Tube In Rotary Draw Bending Research Articles

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.

Significant analysis of the influence of process parameters on the wrinkling of aluminum alloy double-wall gap tube in rotary draw bending

Aluminum alloy double-wall gap tube is prone to wrinke in the rotary draw bending because the rigidity of the inner and outer tubes of the thin-walled structure is low, the mechanical properties between the tubes and the polymer filling medium are different greatly, and the bending forming is a complex nonlinear process of multi-mold coordination and multifactor coupling. While the process parameters are the main factors that affect the wrinkling of inner and outer tube, there are many process parameters and there are interactions among them. Therefore, based on the platform of ABAQUS/Explicit, elastic-plastic 3D-FE model of double-wall gap tube’s bending is established to study the influence mechanism of process parameters on the wrinkling aluminum alloy double-wall gap tube in rotary draw bending. The results show that the clearance between mandrel and inner tube, clearance between pressure die and outer tube, the anti-wrinkle die and the outer tube have significant effects on the wrinkling of the inner tube. The clearance between inner tube and core die, filling medium and inner tube and clearance between anti-wrinkle die and outer tube have significant effects on the wrinkling of inner tube. The wrinkling of the outer tube is more obvious than that of the inner tube. The results can provide a theoretical basis for optimizing the process parameters to suppress the wrinkling of aluminum alloy double-wall gap tube in the rotary-draw bending.

Strain distribution at the transition from bent to unbent regions in tube rotary draw bending: an in-situ, real-time measurement study

In tube bending processes, accurate control of springback is of crucial importance as this affects the dimensional accuracy of the final product and overall equipment efficiency. The distribution of stress and strain during bending is one of the most fundamental issues determining the springback magnitude of the product. In conventional analyses of rotary draw bending, the deformation behaviour along the bending direction is normally assumed to be uniform for constant-radius bends, following the contour of the die configuration. In practice, however, the stress-strain distribution is non-uniform, particularly at the transition between the bent and unbent regions of the formed component. The distribution makes a significant contribution to springback and its variations, especially for low bend-angle components. This research focuses on exploring the strain distribution at the end transition of the bend of aluminium tubes in rotary draw bending. An experimental test setup for strain measurements with a strain gauge glued to the unbent area has been designed and conducted to measure the strain distribution during bending. The characteristics of non-uniform strain distribution during tube bending, including the evolving transition behaviour at the transition between bent and unbent areas, are studied. The results enhance the understanding of deformation characteristics of bent tubes, and contribute to improved physically-based models and springback control routines in industrial practice.

Numerical modelling of Direct Hot Tube Rotary Draw Bending of 22MnB5 High Strength Steel

The use of High Strength Steel (HSS) tubular components in structural frames allows a drastic increase of the stiffness-to-weight ratio and, therefore, may open new possibilities to the design lightweight components for the transport industrial sector. However, the diffusion of these elements is still limited by the lack of manufacturing technologies capable of efficiently forming and bending HSS hollow profiles. To overcome the limits of traditional room temperature processes, an innovative rotary draw bending process carried out at high temperature is proposed, in which the profile cross section is quickly heated to the target temperature and, then, bent and selectively cooled to induce controlled microstructure changes. The paper presents a fully coupled thermo-mechanical-metallurgical numerical model to support the process design, which was applied to 22MnB5 tubes. The model was used to identify the optimal thermal and mechanical parameters to increase the material formability and to obtain the target microstructure in the final part. All the process steps, namely heating, handling, forming, and cooling, were modelled, and the results were experimentally validated by industrial trials carried out on a bending pilot plant. The results prove the possibility of an accurate prediction of both the final shape and the distribution of the microstructural and mechanical properties along the bend.

