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The main focus of the present work is the development of a global procedure for a complete characterization of sheet metal behavior, including anisotropy, evolution of hardening and rupture. This efficient procedure involves the mechanical characterization, at room temperature and in quasi-static conditions, of the material up to large strains by evaluating the local strain field. The initial anisotropy, hardening and rupture of DC04 mild steel are characterized using a complex phenomenological model composed by the non-quadratic Yld2004-18p yield criterion combined with a mixed isotropic-kinematic hardening law and a macroscopic rupture criterion. For this purpose, an inverse methodology for material parameter identification is implemented based on several experimental tests considered as homogeneous and also, a mixed experimental-numerical approach to calibrate the rupture criterion is performed. In order to validate the obtained results, a deep drawing test, leading either to full drawing or rupture of the blank, is carried out. Digital image correlation is used to acquire additional data information in the deep drawing test. Strain fields at several stages of the deep drawing experiment are evaluated leading to a better comparison between the experimental observations and the results of the numerical simulation.

Copper single crystal has excellent electrical properties and ductility, and it has a peculiar application in micro-manufacturing. In this paper, a specific mold was designed and made in order to conduct deep drawing of copper single crystal and evaluate the crystalline orientation effect to the local thinning and rupturing in the process. As a contrast, a finite element subroutine (VUMAT in ABAQUS) based on the crystal plasticity theory was developed to simulate the deep drawing process according to the experimental configurations. The results show that the (1 1 0) blank has better deep drawing performance than (0 0 1) blank; The crack of (0 0 1) blank originates at 〈1 0 0〉 orientation in the plane because 〈1 0 0〉 orientation has poor plasticity; friction is a crucial factor to the forming quality in a small scale deep drawing process; the simulations are in good agreement with the experiments, which also indicates the crystal plasticity model is very necessary to study the plastic forming of metallic material, especially the crystalline characteristics should be considered in the research.

In this paper an improved analytical method for estimating the limiting drawing ratio (LDR) for the first drawing stage is presented. In this method, the effects of parameters such as the geometry and the material properties of die arc region are taken into account for a more accurate determination of LDR. The results are compared to experiments and some other analytical methods reported in the literature. It is shown that the presented method is in good agreement with the experimental results and more accurate compared with other analytical methods. Using the presented method, the effect of some process parameters such as, coefficient of friction, strain hardening exponent, normal plastic anisotropy ratio, ratio of die arc radius to blank thickness and ratio of blank thickness to diameter on LDR is investigated.

In this paper, the finite element method is employed in conjunction with the abductive network to predict the optimum blank contour of an elliptic cylindrical cup with ear-less in deep drawing. The earring behavior of the drawn cup is caused primarily by planar anisotropy in the sheet. Different cup heights combined with various aspect ratios of the elliptic cylindrical cup are taken into account as the process parameters in this study. A finite element-based code is utilized to investigate the material flow characteristics under different process parameters, and the abductive network is then employed to synthesize the data sets obtained from numerical simulations, thus establishing a predictive model. From this model, an optimal blank contour for producing an elliptic cylindrical cup with ear-less can be found. Experiments were carried out with low carbon steel sheet blanks at room temperature for some cases, and the results of experiments show good agreement with the FEM calculations.

This paper discusses the effect of sheet anisotropy on the springback of stainless steel 410 draw-bend specimens. The role that the anisotropy plays in the springback is assessed experimentally as well as through finite element simulations. Process conditions, such as blank holding force, have an obvious effect on springback. Experiments and simulations are conducted with varying blank holding force to assess its role in springback of the formed part. The blank holding effect can also be varied by modifying the contact conditions between the specimen and the die. In this work we consider the effect of lubrication as a means to reduce the coefficient of friction between the contacting surfaces. The role of lubrication has an effect similar to reducing the clamping force. The role of the lubrication on springback is also addressed in this work by comparison to results of dry contact conditions.

Stretch-drawing is a type of the popular deep-drawing process, which utilizes a sharp die shoulder of less than three times the sheet thickness, whereas the conventional process adopts about eight times. When the sheet slides over the die shoulder it is subjected to a strong bending under tension and thus the sheet becomes thinner to yield a deeper cup. Titanium is paid much attention to for its lightness and property of anti-rust. Here, its ability and behavior in the stretch-drawing process is investigated in detail. Two kinds of pure titanium and one of its alloys are tested, of which the thickness is commonly 0.5 mm. It is evidenced that the merit of stretch-drawing or bending under tension is remarkable for titanium sheets as much as for other metals. The variation of the cup wall thickness with the die profile radius, and the relationship between the blank diameter and the depth of formed cups are clarified. The shape quality of the formed cups is also inspected, especially regarding the roundness and the three-dimensional radius distribution of the cup wall cross-section. The former indicates the level of deviation of any cup cross-section from an exact circle, and the latter the global distortion pattern of the cup. The shape quality of a stretch-drawn cup is confirmed to be better than that of a deep-drawn cup. Furthermore, the measurement of the shape implies that its feature depends on the planar anisotropy of the sheets tested.

The present study aims to determine the optimum shape of a blank for the deep drawing of a cylindrical cup without ears. The earing behavior of the deformed cup was predicted from the anisotropic properties of the sheet metals. Sheet metals used in the experiments are low carbon steel and commercially pure aluminum. The nominal thickness was 1.0 mm for all sheets. The modified blank is used to reduce the ear configuration. Comparison between experimental results of circular and modified blanks are included. The punch load and the work requirements were reduced. The limiting drawing ratios were slightly improved.

Based on the load-maximum principle of plastic flow, a new equation, including the process parameters of the strain-hardening exponent n, the normal anisotropy value R, the coefficient of friction μ, the radius of the die arc rd (the bending effect) and the thickness of the blank t0, for evaluating the maximum drawing load Pd at a particular drawing ratio in the cup-drawing of a cylindrical cup with a flat-nosed punch is derived by an elementary analysis. Compared with published experimental work, good agreement between calculation and the experiment is obtained. The new equation is simple and practically applicable, exploring the interaction between the process parameters mentioned above and the value of Pd and thereby enabling a better understanding of the cup-drawing behavior of sheet metal.