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Semesta Teknika
Published by Universitas Muhammadiyah Yogyakarta
ISSN : 1411061X     EISSN : 25025481     DOI : https://doi.org/10.18196/st
Core Subject : Engineering,
Engineering
SEMESTA TEKNIKA is a reputable refereed journal devoted to the publication and dissemination of basic and applied research in engineering. SEMESTA TEKNIKA is a forum for publishing high quality papers and references in engineering science and technology. The Journal is published by the Faculty of Engineering, Universitas Muhammadiyah Yogyakarta, INDONESIA. Copyright is by the publisher and the authors. The Journal is issued in electronic form and also issued in printed form as annual volume for the contributors only. The journal contains original research papers, review articles, short notes and letters to the editors. The topics of interest include modeling, experimental, analytical and numerical investigations on the mechanical, physical, chemical and mineralogical properties of material, developing the prototype/instrument, technology and construction process. Topic of management in industry and civil construction is also considered. SEMESTA TEKNIKA receives manuscripts from the contributor written in the Indonesian and English. Manuscripts submitted to the journal for publication must not have been previously published or is under consideration simultaneously by any other publication. Manuscripts submitted to SEMESTA TEKNIKA will be reviewed Peer Reviewers local and foreign.
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Articles 20 Documents
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Search results for , issue "Vol 11, No 2 (2008): NOVEMBER 2008" : 20 Documents clear
Perbandingan Kekerasan dan Kekuatan Tekan Paduan Cu – Sn 6% Hasil Proses Metalurgi Serbuk dan Sand Casting Suwanda, Totok; Rahman, Muh Budi Nur; Ramdani, Deny Fajrur
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Metal production by sand casting and powder metallurgy indicates the advantage of metal process technology. Bearing materials must have hardness and compressive strength properties to withstand wear and pressure load. Material porosity provides the space for lubricant. The lubrication will decrease the friction and keep temperature low. Low friction and low temperature will increase the life time of bearing. The goal of this research is to compare the hardness, compressive strength, macrostructure and microstructure between Cu-Sn 6% alloy produced by sand casting and by powder metallurgy. During sand casting process, the metal was melted in the furnace and then poured in to the sand mold, whilst in the powder metallurgy process; the metal powder was compacted in the metal mould and then heated to a temperature below its melting point (sintering process). In this research, the powder was compacted at 200 MPa and then sintered at 800° C for 45 minutes. The observation of the microstructure showed that the Cu-Sn 6%  alloy produced by powder metallurgy possessed more porositythan produced by sand casting. The sand casting process produced the Cu-Sn 6% alloy with Brinell Hardness Number (BHN) of 47.97 kgf/mm2 and compressive strength of 680.8 MPa. The powder metallurgy process produced the Cu-Sn 6% alloy with Brinell Hardness Number (BHN) of 27.08 kgf/mm2 and compressive strength of 944.4 MPa.
Konsep Earned Value dalam Aplikasi Pengelolaan Proyek Konstruksi Priyo, Mandiyo; Wibowo, Noor Adi
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Earned value concept is one of monitoring technique on construction process which is based on the integrated concept of cost and time. Using integrity of time and performance of field works, earned value method can accommodate the need of performance monitoring of construction project. The aim of this research is to observe the suitability of construction cost and time in the report compared to the plan report. In this research, observed data were taken from the bridge replacement project. The results show that the project construction at the end of 4th, 8th and 12th week with positive value of schedule variances, SV = 2.20 week, 0.4606 week and 0.9963 week, respectively, present the construction process is faster than schedule. While, positive value of cost variances, CV = IDR 3,543,762.17, IDR 115,583,274.67 and IDR 206,090,828.00 at the end of 4th, 8th and 12th week  shows that the cost of construction project is lower than budget plan. However, evaluation at the end of 16th week shows that the SV value is -0.1946 which means that the construction works are delayed from the schedule. Based on its CV value of IDR 196,892,110.00, the cost project is lower than the budget. These results are supported with the performance index of SPI which is lower than 1 and CPI is higher than 1.  
