Tube Hydroforming Process Research Articles

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.

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.

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.

An Investigation on Forming and Fracture Behavior of Austenitic Stainless Steel Tubes

Tube hydroforming (THF) is an unconventional manufacturing technique that uses pressurized fluid in place of conventional punches to deform the tubular blank into the desired shape. In THF process tubular blank is deformed it into the final shape by applying fluid pressure mostly by water using water intensifier through axial punches. Tube hydroforming is mainly used to produce hollow components using tubular blank which find applications in automobile industry, particularly for exhaust systems. The formability of Austenitic stainless steel tubes as function of microstructure is not focused much in literature. Hence, in this study, formability of Austenitic stainless steel tubes is studied as a function of boundary conditions and bulge width (L/D ratio) and correlated with microstructure. Microstructure resulting in axial feed condition showed better formability than microstructure resulting in fixed feed condition. Similarly, formability and fracture behavior of tube predicted with finite element-based simulation using PAMPSTAMP 2G solver found results, particularly bulge height and fracture location are in good agreement with experimental values. The observed fracture mode noted was ductile both for axial feed condition and fixed feed condition as the fracture consists of voids and micro voids. Fracture location was in base metal just, besides, weld line for axial feed condition and fracture location was in base metal which is little away from weld line for fixed feed condition.

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

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.

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.

Numerical and experimental investigation of the ultrasonic vibration effects on the tube hydroforming process in a die with a square cross-section

Numerical and experimental investigation of the ultrasonic vibration effects on the tube hydroforming process in a die with a square cross-section

Friction Modelling for Tube Hydroforming Processes-A Numerical and Experimental Study with Different Viscosity Lubricants.

The final quality of sheet and tube metal–formed components strongly depends on the tribology and friction conditions between the tools and the material to be formed. Furthermore, it has been recently demonstrated that friction is the numerical input parameter that has the biggest effect in the numerical models used for feasibility studies and process design. For these reasons, industrial dedicated software packages have introduced friction laws which are dependent on sliding velocity, contact pressure and sometimes strain suffered by the sheet, and currently, temperature dependency is being implemented as it has also a major effect on friction. In this work, three lubricants having different viscosity have been characterized using the tube-sliding test. The final aim of the study is to fit friction laws that are contact pressure and sliding velocity dependent for their use in tube hydroforming modeling. The tests performed at various contact pressures and velocities have demonstrated that viscosity has a major effect on friction. Experimental hydroforming tests using the three different lubricants have corroborated the importance of the lubricant in the final forming of a triangular shape. The measurement of the axial forces and the final principal strains of the formed tubes have shown the importance of using advanced friction laws to properly model the hydroforming process using the finite element modeling.

Finite Element Analysis on Hydroforming of CFRP/SS304 Composite Tube with different Fiber Orientation Stacking Sequence

In this paper, a finite element-based approach to the tube hydroforming process of SS304/CFRP material with different stacking sequences was performed in an effort to reveal the failure phases at different stacking angles. The effort to produce hybrid composite tubes through tube hydroforming with composite reinforcement resulted in laminate failure at all the proposed fiber orientation angles. A comparative study of strain energy dissipation at these different stacking angles is further presented. The results show that the 00/900 stacking is considered the strongest stacking angle requiring the least strain energy absorption to initial failure of approximately 50 % more as compared to the ±300 and ±600 stacking angles. The proposed method was more adequate for predicting the strain energy, matrix deformation, and fiber damage when simulating the events.

Quality comparison of Y-shape joints by tube hydroforming with and without counterforce

The design capability, strength, and structural rigidity provided by tube hydroforming (THF) are successfully used in many applications to produce high-strength parts and assemblies with improved mechanical properties, optimized service life, and weight features. In tubular metal forming, output parameters such as branch height, distribution of tube wall material thickness, distribution of damage factor, metal flow, effective stress, and effective strain significantly affect the quality of the product after the forming process. Therefore, this paper aims to evaluate the manufacturing quality of Y-shape joints from AISI304 material steel tube through output parameters of THF process with and without counter punch force on numerical simulation base. The Finite Element Method (FEM) has become an established feature of metal forming technology. The objective of FEM is to replace costly and elaborate experimental testing with fast, low-cost computer simulation. The simulation study uses finite element method-based virtual prototyping techniques to characterize output parameters, gain insight into strain mechanics, and predict mechanical properties of shaped components. The research results are presented clearly and unambiguously through the evaluation of 7 criteria to compare the quality of the specimens hydroformed by two surveyed cases and optimize the crucial input process parameters. And these data can be applied in experiments, more efficient product and process design, calculation, and control of input parameters avoiding costly trial and error in industrial production. The findings can help technologists optimize process parameters in the hydroforming process of products with protrusion from a tubular blank

