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Bipolar plates are one of the most important components of proton exchange membrane fuel cells. With the miniaturization of bipolar plate flow channel sizes and the increasing demand for precision, springback has become a key focus of research in the bipolar plate forming process. In this paper, the hydroforming process for 316L stainless steel bipolar plates was studied, and an FEM model was built to examine the stress and strain at various locations on the longitudinal section of the plate. Modeling accuracy was validated by the comparison of experimental profile and thickness distribution. The effects of forming pressure and grain size on springback behavior are discussed. The results show that with increasing forming pressure, the springback value decreases initially, followed by an increase, but then again decreases. When the forming pressure is 80 MPa–100 MPa, the deformation of the lower element of the upper rounded corner is not uniform with more elastic regions, and the springback is positively correlated with forming pressure. The springback distribution pattern on the cross-section of the bipolar plate changes from a normal distribution to a distribution of "M" shape with increased pressure. The larger the grain size, the lower the yield strength elastic proportion, resulting in a decrease in springback of the sheet. The maximum amount of springback of the bipolar plate is 3.1 μm when the grain size is 60.7 μm. The research results provide a reference for improving the forming quality of metal bipolar plates with different flow channel shapes. [ABSTRACT FROM AUTHOR]

The design of the loading path is one of the important research contents of the tube hydroforming process. Optimization of loading paths using optimization algorithms has received attention due to the inefficiency of only finite element optimization. In this paper, the hydroforming process of 5A02 aluminum alloy variable diameter tube was as the research object. Fuzzy control was used to optimize the loading path, and the fuzzy rule base was established based on FEM. The minimum wall thickness and wall thickness reduction rate were determined as input membership functions, and the axial feeds variable value of the next step was used as output membership functions. The results show that the optimized loading path greatly improves the uniformity of wall thickness and the forming effect compared with the linear loading path. The round corner lamination rate of the tube is 91.2% under the fuzzy control optimized loading path, which was increased by 47.1% and 22.6% compared with linear loading Path 1 and Path 2, respectively. Based on the optimized loading path in the experiment, the minimum wall thickness of the variable diameter tube was 1.32 mm and the maximum thinning rate was 12.4%. The experimental results were consistent with the simulation results, which verified the accuracy of fuzzy control. The research results provide a reference for improving the forming quality of thin-walled tubes and plates. [ABSTRACT FROM AUTHOR]

Hydroforming is a modern metal-forming process prominently used in the shipbuilding, aerospace, and automotive industries for forming lightweight, complex-shaped geometries due to their inherent process benefits. But this process faces challenges such as limited material selection, high tooling costs, and complex process control for obtaining a defect-free part with uniform thickness. Researchers are constantly innovating and advancing hydroforming technologies to overcome these limitations. This work reviews emerging tube and sheet hydroforming technologies, considering parametric effects and design considerations, particularly for micro-domain applications. Further, a wider acceptance of the hydroforming process in different industries is explored by discussing the studies that tried to improve the efficiency and quality of the hydroforming process. This study observed that better formability could be achieved in hydroforming with appropriate intermediate heat treatment, proper lubrication, the correct design of loading paths, and temperature distribution. In tube hydroforming, wrinkles, necking, and cracking observed to be largely reduced by properly selecting the internal pressure and feeding. The precise protrusion height and uniform thickness at different joint cross-sections in tube forming are found to be significantly influenced by the strain-hardening exponent, loading path, and friction coefficient. Electrohydraulic forming is found being increasingly used due to its higher productivity and lower product cost. However, further research is required to achieve complex sheet geometries with sharp corners. This research emphasizes that advanced research, artificial intelligence integration, and the exploration of alternative materials can improve the performance of the hydroforming process. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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

