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چكيده انگليسي :

Simulation Of The Influence Ultrasonic Osillation On The Tube Hydroforming Process Using Finite Element Method Mehdi Zarei m zarei@me iut ac ir Date of Submission 2011 10 13 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mahmood Frazin farzin@cc iut ac irAbstractTube hydroformig process is a new method of metal forming that has been become one of the ways of theindustry Tube hydroforming is a manufacturing process which applies controlled internal pressure andAxial feed to expand the tube to desired shapes The main advantages are part consolidation weight reduction fewer secondary operations and tighter tolerances However it has disadvantages due to manyvariables such as loading paths material formability and tribological conditions which limit its applicabilityand influence parts failure excessive thinning wrinkling buckling or bursting This process has also some drawbacks such as slow cycle time expensive equipment and lack of extensiveknowledge base for process and tool design In order to increase the implementation of this technology in thestamping industry some issues need to be addressed the preparation of the tubes material selection andquality of the incoming tube pre form design and production method application of computer simulations selection of effective lubricants and enhancement of the tribological performance and improvement of theformability of the tube The main advantages are part consolidation weight reduction fewer secondary operations and tightertolerances This research presents ultrasonic technology as a method of improving formability and tribologicalconditions The superimposing of ultrasonic oscillations was already proved to have benefits for other metalforming processes such as reduction in the forming load and frictional stresses No attempts have been madeto investigate on the effects of ultrasonic oscillation the tube hydro forming process Therefore in order toadvance the understanding of the mechanism of ultrasonic tube hydroforming the finite element method wasused The ABAQUS code was used for the FEM Finite element method was used to approximate the ultrasonic pressure and to design a set of tooling forultrasonic process at 20 kHz The results were compared with conventional tube hydroforming In theaxisemetric model the effects are related with the changing of the frictional conditions at the diespecimeninterface The kinematics of sliding varies and the friction force when superimposing the ultrasonicoscillations reverses the direction for every period of oscillations Due to this friction force reversal thefriction force will oppose the forming process only during a half of the oscillations and it will help during theother half The result will be a decrease 15 precent in forming load and also increasing in the final tubediameter For plain strain model in conventional process the tube is expanded under internal pressure in the presenceof friction In the ultrasonic process vibrations are imposed on the die resulting inalternating gaps at thedie tube interface The gaps open and close after each oscillation When the internal pressure is maintained the corner radius obtained is smaller The reduction in the corner radius was between 6 8 and 11 4 Moreuniform thickness and less thinning as well as smaller corner radius indicate improvement of the formabilityof the material Key Words finite element method tube hydroforming ultrasonic oscillations

زارعي، مهدي

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