Based On The Tee Of The Elastomer Composite Bulging Technology

As one kind of basis components in many medium and high pressure pipelines, multi-branch tubes are widely used in many fields. And the production of multi-branch tubes has been one of the most difficult processes. Method of welding, machining and casting once being the traditional and main methods, the production of multi-branch tubes has developed into the forming method. The bulging of multi-branch tubes is a non-chip finish process during which the radial expansion happens under pressure. It's a semi-fine/precision forming technology, and belongs to advanced manufacturing technology. In this paper, elastomer of rubber was chosen as bulging medium, and the forming of T-branch tube (which's a typical part of multi-branch tubes) was researched. The bulging process of multi-branch tubes has the characteristics of material nonlinearity, geometric nonlinearity and boundary nonlinearity. Whereas, non-linear explicit finite element analysis program ANSYS/LS-DYNA was selected as the numerical simulation platform, on which the forming processing parameters and loading path were optimized.Processing parameters optimization. Optimization of tubular blank parameters: finite element model of T-branch tube bulging was established, training and testing samples were gained base on the orthogonal design method. Elman neural network was used to establish the prediction model for T-branch tubular blank parameters. And initial tube length, initial wall thickness and die entry radius were chosen as the network input parameters, while the maximum branch length at the guarantee of thinning and thickening rate being no more than 30% as the output parameters. The prediction network was established, trained and tested on the MATLAB software platform. The optimization of parameters resulted to be: die entry radius R=7 mm, initial thickness t=1.5 mm, initial length l0 = 100. Analysis of effect of friction on the forming: friction coefficient between the tube and the die (μ1) and friction coefficient between the bulging medium and the tube (μ2) are analyzed; an evaluation function was inducted, and the optimal combination turned out to beμ1=0.1,μ2=0.35.Loading paths optimization of compound bulging. The execution method and loading path of counter force for compound bulging process were designed. Development of branch height of axial-compressive bulging process versus time was simplified to a linear equation; the initial height of balance punch h0 and velocity of balance punch V3 were considered instead of the imposing of the counter force F3 in loading path designing process and finally the optimal scheme of "h0=6 mm, V3/V1=1, length of the tip of the axial punch l1=5mm" was obtained which induced a relatively ideal component. According to the comparison of wall thickness, stress, strain and branch height between the axial-compressive bulging and the compound bulging, it indicated that slower thinning rate, more uniform thickness and larger branch height could be got from compound bulging, which also proved the superiority of the compound bulging.