Draw Bending Research Articles

Defects in Rotary Draw Bending and Their Effects on Formability

Tube with different quantities and types; It can be described as a long and narrow cylinder with open ends, which carries liquids, gases and similar substances from one place to another. Tubes are used for advancements in sectors such as transportation, automobiles and aerospace. Aluminum, Inconel and titanium materials are decided according to the required needs in the design and production of tubes. There are different production methods to give permanent shape to the tubes. During tube bending operations, the feasibility of tube bending varies depending on the material type, bending angles, bending radius, tools and process. The tubes produced with a certain margin of defect. Some defects occur during and after production. Springback, ovality, breakage and tearing are among these defects. These defects may prevent the system to be replaced from flowing with the desired properties, as well as the installation of the produced tubes. The aviation and space fields, the production of tubes with high strength and complex geometries is critical. Errors that occur in the rotary draw bending process, one of these pipe bending methods, and the steps to prevent these errors are compiled and presented.

Effect of weld-line position on springback behavior in advanced high-strength steel tailor-welded blanks on hat-shaped bending application

In this study, both experiments and finite-element analysis are performed to elucidate the effect of weld-line position on the springback behavior of advanced high-strength steel tailor-welded blanks (AHSS-TWBs). AHSS-TWBs are fabricated from grade 590Y high-strength steel and 980Y advanced high-strength steel, each with a thickness of 1.2 mm. Gas tungsten arc welding is performed to obtain autogenous butt-weld joints. Three distinct weld-line position patterns are systematically analyzed to investigate the springback phenomenon via hat-shaped draw bending. Experiments on the AHSS-TWBs show that the weld-line position affects springback. The stress distribution changes with the weld-line position, thereby initiating variations in both the components of the bending moment and the corresponding springback angle. Depending on the weld-line position, different springback behaviors and bending moments are resulted on the components.

Additive manufacturing of polymeric pressure die for rotary draw bending process

3D printing or additive manufacturing (AM) possesses enormous potential to benefit the manufacturing industry. Presently, rotary draw bending (RDB) is one of the most commonly used cold-forming industrial process for bending metal tubes. Pressure die is a fundamental forming tool in RDB processes, and it is conventionally made by various grades of comparatively expensive alloy steels. This research presents a novel design of a pressure die which can be 3D printed by using inexpensive polymeric filaments. In this research paper, the 3D-printed pressure die is named as “FFF-pressure die.” The material used to fabricate the FFF-pressure die is a thermoplastic polymer known as “ecoPLA.” The mechanical properties of ecoPLA are studied in relation to the process conditions of a RDB process. Firstly, an initial feasibility of using the FFF-pressure die in a RDB process is obtained by conducting a quick static stress analysis with actual process conditions. After initial feasibility, a complete RDB process is developed and simulated with actual process conditions and material properties. The FFF-pressure die is then practically fabricated by FFF 3D printer and experimentally tested on an industrial RDB machine. The results of practical experiments are compared with the simulation results. In order to make a comparison of the FFF-pressure die with the conventional metal pressure die, the simulation and practical process is also conducted with the conventional metal pressure die. A performance and cost comparison is made between the polymeric FFF-pressure die and the conventional metal pressure die. Von Mises stresses, contact forces, failure risk, and elastic deformations are analyzed. The advantages and limitations of using the FFF-pressure die in a RDB process are discussed in the end. This research intends to widen the avenue of using cost-effective and lightweight forming tools in metal forming industries.

Topology optimization of forming tools: pressure die in rotary draw bending process

AbstractThe forming tools are conventionally manufactured from alloy steels. These tools can be designed to be light weight and cost effective without compromising performance characteristics. In this research, a fundamental forming tool (pressure die) of ‘rotary draw bending processes’ is topology optimized and 3D printed by using polymeric material. An accurate FE-simulation model of a rotary draw bending process is developed and topology optimization of the pressure die is carried out on the basis of contact stresses provided by FE-simulation results. The topology optimized pressure die is compared with its conventional metal made counter-part in terms of contact forces, contact normal stresses, effective area in-contact and cost performance index. This manuscript demonstrates that topology optimized lightweight 3D printed polymeric forming tools are a cost effective alternative to comparatively heavy alloy steels. This research contributes to widen the avenue of cost effective manufacturing by incorporating topology optimization regimes into existing production setups.

