In this paper, the effects of theoretical models of materials and dies on finite element (FE) predictions of a hot forging process are presented, to provide process design engineers and researchers with some useful insight into the theoretical approaches on which they rely. The material was assumed to be rigid-viscoplastic or rigid-thermoviscoplastic and the dies were assumed to be rigid or elastic. The problem of die fracture occurring during the hot forging of aluminum fixed scroll was studied. This process is particularly sensitive to theoretical models, mostly because the die-stress component causing the die fracture has a relatively weak relationship with the forming load. A fully thermo-mechanically coupled FE analysis considered die elastic deformation and was first conducted to reveal die fracture with emphasis on the maximum die stress and forming load. The predictions for four simulated cases using different theoretical assumptions of the material and die were then compared. These were also compared with experiments, undertaken to observe the relationship between maximum die stress component and forming load, to reveal the effects of material and die models in FE predictions. The differences in forming load, die stress and their variation with time among the four cases were clarified quantitatively for different die and material models, to provide some insight into metal forming for engineers and researchers.

In this paper, a Mannesmann roll piercing process equipped with Diecher's guiding discs is investigated using a rigidthermoviscoplastic finite elements method with intelligent remeshing capability and tetrahedral elements. The analysis model is presented and the approach is applied to a Mannesmann roll piercing process found in the literature. Details about the remeshing criterion as well as mesh density control are given. The present predictions are compared with the predictions found in the literature, showing that the two predictions are in close agreement in terms of the deformed shape. However, it is emphasized that the present approach has the distinct strength in predicting details of final shape.

In this paper, a useful die system for warm plate forging of a large axle housing of heavy-duty trucks is presented. A die system composed of material flow guide pin as well as upper die and lower die is proposed to reduce the inherent thickness reduction along the bent corner of the product which deteriorates structural strength and fatigue life in its service. The role of the pin assembled in the upper die is to prevent formation of sharp corner in early forming stage and to supply material in the lower die cavity sufficient enough to thicken the bent corner at the final stroke. The mechanism of the die system is given and its effect on corner thickness of the product is revealed by two-dimensional finite element analysis under plain strain assumption. Three-dimensional finite element solutions are also given to verify validity of the two dimensional approach and to show the mechanics of the die system in detail. The die system has been successfully applied to manufacturing the axle housing of heavy-duty trucks.

In this paper, plastic deformation behaviors of ESW105 and SCM435 steels are revealed by simulations and experiments. ESW105 is the special pre-heat-treated steel characterized by high initial yield strength and negligible strainhardening behavior. The flow stresses of the two steels for large stain are calculated from tensile tests. Axial and lateral compressions of cylindrical bars are tested and simulated and the deformed shapes are compared to characterize the plastic deformation behaviors of the two materials. A forward extrusion process of a cylindrical bar is also simulated to reveal the difference. It has been shown that there are pretty much difference in plastic flow between ESW105 and SCM435 which causes from the difference in strain-hardening capability, implying that the experience-oriented design rules for common commercial materials may lead to failure in process design when the new material of ESW105 is applied without consideration of its plastic deformation behavior.