Deep Drawing Process Research Articles

A multi-scale modelling framework for anisotropy prediction in aluminium alloy sheet and its application in the optimisation of the deep-drawing process

This study proposed a crystallographic texture-based multi-scale modelling framework to predict mechanical anisotropy of textured aluminium alloy sheet. The multi-scale scheme was constructed by the combination of a full-field crystal plasticity model in mesoscopic scale and a newly developed phenomenological yield function in continuum scale. In this approach, the mechanical anisotropy of materials is directly obtained from crystal plasticity (CP) modelling without extensive directional tensile tests. The results show that the multi-scale scheme predicted earing profiles coincide well with experimental measurements. This multi-scale modelling could be utilised to design an optimised blank shape with minimum earing for the deep-drawn component, and a convoluted cut-edge was devised accordingly.

On the effect of the ratio between the yield stresses in shear and in uniaxial tension on forming of isotropic materials

It is generally believed that the choice of the yield criterion used to describe the plastic behaviour of isotropic metallic materials does not affect much the accuracy of the predictions of forming operations. For this reason, the von Mises yield criterion is used for modelling the plastic behaviour. However, according to the von Mises yield criterion, irrespective of the material, the ratio between the yield stresses in simple shear and in uniaxial tension is the same. In this paper, it is presented a numerical study which reveals that even for one of the simplest deep drawing processes, namely the forming of a cylindrical cup, the yielding description influences the predictions of the plastic strains and the final profile of the part. For the description of yielding, an isotropic yield criterion which allows to differentiate between isotropic materials was used. Specifically, this yield criterion involves a parameter α which is expressible solely in terms of the ratio between the yield stresses in shear and in uniaxial tension; for α = 0 it reduces to the von Mises yield criterion. The results of the numerical study are revealing and are believed to provide a new point of view when considering material requirements for drawing performance and models to be used for prediction of the plastic behaviour in deep-drawing processes. From the analysis of the loading paths that the materials experience during the forming of the cup, it appears that the prevalent belief that the yielding properties in the tension-tension quadrant of the yield surface dictate the final profile should be reconsidered. Indeed, the simulations results indicate that for isotropic materials characterized by α > 0 (σT/τY>3), the cup height is greater than for a von Mises material (α = 0), which is higher than the one obtained for materials with α < 0 (σT/τY<3), i.e. lower values of the ratio between the yield stresses in shear and in uniaxial tension lead to greater cup heights. It is shown that this is mainly related to the plastic deformation of the material initially located in the flange region, which is dictated by the shape of the yield surface in the compression-tension quadrant (i.e. normal to the yield surface in the region between uniaxial compression and pure shear stress states).

Establishment of sheet metal forming wrinkling limit diagram (WLD) and research on the consistency of WLDs in different processes

With the actual demand for lightweight and high strength of metal parts, wrinkling has become one of the main problems restricting the overall forming of thin-wall members. Therefore, the efficient and accurate prediction and control of it have actual significance. In this work, a critical principal strain analytic model for plate and shell wrinkling was set up with the combination of energy method theory and plastic flow law of material. And a numerical procedure of establishing the wrinkling limit diagram (WLD) was developed based on the finite element method and the critical principal strain analytic model. With the sidewall wrinkling in deep drawing process of the conical cup and the wrinkling of square plate in the Yoshida bucking test (YBT) as the analysis object, the morphology and the characteristics of the WLD under different forming processes were studied, and the effect of loading conditions and stress loading history on the WLD was investigated, it is observed that the WLD is different under the same sheet material but different loading conditions, and indicated the WLD is dependent on the loading conditions.

Effect of temperature on the deep drawing forming performance of Ti/Al laminates: experimental investigation and finite element analysis

In this study, Ti/Al laminates are deep-drawn at elevated temperatures to investigate the effect of temperature on forming performance using numerical and experimental methods. Equipment for warm deep drawing process in a vacuum atmosphere is developed. The corresponding deep drawing finite element model (FE model) is established and validated by thickness distribution along the drawn cups’ radial direction. Based on the developed FE model, the thickness strain in different temperature is compared. Following this, the process window is established to determine the optimum temperature. The ratio curve of plastic deformation to sliding (D/S curve) during warm deep drawing is established to characterize the sustainable formability of Ti/Al laminates. The results indicated that the maximum limit drawing ratio in 200°C is consistent with the minimum thickness reduction. The safe forming area narrows with the increase of the drawing ratio. The D/S curve is short and presented fluctuations in the middle-temperature section of 150–250°C, as revealed well sustainable formability. Furthermore, the thickness of constituent layers for Ti/Al laminates is measured from micromorphology diagrams and compared. It is observed that the thickness strain of outside layers has more possibility to decline in bottom radius and is higher in flange radius than inner layers.

