Search results for: steel alloys

Authors: M. Deyab, A. Al-Sabagh, S. Keera

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The effects of flow velocity, sand concentration, sand size and temperature on erosion-corrosion of carbon steel in oil sands slurry were studied by electrochemical polarization measurements. It was found that the anodic excursion spans of carbon steel in oil sands slurry are characterized by the occurrence of a well-defined anodic peak, followed by a passive region. The data reveal that increasing flow velocity, sand concentration and temperature enhances the anodic peak current density (jAP) and shifts pitting potential (Epit) towards more negative values. The variation of sand particle size does not have apparent effect on polarization behavior of carbon steel. The ratios of the erosion rate to corrosion rate (E/C) were calculated and discussed. The ratio of erosion to corrosion rates E/C increased with increasing the flow velocity, sand concentration, sand size and temperature indicating that an increasing slurry flow velocity, sand concentration, sand size and temperature resulted in an enhancement of the erosion effect.

Keywords: erosion-corrosion, steel, oil sands slurry, polarization

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Authors: J. M. Lee, W. R. Noh, C. Y. Kim, M. G. Lee

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Delamination of oxide scale has been often discovered at the interface between Fe carbon steel and oxide scale. Among several mechanisms of this delamination behavior, the normal tensile stress to the substrate-scale interface has been described as one of the main factors. The stress distribution at the interface is also known to be affected by thermal expansion mismatch between substrate and oxide scale, creep behavior during cooling and the geometry of the interface. In this study, stress states near the interface in a Fe carbon steel with oxide scale have been investigated using FE simulations. The thermal and mechanical properties of oxide scales are indicated in literature and Fe carbon steel is measured using tensile testing machine. In particular, the normal and shear stress components developed at the interface during bending are investigated. Preliminary numerical sensitivity analyses are provided to explain the effects of the interface geometry and oxide thickness on the delamination behavior.

Keywords: oxide scale, delamination, Fe analysis, roughness, thickness, stress state

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Authors: Songyan Yin, Ravindra Rajarao, Veena Sahajwalla

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Automotive plastics waste (widely known as auto-fluff or ASR) is a complicated mixture of various plastics incorporated with a wide range of additives and fillers like titanium dioxide, magnesium oxide, and silicon dioxide. Automotive plastics waste is difficult to recycle and its landfilling poses the significant threat to the environment. In this study, a sustainable technology to fabricate protective nanoscale TiN thin film on a steel substrate surface by using automotive waste plastics as titanium and carbon resources is suggested. When heated automotive plastics waste with steel at elevated temperature in a nitrogen atmosphere, titanium dioxide contented in ASR undergo carbothermal reduction and nitridation reactions on the surface of the steel substrate forming a nanoscale thin film of titanium nitride on the steel surface. The synthesis of TiN film on steel substrate under this technology was confirmed by X-ray photoelectron spectrometer, high resolution X-ray diffraction, field emission scanning electron microscope, a high resolution transmission electron microscope fitted with energy dispersive X-ray spectroscopy, and inductively coupled plasma mass spectrometry techniques. This sustainably fabricated TiN film was verified of dense, well crystallized and could provide good oxidation resistance to the steel substrate. This sustainable fabrication technology is maneuverable, reproducible and of great economic and environmental benefit. It not only reduces the fabrication cost of TiN coating on steel surface, but also provides a sustainable environmental solution to recycling automotive plastics waste. Moreover, high value copper droplets and char residues were also extracted from this unique fabrication process.

Keywords: automotive plastics waste, carbonthermal reduction and nitirdation, sustainable, TiN film

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Authors: A. Azizi, M. Toubane, L. Chetibi

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Differential scanning calorimetry (DSC) is a widely used technique for the study of phase transformations, particularly in the study of precipitation. The kinetic of the precipitation and dissolution is always related to the concept of activation energy Ea. The determination of the activation energy gives important information about the kinetic of the precipitation reaction. In this work, we were interested in the study of the isothermal and non-isothermal treatments on the decomposition of the supersaturated solid solution in the alloy AZ91 (Mg-9 Al-Zn 1-0.2 Mn. mass fraction %), using Differential Calorimetric method. Through this method, the samples were heat treated up to 425° C, using different rates. To calculate the apparent activation energies associated with the formation of precipitated phases, we used different isoconversional methods. This study was supported by other analysis: X-ray diffraction and microhardness measurements.

