Amount Of Springback Research Articles

Study on Springback Behavior in Hydroforming of Micro Channels for a Metal Bipolar Plate

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.

Analysis of Thickness Variation in 2219 Aluminum Alloy Ellipsoid Shell with Differential Thickness by Hydroforming

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.

Springback characteristics and influencing laws of four-axis flexible roll bending forming for aluminum alloy.

This study aims to solve the problem of springback control of aluminum alloy components in the rolling process, and the method of combining experiment and simulation is adopted. Firstly, a series of aluminum alloy samples are designed, and the four-axis flexible bending machine is used for precision roll bending. Secondly, the three-dimensional (3D) shape change data of the workpiece before and after roll bending is monitored and recorded in real-time by a high-precision 3D scanner. Meanwhile, aiming at different rolling process parameters of each group (including roll bend speed, feed rate, pre-deformation amount, mold curvature radius, and other factors), advanced finite element software is used to carry out detailed simulation and calculations. In addition, the coincidence is compared and analyzed between the actual experiment results and the simulation prediction. The stress-strain distribution and springback evolution of aluminum alloy during roll bending are described accurately. The experimental and simulation results show that the springback rate of aluminum alloy fluctuates in the range of 5% to 15% after four-axis flexible roll bending, and the specific springback value is influenced by various process parameters. For example, under the premise of keeping other conditions unchanged, when the roll bending speed is increased from 30mm/s to 60mm/s, the springback rate shows an upward trend of about 3%. By increasing the feed rate by 20%, an average decrease of about 7% in springback quantity is observed. It can be seen that the increase in roll bending speed can aggravate the springback phenomenon, and the appropriate increase in feed rate can play a certain role in restraining the springback. Further analysis shows that the choice of the mold curvature radius and pre-deformation amount also has a decisive influence on the springback characteristics. There is a nonlinear relationship between the two parameters and the amount of springback. Changing these two parameters in a specific range can effectively regulate the springback effect.

Experimental Study on Springback Properties of 6061 Aluminum in V-Bending

Sheet metal bending is one of the most commonly applied methods among sheet metal forming operations. In this study, the springback behavior of aluminum alloys of different thicknesses was examined by performing v-bending processes at different die angles and widths. The experiments were carried out on 1 and 1.5 mm thick plates at die angles of 140°, 150° and 160° and three different die widths: 10 mm, 16 mm and 20 mm. In this experimental study, it was observed that springback decreased as the die width increased. As the die angle increased, springback values also increased. It has been observed that sheet thickness has little effect on springback. As the sheet thickness increased, the amount of springback decreased. The lowest springback value of 0.1° was obtained in the 1.5 mm thick specimen with a die width of 10 mm and a die angle of 140°. The highest spring-go value of -2.7° was obtained in the 1 mm thick specimen with a die width of 20 mm and a die angle of 140°. As a result of the variance (ANOVA) analysis, it was seen that the die width had a more significant effect (78.42%) on springback than the die angle. The effect of die angle on springback is 10.73%. As a result of the experiments and statistical analysis, it was seen that the parameter that most affects springback is die width.

Al-Cu Composite’s Springback in Micro Deep Drawing

With the recent technological trend of miniaturization in manufacturing industries, the rise of micro forming operations such as micro deep drawing (MDD) is inevitable. On the other hand, the need of more advanced materials is essential to accommodate various applications. However, a major problem are size effects that make micro scale operations challenging. One of the most important behaviors affected by size effects is the springback phenomenon, which is the tendency of a deformed material to go back to its original shape. Springback can affect dimensional accuracy, which is very important in micro products. Thus, this paper investigated the springback behavior of Al-Cu composite in MDD operations. Micro cups were fabricated from blank sheet specimens using an MDD apparatus with variation of annealing holding time. The springback values were measured and compared to each other. The results showed that different grain sizes lead to variation in the amount of springback. However, unlike in single-element materials, the amount of springback in Al-Cu composite is not only related to the thickness to grain size (t/d) ratio. Another factor, i.e., the existence of an interfacial region between layers, alters the mechanical behavior of the composite.