Evaluation of Circumferential Mechanical Properties of Tubular Material by Flaring Test

The investigation into the circumferential mechanical properties of tubular materials has been receiving increasing attention, since the tube hydroforming process has been used in the tubular materials forming field, because the circumferential mechanical properties have a significant effect on the hydroformability of the tubular materials. In the present study, a method for evaluation of the circumferential mechanical properties of the tubular materials with the flaring test was proposed. The expressions for the yield stress, strain hardening coefficient and exponent values of the tube were successfully derived based on the geometrical and mechanical relationships in the tube flaring test. To verify the reliability of this method, the calculated results of the yield stress, strain hardening coefficient and exponent values, obtained from the newly proposed method, were compared to the ones obtained with the conventional tensile tests. It was found that the method proposed in the current study is reliable, with high accuracy. The method is appropriate to evaluate the circumferential mechanical properties of the tubular materials.

Multi-step hydroforming process and wall thickness optimization of 5A02 aluminum alloy five-way tube with different branch diameters

The different branch diameters of five-way tube affect the design of loading internal pressure in the hydroforming process, where the large-diameter branch is broken more easily than the small-diameter one due to the same ultimate stress of tube material in one-step forming method. Therefore, the first four-way and then five-way of multi-step forming (FFTF) method and the first three-way and then five-way of multi-step forming (FTTF) method were proposed to fabricate the 5A02 aluminum alloy five-way tube with two kinds of branch diameters to avoid the burst of large-diameter branch tube. The finite element simulation of five-way tube hydroforming process shows that the height of small-diameter branch tube is lower and serious wrinkles appear at the large-diameter branch tube in the one-step forming and FFTF method. By optimizing the length of punch, a five-way tube with a big branch height and uniform wall thickness was obtained with the FTTF method. The approach of lengthening the punch in the experiment increased the height of formed branch and reduced the wall thickness reduction rate of five-way tube in FTTF method. Overall, the findings mentioned above cannot only offer guide in creating five-way tube with excellent quality, but also be taken as reference to the hydroforming studies on multi-way tube in the future.

Tribological Characteristics of Dual-Pressure Tube Hydroforming

Dual-pressure tube hydroforming (THF) is a tube hydroforming process variant whereby deformation of the tubular specimen is achieved by exerting fluid pressure on both the inside and outside surfaces of the tube. Dual-pressure THF experiments are conducted to study tribological conditions when producing pear-shaped and triangular parts. The pressure-loading paths are designed to exert pressure in oscillatory pattern: I.e., the pressure on the inside was alternated with pressure on the outside causing the tube to expand and contract/buckle as deformation progressed. During tube contraction, the metal-to-metal contact area is substantially reduced. This leads to reduction in friction stress at the tube-die interface, thus increasing formability. Comparing the geometries of the formed parts produced by dual-pressure THF and conventional THF reveals that the former results in a substantial increase in the protrusion height of a pear-shaped specimen.

Experimental investigation and analysis of thickness distribution in elliptically hydroformed Al6061T4 tube samples under different internal pressures

ABSTRACT In the present paper, the elliptical tube hydroforming samples have been deformed inside an elliptical die cavity with the help of internal pressure of water. Bulging thickness distribution of tube has been studied experimentally and numerically as well. The tube hydroforming process is depending on various hydroforming variables such as internal pressure, friction factor, axial force etc. In this experiment, axial feed is kept under constrained condition and performed under unique friction factor. The main attention of this paper is to measure the thickness at various major and minor axis points on tube sample deformed under different internal pressures. The percentage thinning of different major and minor axis points has been also discussed and plotted against simulated results. Finite element analysis (FEA) was carried out on elliptical samples using Abaqus software. The simulation results showed an agreement with the experimental data with some relative error which has been also plotted. Comparative results of incremental FEA prediction and experimental data have also been plotted with some deviation.

