Hydrodynamic Deep Drawing Process Research Articles

On Improving Sheet Metal Formability in Hydrodynamic Deep Drawing Process through a Solid‐Oil‐Type Mineral Grease Pressure Medium

In this research, the improvement in sheet metal formability obtained through the utilization of a mineral grease in solid‐oil‐type (SMG) pressure medium in the hydrodynamic deep drawing process assisted by radial pressure is investigated by experiments and finite‐element method (FEM) simulations on flat‐bottom cups realized with pure copper and DIN 1.0338 steel. To determine the process parameters ranges, an FEM model is developed in ABAQUS/Explicit and validated against experimental results. Afterward, experiments are carried out using two pressure mediums with different viscosities, i.e., water and SMG. Considering the results relevant for both sheet materials, the SMG medium allows an average reduction of the sheet metal thinning of 15% and 10% on the corner edges while also granting a negligible thickness variation on the cup walls. In contrast, the higher viscosity of the SMG, in comparison to the water medium, also results in an average 16% increase in the forming force when compared to the water pressure medium.

Study on the key process parameters of hydrodynamic deep drawing on the stainless steel single sink with countertop

Stainless steel single sink with countertop (SC) has the characteristics of large depth and asymmetric countertop. Its traditional stamping process is mainly realized by the combination of multi-stage deep drawing and annealing process, which leads to the complex manufacturing process, long production chain and poor consistency of products. Based on finite element analysis software (Dynaform) with nonlinear dynamic display algorithm, numerical simulation analysis and research are carried out on the parameters of hydrodynamic deep drawing. First, the sink and the part of countertop are preformed into a cylinder shell, and then the excess of the cylinder shell is drawn back to the countertop. The research results show that the hydrodynamic deep drawing process can effectively improve the flow uniformity of stainless steel sheet, increase the forming of stainless steel tank, drawing a more uniform wall thickness, thus effectively improve the quality of single tank with countertop by setting up reasonable preform structure, controlling the liquid pressure and its loading paths and blank-holder force.

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.

Effect of Anisotropic Yield Functions on Prediction of Critical Process Window and Deformation Behavior for Hydrodynamic Deep Drawing of Aluminum Alloys

Owing to the reduction of rupture instability and the avoidance of wrinkle defect, the hydrodynamic deep drawing (HDD) process is gradually becoming attractive for fabricating lightweight and complicated products. Meanwhile, since metallic materials present anisotropic deformation behavior, it is necessary to select an appropriate constitutive model for the prediction of plastic deformation behavior of applied material with high precision. In the present research, several anisotropic yield criteria, namely, Hill’48, Yld2000-2d, and BBC2005, were implemented to investigate the effects of yield functions on the prediction accuracy of the critical process window and deformation behavior for the HDD process of 2024 and 5754 aluminum alloys. Material constants in the yield criteria were determined by applying uniaxial and equi-biaxial tension tests and optimizing an error-function using the Levenberg–Marquardt algorithm. Furthermore, the process window diagram was computed utilizing the stress analytical model combined material properties with workpiece geometrical features. Numerical simulation results of predicted material anisotropic parameters, process window, and HDD deformation for aluminum alloys were compared with the experimental data. Through the comparison of diverse yield criteria based on materials’ anisotropic coefficients, critical process window prediction, earing profile, and thickness distribution, it was revealed that the Yld2000-2d and the BBC2005 yield criteria can offer more precise models of material behavior in planar anisotropy properties for the HDD process of 2024 and 5754 aluminum alloys.

Simulation and Experimental Studies on Hydrodynamic Deep Drawing of 2198 Aluminum Lithium Alloy

The process of hydrodynamic deep drawing of Al2198 was investigated by finite element (FE) simulation and experimental works. The effects of die cavity pressure, blank holder gap and pre-bulging pressure on the forming process and the thickness distribution were evaluated. The results indicate that the pressure inside the liquid chamber and the blank holder gap or blank holder force are the main factors affecting hydrodynamic deep drawing process. In addition, appropriate pre-bulging pressure is beneficial to form good quality parts with a relatively uniform wall thickness.

