Simulasi proses penyepuhan dengan teori Viscoelasticity

ABSTRAK Penyepuhan merupakan bagian yang penting dalam dunia industri, khususnya industri baja. Cara penyepuhan tidaklah sulit untuk dipraktekkan, namun untuk mendapatkan hasil yang terbaik atau maksimal, perlu pengkajian yang lebih mendalam. Teori viscoelastisitas memberi angin baru dalam mengusahakan cara penyepuhan terbaik, karena memungkinkan analisis memakai komputer. Dengan simulasi ini diharapkan adanya analisis yang relatip murah, namun membuahkan hasil yang balk dalam hal suhu pemanasan, suhu pendingin, atau laju pendinginan yang terbaik bagi suatu penyepuhan logam maupun non-logam. Keywords: Visoelasticity, penyepuhan, baj

Pengaruh Perlakuan Panas Pasca Pengelasan Terhadap Laju Perambatan Retak Lelah Baja SS 400

Low carbon steel welding problems are the non-homogenous structure, the high residual stress, and inclusion. These conditions will increase the fatigue crack growth rate effectively. Post weld heat treatments (PWHT) can be estimated to minimize these problems. In this research, the influence of post weld heat treatments on crack growth rate of SS 400 steel was investigated. Carbon dioxide shielded GMAW process was used on butt joint of 9 mm thick SS 400 steel raw material. Four conditions of PWHT, i.e. P1, P2, P3, and P4 were treated on welding joint. For first condition, the specimen was held for 1 hour at 150 °C furnace temperature, then heated to 750 °C and held for 2 hours, then cooled in air to room temperature (P1). For 2nd condition (P2), the specimen was treated as in P1, except it was held for 1 hour at 450 °C furnace temperature. For third condition (P3), the specimen was cooled in air to room temperature, then heated to 750°C and held for 2 hours, followed by air cooling to room temperature. For fourth condition (P4), the specimen was treated as in P3, except it was cooled in the furnace at a rate of 50°C/hour to room temperature. The crack growth rate tests were carried out on 6,5 mm thick of compact tension specimen (CTS). The results were compared with the welded specimen without treatment (C1) and the base material (BM). The result shows that PWHT decreases crack growth rate on weld metal and HAZ effectively. The highest crack growth rate of transversal butt joint on weld metal was welding specimen without treatment (C1), having Paris constant number (n) = 4.21, and the lowest was P4, with n = 3.01. PWHT decreased the weld metal crack growth rate 20.19-28.503 % compare to Cl and decreased 2.687-10.149 % compare to BM. The crack growth rate of HAZ by PWHT increased 4.437-17.065 % compare to Cl. The lowest of HAZ crack growth rate of longitudinal butt joint was P4 with n = 4.066 and the lowest of weld metal crack growth rate of longitudinal butt joint was P2 with n = 2.61 Key words: fatigue crack growth rate, post weld heat treatment, Paris constant numbe

Modifikasi Sifat Mekanik Dan Ketahanan Korosi Paduan Fe-1,52Al-1,44C Dengan Proses Tempiring

Aluminum is third of biggest element in the world and cheaper relatively. The Fe-Cr-C alloy is promised alloy to replace the Fe-Cr-C alloy. The purpose of the research is to investigate influence of temperature to microstructure, tensile strength, hardness, and corrosion resistance of Fe-Al-C in the 3.5% NaCl solution. Raw material for casting is low Mn steel, FeMn HC, pure aluminum, slag remover. The melting used low frequency induction furnace which has 50 kg capacity. Hardening at 900oC, and then quenching in the water, the last temper along 1 hour with various temperature; 250oC, 300oC, 350oC, 400oC, 450oC and cooling in the air. Chemical composition, microstructure, tensile strength, hardness, and corrosion resistance of Fe-Al-C in the 3.5% NaCl solution were investigated. The result of the chemical composition investigation showed that Fe-Al-C alloy contained 1.52% Al, and 1.44% C. The microstructure of Fe-1.52 Al-1,44C alloy is ferrite and pearlite. The tensile strength of Fe-1.52 Al-1,44C alloy is 33.77 kg/mm2. The tensile strength raised after hardening process became 74.44 kg/mm2 and turn off again after tempering process. The Vickers hardness investigation showed that the Fe-1.52 Al-1,44C alloy has 232.4 VHN and raised after hardening became 298.7 VHN. Highest corrosion rate is 0,927 mm/year after hardening and lowest is 0.196 mm/year after tempering at 300oC (good category corrosion resistance)

