Showing papers on "Hydroforming published in 2020"

A state of the art review of hydroforming technology: its applications, research areas, history and future in manufacturing

Abstract: Hydroforming is a relatively new metal forming process with many advantages over traditional cold forming processes including the ability to create more complicated components with fewer operations. For certain geometries, hydroforming technology permits the creation of parts that are lighter weight, have stiffer properties, are cheaper to produce and can be manufactured from fewer blanks which produces less material waste. This paper provides a detailed survey of the hydroforming literature of both established and emerging processes in a single taxonomy. Recently reported innovations in hydroforming processes (which are incorporated in the taxonomy) are also detailed and classified in terms of “technology readiness level”. The paper concludes with a discussion on the future of hydroforming including the current state of the art techniques, the research directions, and the process advantages to make predictions about emerging hydroforming technologies.

Process Development for a Superplastic Hot Tube Gas Forming Process of Titanium (Ti-3Al-2.5V) Hollow Profiles

Abstract: Tube forming technologies based on internal forming pressures, such as hydroforming or hot tube gas forming, are state of the art to manufacture complex closed profile geometries. However, materials with excellent specific strengths and chemical properties, such as titanium alloys, are often challenging to shape due to their limited formability. In this study, the titanium alloy Ti-3Al-2.5V was processed by superplastic hot tube gas forming to manufacture a helically shaped flex tube. The forming process was investigated in terms of process simulation, forming tool technology and process window for the manufacturing of good parts. Within a simulation study, a strain rate optimized forming pressure–time curve was defined. With the newly developed tool design, forming temperatures up to 900 °C and internal forming pressures up to 7 MPa were tested. A process window to manufacture good parts without necking or wrinkling has been successfully identified. The experiment data showed good agreement with the numerical simulations. The detailed study of the process contributes to an in-depth understanding of the superplastic forming of Ti-3Al-2.5V during hot tube gas forming. Furthermore, the study shows the high potential of superplastic hot tube gas forming of titanium alloys for the manufacturing of helical flex tubes and bellows.

Design of T-shaped tube hydroforming using finite element and artificial neural network modeling

Abstract: Tube hydroforming (THF) is a frequently used manufacturing method in the industry, especially on automotive and aircraft industries. Compared with other manufacturing processes, THF provides parts with better quality and lower production costs. This paper proposes a design approach to estimate the T-shaped THF parameters, such as counter force, axial feed, and internal pressure, through finite element (FE) and artificial neural network (ANN) modeling. A numerical database is built through Taguchi’s L27 orthogonal array of experiments to train the ANN. The micromechanical damage model of Gurson-Tvergaard-Needleman is used with an elastoplastic approach to describe the material behavior. This study aims to find the combinations of THF parameters that maximize the bulge ratio and minimize the thinning ratio and wrinkling. The numerical results obtained by the FE model show good correlation with the results predicted by the ANN.

Theoretical and experimental study of the free hydroforming of egg-shaped shell

Abstract: This study investigated the free hydroforming of a stainless-steel egg-shaped shell. An egg-shaped shell is a promising geometry for deep pressure hulls. The length and width of the egg-shaped shel...

An investigation on tube hydroforming process considering the effect of frictional coefficient and corner radius

Abstract: Tube hydroforming (THF) technology is mostly used in automotive and aerospace industries because of its benefits like high precision, less weight and forming capability of complex shapes. F...

Hybrid forming of sheet metals with long Fiber-reinforced thermoplastics (LFT) by a combined deep drawing and compression molding process

Abstract: In this article, a newly developed method for forming metal sheets together with long fiber-reinforced thermoplastics (LFT) to hybrid parts is presented. The idea of combining two different materials in one part is nothing new, but most of the existing processes use at least separate production techniques for each material and an additional joining operation. The special characteristic of this new process is realized by a combined forming tool for both sheet metal and LFT to create a hybrid part with only one necessary and simultaneously executed process step. Besides contact to the punch, the metal sheet is also formed by the molten LFT material, which behaves like a hydraulic fluid in hydroforming processes. With this method, it is possible to reduce the thickness of sheet metal components by adding a LFT reinforcement structure. The interface connection between the metal sheet and LFT is realized by using a bonding agent, which is previously applied to the metal sheet via coil or powder coating. To achieve this hybrid forming process, new tool and sealing concepts have been developed and the corresponding process parameters were identified and optimized. As a result, the innovative process offers a cost- and time-efficient solution for multi-material lightweight design.