Effects of Process Parameters on Springback of High Strength 21-6-9 Tube Bending Considering Variation of Elastic Modulus

In order to improve forming quality of high strength 21-6-9 tube bending and achieve its precise bending forming, the springback behaviors of high strength 21-6-9 tube in rotary draw bending are investigated. Based on explicit/implicit finite element (FE) software of ABAQUS, the whole rotary draw bending FE model of high strength 21-6-9 tube considering variation of elastic modulus was established, and its reliability was verified. Then, the springback behaviors considering varied elastic modulus of high strength 21-6-9 tube in rotary draw bending under different process parameters were explored and compared that with constant elastic modulus. The results show that the variation tendencies of springback angle are similar with or without considering varied elastic modulus, but augments the value of springback angle with considering varied elastic modulus. Springback angle augments with the increase of the friction coefficient of tube versus mandrel, the friction coefficient of tube versus wiper die or with the decrease of the friction coefficient of tube versus pressure die, while the springback angle firstly declines and then augments with increasing the clearance of tube versus pressure die and the clearance of tube versus wiper die.

Insights on tube rotary draw bending with superimposed localized thermal field

The manufacturing of hollow section profiles using high strength metallic alloys may suffer of relevant drawbacks such as springback, reduced formability as well as wrinkling, which often limit the process capabilities. Localized heating of cross section sectors may allow a significant reduction of these issues thanks to the neutral layer shift and lowered yield stress. The paper describes an analytical approach to provide a fast prediction of the stress and strain distributions in the cross-section and their effects on the springback as consequence of the process thermal and mechanical parameters. Experimental and numerical validations confirm the analytical model reliability.

In-process measurement of springback in tube rotary draw bending

Rotary draw bending of tubes allows repeatable and accurate manufacturing with narrow bending radii and high production rates, thanks to modern CNC controlled electrical machines. However, springback still represents one the main issues especially in small production batches or when the geometrical and mechanical properties of the raw profiles are not constant within the batch. In-process inertial measurements may allow the close-loop process control of the bending angle and, potentially, offer the possibility to compensate the springback by a real-time tuning of the bending. The paper focuses on a newly developed in-process measurement technique and presents an assessment of in-process inertial springback measurements. The springback of bent tubes is investigated as a function of the measurement gauge position and of the cross-section strain distribution along the bend.

Cross section deformation of heterogeneous rectangular welded tube in rotary draw bending considering different yield criteria

Heterogeneous rectangular welded tube has serious anisotropy of parent metal and weld zone, in order to improve the prediction accuracy of cross-section deformation of tube in rotary draw bending (RDB), it is necessary to select the appropriate yield criterion to describe the anisotropic characteristics of heterogeneous rectangular welded tube. So the anisotropic parameters of Hill’48 and Barlat’89 yield criteria of parent and weld zone were obtained by using the digital image correlation test, then FE models of RDB of rectangular welded tube using different yield criteria were established. Based on these established FE models, the cross section deformation of thin-walled heterogeneous rectangular welded tube in RDB considering different yield criteria was researched. The results showed that, for the height and width deformation ratio of rectangular welded tube, the simulated results obtained by Mises, Barlat’89 and Hill’48 yield criteria in sequence, gradually increased to experimental results, this indicated that Hill’48 can well describe the anisotropic characteristic of rectangular welded tube. Further, under the condition of different bending angles and different core numbers, the maximum height deformation ratio obtained by Mises, Barlat’89 and Hill’48, successively, gradually increased to experimental results, which meant that Hill’48 anisotropic yield criterion was the most suitable one to predict cross section deformation of QSTE700 rectangular welded tube in RDB.

Effect of weld zone and corner with cold bending effect on wrinkling of rectangular welded tube in rotary draw bending

Wrinkling of QSTE700 high strength steel thin-walled rectangular welded tube is easy to occur in rotary draw bending (RDB) process due to the existence of non-homogeneous weld zone and corner with cold bending effect. So the FE model of RDB of QSTE700 rectangular welded tube considering weld zone and corner with cold bending effect was established. Based on this FE model, the effect of weld zone and corner with cold bending effect on wrinkling of inner flange and side wall of rectangular welded tube in RDB was researched. The results showed that: when weld zone and corner with cold bending effect were studied separately, weld zone both increased the wrinkling height of inner flange and side wall. However, the influence of corner with cold bending effect on wrinkling height of side wall and inner flange was inconsistent, it reduced the wrinkling height of inner flange, but increased the wrinkling height of side wall. When the weld zone and corner interacted, the coupling effect between weld zone and corner with cold bending effect on wrinkling resulted in the decrease of wrinkling height of inner flange and increase of wrinkling height of side wall of rectangular welded tube in RDB.

