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This paper presents the results of a research project obtained using theoretical, numerical and experimental methods, in order to solve the problems encountered when increasing the height of a double deep drawing sink, and the proposed solution. The analysis considers: Manufacturer limitations (eg. tool modifications, steel material changes etc.), the process parameters observed and measured during the deep drawing operation of the failure part, the theoretical fundamentals of sheet metal forming and the analysis and simulation with a computer program based in the finite element method (FEM). The analysis and simulation results using a FEM program showed that, it is possible the height increment of the sink, utilizing a variable blankholder force, to an 11% above from the fabricated parts before the application of the proposed solution but 5% less than the required final product height.

The empirical model of dynamic recrystallization (DRX) coupled with DEFORM 3D® software (based on the finite element method (FEM)) was used to predict the microstructural evolution of the AA7075 processed by four passes of equal channel angular pressing (ECAP) at 250° C. The DRX model parameters were taken from the literature. The simulation results showed that the DRX exhibited a heterogeneous distribution from the back to the frontal part of the sample and this heterogeneity markedly diminished in the fourth pass. The recrystallized volume fraction reached 50% in most of the sample in the fourth pass and the average grain size did not show significant changes, going from an initial value of 16.4 μm to 12.5 μm. This latter result was attributed to the fact that DRX occurred partially even for the last pass. Experimental testing of ECAP was conducted by using the same conditions of computational simulation. The validation of model was performed by comparison of average grain size values with those obtained experimentally by means of image analysis applied on micrographs that were acquired by means of optical microscopy (OM). Hardness and peak load values also indicated the occurrence of a partial dynamic recrystallization and recovery.

The deep drawing process has been widely used in the industry because it eliminates costly operations such as welding and machining. However, there are many parameters involved that affect the quality of the final products. One of the main parameters of the deep drawing process is the maximum deep drawing force (DDF) or drawing load, which is the maximum force required to perform a particular deep drawing operation. This maximum DDF is needed to define the required capacity of the press, and to calculate the deep drawing work and the process efficiency. Several analytical expressions to estimate the maximum DDF have been proposed in the literature, particularly for cylindrical parts. However, few research works have focused on analyzing the prediction performance of these expressions. In this paper, the performance of different analytical expressions to estimate the maximum DDF of cylindrical and rectangular parts, is evaluated and compared. Initially, several expressions proposed by different researches for the maximum DDF of cylindrical parts are presented. Then, these expressions are transformed into new expressions for the maximum DDF of rectangular parts by using different concepts of equivalency, such as the equivalent diameter concept. Finally, the prediction performance of all the expressions for both cylindrical and rectangular deep drawing is analysed and compared using experimental data from the literature. The performance is evaluated in terms of the prediction error. The results have suggested that the analytical expressions involving the largest number of parameters have a superior prediction performance than the analytical expressions involving less parameters.

Frequently it is desired to calculate the blanking shear force of a cospel using an angled matrix as main characteristics of the cutting die. There are two reasons that support the development of this calculation: the first is that the product may change its shape or material, which makes necessary to modify the operating parameters according to the geometric size and metal composition changes. The second is that the nominal capacity of the working press is established by the manufacturer and cannot be altered to adapt to a new product, this means that any new product parameters must be adapted to the capabilities of the machine. Also, the force equation must contain the main variables of the product and not just “proportions” or “factors”, allowing a better approximation of the cutting operation. In this work, a new expression for the blanking force calculus of a cospel is obtained, based on the geometric characteristics of the cutting die (punch and matrix). A matrix die angled is considered as a main characteristic of the sheet metal cutting die, maintaining the punch geometry without cut angles. Two formulas derived from analytical and graphical proposed methods are used and several blanking tests were conducted with a die designed and fabricated properly to run the laboratory tests. The graphical methods are based on a projected area of the metal cospel, obtained from the three dimensional cospel area to cut, this two dimensional projected area is utilized in the expression for the cutting force calculus. On the other hand, the analytical approach considers an area limited from a mathematical equation obtained from a model based on the geometry regions of the blanking die; this area has also utilized as the shear area in the cutting force calculus of a metal cospel. The experimental procedure consisted in reproduce the blanking operation of several metal cospels using the designed and fabricated die. The cutting force was measured using three different matrix die angles probed during the blanking tests, maintaining the same cut angle of the punch during the tests. The tests results were compared with both analytical and graphical methods showing good agreement. Similarly, the cutting force was calculated with analytical and experimental expressions obtained from the specialized literature in order to determine the degree of accuracy of the calculations.Copyright © 2015 by ASME

Deep drawing is a cost effective sheet metal forming process to produce many industrial components. However, complex geometrical drawn parts are difficult to form due to several modes and conditions of the material flow. Commonly problems associated to the forming operation are wrinkling and tearing defects, which affect the cost and quality of the parts. Actually, there are not theoretical methods developed in the literature yet, so the trial and error method are used to reduce or eliminate the deep drawing defects or inclusive is utilized in the earlier production stages, resulting in higher costs and longer production times. This paper describe a proposed solution to reduce or eliminate the wrinkles defects on the flanges of an industrial fan support that result from applying the forming process. An analysis procedure based on the development of the correct sheet metal blank considering three different blank geometries was proposed. The analysis include the analytical methods available in the literature, the simulation with a computer program based on the Finite Element Method (FEM) and experimentation. FEM model, simulation and results, these were validated by measuring the thickness profile on the flanges of a deep drawing part, before and after the procedure implementation. The results have shown that combining both the analytical and FEM methods, were possible to know the influence degree of the sheet metal blank geometry to reduce or eliminate the wrinkle defect and these can be used as an effective design tool.

