Showing papers on "Hydroforming published in 2022"

Surface roughness of AISI 1010 and AISI 304 of PEMFC bipolar plates with microscale hydroformed capillary channels

Abstract: As part of the efforts to produce robust, cost effective bipolar plates, it is necessary to evaluate the forming characteristics of potential materials under consideration. For this work the relationship between strain and deformation induced surface roughness was investigated for channels made from AISI 304 stainless steel and AISI 1010 mild steel that are formed using a hydroforming process. The experiment investigated the effect of channel geometry and hydroforming pressure on surface roughness of the sheet metals under consideration. It is important to state that some functional properties and manufacturing processes of metallic bipolar plates are dependent on the surface roughness of the materials. The results indicate that the final roughness of the formed part is dependent on the initial roughness of the as received sheet. Also, the results show that the surface roughness increases with increasing forming pressure and the resulting increase in strain of the sheet metal due to deformation.

Hydroforming and buckling of toroids with polyhedral sections

Abstract: ABSTRACT 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.

Mechanical Analysis of a Thermo-Hydroforming Fiber-Reinforced Composite Using a Preferred Fiber Orientation Model and Considering Viscoelastic Properties

Abstract: Thermo-hydroforming (THF) process is a single-step process for thermoplastic composite forming, which has a great advantage in terms of the process time and mass production potential as compared to conventional processes. However, with THF processes, wrinkles and deformations are easily generated due to the process characteristics and process parameters. In this study, the matrix material was examined by considering viscoelasticity and changes in formability according to the forming speed. A numerical analysis of the THF composites was performed based on the preferred fiber orientation (PFO) analysis model, which considers the viscoelasticity of the matrix. The deformation change and molding possibility were examined according to various forming speeds. The viscoelastic PFO model showed better analysis efficiency and stability than the primitive PFO model. This analysis will help improve the process of forming thermoplastic composites.

Joining of metal–plastic composite layered tubes by hydroformed threaded coupling

Abstract: Metal–plastic composite tubular structures, which combine the high strength and stiffness of metallic tubes with the lightweight and flexible properties of plastic tubes, exhibit considerable potential to provide lightweight structures with improved performance compared to conventional monolithic metallic and plastic tubular parts. However, the lack of well-confirmed technologies for connecting metal–plastic composite tubes that can ensure good structural stability and strength has proven problematic in actual applications. In this study, an innovative mechanical joining process via a hydroformed threaded coupling was proposed to achieve the successful joining of metal–plastic composite tubes. For the threaded connection, composite tubes were internally threaded to act as a sleeve, and a threaded coupling tube was externally threaded to act as a screw. The threaded composite tubes and coupling tube were rotated to achieve a secure and robust connection. One-step hydroforming technology was developed to fabricate the threaded tubes and couplings using a single die set. The structural performance of the coupled tubular parts was quantitatively evaluated under axial compression and lateral three-point bending tests. The results showed that the proposed joining process has strong potential for successful utilization in connecting metal–plastic composite tubes for structural applications.

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

Abstract: 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.

Buckling of Hydroformed Toroidal Pressure Hulls with Octagonal Cross-Sections

Abstract: This paper is devoted to the hydroforming performances of toroidal pressure hulls with octagonal cross-sections, together with the buckling performances of hydroformed hulls. The octagonal cross-sections of toroidal preforms are inscribed from the circular cross-sections of perfect toroidal shells with a 150 mm major radius, a 75 mm section radius, and a 1.058 mm wall thickness. The nonlinear finite-element method was employed to study the hydroforming and buckling performances under various hydroforming pressures. To verify the numerical findings, three nominally identical toroidal pressure hulls with discrete octagonal cross-sections were tentatively manufactured, internally hydroformed, and externally collapsed. The numerical and experimental data exhibited satisfactory agreement. It is indicated that the hydroforming technique could greatly enhance the loading capacity of toroidal pressure hulls.

Repairing Damaged Screen Pipes with Tube Hydroforming: Experiments and Feasibility Analysis

Abstract: During oil-well production, there are often cracks, breaks, and perforation corrosion on the screen pipe that can significantly deteriorate sand control and pipe strength. To repair damaged screen pipes, we developed a technique originating from the tube hydroforming, and the feasibility of the technique was systematically investigated. First, the elastoplastic mechanics of patch tubes during the hydroforming process was analyzed to investigate the forming mechanism. Second, tensile experiments showed that AISI 321 after cold drawn and solution had good mechanical properties. A numerical simulation model of a hydroforming patch composed of AISI 321 steel was built to investigate the effect of structural parameters such as the length, initial outer diameter, and thickness of a patch tube on hydroforming patch performance. Forming pressure did not significantly change with length, but it decreased with initial outer diameter and increased with thickness. In addition to the simulation, a hydroforming test bench was constructed to experimentally test the patch method. Test results showed that the patch tube could fit closely with the screen base pipe, and residual contact stress could be more than 139.78 kN/m2. Deformation strengthening due to the deformed martensite was conducive to improving the strength of the patch tube after hydroforming. The combination of the simulation and experiment indicates that the application of hydroforming patch technology can effectively repair damaged screen pipes.

