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8 pages, 185 KiB

Open AccessEditorial

Latest Hydroforming Technology of Metallic Tubes and Sheets

by Yeong-Maw Hwang and Ken-Ichi Manabe

Metals 2021, 11(9), 1360; https://0-doi-org.brum.beds.ac.uk/10.3390/met11091360 - 30 Aug 2021

Cited by 17 | Viewed by 2404

Abstract

Hydroforming processes of metal tubes and sheets are being widely applied in manufacturing because of the increasing demand for lightweight parts in sectors such as the automobile, aerospace, and ship-building industries [...] Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

Research

Jump to: Editorial

18 pages, 9098 KiB

Open AccessArticle

Warm Hydroforming Process under Non-Uniform Temperature Field for Magnesium Alloy Tubes

by Toshiji Morishima and Ken-Ichi Manabe

Metals 2021, 11(6), 901; https://0-doi-org.brum.beds.ac.uk/10.3390/met11060901 - 31 May 2021

Cited by 3 | Viewed by 2167

Abstract

The warm tube hydroforming (WTHF) process of lightweight materials such as magnesium alloy contributes to a remarkable weight reduction. The success of the WTHF process strongly depends on the loading path with internal pressure and axial feeding and other process variables including temperature [...] Read more.

The warm tube hydroforming (WTHF) process of lightweight materials such as magnesium alloy contributes to a remarkable weight reduction. The success of the WTHF process strongly depends on the loading path with internal pressure and axial feeding and other process variables including temperature distribution. Optimization of these process parameters in this special forming technique is a great issue to be resolved. In this study, the optimization of the symmetrical temperature distribution and process loading path for the warm T-shape forming of magnesium alloy AZ31B tube was carried out by finite element (FE) analysis using a fuzzy model. As a result, a satisfactory good agreement of the wall thickness distribution of the samples formed under the optimum loading path condition can be obtained between the FE analysis result and the experimental result. Based on the validity validation of FE analysis model, the optimization method was applied to other materials and forming shapes, and applicability was discussed. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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10 pages, 737 KiB

Open AccessArticle

Description of the Expansion of a Two-Layer Tube: An Analytic Plane-Strain Solution for Arbitrary Pressure-Independent Yield Criterion and Hardening Law

by Sergei Alexandrov, Elena Lyamina and Lihui Lang

Metals 2021, 11(5), 793; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050793 - 14 May 2021

Cited by 6 | Viewed by 1548

Abstract

The main objective of the present paper is to provide a simple analytical solution for describing the expansion of a two-layer tube under plane-strain conditions for its subsequent use in the preliminary design of hydroforming processes. Each layer’s constitutive equations are an arbitrary [...] Read more.

The main objective of the present paper is to provide a simple analytical solution for describing the expansion of a two-layer tube under plane-strain conditions for its subsequent use in the preliminary design of hydroforming processes. Each layer’s constitutive equations are an arbitrary pressure-independent yield criterion, its associated plastic flow rule, and an arbitrary hardening law. The elastic portion of strain is neglected. The method of solution is based on two transformations of space variables. Firstly, a Lagrangian coordinate is introduced instead of the Eulerian radial coordinate. Then, the Lagrangian coordinate is replaced with the equivalent strain. The solution reduces to ordinary integrals that, in general, should be evaluated numerically. However, for two hardening laws of practical importance, these integrals are expressed in terms of special functions. Three geometric parameters for the initial configuration, a constitutive parameter, and two arbitrary functions classify the boundary value problem. Therefore, a detailed parametric analysis of the solution is not feasible. The illustrative example demonstrates the effect of the outer layer’s thickness on the pressure applied to the inner radius of the tube. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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15 pages, 10689 KiB

Open AccessArticle

Local One-Sided Rubber Bulging Test to Measure Various Strain Paths of Metal Tube

by Hidenori Yoshimura, Kana Nakahara and Masaaki Otsu

Metals 2021, 11(5), 751; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050751 - 2 May 2021

Cited by 3 | Viewed by 2650

Abstract

We proposed a local one-sided rubber bulging method of metal tubes to evaluate various strain paths at an aimed portion and measured the forming limit strains of metal tubes at the place of the occurrence of necking under biaxial deformation. Using this method, [...] Read more.

