Controlling Wrinkling and Flatness during the Processing of the Bend Section of a Pipe by Applying Vibration to the Mandrel

2015 ◽  
Vol 656-657 ◽  
pp. 600-603 ◽  
Author(s):  
Xia Zhu ◽  
Narumi Wada ◽  
Keiji Ogi ◽  
Hiroshi Kurosu ◽  
Manabu Takahashi ◽  
...  
Keyword(s):  
Nonlinear Finite Element ◽  
Outer Diameter ◽  
Bend Section ◽  
Finite Element Software ◽  
Bending Process ◽  
Bending Radius ◽  
Metal Pipes ◽  
Thin Walled ◽  
Pipe Processing ◽  
Distribution Of Stresses

Metal pipes have a long history as fluid conduits, and are commonly joined with components such as elbows to form bent transport paths. However, with the increasing demands for economy and energy saving, pipes with reduced joints and thinner walls are desired. The number of joints can be reduced by a drawing and bending process that forms a bend section at any position in the pipe. However, this approach incurs problems such as wrinkling and flattening, especially under conditions of large bending angle, decreased bending radius, and thin pipe walls. In this research, applying vibrations to the mandrel was trialed as an approach for controlling the wrinkle depth and flattening. First, processing experiments were performed on thin walled pipes (wall thickness = 0.5 mm; outer diameter = 14 mm). The change of flattening and the number and depths of wrinkles were investigated in the presence and absence of vibrations. Next, simulations were performed using the commercial nonlinear finite element software. Through these simulations, the flatness and appearance of wrinkles were analyzed by modeling the behavior and distribution of stresses and strains in the processing process. The application of vibration to the mandrel appears to be a promising approach for controlling the wrinkling and flattening problems during pipe processing.

Theoretical, Numerical and Experimental Investigation of the Effects of Manufacturing Process Parameters on Thin-Walled Tube Bending Defects

2009 ◽  
Vol 83-86 ◽  
pp. 1107-1112
Author(s):  
J. Taheri Kahnamouei ◽  
Mohammad Sedighi
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Thickness Ratio ◽  
Outer Diameter ◽  
Tube Bending ◽  
Effective Parameters ◽  
Bending Process ◽  
Thin Walled Tube ◽  
Bending Radius ◽  
Thin Walled

The aim of this paper is to survey thin-walled tube bending process (without use of mandrel and booster). In tube bending process there are several effective parameters such as wall thickness, outer diameter-to-wall thickness ratio, and centerline bending radius-to-outer diameter ratio. Any mismatch in selecting these parameters would cause defects like wrinkling, variation in wall thickness, and cross section distortion. Firstly, the effects of these parameters on the initiation of the wrinkle, depth of wrinkling, change in wall thickness, and cross section distortion are studied. For this purpose, an FE commercial code has been used to simulate the process. Then, a series of experimental tests have been carried out to verify the results simulation. A comparison between analytical and experimental results shows a reasonable agreement with each other. Based on this comparison, it has been observed that there is a critical bending radius for any tube with a certain radius and thickness, in which the wrinkling begins to occur. For a certain bending angle and radius, it have been observed that the depth of wrinkling, change in wall thickness, and cross section distortion increase with reduction in wall thickness and outer diameter-to-wall thickness ratio

Modeling and Experimental Validation of the Effect of Sand Filling on Avoiding Wrinkling Phenomenon in Thin-Walled Tube Bending Process

2010 ◽  
Author(s):  
Jalal Taheri Kahnamouei ◽  
Bashir Behjat
Keyword(s):  
Wall Thickness ◽  
Experimental Tests ◽  
Element Model ◽  
Thickness Ratio ◽  
Outer Diameter ◽  
Tube Bending ◽  
Effective Parameters ◽  
Bending Process ◽  
Bending Radius ◽  
Thin Walled