Optimization of process parameters during hydroforming of tank bottom using NSGA-III algorithm

Abstract: The hydroforming technology can realize overall forming of large storage tank’s bottom, but the quality is affected by many technological parameters. In view of wrinkling and cracking defects of integral storage tank’s bottom in hydroforming, a multi-objective optimization model is established for process parameters including pre-expansion pressure, hydraulic pressure, blank holder force, and fillet radius of blank holder. Based on finite element simulation, the surrogate model between process parameters and quality criteria is established using Kriging technique. NSGA-III is used to determine optimal process parameters when storage tank’s bottom reaches targets including minimum wall thickness variations, minimum fracture trend, minimum flange wrinkle, and minimum wrinkle trend. Compared with particle swarm optimization (PSO) algorithm, NSGA-III algorithm is more suitable to solve this optimization problem. The validity of this method and accuracy of the results are verified by simulation experiments.

A New Semi-Analytical Solution for an Arbitrary Hardening Law and Its Application to Tube Hydroforming

Abstract: The present study consists of two parts. The first part supplies an exact semi-analytical solution for a general model of rigid plastic strain hardening material at large strains. The second part applies this solution to tube hydroforming design. The solution provides stress and velocity fields in a hollow cylinder subject to simultaneous expansion and elongation/contraction. No restriction is imposed on the hardening law. A numerical method is only required to evaluate ordinary integrals. The solution is facilitated using Lagrangian coordinates. The second part of the paper is regarded as an alternative to the finite element design of tube hydroforming processes, restricted to rather simple final shapes. An advantage of this approach is that the hardening law is not required for calculating many process parameters. Therefore, the corresponding design is universally valid for all strain hardening materials if these parameters are of concern. In particular, the prediction of fracture initiation at the outer surface is independent of the hardening law for widely used ductile fracture criteria. The inner pressure is the only essential process parameter whose value is controlled by the hardening law.

Stress–Strain Analysis for Tube Hydroforming

Abstract: AbstractThe stress–strain states and yield locus during hydroforming are comprehensively illustrated. Particularly, the stress–strain states of curved tubes and Y-shaped tubes are discussed. The stress locus of tube hydroforming is presented. At last, the stress-state of corner zone and the splitting mechanism are discussed.

Investigation of hydroforming process loading paths based on experimental and improvement based on Sobol sensitivity analysis

Abstract: در این مقاله، با استفاده از روش تحلیل حساسیت سوبول که مبتنی بر واریانس است، به بررسی 11 فاکتور تأثیرگذار بر روی بهینه‌سازی مسیر بارگذاری فرایند هیدروفرمینگ پرداخته شده است. سپس امکان‌سنجی و صحت‌سنجی نتایج با روش‌های دیگر بهینه‌سازی مانند اجزای محدود و همچنین روش تجربی گزارش شده است. فاکتورهای ورودی شامل، فشار انبساط، فشار نهایی، زمان تسلیم، زمان انتهای انبساط، جابه‌جایی میانی سنبه محوری، جابه‌جایی نهایی سنبه محوری، زمان جابه‌جایی میانی سنبه محوری، موقعیت اولیه سنبه متقابل، موقعیت نهایی سنبه متقابل، زمان شروع حرکت سنبه متقابل و زمان توقف سنبه متقابل در نظر گرفته شده‌اند، سپس تأثیر هر یک از آن‌ها بر روی ضخامت کمینه و ارتفاع بیشینه در مسیر بارگذاری فرایند هیدروفرمینگ برای تولید اتصالات T به تفضیل مورد بررسی و گزارش قرار داده شده است.اندازه مقادیر بهینه از نظر کمی و کیفی برای هر 11 فاکتور ورودی به‌ دست آمده و براساس مسیرهای بارگذاری محاسبه شده‌ اند.

