Degradation of Aluminide Layers During Cyclic Oxidation of Ferritic 430 Stainless Steel

In order to increase the performance of the preferred Ferritic 430 SS for manufacturing automobile and motor-cycle exhaust systems. The aluminizing coating on the surface of bare steel was applied by hot-dipping method in a molten pure aluminum. The high temperature oxidation of the aluminized steel was cyclically studied at 900 °C and 1000 °C in static air. The degradation of intermetallic layers during cyclic oxidation were analyzed by means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The crack perpendicular to the specimen surface rapidly propagated through the FeAl and Fe3Al layers due to a thermal expansion mismatch upon cooling to room temperature. The accumulation of voids generated crack at the interface between the aluminide layer and the steel substrate. Oxygen is allowed to penetrate into the aluminide layer crack, rapidly forming alumina oxide and closing the crack. Some of the aluminide layers peeled off due to this rapid growth. Thus, the protective Al2O3 layer degraded and later, the substrate was oxidized subsequently to form iron-rich oxide (Fe2O3) at 1000 °C

Studi Perilaku Kegagalan Sambungan Las Tipe TConjunctions Pada Baja Karbon Rendah Dengan Pendekatan Experimen Dan Numerik

This research is conducted to investigate failure behavior of welding structure in T-conjunctions type. Welding joint failures were analyzed by both experimental and finite element analysis (2D) approach in terms of stress intensity factor mode I (KI). The stress at the welding zone was strongly influenced by specimen geometries and the ratio of L/h1. The stress intensity factor (SIF) was increased significantly. Whereas, the minimum SIF of specimen #X1 and #Y3 are 58 MPa.√m and 165 MPa.√m, respectively. Failure of welding specimen was more dominated in the zone with the highest stress concentration and also affected by material discontinuity at which the stress was not generated continuously, but localized in any certain area. Specimen without welding did not yield a maximum stress. However, plastic zone formation locally decreases the stress concentration. Discontinuity in the welding specimen does not give rise to plastic stream, thus it will raise the stress concentration at the welding extension region. Discontinuity can be observed by the Von Misses stress pattern at stress welding zone for the welding specimen whereas the specimen without welding was only occurred near the extension zone

Perbandingan Hidrodinamika Flokulator Berbentuk Setengah Lingkaran Dan Persegi Panjang Pada Proses Flokulasi Menggunakan Aliran Melaluimedia Kelereng

Teori Camp & Stein menyebutkan bahwa untuk mendapatkan hasil flokulasi yang baik harus memenuhi nilai Gtd tertentu. Tetapi dalam flokulasi melalui media berbutir dengan nilai Gtd yang relatif lebih rendah dari yang disyaratkan telah didapatkan hasil flokulasi yang baik. Berdasarkan hal tersebut maka diduga ada faktor lain yang berpengaruh pada proses flokulasi menggunakan aliran melalui media berbutir selain Gtd.Penelitian ini bertujuan untuk mengetahui kinerja dari dua buah flokulator dengan media kelereng dalam aplikasinya sebagai flokulator dan mengetahui aspek hidrodinamika yang berpengaruh dalam flokulasi. Flokulator yang digunakan adalah flokulator saluran terbuka berbentuk setengah lingkaran dan flokulator saluran terbuka berbentuk persegi panjang. Variasi debit yang digunakan adalah 1 liter/menit, 1,5 liter/menit, 1,7 liter/menit, 2 liter/menit, dan 2,2 liter/menit. Metode analisis hasil penelitian yang digunakan adalah berupa analisis laboratorium dan analisis perhitungan.Penurunan kekeruhan dengan air baku buatan mencapai lebih dari 98%, dan 94,49% untuk air baku alami. Penurunan kadar organik mencapai 65,23% dan 38,10% untuk penurunan TSS. Angka kehilangan tekan yang terjadi pada flokulator berbentuk setengah lingkaran berkisar antara 0,20 hingga 6,95 cm, dan 0,60 hingga 7,85 cm untuk flokulator berbentuk persegi panjang. Nilai G berkisar antara 33,035 hingga 166,751/detik dan nilai Gtd berkisar antara 306,464 hingga 25304,741. Bilangan Reynolds yang diperoleh berkisar antara 245,392 hingga 708,225. Nilai bilangan Froude untuk kedua flokulator berkisar antara 0,030 hingga 0,064. Angka kecepatan gerusan pada flokulator berbentuk setengah lingkaran berkisar antara 0,026 hingga 0,033 cm/detik, dan antara 0,020 hingga 0,025 cm/detik untuk flokulator berbentuk persegi panjang. Waktu detensi aktual untuk kedua flokulator lebih kecil jika dibandingkan dengan waktu detensi teoritisnya