Abstract Hydroforming is a modern metal-forming process prominently used in the shipbuilding, aerospace, and automotive industries for forming lightweight, complex-shaped geometries due to their inherent process benefits. But this process faces challenges such as limited material selection, high tooling costs, and complex process control for obtaining a defect-free part with uniform thickness. Researchers are constantly innovating and advancing hydroforming technologies to overcome these limitations. This work reviews emerging tube and sheet hydroforming technologies, considering parametric effects and design considerations, particularly for micro-domain applications. Further, a wider acceptance of the hydroforming process in different industries is explored by discussing the studies that tried to improve the efficiency and quality of the hydroforming process. This study observed that better formability could be achieved in hydroforming with appropriate intermediate heat treatment, proper lubrication, the correct design of loading paths, and temperature distribution. In tube hydroforming, wrinkles, necking, and cracking observed to be largely reduced by properly selecting the internal pressure and feeding. The precise protrusion height and uniform thickness at different joint cross-sections in tube forming are found to be significantly influenced by the strain-hardening exponent, loading path, and friction coefficient. Electrohydraulic forming is found being increasingly used due to its higher productivity and lower product cost. However, further research is required to achieve complex sheet geometries with sharp corners. This research emphasizes that advanced research, artificial intelligence integration, and the exploration of alternative materials can improve the performance of the hydroforming process.

Finite element analysis software was employed to examine the plate-type hydroforming hydraulic press, focusing on the stress and deformation of the press under conditions of pre-tightening and full-tonnage operation. This study was conducted to ascertain that the press's strength and stiffness adhere to the design requirements throughout the filling process. The findings reveal that the stress exerted on the upper beam of the hydroforming hydraulic press remains within permissible limits under full-load conditions, and the stiffness aligns with the design specifications. The methodology and outcomes of this research are poised to offer valuable insights and guidance for the design of the combined body of the hydroforming hydraulic press. [ABSTRACT FROM AUTHOR]

Metal-polymer hybrid (MPH) injection molding is an innovative manufacturing process with vast potential in today industries. This article reviews MPH, covering its introduction, applications, significance, and associated challenges. The introduction outlines MPH unique principles distinguishing it from traditional injection molding techniques. Next, the MPH potential in the automotive industry is explored, highlighting its ability to merge high-strength metal components with polymer matrix, resulting in improved structural integrity, decreased weight, reduced gas emissions, and promising cost savings. In addition, the process allows the production of complicated shapes, providing a large design window. Furthermore, its production sustainability potential makes it an interesting alternative for eco-friendly goals. Nevertheless, several technical challenges face MPH process, which have been observed in previous research, such as process parameters, thermal expansion, shrinkage behavior, interfacial adhesion, and manufacturing defects through the molding operation are mentioned thoroughly. Furthermore, considering all the relevant factors, the future scope of study and development has also been evaluated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, the use of response surface methodology (RSM) to design and optimize the primary process parameters for the hydroforming of bi-layered Y-shaped tubes with a new parallel backward punch is reported for the first time. The effects of the main factors such as shaping pressure, left and right axial feed, backward punch displacement, and friction coefficient of the loading path on the forming performance are analyzed, and the ultimate fillet radius and the maximum contact area between the top of the branch pipe and the backward punch combined with the maximum thinning rate of the inner and outer tubes are introduced as the experimental evaluation indexes for the first time, and the effective evaluation indexes, perturbation diagrams, optimized evaluation criteria, and the interaction effects of different experimental factors based on the principal influencing factors are analyzed and optimized to screen the process parameters of the optimal loading path. Finally, the simulation results under the optimal loading path are compared with the experimental data, revealing an error within 5%. This indicates that the proposed loading path optimization method for hydroforming of bi-layered Y-shaped tubes exhibits high accuracy and excellent feasibility. [ABSTRACT FROM AUTHOR]

