Hydroforming Process Research Articles

Fertigungsprozessanalyse eines mittels Innenhochdruck-Umformung hergestellten Bauteils

Abstract Series manufacturers in the field of hydroforming do not always have the necessary database for predictive maintenance, especially for the production of complex hydroformed components. Small and medium-sized companies in particular often lack the resources to acquire, process and profitably utilize these data sets under production conditions. The IHU processes that occur in practice are usually highly complex, both in terms of geometry and against the background of additional process steps (punching, plunging). This results in large amounts of data and complex data analyses, which are reflected in the data processing costs. A data analysis is to be carried out on the basis of a complex hydroforming process and its additional benefit for quality management and predictive maintenance is to be explained.

Effect of strain state on the surface roughening for hydroforming of aluminum alloy tube based on cross-scale numerical modeling

The complex deformation behavior would result in surface roughening such as orange peel defect during the hydroforming process of aluminum alloy tubular parts. In order to control the surface quality of hydroformed tubular parts, the effect of strain state on the surface roughening for 2219 aluminum alloy tube was analyzed based on a cross-scale model. The model combined the crystal plasticity model and macroscopic finite element model. During the uniaxial tension, the surface morphology reveals an equiaxed pattern characteristic of orange peel due to the strain incompatibilities between grains, and the peak and valley are stretched along the tensile direction. The surface roughness under tension-compression plane strain state is the lowest due to the low through-thickness strain. In the biaxial tension region, the change rate of surface roughness gradually increases with the decrease of the second principal strain especially in the late deformation stage, and the surface features evolve from an orange peel pattern to a ridging pattern. The forming limit diagram under different strain states based on surface roughness was established to guide the optimization of hydroforming process. Compared with the one-step hydroforming, the surface roughness of the bulging peak of 2219 aluminum alloy tube using multi-step hydroforming with the axial self-feeding decreases obviously from 16.3 to 10.8 μm due to the significant reduction of the equivalent strain.

Real-Time Simulation of Tube Hydroforming by Integrating Finite-Element Method and Machine Learning

The real-time, full-field simulation of the tube hydroforming process is crucial for deformation monitoring and the timely prediction of defects. However, this is rather difficult for finite-element simulation due to its time-consuming nature. To overcome this drawback, in this paper, a surrogate model framework was proposed by integrating the finite-element method (FEM) and machine learning (ML), in which the basic methodology involved interrupting the computational workflow of the FEM and reassembling it with ML. Specifically, the displacement field, as the primary unknown quantity to be solved using the FEM, was mapped onto the displacement boundary conditions of the tube component with ML. To this end, the titanium tube material as well as the hydroforming process was investigated, and a fairly accurate FEM model was developed based on the CPB06 yield criterion coupled with a simplified Kim–Tuan hardening model. Numerous FEM simulations were performed by varying the loading conditions to generate the training database for ML. Then, a random forest algorithm was applied and trained to develop the surrogate model, in which the grid search method was employed to obtain the optimal combination of the hyperparameters. Sequentially, the principal strain, the effective strain/stress, as well as the wall thickness was derived according to continuum mechanics theories. Although further improvements were required in certain aspects, the developed FEM-ML surrogate model delivered extraordinary accuracy and instantaneity in reproducing multi-physical fields, especially the displacement field and wall-thickness distribution, manifesting its feasibility in the real-time, full-field simulation and monitoring of deformation states.

AN OVERVIEW ON SHEET METAL HYDROFORMING TECHNOLOGIES

The hydroforming process is a nonconventional method for producing sheet metal deep drawing pieces, under the direct or indirect action of a high pressure fluid on the inner or outer side of work piece wall. This process it`s known since the 1900s and it has continuously developed, being today a field of research in the universities from country and abroad. The design of the hydroforming process can be done according to empirical, analytical and numerical methods to obtain high precision of the hydroforming piece and to ensure a large deformation of the material. The hydroforming parts can be used in various fields such as the automotive, aircraft and aerospace industries, having relatively low costs compared to parts obtained by other types of processing such as rolling, forging or stamping. The paper gives an overview regarding the sheet metal hydroforming processes, methods and the equipment used, as well as the process limits and defects that can occur during hydroforming.

