In this paper, we describe the mechanisms responsible for the forming of rectangular bars and tubes extruded through inclined dies by numerical simulations and experiments. We carried out simulations and experiments of rectangular bars and tubes at various exit positions and extrusion ratios. The calculated trend of curvature showed good agreement with experimental results. From this reason, the validity of the numerical simulation was concluded. Curvature generation mechanisms were elucidated on the bases of simulation outputs related to the distributions of the material exit velocity and dead metal area. The turn direction differs according to the difference in exit position and the curvature increases with extrusion ratio as observed from the analytical results. The generation of dead metal area and the configuration of the container used affect the curvatures of curved rectangular bars and tubes.
A new method of springback compensation for a hat-shaped beam based on finite element (FE) simulation and the optimization technique is presented, in which the objective function to be minimized is the shape error of the press-formed beam after springback and the design variables are the geometrical parameters for defining the die shape. This method starts with rough die compensation based on empirical knowledge and springforward analysis, and then optimization is carried out. To reduce the computation time in optimization, the idea of two-step optimization is presented, where the die cross-sectional shape and longitudinal die curvature are determined separately. In addition, a partial FE model, which is less expensive computationally, is used in die cross-sectional shape optimization, instead of a full FE model. In this paper, we describe the general method of die compensation, the formulation of the optimization problem, details of the numerical technique, and the verification of this method by solving a springback problem for the beam model.
The use of aluminum sheets is a powerful means of reducing the weight of cars and domestic electric appliances. However, because spot welding causes several problems in joining aluminum sheets, mechanical joining is required. Mechanical clinching is a method of mechanical joining with excellent features with regard to productivity, energy saving, and recycling efficiency. However, there is a problem associated with the low peel strength of mechanical clinching. The purpose of this research is to improve the peel strength of mechanical clinching. In this research, an experiment and a simulation are performed using a stripper plate with a ring projection instead of a flat stripper plate. The material used in the experiment is a sheet of aluminum A5182 with a thickness of 1 mm. The main results are as follows: 1) Interlock angle increases when the stripper plate with ring projection is used. 2) Peel strength increases when interlock angle is increases. 3) The increase in interlock angle occurs because a stripper plate with a ring projection pushes the material into a die cavity and prevents it from flowing out.
In recent years, the coupled vibration problems with mechanical and control systems have been observed with the development of high-response machines. To design a high-performance and reliable machine, an accurate method of evaluating dynamic characteristics is highly required. In this paper, an evaluation scheme for torsional natural frequency is presented as an example of a hot rolling mill drive system. To improve the current mechanical vibration analysis model, an FEM code considering control is developed. Work stiffness isn’t typically considered in an analysis model, but we demonstrate that work markedly affects the torsional frequency and suggest its estimation method.
In this study, the closing behavior of internal voids was examined by deformation analysis involving the 2-D finite element method (FEM) that imitated voids in steel ingots in the compression process (upset process). In the compression process, a model experiment that uses internal voids is carried out to confirm the accuracy of deformation analysis. By comparing the model experiment with an analytical result, it was confirmed to imitate the internal void behavior by this analysis. The relationship between reduction ratio and void shape/void position was investigated by the analysis. In the forging process, the closing evaluation value of internal voids (Q value) was calculated by a model experiment and 3-D FEM. Using the analysis result, a limited value of the closing behavior of void is quantified, and it is now understood that the void closes at more than Q = 0.21. In addition, the forging process of filling the above-mentioned value was designed by the Taguchi method. The predicted Q value in the case of using the Taguchi method almost corresponds to the value calculated by deformation analysis. It was clarified that the process is capable of being designed simply.
Since cold-roll-formed rings generally have a complex in cross-sectional shape, their metal flow has not been explained well by 2-D CAE analysis. The analysis requires long computational time in the case of applying full Lagrangean mesh. In this study, the peripheral speeds of rolls and rings in the rolling of grooved rings were measured experimentally. 3-D CAE analysis was applied to ring rolling with an ALE (Arbitrary Lagrangean Eulerian) mesh, where a nondeformed area was excluded from the calculation. The predicted velocities of the rolls and rings showed good agreement with the experimental results and the predicted diameter growth also showed good agreement with the result obtained using Hayama’s equation. ALE makes calculation time shorter than a half of that with the Lagrangean mesh.
The endless hot rolling concept was introduced to meet demand for diverse hot-rolled steel sheet products produced by a cost-effective process compared with the conventional batch-type process. Endless rolling involves joining the head and tail ends of two bars following their rough rolling. By applying solid-state joining utilizing the high temperature of the joined materials for endless hot rolling, a new joining technology was proposed to instantaneously obtain a sound and uniform joint as the base metal using a relatively simple equipment. This report presents type I super deformation joining that obtains a sound joint by incompletely shearing the overlapped materials. In laboratory tests, in the presence of a scale of 14 ∼ 24 μm thickness on the overlapping surface, the joint strength of the center of the joint area was approximately the same as that of the base metal, although reduction of area was smaller than that in the base metal. Obtaining a good joint shape with a small step around the joint area and evaluating the joint properties of wider plates remain as problems to be overcome.