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Lakshminarayanan, A. K.
- Evaluation of Micro Structure and Tensile Shear Load of Friction Stir Spot Welded Automotive Steel
Authors
1 Department of Mechanical Engineering, SSN College of Engineering, Kalavakkam, Chennai, IN
Source
Manufacturing Technology Today, Vol 12, No 8 (2013), Pagination: 17-22Abstract
Low alloy low carbon steels are extensively used for automotive applications mainly due to their good impact resistance, specific strength and formability. Electrical Resistance Spot Welding (ERSW) is currently used as a method of joining sheet metal together in automotive industries. Generally materials of similar thickness are blanked, preformed and then welded together to make parts like automobile door, bodies and number of similar parts. ERSW process is relatively faster, but it involves large amounts of current to make joints and cooling equipment to keep the electrode in normal working temperature. Friction stir spot welding (FSSW) is a relatively new type of welding process, which is a derivative of friction stir welding. In this process, a rotating tool is plunged in to the material under high force to create a bond. Joints are made by FSSW process and the macrostructure, microstructure and lap shear tensile strength of these joints are characterized. The metal flow during FSSW process is investigated on samples to gain better understanding of welding mechanisms. The results of the lap shear tensile test indicated that the combination of 900 rpm, 0.18mm plunge depth and 20s dwell time yielded a maximum lap shear tensile strength of 5.9 KN.Keywords
Friction Stir Spot Welding, Automotive Steel, Lap Shear Tensile Test.- Understanding the Role of FSW Process Parameters on Strength Properties of Ferritic Stainless Steel Joints
Authors
1 Centre for Materials Joining & Research (CEMAJOR), Dept. of Manufacturing Engg., Annamalai University, Annamalai Nagar, IN
Source
Manufacturing Technology Today, Vol 10, No 2 (2011), Pagination: 10-18Abstract
The effect of rotational speed, welding speed and tool shoulder diameter on the tensile and impact properties of AISI 409M ferritic stainless steel joints made by friction stir welding are investigated. The experiments were conducted based on three-factor five-level central composite rotatable design and empirical relationships were established between the process parameters (rotational speed, welding speed and tool shoulder diameter) and quality characteristics (tensile strength and impact toughness) of friction stir welded ferritic stainless steel joints. Furthermore, the numerical multiobjective optimisation was used to optimise the friction stir welding process parameters.Keywords
Ferritic Stainless Steel, Tensile Strength, Impact Toughness, Optimisation.- Process Parameter Selection for Friction Stir Welding of Cast A413 Aluminium Alloy Using Taguchi Experimental Design
Authors
1 Dept. of Mechatronics Engg., Kongu Engg. College, Perundurai, Erode, IN
2 Dept. of Mechanical Engg., Coimbatore Institute of Technology, Coimbatore, IN
3 Centre for Materials Joining Research (CEMAJOR), Dept. of Manufacturing Engg., Annamalai University, Annamalai Nagar, IN
Source
Manufacturing Technology Today, Vol 7, No 12 (2008), Pagination: 3-10Abstract
This paper discusses the use of Taguchi technique for maximizing the tensile strength of friction stir welded cast aluminium alloy A413. The experiments have been conducted using Taguchi's experimental design technique. The friction stir welding (FSW) process parameters namely tool rotational speed, welding speed, axial force play a major role in deciding the weld quality. The effect of process parameters on tensile strength is evaluated and the optimum welding condition for maximizing the tensile strength is determined. The analysis of variance and the signal to noise ratio of robust design are employed to investigate the influence of process parameters on the tensile strength of friction stir welded A413 aluminium alloy. To correlate the process parameters and the measured tensile strength, a mathematical model has been developed by multiple linear regression analysis. The developed mathematical model is found to be very useful for predicting the tensile strength of friction stir welded A413 aluminium alloy.- Optimization of Friction Stir Welding Process Parameters to Weld Cast A356 Aluminium Alloy Taguchi's Design of Experiments Approach
Authors
1 Mechatronics Engg., Kongu Engineering College, Perundurai, Erode, IN
2 Mech.Engg., Coimbatore Institute of Technology, Coimbatore, IN
3 Centre for Materials Joining Research, Manufacturing Dept., Annamalai University, IN
Source
Indian Welding Journal, Vol 41, No 2 (2008), Pagination: 34-41Abstract
This paper presents an application of Taguchi's Design of Experiments, to identify the optimum setting of process parameters to maximize the tensile strength of friction stir welded cast A356 aluminium alloy. The quality of weldments in friction stir welding (FSW) process mainly depends on the factors such as tool rotational speed, welding speed and axial force. Taguchi's orthogonal array L27, signal to noise ratio (S/N) and Analysis of Variance (ANOVA) are used to find the optimum levels and the effect of process parameters on tensile strength. To correlate the process parameters and the measured tensile strength, a mathematical model has been developed by multiple linear regression analysis. The mathematical model is found to be very useful to predict the tensile strength of friction stir welded cast A356 aluminium alloy. The optimum conditions to get maximum tensile strength are tool rotation speed of 1000 rpm, welding speed of 75 mm/min and axial force of 5 kN.