Ultrasonic-Assisted Granular Medium Forming of Aluminum Alloy 6063-T5: Simulations and Experiments

To address the challenges posed by the complex shapes of hollow parts, this study examined the ultrasonic-assisted granular medium hydroforming (UGMF) process for tubular components. The dynamics of the deformation behavior and deformation control during 6063-T5 aluminum alloy tube free forming by UGMF were studied via simulations and experiments. Based on the ABAQUS software platform, a coupled method based on finite element (FE) simulation analysis and discrete element (DE) analysis for the UGMF free forming process was used. The results showed that ultrasonic vibration (UV) could reduce the forming force required for expansion and promote the flow of material at the end to the forming area as well as inhibit the decrease in the wall thickness. The accuracy of the FE-DE coupled simulation model and a parabolic geometric model was verified by testing. The results found that UV enhances material flow, decreases the forming force needed, and minimizes damage to the granular surface.

Hydroforming and buckling of a longan-shaped pressure vessel with longitudinal tension rods

ABSTRACT The hydroforming process of a longan-shaped multi-segmented preform with longitudinal tension rods and the buckling behaviour of a hydroformed longan-shaped pressure vessel were numerically and experimentally investigated. The shape of the longan followed the Cassini oval equation, with a shape index of 0.1. A preform with a nominal size of 400 mm for the major axis, 396 mm for the minor axis and a wall thickness of 1 mm was fabricated. Two longitudinal tension rods with a radius of 3 mm and a length of 420 mm were employed in the multi-segmented preform, which was the first to use longitudinal tension rods in the preform. The numerical analysis and experimental results showed that the excessive deformation of the polar plates was significantly reduced. Simultaneously, the overall geometric accuracy of the hydroformed pressure vessel was significantly improved. The results of the analytical, experimental and numerical approaches are in good agreement with one another.

Deformation behavior and scale effects in microchannel hydroforming in ultra-thin TA1/CFRP fuel cell bipolar plates

Microchannels of fuel cell bipolar plates have complex shapes and dimensions at the microscale level, posing significant challenges for manufacturing. Additionally, for traditional bipolar plate materials, mainly based on graphite composites and metals, make it difficult to meet the increasing performance requirements. As the latest fourth-generation fiber-reinforced metal composites, Ti/CFRP laminates exhibit high impact resistance and stiffness after solidification and are electrically conductive, presenting broad prospects for application in bipolar plates. In this study, the metallic layer of the traditional Ti /CFRP laminate was miniaturized to microscale, and a new method for ultra-thin TA1/CFRP laminate low-constraint hydro-microforming was proposed. By combining theoretical modeling, numerical simulation, and process experiments, the deformation behavior and scale effects of the laminate, during the microchannel hydroforming process, were investigated under different process and structural parameters. A single-channel deformation mode was used to study the forming process and examine the impact of hydraulic pressure loading paths and temperature. Additionally, multi-channel and curved channel deformation modes were employed to elucidate the influence of section inclination, channel width, ridge width, and bending angle on the forming process. By varying the laminate thickness, grain size and friction status, the geometric, grain and friction scale effects, as well as the microscale mechanisms of ultra-thin TA1/CFRP laminates in microchannel forming, were explored. This study explores new avenues for the precise microforming of lightweight laminate structures and their application in fuel cell bipolar plates. It provides a theoretical foundation to address the challenges in the microchannel forming of laminates and improve forming accuracy and performance quality.

Experimental and numerical investigation of the damage state of Ti-6Al-4V alloy sheet in the tensile test, hydraulic bulging, and hydroforming processes