Formation of deep-drawing in an open-die by pulsed-magnetic field pressure

The deep-drawing process is considered one of the most important metal processing processes, which is used to form sheet metal of bowl-shaped structures in the field of mechanical engineering, aviation and rocket engineering under tension and compression without changing the sheet thickness. The present work is to evaluate the formability of an aluminum alloy sheet using an open-die in deep drawing process, an attractive manufacturing technique using electromagnetic force (Lorentz) to form metal parts. This work investigates the history of deformation (displacement, deformation, strain rate) in the process of electromagnetic deep drawing in an open-die using a numerical model. The research methods are the finite element method (FEM) associated with the boundary element method (BEM) using LS-DYNA software for the analysis of electromagnetic, mechanical and thermal solvers. Results analysis of the deformable solid thickness in the process of deformation showed that the thickness increased in the marginal zone and reached 1.77 mm. Further, the thickness in the middle zone decreased by 0.23 mm and decreased by 0.35 mm in the central zone. The plastic deformation of the workpiece gradually increased from zero to 26% for the middle zone, 31% for the marginal zone and 46% for the central zone.

Numerical investigation of the effect of punch corner radius and die shoulder radius on the flange earrings for AA1050 and AA1100 aluminum alloys in cylindrical deep drawing process

In aeronautic sectors, lightweight materials are very demanded in order to reduce fuel consumption. Therefore, thinning drawn cups are very recommended. Reduction of thickness led to many geometrical and physical failures that damage the final product. Since most lightweight materials had a high level of anisotropic, the presence of earrings is one of the most significant failures faced in the deep drawing process. Many functions were developed in order to control these undesirable earrings in sheet metal parts. In this paper, a simulation of a 3D cylindrical deep drawing model for AA1050 and AA1100 aluminum alloys using ABAQUS finite element software was achieved. Prediction of earing phenomenon in deep drawing process was carried out. Moreover, the impact of punch corner radius and die shoulder radius on flange earrings was analyzed and a reduction of the percentage of earring heights was investigated.

Understanding formability and geometrical accuracy of SPIF process used as Reshaping approach

Putting in place Circular Economy strategies is an urgent action to be undertaken. Manufacturing processes play a relevant role as efficient material reuse enabler. Scientists have to make an effort either to find new process or to rethink old process to reprocess End-of-life (EoL) components to recover both material and functions. In this paper, Single Point Incremental Forming (SPIF) process is used for reshaping sheet metal EoL components. Deep drawing process as well as uniaxial pre-straining (to imitate the End-of-Life component) followed by SPIF operations (to obtain the reshaped components) are set- up and implemented to form and reform aluminum sheet metal components. As the authors have already proved the technical feasibility of such an approach, the present paper aims at a better understanding of the formability and geometrical accuracy performance of SPIF process as used to reform components. Specifically, an experimental campaign varying kind and extent of restraining is developed and the formability and geometrical accuracy of the subsequent SIPF operations is analyzed. Results proves that SPIF process is a promising approach for reshaping purpose.

Prediction and assessment of skid line formation during deep drawing of sheet metal components by using FEM simulation

The subjective perception of the quality of sheet metal components mainly depends on geometric characteristics and surface structure. Additionally, particular attention must be paid in this context to avoiding surface defects such as skid lines during the sheet metal forming process. For this reason, current research activities focus on predicting such surface defects as precisely as possible in the early development stages of sheet metal components by using FEM simulation. However, the modelling approaches available today do not yet provide an adequate basis for such a numerical prediction regarding the appearance of surface defects of sheet metal components such as car body outer skin panels, especially of skid lines. Consequently, the research work reported about in this paper concentrates on the development of an empirical methodology for predicting and quantifying the formation of skid lines during deep-drawing processes by using FEM simulation. For this purpose, an experimental tool was developed to produce different skid line formations by using various process parameters and thus to investigate process-influencing factors on the example of the steel sheet material DC06. In principle, the investigations carried out showed that the punch radius and the blank holder force indeed do represent crucial influencing factors for the formation of skid lines. Finally, the results obtained were used to develop a forming simulation criterion, which allows predicting skid lines formations based on calculated strain state variables such as major strain, thinning and unbending strain.

