Analytical model for friction coefficient determination in hydroforming of thin-walled tube elements

Industrial branches where the changes occur with the introduction of the new technologies in a very short period are automobile and aviation industries, because the securing and ergonomic criteria had to be achieved. These demands initialized setting of the new productive philosophy, which is based on a modern production like plastic forming and modelling with an incompressible fluid. A tube hydroforming got a significant role in the last five years and is considered as a technology of rapid development. This paper provides researches and analyses of hydroforming of thin-walled tube elements. A workpiece and die contact for hydroforming in a work process manifests with the friction force which has an influence on: axial force, axial punch feed and workpiece wall thickness. The stress-strain state and their disposition during the tube hydroforming are foundation where the friction influence in tube hydroforming is based on. It provides an analysis of deformation zones and friction in T shape tube hydroforming. An analytical model of friction coefficient change in hydroforming between a tube and die has been carried out. The main objective of this paper is to suggest new analytical model for friction coefficient determination in hydroforming of thin-walled tube elements which describes process the most realistically. This paper provides an experimental way of needle sensor setting in measuring of the contact friction in T shape tube hydroforming.Original Abstract: Naujos technologijos sparciausiai diegiamos automobiliu ir aviacijos pramoneje, nes jos yra siejamos su saugumo ir ergonomikos kriterijais. Sie reikalavimai paskatino kurti nauja gamybos filosofija, kuri siejama su modernia gamyba - plastiku formavimu ir modeliavimu nespudziais skysciais. Vamzdziu hidraulinis formavimas ypac paplito per pastaruosius penkerius metus ir laikomas sparciai besivystancia technologija. Siame straipsnyje pateikiami plonasieniu vamzdziu elementu tyrimu ir analizes rezultatai. Kontaktuojant ruosiniui ir presui hidraulinio formavimo metu pasireiskia trinties jegos. Tai vercia analizuoti T formos vamzdzio deformacijos formavimo metu zonas. Pasiulytas trinties tarp vamzdzio ir preso koeficiento pokycio analitinis modelis. Sio straipsnio tikslas - pateikti naujo trinties koeficiento nustatymo formuojant plonus vamzdziu elementus analitinio modelio israiska, kuri realiausiai apibudintu procesa. Straipsnyje aprasomas adatinio jutiklio irengimo, matuojant kontaktine trinti T formo