In this paper, a prediction model for the pressure-axial feed loading path in the hydroforming process of a bi-layered Y-shaped tube is developed. The plastic deformation behavior of the bi-layered Y-shaped tube in the hydroforming process is investigated by categorizing the entire process into four stages: yielding, preforming, plastic forming, and shaping. By conducting stress–strain analysis on the central unit of the bi-layered Y-shaped tube branch area and incorporating the Von-Mises yield criterion, the Levy–Mises flow rule and the principle of volume invariance, rational ranges for internal pressure and axial feed at various stages of the bi-layered Y-shaped tube hydroforming process are identified. Therefore, a predictive model for the loading path of the bi-layered Y-shaped tube hydroforming process, controlled by internal pressure and axial feed under various strain conditions, is developed. The effectiveness of the prediction model was validated through finite element simulations and experimental methods. This predictive model can be used to guide the setup of loading paths for bi-layered Y-shaped tubes and other similar inclined tee tubes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, we investigate into the simulation of sheet metal hydroforming for crafting the cap of the axle-hub of a tip trailer within our manufacturing facility. This cap serves a crucial role in safeguarding wheel bearings from the detrimental effects of dust, sand, and dirt. The motivation for this work arises from the challenges encountered during the fixation of a conventional dust cap, which often falls off when subjected to pressure or threading, particularly when the tractor is in motion. The innovative approach pursued in this research involves the utilization of lightweight aluminum sheet metal for cap production, owing to its facile formability. The cap design incorporates four evenly distributed holes around its circumference and secures to the flange using screws. Prior to the manufacturing phase, a simulation of the cap-forming process was conducted using ANSYS Model 15, a computer-aided engineering program. The necessary models were crafted in CATIA, a computer-aided design program, streamlining the entire process to enhance efficiency, reduce costs, and minimize manpower requirements. The simulation encompassed three different thicknesses (1 mm, 2 mm, and 3 mm) for two distinct aluminum alloys, namely 1100 and 5652. The objective was to discern the optimal alloy for the forming process. Essential mechanical properties, including ultimate tensile strength, modulus of elasticity, and yield stress, were input into the ANSYS program to accurately reflect the materials' behavior during forming. The outcomes of our investigation revealed that aluminum alloy 5652 outperformed 1100 in terms of formability. The former exhibited a forming pressure of 300.2 MPa, while the latter required 298.3 MPa for the same forming depth (40 mm) across all three thickness variations. Additionally, the study demonstrated that 5652 is not only more efficient but also safer and more resilient than 1100.

Copyright of Tikrit Journal of Engineering Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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. [ABSTRACT FROM AUTHOR]

Coated superconducting radio-frequency (SRF) cavities are planned to be implemented in the Future Circular Collider (FCC) at the European Organization for Nuclear Research (CERN). The interest in industrialized and high-performance processes for fabrication of the corresponding copper substrates has thus risen. Tubular hydroforming is a well-known industrial process, but has not been thoroughly applied for ultra-pure oxygen-free electronic copper (Cu-OFE) thick products. To provide a feasibility analysis for the optimized fabrication process of copper substrate seamless cavities, a Forming Limit Diagram (FLD) of the material of interest was studied. In this paper, the methodology, test results and initial benchmark of the material model is presented, for 4 mm and 2 mm thick sheets.

Bipolar plates are one of the most important components of proton exchange membrane fuel cells. With the miniaturization of bipolar plate flow channel sizes and the increasing demand for precision, springback has become a key focus of research in the bipolar plate forming process. In this paper, the hydroforming process for 316L stainless steel bipolar plates was studied, and an FEM model was built to examine the stress and strain at various locations on the longitudinal section of the plate. Modeling accuracy was validated by the comparison of experimental profile and thickness distribution. The effects of forming pressure and grain size on springback behavior are discussed. The results show that with increasing forming pressure, the springback value decreases initially, followed by an increase, but then again decreases. When the forming pressure is 80 MPa–100 MPa, the deformation of the lower element of the upper rounded corner is not uniform with more elastic regions, and the springback is positively correlated with forming pressure. The springback distribution pattern on the cross-section of the bipolar plate changes from a normal distribution to a distribution of “M” shape with increased pressure. The larger the grain size, the lower the yield strength elastic proportion, resulting in a decrease in springback of the sheet. The maximum amount of springback of the bipolar plate is 3.1 μm when the grain size is 60.7 μm. The research results provide a reference for improving the forming quality of metal bipolar plates with different flow channel shapes.

