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welding
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Spot Resistance Welding of St12 and HSLA Steels in Different Thicknesses
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amirhosein (Supervisor) ; Ekrami, Aliakbar (Supervisor)
Abstract
High-strength low alloy (HSLA) E275 developed specifically for automotive application. Also St12 Steel is used in autobodies. On the other hand the resistance spot weld of dissimilar materials is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. The influence of the primary welding parameters affecting the heat input such as; current and time on the morphology, fracture mode, microhardness, and tensile shear load bearing capacity of dissimilar welds between HSLA E275 steel and St12 steel in two different thicknesses (1,2 mm) has been investigated in this study which consisted six group. The...
Dynamic Analysis of a Novel Hybrid Robot for Arc Welding Process
, M.Sc. Thesis Sharif University of Technology ; Zohoor, Hassan (Supervisor)
Abstract
This thesis presented kinematic and dynamic analysis of a novel 8-DOF hybrid manipulator. The hybrid robot manipulator under consideration consists of a parallel robot which is followed by a serial mechanism. The parallel mechanism has three translational DOFs, and the serial mechanism has five DOFs, so that the overall degrees of freedom are eight. The introduced manipulator has a wide workspace and a high capability to reduce the actuating energy. The inverse and forward kinematic solutions of the manipulator were described in closed form. The theoretical results were verified by a numerical example. Inverse dynamic analysis of the robot was presented by utilizing the Iterative...
Effect of Electromagnetic Stirring on GTAW Weld Solidification Structure of AA5052
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Conventional defects in GTAW welding of Aluminum 5052 alloy are the decrease in weld zone strength because of grain growth, formation of columnar grains in the fusion line, solidification cracks and porosities. In this work, effect of strong field electromagnetic stirring on solidification structure of 5052 alloy and elimination of GTAW defects have been investigated. For arc welding processes (especially tungsten inert gas welding), a process called magnetic stirring was proposed, patented, and investigated in the 1970s. The essential aim was to improve weld quality and they indicated that the the Lurentz force is cause of weld stirring. In the earlier researches, alternating magnetic field...
Heat Transfer Modelling and Mechanical Properties Of Wide-Gap Thermite Rail Welds
, Ph.D. Dissertation Sharif University of Technology ; Kokabi, Amir Hossain (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
Wide-gap aluminothermic rail welds with root opening of 60 mm were produced using plain carbon steel rail and non-alloy aluminothermic charge. Such process can repair defective rails, each with only one wide-gap weld instead of using a relatively long plug rail and two standard welds which reduces number of welds in railways and cause saving in money. Required equipments including metallic and sand molds, crucible and self-tapping thimble were designed. Mechanical properties and micro-structure of rail welds and corresponding heat affected zones as well as impact energies and fracture toughnesses of welds were investigated. Wide-gap aluminothermic rail welds exhibited 98% and 95% of yield...
Reliability Study of Steel Welded Joints after Post-Weld Heat-Treatment and Shot-peening
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
Welding as one of the widespread joining techniques, is used in shipbuilding industries, steel bridges, water and gas pipelines, and offshore structures. Also, fatigue plays the major role in more than 90% of welded joints failure. Furthermore, their unserviceability due to failure can incur severe monetary consequences. Unlike deterministic approach, utilizing reliability methods in addition to failure and retrofit cost modeling, enable decision making under uncertainty which leads to an optimal decision. The objective of this research is to create a reliability model of weldedjoints after post-weld heat-treatment and shot-peening using related and reliable experimental data. For this...