This paper investigates a method to avoid the wrinkling in thin-walled tubes in bending process. In the tube bending process there are several effective parameters such as wall thickness, outer diameter-to-wall thickness ratio, centerline bending radius-to-outer diameter ratio. Any mismatch in the selection of the process parameters would cause defects like wrinkling, serve changes in wall thickness, and cross section distortion. For example, the depth of wrinkling increases with reduction in wall thickness and outer diameter-to-wall thickness ratio for a certain bending angle and radius. In this research, to avoid wrinkle initiation, tube is filled by sand and then bended. This sandy core is supported the tube from inner, and tube is prepared to bending. After bending process, sand is removed. In this work, to study the process numerically, a 3D finite element model of the horizontal bending process is built using ANSYS software. Then, experimental tests have been carried out to verify the simulation results and are developed to provide additional insight. A comparison between numerical and experimental results shows a reasonable agreement. It shows that wrinkle initiation can be avoided with filler material like sand.

Wrinkling Limit in Tube Bending

2000 ◽  
Vol 123 (4) ◽  
pp. 430-435 ◽  
Author(s):  
Xi Wang ◽  
Jian Cao
Keyword(s):  
Material Properties ◽  
Deformation Theory ◽  
Energy Approach ◽  
Tube Bending ◽  
Predictive Tool ◽  
Bending Process ◽  
Thin Walled Tube ◽  
Bending Radius ◽  
Thin Walled ◽  
Doubly Curved

Thin-walled tube bending has found many of its applications in the automobile and aerospace industries. This paper presents an energy approach to provide the minimum bending radius, which does not yield wrinkling in the bending process, as a function of tube and tooling geometry and material properties. A doubly-curved sheet model is established following the deformation theory. This approach provides a predictive tool in designing/optimizing the tooling parameters in tube bending.

Wrinkling Limit in Tube Bending

2000 ◽  
Author(s):  
Xi Wang ◽  
Jian Cao
Keyword(s):  
Material Properties ◽  
Deformation Theory ◽  
Energy Approach ◽  
Tube Bending ◽  
Predictive Tool ◽  
Bending Process ◽  
Thin Walled Tube ◽  
Bending Radius ◽  
Thin Walled ◽  
Doubly Curved

Abstract Thin-walled tube bending has found many of its applications in the automobile and aerospace industries. This paper presents an energy approach to provide the minimum bending radius, which does not yield wrinkling in the bending process, as a function of tube and tooling geometry and material properties. A doubly-curved sheet model is established following the deformation theory. This approach provides a predictive tool in designing/optimizing the tooling parameters in the tube bending.

Experimental Study on Residual Cross-Sectional Flattening of Thin-Walled Pipes Under Pure Plastic Bending

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Ziqian Zhang
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Residual Deformation ◽  
Outer Diameter ◽  
Cross Sectional ◽  
Plastic Bending ◽  
Thin Walled Pipe ◽  
Bending Radius ◽  
Thin Walled ◽  
The Cross

Abstract Cross-sectional ovalization (ovalization) usually occurs when thin-walled pipe is subjected to large plastic bending. This paper is concerned with residual deformation of thin-walled pipe's cross section in a radial direction when external bending moment is removed. In order to clarify the fundamental ovalization characteristics, find out what factors influence the residual flattening (value of ovalization), the ovalization behavior is investigated experimentally. The experiments are carried out on 21 stainless steel specimens with different geometric parameters under different bending radii by means of a four-point pure bending device. The residual cross-sectional flattenings are monitored continuously by scanning the cross section periodically along the circumferential direction. From the experimental results, it is observed that the cross-sectional shape of the thin-walled pipe is not perfect standard ellipse, and the appearance of the maximum residual flattening is usually found in the direction normal to the neutral surface. It is also revealed the relationships between the residual flattening and the bending radius, the wall thickness, and the pipe outer diameter, i.e., the residual flattening increases as the bending radius and the wall thickness reduce, but it increases as the outer diameter increases. These results are expected to find their potential application in thin-walled pipe bending operation.

