Design and Analysis of Molybdenum Super Alloy FSW Tools

Abstract

Friction stir welding is an exciting process for welding two pieces of material together as it doesn’t require weld preparation, operates at low temperatures with absences of fumes, is environmentally friendly, energy efficient and can be used by only semi-skilled personnel to produce a satisfactory weld. This project emphasizes on some current uses, variations in tool design, improved welding techniques and new tool materials being developed for the welding of more difficult aluminium alloys to give increased tool life. The tool (made of molybdenum super alloy), its pin profile, shape and dimensions plays a vital role in making the weld joint. In FSW, the stress distribution of tool pin is affected by the thermo mechanical characteristics of the work piece. In this present work, three tools with different pin shapes (Conical, Cylindrical and Frustum) were designed with and without threads in their profiles. Initially the tools dimensions are based on the base material plate thickness taken in to consideration, the induced structural stresses were checked with in the permissible stress limits. The tools were modeled in CATIA and analysis is performed in ANSYS software for exploring stress distributions and displacement vector sum in the pin, at different speeds and temperatures. The frictional force between the tool shoulder and work piece is considered for simulating the stress and displacement vector in the pin profiles. The vonmises stress distributions in pin profiles, displacement vector sum of the pin profiles, are obtained from ANSYS software and the pin with optimum strength is determined.