Keywords: calorimetric, activation energy, AZ91 alloys, microstructural evolution

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Authors: Zi-Ang Li, Mu-Xuan Tao

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During the process of the industrialization of steel structure housing, a composite structural system with separated gravity and lateral resistant systems has been applied in engineering practices, which consists of composite frame with hinged beam-column joints, steel brace and RC shear wall. As an attempt in steel structural system area, seismic performance evaluation of the separated composite structure is important for further application in steel housing. This paper focuses on the seismic performance comparison of the separated composite structural system and traditional steel frame-shear wall system under the same inter-story drift ratio (IDR) provision limit. The same architectural layout of a high-rise building is designed as two different structural systems at the same IDR level, and finite element analysis using pushover method is carried out. Static pushover analysis implies that the separated structural system exhibits different lateral deformation mode and failure mechanism with traditional steel frame-shear wall system. Different indexes are adopted and discussed in seismic performance evaluation, including IDR, safe factor (SF), shear wall damage, etc. The performance under maximum considered earthquake (MCE) demand spectrum shows that the shear wall damage of two structural systems are similar; the separated composite structural system exhibits less plastic hinges; and the SF index value of the separated composite structural system is higher than the steel frame shear wall structural system.

Keywords: finite element analysis, new composite structural system, seismic performance evaluation, static pushover analysis

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Authors: Paul Stonaha, Mariia Romashchenko, Xaio Xu

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Magnetic shape memory alloys (MSMAs) are promising technological materials for a range of fields, from biomaterials to energy harvesting. We have performed inelastic neutron scattering on two powder samples of cobalt-based high-entropy MSMAs across a range of temperatures in an effort to compare calculations of thermodynamic properties (entropy, specific heat, etc.) to the measured ones. The measurements were correct for multiphonon scattering and multiple scattering contributions. We present herein the neutron-weighted vibrational density of states. Future work will utilize DFT calculations of the disordered lattice to correct for the neutron weighting and retrieve the true thermodynamical properties.

Keywords: neutron scattering, vibrational dynamics, computational physics, material science

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Authors: Julien Monnier, Isabelle Mouton, Francois Buy, Adrien Michel, Sylvain Ringeval, Joel Malaplate, Caroline Toffolon, Bernard Marini, Audrey Lechartier

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Chosen to design and assemble massive components for nuclear industry, the 316 Nb austenitic stainless steel (also called 316 Nb) suits well this function thanks to its mechanical, heat and corrosion handling properties. However, these properties might change during steel’s life due to thermal ageing causing changes within its microstructure. Our main purpose is to determine if the 316 Nb will keep its mechanical properties after an exposition to industrial temperatures (around 300 °C) during a long period of time (< 10 years). The 316 Nb is composed by different phases, which are austenite as main phase, niobium-carbides, and ferrite remaining from the ferrite to austenite transformation during the process. Our purpose is to understand thermal ageing effects on the material microstructure and properties and to submit a model predicting the evolution of 316 Nb properties as a function of temperature and time. To do so, based on Fe-Cr and 316 Nb phase diagrams, we studied the thermal ageing of 316 Nb steel alloys (1%v of ferrite) and welds (10%v of ferrite) for various temperatures (350, 400, and 450 °C) and ageing time (from 1 to 10.000 hours). Higher temperatures have been chosen to reduce thermal treatment time by exploiting a kinetic effect of temperature on 316 Nb ageing without modifying reaction mechanisms. Our results from early times of ageing show no effect on steel’s global properties linked to austenite stability, but an increase of ferrite hardness during thermal ageing has been observed. It has been shown that austenite’s crystalline structure (cfc) grants it a thermal stability, however, ferrite crystalline structure (bcc) favours iron-chromium demixion and formation of iron-rich and chromium-rich phases within ferrite. Observations of thermal ageing effects on ferrite’s microstructure were necessary to understand the changes caused by the thermal treatment. Analyses have been performed by using different techniques like Atomic Probe Tomography (APT) and Differential Scanning Calorimetry (DSC). A demixion of alloy’s elements leading to formation of iron-rich (α phase, bcc structure), chromium-rich (α’ phase, bcc structure), and nickel-rich (fcc structure) phases within the ferrite have been observed and associated to the increase of ferrite’s hardness. APT results grant information about phases’ volume fraction and composition, allowing to associate hardness measurements to the volume fractions of the different phases and to set up a way to calculate α’ and nickel-rich particles’ growth rate depending on temperature. The same methodology has been applied to DSC results, which allowed us to measure the enthalpy of α’ phase dissolution between 500 and 600_°C. To resume, we started from mechanical and macroscopic measurements and explained the results through microstructural study. The data obtained has been match to CALPHAD models’ prediction and used to improve these calculations and employ them to predict 316 Nb properties’ change during the industrial process.

