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

E Karabegović,M Mahmić,E Husak,I Karabegović

doi:10.5755/j01.mech.19.6.6012

Abstract

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 philoso-phy, 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 work-piece 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 thick-ness.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 de-scribes 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.DOI: http://dx.doi.org/10.5755/j01.mech.19.6.6012

Highlights

This paper provides researches and analyses of hydroforming of thin-walled tube elements [1,2,3,4,5,6,7,8,9,10]
In metal processing with hydroforming, the friction between a die and workpiece significantly influences on a material flow and presents the crucial parameter in determining of work pressures in hydroforming process
The conditions of the contact friction are constantly changing during the hydroforming process and present a complex analytical problem, which complicates obtaining of a reliable mathematical friction model

Summary

Friction influential zones in tube hydroforming

The metal forming processes implies processing without cutting removal, giving the material a wanted shape by using different methods of plastic forming. If analytical models of friction coefficient determining in hydroforming between the workpiece and die by authors [13, 14] are analysed, it can be concluded that the solutions for friction coefficient μ take into account the increase of the contact pressure caused by load on outer diameter, while solutions [14] assuming that the stresses are in contact of the tube and die (σk)σk = puc doesn't take into account. Analyzing the friction between the tube and the die in hydroforming differently than the above authors analyzed, we come to the new analytical model for friction coefficient determination in hydroforming of thin-walled tube elements. We come to the new analytical model of the friction coefficient between the workpiece and die for thin-walled tube elements which is very significant for hydroforimng processes: puc x Ase Bs0e sym (5)

B C n sym

Conclusions

Summary