Plastic wrinkling of thin-walled tubes under axial compression in non-uniform temperature field

Abstract: The main purpose of this paper is to reveal the wrinkling behavior of thin-walled tubes under axial compression in a non-uniform temperature field formed by induction heating on a local position. The distribution of non-uniform temperature fields induced by induction heating and the wrinkling behavior of tubes under axial compression were studied by combining experiments and simulations. Moreover, the thickness and hardness distribution of the wrinkled tube were analyzed. The results show that the maximum temperature difference along axial direction of 5052 aluminum alloy and AZ31B magnesium alloy tubes can reach 129.1°C and 134.7°C in experiments, respectively. In the non-uniform temperature field with a maximum temperature of 250°C, axisymmetric wrinkles can be formed under axial compression on the tubes. With the increase of axial compression, the wrinkle width gradually decreases and its height gradually increases. The contour shape of wrinkles can be fitted accurately with GaussAmp function. There is an obvious thickening phenomenon on the wrinkles and the thickest point is located on the wrinkle top, where the thickness gradually increases with increasing the axial compression. In addition, the microhardness at the wrinkles is lower than that of the original tubes. It decreases with the increase in axial compression. The maximum reduction of microhardness of 5052 aluminum alloy and AZ31B magnesium alloy tubes at the wrinkles are 41.6% and 17%, respectively. This study not only can provide tube blank with useful wrinkles for hydroforming, but also can provide experimental data for establishing buckling theory of inhomogeneous tube shells.

Evaluation of Circumferential Mechanical Properties of Tubular Material by Flaring Test

Abstract: 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.

Upset bulging as a preforming operation for hot metal gas forming of 22MnB5 tubes

Abstract: Abstract Hot Metal Gas Forming (HMGF) is a coupled process of gas forming and quenching of tubes. This process allows to obtain complex and accurate geometry due to the elimination of springback and high mechanical properties due to the formation of martensite, as a result, the weight of the parts can be reduced. HMGF is widely used in the aerospace and automotive industries to make critical parts from high hardenability steels such as 22MnB5. A typical hot stamped component has 1000 MPa yield stress and 1500 MPa ultimate tensile strength. The main challenge of HMGF process is a significant material thinning and cracking due to the biaxial tension stress state. The paper proposes a preforming method for increasing the forming limits of HMGF by the cold upset bulging of tubes by means of the additional volume of material in the deformation zone. This method allows to obtain one or several waves in the cross section of the tube, which helps to increase the minimum workpiece wall thickness after the forming process by more than 40% and to reduce a probability of the crack formation.

Analysis and experimental study of patch tube mechanical properties based on screen pipe hydroforming patch technology

Abstract: Hydroforming patch technology for damaged screen pipes is designed based on tube hydroforming technology, and the methods for determining the forming pressure range and forming defects are selected according to the forming process. The hydroforming patch model for screen pipes is established according to the technical demand parameters for screen pipe repair. From the mechanical properties of the material and digital–analog comparison analysis of the material formability, it is found that the determiners for formability (such as forming pressure, thinning rate, and springback) of 321 stainless steel (SS321) are better than those of 304L stainless steel (SS304L), and the patch tube materials meeting the technical requirements were selected. A test bench for the formability of patch tubes was built to verify the forming pressure of patch tubes with different thicknesses and the distribution of wall thickness after forming. The results show that the hydroforming patch technology is feasible and can realize the firm and close fit between the patch tube and screen pipe; moreover, SS321 can meet the material requirements of the patch tube.

Springback inhibition of Ti-6Al-4V sheet with impact hydroforming at room temperature

Abstract: Abstract Springback is a tough issue in sheet forming, and always leads to dimensional inaccuracy of formed parts. Titanium alloy selected as desired light-weight alloy has been playing significant roles in aerospace industry because of its good comprehensive performance. Whereas, titanium alloy components manufactured always exhibit severe springback at room temperature, which greatly restrict their application. To explore the possibility of reducing springback, rectangular lath-shaped parts with Ti-6Al-4V alloy sheet were fabricated by impact hydroforming (IHF) with self-designed equipment. Consequently, much lower springback is obtained using IHF with high strain rate than that formed by conventional stretch-bending with low strain rate. Great efforts are paid to clarify the mechanism of springback restriction under IHF. Different from traditional forming methods, more complex and high-speed interaction behavior between liquid and Ti-6Al-4V alloy sheet occurs. It considerably increases the difficulty for analyzing the deformation process of sheet under IHF. Thus, a novel solid-liquid coupling numerical simulation technology for IHF was developed. To validate the simulation accuracy, experiments with different forming processes and parameters were performed. Given the combined analysis of experimental and simulation results, it is found that distinctive forming paths are introduced between stretch-bending and IHF. Specifically, the preferred deformation region of sheet transfers from middle region for conventional stretch-bending to end regions under IHF, which mainly attributes to the unique loading behavior of liquid at high strain rate.

