58 research outputs found
IDENTIFIKASI PERUBAHAN POLA CURAH HUJAN MELALUI PERIODOGRAM STANDAR
Rainfall is time series data that has seasonal pattern, usually period 12. The pattern of rainfall seasonal itself often changes. In this paper, the pattern of rainfall will identify by Periodogram Analysis. We use Time series data from one of city in west Java province. By this analysis, it is proved that the pattern of rainfall has been change. Computation itself, we use macro of Open Source Software R (OSSR).  
Pengaruh Prestrain Bertingkat Terhadap Kekerasan Dan Kekuatan Tarik Baja Karbon Sedang
Prestrain adalah suatu gejala deformasi plastis yang terjadi pada material logam, dimana material yang mengalami beban tarik dengan besar tegangan yang terjadi di atas tegangan luluh (syield) dari material logam tersebut. Efek prestrain akan meningkatkan tegangan luluh dan tegangan tarik material. Tegangan tarik dapat meningkat karena tegangan yang dibutuhkan untuk menimbulkan deformasi plastis ditingkatkan dengan prestrain. Regangan awal yang diberikan terhadap material akan mengakibatkan gerakan dislokasi sehingga menyebabkan pengerasan-regang. Pengerasan-regang banyak digunakan untuk mengeraskan logam atau paduan yang tidak bereaksi terhadap perlakuan panas.Material yang digunakan yaitu baja karbon sedang. Setelah material dibentuk, material tersebut di uji tarik sehingga didapat grafik stress – strain dan load – displacement. Dari grafik tersebut dapat dicari nilai prestrain 3 %, 5 %, 7%, dan 6 %, 10 %, 14 %. Spesimen dipasang pada alat uji dan dijepit sehingga spesimen tidak bergeser pada saat pemberian beban tarik. Pada pengujian prestrain sekali diukur pada prestrain 3%, 5 %, 7 % dan 6 %, 10 %, 14 %. Setelah itu dibiarkan selama 1 hari, kemudian dilakukan pengujian tarik. Dari pengujian tarik ini akan didapatkan tegangan-regangan sehingga diperoleh data-data sy (MPa), sult (MPa), dan ε (%). Nilai uji tarik material sult akan dapat diketahui dengan melihat kertas grafik dari hasil pengujian spesimen. Sedangkan untuk prestrain dua kali diukur pada prestrain 3%, 5 %, 7 %. Setelah itu dibiarkan sampai setengah hari, kemudian di prestrain 3%, 5 %, 7 %. Selanjutnya dibiarkan sampai hari besoknya, kemudian dilakukan pengujian tarik. Dari pengujian tarik ini akan didapatkan tegangan-regangan sehingga diperoleh data-data sy (MPa), sult (MPa), dan ε (%).Hasil pengujian yang didapatkan untuk spesimen yang diberi perlakuan prestrain, mengalami peningkatan nilai kekerasan dan kekuatan tariknya. Peningkatan nilai kekuatan tarik tertinggi terjadi pada prestrain 14 % sekali, sebesar 669,57 MPa (8,20%).sedangkan yang terendah terjadi pada prestrain 3 % sekali, sebesar 626,89 MPa(1,30%)
Investigasi Sifat Mekanik Material Komposit Yang Terbuat Dari Pemanfaatan Limbah Batubara Dengan Matrik Resin Poliester Tak Jenuh
Limbah batubara yang dihasilkan oleh sisa pembakaran di industri yang menggunakan boiler belum termanfaatkan secara maksimal untuk menjadi bahan yang lebih bernilai ekonomi, Pada saat ini ada beberapa industri semen yang memanfaatkan hasil lebih batubara sebagai campuran semen yang dikenal dengan istilah semen komposit. Pada penelitian ini mencoba memanfaatkan limbah batubara untuk alternatif pembuatan bahan komposit yang lain yang merupakan campuran bahan resin dan limbah batubara. Hasil bahan komposit sebelum dimanfaatkan untuk aplikasi yang lain diuji sifat mekaniknya untuk mendapatkan komposisi yang terbaik dari campuran resin dan limbah batubara. Pengujain mekanik yang dilakukan adalah uji tarik, uji bending dan uji kekerasan. Dari hasil pengujian mekanik yang dilakukan didapatkan komposisi campuaran yang terbaik antara limbah batu bara dan resin adalah pada komposisi 40 % : 60%. Hasil kekuatan tarik terbesar didapatkan 10,27 N/mm2, kekuatan bending terbesar 16,67 N/mm2 dan kekerasan tertinggi adalah 60, 4 HRL. Dari hasil distribusi uji kekerasan komposisi antara limbah batu bara dan resin pada campuran 40 % : 60% terlihat lebih merata dibandingkan komposisi yang lain
PERBANDINGAN MEKANISME DATA HILANG PADA MODEL NORMAL
Data hilang merupakan sutu fenomena yang umum terjadi dalam penelitian survei atau experimental, berdasarkan fakta tersebut berbagai metode statistika dikembangkan untuk mengatasinya. Pada makalah ini akan diteliti perbandingan nilai taksiran EM (Expectation and Maximization) algoritma untuk mekanisme data hilang Missing at Random (MAR ), Missing completely at random (MCAR) dan Missing Not at Random (MNAR).