Optimization of Hydroforming Process for Deep Drawing of AA7075 Using Finite Element Simulation and Response Surface Methodology

Aluminum 7075 is a functional aerospace alloy that has high strength and low formability during room temperature deep drawing. Therefore, to avoid warm forming process and relative difficulties, careful control in the process design is needed to enhance quality of drawn part and improve die life. In the present work, an attempt was made to experimentally and numerically study the effect of hydrodynamic deep drawing process such as die geometry and fluid pressure on thinning ratio and punch force. Statistical analysis based on response surface methodology was carried out to correlate empirical relationship between die corner radius, punch corner radius and die fluid pressure as process factors and maximum thinning ratio and punch force as responses. Sensitivity analysis was also performed to find out the factor having greatest impact on aforementioned responses. Further, optimization was carried out by using desirability approach to find out optimal parameter setting to attain minimum thinning and forming force simultaneously. Results indicated that punch and die corner radius followed by fluid had significant effect on the process quality characteristics. Moreover, setting of 9.3 mm punch corner radius, 2 mm die corner radius and 26 MPa fluid pressure resulted in 71% desirability incorporating 31% thinning and 175 MPa punch force. The obtained optimal results were then verified through both FE simulation and confirmatory experiment.

Effect of pre-forming and pressure path on deformation behavior in multi-pass hydrodynamic deep drawing process

Hydrodynamic deep drawing (HDD) is an effective method for the fabrication of the sheet metal parts with deep cavity and complex surface configuration. Despite the remarkable progress that has been made on the development of one-stroke HDD process, a number of fundamental challenges are still unsolved in the multi-stage HDD technology due to the unique process allocation and continuous deformation behavior. In this study, the effect of pre-forming parameters and loading locus of cavity pressure on the sequential deformation of aluminum alloy is explored to determine the suitable working conditions to form a conical part with deep cavity using multi-pass HDD process. Based on the equal allowance function method, the material deformation amount for the multi-pass process is allocated and optimized. In addition, the defect patterns including wrinkling and tearing during the multi-step process are discussed. The effect of pre-forming depth and loading loci of cavity pressure on the dimensional accuracy and thickness variation of the workpiece is analyzed, the appropriate pre-forming depth and loading loci of cavity pressure are achieved by using numerical models implementing diverse yield criteria. The results mirror that yld2000-2d and BBC2005 yield functions predict the pre-forming depth more accurately with respect to Von Mises isotropic formulation and Hill’48 yield criterion. However, the prediction accuracy of the pre-forming stage is superior to that of the final forming period using yld2000-2d yield formula due to the error accumulation and the effect of prestrain on the sequential process. Moreover, the reasonable loading path of cavity pressure for the intermediate cylindrical part is characterized by three feature points, whereas the suitable pressure locus for the final conical part is featured with four unique points and three distinct segments containing low-pressure stage, pressure-raising stage and full pressure period. By using the suitable working conditions, the well-formed conical part with homogenous thickness distribution, desirable surface finish, and high dimensional precision is fabricated, which highlights that the proposed multi-step HDD technology is valid for the integration and precision forming of the workpiece with complex feature and high drawing ratio.

Hydrodynamic deep drawing of double layered conical cups

Hydrodynamic deep drawing assisted by radial pressure is an advanced sheet forming technology with great advantages such as higher drawing ratio, good surface quality and higher dimensional accuracy. In this process, both the bottom surface and the peripheral edge of sheets are under hydrodynamic pressure, so that the forming procedure is more uniform with low failure probability. Multi-layered sheets with complex geometries could be formed more easily with this technique compared with other traditional methods. Rupture is the main irrecoverable failure form in sheet forming processes. Prediction of rupture occurrence is of great importance for determining and optimizing the proper process parameters. In this research, a theoretical model was proposed to calculate the critical rupture pressure in production of double layered conical parts with hydrodynamic deep drawing process assisted by radial pressure. The effects of other process parameters on critical rupture pressure, such as punch tip radius, drawing ratio, coefficient of friction, sheet thickness and material properties were also discussed. The proposed model was compared with finite element simulation and validated by experiments on Al1050/St13 double layered sheets, where a good agreement was found with analytical results.

