Sheet Hydroforming Research Articles

Improving the Quality of Reshaped EoL Components by Means of Accurate Metamodels and Evolutionary Algorithms

The reshaping of End-of-Life (EoL) components by means of the sheet metal forming process has been considered largely attractive, even from the social and economic point of view. At the same time, EoL parts can often be characterized by non-uniform thicknesses or alternation of work-hardened/undeformed zones as the result of the manufacturing process. Such heterogeneity can hinder a proper reshaping of the EoL part, and residual marks on the reformed blanks can still be present at the end of the reshaping step. In a previous analysis, the authors evaluated the effectiveness of reshaping a blank with a deep-drawn feature by means of the Sheet Hydroforming (SHF) process: it was demonstrated that residual marks were still present if the deep-drawn feature was located in a region not enough strained during the reshaping step. Starting from this condition and adopting a numerical approach, additional investigations were carried out, changing the profile of the load applied by the blank holder and the maximum oil pressure. Numerical results were collected in terms of overall strain severity and residual height of the residual marks from the deep-drawn feature at the end of the reshaping step. Data were then fitted by accurate Response Surfaces trained by means of interpolant Radial Basis Functions and anisotropic Kriging algorithms, subsequently used to carry out a virtual optimization managed by multi-objective evolutionary algorithms (MOGA-II and NSGA-II). Optimization results, subsequently validated via experimental trials, provided the optimal working conditions to achieve a remarkable reduction of the marks from the deep-drawn feature without the occurrence of rupture.

MODELING OF SHEET METAL FORMING USING QUASI-ELASTIC MEDIA

In this paper a review on simulations using FEM for sheet metal hydroforming is presented. Hydroforming can be done either with a punch and a pressurized fluid that replaces the die or by using fluid under pressure instead of the punch and with a die. The main types of sheet hydroforming techniques are: with fluid, either directly or with a rubber diaphragm; or with rubber, that can behave like a fluid under a high enough pressure. There are different variations of hydroforming, using different types of fluids with different properties. Some of these hydroforming methods have been simulated by different researchers, using different FEM software, like Dynaform, Abaqus, etc. The purpose of these FEM simulations is to obtain results that are close to the results obtained experimentally, to be able to compare them, which can be quite difficult, because of the fact that there are multiple parameters that can influence the results.

A 3D Non-Linear FE Model and Optimization of Cavity Die Sheet Hydroforming Process

Cryo-rolled aluminum alloys have a much higher strength-to-weight ratio than cold-rolled alloys, which makes them invaluable in the aerospace and automotive industries. However, this strength gain is frequently accompanied by a formability loss. When uniformly applied to the blank surface, hydroforming provides a solution by generating geometries with constant thickness, making it possible to produce complex structures with “near-net dimensions”, which are difficult to achieve with conventional approaches. This study delves into the cavity die sheet hydroforming (CDSHF) process for high-strength cryo-rolled AA5083 aluminum alloy, focusing on two primary research questions. Firstly, we explored the utilization of a nonlinear 3D finite-element (FE) model to understand its impact on the dimensional accuracy of hydroformed components within the CDSHF process. Specifically, we investigated how decreasing fluid pressure and increasing the holding time of peak fluid pressure can be quantitatively assessed. Secondly, we delved into the optimization of process parameters—fluid pressure (FP), blank holding force (BHF), coefficient of friction (CoF), and flange radius (FR)—to achieve dimensional accuracy in hydroformed square cups through the CDSHF process. Our findings reveal that our efforts, such as reducing peak fluid pressure to 22 MPa, implementing a 30 s holding period, and utilizing an unloading path, enhanced component quality. We demonstrated this with a 35 mm deep square cup exhibiting a 16.1 mm corner radius and reduced material thinning to 5.5%. Leveraging a sophisticated nonlinear 3D FE model coupled with response surface methodology (RSM) and multi-objective optimization techniques, we systematically identified the optimal process configurations, accounting for parameter interactions. Our results underscore the quantitative efficacy of these optimization strategies, as the optimized RSM model closely aligns with finite-element (FE) simulation results, predicting a thinning percentage of 5.27 and a corner radius of 18.64 mm. Overall, our study provides valuable insights into enhancing dimensional accuracy and process optimization in CDSHF, with far-reaching implications for advancing metal-forming technologies.

