The success of the tube hydroforming process is dependent on several parameters such as material properties,friction at the tool/tube interface and loading paths.When plastic instability is reached,the process becomes very sensitive to the change of one or more of these parameters and consequently,less reliable.However,in the hydroforming process,the inception of necking in hydroformed parts does not lead necessarily to failure.Indeed,hydroformed parts can be acceptable,even when they contain a local thinning due to diffuse necking.So,a detailed understanding of post-localization behavior is important to determine hydroforming limits.The reliability of the results obtained by finite element simulation is strongly dependent on the accuracy of the chosen model.In this work,numerical simulations were carried out on a uniaxial tensile test to illustrate the incapacity of the classical elasto-plastic model(Prandtl-Reuss)to reproduce the post-localization behavior.To overcome these difficulties,we show that introducing a strain rate-dependence can be a good manner to obtain regularization.This dependence was taken into account by a specific hardening law.Finite element calculations on a corner fill test with internal pressure were achieved to illustrate the accuracy of the rate-dependent model throughout a comparison with experimental data.
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