Process analysis of hydrodynamic deep drawing of cone cups assisted by radial pressure

Forming of flat sheets into shell conical parts is a complex manufacturing process. Hydrodynamic deep drawing process assisted by radial pressure is a new hydroforming technology in which fluid pressure is applied to the peripheral edge of the sheet in addition to the sheet surface. This technique results in higher drawing ratio and dimensional accuracy, better surface quality, and ability of forming more complex geometries. In this research, a new theoretical model is developed to predict the critical rupture pressure in production of cone cups. In this analysis, Barlat–Lian yield criterion is utilized and tensile instability is considered based on the maximum load applied on the sheet. The proposed model is then validated by a series of experiments. The theoretical predictions are in good agreement with the experimental results. The effects of geometrical parameters and material properties on critical rupture pressure are also studied. The critical pressure is increased with increase in the height ratio, strain hardening exponent, and anisotropy. Higher punch nose radius expands the safe zone. It is shown that the critical pressure decreases for drawing ratios higher than 4.

Pressure path optimization of hydrodynamic deep drawing of cylindrical-conical parts

Pressure path is one of the most important parameters in hydrodynamic deep drawing process which affect on thickness distribution and bursting in the parts. In this study, a combination of finite element simulation and artificial intelligence was used to optimize the pressure path in hydrodynamic deep drawing process of cylindrical-conical parts to reach the minimum thickness reduction in critical region of product. First, a finite element simulation model was verified based on experimental results. Then, a neural network model was developed using the data generated from the verified finite element model to predict the thickness in critical region of product. The results indicated that the neural network model can be applied successfully for prediction of sheet thickness. In addition, the neural network model was used as a function in simulated annealing algorithm to maximize the thickness in the mentioned critical region. The final results showed that utilization of the optimized loading path yields good uniform thickness distribution of the part.

Influence of cavity pressure on hydrodynamic deep drawing of aluminum alloy rectangular box with wide flange

Abstract The multi-stage deep drawing process had been traditionally adopted for the box part with super wide flange using multiple annealing procedures with problems of poor surface quality, long manufacturing cycle, high cost and low yield. The hydrodynamic deep drawing (HDD) method was suggested to solve these issues during the multi-stage drawing process, in which the loading path of cavity pressure was one of the key parameters immediately related to the product's quality. The effects of cavity pressure on forming quality and precision were explored according to theoretical analysis, numerical simulations and experiments, and the process window of cavity pressure was established through stress analysis of the corner and straight regions. Meanwhile, wall thickness distributions were investigated with different parameters, including pre-bulging pressure, piecewise stroke and maximum pressure. Furthermore, the reasonable loading path was validated by process experiments. The results indicate that the proper control of cavity pressure will be beneficial in improving the drawability of aluminum alloys effectively, and the conventional drawing process consisting of three drawing operations and two intermediate anneals can be replaced by the one-step HDD process.

Development of Dynamic Loading System for Sheet Metal Hydrodynamic Deep Drawing and Its Application

The loading paths of cavity pressure and blank holding force(BHF) are the key parameters immediately related with the forming quality in hydrodynamic deep drawing process. Aiming at the issues of single loading trajectory and low liquid pressure in the passive-pressurization model, which can not satisfy the need of the complex structural components and high strength materials, a dynamic loading method employing closed-loop control technique to realize the real time adjustment of cavity pressure and BHF is presented. The controllable blank holding system and high pressure pressurization device are designed, and the control system based on upper and lower computers is applied to regulate punch velocity, BHF and cavity pressure, which can change in real time according to assigned craft curves. The process experiments conducted on the dynamic loading system implement the integral and precision forming of a typical stainless steel part with complex features, and the test parts under dynamic loading paths have good surface quality and high forming precision. The results indicate that the dynamic loading technology can implement complicated loading paths and partial high pressure, which are propitious to form complicated structural components and high-strength materials.