A Comparison of Internal Mandrel Designs for Rotary Draw Bend Forming of Carbon-fibre/Thermoplastic (PA6) Tubular Structures

Carbon fibre reinforced thermoplastic tubular structures can be post-formed into desired curvatures via rotary draw bending (RDB) at elevated temperatures. During this process, a rigid internal mandrel is required to support the walls of the tubes to maintain their ovality and minimise unwanted geometrical distortions. This paper investigates four internal mandrel designs for post-forming carbon fiber reinforced polyamide 6 (CF/PA6) thermoplastic tubes. Mandrel designs include silicone rod, bullet, wire, and coil spring, were evaluated through RDB-forming experiments with [± 60°]4 CF/PA6 tubes formed to 90° bends. The designs were evaluated for their effectiveness on minimising distortions resulted from induced stresses during post-forming by measuring the post-formed tube diameter and extrados strains. The mandrel designs were also evaluated for their usability when integrated into the RDB process. Results from optical measurements and micro-computed tomography showed the spring mandrel outperformed others, producing tubes with the least geometrical distortions and no defects during the forming process. As compared to other designs, the spring mandrel is a reusable unibody design that is easy to assemble and remove from the tubes.

Residual Stress Distribution in Aluminum/Polypropylene/Aluminum Sandwich Laminates in U-Channel Draw Bending

Residual Stress Distribution in Aluminum/Polypropylene/Aluminum Sandwich Laminates in U-Channel Draw Bending

Comparison of resistance rotary draw bending of CP-Ti tube with different mandrels

Comparison of resistance rotary draw bending of CP-Ti tube with different mandrels

Effect of the internal pressure in the rubber mandrel on the defects of the rotary draw bending process

Effect of the internal pressure in the rubber mandrel on the defects of the rotary draw bending process

Support software for plastic bending of waveguides on a rotary draw bending machine

The paper addresses the problem of ensuring the bending quality of the waveguide on an automated pipe rotary draw bending machine by winding. This bending method is currently the most common, but has limitations on the allowable values of bend angles and radii, which ensure the accuracy and quality of the bend region geometry without losing the stability of the section shape in the form of wrinkles and ruptures. Modern requirements for minimizing dimensions and masses require the use of the minimum possible bending radii, which depend on the geometry of the section and the material of the work piece. Calculations to determine the limits of permissible bend parameters using general or special purpose programs are very time-consuming require high-performance computers and high qualification of the computing engineer. To solve this problem, it is proposed to create support software that, based on interpolation of results of more accurate calculations, allows you to determine the areas of permissible bend parameters for the selected shape and section dimensions, as well as the work piece material. This approach allows you to quickly obtain solutions for both the engineer in the design of the structure and the operator of the pipe bending machine and to obtain a product with guaranteed bending quality.

Study on cross-section distortion behaviors for tube bending at varying geometry parameters

Tube bending is often plagued by the critical forming defect of cross-section distortion, which increases flow resistance, affects the strength and stiffness of bent-tube, and thus directly influences the usage performance of bent-tube components. To achieve accurate tube bending forming, the distortion behaviors for cross-section during tube bending should be clarified. A finite element (FE) model accounting for the change in elastic modulus was employed for addressing the distortion behaviors of the cross-section for high strength 0Cr21Ni6Mn9N (0Cr21Ni6Mn9N-HS) tube in NC rotary draw bending at varying geometry parameters. The findings indicate that accounting for the change in elastic modulus can aggrandize the distortion ratio of the cross-section, but has no significant impact on the distortion behaviors for the cross-section. The cross-section ovality behaviors of the 0Cr21Ni6Mn9N-HS tube at various geometry parameters for NC rotary draw bending have been clarified, and the ranges of sound parameters have been determined.

Feasibility study of resistance hydro rotary draw bending of commercial pure titanium tubes

Feasibility study of resistance hydro rotary draw bending of commercial pure titanium tubes

A transferred hybrid surrogate model integrating Gaussian membership virtual sample generation for small sample prediction: Applications in metal tube bending

The high-performance virtual sample generation (VSG) method has been extensively introduced to solve the problem of small sample sizes. Data distribution information is a key element of current VSG methods at the data-driven level. Herein, we propose an improved VSG method with a Gaussian distribution and explore the relationship between the Gaussian function and data expansion. To obtain more feasible virtual samples, information expanded based on the Gaussian membership function (GMIE) was established. For further improvement, a hybrid surrogate model based on transfer (THSM) is proposed, which differs from the general hybrid surrogate model (HSM) methods that only mix single models. Using a prevailing evaluation method, our proposed method, which combines a Gaussian membership function with a hybrid surrogate model, outperforms other competing approaches in 12 numerical cases owing to its feasibility and efficacy. Additionally, the proposed approach is applied to a metal tube rotary draw bending (RDB) prediction problem to illustrate its ability to support complex engineering designs.