There has not been any damage prediction using Johnson-Cook’s (JC) hardening and damage model in the hydraulic bulging (HB) and hydroforming (HF), which are the advanced manufacturing processes, of the Ti-6Al-4V (Ti64) alloy. In the presented study, the damage behavior of the Ti64 alloy sheet in the HB and HF processes was investigated both experimentally and numerically for the first time to address the existing research gap. In this context, firstly, tensile tests (TT) were carried out on samples with different stress triaxiality values at three different tensile speeds, and the fracture morphologies of the samples were examined to evaluate whether it was appropriate to use the JC hardening and damage model. Since the fracture surfaces generally exhibit a ductile fracture morphology and are affected by stress triaxiality and strain rate, it was determined that it would be appropriate to use the JC hardening model and damage criterion to predict the damage of the Ti64 alloy in finite element analysis (FEA). Then, JC model parameters were determined by fitting the stress-strain curve obtained from the FEA and experimental tensile tests. In the HB experiments, bulging height and thickness thinning were predicted by FEA with an accuracy of 97% and 96.85%, respectively. In the HF experiments, the experimental burst pressure, die inlet radius, and base radius were predicted correctly at a rate of 92.5%, 95.5%, and 97.8%, respectively. Also, the thickness of the sample showed good agreement with the FEA results. The fracture zones in each process exhibited good agreement with the experimental results. Thus, it has been demonstrated that the JC damage criterion can be successfully applied in FEA if the Ti64 titanium alloy is damaged in various processes.

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.

Numerical Investigation on Influence of Grooves on Tube Hydroforming Process of Aluminium Alloys

For several decades, scientists and engineers have been using the tube hydroforming (THF) process for numerous applications in the automotive and aerospace industries. The inert advantages like weight reduction without compromising on strength, improved part quality, better surface finish, and reduced tooling costs have motivated the use of THF in the fabrication industry. The presence of grooves on the pre-forms was found to immensely help in increasing the pressure-withstanding capacity of the THF tubes, in addition to reducing the stress concentration and achieving the near-net shape during the THF process. This project involves the development of a detailed Finite Element Model, for the THF process. Numerical analysis is carried out in two stages: Stage-1: Groove Formation, and Stage-2: Final THF tube formation. In Stage 1, the numerical model investigates the formation of grooves, predicting the amount of internal pressure and axial feeding that are required to accurately form them. In Stage 2, numerical simulations focus on the actual THF process. This two-stage THF process (Grooved-THF) was compared to a single-stage Generic THF process. The results indicate the Grooved-THF to be producing a relatively lower thickness reduction with a more closely formed corner radius compared to the generic case. The work also involves multi-objective optimization of the process parameters like the number of grooves, coefficient of friction, internal fluid pressure, and die corner radius using the DOE technique – RSM. The results indicate the number of grooves and the friction coefficient to be the most influencing parameters in the THF process.

Enhancing formability of Ti-6Al-4V cylindrical cups by pulsating hydroforming process: Experimental, numerical and microstructural investigations

Ti-6Al-4V alloy sheet is an engineering material that is widely used due to its superior properties such as high strength-to-density ratio besides high temperature and corrosion resistance. However, its low formability at room temperature limits its wider applications. In this study, a cylindrical cup was hydroformed using a female die to examine how the pulsating effect would result under frictional conditions. Initially, finite element simulations were performed to design a proper die geometry. Next, forming tests were run on Ti-6Al-4V blanks under pressure increased monotonically and with pulsation, and microstructural analyses were performed on the formed specimens. The effects of pulsation frequency, amplitude, and base pressure on the formability were investigated. The nose radius/thickness ratio, maximum thinning, bursting pressure, and die-filling ratio measured on the specimens formed under monotonic and pulsating loadings were compared, and the improvement in the formability was demonstrated. An increase of 38.5 % in bursting pressure occurred and the nose radius of the part was decreased up to 30 % with pulsating loading. The die-filling ratio was improved from 87.9 % to 95.3 % with optimized pulsation parameters. The underlying microstructural reasons for the improved formability were elaborated using XRD, SEM, and TEM analyses.

Automatic Optimization of Initial Blank Shape in Production of All Kinds of Rectangular Parts in Computer Aided Hydroforming Process

Automatic Optimization of Initial Blank Shape in Production of All Kinds of Rectangular Parts in Computer Aided Hydroforming Process

A novel active hydroforming & curing process to manufacture GLARE laminates: Numerical and experimental investigations

Fiber Metal Laminates (FMLs) are preferable thin-walled structures in several fields for their exceptional mechanical properties. However, how to manufacture thin-walled FMLs structures with complex shapes and guarantee the high mechanical properties is still a challenge. To address these, this paper proposes an innovative hybrid forming method, referred to as active warm hydroforming and curing, to enhance the formability and performance of FMLs in GLARE form by combining the forming and curing process into a single step. The hybrid method was verified on a box-shaped part as a proof-of-concept to assess the feasibility and parameter influence. Online curing was utilized to enhance efficiency and quality. The outcomes revealed that the new method increases the ultimate tensile stress by 12.1 % and reduces curing deformation from 3.1 mm to 1.3 mm compared to the vacuum bagging method. Furthermore, the critical parameters in forming of thin-walled structures, including blank holder force (BHF), pressure rate (PR), maximum pressure (MP), and forming temperature (FT), were identified using experimental, mathematical, and numerical approaches. Four defects in the formed thin-walled structures were observed and successfully eliminated through the control of these parameters. The method and results presented in this paper also provide direct guidance for optimizing the process parameters of FMLs warm hydroforming.