Keywords: stainless steel characterization, atom probe tomography APT, vickers hardness, differential scanning calorimetry DSC, thermal ageing

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Authors: Krolo Paulina

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The seismic response of moment-resisting steel frames depends on the behavior of the joints, especially when they are considered as ductile zones. The aim of this research is to provide a realistic assessment of the moment-resisting steel frame behavior under seismic loading using nonlinear static pushover analysis (N2 method). The hysteresis behavior of the joints in the frame model was described using a new hysteresis envelope model. The obtained seismic response was compared with the results of the seismic analysis obtained for the same steel frame that takes into account the monotonic model of the joints.

Keywords: beam-to-column joints, hysteresis envelope model, moment-resisting frame, nonlinear static pushover analysis, N2 method

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Authors: M. E. Abou-Hashem El Dib, M. K. Swailem, M. M. Metwally, A. I. El Awady

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This paper presents the effect of stiffeners on the behavior of slender steel I-beams. Nonlinear three dimensional finite element models are developed to represent the stiffened steel I-beams. The well established finite element (ANSYS 13.0) program is used to simulate the geometric and material nonlinear nature of the problem. Verification is achieved by comparing the obtained numerical results with the results of previous published experimental work. The parameters considered in the analysis are the horizontal stiffener's position and the horizontal stiffener's dimensions as well as the number of vertical stiffeners. The studied dimensions of the horizontal stiffeners include the stiffener width, the stiffener thickness and the stiffener length. The results of the achieved numerical parametric study for slender steel I-beams show the significant effect of stiffeners on the beam behavior and its failure load.

Keywords: beams, local buckling, slender, stiffener, thin walled section

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Authors: Yiğit Gürler, İbrahim Şimşek, Müge Savaştaer, Ayberk Karakuş, Alper Taşdemirci

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316L steel is frequently used in the industry due to its easy formability and accessibility in sheet metal forming processes. Numerical and experimental studies are frequently encountered in the literature to examine the mechanical behavior of 316L stainless steel during the forming process. 316L stainless steel is the most common material used in the production of plate heat exchangers and plate heat exchangers are produced by plastic deformation of the stainless steel. The motivation in this study is to determine the appropriate material model during the simulation of the sheet metal forming process. For this reason, two different material models were examined and Ls-Dyna material cards were created using material test data. These are MAT133_BARLAT_YLD2000 and MAT093_SIMPLIFIED_JOHNSON_COOK. In order to compare results of the tensile test & hydraulic bulge test performed both numerically and experimentally. The obtained results were evaluated comparatively and the most suitable material model was selected for the forming simulation. In future studies, this material model will be used in the numerical modeling of the sheet metal forming process.

Keywords: 316L, mechanical characterization, metal forming, Ls-Dyna

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Authors: J. Ptačinová, J. Ďurica, P. Jurči, M Kusý

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Ledeburitic tool steel Vanadis 6 has been subjected to sub-zero treatment (SZT) at -140 °C and -196 °C, for different durations up to 48 h. The microstructure and hardness have been examined with reference to the same material after room temperature quenching, by using the light microscopy, scanning electron microscopy, X-ray diffraction, and Vickers hardness testing method. The microstructure of the material consists of the martensitic matrix with certain amount of retained austenite, and of several types of carbides – eutectic carbides, secondary carbides, and small globular carbides. SZT reduces the retained austenite amount – this is more effective at -196 °C than at -140 °C. Alternatively, the amount of small globular carbides increases more rapidly after SZT at -140 °C than after the treatment at -140 °C. The hardness of sub-zero treated material is higher than that of conventionally treated steel when tempered at low temperature. Compressive hydrostatic stresses are developed in the retained austenite due to the application of SZT, as a result of more complete martensitic transformation. This is also why the population density of small globular carbides is substantially increased due to the SZT. In contrast, the hardness of sub-zero treated samples decreases more rapidly compared to that of conventionally treated steel, and in addition, sub-zero treated material induces a loss the secondary hardening peak.