Revolutionary auxetic intravascular medical stents for angioplasty applications

Due to the significant mortality rate associated with atherosclerosis-induced cardiovascular disease, the utilization of advanced intravascular stents with superior mechanical performance is imperative for the restoration of obstructed arteries. This study proposes novel auxetic medical stents that aim to enhance critical parameters of biomedical stents. This includes load-bearing capacity, expanded opening percentage, and reduced recoil percentage. On this matter, the missing rib auxetic unit cell has been considered and geometrically modified to achieve these objectives. Two-dimensional (2D) metamaterials were fabricated through additive manufacturing technique and subjected to experimental testing. Then, finite element analysis (FEA) was employed to gain comprehensive insights into the mechanical behaviour of the proposed medical stents. Remarkably, an excellent correlation was observed between the FEA and experimental results, validating the high precision of the analysis. The findings reveal that the stents classified as “E-category” exhibit the highest final opening percentage while concurrently demonstrating the lowest recoil percentage. The base stent exhibited a relatively high recoil percentage of 15.56%, indicating a significant amount of recoil or spring-back after deformation. In contrast, the modified “E-category” stent displayed a substantially lower recoil percentage of 1.62%. This notable reduction in recoil percentage indicates that the modifications made to the rib-unit cells had a significant and beneficial effect on the stent's recoil behaviour and minimizing potential damage to arterial tissue during stent deployment (angioplasty) and balloon pressure. The modified design likely enhances the stent's ability to maintain its shape and resist recoil, making it more effective and reliable in its intended application. Additionally, more aspects of biomedical stents such as foreshortening, and dog-boning of the modified missing rib stents were meticulously examined through FEA.

Artificial intelligence-based springback compensation of EV motor component

The hairpin is a crucial component of the drive motor of an electric vehicle, consisting of a copper coil and a very thin enamel layer. It is manufactured using successive forming processes due to its complex shape. After the forming processes, springback is inevitably observed, which causes critical issues in fabricating the drive motor. Compensating springback is a time and cost-inefficient process, and a new process is required for a cost-efficient forming process. In this research, an intelligent forming process has been proposed for springback compensation of hairpin forming by applying Artificial Intelligence to the forming process. The key parameters for the AI are the dimensions of the copper coil, including bobbin information, material property variance in a coil bobbin, punch stroke, and amount of springback. As a preliminary design, the data set has been constructed through the finite element simulation. For the springback compensation, punch stroke was optimized with the trained AI and optimization algorithm. The results show that AI could play a key role in solving the manufacturing issue.

Atomistic simulation of the effect of porosity on shock response of nanoporous gold.

Nanoporous metals (NPMs) have a three-dimensional bicontinuous porous network structure that consists of interconnected nanoligaments. NPMs have the potential to effectively attenuate and dissipate the effects of impacts and blasts. Previous studies do not provide data on the possible effects of porosity at the nanoscale. Molecular dynamics simulations based on the embedded-atom method potential were performed using the open-source code LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). Nanoporous gold (NPG) absorbs shock energy first through the elastic-plastic deformation of ligaments and then through the collapse of ligaments. After the shock loading is relaxed, NPG with lower porosity has a higher amount of springback, and new voids tend to nucleate and grow at collapsed ligaments where the packing is looser. NPG with higher porosity has a better ability to resist the propagation of a shock wave and is subjected to a smaller stress effect.

Effect of Processing Technology on Mechanical Properties of HRB500 High-Strength Steel Bar Threading

The processing quality of steel bar thread has a large influence on its performance. Using the traditional thread processing technology, it is difficult to meet the requirements of steel bar thread processing with large diameter and high strength. A technical process for HRB500 high-strength steel bar thread processing, including face milling, rib stripping, chamfering, necking formation, and thread rolling, was proposed. The influences of cutting parameters on the cutting force of steel bar surface in face milling were analyzed by the finite element method. For the necking formation process, the effect of springback amount on necking formation was studied. The main parameters in rolling formation were analyzed and calculated, including extrusion pressure, rolling speed, and rolling feed. Experiments for uniaxial tensile of the processed high-strength steel bar threads were carried out. The results showed that cutting depth has the largest influence on the cutting force; the second is feed rate. The effect of the spindle speed was lowest during the face milling. After the necking formation process, the values of the maximum springback amount along the X, Y, and Z directions were 0.05 mm, 0.06 mm, and 0.98 mm, respectively. The finished thread met the precision and quality requirements of a grade I joint. This study provides a high-quality processing technology for large-diameter and high-strength steel bar threads.