Hydrodynamic deep drawing process assisted by radial pressure with inward flowing liquid

A radial pressure can reduce drawing force and increase drawing ratio in hydrodynamic deep drawing. However, conventional hydrodynamic deep drawing cannot attain a radial pressure higher than the pressure in the die cavity. In this research, a modified method, named hydrodynamic deep drawing assisted by radial pressure with inward flowing liquid, was proposed and investigated using both primarily experimental and numerical simulation analysis. A radial pressure higher than the pressure in the die cavity was realized by means of the inward flowing of the liquid during this process. After preliminary experimental validation, FEM was used to explore the forming process. The results from the simulation were compared with those from the experiment. The effects of the radial pressure on the wall thickness distribution, punch force, and compressive stress in the blank flange were studied with assistance of numerical simulation. The process window for radial pressures versus drawing ratios was established in 2Al2O alloy experimentally and cups with drawing ratio of 2.85 were successfully formed.

Investigation of hydrodynamic deep drawing for conical–cylindrical cups

Forming conical parts is one of the complex and difficult fields in sheet-metal forming processes. Because of low-contact area of the sheet with punch tip in the initial stages of forming, bursting occurs on the sheet. Moreover, since most of the sheet surface in the area between the punch tip and blank holder is free, wrinkles appear on the wall of the drawing part. Thus, these parts are normally formed in industry by spinning, explosive forming, or multi-stage deep drawing processes. In this paper, forming pure copper and St14 conical–cylindrical cups in the hydrodynamic deep drawing process was studied using finite element (FE) simulation and experiment. The effect of pressure path on the occurrence of defects and thickness distribution and drawing ratio of the sheet was studied. It was concluded that at low pressures, bursting occurs on the contact area of sheet with punch tip. At higher pressures, the cup was formed, but the wall thickness distribution depends on the pressure path. It was also illustrated that for the pressure path with a certain maximum amount, the workpiece was formed adequately with minimum sheet thickness reduction. Internal pressures more than this maximum amounts did not affect on the thickness distribution. By applying the desired pressure path, conical–cylindrical cups with high deep drawing ratio were achieved.

The Effect of Process Parameters on Thickness Distribution in Hydroforming of Conical-Cylindrical Cups

Forming conical parts is one of the complex and difficult fields in sheet metal forming processes. These parts are normally formed in industry by spinning, explosive forming or multistage deep drawing processes. In this paper, forming pure copper conical–cylindrical cups in the hydrodynamic deep drawing process was studied using finite element (FE) simulation and experiment. In this study, the effect of cone angle and punch tip radius on bursting and thickness distribution of the parts and also the effect of pressure path on thickness distribution were examined. Using the measurements of strains and thickness variations on the cup wall, the quality of the drawn cups was evaluated. The results demonstrated that increasing cone angle will lead to higher drawing ratio and uniform thickness distribution. Also, it was concluded that in the conical-cylindrical part the punch tip radius region is the most critical zone. At this zone, the more the cone angle the less the possibility of tearing is. In addition, with increasing punch tip radius it could be seen that the thickness reduction decreases.

Hydrodynamic Deep Drawing Process with Hybrid Blank Holder

In order to decrease the friction force caused by thickening of blank flange during the hydrodynamic deep drawing process with inward flowing liquid,a new method,hydrodynamic deep drawing process with hybrid blank holder is proposed.The nature of the hybrid blank holding during the process is analyzed,and the effects of the gap between blank holder and die,the blank holding force,and the radial pressure on the forming process are studied.The result shows that the actual maximum blank holder force,the friction resistance in the flange region and the thinning rate of the second valley bottom point can be reduced by using hrbrid blank holder;the blank holder force and the gap between blank holder and die have influence on the wall thickness distribution of formed part great blank holder force results in thin wall thickness;small gap between blank holder and die also results in thin wall thickness,then the second valley bottom point is more close to the bottom of formed part.

