A Comparative Simulation Study on Springback and Formability Square Cups: Hydromechanical vs. Conditional Deep Drawing

Hydro mechanical deep drawing (HMDD) is an emerging technology that reduces the number of sheet-forming stages and increases the production of advanced lightweight materials with intricate shapes. This study aims to verify the springback in HMDD and the effect of holding time and fluid pressure on this phenomenon (springback). The springback was measured using a new method by matching the projector p-300 axes with the cylindrical cup wall. The difference between the wall and the axis represents the springback value. Using a blank of low carbon steel (1008-AISI) with 80 mm of diameter and a thickness of 0.7 mm. The effect of holding time (1, 2, and 3 minutes) and the fluid pressure (0.6, 0.8, and 1 N/mm2) was studied. The used hydraulic oil was (code number 3803). The springback value of a cylindrical cup was calculated using the profile projector P-300. The result showed that the springback phenomenon was presented in the hydromechanical deep-drawing process but at a lower rate than the traditional deep-drawing process. The holding time and fluid pressure significantly affected the springback value. The springback decreased with increasing the fluid pressure and holding time.

Forming conical parts is one of the difficult fields in sheet metal forming processes. Because of low contact area of the sheet with the punch in the initial stages of forming, too much tension applied to the sheet that it causes bursting. Furthermore, since the major part of the sheet surface between the blank holder and punch tip is free, wrinkles appears on the wall of the drawn parts. These parts are normally formed in industry by processes such as spinning, explosive forming or multistage deep drawing. Hydroforming deep drawing is one of the special deep drawing processes which have been introduced in order to overcome some inherent problems in the conventional deep drawing with rigid tools. In the present work, an experimental program has been carried out to form and compare the forming pure copper conical-cylindrical cups by hydroforming and conventional multistage deep drawing processes. The conical parts in conventional deep drawing process formed in two stages. The results of the study demonstrate that thickness distribution are more uniform in the parts formed by hydroforming compared to conventional multi stages deep drawing processes.

An experimental investigation on the control of process parameters for the hydromechanical deep drawing of mild steel and an aluminium alloy with special attention to control of the blank holder force (BHF) is carried out. The effect of the counter pressure in the hydromechanical deep drawing process is investigated in combination with different constant levels of the BHF. Differences in strains obtained for the conventional and hydromechanical deep drawing process as well as process limitations are presented. An attempt to improve partial quality by control of the packing effect between the blank and draw die by varying the blank holder force according to the punch force have been explored. A closed‐loop control for the BHF is implemented, but no significant effect could be found due to limitations of the BHF range and delayed response of the pneumatic‐based BHF system.

The engine oil pan is used for restraining pollutant and gathering greasing oil from the engine components’ surface which is significant for thermal dissipation and preventing deterioration of oil quality. The study intended to investigate and develop a hybrid sheet hydroforming process for fabricating an innovative high-capacity oil pan that has the characters of asymmetrical cavity depth and major lateral bulging. Firstly, a two-stage hydromechanical deep drawing (HMDD) process was accomplished, which included precedingly regional and eventually integral deep drawing assisted by fluid counter force. The finite element modeling (FEM) was employed to study the impact of the die fillet dimension as well as the loading routes on the formability of the preformed part. The limited drawing ratio can be enhanced from 2.34 to 2.77 for AISI 304 by HMDD. Hydro-bulging was subsequently investigated by the simulations accompanied by the relatively experimental verification. Both the simulated and experimental results showed that there is a remarkable influence of lubrication condition and intermediate heat treatment on the formability of the final part. The cracks occurred at the corners of the main bulging area can be alleviated by reduction of friction coefficient. Furthermore, wrinkles and cracks have been completely eliminated and the thinning ratio can be reduced to 31.8% for the final part, when intermediate heat treatment is additionally employed. It was concluded that the present hybrid sheet hydroforming process is feasible and sufficient to manufacture a sound engine oil pan without any defects through the optimization of the process parameters.

A mathematical model for the prediction of a safe zone for die cavity pressure and blank holding force/pressure, to avoid tensile and compressive instabilities in hydromechanical deep drawing is presented in this paper. Tensile instability is predicted using the load maximization principle whereas a solution for the stability equations provided the critical condition for compressive instability. Predictions of the present work are compared with results available in the literature and are in good agreement. A comprehensive parametric study is carried out to study the effect of process variables on the safe zone.

Controlling the material flow under the blank holder in hydroforming is a delicate point that can be controlled by the blank holder force (BHF), cavity pressure (CP) and the blank holder gap (BHG). BHG is one of the effective parameters to control the material flow. A numerical and experimental approach studied the impact of the BHG on the Hydromechanical Deep Drawing (HDD) of a hemispherical cup made with 2/1 Glare sheets, including another two factors, CP and BHF. BHGs with different thickness was used in the experiments to form Glare Laminate. Simulation and experiment illustrate that an optimized value of these parameters has a good effect on the forming quality and depth of the final product. Finally, an appropriate value of the BHG is projected and the explanations of the failure modes are discussed.