Blank shape optimization in the deep drawing process by sun method

Deep drawing is one of the most important and widely used processes in industry for the production of various parts. In this process, the optimal design of the blank has many advantages such as reducing the cost of production and waste and improving the quality of the process and thickness distribution. In this study, blank optimization involves finding an initial blank geometry in which the edge contours of the final product approach a target contour, taking the required shape after deep drawing. A new iteration based method is proposing for optimizing the shape of a blank in the deep drawing process. The behavior in such problems is severely nonlinear as a result of major plastic deformations and contact phenomena. The general solution to such problems has been to use numerical simulation iterative based methods. The present study implements a similar approach and presents a new algorithm to make geometrical corrections to the external boundaries of a blank in several iterations. A computer program was developed to automatically run these iterations to study the features of the proposed method. Next, two numerical example was solved, and the results are compared with other studies. The proposed method is robust against the initial guess as it manages to optimize the blank regardless of it.

A novel hydrodynamic deep drawing utilizing a combined floating and static die cavity

A novel method named hydrodynamic deep drawing process utilizing a combined floating and static die cavity (HDDC) was proposed in this research, in order to depress wrinkling during hydrodynamic deep drawing process to form a conical cup with higher height. A special experimental setup of a combined die cavity, which a static chamber inlaid with an inner floating die cavity, was designed to implement the modified hydrodynamic deep drawing experiments. At first, the feasibility of the modified method was evaluated in detail by numerical analyses and experimental tests. Then, the effects of the liquid counter pressure in die cavity on the forming process were also studied. It was found that the proposed method HDDC was feasible and the suppressing wrinkling effect dramatically came into being by using a floating die cavity during the hydrodynamic deep drawing process for conical cups of higher height. The rigid contact between the crater corner of the floating cavity and the blank contributes to the suppressing wrinkle effect during the hydrodynamic deep drawing process utilizing a combined floating and static die cavity. The hydrodynamic deep drawing process of conical cups utilizing a combined die cavity becomes more robust compared with the conventional hydromechanical deep drawing process.

Temperature, thermoelectric current and adhesion formation during deep drawing

In sheet metal forming, dissipating forming work and friction lead to a temperature increase, which causes thermoelectric voltages and currents due to the Seebeck effect. Since both temperature and thermoelectric currents influence adhesion formation significantly, knowing their course and maximum values is of great importance. Within this study, several deep drawing experiments with the aluminum alloy EN AW 5083 and the stainless steel X5CrNi18-10 were conducted with an instantaneous measurement of both temperature and thermoelectric currents in situ at the draw ring. Furthermore, the influence of the latter on adhesion formation and punch force was investigated by applying different externally regulated currents between the contact area of tool and sheet metal. The presented results improve the understanding of deep drawing processes and confirm the possibility of reducing adhesions by influencing thermoelectric currents.

Effect of friction stir welding parameters on the deep drawing of tailor-welded blanks (TWBs)

Friction stir welding is a method for joining dissimilar sheets and producing tailor-welded blanks (TWBs). An important issue in TWBs is their formability, as the material properties is not uniform across the welding line. In this method, the mechanical properties changing is a function of welding parameters such as traverse speed, rotational speed, and the shape of the tool. A common issue is choosing proper friction welding parameters to achieve the appropriate forming properties of the welded blanks. So in this paper, TWBs of AA2024-T3 and AA7075-T6 aluminum were prepared and welded using friction stir welding (FSW) method under various conditions, including three different tool shapes as conical, cylindrical, and square under various traverse speeds and rotational speeds. Tensile tests were carried out in order to obtain the best tensile strength conditions that are acceptable for deep drawing. The deep drawing procedure was simulated by using finite element method (FEM) to investigate the effect of weld line properties on thickness distribution and weld line movement. To verify the simulation results, the best joint was subjected to the deep-drawing process and its thickness distribution and welding line movement were compared with the simulation result. The simulation results revealed that the joint made with circular pin obtain gives the best results in deep drawing in terms of thickness distribution and weld line movement.