Keywords: microstructure, Vanadis 6 tool steel, sub-zero treatment, carbides

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Authors: Sunthorn Sittisakuljaroen

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The edge waviness in hot rolled steel is a common defect. Variables that effect for such defect include as raw material and machine. These variables are necessary to consider. This research studied the defect of edge waviness for SS 400 of metal sheet manufacture. Defect of metal sheets divided into two groups. The specimens were investigated on chemical composition and mechanical properties to find the difference. The results of investigate showed that not different to a standard significantly. Therefore the roll milled machine for sample need to adjustable rollers for press on metal sheet which was more appropriate to adjustable at both ends.

Keywords: edge waviness, hot rolling steel, metal sheet defect, SS 400, roll leveller

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Authors: Anna Dziubinska

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The applications of magnesium alloys in transport include all kinds of vehicle wheels for cars, motorcycles, bicycles, trolleys, etc. Modern technologies of manufacturing products from these materials have been noticeably improved recently, creating new possibilities for their application. Continuously developed technologies for forming Mg alloys must not be overlooked, which make it possible to manufacture products with better properties compared to those obtained by casting only. The article reviews the specialized literature on magnesium wheel forming and presents a concept of technology for forging magnesium wheels for light vehicles from cast preforms. The research leading to these results has received funding from the Norway Grants 2014-2021 via the National Centre for Research and Development.

Keywords: forming, forging, magnesium alloy, wheels, vehicles

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Authors: Mohammad Farooq Wani

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Tribological characterization of ZrN coatings deposited on titanium modified austenitic stainless steel (alloy D-9) substrates has been investigated. The coatings were deposited in the deposition temperature range 300–873 K, using the pulsed magnetron sputtering technique. Scratch adhesion tests were carried out using Rc indenter under various conditions of load. Detailed tribological studies were conducted to understand the friction and wear behaviour of these coatings. For all tribological studies steel and ceramic balls were used as counter face material. 3D-Surface profiles of all wear tracks was carried out using 3D universal profiler.

Keywords: ZrN, Surafce coating, thin film, tribology, friction and wear

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Authors: C. Boubechou, A. Bouchoucha, H. Zaidi

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The aim of this paper is to study the tribological behavior of a dynamic contact steel-brass couple with electric current. This study looks at a dry contact brass-steel couple where friction and wear are studied in terms of mechanical and electrical parameters. For this reason, a tribometer, pin-rotary disc is used in an atmospheric atmosphere. The test parameters are as follows: the normal load (5-30N), the sliding speed (0.1 to 0.5 m / s) and the electric current (3-10A). The duration of each test is 30 minutes. The experimental results show that these parameters have a significant effect on the tribological behavior of the couple studied. The discussion of results is based on observations, using an optical microscope, MEB and a profilometer, worn surfaces and interface phenomena resulting from the process of sliding contact.

Keywords: brass-steel couple, dry friction, electrical current, morphology, normal load, sliding speeds, wear

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Authors: Jin-Hee Ahn, Seok-Hyeon Jeon, Young-Bin Lee, Min-Gyun Ha, Yu-Chan Hong

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Corrosion durability of steel bridges can be generally affected by atmospheric environments of bridge installation, since corrosion problem is related to environmental factors such as humidity, temperature, airborne salt, chemical components as SO₂, chlorides, etc. Thus, atmospheric environment condition should be measured to estimate corrosion condition of steel bridges as well as measurement of actual corrosion damage of structural members of steel bridge. Even in the same atmospheric environment, the corrosion environment may be different depending on the installation direction of structural members. In this study, therefore, atmospheric corrosion monitoring was conducted using atmospheric corrosion monitoring sensor, hygrometer, thermometer and airborne salt collection device to examine the corrosion durability of steel bridges. As a target steel bridge for corrosion durability monitoring, a cable-stayed bridge with truss steel members was selected. This cable-stayed bridge was located on the coast to connect the islands with the islands. Especially, atmospheric corrosion monitoring was carried out depending on structural direction of a cable-stayed bridge with truss type girders since it consists of structural members with various directions. For atmospheric corrosion monitoring, daily average electricity (corrosion current) was measured at each monitoring members to evaluate corrosion environments and corrosion level depending on structural members with various direction which have different corrosion environment in the same installed area. To compare corrosion durability connected with monitoring data depending on corrosion monitoring members, monitoring steel plate was additionally installed in same monitoring members. Monitoring steel plates of carbon steel was fabricated with dimension of 60mm width and 3mm thickness. And its surface was cleaned for removing rust on the surface by blasting, and its weight was measured before its installation on each structural members. After a 3 month exposure period on real atmospheric corrosion environment at bridge, surface condition of atmospheric corrosion monitoring sensors and monitoring steel plates were observed for corrosion damage. When severe deterioration of atmospheric corrosion monitoring sensors or corrosion damage of monitoring steel plates were found, they were replaced or collected. From 3month exposure tests in the actual steel bridge with various structural member with various direction, the rust on the surface of monitoring steel plate was found, and the difference in the corrosion rate was found depending on the direction of structural member from their visual inspection. And daily average electricity (corrosion current) was changed depending on the direction of structural member. However, it is difficult to identify the relative differences in corrosion durability of steel structural members using short-term monitoring results. After long exposure tests in this corrosion environments, it can be clearly evaluated the difference in corrosion durability depending on installed conditions of steel bridges. Acknowledgements: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1D1A1B03028755).