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

2219 aluminum alloy thin-walled tubes were fabricated by multi-pass spinning process, and then heat treatments were employed to optimize the mechanical properties of the spun tubes. It is shown that severe deformation during the spinning leads to the formation of large number of nanoscale subgrains, which causes the decrease of work hardening rate, ultimate tensile strength, and fracture strain. The solid solution at 530℃/30 min results in the full recrystallization and leads to the disappearance of the nanoscale subgrains. Besides, the micron scale precipitates in the as-spun tubes are refined to be nanoscale via the further aging process conducted at 175℃/18 h. It is why the ultimate strength of the tubes is enhanced from 245 to 435 MPa. By using of the spun tubes, 2219 aluminum alloy bellows with four circumferential waves were successfully formed by multi-step single wave hydroforming process. [ABSTRACT FROM AUTHOR]

In the hydroforming process, the wall thickness of metal bellows decreases, resulting in a non-uniform phenomenon in which the thickness of bellows decreases with increasing diameter. To describe this phenomenon, the index thinning method was introduced in this paper. Finite element (FE) models were utilized to analyze the non-uniform wall thickness of thin-walled bellows, and the numerical stiffness was calculated through numerical simulation with ABAQUS. The corresponding m (thinning index) value of the bellows model was then determined by comparing the numerical stiffness with the experimental stiffness. For the model with m set to 0.8, the numerical stiffness was found to be 1007.19 N/mm, while the average experimental stiffness was measured as 1000.49 N/mm, with the minimum relative error between the two being 0.67%. Then, the meridional and circumferential stresses of the bellows model were obtained when m was 0.8, and the accuracy of stress results calculated by the FE method was verified by the stress measured in tests, and it also verified the validity of the proposed method. From the perspective of the development of hydroforming technology, the index thinning method could have guiding significance for practical application. [ABSTRACT FROM AUTHOR]

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

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.

Purpose: A 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/approach: A 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. Findings: The 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/value: A 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. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hydroforming and buckling of toroids with polyhedral sections were examined. The cross section of a polyhedral preform had the form of an irregular octagon with a uniform thickness of 1.1 mm. This octagon was inscribed on the circular section of a target toroid with a rotation radius of 150 mm and a cross-sectional radius of 75 mm. Two nominally identical preforms were fabricated, internally hydroformed, and externally collapsed. The internally and externally applied pressures were recorded, and the geometric shapes and thicknesses were measured before and after the hydroforming process. The nonlinear finite-element method was used to investigate the hydroforming and buckling properties. The experimental results and numerical estimations were compared, and the results indicate that the hydroformed toroid can be employed in underwater vehicles. Jordan's equation can provide a conservative prediction of the ultimate allowable outer pressure of hydroformed toroids when the hydroforming pressure exceeds a certain threshold. [ABSTRACT FROM AUTHOR]

In this study, hydraulic pressure generation and small-scale cylindrical hydromechanical deep-drawing experiments were conducted using a novel die-integrated active high-pressure generation system. The most significant feature is the installation of a hydraulic pressure-generating piston structure inside the die, which enables a high-pressure generation process of 100 MPa or higher inside the die. In addition, by taking advantage of the size effect of a smaller die, a high hydraulic pressure is actively generated using the same equipment as in conventional drawing processes. It was discovered that a piston installed in the die can actively generate a hydraulic pressure of 100 MPa or higher based on the Pascal principle. By downsizing the die, a hydraulic pressure of 100 MPa or higher can be generated using only the power of a small press machine (50 kN). By actively applying high hydraulic pressure counter and radial pressures, small-scale drawability can be significantly improved. Furthermore, the application of the proposed system to single-action presses and progressive dies can enable hydromechanical deep drawing with optimized conditions for each process in a single motion. [ABSTRACT FROM AUTHOR]