Experimental investigation and numerical simulation of the effect of type of bending die on the quality of tube forming in rotary draw bending process

This study introduces a new rotary draw bending method that utilizes a variable curvature bending die. Unlike traditional methods that bend tubes with a fixed radius, this method gradually deforms the tube from a large to a small radius. The curvature of the bending die is determined by using an involute curve as the equation for the geometric location of the variable curvature. Hydroforming technology, utilizing fluid under pressure, replaces the mandrel in the rotational tensile bending process. The research was conducted using a thin-walled AA6063 tube with a 13.88 diameter-to-thickness ratio. The bending process was examined at critical bending ratios of 1 and 1.6 times the diameter, with a 90° bending angle. The maximum pressure that can be applied in any bend radius ratio was predicted using the necking criterion. The simulation and experimental tests analyzed the effects of internal fluid pressure and bend die curvature on defects such as wall thinning in the outer curvature of the bend, thickening of the wall in the inner curvature of the bend, and cross-section non-roundness. The results indicate that, at constant pressure, the amount of thinning and thickening of the bent tube is significantly improved when using the variable radius bending die compared to the fixed radius die.

The effect of aging heat treatment on the formability and microstructure of the AA6063 tube in the rotary draw bending process

This research delves into the impact of aging heat treatment on both the formability and microstructural characteristics of 6063 aluminum tubes when subjected to the rotary draw bending (RDB) procedure. To ascertain a heat treatment regimen that can yield desirable hardness and formability for the bending process, the tube was subjected to T3, T6, and annealing heat treatment cycles under diverse conditions and subsequently the tube's bendability was evaluated. The findings indicate that as temperature and dissolution time are raised, there is a corresponding rise in the extent of elliptical deformation, consequently resulting in higher hardness values. The research outcomes suggest that elevating both temperature and dissolution time leads to a more pronounced elliptical shape in the bent sample. For instance, when subjected to heat treatment at 530 °C and 545 °C for 60 min, the samples exhibited respective increases in ellipticity of 5.30 % and 4.34 % compared to those treated for just 30 min. Additionally, higher internal pressure led to a reduction in the degree of elliptical deformation, notably a decrease of 9.85 % observed at a pressure of 20 bar. Moreover, the hardness of samples subjected to the T3 cycle exhibited an upward trend with increasing both temperature and duration of heat treatment. To elaborate, the hardness measurements were conducted at three distinct temperatures (530 °C, 545 °C, and 560 °C) and four different durations (30, 45, 60, and 75 min). The sample subjected to a 75-minute heat treatment at 560 °C exhibited the highest recorded hardness value, measuring at 62.55 HV. In summary, the results indicate that aging heat treatment can enhance the formability of 6063 aluminum tubes during the RDB process. Furthermore, it is noteworthy that temperature and internal pressure serve as crucial parameters to control in order to mitigate elliptical deformation and enhance hardness.

Cross-sectional performance prediction of metal tubes bending with tangential variable boosting based on parameters-weight-adaptive CNN

Metal bending tubes have been widely used in various fields owing to their excellent performance; however, bending defects significantly affect their quality. This study proposes a tangential variable boosting (TVB) scheme to reduce the severity of multiple defects generated during the rotary draw bending (RDB). The boosting pressure die is divided into several parts. Different process parameters were applied to the divided semi-parts based on the tangential stress distribution trend. To explore the effects of the TVB, a cross-sectional defect prediction method is proposed based on a parameter-weight-adaptive convolutional neural network (PWA-CNN). To validate the proposed prediction method, a dataset for training the prediction model was constructed using a series of numerical simulations of aluminum-alloy tubes. The prediction results of the PWA-CNN were then compared with those of the other CNNs and different weight assignment methods. The comparison results show that the PWA-CNN exhibits the best performance in predicting the tube cross-sectional distortion. Finally, the effects of the TVB on the forming quality of the bending tubes were obtained. A reasonable TVB is beneficial for reducing the wall-thinning and contour distortion ratios of the tubes and has a negligible effect on the short-axis variation rate.

Bo-LSTM based cross-sectional profile sequence progressive prediction method for metal tube rotate draw bending

Predicting the cross-sectional profile of the whole bending segment for metal tube bending is essential to achieve high-precision bending, yet still remains challenging. The existing prediction methods mainly base on theoretical derivation under certain assumptions and approximations, which do not fully characterize the whole bending segment profile neither do they fully utilize the information in the bending process. In this study, a Bo-LSTM-based progressive prediction method for the cross-sectional profile sequence is proposed, which comprehensively utilizes the profile information during the bending process and achieves an accurate prediction of the cross-sectional profile of the whole bending segment in the subsequent bending process. Firstly, the method of describing the cross-sectional profile in polar radial vector and the cross-sections of the bending segment in discrete sequences are proposed, which cover the information of cross-sectional distortion and wall thickness variation (viz. cross-sectional defects) for the whole bending segment. Secondly, an LSTM network is constructed integrating Bayesian-optimization-based hyper-parameters selection approach to progressively predict the tube cross-sectional profile sequence. Finally, the proposed methods are verified on simulated datasets as well as experimental data, and the accuracy is compared with networks of different structures. The results show that Bo-LSTM has better prediction accuracy. Meanwhile, the progressive prediction pattern has better robustness compared to chain prediction pattern.