The behavior and forming performance of vapor hydroforming process of thin aluminum sheets: Numerical and experimental analysis

Abstract: This paper presents a study on the formability prediction, thickness variation, the influence of the gradient temperature, and prediction damage and failure behavior of aluminum sheets in a hydroforming vapor process through experimental and numerical investigations. A vapor hydroforming process that takes advantage of the coupling between thermal and mechanical loads applied to sheet metal is introduced. Uniaxial tensile tests and an optimization program developed in Matlab and based on the inverse method were conducted for identifying the coefficients of the Johnson-Cook law at room and at different temperatures. In parallel, a finite element model of the hydroforming vapor process was developed using ABAQUS/Explicit to reproduce the behavior of the aluminum sheet, where the behavior of the coupled thermo viscoelastic material and to the damage prediction of the plate being tested is analyzed using Johnson-Cook model. The results confirm the feasibility of the forming process. The variation of sheet thickness, the thinning mode of the tested sheet, and the effects of the hydroforming temperature are studied. A good agreement was achieved between experimental data and numerical results.

Wall thickness control in multi-stage hydroforming of multiwave seal ring with small diameter

Abstract: Thinning rate is a crucial factor in forming quality of the thin-walled seal ring with complex features. To control the excessive thinning by altering the stress state during the material deformation, a new multi-stage three-dimensional (3D) hydroforming technology was proposed in this work. Based on the characteristics of the seal ring and the used superalloy strip, a multi-stage internal pressure forming process was established through finite element analysis (FEA) and forming experiment verification. In addition, the distribution of wall thickness in every stage was discussed. And the influence of the width of deformation zone and the pressure loading path in the cavity on the wall thickness of the part in each step was studied. Finally, the optimal forming parameters of each step that can achieve a stable state of metal flow were obtained. The experimental results demonstrated that the developed 3D hydroforming technology can accurately control the material flow in the multi-stage forming of the multi-wave seal ring with small-diameter and ultrathin wall thickness. For the optimized parameter combination, the blank dimensions of deformation zone are 8 mm in the first step and 18 mm in the second step, while the pre-bulging pressure is 9 ~ 12 MPa and the maximum pressure is 100 MPa in the two steps.

A Novel Hydroforming Process by Combining Internal and External Pressures for High-Strength Steel Wheel Rims

Abstract: As one of the key safety components in motor vehicles, the steel wheel rim is commonly fabricated with the roll forming process. However, due to the varied cross-sections of the rim and the low formability of high-strength steel, it is difficult to produce thin-wall and defect-free wheel rims to realize the purpose of light weight. To solve these problems, a novel hydroforming process by combining internal and external pressures (HIEP) was proposed to produce thin-wall wheel rims in the current study. The designed initial tube with diameter between the maximum and minimum diameter of the wheel rim ensures dispersed deformation and effectively avoids local excessive thinning. During HIEP, a hydroforming process was performed with two successive stages: the external pressure and internal pressure stages. Theoretical analysis and finite element method (FEM) were jointly used to investigate the effect of process parameters on the wrinkling and thinning. With the optimized parameters for internal and external pressure, the wrinkling of wheel rims is prevented under compressive state during the external pressure forming stage. Additionally, HIEP was experimentally carried out with high-strength steel rims of 650 MPa ultimate tensile strength (UTS). Finally, wheel rims with weight reduction of 13% were produced successfully, which shows a uniform thickness distribution with a local maximum thinning ratio of 11.4%.

Optimization of Load Values in Pipe Hydroforming Process Using A Fuzzy Load Control Algorithm

Abstract: One of the most advanced methods of metal shaping techniques is hydroforming, which uses fluid at extreme pressure to deform metal sheets that cannot be fabricated by conventional approaches. This method is perfect for the production of lightweight, seamless, continuous, mesh-shaped, high-quality, and important high-strength automotive and aircraft components. When it comes to pipe hydroforming, the ductility of the metal pipe has a direct impact on the forming load route. (Internal deformation pressure and axial feeding). This research focuses on the impact of operational circumstances. (i.e., the impact of ultimate longitudinal feeding and forming pressure) on the whole procedure and keeps the other factors fixed. The control algorithms were designed to control longitudinal feeding and pressure over the shaping process modeling. Most of the pipe hydroforming paths are created during the multi-stage procedure for loading. Hence the deformation limit strains obtained in the middle of the deformation procedure depend on the route. The present work optimizes the loading path angles in the pipe deformation procedure using an intelligent algorithm for fuzzy logic control. This prevents the tube from breaking or rupturing during the forming process due to high strains. The mentioned control algorithm and fuzzy adaptive neural system (ANSYS) were used to simulate the hydroforming procedure.