Kata kunci : Data hilang, EM Algoritma, Model normal, Mekanisme data hilan
Pengaruh Kedalaman Alur Back Chipping Pada Pengelasan Listrik SMAW Baja Karbon Sedang AISI 1045 Terhadap Uji Kekuatan Tarik
Medium carbon steel can be assembled in various ways, one of them by welding. On the implementation of welding using SMAW welding type which is one method of welding is used widely in construction grafting techniques. In welding, there\u27s common defects such as imperfections of root penetration, hardened and cracked. Back chipping or welding opponent needs to be done to avoid or fix things that often occur in the root weld. SMAW welding is one method which is widely used in construction grafting techniques. This study aims to determine the different test results with the depth of groove weld seam treatment chipping back to the tensile strength test also to determine micro structure. The depth of groove seam using a variation of 2 mm, 3 mm and 4 mm, then the welding results of each treatment were divided into three tensile test specimens and one photo micro specimen. Upon completion of the test specimens and then tensile test performed and photo micro to acknlowledge changes in mechanical properties. From the testing that has been done, the result from tensile strength at back chipping welding with 3mm depth is higher than treated back chipping welding with 2mm and 4 mm depth. The largest maximum tensile strength were found in the back chipping welding groove with 3mm depth is 683.3 MPa, while the untreated back chipping weld the largest maximum tensile strength is 591.7 MPa. Microstructure of root steel welding was welded without back chipping has dominant ferrite grain area
Pengaruh Komposisi Deposit Nacl/na 2 So Terhadap Korosi Temperatur Tinggi Baja Aisi 4130 Yang Dilapisi Aluminium 4
Steel AISI 4130 is a combination steelof 1,0 Cr-0,25 Mo-Fe that mostly used for the component heat axchanger and pipe steam boiler. However in a high temperature and contain of corrosive gas like klor and sulfur,the endurance of the corrosion of steel AISI 4130 declines. It is important to do a research for increasing the endurance of the corrosion of the steel AISI 4130 with heated Al layered in the surface of steel AISI 4130 Al layered and oxidized in temperature 750°C during periods 1-49 jam. The calibration of the corrosion is done with the variation of deposit NaCl/Na The finding of the research shows that the existence of deposit NaCl/Na2 SO in the steel Al layered brings a large influence oxidation kinetics steel, it is proven through the largest value of parabolic constants of the steel AISI 4130 with Al layered with the comparison of deposit NaCl/Na4(gr):30/70 is 6,89 × 10-9 g2 cm–4 s–1. Whereas the value of parabolic constants with the comparison of deposit (gr): 100/0 is 2,71 × 10 -9 g2 cm–4 s–1, 50/50 is 6,15 × 10 -9 g2 cm–4 s–12 SO24SO4 , 70/30 is 2,97 × 10 g2 cm –4 s–1 and 0/100 is around 2,60 × 10 -9 g 2 cm –4s–1. The destruction of the protective layer Al in the aluminide layer is caused by the existence of klor dan sulfur from the deposit NaCl/Na2SO4 thattriggersthe growthofiron-rich ovide (FeO)
Analisis Uji Ketahanan Lelah Baja Karbon Sedang Aisi 1045 Dengan Heat Treatment (Quenching) Dengan Menggunakan Alat Rotary Bending
Fatigue is the one of the main cause from of the material failure. The main of cause failure 90 % caused fatigue. Fatigue is material sructure process changes that is caused by repeatly load (stress or shear) in a long period of time so it occured crack or break. The reason of this research is to analyze of the fatigue strength medium carbon steel type AISI 1045 with variaton of shaft rotation on rotary bending machine. Fatigue test applied on medium carbon steel type AISI 1045 without heat treatment. This research was conducted with variation of shaft rotation 2880 rpm and continued with load variation 20%, 30%, 40%, 50% and 60 % from material UTS. Specimen that used according ASTM E466 spesimen made by lathe machine. Fatigue test is using by rotary bending machine type fatigue test machine
Effect of Slab Thickness on Weld Distortion Results in Medium Carbon Steel AISI 1045 by SMAW Method
This research aimed to investigate the effect of width plate variation to distortion caused by welding in AISI 1045 light steel alloy plate. This kinds of steel is formable by heat treatment and often for making mechanical component use. Sometimes repairing mechanical component was done by welding. The deformation that occurred by welding are caused by distortion. Distortion is shape transformation proccess of welding result which caused by unbalance between expanding metal while heating and shrink while colding.This research takes places in Bureau of Work and Training (BLK) Bandar Lampung, for making the test specimen and distortion measurement, while the hardness test and microstructure test held in Material Laboratory Lampung University. Before testing the specimen, first of all the steel must be welded well, using Shielded Metal Arc Welding (SMAW) method. The electrode which used for welding is E 6013 RB 26, while the joint are V form with 80 A electric current. The welding region that will be the sample data test are base metal, HAZ, and weld metal for hardness test and microstructure test. The variation of plate width are 2, 5, 8 mm.From the result of testing materials, we can make some conclution which is, the largest distortion level experienced by plate occurred in 8 mm width of plate, while the largest hardness number experienced by plate occurred in base metal region with 57,5 HRC number. Although, the 8 mm width of plate is the most thick of all specimen, the hardness number in HAZ refgion has the smallest number of hardness
Karakterisasi Sifat Mekanik Dan Struktur Mikro Baja Carbon Rendah Untuk Cane Cutter Blade Pada PT Gunung Madu Plantation
Cane cutter blade (blade chopper cane), which is a tool used for chopping cane. This tool acts as a cane crusher, made of low steel carbon. Constraints that occur on Cane Cutter Blade is a high wear rate, thus disrupting the productivity of the industry. The company handles this problem by providing a coating on a cane cutter blade, only in this way is still considered very less effective at. low steel carbon relatively low carbon steel.Characterization of the mechanical properties and the microstructure of low steel carbon with hardness testing and tensile testing, while the micro picture of choice to see the results of the condition of the microstructure after a heat treatment with water as cooling media
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