Effects of Variable Punch Speed and Blank Holder Force in Warm Superplastic Deep Drawing Process

A cylindrical deep drawing test was conducted for the purpose of improving the drawability, product accuracy, and quality in warm deep drawing using a superplastic material with large strain rate dependence. Then, the effects of blank holding force (BHF) and punch speed (SPD) on the flange wrinkle behavior and wall thickness distribution were investigated by experiments and theoretical analysis. A Zn-22Al-0.5Cu-0.01Mg alloy superplastic material SPZ2 with a sheet thickness of 1 mm was employed as the experimental material, and a cylindrical deep drawing experiment with the drawing ratio (DR) of 3.1 and 5 was performed at 250 °C. A good agreement was qualitatively obtained between the elementary theory on the flange wrinkle limit, the fracture limit, and the experimental results. In addition, the authors examined each variable BHF and SPD method obtained from the theory and experimentally demonstrated that the variable BHF method has a great effect on uniform wall thickness distribution and that variable SPD has a great effect on shortening the processing time for superplastic materials. Furthermore, the authors demonstrated the effectiveness of the variable BHF/SPD deep drawing method that varies both BHF and SPD simultaneously.

Deformation Behavior of Single Prismatic Battery Cell Cases and Cell Assemblies Loaded by Internal Pressure

Abstract The safety of electrochemical energy storage system depends on the structural integrity of the call containment. Nominal values of cell case dimensions and material properties are the standard inputs for the mechanical analysis of prismatic lithium-ion batteries. However, such data usually do not account for any considerations on the influence of the manufacturing processes of the cell case. This study investigates the effects of the cell wall thickness and elastic modulus, resulting from deep-drawing process, on the cell and cell assembly response. It is found that the deep-drawing process degrades Young’s modulus relative to standard values and leads to a spatial variation in the wall thickness of the cell case. The use of actual cell case material properties and cell wall thickness values is required to obtain validated finite element models of the battery cell case. Using experiments on internal pressure loaded single battery cells and finite element computations, it is demonstrated that the use of nominal cell casing characteristics significantly underestimates the resistance provided by the cell case to counter swelling of the active battery components.

Earing Reduction by Varying Blank Holding Force in Deep Drawing with Deep Neural Network

In the present study, we propose a novel method of varying blank holding force (BHF) with the segmental blank holder and investigated its influence on the earing reduction in the circular deep drawing process of an aluminum alloy sheet. Based on the analysis of cup height profile, the principle of varying BHF using segmental blank holder was presented and analyzed by analytical theory and numerical simulation. The optimal varying BHF was reasonably determined and compared by using the analytical model and deep neural network (DNN) model integrated with genetic algorithm (GA). The integrated DNN-GA model revealed an accurate prediction and optimization of varying BHF for the minimum earing height variation, which showed a superior result to the analytical model. The optimal varying BHF exhibited a significant influence on the earing formation, resulting in the noticeable decrease of earing height variation. For volume consistency, it was found that an increase in thickness at the cup wall region predicted with the optimal varying BHF was achieved in the transverse direction, which implies an improvement of deep-drawability. Such results indicate that the varying BHF is more reasonable and effective than the uniform BHF. Furthermore, the material properties of the blank sheet also affected the reduction of earing in the deep drawing with varying BHF. The present study revealed that the lower the material strength, the more significant the earing reduction in the deep drawing with varying BHF will be.

Experimental and numerical analysis of aluminium alloy cylindrical cup using novel deep drawing technique

ABSTRACT In the traditional deep drawing process, a blank holder is required to press the blank over the die to prevent wrinkling and to control the material flow into the die cavity. But, this important tool responsible for fracture on the sheet and the optimisation of blank holder pressure is very critical. This present study introduces a new technique for the deep drawing process of cylindrical cups through a conical die without a blank holder. In this new technique, cylindrical cups are produced by pushing a circular blank using a flat-headed cylindrical punch through a conical die with a cylindrical throat in a single punch stroke. A 3-D parametric FE model was built using the commercial FE package ANSYS/APDL-19. A die with a half cone angle of 18° has shown the best drawability for the new technique. A flat-headed punch was used for forming of AA8011 & AA1200 with 1 to 2 mm initial thicknesses and diameters varies from 45 to 65 mm in experimental analysis. 100-ton hydraulic press used for deep drawing setup. Finite element model results showed good agreement with experimental results. Experimentally, a cylindrical cup with a LDR of 2.5 has been successfully achieved.