Effect of hydroforming process on the formability of fiber metal laminates using semi-cured preparation

Abstract: In this study, the cup part of fiber metal laminates (FMLs) was formed by a method which combines the semi-cured preparation and hydroforming processes. The FMLs in this research were produced by using glass woven fiber prepreg and aluminum 2024-T3. The process parameters were designed by Taguchi method, and the optimized parameters (3 mm pre-bulging height, 15 MPa cavity pressure, 4 MPa pre-bulging pressure and 1.15 mm clearance between blank holder and die) were obtained by range analysis. The part without defect can be obtained using the optimized parameters. The thinning rate of each layer, stress-strain distribution, and the failure modes were analyzed with experiments and numerical simulations. The results show that the middle layer has a great influence on the thinning, stress-strain distribution, and fracture modes in different directions. Numerical simulation can be used for predicting the thinning rate and fracture location. Small-size FML parts can be fabricated directly using the semi-cured hydroforming process, which can improve the production efficiency and expand applications of FMLs.

Tube hydroforming optimization using a surrogate modeling approach and Genetic Algorithm

Abstract: The quality of a product obtained by hydroforming process is influenced by the geometrical, material and process parameters. In this paper, to predict an acceptable T-shaped tube with minim...

Numerical and experimental studies on thin-walled aluminum alloy tube hydroforming using differential lubrication method

Abstract: In this paper, it was analyzed that the friction forces that affected the material flow were influenced by the friction coefficient and the load path of internal pressure and feeding in T-shaped tube hydroforming process. Therefore, a novel differential lubrication method was proposed to adjust the material flow through changing the friction coefficient in the asymmetric zone in the T-shaped tube besides the loading path design method. The differential lubrication zones in T-shaped tube were divided, and a method called intermediate semiring differential lubrication was designed. The effects of differential lubrication and traditional uniform lubrication methods on the wrinkle, height of branch tube and wall thickness distribution of the T-tube were investigated under the same loading path of internal pressure and axial feeding. Meanwhile, the differential lubrication methods were also simulated under the different loading paths of the internal pressure and axial feeding. The differential lubrication experiments of T-shaped tubes hydroforming were carried out with fluorosilicone grease and PEFT film as lubrication medium. The simulation and experimental results showed that the differential lubrication method more effectively avoided wrinkles in the back zone of the main tube, increased the height of branch tube and weakened the thickening than the traditional uniform lubrication method. And it was a promising way to improve the formability of T-shaped tube hydroforming and reduced the over-reliance on the loading path.

Influence of process parameters on thinning ratio and fittability of bellows hydroforming

Abstract: Metal bellows are widely used in piping systems, aerospace, automobile and other industries due to their favourable properties including absorption of expansion, light weight and flexibility. In this paper, the fittability was presented to evaluate the convolution shape precision of the metal bellows. By establishing a finite element model of bellows hydroforming process during the bulging and forming stages, the influence of internal pressure, axial feeding and feeding loading path on the wall thickness variation and fittability of one-convolution bellows was investigated. On that basis, the hydroforming process of multi-convolution bellows was studied, and an experiment was carried out. The results showed that with the increase in internal pressure, the wall thickness of the bellows thinned overall, and the fittability of the root zone of the bellows gradually deteriorated. Some region near the crown zone did not fit the dies well when the internal pressure is small. To improve the fittability of the bellows, the actual axial feeding should be a bit less than the theoretical axial feeding. It is of importance in developing the hydroforming technique and improving the hydroforming quality of bellows.

