a new method of friction welding and estimation of its residual stress

there are some disadvantages in using fusion welding methods which make the engineers to think about substitution of the new methods instead of the traditional ones a major drwback in fusion welding is that the fatigue behavioir of the welded part decreases because of tensile residual stresses which remain during producing process one of the best methods that make less residual stress is friction welding inthis paper a new type of friction welding method is presented to produce a special type of thermostat it needs to join a pin and a cap shaped part by welding which has been done by spot welding previously in order to obtain better product the ultrasonic effects are mixed with friction welding method. one end of the part is vibrated by using a piezoelectric band. the final process is done by the head of a three axis CNC milling machine .