In the hydroforming process of a thin-walled tubular component with multiple local bulges, the bulge in the middle position is almost impossible to be formed with a conventional one-step hydroforming process because of the difficult axial feeding. To solve this problem, a novel method is proposed by preforming wrinkles using selective induction heating at different positions of tube blank to aggregate materials in advance for the subsequent hydroforming of tubular component with multiple local bulges. In this paper, the wrinkling behavior of 5052 aluminum alloy tube blank under different conditions and the deformation behavior of the wrinkled tube blank in subsequent hydroforming process of tubular component with three bulges are analyzed. It is shown that the existence of wrinkles is beneficial to increase the ultimate expansion ratio of the tube blank. Moreover, the instability behavior of multiple wrinkles on 5052 aluminum alloy tube blanks under different conditions was investigated by experiments. The process parameters for prefabricating two or three wrinkles, including temperature, spacing between wrinkles, and internal pressure, were determined through a detailed experimental investigation. Finally, the defects including splitting and undercut that occur in the hydroforming of tubular component with three bulges are analyzed, and the thin-walled tubular component with three bulges was hydroformed successfully using a wrinkled tube blank obtained under the process parameters of 250 °C, 4 mm, 5.5 MPa/350 °C, 10 mm, 2 MPa/400 °C, 6 mm, 1.33 MPa. These results provide insights for the manufacturing of tubular component with multiple local bulges from hard-to-form materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the differential lubrication method on the wrinkling and cracking during the hydroforming of the Y-shaped tube was discussed, as well as the effects of the initial position, counterforce, and end angle of the counter punch on the forming of the branch tube were discussed. It is of great significance to the hydroforming of thin-walled 5A02 aluminum alloy Y-shaped tube with a large transition fillet that is asymmetric in both longitudinal and transverse directions. The experiment used a counter punch with 0° and 13.5° end angles and a loading path with stepped pressure feed. MoS2 and PTFE film were chosen as lubricants for the differentiated lubrication method. The experimental results show that the flow rate of material in the bulging zone was effectively improved when MoS2-PTFE was used in this zone of Y-shaped tube, while dry friction was used in other areas, preventing the wrinkling on the main tube. The branch without cracking but with ideal height and good surface quality can be obtained when the counterforce was 13.7 KN, the initial position was 17 mm, and the counter punch end angle was 13.5°. [ABSTRACT FROM AUTHOR]

The isothermal high temperature pneumoforming process to form tubes at constant elevated temperatures by means of internal pressure is investigated. Two materials, a ferritic (X2CrTiNb18) and a martensitic stainless steel (X12Cr13) are used for the investigations. The required material characterization is performed at the temperature and strain rate of the actual process. A new method for quantifying thermal softening via the time-dependent decrease in static yield stress is presented. At a temperature of 1000 °C, the static yield stress decreases by 50% within 100 s for both materials. The numerical models are validated on the basis of the formed geometry and used to study the influence of maximum internal pressure, axial feed, holding time under load and die edge length on the final part geometry. It was observed, that with higher internal pressures and longer holding times smaller corner radii are formed for both materials. In contrast, a superimposed axial feed as well as the effective friction coefficient have a negligible influence on the formed geometry. With an increasing die edge length, smaller radii are formed with the ferritic stainless steel numerically and experimentally. By contrast, for the martensitic stainless steel, larger radii are observed numerically. Experimentally, the limited formability of these tubes weld seam becomes apparent. Based on the findings, process windows depending on the process parameters internal pressure and die edge length were derived. Numerically, forming limit curves of tubular semi-finished products under comparable conditions serve as a failure criterion. Good agreement with experiments was observed. [ABSTRACT FROM AUTHOR]

At present, there are no experimental methods that allow for the complete direction-dependent mechanical characterization of tubes. This considerably limits the parameterization of complex, anisotropic material models. The present study introduces a new approach to overcome these limitations: tube sections are first flattened into a planar geometry; then, samples for uniaxial testing are taken out of the flattened tube section and used for parameter identification. In this paper, special emphasis is placed on the intermediate step of flattening, which is investigated in detail both numerically and experimentally. Flattening by pressing is identified as the most advantageous of several options, and the procedure is optimized by numerical simulations that address springback compensation. Experimental validation is performed on tubes (steel E235) with a diameter of 60 mm and an average wall thickness of 1.524 mm. Tube sections are successfully flattened in a custom-built tool with only small remaining out-of-plane displacements after flattening. The numerically predicted pressing force curves agree very well with the experimental data. [ABSTRACT FROM AUTHOR]

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.