Fatigue Behavior of Resistance Spot-Welded Unequal Sheet Thickness Austenitic Stainless Steel

This paper presents a comparative study on the fatigue strength of resistance spot-welded unequal and equal sheet thickness austenitic stainless steel. Lap joints of 3.0-1.0 mm and 1.0-1.0 mm thick austenitic stainless steel were made using the same resistance spot welding schedule with current, weld time and electrode force of 4.7 kA, 20 cycles and 6 kN respectively. The sinusoidal wave form with a constant stress amplitude was selected in the fatigue tests whereas the stress ratio and frequency used were 0.1 and 8 Hz respectively. Fatigue strength and tensile-shear load bearing capacity of 3.0-1.0 mm joint were higher than that of 1.0-1.0 mm joint, although its nugget diameter was smaller. The joint stiffness was the controlling factor of the fatigue strength of resistance spot-welded unequal sheet thickness austenitic stainless steel

Pengaruh penambahan ejektor (JET) pada pompa air

ABSTRAK Pompa air bagi banyak orang sudah menjadi bagian dari sarana penunjang hidup. Tiap hari kita perlu air, dan ka/au pomp(\u27 tidak bekerja, semuanya kalang kabut. Kerusakan pompa sebagian besar disebabkan oleh keausan, yang terjadi karena adanya gesekan antara sudu yang berputar dengan rutnah pompa. Akibat dari keausan tadi, jarak antara kedua per¬mukaan menjadi setnakin jauh, sehingga aliran air yang bocor lewat celah yang aus tadi setnakin banyak, atau air yang sudah dipotnpa tnakin banyak yang ketnbali ke bagian hisap. Kalau hal ini dibiarkan akibatnya jelas, yaitu debit air makin kecil, atau bahkan Rona seka/i tidak keluar airnya, walauptin terdengar potnpa inasih berputar. Kemungkinan lain adalah turunnya permukaan air sumur pada muslin ketnarau. Balk keausan maupun turunnya air sumur, keduanya dapat ditanggulangi dengan cara yang dirasa murah dan praktis yaitu menambah ejektor (ejector) pada saluran hisapnya. Jumlah ejektor yang dipasangkan pada saluran hisap ini pada prinsipnya dapat lebih dart satu, dan diletakkan secara seri, sehingga memperoleh daya hisap yang jauh lebih balk. Tulisan ini mencoba memberikan gambaran untuk kerja atau karakteristik pompa sembarang dengan ejektor yang tersedia di pasaran sebagai suku cadang pompa khusus. Keywords: suku cadang pompa, ejaktor, pompa ai

Karakterisasi Ball Mill Import Pada Industri Semen Di Indonesia

The purpose of this research is to investigate the characteristics of import Ball Mill which is used at cement mills in Indonesia. There were two kind of import Ball Mill from PT. Semen Gresik, Tbk that used in this research which are A type (Ø 30 mm) and B type (Ø 40 mm). Visual investigation, chemistry composition, distribution of hardness, and microstructure photograph was conducted characterize these ball mill. Visually, the import Ball Mill has rough surface, white coloring when cut off, and small cracks at all specimens. Type A ball mill contains of 2,934% C, 11,231% Cr, and 0,177% Mo, where type B Ball Mill contains of 2,693% C, 12,31% Cr, and 1,103% Mo. Both are martensitic white cast iron ASTM A532 Class II type A. The surface are harder then the its core. The highest hardness on the surface are 720,82 kg/mm2 (type A) and 746,5 kg/mm2 (type B), where as lowest hardness on the core are 631,1 kg/mm2 (type A) and 544,0 kg/mm2 (type B). Microstructure investigation shows Perlit, Cementit, and Martensit

Corrosion Resistance of AISI 316L after Short Holding Time of High Temperature Gas Nitriding (HTGN)