Perbandingan Model Turbulen Spalart-Allmaras dan Reynolds Stress Model pada Analisis Efisiensi dan Rugi Tekanan Siklon Caroko, Novi; Suyitno, Suyitno
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Two different turbulence models, i.e. Spalart Allmaras (SA) and Reynolds stress model (RSM) are used as turbulence model in the cyclone investigation via numerical simulation. The appropriate turbulence model is key parameter on the analysis of cyclone performance. The cyclone has a characteristic diameter of 30 cm. Four different inlet gas velocities, i.e. 13.6 m/s, 14.7 m/s, 16.3 m/s, and 17.8 m/s are simulated in FLUENT. It is found that the particle separation efficiency is higher 90% for all inlet gas velocities variation when RSM is used as turbulence model. The pressure drop is increasing linearly with the inlet gas velocity. The utilization of RSM can give better result of efficiency and pressure drop than SA turbulence model.    
Optimalisasi Kerja Tabung Induksi Menggunakan Mekanisme Katup pada Mesin Dua Langkah Jenis Yamaha Force 1 ZR Masy’ari, Masy’ari
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Rapid development of the automotive world, especially in the two-wheel motor vehicles, must also be compensated with fuel efficiency. Many ways has been used to save fuel for vehicles, particularly for two strokes (2t) gasoline motor, that uses YEIS (Yamaha Energy Induction System) technology, or known as tube Induction. This technology in general is used in Yamaha motorcycle engine with cylinder volume ranging from 155 cc, 135 cc, 150 cc to 250 cc. However the application of YEIS tube is not optimal. The goal of this research is to optimize the performance of the system by creating a system with valve mechanism to regulate incoming and outgoing flow of the mixture of fuel-air into the YEIS system. Induction tube acts as a buffer for fuel-air mixture preventing the mixture from returning to the carburetor during process strokes and then dispose of the rinse proceed with steps, so that the remaining fuel is not futile. The research was started with constructing induction tube, valves and valve housing, assembling and testing. The results of this research indicates that two-wheeled vehicles using an induction tube efficiency has better fuel efficiency than two-wheeled vehicle without induction tube and two-wheeled vehicle equipped with induction tube without the valve mechanism. The result also indicates that the acceleration of the vehicle is not reduced.
Studi Optimasi Peningkatan Kekuatan Bending Komposit Berpenguat Serat Nanas-Nanasan (Bromeliaceae) Kontinu Searah Rahman, Muh Budi Nur; Suwanda, Totok; Diharjo, Kuncoro
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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The objectives of this research are to observe the bending strength composite with bromeliaceae fiber with variations of alkali treatment duration, variations of fiber fraction volume and to observe the broken section characteristics. Materials used are bromilicea fiber, resin polyester, NaOH alkali and distilled water. The composite made with printing press methods. Dimensions of specimens and bending testing methods is done by to the standard ASTM D790 (bending test). Variables in this research are fiber fraction volume in the amount of 20-50% and the soaking times in alkali treatment are 0, 2, 4, 6 and 8 hours. Visualization of the broken section is shown in the macro picture. Highest bending strength and bending tensile occur in the composite with bromeliaceae fiber for 6-hour alkali treatment of 218.06 MPa and at the amount of 4.39% in fraction volume of 34.96%. Highest bending modulus occurs with 4 hours alkali treatment of 5.92% GPa. Composite with bromeliaceae fiber without alkali treatment has broken section characteristics fiber pull out, but the composite with alkali treatment has less fiber pull out characteristics.
Analisis Waktu Perjalanan Terhadap Pembukaan Jalur Lingkar Selatan Surakarta Menggunakan Program TFTP Suwardi, Suwardi
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Surakarta road network services high traffic volume to/from Surakarta city. It is caused by the activities are still centered. In addition, outside road network of city which is provided for traffic only passing Surakarta city is not available yet. Therefore, a Surakarta road network needs urgently to be expanded and a proposed ring-road is considered necessary. In order to anticipate the future traffic condition, effects of a proposed ring-road is studied. The aim of study is to predict the future traffic condition in terms of effective journey time after a proposed ring-road is implemented using Teacher Friendly Transportation Program (TFTP). The results show that effective journey time in 2009 and 2014 was significantly reduced after opening the proposed ring-road in the Surakarta road networks. The efficiency of journey time in 2009 was predicted in the range of 8 to 9 minutes for three alternatives and in 2014 was about 9 to 11 minutes. Meanwhile, the journey time for ring-road in 2009 was estimated in 17.1 minutes with the efficiency of journey time for alternative 1, 2 and 3 was calculated in 17.9, 10.9 and 13.9 minutes, respectively. The journey time for ring-road in 2014 was found to be 19 minutes with the efficiency of journey time for alternative 1, 2 and 3 is 20, 17.5 and 15, respectively.  