Deformation Property and Suppression of Ultra-Thin-Walled Rectangular Tube in Rotary Draw Bending

Recently, miniaturization and weight reduction have become important issues in various industries such as automobile and aerospace. To achieve weight reduction, it is effective to reduce the material thickness. Generally, a secondary forming process such as bending is performed on the tube, and it is applied as a structural member for various products and a member for transmitting electromagnetic waves and fluids. If the wall thickness of this tube can be thinned and the bending technology can be established, it will contribute to further weight reduction. Therefore, in this study, we fabricated an aluminum alloy rectangular tube with a height H0 = 20 mm, width W0 = 10 mm, wall thickness t0 = 0.5 mm (H0/t0 = 40) and investigated the deformation properties in the rotary draw bending. As a result, the deformation in the height direction of the tube was suppressed applying the laminated mandrel. In contrast, it was found that the pear-shaped deformation peculiar to the ultra-thin wall tube occurs. In addition, axial tension and lateral constraint were applied. Furthermore, the widthwise clearance of the mandrel was adjusted to be bumpy. As a result, the pear-shaped deformation was suppressed, and a more accurate cross-section was obtained.

Cross-sectional deformation of high strength steel rectangular welded tube in rotary draw bending with different constitutive relationships

An accurate constitutive relationship of rectangular welded tube is important to improve prediction accuracy of cross-section deformation in rotary draw bending by simulation. So five constitutive relationships of QSTE700 high strength steel rectangular welded tube were selected and determined. And five FE models of rotary draw bending process of rectangular welded tube by using these five constitutive relationships were built. Based on the above FE models, the effect of different constitutive relationships of rectangular welded tube on cross-sectional deformation in rotary draw bending process was studied. The results showed that height deformation ratio and width deformation ratio obtained by simulations were gradually increased to approach experimental results when using mixture-model, homogeneity model, W1H model, W2H model and W4H model, successively, and the simulation results obtained by W4H model were closest to experimental results, so the “weld and four heat affected subzones” model was suitable for describing the constitutive relationship of rectangular welded tube, which further meant that when the heat-affected zone was subdivided into more subzones, the constitutive relationship of QSTE700 rectangular welded tube became more accurate.

Experimental investigation of effective parameters in the tube rotary draw bending process

The rotary draw bending (RDB) process is one of the complex forming processes which is widely used for tube bending. There are different parameters in this process that incorrect selection of them cause the happening of some defects such as thinning and tube ovality. In the present study, the effects of main parameters of the RDB process is investigated on the thinning and ovality of BS 3059 steel tube using the experimental tests. Therefore, a design of experiment (DOE) base on the Taguchi method is used to investigate the effect of mandrel diameter, pressure of pressure die and mandrel position on the thinning of tube outer wall and the tube ovality. Four different values of 7 MPa, 10 MPa, 12 MPa, and 15 MPa are considered for the pressure of pressure die and four values of 7 mm, 15 mm, 20 mm and 34 mm for the mandrel position. The mandrel position is the distance between the mandrel and bending center. Two different chain link mandrels are used with balls diameter of 33.5 mm and 34.5 mm. The results showed that the mandrel position had the most significant effect on the thinning and tube ovality. Although the increase of mandrel position improved the thinning defect in the tube outer wall, the tube ovality increased by the increase of mandrel position from 20 mm to 34 mm. The results showed that the pressure of 7 MPa, mandrel position of 15 mm and the mandrel diameter of 33.5 mm were the best parameters for RDB of BS 3059 steel tube.