The deep drawing process is commonly used in the industry because its ability to produce parts with reduced weight and good mechanical properties at a high production rates. However, the elasto-plastic deformation mechanism of deep drawing is complex and difficult to analyse; this because there are many process parameters and variables involved that affect the quality of final products. Among these variables are the geometric parameters, which have been proved to have a great influence on the process. Theoretical and experimental analyses reported in the literature have been mainly focused on conventional cylindrical cup deep drawing. Few research works have dealt with the deep drawing analysis of non-cylindrical parts, particularly the influence of geometrical parameters on the deep drawing performance. This paper presents an analysis of the effect of geometrical parameters on the allowable deep drawing height (DDH) of rectangular parts before fracture. The aim is to identify the influence of the main geometrical parameters on the DDH, Numerical analyses based on the Finite Element Method (FEM) were used to investigate the influence of geometrical parameters, such as the radii, the metal sheet thickness, and the aspect ratio, among others, on the DDH.

The deep drawing process is widely used in industry because it allows the production of parts with reduced weight and good mechanical properties. However, the deep drawing process of non-cylindrical shapes still relies on experimental and trial and error methods, leading to high costs and long development times. The deformation mechanism of non-cylindrical cup drawing is theoretically very complex because of the large elasto-plastic stress and strain, and contact conditions between the tools and the sheet metal involved. In particular, several attempts have been tried in the past to perform theoretical and numerical analysis of rectangular cups. This paper presents an analysis of the allowable deep drawing height (DDH) of rectangular cups. The aim of this paper is twofold: 1) to analyze and estimate the allowable DDH of rectangular parts using theoretical, numerical (FEM) and experimental methods, and 2) identify the theoretical expression that predicts with the highest accuracy the allowable DDH of rectangular parts. A new theoretical expression for predicting this DDH is also proposed. To perform the study FEM is used together with the experimental data from industrial parts. The results show the accuracy of each theoretical expression in predicting the allowable DDH of rectangular parts.Copyright © 2010 by ASME

Complex shape deep drawn parts are more frequently used in many industrial applications. However, complex parts can be particularly difficult to form due to serious wrinkling and tearing problems associated to the different forming modes and complex material flow. Moreover, deep drawing depends highly on the part design, including radii, draw depths, wall angles, steps and transitions; these variables interact to affect the cost and quality of the drawing. Since there are not theoretical methods available in the literature yet, and because several factors affect the drawn, deep drawing of complex shapes is usually developed using the trial and error method. To increase the speed of the design process and the machine tuning, and to reduce the use of the trial and error method, computer-assisted analysis and simulations based on numerical approaches such as Finite Element Method (FEM), are more intensively used. By using these computerized methods, process parameters (sheet metal material, lubricants, forces, part geometry etc.) can be reproduced and modified, part defects can be also identified and, if possible, eliminated. This paper presents the analysis of an industrial double rectangular deep drawing kitchen sink using virtual prototyping based on FEM. In the original deep drawing process the part presented defects (cracks). A failure criterion was established to evaluate and reduce the stresses levels that were causing the cracks. An analysis procedure was then proposed and the optimal lubrication conditions were obtained to eliminate the cracks. FEM model, simulations and results, were validated by measuring the thickness of the actual fabricated part. The thickness of the sheet metal at the critical area was measured in the FEM simulation and compared with the thickness profile of the actual fabricated part before and after changes in the lubrication conditions. The results have shown that FEM can be effectively used as a design tool to eliminate part defects in complex shape deep drawing processes.Copyright © 2010 by ASME

The deep drawing manufacturing process of sheet metal parts with complex shape has increased recently in applications such as in the automotive industry and the household appliances. The trial and error methods commonly used in defining the process parameters, cause high costs and large development times. The computer assisted analysis and simulations are being used more frequently to reduce the cost and development time of a product. The process parameters can be modified and evaluated using these computer simulations before the production is carried out. Therefore the defects of a part can be identified and eliminated, if possible, without the need of the traditional trial and error methods. This paper presents a case study of an industrial component that presented defects (wrinkles at the corners) in its deep drawing process. To eliminate these defects a drawbead was proposed and its optimal location was established using an optimization procedure based on finite element method (FEM). The FEM simulations were validated by measuring the thickness of the fabricated part. To evaluate the elimination of the wrinkle, the thickness of the sheet metal at the critical area was measured in the FEM simulation and compared with the thickness profile before and after the addition of the drawbeads. The results have shown that the design strategy based on FEM can be effectively used as a design tool to eliminate part defects in rectangular deep drawing process.