Investigation on the wall thickness variation of an eccentric tube in the rotary draw bending process

PurposeWhen bending a large diameter thin-walled tube, the thickn ess of outer side wall will reduce greatly, which leads to a decrease of structural strength of the tube. To solve this problem, this paper investigated the deformation principles of an eccentric tube in the rotary draw bending process, trying to find a way to reduce the wall thickness difference between inner and outer diameters.Design/methodology/approachAn finite element model is established for analyzing the deformation of an eccentric tube in rotary draw bending process. The wall thickness distribution of the formed pipe was analyzed along the axis and diameter, respectively.FindingsIt is found that there exists an optimal eccentricity between the inner and outer circle center of the tube cross-section. If the eccentricity of the tube is chosen properly, it is possible to get a bent tube with equal thickness of inner and outer side walls. In addition, it is also found the optimal eccentricity on the cross-section can be influenced by bending radius, wall thickness, diameter and bending angle. The optimal eccentricity increases greatly with the decreasing of bending radius, the increase of outer diameter and the increase of wall thickness. The influence of bending angle on the optimal eccentricity can be divided into two situations. When the bending angle is small, the optimal eccentricity increases with the increase of bending angle. When the bending angle exceeds a certain value, the pipe enters a stable forming state. The optimal eccentricity of the stable forming region does not change with the bending angle.Originality/valueSuch a research is beneficial for reducing the thickness difference between inner and outer side walls in the rotary draw bending process.

Sustainable profile bending: Wood-based forming tools

To enhance flexibility in a production age characterized by mass customization and individualization complying geopolitical climate targets at the same time, more sustainable approaches to profile bending are required to adapt to the corresponding manufacturing processes. Metal based rigid tooling systems consume a lot of material and energy resources, particular when aiming for high flexibility, low batch size or individualization. To reduce the overall resource consumption and to meet climate restrictions, non-metallic tooling approaches can counteract these issues when aiming for flexibility and individualization in profile and tube bending. Compared to conventional metal-based tooling approaches, wood-based forming tools may provide a potential resource reduction (e.g., carbon footprint) and offer a sustainable tooling alternative for tube and profile bending. For typical bending applications with low batch sizes and production volumes (e.g., freeform bending), the substitution of conventional rigid metal tools may reduce the environmental impact without compromising the economic objectives. Although the mechanical performance of wood is lower than that of conventional tool steel, certain wood-based forming tools can potentially be implemented for these bending applications. To layout the design of wood-based composite forming tools, a deeper understanding of the mechanical performance is required. In this work a feasibility study of wood-based tooling materials is carried out to investigate the mechanical performance on metal tubes and profiles for rotary draw and freeform bending. To determine the performance, different composite structures (thickness, orientation, base material) and geometries are investigated for wooden forming tools of black locust (robinia pseudoacacia). Finally the results are summarized to outline a potential process window for wooden forming tools for tube and profile bending.

Springbek optimizacija za CNC mašinu za savijanje cevi zasnovanu na veštačkim neuronskim mrežama (ANN)

Predicting the springback angle has become the major production problem among tube benders. Springback is where the tube on a mandrel-less rotary draw bending tends to bounce back after being bent when the clamps are released. Accurately predicting the springback angle is crucial for effective tube bending. Machine learning (ML), a popular prediction approach, was applied to functions such as prediction or function approximation, pattern classification, clustering, and forecasting. To achieve this, the springback angle values from 27 experiments were collected and used as input into artificial neural networks (ANNs) in one area of ML. This research was conducted to study the optimization of the springback angle when bending ASTM A-210 Gr. A1 seamless tube with an outside diameter of 44.45 mm, using the 4 input factors Wall Thickness, Bending Radius, Dwell Time, and Bending Angle. The results showed that all factors significantly influence the springback angle in the tube bending process; different prediction methods were analyzed by comparing the results using different activation functions. The results showed that the optimal neural network architecture is 4-98-1; these results were achieved using the Sigmoid function, giving the lowest mean squared error (MSE) = 0.001892. The resulting coefficient of determination (R2 ) = 99.42%, the ReLU function R2 = 98.99%, the TanH function R2 = 98.53%, and the Identity function, which was 79.53%. It was also found that the best prediction of the springback angle using the best regression equation, with R2 = 82.32%, was better than the prediction using the 65 neurons with the Identity function R2 = 79.53%, a 2.79% difference in favor of the regression equation.

Control of material flow using measuring methods for wrinkle and crack detection during rotary draw bending

Control of material flow using measuring methods for wrinkle and crack detection during rotary draw bending