Research

16 pages, 7555 KiB

Open AccessArticle

Die Design and Finite Element Analysis of Welding Seams during Aluminum Alloy Tube Extrusion

by Yeong-Maw Hwang and I-Peng Hsu

Metals 2023, 13(5), 911; https://doi.org/10.3390/met13050911 - 08 May 2023

Cited by 2 | Viewed by 1404

Hollow tubes are generally manufactured using porthole die extrusion. A finite element software QForm is used to analyze the material flow of aluminum alloy A6061 tubes inside a specially designed porthole die during tube extrusion. High welding pressure and shorter transverse seam length [...] Read more.

Hollow tubes are generally manufactured using porthole die extrusion. A finite element software QForm is used to analyze the material flow of aluminum alloy A6061 tubes inside a specially designed porthole die during tube extrusion. High welding pressure and shorter transverse seam length are required for a sound product. Various extrusion conditions and die geometries and dimensions affect the bonding strength of the products. In this paper, the effects of die geometries on the welding pressure are discussed using the Taguchi method. The simulation results show that a higher welding pressure is obtained with a larger porthole radius, a larger welding chamber height, and a larger bearing length, while a larger bridge width increases the welding pressure slightly. For transverse seam lengths, a shorter transverse seam length can be obtained with a smaller porthole radius and a smaller welding chamber height, and a shorter bridge width and bearing length decrease the transverse seam length slightly. The transverse seam region and flow patterns are observed. Tube expanding tests were also conducted. From the expanding test results, it is known that the fracture position did not occur at the welding line and the bonding strength could reach up to 160 MPa. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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25 pages, 13016 KiB

Open AccessArticle

Efficient Roll-Forming Simulation Using Non-Conformal Meshes with Hanging Nodes Handled by Lagrange Multipliers

by Cédric Laruelle, Romain Boman, Luc Papeleux and Jean-Philippe Ponthot

Metals 2023, 13(5), 895; https://doi.org/10.3390/met13050895 - 05 May 2023

Viewed by 1233

Abstract

Simulations of industrial roll-forming processes using the finite element method typically require an extremely fine discretization to obtain accurate results. Running those models using a classical finite element method usually leads to suboptimal meshes where some regions are unnecessarily over-refined. An alternative approach [...] Read more.

Simulations of industrial roll-forming processes using the finite element method typically require an extremely fine discretization to obtain accurate results. Running those models using a classical finite element method usually leads to suboptimal meshes where some regions are unnecessarily over-refined. An alternative approach consists in creating non-conformal meshes where a number of nodes, called hanging nodes, do not match the nodes of adjacent elements. Such flexibility allows for more freedom in mesh refinement, which results in the creation of more efficient simulations. Consequently, the computational cost of the models is decreased with little to no impact on the accuracy of the results. Handling the generated hanging nodes can, however, be challenging. In this work, details are first given about the implementation of these particular meshes in an implicit finite element code with a special focus on the treatment of hanging nodes using Lagrange Multipliers. Standard and non-conformal meshes are then compared to experimental measurements on the forming of a U-channel. A more complex roll-forming simulation—a tubular rocker panel—is then showcased as proof of the potential of the method for industrial uses. Our main results show that the proposed method effectively reduces the computational cost of the roll-forming simulations with a negligible impact on their accuracy. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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19 pages, 6606 KiB

Open AccessArticle

A New Bending Force Formula for the V-Die Bending Process

by Kongkiet Doungmarda and Sutasn Thipprakmas

Metals 2023, 13(3), 587; https://doi.org/10.3390/met13030587 - 13 Mar 2023

Cited by 1 | Viewed by 2707

Abstract

The V-die bending force is an important parameter in respect of press machine capacity selection, but it has not been the focus of previous research. Furthermore, while the various modified formulas proposed in previous research were calculated using V-die bending theory, they are [...] Read more.