Advancements in robot-assisted incremental sheet hydroforming: a comparative analysis of formability, mechanical properties, and surface finish for rhomboidal and conical frustums

Advancements in robot-assisted incremental sheet hydroforming: a comparative analysis of formability, mechanical properties, and surface finish for rhomboidal and conical frustums

Simple Contact Sensor for Material on Die in Sheet Hydroforming

A simple material contact sensor on the forming tool was devised for sheet hydroforming. The applicability was investigated for the shallow forming of aluminum alloy sheet. A flat bottom axisymmetric die or a conical one was used. An antistatic electric tape was used as contact sensor. It is flexible and attached to the die cavity in the radial direction. Electrical resistance of the tape between the center and the contact position of the material changes as the forming progresses. The change in voltage of the resistance part corresponding to the contact length was captured continuously. The strain at the center of the circular test piece was also continuously measured using a strain gage for large deformation. A short contact length was captured for the flat bottom die, since the test piece deforms into a dome shape, and the tip of the dome contacts to the center of the die cavity. On the other hand, the captured length was longer in the forming with the conical die. The repetitive separation and contact motion of the test piece to the die in impact forming due to the impulsive water pressure was successfully captured by the contact sensor. The accuracy was relatively coarse due to that the diameter of the die cavity was small. However, it was found that the simple contact sensor can be applied to evaluate the deformation behavior of the material. The measured maximum strain of the test piece was larger in impact forming, and the strain concentration occurred. This may be due to the negative strain rate sensitivity of the material.

Multi-objective optimization of loading path for sheet hydroforming of tank bottom

As a critical component of the propellant tank, the tank bottom is subjected to complex loads such as internal pressure and vibration and has high requirements for structural load-bearing capacity. Hydroforming deep drawing is one of the techniques for the integral forming of the tank bottom. As the tank bottom is a large-size thin-walled structure, defects such as cracks and wrinkles are prone to occur during the hydroforming deep drawing process. Aiming at reducing these defects, the hydraulic pressure loading path and blank holder force loading path of the hydroforming deep drawing process are studied, and a multi-objective optimization method is proposed to improve the surface accuracy and thickness distribution uniformity of the tank bottom. The complex loading path curve optimization problem is transformed into a functional relationship between hydraulic pressure and blank holder force with time. The hydraulic pressure and blank holder force at each time node are used as design variables, and the maximum wall thickness reduction rate, rupture trend factor, wrinkle height, and wrinkle trend factor are used as optimization targets. The radial basis function (RBF) neural network is used to establish the approximate model between the loading path and the optimization target, and the multi-objective particle swarm optimization (MOPSO) algorithm is used to optimize the solution. Taking the hemispherical tank bottom as an example, the optimal hydraulic pressure loading path and blank holder force loading path are obtained, and the quality of the formed part is improved.