Hydroforming of double-layer Y-shaped tube controlled by a novel backward punch shape

PurposeA new backward punch shape was designed and used in the hydroforming process of double-layer Y-shaped tubes to achieve uniform wall thickness. This study focuses on the implementation and effectiveness of this novel punch shape.Design/methodology/approachA numerical simulation and experimental validation of the hydroforming process of double-layer Y-shaped tubes under various backward punch, replenishment ratios (left and right feed ratios) and internal pressure loading paths was performed using finite elements. During the hydroforming process, an analysis was made on the distribution of stress, strain and wall thickness in both the inner and outer layers of the Y-shaped conduit.FindingsThe novel backward punch parallel to the main tube has been found to improve the distribution of wall thickness in Y-shaped tubes. By controlling the feeding ratio and modifying the loading path of the internal pressure, it is possible to obtain the optimal forming part of the double-layer Y-shaped tube. The comparison between the simulation and experimental results of the double-layer Y-shaped tube formed under the optimal path indicates that the error is within 5% and the distribution of wall thickness is consistent.Originality/valueA novel backward punch technique is employed to control the hydroforming process in a Y-shaped tube. A study on hydroforming of double-layer Y-shaped tubes with asymmetric features and challenging forming conditions is being suggested.

Effect of loading paths on hydroforming ability of stepped hollow shaft components from double layer pipes

The step hollow shaft components are composed of two layers of different materials, they are formed using tube hydroforming process due to its high strength and rigidity, low weight and flexible profiles, compared to traditional casting, welding, and forming methods. These products are effectively used in industries such as the automotive, shipbuilding, aerospace and defense, and oil and gas sectors. The success of various double layer pipe hydroforming process depends on several factors, with the most important being the internal pressure path and axial loading path. This paper presents research on the effect of input loading paths on the hydroforming ability of a different two-layer metal structure - an outer layer of SUS304 stainless steel and an inner layer of CDA110 copper - using 3D numerical simulations on Abaqus/CAE software. Output criteria were used to evaluate the forming ability of the formed components, including Von Mises stress, Plastic strain component (PEmax), wall thinning, and pipe profile, based on which the input loading paths were combined during the forming process. These output criteria allow for more accurate predictions of material behavior during the hydroforming process, as well as deformation and stress distribution. This can support the design process, improve product quality, reduce errors, and increase production efficiency. The research results can be applied as a basis for optimizing load paths for the next experimental step in the near future, for undergraduate and graduate training, as well as allowing designers and engineers to optimize the process of hydroforming of different 2-layer tubes, reducing costs, improving accuracy, flexible design, minimizing risks, and increasing efficiency

Internal Hydroforming of Large Stainless-Steel Eggshells from Stepped Preforms

The internal hydroforming of large stainless-steel eggshells from a stepped preform is investigated in this paper. The nominal major and minor axes of the eggshell were 1537 and 1070 mm, respectively. The stepped preform was fabricated from thin-walled (1.9 mm thick) stainless-steel sheets and comprised twelve conical segments inscribed inside the target eggshell. The preform was then hydroformed, and its wall thickness and shape were measured. The yield load distribution and material hardening of the hydroforming process were investigated analytically. Nonlinear finite-element analyses were employed to further investigate hydroforming behaviors and the effect of weld lines on hydroforming. The experimental, numerical, and analytical results were consistent. The results confirm that, during the hydroforming process, considerable springback occurs for large eggshells, which greatly affects forming precision. However, this effect can be reduced by accounting for the strengthening effect of weld lines.