Formation of ultrafine grain and mechanical properties in commercial pure titanium subjected to heavy-reduction thermomechanical processing around β transus temperature

The purpose of this study was to investigate the flow stress behavior and formation of ultrafine grains (UFGs) by focusing on the effects of strain-induced dynamic transformation (SIDT) and dynamic recrystallization (DRX) under hot forming near the β transus temperature. Heavy-reduction thermomechanical controlled processing (TMCP) of commercial pure (CP) titanium was performed at deformation temperatures ranging from 700 to 1000 °C, a strain rate of 1 s−1, and a 70% height reduction, followed by water cooling immediately after compression. The flow stress at 0.2 strain decreased significantly from 96 to 25 MPa when the deformation temperature increased from 800 to 900 °C. Equiaxed UFGs with a grain size of 2–4 μm formed in this temperature range. The primary mechanisms of grain refinement in the CP titanium under heavy-reduction TMCP were DRX occurring at 800 °C and a combination of DRX and SIDT (β → α) at 900 °C. Of the 700, 900, and 1000 °C TMCP-treated specimens subjected to a 90° V-bending test, the yield force of the 700 °C TMCP-treated specimen was the highest. When the TMCP temperature was increased from 900 to 1000 °C, the yield force decreased significantly, whereas the springback amount increased. The α phase grain refinement achieved by the TMCP at 700 °C increased the force, and the retained β phases within the 1000 °C TMCP-treated specimen increased the springback amount.

On the Springback and Load in Three-Point Air Bending of the AW-2024 Aluminium Alloy Sheet with AW-1050A Aluminium Cladding.

This article presents the results of an analysis of the bending load characteristics and the springback phenomenon occurring during three-point bending of 1.0 and 2.0 mm thick AW-2024 aluminium alloy sheets with rolled AW-1050A cladding. A new proprietary equation was proposed for determining the bending angle as a function of deflection, which takes into account the influence of the tool radius and the sheet thickness. The experimentally determined springback and bending load characteristics were compared with the results of numerical modelling using different models: Model I, a 2D model for a plane deformation state, disregarding the material properties of the clad layers; Model II, a 2D model for a plane deformation state, taking into account the material properties of the cladding layers; Model III, a 3D shell model with the Huber-von Mises isotropic plasticity condition; Model IV, a 3D shell model with the Hill anisotropic plasticity condition; and Model V, a 3D shell model with the Barlat anisotropic plasticity condition. The effectiveness of these five tested FEM models in predicting the bending load and springback characteristics was demonstrated. Model II was the most effective in predicting bending load, while Model III was the most effective in predicting the amount of springback after bending.

Integral Hydro-Bulge Forming Method of Spherical Pressure Vessels Using a Triangle Patch Polyhedron

AbstractThis paper proposes an integral hydrobulge forming (IHBF) method using a triangular patch polyhedron as the closed preform shell. When triangular flat parts are welded along the edges in sequence, triangular patch polyhedra are naturally formed. From the radius of the spherical pressure vessel, a design formula was derived to calculate the side lengths of the triangular flat plate parts. The water pressure, water volume, average strain of molding, and amount of springback after molding, which are necessary for implementing the IHBF for practical use, were also formulated. To verify the forming performance of the spherical pressure vessel using IHBF method, the finite element method was carried out, and a stainless-steel spherical pressure vessel with a thickness of 1.0 mm and a diameter of approximately 500 mm was fabricated using the proposed IHBF method. As a result, the measured shape error expressed as roundness to diameter ratio was 0.52%, and the calculated average plastic strain was 0.02, which was approximately 1/19 times of the forming limit strain of the material. The amount of springback after forming by calculation was approximately 0.7 mm, indicating that the amount of water required for IHBF was 5.90% of the volume of the spherical pressure vessel, while the required water pressure was no bigger than 2.3 MPa. The process directly utilizes triangular flat plate parts, eliminating the need for molds to process closed preform shells resulting in a low average plastic strain during forming, thereby improving the quality of the formed spherical pressure vessels.