We proposed a local one-sided rubber bulging method of metal tubes to evaluate various strain paths at an aimed portion and measured the forming limit strains of metal tubes at the place of the occurrence of necking under biaxial deformation. Using this method, since rubber is used to give pressure from the inner side of the tube, no sealing mechanisms were necessary unlike during hydraulic pressure bulging. An opening was prepared in front of the die to locally bulge a tube at only the evaluation portion. To change the restriction conditions of the bulged region for biaxial deformation at the opening, a round or square cutout, or a slit was introduced. The test was conducted using a universal compression test machine and simple dies rather than a dedicated machine. Considering the experimental results, it was confirmed that the strain path was varied by changing the position and size of slits and cutouts. Using either a cutout or a slit, the strain path in the side of the metal tubes can be either equi-biaxial tension or simple tension, respectively. Additionally, by changing the size of the cuts or slits, the strain path can be varied. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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18 pages, 9132 KiB

Open AccessArticle

Investigation of Punch Shape and Loading Path Design in Hydro-Flanging Processes of Aluminum Alloy Tubes

by Yeong-Maw Hwang, Hong-Nhan Pham and Hiu-Shan Rachel Tsui

Metals 2021, 11(4), 636; https://0-doi-org.brum.beds.ac.uk/10.3390/met11040636 - 13 Apr 2021

Cited by 8 | Viewed by 2232

Abstract

Hydro-joining is composed of hydro-piercing, hole flanging and nut-inlaying processes. In this study, a new hydro-flanging process combining hydro-piercing and hydro-flanging is proposed. An internal pressured fluid is used as the supporting medium instead of a rigid die. Three kinds of punch head [...] Read more.

Hydro-joining is composed of hydro-piercing, hole flanging and nut-inlaying processes. In this study, a new hydro-flanging process combining hydro-piercing and hydro-flanging is proposed. An internal pressured fluid is used as the supporting medium instead of a rigid die. Three kinds of punch head shapes are designed to explore the thickness distribution of the flanged tube and the fluid leakage effects between the punch head and the flanged tube in the hydro-flanging process. A finite element code DEFORM 3D is used to simulate the tube material deformation behavior and to investigate the formability of the hydro-flanging processes of aluminum alloy tubes. The effects of various forming parameters, such as punch shapes, internal pressure, die hole diameter, etc., on the hydro-flanged tube thickness distributions are discussed. Hydro-flanging experiments are also carried out. The die hole radius is designed to make the maximum internal forming pressure needed smaller than 70 MPa, so that a general hydraulic power unit can be used to implement the proposed hole flanging experiments. The flanged thickness distributions are compared with simulation results to verify the validity of the proposed models and the designed punch head shapes. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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15 pages, 7314 KiB

Open AccessArticle

Tube Drawing Process with Diameter Expansion for Effectively Reducing Thickness

by Shohei Kajikawa, Hikaru Kawaguchi, Takashi Kuboki, Isamu Akasaka, Yuzo Terashita and Masayoshi Akiyama

Metals 2020, 10(12), 1642; https://0-doi-org.brum.beds.ac.uk/10.3390/met10121642 - 6 Dec 2020

Cited by 7 | Viewed by 6401

Abstract

The present paper describes a tube drawing method with diameter expansion, which is herein referred to as “expansion drawing”, for effectively producing thin-walled tube. In the proposed method, the tube end is flared by pushing a plug into the tube, and the tube [...] Read more.

The present paper describes a tube drawing method with diameter expansion, which is herein referred to as “expansion drawing”, for effectively producing thin-walled tube. In the proposed method, the tube end is flared by pushing a plug into the tube, and the tube is then expanded by drawing the plug in the axial direction while the flared end is chucked. The forming characteristics and effectiveness of the proposed method were investigated through a series of finite element method (FEM) analyses and experiments. As a result of FEM analysis, the expansion drawing effectively reduced the tube thickness with a smaller axial load when compared with the conventional method. According to the experimental results, the thin-walled tube was produced successfully by the expansion drawing. Maximum thickness reduction ratios for a carbon steel (STKM13C) and an aluminum alloy (AA1070) were 0.15 and 0.29 when the maximum expansion ratios were 0.23 and 0.31, respectively. The above results suggest that the proposed expansion drawing method is effective for producing thin-walled tubes. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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17 pages, 7996 KiB

Open AccessArticle

Pneumatic Experimental Design for Strain Rate Sensitive Forming Limit Evaluation of 7075 Aluminum Alloy Sheets under Biaxial Stretching Modes at Elevated Temperature

by Jong-Hwa Hong, Donghoon Yoo, Yong Nam Kwon and Daeyong Kim

Metals 2020, 10(12), 1639; https://0-doi-org.brum.beds.ac.uk/10.3390/met10121639 - 5 Dec 2020

Cited by 5 | Viewed by 2038

Abstract

A pneumatic experimental design to evaluate strain rate sensitive biaxial stretching forming limits for 7075 aluminum alloy sheets was attempted with the finite element method. It was composed of apparatus geometric design with pressure optimization as the process design. The 7075 aluminum alloy [...] Read more.

