SIMULATION OF METAL FORMING PROCESSES. Konstantin SOLOMONOV a, Victor SVIRIN b

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1 SIMULATION OF METAL FORMING PROCESSES Konstantin SOLOMONOV a, Victor SVIRIN b a Moscow State University of Railway Engineering (Voronezh branch), 75а, Uritskogo street, , Voronezh, Russia, konssol@list.ru b Moscow Institute of Steel and Alloys, 4, Leninsky Prospect, , Moscow, Russia, v_svirin@mail.ru Abstract Problem of metal forming can be solved by applying different methods of simulation. Division by means of simulation rather conventional and does not have clear boundaries, as often one way is the basis of or includes the other. For full automation of simulation and forecasting of plastic deformation of the material in metal forming processes, as well as structural solutions and technological issues is advisable to establish a program complex that includes the following components: intellectual, implemented in the form of an expert system; infological consisting of DBMS; proper simulation, as well as digital libraries, full of information design and technology nature. Intellectual and infological blocks can be attributed to the first level of simulation, and mathematical, geometric, analog and physical simulation for the second level. Ways to simulation the first level is used to solve ill-structured, information and logical problems. To solve problems structured using methods of simulation the second level. Such problems include the simulation of materials processing. To solve the complex problems of plastic deformation, which include the processes of metal forming, sometimes you want to engage all the methods of simulation. For the simulation of plastic forming workpiece developed software PARSHTAMP that uses the «sand analog». It allows you to portray: the contour of workpiece, the dividing line of metal flow, the pattern of metal flow, the profile of the ribs, a spatial diagram of contact stresses. Compared with the known application packages, bases for the finite element method, software PARSHTAMP based on analytical relationships, and therefore easy to learn and use, does not require large computing resources, has a high speed. Keywords: the spatial diagram of contact stresses, the dividing line of metal flow, flow line 1. REVIEW Recently, much attention is paid to the development of various methods of simulation. A significant number of mathematical models that take into account many parameters (temperature, strain rate, rheology, etc.), creates the prerequisites for precise description of the plastic deformation of metal. Increased capabilities of computer technology make it possible to obtain a solution for problems of this kind quickly and effectively, presenting it in a fairly easy to read and analyse the form of a simulation model with intelligent interface. This greatly simplifies and enhances the design and technology, allowing them to choose the appropriate options for the design and procurement tool. Important are the computer programs, based on numerical methods. These programs have in recent years are widely used in forging and stamping and other business enterprises in our country and abroad and play a major role in the software market. To develop and optimize technologies and tools from the beginning of 1990 in the stamping industry began to apply computer programs based on finite element method (FEM). The first versions of the programs allow you to simulate a plane and axisymmetric deformation, and since the

2 mid 1990's the opportunity to calculate the full three-dimensional deformation. Value of developed software products have always been largely defined by the accuracy of the calculated results. There have been two major drawbacks of most programs that use the FEM as a model for numerical implementation: a considerable amount of time spent on clearing operations, which is associated with greater opportunities into account a set of parameters that characterize the process and, consequently, more complicated mathematical model, difficulties in training users, predictably follow from the thesis - the greater the opportunities inherent in the program and the more functions it can perform, the more difficult to master it. The results of simulation and numerical calculations are the basis for the design, as process and tool, and in some cases, and procurement. The solution of these problems can be achieved by using different methods (types) of simulation (Fig. 1). The division of the types of simulation quite arbitrarily and has no clear boundaries, because sometimes one way is the basis of or includes the other. Thus, it is difficult to separate unambiguously computer simulations on numerical and visual (graphic). Strictly speaking, the geometric simulation is part of the mathematical and highlighted here in a separate types just because the basis set of graphic software. Simulation intellectual infological mathematical geometrical analogue physical computer analytical graphic Fig. 1. Types of simulation For full automation of simulation and forecasting of plastic deformation of the material in the processes of metal forming (MF), as well as structural solutions and technological issues is advisable to establish a program complex that includes the following components: intellectual, implemented in the form of an expert system; infological consisting of a DBMS; proper simulation, as well as digital libraries, full of information design and technology nature. Intellectual and infological blocks can be attributed to the first level of simulation, and mathematical, geometric, analog and physical simulation for the second level. Ways to simulation the first level is used to solve ill-structured, information and logical problems. To solve problems structured using methods of simulation the second level. Such problems include the simulation of materials processing. To solve the complex problems of plastic deformation, which include the processes of metal forming, sometimes you want to engage all the methods of simulation. Methods of simulation processes MF described in general terms in [1]. A significant share of total manufactured workpieces obtained in the process of MF, are workpiece with a developed «thin» blanket and the ribs. 2