The process of spinning and machining for heavy plates has the problems of a large amount of machining, large springback, and easy cracking. Aiming to address these issues, we proposed a deep drawing forming method for a plate with differential thickness to manufacture an integral ellipsoid component with a thin zone in the middle and a thick zone in the periphery. The plate with a differential thickness was initially produced through machining, followed by the execution of deep drawing deformation. During the deformation process of plates with differential thickness, the thin zone is prone to rupture defects. Therefore, a hydroforming method utilizing an elastic auxiliary plate was adopted to solve this problem. Through mechanical analysis and deep drawing experiments, the influences of hydraulic pressure and elastic auxiliary plate on the distributions of thickness and strain were studied, and the influence of friction on hydroforming was analyzed. The results indicate that increasing the hydraulic pressure and setting elastic auxiliary plates can increase the interfacial friction, reduce the thickness thinning rate, and improve the thickness distribution and deformation uniformity within the thin zone. When the hydraulic pressure is 5.2 MPa and the thickness of the elastic plate is 5 mm, the maximum thickness thinning rate of the ellipsoid shell is 8.8%, which is 34% lower than that of the ellipsoid shell obtained via conventional deep drawing.

Experimental and Finite Element Studies of Redrawing for ASS 316 at Elevated Temperatures

Several studies have explored analytically predicting forming limits in processes like hydroforming and incremental forming, yet there’s a lack of discussion on effective experimental methods. This paper introduces hydro-assisted incremental forming (HAIF) as a hybrid technique combining incremental forming and hydromechanical deep drawing, resulting in improved formability through simultaneous application of normal and through-thickness stresses. A novel test method is devised based on this process, and forming limits are assessed through both experimental and finite element approaches. The authors' earlier analytical forming limit predictions are scrutinized using experimental tests and simulations, revealing a good match. The study reaffirms that the application of normal and through-thickness stresses enhances formability across various strain paths, especially in plane strain mode.

Study of micro hydromechanical deep drawing of SUS304 circular cups by an ALE model

The following contribution focuses on the FEM‐simulation of “Die‐Less‐Hydroforming” using LS‐DYNA. That specific forming technology is used to create structures by inflating initial seal‐welded flat 2D blanks as well as 3D hollow bodies without using any die, mould or punch in contrast to conventional hydroforming (e.g. tube hydroforming or hydromechanical deep drawing). (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Stamp forming method used for forming of relatively smaller and complex-shaped fiber metal laminate (FML) parts has inherent constraints such as fiber sheet rupture, metallic layers quantity, and repeated heating/solidification of thermoplastic (TP) resin/tooling. As an alternate and efficient strategy, simultaneous forming of multiple blanks has been studied by using hydro-mechanical deep drawing (HDD) method. Also, the effect of process variables such as cavity pressure and blank holding force (BHF) and their role in wrinkles formation, thinning, edges movement and formability for the HDD process (performed with and without applying the cavity pressure) has been deliberated. Blanks made of Al 2024-O alloy sheet were used and the formability attributes, based on Barlat 2000 yield criteria, were estimated using DYNAFORM/LS-DYNA and compared with the experimental results. The results show that application of cavity pressure within certain limits has a positive effect on the quality of three-layer formed part as well as leads to higher depths as compared with the process when no cavity pressure was applied. Good agreement has been found between the predicted and the experimental results. The simultaneous forming strategy can give the advantage of eradicating the strict process controls which are needed in the conventional stamp forming method and can expand the application areas of FML parts for the aerospace and automobile industries.

Investigation into the effect of pre-bulging during hydromechanical deep drawing with uniform pressure onto the blank

Deep Drawing (DD) process is the one in which a punch forces a flat sheet metal blank into a die cavity. DD can also be described as the process which involves conversion of flat thin sheet metal blanks into parts of desired shape. Little work is available in the applications of DD processes at elevated temperatures which is going to be a very important manufacturing application in the coming decades. Deep Drawing (DD) is one of the sheet metal forming processes widely used in automobile, aerospace, electronics and allied industries to produce the hollow parts. The improvement in the deep drawing manufacturing process with latest methodologies leads to developments in the automobile and other sheet metal industries. Still today, this process of analysis and design is an art than science. Presently, the conventional deep drawing (CDD) operation is carried out at room temperature in industries. Although the deep drawing process of high strength / low formability metals has an extensive industrial application area, deep drawing at room temperature has serious difficulties because of the large amount of deformations revealed and high flow stresses of the materials. The present paper gives an overview of deep drawing process, its classification along with advantages, limitations and applications.

In the deep drawing processes, the use of an optimal blank shape not only saves the material but also it may reduce the occurrence of defects e.g. wrinkling and tearing. In addition, finding the desirable flange contour, eliminate the trimming step in the deep drawing of parts with flange. The main objective of this study is to optimize the blank shape in order to produce a cylindrical cup with desirable flange contour and investigation of its effect on important parameters. Presently, to overcome this issue, a very expensive and time consuming trial and error method is used. In this study, a systematic method based on sensitivity analysis has been used to find the optimal blank to obtain a desirable flange contour for a cylindrical cup by hydromechanical deep drawing process. With the aid of a well-known dynamic explicit analysis code ABAQUS; optimum initial blank shape has been obtained. With the predicted optimal blank, both computer simulation and experiment are performed and the effect of blank shape on the some parameters such as thickness distribution and forming pressure of the formed cups were investigated. It is shown that formed cup with an optimum blank shape has a better thickness distribution in the rolled direction.