Stainless steel AISI 316L is widely used as biomaterial due to its high corrosion resistance. However this property decreases in highly stressed and oxygen depleted environments. Several methods have been developing to increase the corrosion resistance such as low and high temperature gas nitriding. High temperature gas nitriding (HTGN) produces more depth effect than low temperature gas nitriding. Unfortunately HTGN for long holding time results on grain coarsening which reduce its tensile strength. The objective of this research is to determine the effect of HTGN at short holding time on the corrosion resistance, hardness and grain coarsening of AISI 316L. Specimens were made from as rolled 1 mm thickness AISI 316L plate. Before HTGN process, the specimens were rinsed using ultrasonic cleaner in acetone medium. HTGN process was conducted at temperature 1050oC, 1100oC and 1200oC for short period holding time i.e. 15 and 30 minutes. Micro hardness, microstructure and corrosion tests were conducted in the simulated body fluid (SBF) to evaluate the process. The results show that hardness and corrosion resistance were increased significantly after HTGN process. Moreover, hardness for holding time of 30 minutes was higher than 15 minutes, however the corrosion resistance were decreased. In addition HTGN process also results on grain coarsening at 30 minutes holding time, however for holding time 15 minutes and temperature 1050oC and 1100oC did not give significant grain coarsening. Therefore, the HTGN process parameters must be optimized for compromise between hardness and corrosion resistance. Keywords: high temperature gas nitriding, corrosion resistance, grain coarsening, AISI 316

Detection and Identification of Detonation Sounds in an Internal Combustion Engine using Wavelet and Regression Analysis

Improving efficiency and power in an internal combustion engine is always impeded by detonation (knock) problems. This detonation problem has not been explained fully yet. Quick and accurate detection of detonation is also in the development stage. This research used a new method of detonation sound detection which uses microphone sensors, analysis of discrete wavelet transform (DWT), and analysis of the regression function envelope to identify the occurrence of detonation. The engine sound was captured by the microphone; it was recorded on a computer; it was proceeded using a DWT decomposition filtering technique; it was then subjected to normalization and regression function envelope to get the shape of the wave pattern for the vibration. Vibrational wave patterns were then compared to a reference using the Euclidean distance calculation method, in order to identify and provide an assessment decision as to whether or not detonation had occurred. The new method was applied using Matlab and it has yielded results which are quite effective for the detection and identification of detonation and it is also capable of producing an assessment decision about the occurrance of detonation

Assessment of Nugget Size of Spot Weld using Neutron Radiography

Resistance spot welding (RSW) has been widely used for many years in the fabrication of car body structures, mainly due to the cost and time considerations. The weld quality as well as the nugget size is an issue in various manufacturing and processes due to the strong link between the weld quality and safety. It has led to the development of various destructive and non-destructive tests for spot welding such as peel testing, ultrasonic inspections, digital shearography, and infrared thermography. However, such methods cannot show spot weld nugget visually and the results are very operator’s skill dependent. The present work proposes a method to visualize the nugget size of spot welds using neutron radiography. Water, oil and various concentrations of gadolinium oxide-alcohol mixture were evaluated as a contrast media to obtain the best quality of radiography. Results show that mixture of 5 g gadolinium oxide (Gd2O3) in 25 ml alcohol produces the best contrast. It provides the possibility to visualize the shape and size of the nugget spot weld. Furthermore, it can discriminate between nugget and corona bond. The result of neutron radiography evaluation shows reasonable agreement with that of destructive test. Received: 13 October 2010; Revised: 25 August 2011; Accepted 26 August 201

Perilaku Laju Rambatan Retak Fatik Sambungan Spiral Las Busur Rendam Pipa Baja API 5L X-52 yang Mengalami Perlakuan Panas Stress Relief.

Spiral welded steel pipes are widely used for oil/gas (API) transmission. Such pipes are usually produced by forming hot-rolled coil (HRC) steels into tubular products and welding is performed along spirally joining lines using a submerged arc welding (SAW) process. For structural applications, weld metals for API 5L X-52 steel pipes must have high strength, good impact toughness and high resistance to fatigue crack growth. The present investigations aims to study effects of stress relief heat treatment on mechanical properties of submerged arc spiral welded API 5L X-52 steel pipes in particular fatigue crack growth behaviour. Experiments were carried out by heating submerged arc steel weld metals of API 5L X-52 steel pipes to various temperatures, namely 400, 500 and 600 °C for 3 hours. Subsequently, a sequence of tests were conducted including microstructural examination, hardness test, tensile test and fatigue crack growth test. Results of this investigation show that stress relief heat treatment is proved to improve resistance to crack growth. At low AK, the weld metal which is heat treated at 600 °C reveals the highest resistance to fatigue marked its lowest value of A. However, for higher AK, the n value of the weld metal heat treated at 500 °C is the lowest suggesting that this weld metal has optimum resistance to fatigue crack growth. Keywords : API 5L X-52 steel pipes, submerged arc welding and fatigue crack growt