Predicting the forming limits in the tube hydroforming process by coupling the cyclic plasticity model with ductile fracture criteria

This study presents a one-surface plasticity constitutive model combined with phenomenological and micromechanical damage models to be applied to the large plastic deformation during tube hydroforming. These factors lead to simulating the Bauschinger effect and transient behavior in large plastic strain ranges and predicting fracture onset. By using the integration approach, a numerical integration algorithm of implementation by explicit schemes was carried out. A comparison of several cyclic loading tests between experiments and numerical simulation was accomplished. The accuracy of these models is verified, which could be expanded to a large strain range forming process. Adopting the proposed models, finite element modeling is performed in the tube hydroforming process. The simulation and experimental results comparison showed that the proposed framework accurately predicted the tube formability in the hydroforming process.

An Attempt to Evaluate and Optimize the Hydroforming of Fiber Metal Laminates with the Comprehensive Forming Limit Curve

Although some papers have studied the formability of fiber metal laminates (FMLs), there is still a lack of a standard criterion for the engineering field. To give a standard for predicting the failure and provide the optimized method of the hydroforming process for FMLs, a comprehensive forming limit curve (FLC) was established by a hydro-bulging test method. The influence of pressure rate (PR), blank holder pressure (BHP), and temperature (T) was studied in this paper. Both theoretical and experimental results showed that the higher BHP and PR have a significant negative effect on limit height, while increased T has a positive effect. Moreover, the semi-cured forming of a real part was evaluated by this FLC for the very first time and the improvement suggestions of process parameters were given based on the comprehensive research. Finally, the real part that met the quality requirements was obtained by numerical simulation and trial production, which verifies the effectiveness of this comprehensive FLC.

Improvement of material flow in tube hydroforming by advanced sealing methods

In this paper, two advanced sealing methods are proposed to enhance the formability of aluminium alloys in the tube hydroforming process. These methods are aimed at omitting friction force at the contact area between the tube and the die in the feed region and facilitating the material flow to the deformation region. The advanced sealing methods are numerically and experimentally examined against the conventional sealing method by conducting the free bulge test on AA6063 aluminium tubes. The deformation mechanics are deeply analysed in the principal strain space to identify the influence of the sealing methods on deformation paths. In addition, the effectiveness of the advanced sealing methods is evaluated under different lubrication conditions and contact lengths in the feed region. Results show that in the advanced sealing methods compared to the conventional one, the thickness in the feed region does not increase and the necking occurs in larger in-plane strains, leading to a higher bulge height. Results also allow concluding that a higher bulge height is formed using the second advanced sealing method, in which the tube is pressurized from both sides in the feed region. Thus, the advanced sealing methods are recommended for tube hydroforming of aluminium alloys with low formability.

ALTERNATIVE NUMERICAL SIMULATION APPROACH FOR OBTAINING FLC/FLD

To be able to predict the forming behavior of sheet metal parts by simulation, it is necessary to determine the FLD1 (Forming Limit Diagram) curves of the sheet material that is subjected to bending, hemming, deep drawing, progressive forming, embossing, hydro-forming processes. To determine such curves, the usual practice is to carry out a series of experiments that need to be repeated many times, and therefore it takes a long time to finalize them [1], [2], [3], [4], [5], [6]. Not to mention undertaken experiments are very detailed and need tedious and careful work has to be done such as screen printing on the material and doing simultaneous optical measurements during the experiments. Indeed, a fully equipped laboratory and qualified lab personnel are required for such experiments which may not be easily found. When it's found, there is usually six months to a year, queue to conduct such experiments.
 Because of these difficulties, many academic institutions and manufacturing sites develop their in-house test equipment if funding is available. If not, it is dependent on research whether it comes to an end or whether it can continue without it.
 An alternative method developed for extracting FLD/FLC curves is using today’s state-of-the-art simulation technology. This method requires two main inputs;
 a) Tensile test of the material
 b) An explicit solver
 The scope of this paper is to detail this method such that the findings in this document can be reproduced when the mentioned requirements are satisfied. Therefore, all data used in charts, a high-resolution image, and a sample Abaqus input file are provided as supplemental data [7].
 The results from the simulations of FLD/FLC were compared to published literature [13] [14] to confirm their compliance with experiments. The comparison showed good results and demonstrates that expensive and time-consuming FLD/FLC experiments are not necessary when the mentioned requirements are met.