Efek Shot Peening Terhadap Korosi Retak Tegang (SCC) Baja Karbon Rendah Dalam Lingkungan Air Laut

The aim of this study is to investigate the effect of shot peening on stress corrosion cracking of a low carbon steel in ocean water environment. The dimension of specimens were prepared in accordance with the ASTM G39. The hardness testing was carried out using microvickers with 0,25 kgf load in the longitudinal direction. The corrosion cracking test was immersed into artificial sea water for about 7 months. The test shows that the pitting corrosion is dominantly nucleated at the metal film interface. The biggest pitting corrosion was occurred under the static loading of 70 for the specimens unpeened. The presence of pitting corrosion promotes stress corrosion cracking. The cracking has a intergranular branched morphology which is typical for the chloride cracking of low carbon stee

Pendugaan Potensi Kekeringan Meteorologis terhadap Kebakaran Hutan dan Lahan dengan Metode Indeks Presipitasi Terstandarisasi di Kabupaten Banjar

The potency of meteorological drought estimated by Standardized Precipitation Index can be used to predict the incidence of forest and land fires in Kabupaten Banjar. The aim of this research was to synthesize the relationship rainfall and level of dryness with the occurrence of hotspots, mapping meteorological drought in monthly periods and level of dryness of the method of Standardized Precipitation Index (SPI) and spreading of hotspots in Kabupaten Banjar. This research was conducted in Kabupaten Banjar by using the method of Standardized Precipitation Index to analyze the dryness level in one area. Data used were the processed monthly rainfalls in the period of 2010 – 2015 and the data of hotspots in Kabupaten Banjar, and then the maps for the hotspots and rainfall were created using mapping software. The results showed meteorological drought periods in Kabupaten Banjar happens nearly every year with the lowest period (very dry) occurred in November 2015 with a value of SPI -3.3. To conclude, first, the less rainfall and the low value of SPI will be followed by the increasing incidence of forest and land fires on the marks with the high number of hotspots, the second level of meteorological dryness occurs in January, July and up to November, and the last occurrence of high hotspots occurs in July up to November

Posisi Indonesia pada Kerja Sama Energi Regional dalam Memasuki Era Masyarakat Ekonomi ASEAN Studi Kasus: ASEAN Power Grid

