengan ketebalan lapisannya sebesar 89,37 ?m, sedangkan ketebalan lapisan permukaan tipis didapat pada tegangan 4 volt dengan waktu pelapisan 30 menit ketebalan lapisannya sebesar 20,18 ?m. Jadi tegangan listrik dan waktu electroplating dapat mempengaruhi dan memberikan efek terhadap ketebalan lapisan yang terjadi pada Baja St.60. The hard chrome coating process is the final process or completion stage in most parts making so as not to wear out quickly, such as on the shaft, pegs, piston rings, cylinders, bearings and crank shafts. In the industrial field of mechanical properties that are much needed in the metal used is its ability to withstand wear and corrosion resistance which we know metals have a very active reaction to changes in temperature and weather, coating is necessary so that the possibility of a metal being corroded can be inhibited. The specimens used were Baja St 60 (C 0.40%; Mn 7%; Si 0.28%; P + S 0.09%; Fe 98.53%) with variations in electrical voltage: 4, 6 and 8 volts, for time variations hard chrome electroplating 30, 60 and 90 minutes. Tests carried out by measuring the thickness of the layer use a micro photo scale and calculate the thickness of the surface layer. The results showed that the higher the voltage used and the longer the coating process was hard chrome, the thickness of the layer increased. The thickest surface layer thickness was obtained at 8 volts with a coating time of 60 minutes with a layer thickness of 89.37 ?m, while the thickness of the thin surface layer was obtained at a voltage of 4 volts with a coating time of 30 minutes layer thickness of 20.18 ?m. So the electrical voltage and time of electroplating can affect and give effect to the thickness of the coating that occurs in Steel St.60
It has been found out that heat exchangers with longitudinal grooves produce better heat transfer than those without longitudinal grooves. However, up to now, there have been few investigations and applications of longitudinal grooves in relation to heat transfer associated with friction from the annulus of a heat exchanger. The present investigation examined the effects of longitudinal grooves in a double pipe heat exchanger on the characteristics of heat transfer and friction. Longitudinal rectangular grooves were carved into the outer side of a tube at a specified depth (t) and width (l). The effect of the number of longitudinal grooves, Reynolds number (Re), on the thermal and hydraulic performance was evaluated based on the heat exchanger experimental data. A total of four pipes were used: one pipe with 2 grooves, one pipe with 4 grooves, one pipe with 6 grooves and one pipe with 8 grooves. Water, hot and cold, was used as the working fluid. The test was performed with the cold water as the working fluid, with the Reynolds number from about 33 000 to 46 000 in a counter-flow scheme. The result showed that the number of grooves improved the heat transfer and caused a pressure drop. The increase in heat transfer ranged from 1.05 to 1.15, and the pressure loss of the system reached almost 30% as compared with the smooth annulus, the annulus with no groove. The installation of longitudinal grooves in a heat exchanger system enhanced the process of the heat flow through the boundary but provided a compensation for the pressure loss, which was correlated with the friction and pumping power.
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