Failure Prediction of Superheater Tubes in Rotary Tube Bending Process Using GTN Damage Model

Superheater tubes are one of the main parts of boilers which are subjected to high temperature and stress. Fracture is one of the main defects which happen during the forming process of these tubes. In the present study, tube rotary draw bending (RDB) process is used for forming of superheater tube. Gurson–Tvergaard–Needleman (GTN) damage model is used for fracture prediction in the numerical simulation of tube RDB. Response surface methodology is coupled with the finite element to identify the GTN parameters. For this purpose, different sets of GTN parameters are used to simulate the uniaxial tensile test in the Abaqus software. Effect of GTN parameters is investigated on the predicted stress–strain curve of the uniaxial tensile test in the numerical simulation. The best-identified GTN parameters are used in the finite element simulation of tube RDB of superheater tube. Results indicate that there is an appropriate agreement between the predicted fracture location of the numerical and experimental sample after RDB.

Modelling of hot rotary draw bending for thin-walled titanium alloy tubes

Titanium alloys tubes are largely used to manufacture structural parts and piping elements that work at high temperature in many applications of transport industry, thanks to their high strength-to-weight ratio and excellent corrosion resistance. Among the available manufacturing methods, tube rotary draw bending is the most promising to achieve challenging shapes with high level of accuracy and process robustness, even if defects, such as wrinkling, over thinning, distortion of the cross-sections and springback, are still critical to be controlled. At the same time, titanium alloy tubes can be hardly shaped at room temperature due to their high yield strength and low ductility. The use of temperature-assisted processes might allow overcoming the above-mentioned limitations, but, at now, such processes have not been investigated in depth. In this context, the paper aims at investigating by numerical simulations the effects of selective heating in the rotary draw bending of thin-walled titanium alloy tubes. A numerical model of the process was developed to investigate different heating strategies and process temperatures. The obtained results show that selective heating is promising and capable to influence the quality of the bent tubes.

Influence of mandrel parameters on cross-sectional deformation of H96 double-ridged rectangular tube with ridge groove fillers in H-typed rotary draw bending

Rigid mandrel plays an important role in restricting the cross-sectional deformation of double-ridged rectangular tube in rotary draw bending. So a 3D FE model of H-typed rotary draw bending of the tube was established, and the influence law of rigid mandrel parameters on cross-sectional deformation was obtained. With the increase of core number, the deformation of different parts of tube decreases. When core number exceeds 3, the effect of increasing the core on the improvement of cross sectional deformation is insignificant. A curved mandrel with simple structure was proposed, and the effect of curved mandrel on controlling of cross-sectional deformation is better than that of separated rigid mandrel.

An innovative PVC mandrel for controlling the cross-sectional deformation of double-ridged rectangular tube in rotary draw bending

In order to control the cross-sectional deformation of double-ridged rectangular tube (DRRT) in rotary draw bending (RDB), a PVC mandrel just supporting the back of ridge grooves was introduced. The characteristics of cross-sectional deformation of DRRT and its evolution with the new PVC mandrel were revealed numerically by comparing with that with the mandrel-core die. In order to evaluate the application scope of the new PVC mandrel, the cross-sectional deformation for different specifications of DRRT in RDB were also researched. The results show that: (1) the flange sagging Δh, space deformation between ridges Δd, and width deformation of inner ridge groove Δw by using the new PVC mandrel can be better controlled than that by using the mandrel-core die. But the width deformation of the outer ridge groove ΔW gets a little larger; (2) by using the new PVC mandrel, the maxima of absolute values of Δh and Δw and the maximum of ΔW all increase firstly with the process of bending and then change little when the bending angle is larger than 60°, which are consistent with the variation of the peak value of tangent stress on the flange, while the maximum of absolute value of Δd increases continuously. (3) For small-sized DRRT, its cross-sectional deformation can be well controlled by using the new PVC mandrel. However, with the increase of dimension of DRRT, the cross-sectional deformation of DRRT increases obviously, and its distribution is extremely non-homogeneous.