ASEAN Power Grid merupakan sebuah kerja sama interkoneksi listrik ASEAN yang telah diamanatkan pada tahun 1997 di bawah Visi ASEAN 2020. Selain itu, percepatan pembangunan ASEAN Power Grid juga dicantumkan dalam cetak biru Masyarakat Ekonomi ASEAN menuju 2015. ASEAN menyadari bahwa energi memiliki peranan penting dalam medukung aktivitas ekonomi, termasuk listrik. Namun, sampai pada tahun 2015 realisasi pembangunan ASEAN Power Grid masih belum mengalami kemajuan yang signifikan. Sebagai pengguna energi terbesar di ASEAN dan aktivitas ekonomi serta industri yang terus berkembang, kerja sama ASEAN Power Grid ini dapat dimanfaatkan untuk memenuhi kebutuhan pasokan energi dalam memasuki era Masyarakat Ekonomi ASEAN. Di Indonesia belum ada ASEAN Power Grid yang sudah selesai terinterkoneksi, namun proyek interkoneksi listrik tersebut sedang dalam konstruksi sebesar 600 MW yang akan menghubungkan Sumatra dengan Malaysia, dan sebesar 230 MW yang akan menghubungkan Kalimantan dengan Serawak. Adapun interkoneksi yang akan mengubungkan Batam – Singapura, serta Singapura – Sumatera yang masing-masing sebesar 600 MW masih dalam tahap perencanaan. Tujuan dari penelitian ini adalah untuk meninjau kembali posisi Indonesia pada kerja sama enerhi regional demi mempersiapkan diri dalam memasuki era Masyarakat Ekonomi ASEAN. Metode yang digunakan dalam penelitian ini adalah deskriptif kualitatif dengan jenis penelitian studi kasus. Hasil penelitian ini menemukan bahwa Indonesia, melalui HAPUA, telah berupaya dalam melakukan realisasi atas komitmen perwujudan ASEAN Power Grid. Namun, oleh karena adanya kendala, maka realisasi ASEAN Power Grid di Indonesia cenderung bergerak lambat. Adapun pola kerja ASEAN Power Grid, yaitu melibatkan ASEAN sebagai institusi supra nasional, investor sebagai aktor non negara, dan negara anggota ASEAN sebagai aktor negara

Hubungan Cuaca dan Konsentrasi Pm10 (Studi Kasus di Kota Banjarbaru)

This research's aim was to identify the relationship between weather element with PM10 concentration in Banjarbaru both during normal condition and during smoke fog (smog) condition, to study the condition's effect afflicts to weather element and PM10 concentration in ambient air and to determine standard quality concentration PM10's threshold in ambient air during smog condition. The data were 10 minute PM10, humidity, and temperature and daily weather of 2015 that obtained from Banjarbaru Climatology Station meanwhile data of hotspot's in South Kalimantan at 2015 was taken from MODIS satellite of Terra Aqua owned by NOAA. The 10 minutes data has been clustered using K-means method and the daily weather element relationship with PM10 concentration obtained based on regression analysis. When normal conditions, only temperature, and duration of irradiance were significantly has positively correlated with PM10 concentration, air humidity and significant rainfall are negatively correlated, the remain is not significant in effect, while during smog conditions; temperature, duration of irradiation, air pressure, average wind velocity, and maximum significant wind speed are positively correlated, air humidity, and rainfall significantly negatively correlated. Based on the results of K-means clustering analysis of PM10 concentration, there was higher humidity, higher temperature, and PM10 concentrations were below the standard quality threshold under normal conditions while in the case of smog conditions, lower humidity, lower temperature, and PM10 concentrations were above the quality standard threshold. PM10 concentration during smog condition reaches dangerous status/above the standard quality threshold before dry season until late dry season at 02.20 is in the dusk until 12.30 pm

Pemanfaatan Data Satelit Tropical Rainfall Measuring Mission (Trmm) Untuk Pemetaan Zona Agroklimat Oldeman Di Kalimantan Selatan

The irregularity of observation sites distribution and network density, lack data availability and discontinuity are the obstacles to analyzing and producing the information of agroclimate zone in South Kalimantan. TRMM satellite needs to be researched to overcome the limitations of surface observation data. This study intended to validate TRMM 3B43 satellite data with surface rainfall, to produce Oldeman agroclimate zone based on TRMM satellite data and to analyze the agroclimate zone for agricultural resources management. Data validation is done using the statistical method by analyzing the correlation value (r) and RMSE (Root Mean Square Error). The agroclimate zone is classified based on Oldeman climate classification type. The calculation results are mapped spatially using Arc GIS 10.2 software. The validation result of the TRMM satellite and surface rainfall data shows a high correlation value for the monthly average. The value of correlation coefficient is 0,97 and 25 mm for RMSE value. Oldeman agroclimate zone based on TRMM satellite data in south Kalimantan is divided into five climate zones, such as B1, B2, C1, C2, and D1