An experimental investigation of formability of inconel sheet plate for different die angles and rolling directions in press brake bending

The formability of Inconel materials is important to be used in engineering applications such as in fields of aircraft and maritime. The aim of study is to investigate bending characteristic and formability of Inconel 625 material having a property of corrosion resistance and high strength. In the paper, spring-back phenomena of Inconel 625 sheets are focused on experimentally. The 4 specimens for each different die angle are prepared to be bent. The press brake is used for forming Inconel 625 sheets. The die angle is altered from 90˚ to 150˚. The different rolling direction such as 0˚ and 90˚ is chosen to investigate the effect of grain orientation on spring-back of Inconel sheets. The bending radius is constant and set as 2 mm for all bending tests. The spring-back angles and amounts are measured. Results show that as the bending angle is increased, the spring-back amount in units of angle is decreased averagely from 3.35˚ to 2.58˚ for 0˚ rolling direction and maximum spring-back angle is obtained at a die angle of 120˚ for rolling direction of 90˚. Finally, Erichsen cupping test is also applied to determine the deformability of Inconel sheets. It is demonstrated that cup height value has been found as 17.20 mm.

Investigation of the spring-back phenomenon in two-dimensional bending of continuous glass fiber-reinforced polyamide composite sheets

Thermoplastic composite sheets have great potential for use in industrial applications owing to their fast-forming properties in the mold. One of the important matters of forming is the tendency of the part to recover elastically after it comes out of the mold. This behavior affects the dimensional accuracy of the final part. In this study, V-bending experiments were carried out to understand the spring-back phenomenon of continuous glass fiber-reinforced polyamide-6 composite sheets. Unidirectional and cross-ply composite sheets were used in the experiments and bending angle, die radius, pressure, and dwell-time were investigated systematically. After bending, the spring-back angles of the parts were measured and the effects of the inspected parameters were compared. Also, variations in part thickness caused by spring-back were evaluated. Finally, the deformations in the specimens resulting from the residual stress were visualized with a scanning electron microscope. When the results were compared, it was determined that the bending conditions where the spring-back defect could be minimized were 6 mm radius, 90° angle, 120 s dwell-time, and 3 MPa pressure. Under these situations and in sheets bent 90°, the amount of spring-back was determined as 22° for unidirectional composites and 15° for cross-ply composites.

An efficient closed-form solution for springback prediction and compensation in elastic–plastic creep age forming

Accurately predicting the amount of springback has always been a prior focus in metal forming industry, particularly for creep age forming (CAF), for its significant effect on tool cost and forming accuracy. In this study, a closed-form solution for CAF springback prediction covering deformation from elastic to plastic loadings was developed by combining the beam theory and Winkler’s theory, based on which an efficient springback compensation method for CAF was proposed. This developed solution extends the application area beyond the traditional beam theory-based springback prediction methods, maintaining its validity with large loading deflection in plastic range. Finite element (FE) simulation and four-point bending CAF tests adopting a 3rd generation Al-Li alloy were conducted in both elastic and plastic forming regions and the results showed close agreement with the closed-form springback predictions. For the proposed compensation method, an adjustment factor was introduced for complex flexible tool CAF to consider its deviation from the uniform stress loading and can be obtained using the closed-form solution. The flexible tool CAF tests using the Al-Li alloy demonstrated the applicability of the proposed compensation method to obtain the target shape within reasonable iterations, which can be further reduced by combining FE simulation.

Modelling and analysis of the specific cutting energy for ultra-precision diamond cutting of Ti6Al4V alloy

Ultra-precision diamond cutting (UPDC) is a promising method for fabricating precision parts of titanium alloys. Although energy consumption models have been proposed for conventional cutting methods with macro-cutting scale, few studies focus on the modelling of specific cutting energy for UPDC of titanium alloys with micro/nano-cutting scale. This study proposes an analytical specific cutting energy (SCE) model by fully considering two-phase material microstructures, spring back, size effect, cutting edge effect, temperature evolution and tool-chip frictional states. The theoretical and experimental results show that the significant cutting edge effect and large spring back amount jointly leads to the very high SCE at small undeformed chip thickness (UDCT). The minimum SCE is achieved at the transition UDCT where the cutting mechanism transforms from ploughing to shearing. Moreover, the severe resistance of dislocation movement induced by viscous drag effect results in the slightly increased SCE with increasing cutting speed. The heat accumulated at high cutting speeds can further increase the SCE through increasing the spring back amount of finished surface. The simulated SCE values are in good agreement the experimental results within an error of 6.3 %. By considering the round tool nose and tool wear rate, an energy-oriented machining parameters optimization method is proposed and validated to minimize the SCE in UPDC of titanium alloys.