A Novel Approach to Predict Wrinkling of Aluminum Alloy During Warm/Hot Sheet Hydroforming Based on an Improved Yoshida Buckling Test.

Abstract: In order to predict the wrinkling of sheet metal under the influence of fluid pressure and temperature during warm/hot hydroforming, a numerical simulation model for sheet wrinkling prediction was established, taking into account through-thickness normal stress induced by fluid pressure. From simulations using linear and quadratic elements, respectively, it was found that the latter gave results that were much closer to experimental data. A novel experimental method based on an improved Yoshida Buckling Test (YBT) was proposed for testing the wrinkling properties of sheets under the through-thickness normal stress. A wrinkling coefficient suitable for predicting wrinkling was also presented. Based on the numerical simulations, an experimental validation of wrinkling performance was conducted. Ridge-height curves measured along the main diagonal tensile direction of the sheet were presented and showed that the wrinkling prediction criterion provided good discrimination. Furthermore, the wrinkling properties of several different materials were simulated to evaluate the accuracy of the prediction method, and the results revealed that the improved YBT gave good predictions for wrinkling in the conventional sheet metal forming process, while the prediction results for wrinkling in warm/hot sheet hydroforming were also accurate with the fluid pressure of zero.

Research on the selection principle of upper sheet in double-layer sheets hydroforming

Abstract: By combining the advantages of sheet hydroforming and multi-layer sheet deep drawing in wrinkling suppression, double-layer sheets hydroforming process was proposed. Different from the multi-layer sheet deep drawing, the two sheets are not bonded together, the upper sheet is introduced to eliminate the wrinkling defects occurred in the formed lower sheet. Therefore, how to determine the appropriate upper sheet is the key point in this process. Based on this, some investigations in selecting the appropriate upper sheet have been down, but the selection principle for the appropriate upper sheet is still ambiguous. To make clear this, in this paper, a semi-ellipsoid curved sheet part made of 2198 Al-Li alloy with an axial length ratio of 0.9 was chosen as the target part, by changing the thickness of the upper sheet (5A06-O aluminum alloy); the primary and secondary order of the anti-wrinkle ability and interfacial friction stress in suppressing the wrinkle defects were investigated and the selection principle for appropriate upper sheet is obtained.

Experimental and numerical study on warm single-point incremental sheet forming (WSPIF) of titanium alloy Ti–6Al–4V, using cartridge heaters

Abstract: The single-point incremental forming process is an emerging process, which presents an alternative to the conventional sheet metal forming processes like hydroforming and drawing. It is known to be perfectly suited for prototyping and small series. For example, the incremental forming process offers the possibility of manufacturing medical prosthesis or implants specific to each patient, which are more comfortable and guarantee better performance. The customization of this type of product brings better efficiency and better comfort. However, the manufacture of customized titanium prosthesis is not yet industrialized, mainly due to the geometrical inaccuracy of the parts and inability to form parts with a high wall angle. In fact, considerable forces and damage occur during the process limiting the formability. Several studies have already shown that increasing the working temperature allows improving the formability. A reverse engineering approach associated with warm single-point incremental forming process, in order to produce a customized titanium prosthesis, can make the ability to be exploited in the industry to manufacture titanium alloys medical shapes. In this paper, an experimental and numerical study of the warm incremental process based on the use of heat cartridges is performed. The objective is to demonstrate that our low-cost heating system can be used in forming limit angle similar to that obtained with expensive laser heating. The effects of the wall angle at 450 °C on the forming force, thickness distribution and displacement are investigated by producing a truncated cone with Ti–6Al–4V thin sheets. Results show that the formability is significantly improved with the heating. In addition, a thermo-viscoplastic constitutive model is used to simulate the warm incremental forming process. A comparison of the numerical and experimental results shows that the finite element model gives accurate predictions.