Development of a Micro Sheet Hydroforming Setup to Produce Micro Cup Products

Development of a Micro Sheet Hydroforming Setup to Produce Micro Cup Products

Investigation of the effect of process parameters in sheet hydroforming process

Investigation of the effect of process parameters in sheet hydroforming process

Studies on Finite Element Analysis in Hydroforming of Nimonic 90 Sheet

The primary goal of this study was to investigate the formability of Nimonic 90 sheet which performs well at high temperatures and pressures, making it ideal for applications in the aerospace, processing, and manufacturing industries. In this present study, finite element analysis (FEA) and optimization of process parameters for formability of Nimonic 90 in sheet hydroforming were investigated. The material’s mechanical properties were obtained by uniaxial tensile tests as per the standard ASTM E8/E8M. The sheet hydroforming process was first simulated to obtain maximum pressure (53.46 MPa) using the FEA and was then validated using an experiment. The maximum pressure obtained was 50.5 MPa in experimentation. Since fully experimental or simulation designs are impractical, the Box–Behnken design (BBD) was used to investigate various process parameters. Formability was measured by the forming limit diagram (FLD) and maximum deformation achieved without failure. Analysis of variance (ANOVA) results also revealed that pressure and thickness were the most effective parameters for achieving maximum deformation without failure. Response surface methodology (RSM) optimizer was used to predict optimized process parameter to achieve maximized response (deformation) without failure. Experimental validation was carried out for the optimized parameters. The percentage of error between experimental and simulation results for maximum deformation was less than 5%. The findings revealed that all the aspects in the presented regression model and FEM simulation were effective on response values.

Microstructural analysis of sheet hydroforming process assisted by radial ultrasonic punch vibration in a hydro-mechanical deep drawing die

Microstructural analysis of sheet hydroforming process assisted by radial ultrasonic punch vibration in a hydro-mechanical deep drawing die

Design, Fabrication and Performance Tests of a Double-sided Sheet Hydroforming Test System

Design, Fabrication and Performance Tests of a Double-sided Sheet Hydroforming Test System

Reshaping End-of-Life components by sheet hydroforming: An experimental and numerical analysis

In this study, a numerical/experimental analysis is proposed to investigate the possibility of reshaping sheet metal-based End-of-Life (EoL) components using sheet Hydroforming (SHF). Returned EoL components are challenging to be reformed, they are usually characterised by high heterogeneity as there are localised thinning areas (caused by the original forming processes), and the overall formability is reduced with respect to the original flat sheet material. The reshaping route was replicated: a deep drawing process was adopted to impart a square feature; subsequently, SHF was performed. The capability of remove the deep drawn feature was analysed with varying Blank-holder force, oil pressure profile and the location of the previous deep drawn feature. A 3D finite element model of the entire manufacturing route was used to analyse the strain paths of the reshaping process. The change in the strain paths when considering a component previously subjected to deep drawing was analysed and discussed in comparison with SHF using an undeformed blank. This study for the first time provides an insight on the reshaping process mechanics as well as attempts at quantifying the quality of the reshaped components. Results revealed that SHF can be successfully adopted for reshaping purposes as it performed well under two analysed aspects: capability of removing the existing feature and imparting a brand-new shape and thickness/strain path analyses (avoiding fracture and excessive thinning). Nevertheless, the developed analyses revealed that reshaping is more challenging than conventional forming and new design rules, identified in the present paper, need to be followed.

Numerical simulation and experimental study of warm hydro-forming of magnesium alloy sheet

The uneven forming temperature during warm hydro-forming of magnesium alloy sheets is one of the main causes of defects in formed parts. In order to completely solve this problem to obtain products with good forming quality, a new warm forming method for magnesium alloy sheet is proposed: the magnesium alloy sheets and forming die are immersed in hot oil to achieve constant temperature forming. In addition, a hot oil warm hydro-forming device for magnesium alloy sheets was designed and developed. This work also carried out the numerical simulations and forming experiments, this study to investigated the effects of forming concave die chamfer, temperature, friction coefficient, hydraulic pressure, and blank holder force on the warm hydro-forming of magnesium alloy sheet. The simulation results are in good agreement with the experimental ones, and the feasibility of warm hydro-forming of magnesium alloy sheet is verified. According to the numerical simulations and forming experiments, the best process window for warm hydro-forming of l mm thick AZ31B magnesium alloy sheet was obtained. The hot oil constant temperature hydraulic forming technology can enrich the forming process of magnesium alloy and provide a new perspective and technical basis for warm forming of other hard-to-deform metal materials.

