FINITE ELEMENT SIMULATION OF HEAT TRANSFER IN FRICTION STIR WELDING OF AL 7050

Friction welding is widely used in various industries. In friction welding, heat is generated by conversion of mechanical energy into thermal energy at the interface the work pieces during pin rotation under pressure. A three-dimensional thermo mechanical simulation of friction stir welding (FSW) processes is carried out for Aluminium Alloys of 6061and 7050 where the simulation results are compared directly with the measured temperature histories during FSW after process. The objective of the present work is to study and predict the heat transient generated in alloy aluminium plate welded by FSW method. A three dimensional model was developed by LS-Dyna software and heat cycles have been proposed during the welding of aluminium alloys 6061 and 7050. In this research, the simulations were carried out with linear velocity in the range of 140 to 225 mm/min and pin rotational speeds of 390 and 500 rpm. Increase in pin rotational speed, from 390 to 500 rpm, resulted in greater temperatures which translated to rise of recorded temperature of top and bottom of the specimens. This is in turn to a wider HAZ. In addition, it was observed that raising the linear velocity had an opposite effect. Finally, results of experimental and numerical data were correlated and validate

FINITE ELEMENT SIMULATIONS OF HEAT TRANSFER IN FRICTION STIR WELDING OF AL 6061

Friction stir welding (FSW) is a process in the solid state in which heat is generated due to friction between welding tool and work piece. FSW has extensive effect on the microstructure, weld quality, and mechanical properties. The purpose of this investigation is to study and to predict the heat generated in Aluminum alloy plates welded by FSW method. A three dimensional model was developed by LS-Dyna software, using finite element method. An appropriate heating cycle has been proposed for aluminum 6061 alloy. The investigated parameters in this study were linear velocity and rotational velocity. Finally, results from numerical and experimental data was compared and verified

Microstructural evolution in friction stir welded API 5L-X52 steel

Abstract: Welded API-5L steel pipes have been extensively used in the oil industry. One of the major parameters affecting the mechanical properties is the grain size, which is altered with the joining method. In this paper microstructural evolution in the friction stir welded API 5L-X52 steel pipes has been investigated.Specimens were cut from a 2mm thick API 5L-X52 steel pipe. The steel sheets were then joined by friction stir welding process; at a linear speed of 100 mm/min. The tool rotational speed was varied from 400 to 800 rpm. Samples were then evaluated using tensile test, metallographic and hardness measurements. Microstructural investigations revealed the stir zone, heat affected zone and thermo mechanically affected zones. Heat input in the stir zone led to the formation of elongated austenite grains which were transformed to fine ferrite and pearlite grains and widmanstatten ferrite in certain regions. Plastic deformation and recrystallization enhanced the hardness and tensile strength as well as toughness of the welded joint in the API 5L-X52 steel

Durability of E-glass vinyl ester composite structures and their modeling in ABAQUS

The use of fiber-reinforced polymer composite materials (FRP) in various applications such as aerospace, automotive, sports equipment, and oil and gas industries has been growing in recent years. Nonetheless, the potential use of FRP pipes in harsh environmental conditions of oil and gas industry-related applications could become significantly greater if there was minimal degradation to the mechanical and physical properties of the materials used to form the pipes. The feasibility study of this potential, however, requires several systematic investigations for assessing the long-term durability of glass fiber-reinforced polymer composite pipes. This paper presents results from our preliminary investigation on the response of E-glass/Vinyl ester composite pipes aged in water and seawater at various temperatures. Scanning electron microscopy is used to assess the material’s response, and ABAQUS simulations are used to assess the capacity of the modeling software to predict the moisture absorption process in E-glass/Vinyl ester composites using a diffusion module. As the results obtained in the experiments and ABAQUS simulations have good agreement, ABAQUS can be used to simulate the long-term durability of E-glass/Vinyl ester composite pipes exposed to humid environments