Characterization and optimization of the hydroforming process of AISI 316L steel hydraulic tubes

Abstract: Hydroforming is a metal forming technology that enables the fabrication of complex parts in a low cycle time. The process is based on the plastic deformation of a blank sheet using a pressurized fluid. This paper focuses on the design of a tube hydroforming (THF) process to replace the current cut-and-weld practice for components produced by a company. Specifically, the study focuses on the characterization and optimization of the THF process for stainless steel T-joint parts produced in two sizes: small and large. The new production must improve the final components’ quality and maintain the technical requirements of the previous one, especially in terms of the parts’ geometry (in particular, the third branch minimum height and thickness) and material (AISI 316L), with competitive production costs. Accordingly, the process optimization is performed in three sequential steps. Initially, the process is characterized by the material flow stress and the friction between a tube and die. Subsequently, this information is used to develop a finite element method (FEM) model, which is validated based on experimental data. The FEM is used to optimize the process parameters (pressure, stroke, and trust force of the counterpunch) to improve the final component quality and guarantee the specific dimensional requirements. Finally, further improvements of the process are implemented (initial precrash of the tube, optimal length of the blank tube, and calibration pressure to avoid wrinkles in the final component). After the THF process optimization, emphasis is placed on the punch geometry. A study is conducted to avoid stress concentrations that may cause punch breakage. The results of this study allow the minimization of tube thinning during the hydroforming process, and guarantee the target value for the third branch height with minimal material consumption. Moreover, the evaluation of different geometrical alternatives allows the stresses acting on the punches to be reduced by 45%.

Loading path design of thin-walled aluminum alloy T-shaped tube hydroforming process based on the control of limit pressure

Abstract: Due to the influence of pressure control precision, the actual pressure in hydroforming process for the tube is usually greater than the design pressure, which causes the fracture of tube. The loading path of T-shaped tube hydroforming process was designed based on the control of limit pressure. First, the limit pressure of tube Pmax was obtained by improving the internal pressure until the tube cracked in the T-shaped tube hydroforming process without the feeding and a theoretical model for predicting instantaneous pressure is developed. Second, the tube bulge height Hmax and the maximum feeding Dmax were explored through manual operation of feeding and pressure in hydroforming machine, in which the overflow pressure is set to Pmax by using an overflow valve; finally, the loading path of internal pressure and feeding was designed using the ladder growth and linear growth in T-shaped tube hydroforming experiment in which the maximum pressure, the maximum feeding, and the overflow pressure (equal to internal pressure) were set to Pmax, Dmax, and Pmax, respectively. The results show that the obtained limit pressure Pmax can avoid the overpressure of the tube and restrain the fracture of the tube through the action of the overflow valve. Meanwhile, the accuracy of the prediction model to figure up Pmax was verified through experiments: the theoretical prediction value of the established model was consistent with the experimental true value. Compared with the T-shaped tube formed by linear loading path, the wall thickness of the formed T-shaped tube by ladder loading path is more evenly distributed without wrinkles and fractures and the height of the formed branch tube close to Hmax. At the same time, it is found that under the differential lubrication tube blank, the time of obtaining a suitable loading path is significantly reduced, and the collocation of ladder mode is simpler and more efficient.

Effect of bulge ratio on the deformation behaviour and fracture location during welded steel tube hydroforming process

Abstract: A drawing quality welded steel tube with outer diameter of 57.15 ​mm and thickness of 1.6 ​mm was used in this study. These tubes were hydroformed at bulge ratio (or L/D ratio) of 1, 2 and 3 to achieve different strain paths. It was observed that the tubes after hydroforming fractures in the base metal near the weld for L/D ​= ​1 whereas for L/D ​= ​2, 3 the fracture occurs in the base metal opposite to the weld which was a novel observation. The experimental and simulated strain paths for two extreme L/D ratios of 1, 3 were analysed. It was found that the maximum value of major strain was found at the base metal for all L/D ratios, however, its location and subsequent fracture depends upon L/D ratio. Therefore, to investigate this anomaly, the detailed FE analysis was carried out by varying the ratio of strain hardening exponent between base and weld metal and by introducing the thickness imperfection in the tube. The FE analysis predicts the trade-off between the material inhomogeneity and thickness imperfection leading to fracture at specific location for both L/D. The present study concludes that the relative sensitivity of thickness imperfection versus material inhomogeneity is dictated by the tube bulge ratio.