Deformation and Stress Analysis of Sheet Hydroforming in Car Frame T-Joint

Abstract: Hydroforming is a relatively new metal forming process that offers many advantages over traditional cold forming processes, including the ability to produce more complex components with fewer operations. For certain geometries, hydroforming technology makes it lighter, stiffer, cheaper to manufacture, and requires less blanks, resulting in less material waste. This paper focuses on the analysis of composite T-joints which are used in automobiles under various loads. It is modelled analysed using CATIA V5 and ANYSYS software’s respectively. There are several studies on design optimization of automotive T-joints. This paper depicts deformation and stress analysis of TJoint, when made using sheet hydroforming. Keyword: Hydroforming, Metal Forming, Cold Forming, T-Joint, Catia, Ansys

Punch-less and die-less sheet hydroforming process for manufacturing of serpentine-shaped micro-channels in ultra-thin sheets

In the present work, novel serpentine-shaped micro-channels were successfully fabricated in ultra-thin sheets of AA1050, C101, and SS304 materials using the sheet hydroforming (SHF) process. In-house fabrication methods, namely punch-less SHF and die-less SHF processes were designed and developed on a 20-t press to manufacture these channels. The finite element (FE) modeling of both processes was developed for the prediction of the deformation behavior of these sheets. The elasto-plastic FE models incorporated the elastic properties, Barlat 89 anisotropic yield model, and Hollomon hardening law for all the three sheets, and their corresponding forming limit diagrams (FLDs) were implemented as damage criteria. It was observed that the maximum pressure was 28 MPa and 32 MPa for the punch-less and die-less SHF process, respectively. The manufacturability of the hydroformed channels was examined through channel depth, aspect ratio, and thickness distribution. The average channel depth and aspect ratio were found to be higher in the case of the die-less SHF compared to punch-less SHF. The failure occurred in the AA1050 channel under plane strain deformation mode near the die corner region and punch corner region for punch-less and die-less SHF processes, respectively, indicated by a sudden dip in the thickness distribution profile. Moreover, the surface quality of the formed channels was investigated through surface roughness value, and this was further correlated with effective plastic strain incurred in the deformation process. It was observed that the surface roughness of the deformed channels fabricated by the punch-less SHF process was lower than those formed through the die-less SHF process in the present study.

Deformation of large curved shells using double-sided pressure sheet hydroforming process

Large, thin-walled, and curved surface shells are challenging to deform using traditional forming technologies owing to wrinkling and rupture defects that coexist during the deformation process. In this study, the process of double-sided pressure sheet hydroforming (DSHF) was developed to overcome these issues and fabricate large curved components integrally. A theoretical analysis model was established by considering the stress and strain distributions at varying double-sided pressure ratios during DSHF. Simulations and experiments were conducted using the DSHF process on a hemispherical shell to analyse the effects of the pressure ratio on deformation behaviour, stress and strain, thickness distribution, and deformation defects. Furthermore, a phenomenon called “planar deformation state” was observed, and the stress state was optimised by setting a proper pressure ratio. Under this condition, the thickness distribution was improved and the formed curved shells were free from wrinkling and rupture defects. A CNC sheet hydroforming machine developed by Harbin Institute of Technology was employed to perform a case study of the DSHF process. Lastly, to demonstrate the application of the proposed process, an aluminium-alloy dome with a diameter of 3 m and a uniform thickness distribution was fabricated.

2枚板･3枚板ハイドロフォームの成形技術

Sheet hydroforming using high- and ultra high-strength steel has the potential to realize the manufacture of lightweight and complex car parts. In this study, forming characteristics and limits in sheet hydroforming with the material inflow of welded double blanks (double sheet hydroforming) without a blank holder are investigated by finite element (FE) analysis. On the basis of the obtained results, technology of welded triple blanks (triple sheet hydroforming) is demonstrated in experiments. The main results are as follows. (1) In double sheet hydroforming, wrinkles occur owing to the difference between the upper and lower material inflows. (2) The limits of wrinkle occurrence depend on the differences between the upper and lower die circumferences, the upper and lower sheet tensile strengths, and the upper and lower sheet thicknesses. (3) The formable range of double sheet hydroforming using dies with concave and convex beads differs, even in the same upper and lower die circumferences. (4) Two methods of triple sheet hydroforming are proposed. Experimental products have no defects. It is confirmed that the new methods are effective in reinforcing automotive parts.

