Investigation on tailored blanks in a full forward extrusion process of sheet-bulk metal forming

Due to the ongoing technological development, the demand for geometrically complicated high performance parts with great functional density is increasing. Often, the use of sheet metal is a beneficial approach in manufacturing technology to meet the requirements on components regarding material strength and lightweight construction goals. The forming of therefore required complex sheet metal part geometries with integrated functional elements cause the need for a three dimensional material flow. Sheet-bulk metal forming, characterized by the application of bulk forming operations on sheet metals, is a suitable approach to produce such components. A challenge is the material flow control, resulting in an insufficient die filling of the functional elements. The use of tailored blanks with a defined sheet thickness distribution is an auspicious approach to face this challenge in subsequent forming processes. In the presented work, semi-finished products with a continuous thickness profile manufactured by orbital forming are applied in a full forward extrusion process. By an additional implementation of a heat treatment, the tailored blanks undergo a recrystallization process that causes a softening of the strain hardened material. In this paper, the potential of a heat treatment in the process class of sheet-bulk metal forming is shown by characterizing the geometrical and mechanical properties of the functional components by applying the mild deep drawing steel DC04 with an initial sheet thickness of t0 = 2.0 mm.

Towards an holistic account on residual stresses in full-forward extruded rods

An holistic view is attempted towards prediction of the effect of residual stresses induced by full-forward extrusion on fatigue life of workpieces during operation. To study the effect of constitutive model on the accuracy of forming simulations, a combined nonlinear isotropic/kinematic hardening model as well as the isotropic hardening part of the same model are calibrated based on five compression-tension-compression uniaxial stress experiments. A full-forward extrusion finite element model is developed adapting both the aforementioned hardening plasticity models and the predicted residual stress states at the surface of the workpiece are compared against that of a corresponding forming experiment. Results show residual stress predictions of remarkable accuracy by the FE-models with the isotropic hardening model. The effect of residual stresses on fatigue life of the workpiece is qualitatively studied by uncoupled multiscale simulations featuring gradient crystal plasticity at the microscale. While the effective (homogenized) macroscale response indicates elastic response during a macroscopically cyclic loading, plasticity accompanying reduction of residual stresses is still present at the microscale within, e.g. grain boundaries.

МОДЕЛЮВАННЯ ПРОЦЕСІВ КОМБІНОВАНОГО РАДІАЛЬНО-ПРЯМОГО ВИДАВЛЮВАННЯ СКЛАДНОПРОФІЛЬОВАНИХ ПОРОЖНИСТИХ ДЕТАЛЕЙ ІЗ ВИКОРИСТАННЯМ МЕТОДУ КІНЕМАТИЧНИХ МОДУЛІВ

Expanding the capabilities of the kinematic modules method to determine the value of the relative deformation pressure and shaping of a semi-finished product in the processes of combined radial-forward extrusion such as hollow parts with a complex profile. Obtaining calculated dependencies that will allow predicting compliance with the required dimensions of the part and assessing the possibility of defect formation. Upper bound method based on the method of kinematic modules is defined investigation of the main factors, affecting the power mode of deformation and features in the shaping of a semi-finished product in the processes of combined extrusion with several degrees of metal flow freedom Based on the upper bound method by using a kinematic module with two degrees of metal flow freedom is determined the value of the relative deformation pressure for make scheme of combined radial-forward extrusion such as hollow parts with a complex profile. The dependences of the increments in the semi-finished product that make it possible to analyze the influence of technological factors in the process of shaping and possible defect formation in the form of dimple are determined. The possibilities of the upper bound method by using kinematic modules with several degrees of metal flow freedom to assess the power mode and shaping of a semi-finished product in the processes of combined extrusion are determined. Significant influence of friction conditions and geometric parameters of the process the appearance of dimple in combined radial-forward extrusion such as hollow parts with a complex profile are considered. Mathematical relationships for calculating the value of the relative deformation pressure and increments of the semi-finished product in combined radial-forward extrusion such as hollow parts with a complex profile that will contribute to a more active introduction of combined extrusion processes in production are determined.

Analysis of power parameters of combined three-direction deformation of parts with flange

The upper bound power method is used to simulate the process of combined radial-backward-forward extrusion of hollow parts of the "cup with flange and branch pieces" type from a continuous workpiece. The calculation scheme with autonomous deformation zones is used, which contains modules with an inclined boundary and the condition for the equality of powers acting on both sides of the intermediate hard zone is accepted. This made it possible to more accurately determine the power regime and the prevailing direction of the metal flow, which is necessary to assess the character of the forming of the part. The comparison of theoretical and experimental values of the deformation pressures and the flow velocities with each other, as well as with the results obtained by the finite element method shows the feasibility of using the obtained functions for technological calculations of power parameters and evaluating of part forming.