Effects of moisture absorption on degradation of E-glass fiber reinforced Vinyl Ester composite pipes and modelling of transient moisture diffusion using finite element analysis

The main purpose of this study is to investigate the effects of humidity and temperature on the properties of GFRP specimens. Tubular specimens fabricated by a filament winding machine are submerged in the studied environment and the accuracy of Fick’s law on moisture diffusion behaviour is studied. The results prove that decreasing the exposure temperature reduces the diffusion coefficient and absorbed moisture. To analyse the effects of moisture uptake on mechanical and physical properties, buckling tests and scanning electron microscope were used. ABAQUS is employed to simulate the moisture absorption. The outcome shows good agreements between experimental and FEA results

Influence of Parameters of Quenching and Partitioning Process on Microstructure and Fraction of Retained Austenite

Certain amount of retained austenite can increase ductility of steels because of the TRIP phenomenon during plastic deformation. One method for achieving this is partitioning of carbon into austenite to stabilize it at room temperature. The quenching and partitioning (Q&P) heat treatment leads to a microstructure consisting of martensite and stabilized retained austenite between martensite plates, which provides a better combination of strength and ductility. In this study, the effect of parameters of Q&P process (quenching temperature, partitioning temperature and partitioning time) on the microstructure and retained austenite volume fraction of a low alloy medium carbon steel was investigated. The results showed that the high increase in partitioning time causes the disappearance of martensite blades and reduction of austenite volume fraction. However, increasing of partitioning temperature made the retained austenite films become thicker and its volume fraction increase. On the other hand, by increasing the quenching temperature, carbon content of retained austenite increased sharply

The influence of Ni addition and hot-extrusion on the microstructure and tensile properties of Al-15%Mg<inf>2</inf>Si composite

The effects of nickel addition and hot-extrusion on the microstructure and tensile properties of in situ Al-15%Mg2Si composite specimens have been investigated. Al-15%Mg2Si composite ingots were prepared by an in situ process and different amounts of nickel (0.1, 0.3, 0.5, 1.0, 3.0 and 5.0wt% Ni) were added to the remelted composite. Optical microscopy (OM) and scanning electron microscopy (SEM) indicated that Ni addition changes the morphology of both primary and eutectic Mg2Si phases and decreases the size of primary Mg2Si particles from 42μm to 17μm. Hot-extrusion was found to be powerful in breaking the eutectic network and changing the size and morphology of pseudo-eutectic Mg2Si phase. The results obtained from tensile testing revealed that both Ni addition and hot-extrusion process improve ultimate tensile strength (UTS) and elongation values. Fracture surface examinations revealed a transition from brittle fracture mode in as-cast composite to ductile fracture in hot-extruded composite after Ni addition. This can be attributed to the changes in size and morphology of primary and eutectic Mg2Si phases and also the formation of more and finer α-Al phase. © 2012 Elsevier Ltd

The effect of soda bagasse lignin modified by ionic liquids on properties of the urea–formaldehyde resin as a wood adhesive

International audienceThe aim of this research was to investigate the influence of lignin modified by ionic liquids on physical and mechanical properties of plywood panels bonded with the urea–formaldehyde (UF) resin. For this purpose, soda bagasse lignin was modified by the 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then the various contents of unmodified and modified lignins (10, 15, and 20%) were added at pH=7 instead of second urea during the UF resin synthesis. The physicochemical properties of the prepared resins as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels made with these adhesives were measured according to standard methods. According to Fourier Transform Infrared (FTIR) Spectrometry, by treatment of lignin, the C=O, C–C, and C–H bonds decrease while the content of the C–N bond dramatically increases. Based on the finding of this research, the performance of soda bagasse lignin in UF resins dramatically improves by modification by ILs; as the resins with modified lignin yielded lower formaldehyde emission and water absorption when compared to those made from unmodified lignin and commercial UF adhesives, respectively. The shear strength as well as wood failure percentages are lower for the panels produced with modified lignin than for the panels produced with UF resins alone