Keyword : Metal forming, finite element analysis, Ansys, elasto-plasticity, cold forging design. Metal forming is a widely used manufacturing process noted for its minimum waste and dimensional precision, and it usually improves the mechanical properties of the formed part. However, the forming sequence of a new design is not a straightforward task, and it requires many trials and adjustments to achieve satisfactory producing conditions.
The empirical "trial and error" method has been traditionally applied to metal forming design, however, this approach is expensive and time consuming. Metal forming analysis can be performed in three modeling scales Koop et al. The first scale is the global modeling, which only predicts process loads or work. Analytical methods are used for this purpose.
Local scale analysis is used to estimate the thermo-mechanical variables such as strain, strain rate, and temperature. With the extensive development in computational mechanics, numerical methods have been used as an economical alternative to perform the local modeling. Micro-scale modeling computes the micro-structural evolution during the forming process. Since global scale analysis is only applicable to simple situations and micro modeling is still incipient and only gives results for specific conditions, local modeling is the most popular approach.
Among other methods, the Finite Element Methods FEM is widely used in metal forming analysis due to its capabilities to model the complicated geometries of tools and parts in forming processes. In this paper, we present two forming problems. Ring compression test and upsetting simulations are presented to demonstrate the capabilities of a finite element commercial software Ansys to aid in metal forming design.
The contact conditions are modeled by the Coulomb law with a penalty method and the multilinear elasto-plastic material model is used. Experiments are carried out to validate the modeling technique. One of the biggest challenges in the metal forming industry is to obtain products in the final shape and properties with minimum machining. Cold forging processes are a viable option for this purpose because the manufactured part needs little machining, small production time, and the products present mechanical strength higher than parts manufactured by other processes.
Cold forging is a process carried out below the recrystallization temperature applied to manufacture small parts with varied geometries and has the following advantages: minimum material waste, mechanical properties improvement, such as yield strength and hardness, which brings as an advantage the use of cheaper materials, very good surface finish, energy economy when compared with hot or warm forging, and tools subjected to less thermal fatigue.
Contact conditions are included to handle contact between tools and dies. The classical Coulomb law [Mielnik, ] is used to model frictional contact and the penalty method [Bathe, b] is applied to avoid penetration. The contact tractions on G c are defined as follows:. The contact term is integrated by co-locational formulation to yield.media.travelenet.com/21-chloroquine-phosphate.php
Finite Element Analysis: Theory and Application with ANSYS, 4e
The elasto-plastic constitutive equation together with contact conditions are used for metal forming analysis. The radial return mapping algorithm is used to compute the stress and internal variables Krieg and Key, , and the consistent tangent operator Simo and Taylor, , which preserves the quadratic convergence rate of the Newton method is also used. The penalty method is applied to impose contact conditions between the contacting surfaces.
The friction is an important factor in forming processes, and it is also responsible for the internal and surface quality of the formed part. In the current formulation friction is modeled by the Coulomb law. Figure 1 shows how a finite element analysis FEA can be used in metal forming design. The FEA can provide detailed information for forming designers such as forming force, defects predictions, flow pattern, and stress concentration in the dies.
The strain output, for instance, can display strain concentration areas to identify the possible early failures in the tools or to predict formability problems. Many forming aspects can be analyzed from simulated solution. For instance, irregular flow, which can cause products internal defects, can be detected from simulation. Elastic deformation of the tools, which should be controlled to maintain desirable tolerances, can be verified in the finite element analysis prediction.
The solution convergence of the method is checked by decreasing the time step, and by increasing the number of nodes of the analysis model. The ring compression test was developed to experimentally estimate the friction coefficient in metal forming operations Male and Cockcroft, The test consists of compressing a ring at different ratios with flat and smooth tools and measuring the final height hf and final internal diameter dif. During compression, the internal and external diameters will change according to the amount of compression and the friction condition on the interface.
Hence, curves relating changes in the internal diameter with respect to the compression ratio characterize the friction coefficient m. The geometrical dimensions of the ring deo: dio : ho initial external diameter : initial internal diameter : initial height are in proportion to The lubricant used in this test is the bisulfide of molybdenum MoS2 , which is widely used in cold metal forming processes.
Due to the axial and radial symmetries, the simulation was made with one quarter of the ring discretized with nodes. Two types of elements were used to model the ring: Visco and Plane42 Ansys - V.
Finite element analysis theory and application with ansys download
III, Contact was modeled with Contact48 element. In Fig. Request a copy. Download instructor resources.
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You have successfully signed out and will be required to sign back in should you need to download more resources. Teaching and Learning Experience This program will provide a better teaching and learning experience—for you and your students. It will help: Present the Theory of Finite Element Analysis: The presentation of theoretical aspects of finite element analysis is carefully designed not to overwhelm students.
Present the Theory of Finite Element Analysis Careful, balanced presentation of theory offers insightinto the theoretical aspects of finite element analysis, without overwhelming students with theory. Enough theoretical background is offered to allow individuals to use ANSYS intelligently and effectively. Mechanical and thermophysical properties of some common materials used in engineering are covered in the appendices.
Introduction to Finite Element Analyisis
A brief review of fundamental principles in solid mechanics, heat transfer, and fluid mechanics is included. Each chapter first discusses the relevant basic theory and then demonstrates it using simple problems with hand-calculations. The last two chapters are devoted to the introduction of design, material selection, optimization, and parametric programming with ANSYS.
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