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This paper presents the influence of beam incidence angle on austenitic stainless steel sheet subjected to a high density laser beam having Gaussian power density…
This paper presents the influence of beam incidence angle on austenitic stainless steel sheet subjected to a high density laser beam having Gaussian power density distribution. Bead‐on trials are conducted on 3.15 mm thick commercial AISI 304 austenitic stainless steel sheet using a Nd:YAG laser source with a maximum output of 2kW in the continuous wave mode. The effects of beam incident angle on the weld bead geometry are studied using finite element analysis. Experiments are conducted with 600, 1000 and 1400W laser power and 800, 1400 and 2000mm/min welding speed. A three dimensional finite element model is developed for the simulation of non‐linear transient thermal analysis of the weld bead geometry for different beam incident angles using the finite element code ANSYS. The result reveals that by increasing the beam incident angle with constant beam power and welding speed, there is a considerable reduction in the depth of penetration‐to‐width ratio (d/w). Further, it is noticed that the process enters into conduction mode of welding from the keyhole mode of welding as the beam angle is increased beyond 10o. The comparison of the simulation results and the experimental data for weld bead geometry with different beam incident angles show good agreement.
Friction stir welding (FSW), a process that involves joining of metals without fusion of filler materials. It is used already in routine, as well as critical application…
Friction stir welding (FSW), a process that involves joining of metals without fusion of filler materials. It is used already in routine, as well as critical application for the joining of structural components made of Aluminum and its alloys. Indeed it has been convincingly demonstrated that the process results in strong and ductile joints, some times in systems, which have proved difficult using conventional welding techniques. The process is most suitable for components that are flat & long (plates & sheets) but it can be adapted for pipes, hollow sections and positional welding. The welds are created by the combined action of frictional heating and mechanical deformation, due to a rotating tool. Recently, a new technology called friction stir spot welding (FSSW) has been developed that has a several advantages over the electric resistance welding process widely used in automotive industry in terms of weld quality and process efficiency. This welding technology involves a process similar to FSW, except that, instead of moving the tool along the weld seam, the tool only indents the parts, which are placed on top of each other. The conditions under which the deposition process in FSSW is successful are not fully understood. However, it is known that only under specific thermo‐mechanical conditions does a weld formation occur. The objective of the present work is to analyze the primary conditions under which the cavity behind the tool is filled. For this, a fully coupled thermo‐mechanical three‐dimensional FE model has been developed in ABAQUS/Explicit using the adaptive meshing scheme and the Johnson‐Cook material law. The contact forces are modeled by Coulomb’s law of friction, making the contact condition highly solution dependent. Temperature graph in the radial direction as well as stress, strain plots are presented.
Vehicle weight reduction represents a viable means of meeting tougher regulatory requirements designed to reduce fuel consumption and control greenhouse gas emissions…
Vehicle weight reduction represents a viable means of meeting tougher regulatory requirements designed to reduce fuel consumption and control greenhouse gas emissions. This paper aims to present an empirical and comparative analysis of lightweight magnesium materials used to replace conventional steel in passenger vehicles with internal combustion engines. The very low density of magnesium makes it a viable material for lightweighting given that it is lighter than aluminium by one-third and steel by three-fourth.
A structural evaluation case study of the “open access” Wikispeed car was undertaken. This included an assessment of material design characteristics such as bending stiffness, torsional stiffness and crashworthiness to evaluate whether magnesium provides a better alternative to the current usage of aluminium in the automotive industry.
The Wikispeed car had an issue with the rocker beam width/thickness (b/t) ratio, indicating failure in yield instead of buckling. By changing the specified material, Aluminium Alloy 6061-T651 to Magnesium EN-MB10020, it was revealed that vehicle mass could be reduced by an estimated 110 kg, in turn improving the fuel economy by 10 per cent. This, however, would require mechanical performance compromise unless the current design is modified.
This is the first time that a comparative analysis of material substitution has been made on the Wikispeed car. The results of such work will assist in the lowering of harmful greenhouse gas emissions and simultaneously augment fuel economy.
The gas tungsten arc welding (GTAW) process is a widely used process that produces quality weldments. But the high heat generation from the GTAW arc can cause extreme…
The gas tungsten arc welding (GTAW) process is a widely used process that produces quality weldments. But the high heat generation from the GTAW arc can cause extreme temperatures as high as 20,000°C. The residual stresses and deformations are high accordingly. One of the methods for decreasing residual stresses and deformations is to change the welding pattern. In the literature, there are not so many examples of modeling dealing with welding patterns. This paper aims to investigate the influence of welding patterns on the deformations.
In this work, back-stepping patterns and partitioning of the weld line were investigated and the distortions and residual stresses were calculated. By doing this, temperature-dependent thermophysical and thermo-mechanical material properties were used. The temperature distribution and deformation from experiments with the same welding conditions were used for validation purposes.
Seven different welding patterns were analyzed. There is only one pattern with a single partition. There are three patterns investigated for both two and three partitioned weldings. The minimum deformation and the optimum residual stress combination is obtained for the last pattern, which is a three partitioned and diverging pattern.
The most important aspect of this paper is that it deals with welding patterns, which is not much studied beforehand. The other important thing is that the structural part and the thermal part of the simulation were coupled mutually and validated according to experiments.