Investigation on the effect of blank holder gap in the hydroforming of cylindrical cups, made of fiber metal laminate

Abstract: Although fiber metal laminates (FMLs) were invented a few decades ago, large-scale manufacturing, especially the forming process of small and complex-shaped products, has not been matured yet. The forming difficulty comes with the limited strain rate of the fiber layers compared to the metallic layers. As a result, the conventional approaches to form FML parts are not very suitable. Understanding the material behavior during the forming process is critical to find a new technique for relatively intricate and smaller FML parts. The blank holder gap (BHG) is one of the effective parameters to control the material flow in the deep drawing process, but in the case of the FMLs, the situation is completely different due to the laminate constituent. The compression of the fiberglass and thermo-plastique resin to the blank holder force (BHF) is not the same as the metals. The resin acts like a rubber, which decreases the thickness of the laminate and affects the friction between the laminate layers, especially when forming semi-cured laminates, which makes it hard to define an ideal BHF. This paper presents the results of numerical and experimental investigation of the effect of the BHG on the hydromechanical deep drawing (HDD) of a cylindrical cup made with 2/1 Glare sheets. It is found that the optimized BHF and cavity pressure (CP) with a BHG of 1.1 mm, smaller than the laminate’s initial thickness of 1.2 mm, resulted in a good part with a significant depth improvement of 35 mm. Results also exhibited that FML parts manufactured by considering the BHG can enhance its applications and lead to a reduction of time and effort spent in mass production.

Movable Die and Loading Path Design in Tube Hydroforming of Irregular Bellows

Abstract: Manufacturing of irregular bellows with small corner radii and sharp angles is a challenge in tube hydroforming processes. Design of movable dies with an appropriate loading path is an alternative solution to obtain products with required geometrical and dimensional specifications. In this paper, a tube hydroforming process using a novel movable die design is developed to decrease the internal pressure and the maximal thinning ratio in the formed product. Two kinds of feeding types are proposed to make the maximal thinning ratio in the formed bellows as small as possible. A finite element simulation software “DEFORM 3D” is used to analyze the plastic deformation of the tube within the die cavity using the proposed movable die design. Forming windows for sound products using different feeding types are also investigated. Finally, tube hydroforming experiments of irregular bellows are conducted and experimental thickness distributions of the products are compared with the simulation results to validate the analytical modeling with the proposed movable die concept.

Deformation behavior in the hydroforming of overlapping tubular blanks

Abstract: The hydroforming of overlapping blanks (HOB) is a novel method that uses overlapping tubular blanks rather than closed cross-sectional tubes to enhance the forming limit. However, the deformation and instability mechanism of HOB has not been elucidated yet. In this paper, theoretical analysis models were developed for the material flow field, the critical wrinkling stress, and the critical supporting pressure. On the basis of it, the HOB approach was performed experimentally and numerically to validate the proposed models, taking a variable-diameter part as an example. A new self-sealing loading tool made of highly elastic material was developed to realize the sealing. The deformation mechanism in HOB was revealed and the occurrence of material flow along the circumferential direction was demonstrated. In addition, the location and the morphology of potential wrinkles were well predicted. Wrinkling defects were prevented effectively by applying the normal load, which was achieved by a sub-plate covered upon the overlap at the outer layer. The comparison of the required internal pressure and the wall thickness distribution was analyzed in the HOB and the THF processes. It is feasible to reduce the forming pressure and the wall thinning using an overlapping blank.