A pneumatic experimental design to evaluate strain rate sensitive biaxial stretching forming limits for 7075 aluminum alloy sheets was attempted with the finite element method. It was composed of apparatus geometric design with pressure optimization as the process design. The 7075 aluminum alloy material was characterized by conventional Voce-type hardening law with power law strain rate sensitivity relationship. For optimization of the die shape design, the ratio of minor to major die radius (k) and profile radius (R) were parametrically studied. The final shape of die was determined by how the history of targeted deformation mode was well maintained and whether the fracture was induced at the pole (specimen center), thereby preventing unexpected failure at other locations. As a result, a circular die with k = 1.0 and an elliptic die with k = 0.25 were selected for the balanced biaxial mode and near plane strain mode, respectively. Lastly, the pressure inducing fracture at the targeted strain rate was studied as the process design. An analytical solution that had been previously studied to maintain constant strain rate was properly modified for the designed model. The results of the integrated design were compared with real experimental results. The shape and thickness distribution of numerical simulation showed good agreement with those of the experiment. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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13 pages, 10181 KiB

Open AccessArticle

Ball Spin Forming for Flexible and Partial Diameter Reduction in Tubes

by Shota Hirama, Takayuki Ikeda, Shiori Gondo, Shohei Kajikawa and Takashi Kuboki

Metals 2020, 10(12), 1627; https://0-doi-org.brum.beds.ac.uk/10.3390/met10121627 - 4 Dec 2020

Cited by 3 | Viewed by 2367

Abstract

This paper proposed a new ball spin forming equipment, which can form a reduced diameter section on the halfway point of a tube. The effects of forming process parameters on the surface integrity and deformation characteristics of the product were investigated. The proposed [...] Read more.

This paper proposed a new ball spin forming equipment, which can form a reduced diameter section on the halfway point of a tube. The effects of forming process parameters on the surface integrity and deformation characteristics of the product were investigated. The proposed method can reduce the diameter in the middle portion of the tube, and the maximum diameter reduction ratio was over 10% in one pass. When the feed pitch of the ball die was more than 2.0 mm/rev, spiral marks remained on the surface of tube. Torsional deformation, axial elongation and an increase in thickness appeared in the tube during the forming process. All of them were affected by the feed pitch and feed direction of the ball die, while they were not affected by the rotation speed of the tube. By sending the ball die towards the fixed part of the tube or by increasing the feed pitch, torsional deformation and elongation decreased, and the amount of thickening increased. When the tube was pressed perpendicularly to the axis without axial feed, a diameter reduction ratio of 21.1% was achieved without defects using a ball diameter of 15.9 mm. The polygonization of the tube was suppressed by reducing the pushing pitch. The ball spin forming has a high advantage in flexible diameter reduction processing on the halfway point of the tube for producing different diameter tubes. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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16 pages, 5280 KiB

Open AccessArticle

Movable Die and Loading Path Design in Tube Hydroforming of Irregular Bellows

by Yeong-Maw Hwang and Yau-Jiun Tsai

Metals 2020, 10(11), 1518; https://0-doi-org.brum.beds.ac.uk/10.3390/met10111518 - 16 Nov 2020

Cited by 10 | Viewed by 2860

Abstract

Manufacturing of irregular bellows with small corner radii and sharp angles is a challenge in tube hydroforming processes. Design of movable dies with an appropriate loading path is an alternative solution to obtain products with required geometrical and dimensional specifications. In this paper, [...] Read more.