scholarly journals Development and Modelling of the Method of Mandrelless Small-Radius Tube Bending / Opracowanie I Modelowanie Sposobu Beztrzpieniowego Gięcia Rur Na Małych Promieniach

2015 ◽  
Vol 60 (4) ◽  
pp. 2797-2804 ◽  
Author(s):  
J. Michalczyk ◽  
K. Wojsyk
Keyword(s):  
Numerical Modelling ◽  
Cross Section ◽  
Small Radius ◽  
Outer Diameter ◽  
Actual Process ◽  
Tube Bending ◽  
Tube Cross Section ◽  
Wall Thinning ◽  
Bending Process ◽  
Bending Radius

The paper reports the results of research aimed at creating theoretical grounds for a new method of mandrelless small-radius tube bending (1.5Dr<Rg<2.5Dr, where Dr- tube diameter, Rg- bending radius). As the result of applying such a methodology it is possible to carry out the bending process (with an angle of up to 180°) and obtain an ovalization and wall thinning in the bending area, which are much smaller than those in currently manufactured products. The currently used bending methods and bending equipment are able to achieve a minimum bending radius not less than three times the tube outer diameter. The research hypothesis has assumed the existence of tube bending methods that are more efficient that those known so far. Than methods do not rely on circular bending contours, but instead they may use other shaping die contours which has not been explored yet. Circular benders used in practice fail in that they do not yield the expected results on small radii and do not control the material flow (do not ensure its correct behaviour) in the bending zone. The literature review has shown that there are currently no theoretical studies, numerical analyses and experimental verifications related to the processes of mandrelless tube bending on small radii, i.e. for 1.5D≤R≥2.5D, where: (R - bending radius, D - tube outer diameter) up to an angle of 180°. Due to the lack of studies on this subject, in their approach to the numerical modelling of the problem, the authors of the paper were guided by their own experience in this field and made every effort to make the numerical model reflect the actual process as accurately as possible. They were only aided by the general knowledge accumulated in the literature on numerical modelling. To sum up, the purpose of the publication is to demonstrate that the change in the die recess towards a shape resembling an ellipse results in a change in the characteristics of metal flow (movement) along the tube perimeter and in a change in the stress characteristics and, as a consequence, a change in the tube cross-section in the bending zone. The research discussed in this paper seeks to establish the correct flow of material in the tube cross-section in the bending zone by determining the most efficient bender recess shape and friction surface forming, which will eliminate the excessive ovalization and upper wall thinning. The expected effect of implementing this bending technology will be increasing the flow capacity in energy systems, which will directly translate into a reduction of atmospheric CO emissions due to the lower energy consumption. In addition, the paper has presented the concepts of tools intended for the experimental verification of tube bending process.

Research on the Die Fittingness and Springback of Large Diameter Thin-Walled CT20 Titanium Alloy Tube NC Bending

2012 ◽  
Vol 472-475 ◽  
pp. 997-1002 ◽  
Author(s):  
Jian Guang Wang ◽  
Mei Zhan ◽  
Tao Huang ◽  
He Yang
Keyword(s):  
Titanium Alloy ◽  
Compressive Stress ◽  
Large Diameter ◽  
Alloy Tube ◽  
Bending Process ◽  
Bending Radius ◽  
Thin Walled ◽  
Titanium Alloy Tube ◽  
Assembly Precision ◽  
Nc Bending

The significant die unfittingness and springback, occuring during the numerically controlled (NC) bending process of large diameter thin-walled CT20 titanium alloy tube, has an obvious influence on the shape and the geometrical precision of the bent tube, furthermore on the assembly precision and the sealing capability. The changing rules of die fittingness and springback of large diameter thin-walled CT20 titanium alloy tube under different bending parameters were investigated and the mechanism was analysed using finite element method (FEM) in this paper. The result shows that the springback of large diameter thin-walled CT20 titanium alloy tube is more significant than that of aluminum alloy and stainless steel tubes with the same specification. The die fittingness has a connection with the tangent compressive stress on the intrados of the tube before springback, the larger the tangent compressive stress, the worse is the die fittingness.The results may provide a significant guide to the control of bending radius and bending angle for large diameter thin-walled titanium alloy tube NC bending.