Keywords
Friction Stir Welding, Cast Aluminium Alloy, Tensile Strength, Taguchi Design, Regression Analysis.- Developing Empirical Relationships to Predict Diffusion Layer Thickness, Hardness and Strength of Al-Cu Dissimilar Joints
Authors
1 Centre for Material Joining & Research, Manufacturing Dept., Annamalai University, IN
2 Mech. Engg, Pondicherry Engineering College, Pondicherry, IN
Source
Indian Welding Journal, Vol 41, No 3 (2008), Pagination: 37-45Abstract
The principal difficulty when joining Aluminium (Al) and commercial grade Copper (Cu) lies in the existence of formation of oxide films and brittle intermetallics in the bond region. However, diffusion bonding can be used to join these alloys without much difficulty. Temperature, pressure and holding time are the three main variables, which govern the integrity of the diffusion bonds. The experiments were conducted based on three factors, five-levels, and central composite rotatable design with full replications technique. Empirical relationships were developed to predict diffusion layer thickness, hardness, strength of Al-Cu joints incorporating process parameters using Response Surface Methodology. The developed relationships can be effectively used to predict the bond properties at 95 % confidence level.
Keywords
Diffusion Bonding, Aluminium Alloy, Commercial Grade Copper, Lap Shear Tensile Strength, Ram Tensile Strength.- Study on Effect of Weld Cooling Rate on Fusion Zone Microstructure and Solidification Cracks in 316L Austenitic Stainless Steel
Authors
1 Department of Mechanical Engineering, SSN College of Engineering, Kalavakkam - 603 110, IN
2 Metallurgy and Materials Group, IGCAR, Kalpakkam - 603 102, IN
Source
Indian Welding Journal, Vol 52, No 1 (2019), Pagination: 56-63Abstract
A study on effect of cooling rate on mode of solidification and microstructure was carried out on austenitic stainless steel welds. A tube and plug of 316L stainless steel was joined using Gas Tungsten Arc Welding (GTAW) and laser welding processes. The welds were characterized using optical and Scanning Electron Microscope (SEM). The results indicate that cooling rate of the weld has significant effect on solidification mode, microstructure and solidification cracking. 316L weld joints prepared using GTAW process shows duplex microstructure of vermicular ferrite and austenite in the fusion zone. Whereas, the fusion zone of laser joint shows only single phase austenite microstructure. From these observations, it is clearly understood that the changes observed in the fusion zone microstructures of GTAW and laser welds are due to change in the mode of solidification as a result of change in the weld cooling rates. The predicted mode of solidification for GTA welds for 316L composition used in this study was Austenite-Ferrite (AF) and it was also confirmed through the microstructural observations. In laser joint, the weld has solidified in fully austenitic mode which deviates from the mode of solidification predicted by the conventional constitutional diagrams and hence modified weldability diagram was used. From this investigation, it was also found that the rapid solidification during laser welding is not completely partition less because segregation of sulphur was found using Scanning Electron Microscope – Energy Dispersive Spectroscope (SEM-EDS) along the dendrite boundaries of laser welds. High cooling rate during weld solidification which influences fully austenitic mode of solidification and micro segregation of impurities along the grain boundaries contribute to solidification cracking of welds in laser joints.
Keywords
Solidification Mode, Solidification Cracking, Cooling Rate, Energy Dispersive Spectroscopy, Laser Welding, Gas Tungsten Arc Welding.References
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