Influence of internal pressure and axial compressive displacement on the formability of small-diameter ZM21 magnesium alloy tubes in warm tube hydroforming

Abstract: In this study, the influence of internal pressure and axial compressive displacement on the formability of small-diameter ZM21 magnesium alloy tubes in warm tube hydroforming (THF) was examined experimentally and numerically. The deformation behavior of ZM21 tubes, with a 2.0 mm outer diameter and 0.2 mm wall thickness, was evaluated in taper-cavity and cylinder-cavity dies. The simulation code used was the dynamic explicit finite element (FE) method (FEM) code, LS-DYNA 3D. The experiments were conducted at 250 °C. This paper elucidated the deformation characteristics, forming defects and forming limit of ZM21 tubes. Their deformation behavior in the taper-cavity die was affected by the axial compressive direction. Additionally, the occurrence of tube buckling could be inferred by changes of the axial compression force, which were measured by the load cell during the processing. In addition, grain with twin boundaries and refined grain were observed at the bended areas of tapered tubes. The hydroformed samples could have a high strength. Moreover, wrinkles, which are caused under a lower internal pressure condition, were employed to avoid tube fractures during the axial feeding. The tube with wrinkles was expanded by a straightening process after the axial feed. It was found that the process of warm THF of the tubes in the cylinder-cavity die was successful.

Cellular automata modeling of the kinetics of static recrystallization during the post-hydroforming annealing of steel tube

Abstract: A modeling setup based on the cellular automata (CA) method was developed to model the kinetics of static recrystallization (SRX) in hydroformed steel tubes undergoing the annealing process. In addition, the impact of multiaxial deformations on the kinetics of SRX within the hydroformed steel tube was investigated. First, hoop and axial strains developing at the pole of the steel tube during hydroforming were obtained from the digital image correlation measurements. Then, an exact analytical solution was employed to calculate the corresponding hoop and axial stresses at the pole of the bulged tube. Using these biaxial stress–strain curves, the stored energy was calculated for the hydroformed tube specimen. Second, the actual grain topology and crystallographic orientation of grains in the deformed specimen were obtained with the electron backscatter diffraction. Third, the calculated stored energy as well as the microstructural and crystallographic data was incorporated into the CA model as initial conditions to predict the kinetics of SRX in the specimen during annealing. Finally, to assess the accuracy of the CA model, experimental and predicted results were compared in terms of grain topology data including the grain size and aspect ratio distributions, as well as the rate of recrystallization during annealing. A reasonable agreement between the experimental and CA predictions in partial and fully recrystallized specimens was achieved inferring the validity of the developed algorithm and the modeling setup to predict the SRX kinetics during the post-tube hydroforming annealing process.

Manufacturing of bent tubes with non-uniform curvature and cross-section using a novel hydroforming die: experimental, finite element analysis, and optimization

Abstract: Producing non-uniformly curved tubes with sharp corners using the common experimental methods in hydroforming process is difficult. A common approach is to increase the internal pressure as high as possible; which may lead to excessive thinning and fracture on the corners of the tubes. To manufacture this type of tubes, the current study has proposed a new hydroforming die to perform such a process by taking two general steps: initial bulging and forming. The proposed die facilitated with two movable bushes is able to produce bended stainless steel tubes with non-uniform curvature and cross-section. To find the optimum pressure and axial feed profiles, finite element simulations were performed, and the results were validated with experiments. The main advantage of this die is that by moving the bushes inside the die cavity, the friction between die and bushes can be reduced considerably while axial feeding is provided properly, leading to produce a tube with a uniform thickness distribution and maximum achievable corner filling.

Effect of heat treatment temperatures on formability of SS 304 during tube hydroforming process

Abstract: Tube hydroforming is a special process which utilizes a liquid medium to form the tube into required shape. This method has an advantage of attaining uniform pressure all through the tube at any time throughout the process. The forming limit curve (FLC) of SS 304 tubes at different annealed temperatures viz., 150 °C, 200 °C and 250 °C were investigated and compared with as received condition. Effects of annealing temperatures on FLC and bulge height of the hydroformed tube were studied. Numerical simulation of FLCs in tube hydroforming with different L/D ratios and diverse boundary settings were judged to extend wide variety of strain paths. The obtained FLD from the simulations were compared with other two different models to predict the accuracy of the FLD models. Numerical simulations confirmed that the annealing temperatures had an effect on the FLC of hydroformed tube. The forming limit increased with temperature up to 200 °C, and decreased slightly at 250 °C temperature.