Computer-Simulation of the Billet Shape Change during Helical Piercing

In this paper the task of the study of the deformation during helical piercing of the metal was set and solved with the use of the DEFORM-3D software. Methodology, that allows to calculate the length of helix lead along the deformation zone, as well as determine for each lead absolute and relative reduction, the width of the contact area and the metal strain refinement indicator was developed. Based on the developed methodology application the following variation regularities were established: helix lead length (li), quotient reduction (Δr/r0), ratio of the billet radius to the width of the contact area (r0/b), as well as the length of the billet contact surface (l0) with the roll in dependence of the feed angle (β), the roll number of revolutions (N) and the plug nose advancement over the gorge (Cg).

Route Effects in I-ECAP of AZ31B Magnesium Alloy

An AZ31B wrought magnesium alloy was processed by incremental equal channel angular pressing (I-ECAP) using routes A and BC. Despite the fact that the measured grain size for both routes was very similar, the mechanical properties were different. Tensile strength was improved using route A comparing to route BC, without ductility loss, while tension-compression anisotropy observed for route A was significantly suppressed when using route BC. Moreover, billet shape evolution resulting from subsequent passes of I-ECAP was studied. Significant distortion after processing using route BC and no occurrence of such effect for route A were observed. Results of a finite element analysis showed that non-uniform strain rate sensitivity might be responsible for different billet shapes. The conclusion is drawn that processing route has a strong influence on the billet shape and mechanical properties when processing magnesium alloys by I-ECAP.

Numerical and Experimental Studies on Extrusion of Fan-Shaped Shell of Magnesium Alloy

This paper presents a case study of optimizing the forming process for a fan-shaped shell component. Numerical simulation was used to study the backward extrusion process of a fan-shaped shell. The underfill defect produced at the opening of the extruded shell due to the billet shape was solved and the minimal base thickness required to avoid the presence of the underfill defect at the bottom corner of the component was defined through the numerical simulation. The extrusion drawing and forming process of the fan-shaped shell were designed on the basis of the results of the numerical simulation. Forming experiments had been performed on the fan-shaped shell at 380 °C and cracking was found on the outside wall in the center of the extruded shell. Choked groove on the inner wall of the die and reducing the lubrication had been used to avoid the presence of cracking. The fan-shaped shell of AZ31 magnesium alloy has been successfully formed by the three-stage forming process of hot upsetting, hot backward extrusion and cold sizing.

Mathematical Simulation of Billet Profile during Spray Forming Process

The parameters of atomizer were obtained from the experiment. Based on the obtained parameters, a mathematical model was proposed to simulate the growing profile of billet during spray forming. The model included some process parameters which relate to the shape profile such as nozzle data, eccentric distance, rotation speed, withdraw speed and so on. After being compared with the billet shape of experiment, we got good consistent results between the simulation and experiment, it was found that the results of the simulation is in good consistent with that of the experiment.

Preform Design of Powder Metallurgy Turbine Disks Using Equi-Potential Line Method

In a material hot forging process, rational preform design not only ensures that metal flows properly in die cavity and that final products have excellent quality, but also reduces tooling cost. In the present work, it is proved in theory that the differential equation of electric potential (∇2ϕ=0) in the electrostatic field is similar to the differential equations of velocity potential function (∇2φ=0) and velocity stream function (∇2ψ=0) in velocity field during the material forming process, with all three represented in the form of the Laplace equation. Moreover, the material flow in the plastic stage and the energy in electrostatic field all meet the least-energy principle. Therefore, according to the similarity criteria, an equi-potential line (EPL) method is proposed for the design of the preform shape in material hot forging. Different voltages are applied to the billet shape and the final product shape to generate a proper electrostatic field. One optimal equi-potential line is selected among the innumerable equi-potential lines as the basic shape of the preform shape and is processed into the preform shape following a three-step procedure. The preform design by the EPL method is compared with that by the traditional industrial method. The results show that the proposed method for preform design is feasible and reliable for practical applications.