Manufacturing of irregular bellows with small corner radii and sharp angles is a challenge in tube hydroforming processes. Design of movable dies with an appropriate loading path is an alternative solution to obtain products with required geometrical and dimensional specifications. In this paper, a tube hydroforming process using a novel movable die design is developed to decrease the internal pressure and the maximal thinning ratio in the formed product. Two kinds of feeding types are proposed to make the maximal thinning ratio in the formed bellows as small as possible. A finite element simulation software “DEFORM 3D” is used to analyze the plastic deformation of the tube within the die cavity using the proposed movable die design. Forming windows for sound products using different feeding types are also investigated. Finally, tube hydroforming experiments of irregular bellows are conducted and experimental thickness distributions of the products are compared with the simulation results to validate the analytical modeling with the proposed movable die concept. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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14 pages, 4413 KiB

Open AccessArticle

Investigation of Effects of Strip Metals and Relative Sliding Speeds on Friction Coefficients by Reversible Strip Friction Tests

by Yeong-Maw Hwang and Chiao-Chou Chen

Metals 2020, 10(10), 1369; https://0-doi-org.brum.beds.ac.uk/10.3390/met10101369 - 14 Oct 2020

Cited by 5 | Viewed by 2009

Abstract

Friction at the interface between strips and dies is an important factor influencing the formability of strip or sheet forming. In this study, the frictional behaviors of strips at variant speeds were investigated using a self-developed strip friction test machine with a dual [...] Read more.

Friction at the interface between strips and dies is an important factor influencing the formability of strip or sheet forming. In this study, the frictional behaviors of strips at variant speeds were investigated using a self-developed strip friction test machine with a dual tension mechanism. This friction test machine, stretching a strip around a cylindrical friction wheel, was used to investigate the effects of various parameters, including sliding speeds, contact angles, strip materials, and lubrication conditions on friction coefficients at the strip–die interface. The friction coefficients at the strip–die interface were calculated from the drawing forces at the strip on both ends and the contact angle between the strip and die. A series of friction tests using carbon steel, aluminum alloy, and brass strips as the test piece were conducted. From the friction test results, it is known that the friction coefficients can be reduced greatly with lubricants on the friction wheel surface and the friction coefficients are influenced by the strip roughness, contact area, relative speeds between the strip and die, etc. The friction coefficients obtained under various friction conditions can be applied to servo deep drawing or servo draw-bending processes with variant speeds and directions. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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16 pages, 40823 KiB

Open AccessArticle

Crash Characteristics of Partially Quenched Curved Products by Three-Dimensional Hot Bending and Direct Quench

by Atsushi Tomizawa, Sanny Soedjatmiko Hartanto, Kazuo Uematsu and Naoaki Shimada

Metals 2020, 10(10), 1322; https://0-doi-org.brum.beds.ac.uk/10.3390/met10101322 - 2 Oct 2020

Cited by 7 | Viewed by 1701

Abstract

Recently, improvement of hybrid and electric vehicle technologies, equipped with batteries, continues to solve energy and environmental problems. Lighter weight and crash safety are required in these vehicles body. In order to meet these requirements, three-dimensional hot bending and direct quench (3DQ) technology, [...] Read more.

Recently, improvement of hybrid and electric vehicle technologies, equipped with batteries, continues to solve energy and environmental problems. Lighter weight and crash safety are required in these vehicles body. In order to meet these requirements, three-dimensional hot bending and direct quench (3DQ) technology, which enables to form hollow tubular automotive parts with a tensile strength of 1470 MPa or over, has been developed. In addition, this technology enables to produce partially quenched automotive parts. In this study, the crash characteristics of 3DQ partially quenched products were investigated as the fundamental research of the design for improving the energy absorption. Main results are as follows: (1) for partially quenched straight products in axial crash test, buckling that occurs at nonquenched portion can be controlled; (2) for the nonquenched conventional and overall-quenched curved products, buckling occurs at the bent portion at the initial stage in axial crash tests, and its energy absorption is low; (3) by optimizing partially quench conditions, buckling occurrence can be controlled; and (4) In this study, the largest energy absorption was obtained from the partially quenched curved product, which was 84.6% larger than the energy absorption of the conventional nonquenched bent product in crash test. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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11 pages, 4391 KiB

Open AccessArticle

Conductive Heating during Press Hardening by Hot Metal Gas Forming for Curved Complex Part Geometries

by Mirko Bach, Lars Degenkolb, Franz Reuther, Verena Psyk, Rico Demuth and Markus Werner

Metals 2020, 10(8), 1104; https://0-doi-org.brum.beds.ac.uk/10.3390/met10081104 - 17 Aug 2020

Cited by 13 | Viewed by 3140

Abstract

Climate targets set by the EU, including the reduction of CO₂, are leading to the increased use of lightweight materials for mass production such as press hardening steels. Besides sheet metal forming for high-strength components, tubular or profile forming (Hot Metal [...] Read more.