Investigation into hydrodynamic deep drawing assisted by radial pressure: Part II. Numerical analysis of the drawing mechanism and the process parameters

A new method, named hydrodynamic deep drawing assisted by radial pressure, is proposed. Different from the conventional hydrodynamic deep drawing process (HDD), a radial pressure is loaded along the blank rim to reduce the drawing force. To explore the internal deformation mechanism, the numerical simulation was used for analyzing the forming process of an Al–Mg–Si aluminum alloy by using explicit dynamic finite element calculations utilizing non-quadratic yield criteria. Firstly, the loading boundary conditions were studied for the purpose of calculating the forming process accurately. The effects of sheet anisotropy on the material flow velocity distribution, the stress distribution, the strain distribution and the sheet thickness distribution were investigated. The optimum parameters were studied so that the flange wrinkling and fracture can be predicted and controlled effectively. The simulated results were in good agreement with the experiment.

Key technologies of the simulation of the hydrodynamic deep drawing of irregular parts

Because of the complex boundary conditions to be dealt with, it is a difficult task to simulate the hydrodynamic deep drawing of irregular cups. If the boundary conditions on the loading of liquid pressure onto the blank are not considered correctly, the results obtained from the FEM will differ greatly from the experimental results. In this paper a mathematical model is proposed for the liquid flow between the flange and the die when drawing a tapered rectangular cup using hydrodynamic deep drawing. The proposed model was incorporated into a commercial FEM software (LS-DYNA3D), successfully. Process parameters including die entrance radius, lubrication, blank geometry, and the control of material flow for the hydrodynamic deep drawing of a tapered rectangular cup were investigated. Based an experimental unit mounted onto a single-action hydraulic press, the hydrodynamic deep drawing process was also investigated experimentally. It was shown that the FE results matched well with the experimental results, which may suggest that the proposed method can be used to determine the main process parameters during the hydrodynamic deep drawing of irregular cups.

The hydrodynamic deep-drawing process for blanks of non-uniform thickness

The process of hydrodynamic deep-drawing (HDD) has been modified to draw tapered blanks of small angles. This option, unattainable in classical deep-drawing processes, has its applications in producing specially-dedicated products. But, more generally, this process is aimed at decreasing the demand for a strict uniformity of blank thickness and thus relaxing the costly tight tolerances on the preformed blanks. The idea rests on changing the customary clamped die to a self-aligned die by letting it be semi-spherical with rotational degrees of freedom. The automatic self-alignment of the die to the current angle of the blank arises from the very nature of the hydrodynamic fluid pressure beneath the blank. The solution for the statically admissible stresses throughout the flange is produced in an asymptotic-expansion fashion, with the inclusion of thickness variation, interfacial friction and exponential hardening of the material. Consequently, the apparently ‘bizarre’ phenomenon of rupture initiating at the thickest portion of the blank (rather than at the thinnest portion) is revealed. Expressions for the limit drawing ratio (LDR) as a function of the angle of the tapered blank (beside other relevant parameters) are developed. They are compared favourably with experiments produced on a specially built apparatus.

On the hydrodynamic deep-drawing process

The feasibility of deep-drawing aided by hydrodynamic flow beneath the blank is demonstrated. The analytical background for directing the design of the process is based on the limit analysis in plasticity theory coupled with flow analysis of viscous, non-inertial fluid. It is done for isotropic non-hardening material with inclusion of constant friction coefficient as an additional parameter acting on plastic/rigid interfaces. The main attention is focused on approximating the Limit Drawing Ratio (LDR) via upper and lower bound and comparing the conventional process to the suggested hydrodynamic-aided process. The unique features of the process along with its limitations (geometrical and material-wise) are exhibited. The prominent role of the die curvature with regard to LDR is emphasized. A non-dimensional number combining fluid viscosity, punch speed, material strength and a characteristic length of the process (identified as Sommerfeld Number) appears as a useful measure for the clearance height through which the fluid flows. The study is corroborated with experiments.