Fiber metal laminates (FMLs) are a super hybrid material that provides the combined advantages of metals and composites and offers significant potential as an ultralight structural material in the aerospace industry. Consequently, there has been increased research attention on FML mass production processes. The recent developments in FML component production and FML sheet preparation are the main topics of this review. First, a general overview of the development history, fabrication process, and properties of FMLs and their production process is presented in this paper. With a focus on combined die forming, such as stamping and hydroforming, which is the most promising method for the mass manufacture of complex curve-shaped FML components, several other forming technologies are also discussed in depth. Afterward, the FMLs' forming limitations and challenges, which have been observed in previous research, are also mentioned thoroughly. The defect and deformation modes that can develop during the forming processes of FMLs are addressed. Furthermore, considering all the relevant factors, the future scope of study and development has also been evaluated. [ABSTRACT FROM AUTHOR]

Today, the use of sheet hydroforming methods in the conventional deep drawing process has significantly improved the formability of the sheet. However, due to the limitations of the sheet hydroforming process, new methods can be used in combination with it, such as ultrasonic vibration–assisted forming. Many of the mechanical effects of ultrasonic vibration in the metal forming process are due to the metallurgical and structural impacts of the material. Hence, to find the cause of the observed cases, one must look at the microstructural interactions of materials. Therefore, the process of St14 sheet hydroforming with the assistance of ultrasonic vibration is investigated microstructurally in this paper. For this purpose, during the hydroforming drawing process, ultrasonic vibration was radially applied to the punch in a hydro-mechanical deep drawing die. Then, the process parameters, including thickness, equivalent strain, grain size, and rotation at a selected point of the cross-section of the sample parts, are compared in four modes of conventional deep drawing (CDD), hydroforming deep drawing (HDD), deep drawing assisted by ultrasonic vibration (UDD), and hydroforming deep drawing assisted by ultrasonic vibration (UHDD). Results showed that the application of ultrasonic vibrations in the sheet hydroforming process led to a significant reduction in thickness strain (as well as equivalent strain) in the wall of the cup, increased grain length, and reduced rotation. This implies that the positive impact of ultrasonic vibrations in the flow of materials is due to the reduction of friction and facilitates the movement of dislocations. [ABSTRACT FROM AUTHOR]

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For the purpose of eliminating the annular welding seams in welding structures with differential thickness, a hydroforming method using a circular 5A06 aluminum alloy plate with a radial differential thickness in coupling with a flexible polyurethane auxiliary plate was proposed to form an integrated semi-ellipsoid shell. The circular 5A06 aluminum alloy plate had a smaller in the middle and a larger thickness in the periphery. In the forming process of such aluminum alloy plates, concentrated deformation and fracture might have occurred in the thin zone. According to the size of the target specimen, the testing plates with two types of thickness ratios were obtained by mechanical processing. Furthermore, the thickness and strain of the drawn specimens with different thickness ratios were analyzed under different hydraulic pressure by means of deep drawing experiments. Compared to the conventional deep drawing, the formability of 5A06 aluminum alloy plates with differential thickness could be effectively improved by hydroforming. The integrated semi-ellipsoid shells with the thickness ratios of 2/3 and 1/2 were obtained under the hydraulic pressure of 10 MPa with maximum thinning ratios of 8.5% and 10.9%, respectively. In a word, the increase in hydraulic pressure could effectively reduce the maximum thinning ratio in the thin zone, and improve the thickness distribution uniformity. [ABSTRACT FROM AUTHOR]

An elliptical die hydraulic bulging test was carried out to explore the forming performance of 2A16 aluminum alloy sheets during hydroforming. By using five groups of elliptical dies with ovality of 1.0, 0.9, 0.8, 0.6, and 0.4, the effects of different pressure rates of 0.02 MPa/s, 0.04 MPa/s, and 0.08 MPa/s on the test results were studied, and different sheets thicknesses of 2 mm and 2.5 mm were also explored, then the equivalent stress and strain values obtained by theoretical calculation were also analyzed. Finally, the complete forming limit diagram (FLD) of the 2A16 aluminum alloy sheet at room temperature was plotted through the elliptical hydraulic bulging test and the uniaxial tensile test under the same test conditions. The results show that as the ellipticity increases, the maximum equivalent stress-strain value of sheets gradually increases; reducing the hydroforming pressure rate or increasing the thickness of the sheet can slightly increase the maximum bulging height of the sheet, but it has no significant impact on the maximum equivalent stress and strain value of this material. There is no noticeable difference in the FLD on the right side, indicating that its FLD is universal for a material.