3 2. MATHEMATICAL MODEL Mathematical model describing the deformation of a thin layer of metal to the theory of flow of a thin plastic layer (TFTPL) [2]. Due to a number of assumptions, this theory gives an approximate picture of the metal flow. It is very convenient for constructing a visual picture of the flow of metal when it is necessary to obtain not quantitative and qualitative characteristics of the process. The essence of the assumptions referred to represent two conditions: the condition of complete plasticity, in accordance with which the shear stresses are zero, and the kinematic condition, which consists in the equality of the transverse flow velocity of particles in the layer. Then the spatial diagram of contact stresses (SDCS) represents the surface of the same slope, all the generators which are inclined to the plane of contact at the same angle. It remains to add the boundary conditions and friction conditions, and the system can be considered closed. In the case where a simple circuit (eg, square) and the boundary conditions are homogeneous (eg, free of sediment), the boundary curve of contact pressures is a side of the same height. To get SDCS on this deck is necessary to construct the surface of the same slope, which in this case is a pyramid (fig. 2, a). Projection onto the plane crests SDCS contact - the dividing lines of metal flow, (DLMF), in this case the diagonal of the square (fig. 2, b). Projection of lines skate it the flow lines (FL). Then on the FL are equidistant from the contour of forgings. In the case of inhomogeneous boundary conditions, FL orthogonal is not really a conditional loop, whose shape depends on the boundary pressure. а b Fig. 2. The model of forging of workpiece: a) SDCS; b) the pattern of metal flow For parts with complex shapes, which are used in engineering, construction DLMF no easy task. It requires a lot of experience and time-consuming. To solve this problem using different methods of geometric simulation. 3. GEOMETRIC SIMULATION The analytical form of the problem of constructing DLMF can be formulated by means of differential geometry. However, an analytical solution in general form is difficult. For this problem, it is easy to find private solutions. For example, when the contour is an ellipse. If we assume that any circuit can be approximated by straight lines and circular arcs, then all of a variety of options can be reduced to four: straight-line, straight-circle, two circles, the circumference of a circle. During plastic deformation, this corresponds to precipitate a rectangular plate with two circular cutouts and a round plate with a round neckline. If you build it DLMF means of analytic geometry as the projection of the ridges SDCS, then in this case we get the same results, namely, line of intersection of two conical surfaces is either 3

4 an ellipse or a hyperbola, which follows from the solution of algebraic equations. The same problem can be solved by methods of descriptive geometry, using the method of auxiliary cutting planes, and get an identical solution. 4. ANALOGUE SIMULATION In the case where the shape of the contour is very complicated, and get a decision in other ways is difficult, you can use the analog simulation. SDCS in accordance with TFTPL shape similar to a sand mound. For the simple mounds (cone, pyramid), the solution is obvious and does not require the production models. However, for complex mounds such a method can be regarded as the only means of visual solutions. This method is convenient because the solution always exists and it is unique. 5. COMPUTER SIMULATION Computer simulation today is considered the most productive and powerful way to model that integrates and numerical and graphical methods. TFTPL formed the basis for software system PARSHTAMP, implemented in an environment of visual programming DELPHI. Program complex PARSHTAMP may be a vivid demonstration of possibilities of automation of engineering calculations and computer simulations. Program complex PARSHTAMP, designed to calculate the parameters of the forging and the forging and modeling of plastic deformation of billets consists of three major programs that provide the solution of static, kinematic and dynamic problems. The solution of the static problem is consistent with the principle of the shortest normal, according to which the metal to flow along the plane of contact radiotherapy directed orthogonally to the contour of forgings. In this case DLMF is the locus of points equidistant from the contour details, or equidistant. This scheme is called the normal flow of metal. The solution of the kinematic problem is based on the principle of least perimeter, through which could be adopted pseudo-radial flow diagram of the metal, which is characterized by the fact that radiotherapy directed orthogonally to some arbitrary curve, which is a level line on the surface of the contact pressure. Then the metal flows along the radius of a circle, called a conditional loop. Dynamic problem is reduced to constructing SDCS, which is a combination of conical and polyhedral surfaces. And in projection on the plane of contact edges of the surface are the dividing lines of metal flow and the line slope the flow lines. To simulate SDCS and DLMF comfortable enough known software COMPAS. Firstly, it is easy to learn, and secondly, squeezing a solid model on a flat circuit occurs so that all generators are derived surface tilted at an angle to the plane of the circuit. Consequently, the solid model is the surface of the same slope, similar in form SDCS. In the transition to drawing the horizontal projection of this model depicts DLMF. 6. PHYSICAL SIMULATION Physical simulation allows you to test theoretical results in practice. In an industrial environment for the complete formation of forgings are often not enough effort press, used in a particular enterprise. Then apply one of the technological approaches - technological recess. As you can see on the models obtained in the COM- PAS (fig. 3, a), the volume model SDCS workpiece with a hole much smaller than without the notch. Therefore, the efforts of the press requires less. Also, the use of technological notch affects the flow pattern of the metal, as seen from the simulation results in PARSHTAMP (fig. 3, b). Technology neckline makes the formation of stiffeners more uniform. Shown here has been stamped on the forging press 150 MN on one of the enterprises in Russia. During the stamping technology cutout «slammed» as seen in the photo (fig. 3, c). 4

5 а b c Fig. 3. The results of the simulation: a) in COMPAS, b) in PARSHTAMP; c) in the industry Comparison of results obtained in the COMPAS and PARSHTAMP shows good coincidence with the physical experiment. In general, the example of solving the problem of shaping a thin workpiece, we looked at all methods (types) of simulation presented in our proposed classification. LITERATURE [1.] SOLOMONOV, K., KOSTAREV, I., ABASHKIN, V. Simulation of the processes of bulk stamping and forging slabs. Moscow: Publishing House of MISA, p. [2.] ILYUSHIN, A. Plasticity. Moscow: State Publishing House of technical literature, p. 5