Manabu Kiuchi

Flow Stress, Yield Criterion and Constitutive Equation of Mushy/Semi -Solid Alloys

Abstract New mathematical models of yield criterion and constitutive equations of mushy/semi -solid alloys (hereinafter described as semi -solid alloys) are proposed in order to investigate their flow features and deformation characteristics in various forming and shaping processes. First, a large number of uniaxial compression tests of semi -solid alloys are carried out and their stress -strain curves are measured. Through the tests, the remarkable drop of their flow stress is observed when their solid fraction decreases from 100%. The second, a new formula of yield criterion of semi -solid alloys is proposed. It can express the drop of their flow stress in semi -solid state. In addition, so -called constitutive equations, which describe flow and deformation of such alloys in forming and shaping processes, are derived from the formulated yield criterion. At the last stage, the obtained constitutive equations are introduced to 3D FEM simulation of upsetting of billets.

Application of mushy/semi-solid joining—Part 3

Abstract A process to join glass or stone onto base metal alloys is proposed. The process characteristics allow using various kinds of glasses or stones, such as craft glass, beads, tile, amethyst, agate and hematite with different shapes and sizes. The process utilizes excellent and active join ability of mushy or semi-solid alloy’s properties. In this study, the mechanism of the joining was investigated and some applications were showed. The process itself has several useful properties like: (1) easy-to-operate, (2) ability to get good joining condition, and (3) applicability to a continuous production system. Through the study, it is found that the mushy joining is a useful and valuable manufacturing method for developing and manufacturing glass/metal or stone/metal composites. The mushy joining process is different from the existing cloisonne and enameling process.

Computerized Numerical Simulation of Roll-Forming Process

Abstract A computerized numerical simulation system for cold roll-forming was developed. It was applied to various roll-forming processes of ERW (electric resistance welded) pipes, light gauge section steels, deck-plates and others. Through simulations, effects of pass-schedule, geometry and position of roll, dimension of product and mechanical properties of metal sheet on deformation features of metal sheet at every forming stage, stress and strain occurring in it, roll separating force, roll driving torque and dimensional accuracy of product were clarified. The system is now being used for design and prediction of desirable profiles of forming rolls, roll positions and other operation factors. It is also being successfully used to design pass-schedules for newly requested products.

Mathematical Simulation of Clad Sheet Rolling and Sandtvich Sheet Holling

Synopsis Mathematical models and simulation techniques for clad sheet rolling and sandwich sheet rolling are developed. They are based on the extended upper bound theorem. A series of numerical simulations of clad and sandwich sheet rolling processes are performed. Through simulations, the flow and deformation feature of each sheet (layer) at roll gap, thickness ratio of each layer in rolled clad or sandwich sheet, rolling force, rolling torque and longitudinal curvature of rolled product’ are successfully calculated. The calculated results are compared with the experimental measurements and very good agreement between them are found. It becomes clear that the proposed simulation techniques are useful enough for characterizing the clad sheet rolling and the sandwich sheet rolling. They enable us to obtain systematic knowledges for designing desirable rolling schedule and performing stable operation.

A New Method to Detect Solid Fractions of Mushy/Semi-Solid Metals and Alloys

Abstract A new method to detect so—called solid fractions of mushy or semi-solid metals and alloys is proposed. Firstly, the relationships between electric resistance (or electric potential difference) and temperature in the range from solid—line to liquid—line are measured with respect to binary alloys and multi—component alloys. Secondly, the relationships between solid fractions of mushy or semi-solid binary alloys and their temperatures are obtained by referring their equilibrium phase diagrams. By combining both results, the unified relationship between normalized electric potential difference and solid fraction is obtained for all of the tested binary alloys. This relationship is used to determine the solid fractions of multi—component alloys from their measured normalized electric potential differences. The assumed values are verified by the rapid solidification method.

