springback angle
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Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1418
Author(s):  
Daniel J. Cruz ◽  
Manuel R. Barbosa ◽  
Abel D. Santos ◽  
Sara S. Miranda ◽  
Rui L. Amaral

The increasing availability of data, which becomes a continually increasing trend in multiple fields of application, has given machine learning approaches a renewed interest in recent years. Accordingly, manufacturing processes and sheet metal forming follow such directions, having in mind the efficiency and control of the many parameters involved, in processing and material characterization. In this article, two applications are considered to explore the capability of machine learning modeling through shallow artificial neural networks (ANN). One consists of developing an ANN to identify the constitutive model parameters of a material using the force–displacement curves obtained with a standard bending test. The second one concentrates on the springback problem in sheet metal press-brake air bending, with the objective of predicting the punch displacement required to attain a desired bending angle, including additional information of the springback angle. The required data for designing the ANN solutions are collected from numerical simulation using finite element methodology (FEM), which in turn was validated by experiments.


Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5044
Author(s):  
Guangjun Li ◽  
Zirui He ◽  
Jun Ma ◽  
Heng Yang ◽  
Heng Li

Titanium bent tubular parts attract extensive applications, thus meeting the ever-growing demands for light weight, high reliability, and long service life, etc. To improve bending limit and forming quality, local-heat-assisted bending has been developed. However, significant springback seriously reduces the dimensional accuracy of the bent tubular parts even under elevated forming temperatures, and coupled thermal-mechanical working conditions make springback behavior more complex and difficult to control in warm bending of titanium tubular materials. In this paper, using warm bending of thin-walled commercial pure titanium tube as a case, a coupled thermal-mechanical finite element model of through-process heating-bending-unloading is constructed and verified, for predicting the springback behavior in warm bending. Based on the model, the time-dependent evolutions of springback angle and residual stress distribution during thermal-mechanical unloading are studied. In addition, the influences of forming temperature and bending angle on springback angle, thickness variation, and cross-section flattening of bent tubes are clarified. This research provides a fundamental understanding of the thermal-mechanical-affected springback behavior upon local-heat-assisted bending for improving the forming accuracy of titanium bent tubular parts and structures.


Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3856
Author(s):  
Jae-Hyeong YU ◽  
Chang-Whan Lee

In this study, the time-dependent mechanical behavior of the magnesium alloy sheet (AZ31B) was investigated through the creep and stress relaxation tests with respect to the temperature and pre-strain. The microstructure changes during creep and stress relaxation were investigated. As the tensile deformation increased in the material, twinning and dynamic recrystallization occurred, especially after the plastic instability. As a result, AZ31B showed lower resistance to creep and stress relaxation due to dynamic recrystallization. Additionally, time-dependent springback characteristics in the V- and L-bending processes concerning the holding time and different forming conditions were investigated. We analyzed changes of microstructure at each forming temperature and process. The uniaxial tensile creep test was conducted to compare the microstructures in various pre-strain conditions with those at the secondary creep stage. For the bending process, the change of the microstructure after the forming was compared to that with punch holding maintained for 1000 s after forming. Due to recrystallization, with the holding time in the die set of 60 s, the springback angle decreased by nearly 70%. Increased holding time in the die set resulted in a reduced springback angle.


2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098430
Author(s):  
Huifang Zhou ◽  
Shuyou Zhang ◽  
Lemiao Qiu ◽  
Zili Wang

The springback directly affects the forming accuracy and quality of metal bent-tube, and accurate springback prediction is the key to the springback compensation and control. This paper investigates the springback of mandrel-less rotary draw bending (MLRDB) of circular metal tubes, and an innovative method, springback angle prediction considering the interference of cross-sectional distortion (IoCSD-SAP), is proposed. The digit decomposition condition variational auto-encoder generative adversarial network (D2CVAE-GAN) is developed to augment the data samples. Considering the nonlinear interference of the cross-sectional distortion on springback, auxiliary extended radial basis function (AE-RBF) is proposed. It establishes the mapping relationship between the characteristic parameters and cross-sectional distortion. By extracting the information encode of cross-sectional distortion as the condition input, this model realizes the condition prediction of springback angle. Taking MLRDB of 6060-T6 Al-alloy circular tube as a case study, the proposed method, IoCSD-SAP, is verified. According to the experimental results, the mean absolute percentage error (MAPE) for the springback angle of our proposed method is 4.73%, and three different analytical models are 38.92%, 14.39%, and 14.22%, respectively. It can be seen that our proposed method significantly improves the prediction accuracy of springback angle. For the springback angle prediction of circular metal tube in MLRDB, the data augmentation can effectively reduce the generalization error and improve the prediction accuracy. The nonlinear interference of the cross-sectional distortion on springback should be taken into account to improve the accuracy and robustness of the springback prediction model.


Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4929
Author(s):  
Xin Guan ◽  
Zhenwu Ma ◽  
Chunju Wang ◽  
Haidong He ◽  
Yuanjing Zhang ◽  
...  