The V-die bending force is an important parameter in respect of press machine capacity selection, but it has not been the focus of previous research. Furthermore, while the various modified formulas proposed in previous research were calculated using V-die bending theory, they are insufficient for predicting the actual V-die bending force. Based on the actual V-die bending mechanism, a new V-die bending force formula is proposed in this study, in which bending is generated not only in the bending allowance zone but also on the legs next to the bending allowance zone. Therefore, the bending force in these zones must be carefully considered. The finite element method (FEM) was used as an effective technique to clearly determine the actual V-die bending mechanism and to modify and develop a new V-die bending force formula. Laboratory experiments were carried out to validate the FEM simulation results as well as to confirm the accuracy of the proposed new V-die bending force formula. Two types of workpiece material, aluminum AA1100-O (JIS) and medium carbon-steel sheet-grade SPCC (JIS), were used as test materials. The results clearly show that the new V-die bending force formula offers more accuracy in V-die bending force prediction than predictions based on past formulas. The error in the V-die bending forces predicted using the new formula was approximately 5% compared with those of the experimental works. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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24 pages, 1507 KiB

Open AccessArticle

Utilizing Artificial Intelligence Approaches to Determine the Shear Strength of Steel Beams with Flat Webs

by Ahmed S. Elamary, Mohamed A. Mohamed, Ibrahim A. Sharaky, Abdou K. Mohamed, Yasir M. Alharthi and Mahrous A. M. Ali

Metals 2023, 13(2), 232; https://doi.org/10.3390/met13020232 - 26 Jan 2023

Cited by 1 | Viewed by 1367

Abstract

Steel beams’ shear strength is one of the most important factors that influence how quickly webs buckle. Despite extensive studies having been performed over the previous three decades, the existing procedures did not achieve the necessary reliability to predict the ultimate shear resistance [...] Read more.

Steel beams’ shear strength is one of the most important factors that influence how quickly webs buckle. Despite extensive studies having been performed over the previous three decades, the existing procedures did not achieve the necessary reliability to predict the ultimate shear resistance of plate girders. New techniques called Learner Techniques have started to be used over the last few years; these techniques were applied to calculate the steel beam shear strength. In this study, a Regression Learner Techniques model was built using data from 100 test results from previously published research. Based on the geometric and material properties of the web and flanges available in the published tests, a model was built using Artificial Neural Networks. Based on sensitivity analysis, a Cascade Forward Backpropagation Neural Networks (CFBNN) approach was utilized to anticipate the shear strength of steel beams. The proposed models outperformed current hybrid artificial intelligence models developed using the same collected datasets and demonstrated to accurately predict the ultimate shear strength. The performance of the models was evaluated using a range of statistical assessment methods, which led to a valuable conclusion. The CFBNN model achieved the highest root mean square (R² = 0.95). The results corresponding to each test were verified by specimen shear strength values calculated by a theoretical approach. The resultant maximum shear force obtained by the proposed modified equation was compared with the experimental results and the shear force was estimated using two different approaches proposed by the European code. Finally, two approaches were used to verify the proposed model. The first approach was the data reported from an experimental shear test program conducted by the authors, and the second was the results of the shear values acquired experimentally by other researchers. Based on the test results of the previous studies and the current work, the suggested model gives an adequate degree of accuracy for estimating the shear strength of steel beams. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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19 pages, 7023 KiB

Open AccessArticle

Experimental and Numerical Analysis of Prestrain on the Formability of Zn-Cu-Ti Alloy Zinc Sheet

by Emanuel A. Nicoletti, Analía Roatta, Luciano Ponzellini Marinelli, Javier W. Signorelli and Diego J. Celentano

Metals 2022, 12(7), 1095; https://doi.org/10.3390/met12071095 - 26 Jun 2022

Viewed by 1185

Abstract

The forming limit diagrams (FLDs) characterizing the formability of sheet metals are usually obtained by applying proportional loadings. Nevertheless, the industrial processes involve strain path changes that can modify the limit-strain values. In addition, for strongly anisotropic sheet metals such as the Zn-Cu-Ti [...] Read more.