Keywords: corrosion, atmospheric environments, steel bridge, monitoring

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Authors: Anna Jastrzebska, K. S. Suresh, T. Kitashima, Y. Yamabe-Mitarai, Z. Pakiela

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Near α titanium alloys are important materials for aerospace applications, especially in high temperature applications such as jet engine. Mechanical properties of Ti alloys strongly depends on their processing route, then it is very important to understand micro-structure change by different processing. In our previous study, Nb was found to improve oxidation resistance of Ti alloys. In this study, micro-structure evolution of Ti-6Al-4Nb (wt %) alloy was investigated after plain strain compression test in hot working temperatures in the α and β phase region. High-resolution EBSD was successfully used for precise phase and texture characterization of this alloy. 1.1 kg of Ti-6Al-4Nb ingot was prepared using cold crucible levitation melting. The ingot was subsequently homogenized in 1050 deg.C for 1h followed by cooling in the air. Plate like specimens measuring 10×20×50 mm3 were cut from an ingot by electrical discharge machining (EDM). The plain strain compression test using an anvil with 10 x 35 mm in size was performed with 3 different strain rates: 0.1s-1, 1s-1and 10s-1 in 700 deg.C and 1050 deg.C to obtain 75% of deformation. The micro-structure was investigated by scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD) detector. The α/β phase ratio and phase morphology as well as the crystallographic texture, subgrain size, misorientation angles and misorientation gradients corresponding to each phase were determined over the middle and the edge of sample areas. The deformation mechanism in each working temperature was discussed. The evolution of texture changes with strain rate was investigated. The micro-structure obtained by plain strain compression test was heterogeneous with a wide range of grain sizes. This is because deformation and dynamic recrystallization occurred during deformation at temperature in the α and β phase. It was strongly influenced by strain rate.

Keywords: EBSD, plain strain compression test, Ti alloys

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Authors: Parisa Hasanpour, Bahram Borooghani, Vahid Asadi

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In the current research, a catastrophic failure of a 304 stainless steel flange at pipeline transportation of ethylene in a petrochemical refinery was studied. Cracking was found in the flange after about 78840h service. Through the chemical analysis, tensile tests in addition to microstructural analysis such as optical microscopy and Scanning Electron Microscopy (SEM) on the failed part, it found that the fatigue was responsible for the fracture of the flange, which originated from bumps and depressions on the outer surface and propagated by vibration caused by the working condition.

Keywords: failure analysis, 304 stainless steel, fatigue, flange, petrochemical refinery

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Authors: Lucian Capitanu, Virgil Florescu

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Often for the laboratory studies, modeling of specific tribological processes raises special problems. One such problem is the modeling of some temperatures and extremely high contact pressures, allowing modeling of temperatures and pressures at which the injection or extrusion processing of thermoplastic materials takes place. Tribological problems occur mainly in thermoplastics materials reinforced with glass fibers. They produce an advanced wear to the barrels and screws of processing machines, in short time. Obtaining temperatures around 210 °C and higher, as well as pressures around 100 MPa is very difficult in the laboratory. This paper reports a simple and convenient solution to get these conditions, using friction sliding couples with linear contact, cylindrical liner plastic filled with glass fibers on plate steel samples, polished and super-finished. C120 steel, which is a steel for moulds and Rp3 steel, high speed steel for tools, were used. Obtaining the pressure was achieved by continuous request of the liner in rotational movement up to its elasticity limits, when the dry friction coefficient reaches or exceeds the hardness value of 0.5 HB. By dissipation of the power lost by friction on flat steel sample, are reached contact temperatures at the metal surface that reach and exceed 230 °C, being placed in the range temperature values of the injection. Contact pressures (in load and materials conditions used) ranging from 16.3-36.4 MPa were obtained depending on the plastic material used and the glass fibers content.

