EFFECT OF WELDING PARAMETERS ON MECHANICAL PROPERTIES OF FRICTION STIR WELDED ALUMINIUM ALLOY 1100

Abstract

Friction Stir Welding is considered to be the most remarkable and potentially useful welding technique for several materials, such as Al-alloys, Mg-alloys, brasses, Ti-alloys, and steels. However, during FSW process using inappropriate welding parameters can cause defects in the joint and deteriorate the mechanical properties of the FSW joints. Effect of process parameters :tool rotational speed , weld speed , shoulder pin diameter, on the weld process is determined by co – relating the process parameters with mechanical properties such as tensile strength ,hardness at weld nugget , hardness at thermo mechanically affected zone, temperature at weld nugget and temperature at thermo mechanically affected zone. The design matrix was prepared on the basis of 3 factors , 2 levels , full factorial design. Response surface methodology was used to develop the mathematical models co relating the process parameters with the mechanical properties. The models once developed were checked for adequacy using ANOVA technique. From the adequate models the significant terms were selected using p test. The finally proposed models contains only the significant terms. Main and interaction effects of the process variables on the mechanical properties are presented in graphical form . the developed models can be used for prediction of important mechanical properties and control the weld quality by selecting appropriate process parameter values. Use of artificial neural network for modelling of the friction stir welding process was done. Artificial Neural Network architecture , using back propagation algorithm was developed which provided satisfactory outputs. Comparison of the performance of the RSM Models and the ANN Model was also done and it was concluded that the when number of factors are less , RSM yields more satisfactory results. This thesis is divided into 8 chapters. The first chapter discusses the objective and motivation of the problem , followed by the statement of the problem and lastly the plan of investigation , which was undertaken to achieve the objectives. The next chapter gives an insight regarding the research work which has been carried out in related fields such as ANN Modelling RSM application to welding problems , metallurgical investigations etc., chapter 3 gives a brief introduction to the concepts of FSW , ANN , RSM and weld metallurgy followed by the experimental procedures undertaken to carry out the project work . chapter 4 discusses the development of mathematical models . it is followed by chapter 5 where in discussions of the effects of the process variables on mechanical properties are done . chapter 6 is dedicated to use of ANN for modelling of the FSW process . A comparison of the 2 modelling approaches is also done. Chapter 7 discusses metallurgical effects after welding. Chapter 8 discusses results and conclusions drawn from this study . KEYWORDS