Research on springback characteristic in flexible multi-points 3D stretch-bending process

2021 ◽  
pp. 095440542110284
Author(s):  
Song Gao ◽  
Tonggui He ◽  
Qihan Li ◽  
Yingli Sun ◽  
Jicai Liang
Keyword(s):  
Simulation Model ◽  
High Efficiency ◽  
Vertical Direction ◽  
Factors Affecting ◽  
Stretch Bending ◽  
Element Simulation ◽  
Bending Process ◽  
Bending Radius ◽  
Aluminum Profiles ◽  
Bending Sequence

The problem of springback is one of the most significant factors affecting the forming accuracy for aluminum 3D stretch-bending parts. In order to achieve high-efficiency and high-quality forming of such kind of structural components, the springback behaviors of the AA6082 aluminum profiles are investigated based on the flexible multi-points 3D stretch-bending process (3D FSB). Firstly, a finite element simulation model for the 3D FSB process was developed to analyze the forming procedure and the springback procedure. The forming experiments were carried out for the rectangle-section profile to verify the effectiveness of the simulation model. Secondly, the influence of tension on springback was studied, which include the pre-stretching and the post-stretching. Furthermore, the influences of the bending radius and bending sequence are revealed. The results show that: (1) The numerical model can be used to evaluate the effects of bending radius and process parameters on springback in the 3D FSB process effectively. (2) The pre-stretching has little effect on the horizontal springback reduction, but it plays a prominent role in reducing the springback in the vertical direction. (3) The increase of bending deformation in any direction will lead to an increase of springback in its direction and reduce the springback in the other direction. Besides, it reduces the relative error in both directions simultaneously. This research established a foundation to achieve the precise forming of the 3D stretch-bending parts with closed symmetrical cross-section.

scholarly journals Optimal Design of the Shape of a Non-Ball Mandrel for Thin-Walled Tube Small Radius Cold Bending

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1221
Author(s):  
Lu Bai ◽  
Jun Liu ◽  
Ziang Wang ◽  
Shuanggui Zou
Keyword(s):  
Ideal Point ◽  
Small Radius ◽  
Grey Wolf Optimizer ◽  
Forming Quality ◽  
Hollow Section ◽  
Cold Bending ◽  
Bending Process ◽  
Before And After ◽  
Thin Walled Tube ◽  
Thin Walled

In the field of cold bending, it is necessary to use ball mandrels, especially to bend thin-walled tubes with a small radius. However, the bending process with a ball mandrel is complex and expensive, and it is easy to jam the core ball inside the tube. To solve these issues, we designed two kinds of hollow non-ball mandrel schemes with low stiffness that were suitable for the small radius bending of thin-walled tubes. We evaluated the forming quality of cold bending numerically and the influence of the hollow section length and thickness on the forming indices. Our results showed that the thickness of the hollow section has a greater influence on forming quality than the length. As the hollow section’s thickness increased, the wrinkling rate first declined by approximately 40% and then increased by above 50%. When the thickness was 11 mm in scheme 1 and 13 mm in scheme 2, the wrinkling rate reached minimum values of 1.32% and 1.50%, respectively. As the hollow section’s thickness increased, the flattening rate decreased by more than 60% and the thinning rate increased by about 40%. A multi-objective optimization of forming indices was carried out by ideal point method and grey wolf optimizer. By comparing the forming results before and after optimization, the feasibility of using the proposed hollow mandrel was proved, and the hollow mandrel scheme of standard cylinder is therefore recommended.

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