Keywords: plastics with glass fibers, dry friction, linear contact, contact temperature, contact pressure, experimental simulation

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Authors: N. Jena, Nitin Seth

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Globalization and free trade has forced the organizations to continuously rethink and rework on the increasing cost of logistics. World wide, it is visualized that on one side the steel sector is witnessing rapid growth and on the other side it is facing huge challenges in terms of availability of raw materials for uninterrupted production. Inbound logistics also gains significant importance for ensuring the timely availability of raw materials. It is seen that in Indian steel sector logistic cost is still very large and challenging. Effectively managing the inbound logistics in steel decides the profitability and serviceability of the organization. Effective management of inbound logistics also has a major role on the inventory of the organization. Since, the logistics for the steel industry in India is evolving rapidly and it is the interplay of infrastructure, technology and new types of service providers that will define whether the industry is able to help its customers to reduce their logistics costs. Integration of Logistics has been treated as one of the most potential area for the companies to provide a base for cost reduction. In spite of the proven area for benefits for the industry, it is very surprising that none of the researchers have explored this area. Although, many researchers explored the subject of logistics in steel industry, but their perspective varied from exploring and understanding the associated cost and finding out the relations between them. Visualizing a potential gap, the present research is under taken to explore the integration opportunities in inbound logistics for steel sector. Typically in Indian steel sector where in most of the manufacturers depend on imported materials for processing the logistics is very challenging and accounts for transactions at supplier – who is situated in different country, shipper- who is transporting the material to the host country, regulators in both countries-that include customs and various clearing agents, local logistics service providers and local transporters/handlers. It is seen that In bound logistics cost in the steel sector is very high and accounts for about 15-16% of the turn over, integration of information across different channels provides and opportunity for improvements and growth of the organization. In the present paper, a case of leading steel manufacturer has been taken and the potentials for integration of information across various partners have been identified. The paper provides the identification of grey area in steel sector for major improvements in cycle time and lowering the inventories by integration of information. Finally, based on integration of information, the paper presents a business information framework for steel sector.

Keywords: integration, steel sectors, suppliers, shippers, customs and cargo agents, transporters

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Authors: S. Ilahi, M. Baira, F. Saidi, N. Yacoubi, L. Auvray, H. Maaref

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Photo-thermal deflection technique (PTD) is used to study the nonradiative recombination process in BGaAs/GaAs alloy with boron composition of 3% and 8% grown by metal organic chemical vapor deposition (MOCVD). A two layer theoretical model has been developed taking into account both thermal and electronic contribution in the photothermal signal allowing to extract the electronic parameters namely electronic diffusivity, surface and interface recombination. It is found that the increase of boron composition alters the BGaAs epilayers transport properties.

Keywords: photothermal defelction technique, two layer model, BGaAs/GaAs alloys, boron composition

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Authors: Waheed Ahmad Safi, Shunichi Nakamura

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Concrete filled steel I-girder (CFIG) bridge was proposed and the bending and shear strength was confirmed by experiments. The area surrounded by the upper and lower flanges and the web is filled with concrete in CFIG, which is used to the intermediate support of a continuous girder. Three-dimensional finite element models were established to simulate the bending and shear behaviors of CFIG and to clarify the load transfer mechanism. Steel plates and filled concrete were modeled as a three-dimensional 8-node solid element and steel reinforcement bars as a three-dimensional 2-node truss element. The elements were mostly divided into the 50 x 50 mm mesh size. The non-linear stress-strain relation is assumed for concrete in compression including the softening effect after the peak, and the stress increases linearly for concrete in tension until concrete cracking but then decreases due to tension stiffening effect. The stress-strain relation for steel plates was tri-linear and that for reinforcements was bi-linear. The concrete and the steel plates were rigidly connected. The developed FEM model was applied to simulate and analysis the bending behaviors of the CFIG specimens. The vertical displacements and the strains of steel plates and the filled concrete obtained by FEM agreed very well with the test results until the yield load. The specimens collapsed when the upper flange buckled or the concrete spalled off. These phenomena cannot be properly analyzed by FEM, which produces a small discrepancy at the ultimate states. The FEM model was also applied to simulate and analysis the shear tests of the CFIG specimens. The vertical displacements and strains of steel and concrete calculated by FEM model agreed well with the test results. A truss action was confirmed by the FEM and the experiment, clarifying that shear forces were mainly resisted by the tension strut of the steel plate and the compression strut of the filled concrete acting in the diagonal direction. A trail design with the CFIG was carried out for a four-span continuous highway bridge and the design method was established. Construction cost was estimated about 12% lower than that of a conventional steel I-section girder.