Overall Thermal Analysis of Hot Plate/Sheet Rolling

Abstract A new scheme of three-dimensional thermal analysis of workpiece temperature and roll temperature in hot plate/sheet rolling is proposed. Mathematical models and numerical analysis are based on a modified finite element method. The results are as follows. (1) The temperature change at each portion of workpiece during hot rolling was calculated in detail. (2) The effects of rolling parameters on the workpiece temperature and roll temperature were consistently clarified. (3) The calculated results were used for process design and process control. (4)They are essential for innovation of hot plate/sheet rolling processes as well as quality control of rolled products.

Computer aided design of rolls for reshaping processes from round pipes to channel-type pipes

Abstract The reshaping of round pipes into non-circular pipes is one of the most important processes in the tube/pipe industry. Due to recent industrial demands, the reshaped products have to satisfy a high level of specifications with accuracy in dimensions and variety of cross-sectional profiles. The design of rolls and pass-schedules, however, are still carried out relying on individual empirical knowledge and judgement, with the consumption of much time and labor. Under a situation like this, some kind of theory, numerical model and simulation method, which can provide reasonable knowledge and data concerning pipes’ deformations, are required for the design of rolls and processes. In this study, a two-dimensional elasto-plastic analysis method is extensively developed to investigate the deformation features of pipes’ cross-sections in reshaping processes from round pipes into non-circular pipes. It has become clear that through systematic numerical analyses of forward and backward deformation based on the developed method, roll-profiles that are suitable for making the required products, can be designed successfully. The developed method is usable to design rolls and pass-schedules for various types of reshaping.

Complex Simulation System of Forging Based on UBET

Abstract Simulation techniques based upon UBET applicable to various deformation features of workpieces in forging processes were developed. Each one of them deals with basic deformation features of workpieces on dies, such as axisymmetric upsetting, bulging, folding, radial expansion, forward and/or backward extrusion, and non-axisymmetric upsetting, radial expansion forward and/or backward extrusion. A complex simulation system of three-dimensional forging processes was built up by combining these simulation techniques. In this system, the workpiece with complicated three-dimensional geometry is divided into several blocks. The deformation of each block is analysed separately using appropriate one of these simulation techniques. The result of analysis about each block is combined with others and they are optimized so as to make the total power of deformation of the workpiece into minimum. This complex simulation system was applied to some cases and its usefulness was verified.

Characterization of Three-Dimensional Metal Flow in Extrusion Process

Abstract This paper presents a rigid- plastic FEM code and describes its application to flew simulation during extrusion with aims to obtain knowledges and information usable for eliminating geometrical defects of products. The effects of some variables like the aspect ratio of products cross section, the bearing length and the position of die opening on the metal flow are studied. Results on the average extrusion pressure and the metal flow characteristics in terms of the velocity distribution profiles in the bearing section and the streamline patterns are presented. From them it is possible to predict the geometric defects of the product and find out the method to reduce them by modification of the die geometry, e.g., bearing length. The extrusion simulation of rectangular and angle sections is chosen to show the applicability.

Mashy-State Rolling of Aluminum Alloys and Cast Irons

Summary Mechanical and metallurgical features of mashy-stare (or mushy-state) rolling processes are investigated. Washy-state rolling of aluminum alloy sheets and cast iron sheets are carried out and effects of rolling conditions, such as solid fraction (weight percentage of solid component) of workpiece and thickness reduction, on flow and deformation characteristics of liquid component and solid component at roll gap, internal structure and mechanical property of rolled sheet are widely investigated. The results are as follows. (1) The rolling force decreases distinctively following to the decrease in solid fraction of workpiece. (2) When the solid fraction of workpiece is low, the solid and liquid components flow separately at roll gap. (3) In that case, the internal structure of rolled sheet differs completely from that obtained by hot rolling. (4) Mechanical properties of aluminum alloys and cast irons may be improved and new type of functional sheets of those metals can be manufactured by the mashy state rolling.