Conventional Friction Stir Welding has increased heat generation which results in improper dissolution of precipitates in Heat Affected Zone (HAZ) which develop the weakest section of the weld. In order to dissipate the heat beyond Thermo-Mechanical Affected Zone (TMAZ), spray nozzle with water and compressed air is used in this study. Friction Stir Welding assisted with cooling has been shown to improve the microstructure properties of the weld than normal friction stir welding process (FSW). This is because the grain structures in the nugget zone become finer when water is used as a cooling medium to dissipate the excess heat. Refined grain structure is known to improve the tensile strength and ductile properties of the weld. The welding was carried out using the spray setup at 1000 rpm and 44 mm/min. The flow rate of the nozzle setup was set to 72 ml/min. The tensile behavior of the welded specimen was then tested. The ultimate tensile strength of water cooled was obtained and compared with air cooled weld. Fracture analysis was performed using Scanning Electron Microscope (SEM) and the results are then compared. Microhardness values of various zones were then measured and compared. It was found that the weld obtained with water cooled friction stir welding possesses balanced hardness and tensile properties suitable for real life applications.

In the recent years, nanofluids embarked as a new class of fluids with improved thermophysical properties such as thermal conductivity, thermal diffusivity, viscosity, and convective heat transfer coefficients thus promoting better heat transfer. Nanofluids consists of two-phase system where the nano sized solid phase (nanoparticles) is dispersed into a base fluid. Graphene is a material which has two-dimensional planar geometry with thermal conductivity of the order of 5000 W/mK. Nanoparticles in the form of thin flakes as small as 50 nm, 100 nm has been used in this study. Two step technique is the used method for preparing nanofluids. Inclusion of additives in small quantity, enhance the durability of the nano particles inside the conventional base fluids. The stability of the solid nano particles inside the conventional base fluid is increased by using surfactants. The heat transfer capacity and stability of the fluids are considered as the basic properties for investigation. The nanofluids characterization studies were drawn from the SEM, XRD and thermal conductivity results. Hot wire method was used to determine the thermal conductivity of the nanofluids. The preparation and properties of graphene based nanofluids which can be used as coolant are studied in this work.

No abstract

No abstract

A water cooled holder has been designed to facilitate Friction stir welding of steel, which is not possible now because of the tool material limitations such as high temperature and load gradients , excess heat flow. Due to its high melting point, friction stir welding of steel generates very large amount of heat which has deleterious effect on the machine bearing. Deformation and wear of tool, degeneration of spindle bearing are some of the effects of FSW on steel which gradually destroys the whole system. To overcome these defects, a cooling system is needed to manage the heat transfer. A liquid cooled tool holder with a thermocouple, sealing and a coolant is designed and developed that manages heat removal from the tool. This article primarily focuses on the necessity and the layout of water cooled tool holder, selection of coolant and tool material. The results obtained show the increase in feasibility of friction stir welding of steel.