Keywords: concrete filled steel I-girder, bending strength, FEM, limit states design, steel I-girder, shear strength

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Authors: Roland Tolulope Loto, Cleophas Akintoye Loto, Abimbola Patricia Popoola

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The inhibiting action of 2-dimethylamine on the electrochemical behaviour of austenitic stainless steel (type 304) in dilute hydrochloric was evaluated through weight-loss method, open circuit potential measurement and potentiodynamic polarization tests at specific concentrations of the organic compound. Results obtained reveal that the compound performed effectively giving a maximum inhibition efficiency of 79% at 12.5% concentration from weight loss analysis and 80.9% at 12.5% concentration from polarization tests. The average corrosion potential of -321 mV was obtained the same concentration from other tests which is well within passivation potentials on the steel thus, providing good protection against corrosion in the acid solutions. 2-dimethylamine acted through physiochemical interaction at the steel/solution interface from thermodynamic calculations and obeyed the Langmuir adsorption isotherm. The values of the inhibition efficiency determined from the three methods are in reasonably good agreement. Polarization studies showed that the compounds behaved as cathodic type inhibitor.

Keywords: corrosion, 2-dimethylamine, inhibition, adsorption, hydrochloric acid, steel

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Authors: Alper Akin, Ibrahim Aydogdu

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This study presents a hybrid metaheuristic algorithm to obtain optimum designs for steel space buildings. The optimum design problem of three-dimensional steel frames is mathematically formulated according to provisions of LRFD-AISC (Load and Resistance factor design of American Institute of Steel Construction). Design constraints such as the strength requirements of structural members, the displacement limitations, the inter-story drift and the other structural constraints are derived from LRFD-AISC specification. In this study, a hybrid algorithm by using teaching-learning based optimization (TLBO) and harmony search (HS) algorithms is employed to solve the stated optimum design problem. These algorithms are two of the recent additions to metaheuristic techniques of numerical optimization and have been an efficient tool for solving discrete programming problems. Using these two algorithms in collaboration creates a more powerful tool and mitigates each other’s weaknesses. To demonstrate the powerful performance of presented hybrid algorithm, the optimum design of a large scale steel building is presented and the results are compared to the previously obtained results available in the literature.

Keywords: optimum structural design, hybrid techniques, teaching-learning based optimization, harmony search algorithm, minimum weight, steel space frame

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Authors: Alaa Al-Mosawe, Riadh Al-Mahaidi

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Carbon fiber reinforced polymers have been wildly used to strengthen steel structural elements. Those structural elements are normally subjected to static, dynamic, fatigue loadings during their life time. CFRP laminate is one of the common methods to strengthen these structures under the subjected loads. A number of researches have been focused on the bond characteristics of CFRP sheets to steel members under static, dynamic and fatigue loadings. There is a lack in understanding the behavior of the CFRP laminates under impact loading. This paper is showing the effect of high load rate on this bond. CFRP laminate CFK 150/2000 was used to strengthen steel joint by using Araldite 420 epoxy. The results showed that applying high load rate has a significant effect on the bond strength while a little influence on the effective bond length.

Keywords: adhesively bonded joints, bond strength, CFRP laminate, impact tensile loading

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Authors: A. Chellil, A. Nour, S. Lecheb , H. Mechakra, L. Addar, H. Kebir

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This paper present a mechanical characteristics on fatigue crack propagation in Aluminium Plate based on strain and stress distribution using the abaqus software. The changes in shear strain and stress distribution during the fatigue cycle with crack growth is identified. In progressive crack in the strain distribution and the stress is increase in the critical zone. Numerical Modal analysis of the model developed, prove that the Eigen frequencies of aluminium plate were decreased after cracking, and this reduce is nonlinear. These results can provide a reference for analysts and designers of aluminium alloys in aeronautical systems. Therefore, the modal analysis is an important factor for monitoring the aeronautic structures.