Digitization of roll forming and its application

With the rapid development of metaverse and intelligent manufacturing, the requirement for the digitization of the traditional manufacturing process is a challenging task for industries. Roll forming is a highly efficient sheet metal forming process which can be widely been applied in a wide range of sectors, such as automotive, transportation, building other key sectors. However, this forming process is highly dependent on the experience of the on-site engineers. This paper presents a highly intelligent, flexible and self-adaption roll forming machine co-developed by the University of Electronic Science and Technology of China and data M. The machine consists of several flexible moving units controlled by codded stepper motors with a decent control system. Moreover, a high-performing artificial intelligence algorithm achieved from a systematic machine learning training process is integrated into this machine. The algorithm has already been use to predict and control the forming process to achieve a high-quality product. Data collection on a large scale and integrated sensors lead to an increased understanding of the process and provide the basis to develop self-optimizing roll forming machines, increasing the productivity, quality and predictability of the roll forming process. The application of digital twin and machine learning techniques is used to predict and reduce the amount of springback in the product. The first high-strength steel parts successfully manufactured with this new forming concept are presented.

An ABAQUS plugin for rotary draw bending of tight fit pipes

This paper investigates the bending of a Tight Fit Pipe (TFP). It is a double-walled pipe with a corrosion-resistant alloy (CRA) liner fitted inside a carbon steel outer pipe through thermal-hydraulic production. Due to the effects of various variables, such as the process of production of a double-walled pipe, the initial imperfections in the inner pipe, and the mandrel location in rotary draw bending (RDB) without defects, it is not easy to study TFP bending. For efficient process modeling, a new plugin is developed. With this plugin, the production and bending are easily simulated and present the final bending quality (separation, wrinkling, ovality, and springback) in a few diagrams wholly and concisely. A stress histogram is introduced to quantify the investigation of separation between pipes and wrinkling. The plugin evaluates the ovality diagram, and the amount of springback is presented directly. Then the production and bending processes are performed experimentally, and the capability of the plugin is investigated. Due to the adaptation of residual stress in the production process and the plugin results, the simulation accuracy in the production process is confirmed. Then the comparison of wrinkling at the end of the process shows good agreement between the results of the presented plugin and the experimental results.

Yüksek Mukavemetli Çeliklerde Geri Esnemenin Kalınlık Azaltma Yöntemi ile Telafisi

The sheet metal bending process plays an important role in sheet metal production and springback is an unintended consequence of this operation. If the bending die process is performed without knowing the amount of springback, it is difficult to produce parts within acceptable tolerance values. The springback behavior of the part to be bent also affects the size of the bending die. In particular, in the case of a 90° U bend die, the manufacturing cost of the bending die with the springback compensation method is high. Therefore, it is important to estimate the springback value at the design stage. In this work, the estimation of the amount of deformation to avoid springback value was performed using the thickness reduction method for high strength sheet metal. According to this study, the thickness reduction method can be used effectively in springback compensation. The estimation of the measurement accuracy at the design stage reduces the cost of the bending die and it is possible to produce parts within tolerance limits without much experimentation. The results showed that thickness reduction at the 0,2 t value was suitable to eliminate the springback value in the U-bending process. It has been found that experimental, empirical and finite element results are close to each other.

Parameter Identification of Chaboche Model for Aluminum Alloy Sheets Based on Differential Evolution Algorithm

Springback prediction is one of the most challenging in finite element analysis for sheet metal forming processes. The demand requests the development of a kinematic hardening model and parameter identification. This study presents a schematic strategy to identify parameters of Chaboche’s kinematic hardening model based on a differential evolution optimization method. To this goal, several tension-compression (TC) tests were conducted to observe the Bauchinger’s effects and kinematic hardening behaviors of two aluminum alloy sheets: AA6022-T6 and AA7075-T76. A Python code is developed to apply the proposed method in identifying parameters of the kinematic hardening model. The calibrated material models were implemented in Abaqus software to simulate V-bending and U-bending tests for the investigated materials. The predictions for springback amount match well with the experimental measurements, which verifies the effectiveness of the presented identificationstrategy.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.