In the sustainability of ceramic forming this paper will provide a comprehensive review of the way that ceramics have changed over time towards sustainability due to Industry 4.0’s current manufacturing technologies which are improving day by day. Particularly this study focuses on reducing the depletion of resources, energy utilization, and natural pollution by examining how conventional strategies for forming ceramics can be replaced by new ones that emphasize sustainability and form a solution. Basically, this paper highlights a few crucial properties in ceramics including its capacity to resist high temperatures, flexibility, and chemical inactivity, and their significance in several areas like biomedical designing, hardware, aviation, the machinery industry, and many more applications. When the drawbacks of traditional ceramic forming methods were analyzed such as high cost and lengthy processing periods, the study clarifies that there is a need for sustainable alternatives. This study also examines new possibilities such as additive manufacturing (3D printing) and hydroforming, which permit for more accuracy in product shape while utilizing a low amount of materials and energy. Going forward, this research also looks into eco-friendly ceramic materials that make the most of secondary sources or are based on biomass-based added substances and binders. Using examples from real circumstances and information from industry, it demonstrates where sustainable ceramics can be utilized in different divisions like design, space travel, electronics, wellbeing care, or renewable energy sources. By doing so, this paper emphasizes how sustainable ceramic making seems to trigger environmental enhancements as well as keep up resource efficiency and shift towards a circular economy.

Forming process and product quality in hydroforming of sheet metal have been considered to be significantly influenced by numerous technological parameters, and one of those is blank holder pressure. This parameter keeps an important role in not only maintaining stability on rim of workpiece but preventing leakage of high-pressure liquid as well. In this paper, a parametric study was conducted to investigate a relationship between the blank holder pressure and forming pressure during the shaping process. Moreover, effect of the blank holder pressure on product quality was also experimentally scrutinized through thinning and real shapes of different finished products. The researched object was chosen to be a cylindrical cup made of steel DC04 with various thicknesses. The experiments were implemented for two cases of the blank holder pressure during forming process: constant and varied pressures. The results indicate a covariant relationship between the blank holder pressure and forming pressure. Furthermore, it should be noted that the forming pressure can be maintained at higher values in the case of varied blank holder pressure, thereby improving shape quality and thinning rate of the product. The relationship between two types of pressure as well as impact of the blank holder pressure on the bottom radius and the maximum thinning of the product is demonstrated as functions through empirical studies. This study is believed to make contribution to optimizing technological parameters within forming process to manufacture high-quality products. [ABSTRACT FROM AUTHOR]

The pressure rate is a key parameter during sheet hydroforming. To investigate the influence of pressure rate (the increment of pressure per unit time) on the thickness of aluminum alloy cylinder-shaped part flange under the action of thickness normal stress, a finite element model of hydroforming was established. Variations in thickness of the flange of cylinder-shaped parts were simulated at different pressure rates under the same forming parameters, such as friction coefficient, forming pressure, and loading path. For the convenience of the study, the thickness variation range was divided into three intervals, namely, the fast growth area, the slow growth area, and the fluctuation area, when the pressure rate is larger than 1.25 MPa/s. The variation of the thickness of the flange in these three intervals was analyzed and the relation between the pressure rate and the maximum flange thickening rate was obtained for the different intervals. The influence of the pressure rate on the thickness of cylinder-shaped part flange was obtained. Using a quadratic polynomial curve fitting method, a prediction equation for the maximum rate of thickening of cylinder-shaped part flange was established, by which maximum flange thickness can be predicted for different pressure rates. Experimental verification was also carried out. It was found that the experimental results are in good agreement with the simulation results. The prediction equation can provide useful reference and experimental basis for the selection of hydroforming deep drawing process parameters of aluminum alloy cylinder-shaped parts and the trial production of typical parts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]