The prediction of springback angle for ultra-thin metallic sheets becomes extremely difficult with the existence of size effects. In this study, size effects on the springback behavior of CuZn20 foils are investigated by experiments and analytical methods. The experimental results reveal that the springback angle first decreases gradually and then increases markedly with the decrease of foil thickness, which cannot be analyzed by current theoretical models. Then, an analytical model based on the Taylor-based nonlocal theory of plasticity is developed, in which the drastic increases of both the proportion of surface grains and the strain gradient are taken into account. Moreover, the influence of strain gradient is modified by the grain-boundary blocking factor. The calculation results show that the springback angle of foils is determined by the intrinsic competition between the decrement angle caused by surface grains and the increment angle caused by the strain gradient. Besides, the relative error of predicted springback angle by the model is less than 15%, which means that the developed model is very useful for improving the quality of micro sheet parts with high accuracy of springback prediction.


Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 892 ◽  
Author(s):  
Chuanjie Wang ◽  
Shan Wang ◽  
Shuting Wang ◽  
Gang Chen ◽  
Peng Zhang

With the increasing demand for micro parts using metal laminates in modern production, the manufacturing processes of thin sheet parts have been elevated. However, it is difficult to predict the deformation behavior with miniaturization because of size effects in micro-scale. In this study, the flexible die micro V-bending behavior of Cu/Ni clad foils was investigated. The bending experiments with three different punch angles and Cu/Ni clad foils under different annealed temperatures were performed. The results show that the springback angle increases with the increase of bending angle and annealing temperature. The placement of Cu/Ni clad foils induced compressive stress results in the more obvious thinning of thickness and decreasing of springback angle. The interactive effects of the distribution of deformation zones and compressive stress induced by the interface layer result in the springback behavior of Cu/Ni clad foils during the flexible die micro V-bending process.


2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Lidong Ma ◽  
Haoxi Ma ◽  
Zijian Liu ◽  
Shuo Chen

Flexible forming excellent (FFX) forming of electric resistance welding (ERW) pipe is an advanced roll forming method. In order to understand FFX forming mechanism and set reasonable roll parameters, five-point bending process and springback process for preforming section of ERW pipe FFX forming are analyzed. Under various assumptions, the bending process of sheet metal is divided into full elastic bending stage and elastic-plastic bending stage by analyzing the forming law and simplifying the contact state model of roll bending process. Based on the theory of plane bending theory, the five-point bending springback model is established. Mathematical expressions of bending curvature and rotation angle of arbitrary particle on plate under arbitrary state are derived. The curvature calculation formulas of each particle on plate after springback are obtained, and then the calculation formulas of bending angle and rebound angle after springback are obtained. The theoretical analysis results are verified by the wide plate five-point bending experiment. The theoretical value of springback angle agrees well with the experimental results. The maximum deviation of springback angle is 0.42 degrees. The results show that the five-point bending model is reasonable. It provides theoretical support for the preforming model of flexible roll forming.


Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 694 ◽  
Author(s):  
Xiangji Li ◽  
Xu Yan ◽  
Zhiqiang Zhang

Different from traditional hot stamping components with full martensite, the new tailored hot stamping (THS) components have different quenched microstructures, which results in their lower shape accuracy. To investigate the influence of different quenched phases on the springback of a component, a THS experiment of a U-shaped component was performed with segmented heating and a cooling tool. The area fractions of phases at different tool temperatures were obtained by a two-stage color tint etching procedure. Results showed that the quenched phase of the cold zone was almost full martensite. The area fraction of martensite in the hot zone was reduced to the lowest 13% at the tool temperature of 600 °C, while the bainite content reached the highest at 70%. The springback angles at different tool temperatures for quenching were measured by 3D scanning technology and the reverse modeling method. It was revealed that the springback angle increased with the increase of martensite and yet decreased with the increase of bainite. The relationship between the springback angle and the area fractions of the quenched phases was established by means of multiple linear regression analyses. The error analysis results of the predictions and measurements showed that the springback analysis model, based on the area fractions of quenched phases, could be used to predict the springback of hot stamping components with tailored properties.


2018 ◽  
Vol 192 ◽  
pp. 01018
Author(s):  
Natthasak Pornputsiri ◽  
Kannachai Kanlayasiri

In this study, process parameters such as the bending angle and bending temperature of the metal sheets for pure bending of advanced high strength steel sheet DP980 were investigated using the air-bending method. This investigation focused on bendability and failure mechanisms. Experimental studies were carried out with various bending temperatures and the bending angle parameters to identify effect on springback angle, initial crack, and the evolution of the microstructure. Prior to testing, the DP steel sheets were heattreated at different temperatures (room temperature, 200 °C, 400 °C, and 600 °C) with a heating rate of 2 °C/S and 5 minutes of holding time in an electric furnace. As a result of the experiments performed at different temperature values and bending angle values, it was determined that an increase in the bending angle reduces the size of the springback angle. It was also determined that an increase in air-bending-temperature reduces the amount of springback. Air-bending-temperature also affected the microstructure evolution and slowed the cracking of the bent surface.


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