Determination of Limit Drawing Ratio of SS 304 Steel using Sheet Hydroforming Process with Female Die

Sheet hydroforming with female die process (SHF-D) is easily applicable without pressure and blank holder force control compared to the sheet hydroforming with punch process. Shallow parts can be produced easily with using SHF-D process which is used a lower cost production method in a wide variety of sectors. Limiting drawing ratio (LDR) is indication of formability of sheet metals is determined by using cylindrical punch die. In this study, for the first time, the LDRs of the SS 304 material with different thicknesses was determined experimentally by using the SHF-D instead of sheet hydroforming with punch unlike in the literature. Finite element analysis of SHF-D process has been realized. The results showed that relatively shallow sheet metal parts can be easily produced without the control of pressure and blank holder by means of SHF-D using obtained LDR. It is important to know the forming limit in the SHF-D, since it can be a more economical production method, especially in the manufacture of shallow and large parts used in the automotive and aerospace industries and obtain more quality products than that from classical deep drawing process. By knowing these ratios, die design and parts manufacturing can be realized less costly. The LDR was experimentally obtained as 1.82 with using the sheet hydroforming with female die for the SS 304. The FEA results are in good agreement with experimental results. So, it is useful to analyze the finite element method before designing the dies that will be used with the SHF-D.

DIE SHEET HYDROFORMING OF A COMPLEX-SHAPED AA2024-W AIRCRAFT SKIN PANEL — FROM CONCEPT TO FINAL COMPONENT

Product design in the early stages requires a more quantitative process to ensure that the simulation study's outcome will meet expectations. The purpose of this study was to determine whether a manufacturing simulation software package could effectively evaluate and validate the conceptualised blank and tooling to manufacture a sizeable complex- shaped aluminium alloy aircraft panel using die sheet hydroforming. Blank and tool concepts were conceptualised, evaluated, and validated digitally using the forming process conceptualisation cycle. Without the need to trial several blank and tool concepts physically, a significant saving was achieved using a resource-efficient development process. Even without modelling the hyperelastic rubber elements, a successful die sheet hydroformed simulation result was conducted. However, the study showed that a rubber-to-metal friction coefficient must be incorporated appropriately. The study further showed the lack of standard metrology methods in commercial simulation packages to evaluate a simulation result accurately. Simulation metrology is a new area of interest that requires further development. This research contributes to improving the sheet metal forming simulation process and, specifically, die sheet hydroforming process simulation. The study will benefit the aerospace and automotive industry and promote the adoption of digital manufacturing processes.

Evaluation of the formability of AA2198-T3 Al-Li alloy in warm sheet hydroforming

This study aims to investigate the formability of the AA2198-T3 Al-Li alloy in hydro-mechanical deep drawing (HMDD), through experimentation and finite element simulation. The effects of the most critical factors were studied: die cavity pressure and forming temperature; the forming temperature is selected at 298K and 423K. The Gurson−Tvergaard−Needleman model (GTN model) was employed to analyze the formability of AA2198-T3 Al-Li alloy and predict the fracture in the hydroforming of a cylindrical part. Both the numerical and experimental results showed that the increase of the pressure inside the liquid chamber, within a certain range, contributes to improve the formability of the alloy. Increasing the temperature would reduce the required pressure for sheet hydroforming. Notably, the appropriate chamber pressure was beneficial to form good quality parts with a relatively uniform wall thickness. By analyzing the fracture morphologies, the brittle fracture of AA2198-T3 plays a main role at room temperature, but the ductile fracture was shown at the elevated temperature.