Climate targets set by the EU, including the reduction of CO₂, are leading to the increased use of lightweight materials for mass production such as press hardening steels. Besides sheet metal forming for high-strength components, tubular or profile forming (Hot Metal Gas Forming—HMGF) allows for designs that are more complex in combination with a lower weight. This paper particularly examines the application of conductive heating of the component for the combined press hardening process. The previous Finite-Element-Method (FEM)-supported design of an industry-oriented, curved component geometry allows the development of forming tools and process peripherals with a high degree of reliability. This work comprises a description regarding the functionality of the tools and the heating strategy for the curved component as well as the measurement technology used to investigate the heat distribution in the component during the conduction process. Subsequently, forming tests are carried out, material characterization is performed by hardness measurements in relevant areas of the component, and the FEM simulation is validated by comparing the resulting sheet thickness distribution to the experimental one. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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16 pages, 9167 KiB

Open AccessArticle

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

by Kunito Nakajima, Noah Utsumi, Yoshihisa Saito and Masashi Yoshida

Metals 2020, 10(8), 1074; https://0-doi-org.brum.beds.ac.uk/10.3390/met10081074 - 10 Aug 2020

Cited by 9 | Viewed by 4335

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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15 pages, 9960 KiB

Open AccessArticle

Circumferential Material Flow in the Hydroforming of Overlapping Blanks

by Cong Han and Hao Feng

Metals 2020, 10(7), 864; https://0-doi-org.brum.beds.ac.uk/10.3390/met10070864 - 29 Jun 2020

Cited by 4 | Viewed by 2306

Abstract

The hydroforming of the overlapping blanks is a forming process where overlapping tubular blanks are used instead of tubes to enhance the forming limit and improve the thickness distribution. A distinguishing characteristic of the hydroforming of overlapping blanks is that the material can [...] Read more.

The hydroforming of the overlapping blanks is a forming process where overlapping tubular blanks are used instead of tubes to enhance the forming limit and improve the thickness distribution. A distinguishing characteristic of the hydroforming of overlapping blanks is that the material can flow along the circumferential direction easily. In this research, the circumferential material flow was investigated using overlapping blanks with axial constraints to study the circumferential material flow in the hydroforming of a variable-diameter part. AISI 304 stainless steel blanks were selected for numerical simulation and experimental research. The circumferential material flow distribution was obtained from the profile at the edge of the overlap. The peak value located at the middle cross-section. In addition, the circumferential material flow could be also reflected in the variation of the overlap angle. The variation of the overlap angle kept increasing as the initial overlap angle increased but the improvement of the thickness distribution did not. There was an optimal initial overlap angle to minimize the thinning ratio. An optimal thickness distribution was obtained when the initial angle was 120° for the hydroforming of the variable-diameter part with an expansion of 31.6%. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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15 pages, 3579 KiB

Open AccessArticle

Oblique/Curved Tube Necking Formed by Synchronous Multipass Spinning

by Hirohiko Arai and Shiori Gondo

Metals 2020, 10(6), 733; https://0-doi-org.brum.beds.ac.uk/10.3390/met10060733 - 2 Jun 2020

Cited by 5 | Viewed by 2494

Abstract

In this paper, we propose a method of forming a tube into an oblique/curved shape by synchronous multipass spinning, in which the forming roller reciprocates in the radial direction in synchrony with the rotation angle of the spindle while the roller moves back [...] Read more.

