Modelo numérico basado en el método de los elementos finitos para el estudio de la hidrodinámica de Avelino Samartín at Universidad Politécnica de Madrid. Optimización de mallas bidimensionales en elementos finitos. Article (PDF Avelino Samartín at Universidad Politécnica de Madrid. Avelino Samartín. 16 dez. We are pleased to announce that we will have soon, also in EAD, the course of Dynamic Finite Element Analysis by the NCE/Prof. Dr. Avelino.
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Exploració per tema “Elasticitat”
The stamping is a process of mechanical forming very used in the industry by facilitating the obtaining of products with several formats, good mechanical properties and finishes or semi-finishes. The computational simulation using the finite elements method has shown a great importance in the lasts years. Make a parametric program means, to develop a procedure that builds a model in function of its parameters or variables.
When makes a parametric program it happens a drastic decrease in the necessary time to define the variables of the stamping process and the construction of the simulation model.
Stamping, Delphi, Parametric, Finite Elements. The use of programs of computational simulation, in the forming of sheets, has show a great increase in the last decade, with prominence for programs that use the finite elements method, becoming an important tool in the optimization the real processes.
The finite elements method considers the structure divided in parts or elements that are not infinitesimal, united to each other in nodes points, where they are supposed concentrated whole the connection forces among the elements.
The solicitations and deformations concentrated in the nodes. The elastic and mechanical behavior of each element can have such simple mathematical expression with relationship to the one of the infinitesimal elements of the classic solution. The composition of those elements of finite size, to build the considered structure, gives place easily to a system of equations calculated by matrix way. This work has the objective of elaborating a parametric program that has as purpose: The construction of a model of finite elements consists of the making the geometry, the mesh, the application of the loads and displacement conditions and the solution of the model.
The parametric is written in some text editor, ex. ANSYS will read and load the parametric automatically, not being necessary any type of the dinitos intervention. Making of the Parametric The construction of a parametric program can be accomplished following some steps that are: The manual modeling of the simulation: This file contains the command lines used in the construction of the model.
Identification the variables of the model: These variables will be the parameters of the model. Insert equations and programming routines: Can be used programming routines with APDL language ex.: The Figure 1 shows a simplified flowchart contends the necessary stages to build a parametric program.
In this parametric program were used the elements VISCO for the sheet and a rigid element with just a superficial mesh for punch, die and blank-holder. Manual build of the simulation. Identification of the command lines that will be substituted by parameters ex.: Insert the parameters and adjustment of the command lines.
Insert equations and programming routines. Figure 1 Steps by build of the parametric model. The element is defined by eight nodes with three degrees of freedom each node. The use of this element needs the use procedures of incremental solutions, because is applied to simulation elemeentos nonlinear behavior.
In the stamping process, the deformations and failures happen mainly in the sheet, the tools was considered a rigid body being just applied a superficial mesh where it will happen the contact with the sheet, being controlled by a pilot node, where the conditions of loads and displacement of these components will be concentrated. We used three pairs of contact: The Figure 2 shows the pairs of contact. In the die, the displacements and rotations are impeded in all the directions.
The pressure applied blank-holder is accomplished in a uniform way. The progress of the punch is accomplished through increments of time, is that, when a new increment is beginning the punch moves forward. The parametric program in subject is built in an automatic way, being just necessary that the user inserts the necessary independent parameters. In the Figure 3 the main interface of the program developed in DELPHI is shows, in this figure is also possible to observe the input data that should be insert by the designer.
The Figure 4 shows a flowchart with sequence of operations of the program Estampagem Profunda.
Prof. Avelino Alves Filho – Método dos Elementos Finitos – UNESP Bauru – Semeng
The Figure 5 shows the text interface edition contends the parametric generated. Figure 5 Text interface edition contends the parametric generated. The Figure 6 shows the mesh of the finite elements applied in the sheet after the stamping, in this particular case was stamping 30 mm depth. To obtain the generation of the cylindrical cup in 3D the conditions of geometry expansion they were use. The Figure 7 shows the modeling of the geometry components of the stamping process: Figure 7 Modeling of geometry components of the stamping process Validation of the Parametric Program For validation of the parametric program, experiments were accomplished, and the compared data are the curves of stamping force and thickness variation of the sheet in relation to its radial position.
The chosen material, and used for the making of the experiments, it was a carbon steel sheet, with thickness of 0. Figure 8 Tools used in the experiments. The general parameters used in the experiment were: Table 1 Dimensions of blanks, radius of the die and the punch. The Figure 10 shows the comparison between the stamping forces obtained in the simulation and the experiments for the blank Force N Simulation Exp.
The Figure 11 shows the comparison between the thickness variations of the sheet on its radial position, obtained in simulation and experiments for the blank 1. Radial position is the measure that begins at the center of the blank and extends until the border Variation mm Simulation Exp. The Figure 13 shows the comparison between the stamping forces obtained in the simulation and the experiments for the blank 2. Figure 12 Comparison between the stamping cup obtained in the simulation and experiment for blank Force N Simulation Exp.
The Figure 14 shows the comparison between the thickness variations of the sheet on its radial position obtained in simulation and experiments for the blank Variation mm Simulation Exp. Figure 15 Comparison between the stamping cup obtained in the simulation and experiment for blank 3. The Figure 16 shows a comparison between the stamping cup obtained in the simulation and experiment for the blank 3.
The Figure 17 shows the comparison between the stamping forces obtained in the simulation and the experiments for the blank Force N Simulation Exp. Variation mm Simulation Exp. When we use the parametric program happens a drastic reduction in the necessary time to accomplish the simulation modeling.
It also turns more accessible the construction of this model, stopping being a difficult activity and not needing that the designer has great knowledge of the program ANSYS. Analyzing the results, is observed that when decreases the radius of die and punch, it happens because an increase in the necessary force to accomplished the stamping, because they are more several work conditions and because it also happens an increase in the contact area between the blank and blank-holder, and consequently a increase the force applied by the blank-holder.