Keywords: aluminum alloys, plate, crack, failure

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Authors: Ming-Wei Wu, Yu-Jin Tsai, Ching-Huai Chang

Abstract:

Liquid phase sintering (LPS) is a versatile technique for achieving effective densification of powder metallurgy (PM) steels and other materials. The aim of this study was to examine the influences of 0.6 wt% boron on the microstructure and LPS behavior of boron-alloyed 410 martensitic stainless steel. The results showed that adding 0.6 wt% boron can obviously promote the LPS due to a eutectic reaction and increase the sintered density of 410 stainless steel. The density was much increased by 1.06 g/cm³ after 1225ºC sintering. Increasing the sintering temperature from 1225ºC to 1275ºC did not obviously improve the sintered density. After sintering at 1225ºC~1275ºC, the matrix was fully martensitic, and intragranular borides were extensively found due to the solidification of eutectic liquid. The microstructure after LPS consisted of the martensitic matrix and (Fe, Cr)2B boride, as identified by electron backscatter diffraction (EBSD) and electron probe micro-analysis (EPMA).

Keywords: powder metallurgy, liquid phase sintering, stainless steel, martensite, boron, microstructure

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Authors: Rahma Tibigui, Ikram Hadj Said, Rachid Belkada, Dalila Hammoutene

Abstract:

The vulnerability of industrial facilities is highly concerned with multiple risks from corrosion. The commonly adopted solution is based on the use of organic inhibitors, which are gradually being replaced by environmentally friendly organic inhibitors. In our work, we carried out a quantum chemical study based on the Density Functional Theory (DFT) method at the B3LYP/6-311G (d,p) level of theory. The inhibitory performance of a derivative of the tetrazole molecule has been investigated and reported as a carbon steel-friendly corrosion inhibitor in hydrochloric acid (HCl) medium. The relationship is likely to exist between the molecular structure of this compound as well as its various global reactivity descriptors, and its corrosion inhibition efficiency, which was examined and then discussed. The results show low values of ΔE, which represent strong adsorption of the inhibitor on the steel surface. Moreover, the flat adsorption orientation confirmed the great ability to donate (accept) electrons to (from) steel, fabricating an anchored barrier to prevent steel from corrosion.

Keywords: eco-friendly, corrosion inhibitors, tetrazole, DFT

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Authors: Sachin S. Patil, Mohan I. Mehta, Sandip J. Sutar, Akshay B. Patil, Shreyas S. Kirwai, Suresh Arangi

Abstract:

MnS is the most commonly found inclusion in steel, which is desirable for machinability of alloy steels but only up to a certain limit, beyond which it weakens fatigue properties of steel. In present work, the effect of sulfur content and its inclusions on the fatigue behavior of AISI 4140 steel is studied (sulfur content 0.002% and 0.016%). Metallurgical analysis, Mechanical testing and Rotating Bending Fatigue (RBF) test were carried out. With the increase in sulfur content, ductility and toughness of the material decrease significantly and large scatter is observed in UTS and impact energy values. From the results of RBF testing, it can be observed that increase in sulfur content from 0.002% to 0.016% has a negligible effect on the endurance strength of AISI 4140 for similar hardness level. Fractography analysis was carried out to study the failure modes in testing.

Keywords: AISI 4140, sulfur content, MnS inclusion, rotating bending fatigue

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Authors: Iting Chiang, Cheng-Yu Wei, Chin-Teng Kuo, Po-Sheng Hsu, Yo-Lun Yang, Yung-Chang Kang, Chien-Chon Chen, Chih-Yuan Chen

Abstract:

In recent years, it is reported that microalloying of nitrogen atoms within traditional Cr-Mo-V hot work tool steels can achieve better high temperature mechanical properties, which thus leads to such metallurgical approach widely utilized in the several commercial advanced hot work tool steels. Although the performance of hot work tool steel can be improved better by alloy composition design strategy, the influence of processing parameters on the mechanical property, especially on the service life of hot work tool steel, is still not fully understood yet. A longer service life of hot work tool steel can decrease the manufacturing cost effectively and thus become a research hot spot. According to several previous studies, it is generally acknowledged the service life of hot work tool steels can be increased effectively as the steels possessing higher hardness and toughness due to the formation and propagation of microcracks within the steel can be inhibited effectively. Therefore, in the present research, the designed experiments are primarily to explore the synergistic effect of nitrogen content and austenitization conditioning on the mechanical properties of hot work tool steels has been conducted and analyzed. No matter the nitrogen content, the results indicated the hardness of hot work tool steels increased as the austenitization treatment executed at higher temperature. On the other hand, an optimum toughness of hot work tool steel can be achieved as the austenitization treatment performed at a suitable temperature range. The possible explanation of such metallurgical phenomenon has been also proposed and analyzed in the present research.

Keywords: hot work tool steel, Cr-Mo-V, toughness, hardness, TEM

Procedia PDF Downloads 59