In this paper, we propose a method of forming a tube into an oblique/curved shape by synchronous multipass spinning, in which the forming roller reciprocates in the radial direction in synchrony with the rotation angle of the spindle while the roller moves back and forth along the workpiece in the axial direction to gradually deform a blank tube into a target shape. The target oblique/curved shape is expressed as a series of inclined circular cross sections. The contact position of the roller and the workpiece is calculated from the inclination angle, center coordinates, and diameter of the cross sections, considering the geometrical shape of the roller. The blank shape and the target shape are interpolated along normalized tool paths to generate the numerical control command of the roller. By this method, we experimentally formed aluminum tubes into curved shapes with various radii of curvature, and the forming accuracy, thickness distribution, and strain distribution are examined. We verified that the curved shapes with the target radii of curvature can be accurately realized. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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23 pages, 10461 KiB

Open AccessArticle

A Vision-Based Fuzzy Control to Adjust Compression Speed for a Semi-Dieless Bellows-Forming

by Sugeng Supriadi, Tsuyoshi Furushima and Ken-ichi Manabe

Metals 2020, 10(6), 720; https://0-doi-org.brum.beds.ac.uk/10.3390/met10060720 - 28 May 2020

Cited by 1 | Viewed by 2647

Abstract

A novel semi-dieless bellows forming process with a local heating technique and axial compression has been initiated for the past years. However, this technique requires a high difficulty in maintaining the output quality due to its sensitivity to the processing conditions. The product [...] Read more.

A novel semi-dieless bellows forming process with a local heating technique and axial compression has been initiated for the past years. However, this technique requires a high difficulty in maintaining the output quality due to its sensitivity to the processing conditions. The product quality mainly depends on not only the temperature distribution in the radial and axial direction but also the compression ratio during the semi-dieless bellows process. A finite element model has clarified that a variety of temperature produced by unstable heating or cooling will promote an unstable bellows formation. An adjustment to the compression speed is adequate to compensate for the effect of the variety of temperatures in the bellows formation. Therefore, it is necessary to apply a real-time process for this process to obtain accurate and precise bellows. In this paper, we are proposing a vision-based fuzzy control to control bellows formation. Since semi-dieless bellows forming is an unsteady and complex deformation process, the application of image processing technology is suitable for sensing the process because of the possible wide analysis area afforded by applying the multi-sectional measuring. A vision sensing algorithm is developed to monitor the bellows height from the captured images. An adaptive fuzzy has been verified to control bellows formation from 5 mm stainless steel tube in to bellows profile up to 7 mm bellows height, processing speed up to 0.66 mm/s. The adaptive fuzzy control system is capable of appropriately adjusting the compression speed by evaluating the bellows formation progress. Appropriate compression speed paths guide bellows formation following deformation references. The results show that the bellows shape accuracy between target and experiment increase become 99.5% under given processing ranges. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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17 pages, 12620 KiB

Open AccessArticle

Influence of Internal Pressure and Axial Compressive Displacement on the Formability of Small-Diameter ZM21 Magnesium Alloy Tubes in Warm Tube Hydroforming

by Hajime Yasui, Taisuke Miyagawa, Shoichiro Yoshihara, Tsuyoshi Furushima, Ryuichi Yamada and Yasumi Ito

Metals 2020, 10(5), 674; https://0-doi-org.brum.beds.ac.uk/10.3390/met10050674 - 21 May 2020

Cited by 6 | Viewed by 2953

Abstract

In this study, the influence of internal pressure and axial compressive displacement on the formability of small-diameter ZM21 magnesium alloy tubes in warm tube hydroforming (THF) was examined experimentally and numerically. The deformation behavior of ZM21 tubes, with a 2.0 mm outer diameter [...] Read more.

In this study, the influence of internal pressure and axial compressive displacement on the formability of small-diameter ZM21 magnesium alloy tubes in warm tube hydroforming (THF) was examined experimentally and numerically. The deformation behavior of ZM21 tubes, with a 2.0 mm outer diameter and 0.2 mm wall thickness, was evaluated in taper-cavity and cylinder-cavity dies. The simulation code used was the dynamic explicit finite element (FE) method (FEM) code, LS-DYNA 3D. The experiments were conducted at 250 °C. This paper elucidated the deformation characteristics, forming defects and forming limit of ZM21 tubes. Their deformation behavior in the taper-cavity die was affected by the axial compressive direction. Additionally, the occurrence of tube buckling could be inferred by changes of the axial compression force, which were measured by the load cell during the processing. In addition, grain with twin boundaries and refined grain were observed at the bended areas of tapered tubes. The hydroformed samples could have a high strength. Moreover, wrinkles, which are caused under a lower internal pressure condition, were employed to avoid tube fractures during the axial feeding. The tube with wrinkles was expanded by a straightening process after the axial feed. It was found that the process of warm THF of the tubes in the cylinder-cavity die was successful. Full article

(This article belongs to the Special Issue Latest Hydroforming Technology of Metallic Tubes and Sheets)

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