Date of Graduation

1997

Document Type

Dissertation/Thesis

Abstract

Numerical modelling simulations of two dimensional tube extrusion and three dimensional tube pilgering reduction of nickel-base alloys were conducted using a commercial finite element code, DEFORM{dollar}\\sp{lcub}\\rm TM{rcub}{dollar}. Accuracy of the finite element modelling results was verified quantitatively by comparing solid extrusion simulation results with experimental data. An interface frictional coefficient was also examined and the best fit was selected for the simulation. As expected, heat loss of the extruded material was found to be significant due to temperature-dependent material properties of the alloy. A sequence of selected FEM tube extrusion simulations using DEFORM{dollar}\\sp{lcub}\\rm TM{rcub}{dollar} were carried out and based on an isoparametric interpolation scheme, the numerical results were used to establish a predictive formula which can be used to predict extrusion load and exit temperature with given processing variables (tube dimensions, ram speed and initial billet temperature). Accuracy of the predictions was also verified. Based on the numerical simulation results and the predictive extrusion formula, limit diagrams of a specific alloy were then established. For the three dimensional tube pilgering reduction simulation, possible defect formation was inspected and adjustment of processing variables such as feed rate or side relief was suggested to avoid defect formation. Good correlation was observed between defect formation identified by the pilgering simulation and actual processing defect. Also, effect of material property and feed rate was examined and optimum choice of processing variables (geometry, tool setup or feed rate) was proposed. The methodology presented in this research provides a practical way to tube manufacturers to avoid costly trial and error runs of initial setup for tube production as well as optimize tube production process.

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