Investigations of hot-dip galvanized dual-phase steel (DP600+Z) sheet metal on selectively oxidized tool steel surfaces under dry deep-drawing conditions

As reported in previous studies conducted within the priority program 1676 “Dry forming - Sustainable production through dry machining in metal forming”, selectively oxidized tool surfaces represent a promising approach for the realization of a dry forming process. For the transfer of the findings to an actual industrial deep drawing process, the choice of sheet material is of great importance. The present study reports investigations on hot-dip galvanized dual-phase steel that was deep-drawn with selectively oxidized tools made from hardened 1.2379 tool steel. The data are compared to the deep-drawing behavior of electrolytically galvanized deep-drawing steel, which was used as a reference. The applied oxide system consisted of α-Fe2O3 and was generated in a tailored atmosphere with controlled partial pressure of oxygen. A specially developed modular deep-drawing tool was used for the deep-drawing tests, which allowed carrying out cup-drawing tests in which parts of the drawing ring featured different oxidation conditions. The differently set load cases on the drawing ring were then evaluated and examined with respect to the resulting surface properties of the component produced. The changes in the surface morphology prior to and after deep drawing were analyzed using high resolution analysis and the interactions between tool coating and sheet metal were examined. The results obtained provided information about the deep-drawing properties of the sheet metal materials and confirmed the advantages of α-Fe2O3 tool coating used as a low-friction separating layer for use in dry deep drawing.

Robust Optimization and Kriging Metamodeling of Deep-Drawing Process to Obtain a Regulation Curve of Blank Holder Force

In recent decades, the automotive industry has had a constant evolution with consequent enhancement of products quality. In industrial applications, quality may be defined as conformance to product specifications and repeatability of manufacturing process. Moreover, in the modern era of Industry 4.0, research on technological innovation has made the real-time control of manufacturing process possible. Moving from the above context, a method is proposed to perform real-time control of a deep-drawing process, using the stamping of the upper front cross member of a car chassis as industrial case study. In particular, it is proposed to calibrate the force acting on the blank holder, defining a regulation curve that considers the material yield stress and the friction coefficient as the main noise variables of the process. Firstly, deep-drawing process was modeled by using commercial Finite Element (FE) software AutoForm. By means of AutoForm Sigma tool, the stability and capability of deep-drawing process were analyzed. Numerical results were then exploited to create metamodels, by using the kriging technique, which shows the relationships between the process parameters and appropriate quality indices. Multi-objective optimization with a desirability function was carried out to identify the optimal values of input parameters for deep-drawing process. Finally, the desired regulation curve was obtained by maximizing total desirability. The resulting regulation curve can be exploited as a useful tool for real-time control of the force acting on the blank holder.

Springback optimization of deep drawing process based on FEM-ANN-PSO strategy

Deep drawing is one of the most common sheet metal forming processes. It is largely used for mass production of parts in various shapes in automobile, packaging, and household appliance industries. During this process, the stamped part is susceptible to the process failures, especially springback if the process parameters are not correctly selected. The objective of this article is to propose a complete and an efficient optimization approach, starting from modeling and ending with identification of optimal process parameters. Our approach is based on the combination of finite element simulation, design of experiments (DOE), artificial neural network (ANN), and particle swarm optimization (PSO). Based on the comparison of simulation results with experimental results, a finite element model (FEM), which can replace the real deep drawing and predict the springback accurately, has been developed. In this article, process parameters are optimized according to their degree of importance. For this reason, the analysis of variance (ANOVA) method was used to assess the degree of importance of each of the process parameters on springback. An artificial neural network (ANN) model was developed, as a predictor, to relate critical process parameters to springback. Particle swarm optimization (PSO) is then implemented to identify the optimal values of the process parameters. The results indicate an important minimization of springback could be achieved with the use of FEM-ANN-PSO strategy. This approach can, therefore, be used for the optimization of process failures of highly non-linear mechanical systems.

Sensitivity of friction coefficients, material constitutive laws and yield functions on the accuracy of springback prediction for an automotive part

High Strength Steel is more used in automotive industry to combine safety improvements and weight reductions of the vehicles. However, these steels raise new challenges for manufacturer, especially for springback and its prediction. Finite Element Analysis is widely used for the prediction of springback but accuracy is strongly depending on numerical as well as physical parameters. Such parameters affecting prediction are for example frictional behavior, constitutive model, loci function. In this paper the sensitivity of friction coefficients and the influence of some material laws on the springback prediction were studied and analyzed in details. Several numerical models are investigated in this work in order to allow the different aspects of materials mechanical behavior to be better described: isotropic work-hardening (Swift, Hockett-Sherby, SHS), isotropic-kinematic hardening, yield loci (Hill 48, Hill 90 and Barlat 91). In this study, we use an industrial example of the deep drawing process: the side sill closing with the material steel TRIP800. All the simulations are carried out with the commercial code Pam-Stamp 2G and comparison with the experimental results are presented.