Simulation of the tube drawing process using the finite element method

The power law and the Ramberg-Osgood constitutive equations are commonly used for describing material behavior. The Ramberg-Osgood equation is the more popular one as it is capable of describing behavior of several materials over the entire range of deformation. Previous research revealed, however, that the Ramberg-Osgood equation is not capable of describing the behavior of materials which exhibit sudden changes.; One of the goals of this research was to develop a more accurate and efficient way of describing materials behavior. This goal has been achieved as a new equation, called the Alpha constitutive equation, has been developed. This equation is very accurate and efficient as well due to the ability of one equation being able to describe the behavior of any material—even materials that exhibit strain softening.; The second phase of this research focused on developing a finite element program to simulate the tube drawing process which involves large plastic deformation and complicated boundary conditions. A specialized code to simulate the tube drawing in the presence of a mandrel has been developed. This finite element program has the ability to accept materials data in the form of a modified Ramberg-Osgood equation as well as the Alpha equation. A special technique was devised and implemented in the finite element program to avoid instability that tends to occur at the die exit.; The finite element simulation results achieved in terms of the prediction of the drawing force compares well with the results obtained by Ontario Hydro Technologies. In addition, experiments conducted at Ontario Hydro revealed the formation of shear cracks on the outer surface of the tube. The finite element simulation results are consistent with this observation as the results indicate that maximum shear stress does exist at the outer walls of the tube which is responsible for the formation of shear cracks.; The FEM program developed has the added advantage of having the capability to determine the stresses under unsteady state (transient) conditions. In addition, the residual stresses in the material can be determined.; This research work is far from over—it is only the beginning of a very promising step to reach the goal of being able to use mathematically simulations to accurately simulate tube forming processes.