RESEARCH INTO THE BULGE FORMING OF A TUBE UNDER AXIAL-RADIAL COMPOUNDFORCES AND ITS APPLICATION

In this paper the results of experimental research into a new approach for the bulge forming of a metal tube using polyurethane is presented . In this approach, bulging is executed, accompanied by the applicatio n of external forces that provide an axial compressive load acting on the base of the tube wall and counter-pressure against the bulged part . This method improved greatly the state of stress in the metal and ra ises the forming limit. A universal device was designed for this study , which can investigate the bulge forming of items such as a tee-junct ion and a four-way junction, as well as rotationally-symmetric items. Moreover, the axial force and the counter-pressure can be added either on their own or in conjunction. Some test results relating to the for ming of a tee-junction using this technology are presented and the upp er-bound method is used for predicting the total forming load. Further , equations for the calculation of the values of relevant quantities i n the bulging operation are deduced. Finally, examples of items formed successfully in production are presented.