Uji Triaksial Unconsolidated-Undrained pada Campuran Tanah Lanau - Kapur - Abu Sekam Padi dan Serat Karung Plastik Widianti, Anita; Hartono, Edi; Muntohar, Agus Setyo
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Geotechnical and mechanical behaviour of soil stabilized with lime-rice husk ash and strengthened by randomly placed plastic fiber depends on the portions of the added materials and curing time. This research investigates the effect of the waste plastic sack fibers portion and the curing time to the stress – strain relationship and to the shear strength parameters of the mixture. In this study the portions of lime and rice husk ash were set as constant to the value of 12% and 24% respectively. The effect of four waste plastic sack fibers portion variation from 0.1% to 0.8% was measured by unconsolidated-undrained triaxial test. The samples were tested at 7, 14 and 21 days after mixing. In general, according to the test result, the inclusion of randomly waste plastic sack fiber and curing time have enhanced the shear strength parameters, the peak stress and the strain before failure.  With 0.2% fiber content, the cohesion and the internal friction angle values of the samples have increased 335% and 409% respectively compared with those of the samples having no added materials.
Analisis Ketepatan Penghitung Frekuensi dengan Metode Pencacahan Berbasis Mikrokontroler Kurniawan, Freddy; Basukesti, Agus
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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A frequency counter is an electronic instrument, or component of one, that is used for measuring frequency. Frequency counters usually measure the number of oscillations or pulse per second in a repetitive electronic signal. A digital-signal frequency counter, can measure the number of positive-going-transition or the number of negative-going-transition of signal in a set of period time. This microcontroller-based frequency counter work by using a counter, which accumulates the number of negative-going-transitions occurring within two periods for 16-bit microcontroller-timer overflow. After the period, the value in the counter is divided by the period and transferred to a display. This frequency counter can measure frequency from 100 Hz to 1 MHz. The upper limit of frequency can be extended up to 256 MHz by adding a frequency divider. The analysis of the accuracy of measuring presented in this article can support to determine the number of digit to display.  
Pengaruh Deposisi Lapisan Tipis Ti-Al-N Terhadap Umur Pahat Bubut HSS Nuri, Sigit Hidayat
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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The surface hardness of material can be improved through appropriate technique in surface coating. There are several various techniques have been used in order to obtain an optimum result of surface coating. One of them is sputtering technique. Thin layer deposition of Ti N + Al N (titanium nitride + aluminum nitride) materials with sputtering is a modern coating process for improving material properties. The objective of this paper is to obtain an optimum result on surface hardness of HSS cutting and lifetime cutting tool. The specimen with 9.4 ´ 9.4 ´ 11 mm was coated by Ti-N + Al-N materials in various temperatures, coating times, and gas pressure ratio of Ar and N2.   Hardness test of Micro Vickers was used for 10 gf of load in this study. The optimum hardness number (VHN0,01 1756.2) was reached at 150° C for 2 hours process of pressure ratio of Ar : N2 is 1 : 1 at 3.10-2 kg/cm2. The hardness number of HSS material was found to be 847, 9 VHN0,01. The HSS Ti N + Al N, deposition on HSS cutting tool were used in order to cut medium carbon steel with 1 mm cutting thickness at 0.084 mm/rev of feeding speed. The speed was varied for 35, 45 and 48 m/min. The HSS cutting tool coated by Ti N + Al N has 107 % of hardness and 144% ~ 149 % of life time compared to the uncoated cutting tool.
Pengaruh Diameter Katoda pada Sensitivitas Pengukuran Gradien Kecepatan dengan Metode Polarografi Sukamta, Sukamta
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Wall velocity gradient measurement using polarography gives very accurate output due to the absence of problem in fluid flow. Therefore this experiment is highly recommended. Based on the polarogram resulted in the polarography method, the potential that has to be applied to both electrode is 0.25 – 0.75 Volt, whilst in the experiment 0.45 is applied. Calibration has been done to single phase flow, by measuring as a result of  by friction between wall and current flow through electrode at constant flow rate. The ΔP data are used to determine τ. Relation plot between τ (resulted from ΔP measurement) and current can be obtained from the data acquisition device. The result of this research shows that the value of wall shear stress (as velocity gradient) is influenced by the increase of flow rate. Whilst measurement of wall shear stress shows that the cathode area gives effect on the sensitivity of the measurement,  a small cathode results in better shear stress data measurement (more sensitive). In this research the best wall shear stress was resulted in cathode with diameter d=0.2 mm.

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