In-process feedback control of tube hydro-forming process

The present work will address the problem of designing an in-process control system for a tube hydro-forming process, controlling the tool filling forming a T-tube. The control problem is nontrivial as wrinkling and bursting will develop rapidly and, in most cases, are irreversible—thus, the control system must react fast and without extensive overshoot. The objective is to control the tool filling, reproducing a reference filling trajectory, where the controller input is defined as a correction of the reference forming pressure. The control system was verified experimentally, using four different error scenarios. Initially, the error was provoked, by manipulating the input signal, and for all three cases, the control system successfully eliminates both wrinkling and bursting. Finally, the material was changed going from an aluminum grade 5049-0 to 6060-T6 also; in this case, the control system eliminates the error and stabilizes the process. The control strategy and implementation was developed using numerical simulation (explicit finite element), and the controller implementation was reused directly in the experimental setup without manipulating or scaling the gain factors.

Material characteristics evaluation for DC04-welded tube hydroforming

Tube hydroforming (THF) technology is widely applied especially in the automotive and aircraft industries. Material characteristics of tubular workpieces should be evaluated in terms of bending and THF processes. A mathematical model, which combines the assumption of the elliptical contour of a bulged wall and the prediction equation of wall thickness, was designed to analyze the THF process and to obtain the strain–stress relationship of tubes. Material characteristics of a DC04-welded tube were obtained by using a self-designed THF test machine. Considering the effects of pre-work hardening, the material strain–stress relationships of the tube and original sheet blank were discussed. An approximate determination method was proposed to obtain the stress–strain curve of the tube by using the curve of the original sheet blank and the hardness of the tube and sheet blank. A suitable constitutive equation with pre-work hardening was applied to the DC04-welded tubes through simulation and experimental methods.

Prediction of softening kinetics and recrystallization texture in non-isothermally annealed bulged tubes using CPFEM and CA models

A hierarchically coupled cellular automata (CA) model, crystal plasticity finite element method (CPFEM), and thermal finite element (FE) model is developed to predict the softening kinetics of the bulged steel tube during non-isothermal annealing. Through the developed model, the kinetics of softening mechanisms including static recovery (SRV) and static recrystallization (SRX), as well as the recrystallization texture are predicted. Later, the Johnson-Mehl-Avrami-Kohnogorov (JMAK) model based on the predicted SRX data is developed to interpret the recrystallization behavior of the material. To perform this study, diverse experimental tests including tube hydroforming (THF), annealing, uniaxial tensile test, hardness test, as well as microstructure observations through optical microscopy and Electron Backscatter Diffraction (EBSD) tests on steel tube are performed. The obtained experimental data are utilized to calibrate and verify the implemented CPFEM model for simulation of THF process, thermal FE model for prediction of the local temperature over annealing time, and CA algorithm for modeling of the softening kinetics and texture evolution throughout the annealing process. The study shows that the predicted deformation characteristics, softening kinetics, recrystallization texture and temperature profile during non-isothermal annealing are in good agreement with experimental data. During the annealing process, a total of four stages for the kinetics of softening mechanisms is observed: No softening; SRV only; SRV dominant; and SRX dominant. During the progress of SRX, the behavior of recrystallization is abruptly changed, confirming that two different mechanisms are controlling the kinetics of transformation.

An application of a genetic algorithm based on Particle Swarm Optimization to a multiple responses problem arising in the Tube Hydroforming Process

An application of a genetic algorithm based on Particle Swarm Optimization to a multiple responses problem arising in the Tube Hydroforming Process

Warm Hydroforming Process under Non-Uniform Temperature Field for Magnesium Alloy Tubes

The warm tube hydroforming (WTHF) process of lightweight materials such as magnesium alloy contributes to a remarkable weight reduction. The success of the WTHF process strongly depends on the loading path with internal pressure and axial feeding and other process variables including temperature distribution. Optimization of these process parameters in this special forming technique is a great issue to be resolved. In this study, the optimization of the symmetrical temperature distribution and process loading path for the warm T-shape forming of magnesium alloy AZ31B tube was carried out by finite element (FE) analysis using a fuzzy model. As a result, a satisfactory good agreement of the wall thickness distribution of the samples formed under the optimum loading path condition can be obtained between the FE analysis result and the experimental result. Based on the validity validation of FE analysis model, the optimization method was applied to other materials and forming shapes, and applicability was discussed.