Study on cross-sectional deformation of rectangular waveguide tube with different materials in rotary draw bending

Abstract

Multi-Objective Parameter Optimization for Cross-Sectional Deformation of Double-Ridged Rectangular Tube in Rotary Draw Bending by Using Response Surface Methodology and NSGA-II

Cross-sectional deformation of double-ridged rectangular tube (DRRT) inevitably occurs due to the inhomogeneous deformation induced by external boundary conditions in rotary draw bending (RDB). Unreasonable factor combination would aggravate the cross-sectional deformation of DRRT. So, a powerful and efficient method combining Response Surface Methodology (RSM) and Non-Sorted Genetic Algorithm II (NSGA-II) was proposed to optimize the factors to control the cross-sectional deformation of DRRT in RDB. Firstly, an orthogonal experiment was used to screen out the important factors. It was obtained that three factors—clearance between DRRT and mandrel, clearance between DRRT and bending die, and boosting of pressure die—have an important influence on the cross-sectional deformation of DRRT. It can also be observed that the variation trend of flange sagging (FS) is always consistent with that of space deformation between ridges (SDR) with the changing of factors. RSM based on a Box-Behnken design was then used to establish response surface models. The proposed response surface models were used to analyze the relationship of the important parameters to the responses, such as space deformation between ridges, and width deformation of outer and inner ridge grooves (WDO and WDI). Finally, multi-objective parameter optimization for the cross-sectional deformation of DRRT in RDB was performed by using the established model and NSGA-II algorithm. The interaction of responses was revealed and the value range of each response in the space of Pareto optimal solutions was determined. It can be observed that there is always an evident conflict between SDR and WDO in the space of Pareto optimal solutions. By using this optimization method, the absolute values of SDR and WDI were significantly reduced—by 13.17% and 17.97%, respectively—compared with those before optimization, while WDO just increase only a little.

Dynamic Detection of Instability Defects in tube Rotary Draw Bending

Tube rotary draw bending is commonly used to manufacture complex shaped elements in a wide range of geometries and applications. When thin-walled tubes are formed with small bending radii, the components may suffer of wrinkling at the intrados due to the critical process parameters. Off-line optimization approaches, which aim at predicting the correct process parameters and tool geometries, often require accurate data of the workpieces properties or the application of numerical simulation analyses, that may fail due to the scatter of such properties along the production batches. Therefore, the availability of on-line approaches to provide an adaptive response of the machine is crucial for the efficiency of highly automated production lines.The paper presents the investigations carried out to assess the capability of dynamic analysis techniques to detect the instability defects that may affect the tubes in critical operating conditions. A new experimental approach, based on the analysis of dynamic data from the machine, is presented, as well as the evaluation of its performances when applied to the industrial process. The proposed approach appears promising for the detection of wrinkling, once they appear on the tube, and capable to give accurate feedback for the fast adjustment of the process parameters.

Study on the ridge grooves deformation of double-ridged waveguide tube in rotary draw bending based on analytical and simulative methods

Cross sectional deformation of double-ridged waveguide tube easily occurs in rotary draw bending due to its structural features of hollowness, thin-wall and shape complexity. Particularly, the ridge grooves deformation would largely affect the transmission characteristics of double-ridged waveguide tube. Thus, using plasticity deformation theory, an analytical method to investigate the ridge grooves deformation is proposed, in which the ridge grooves deformation is considered to be resulted from three parts of deformation, including flange sagging, web deflection and variation of flange width. Then, the analytical method is verified by a FE model from various viewpoints. Finally, the contribution of every part to the ridge grooves deformation under different conditions is analyzed combining analytical and simulative methods. The results show that: (1) The contribution of flange sagging to the width deformation of outer and inner ridge grooves is usually far small and can be omitted. The web deflection results in the decrease of width deformation of outer ridge groove, but the variation of flange width increases that. The web deflection and variation of flange width all lead to the increase of width deformation of inner ridge groove. (2) With the increase of bending angle, the width deformation of outer ridge groove changes little while the absolute value of width deformation of inner ridge groove increases. When the bending radius decreases, the absolute value of width deformation of outer and inner ridge grooves all increase. With the increase of core number, the width deformation of outer ridge groove changes from shrinking to widening while there is no change for the width deformation of inner ridge groove.