The forming limit diagrams (FLDs) characterizing the formability of sheet metals are usually obtained by applying proportional loadings. Nevertheless, the industrial processes involve strain path changes that can modify the limit-strain values. In addition, for strongly anisotropic sheet metals such as the Zn-Cu-Ti zinc alloy, large differences in forming limit curves (FLCs) with respect to the sheet rolling direction are observed. In the present work, the analysis of the effect of bilinear strain paths on the FLC is addressed by both experimental measurements and numerical simulations. For this purpose, a miniature testing device was used that allows evaluation of the influence of strain path changes on the limit strain on samples at 0°, 45° and 90° with respect to the sheet rolling direction cut from non-standard large samples previously subjected to a prestrain along the RD up to an early deformation of ~0.12. Numerical simulations were carried out using the well-known Marciniak and Kuczynski (MK) theory in conjunction with the viscoplastic self-consistent (VPSC) crystal plasticity model. In order to account for the grain fragmentation process due to the continuous dynamic recrystallization (CDRX) mechanism, an ad hoc short-range interaction effect (SRE) model was included in the simulations. Additionally, the measured and simulated texture evolution of Zn-Cu-Ti alloy sheets at the different stages of the deformations were shown. The capacity of the MK-VPSC-SRE model was validated, and the limitations to simulating the texture development, flow stress and forming limit curves, including a non-proportional strain path, were discussed. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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13 pages, 2398 KiB

Open AccessFeature PaperArticle

Material and Damage Characterization of the Elastoplastic Response of the EK4 Deep Drawing Steel

by Carlos Barrera, Claudio García-Herrera, Diego J. Celentano and Javier W. Signorelli

Metals 2022, 12(5), 720; https://doi.org/10.3390/met12050720 - 23 Apr 2022

Cited by 3 | Viewed by 1532

Abstract

Although EK4 drawing steel is nowadays widely used to manufacture a great variety of parts, it exhibits a marked normal and planar anisotropy that can make it difficult to control the process during its forming. In order to achieve an accurate description of [...] Read more.

Although EK4 drawing steel is nowadays widely used to manufacture a great variety of parts, it exhibits a marked normal and planar anisotropy that can make it difficult to control the process during its forming. In order to achieve an accurate description of the elastoplastic material response in sheet forming operations, this work presents a detailed material and damage characterization of EK4 deep drawing steel through a two-step methodology involving both experiments and finite element simulations. Firstly, tensile tests on sheet samples cut along the rolling, diagonal and transverse directions were carried out. The corresponding measurements were used to calibrate the material parameters related to the following modeling approaches adopted in the present study: the Hollomon hardening law, the non-associated Hill-48 phenomenological constitutive model and the anisotropic Hosford-Coulomb ductile fracture criterion. Secondly, this characterization was assessed and validated in the numerical simulation of the technological Erichsen test in which the material is mainly subjected to a biaxial stress state. The obtained predictions show a good agreement when compared with the corresponding experimental measurements of the punch load–displacement curve and thickness radial profile at the final fracture stage of the sample. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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19 pages, 8290 KiB

Open AccessArticle

Evaluation on Flexibility of Phenomenological Hardening Law for Automotive Sheet Metals

by Quoc Tuan Pham and Young-Suk Kim

Metals 2022, 12(4), 578; https://doi.org/10.3390/met12040578 - 29 Mar 2022

Cited by 3 | Viewed by 2236

Abstract

Constitutive modeling of sheet metals involves building a system of equations governing the material behavior under multi-axial stress states. In general, these equations require a hardening law that describes the stress-strain relationship. This study provides a thorough examination of the existing phenomenological hardening [...] Read more.

Constitutive modeling of sheet metals involves building a system of equations governing the material behavior under multi-axial stress states. In general, these equations require a hardening law that describes the stress-strain relationship. This study provides a thorough examination of the existing phenomenological hardening laws in the literature. Based on their ordinary differential equations, special efforts were made to discuss the degree of flexibility of these hardening laws. Four new phenomenological hardening laws were proposed during the discussions to capture the stress-strain relationship of automotive sheet metals, such as aluminum alloy and steel sheets. Then, applications of 18 hardening laws for fitting the uniaxial tensile stress-strain data of 12 automotive sheet metals were thoroughly compared. The comparisons reveal that the proposed hardening laws capture well the experimental stress strain data of all examined materials. Compared to several combined hardening laws, the proposed functions have comparable flexibility but require fewer parameters. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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14 pages, 4888 KiB

Open AccessArticle

Numerical Model Simulation of the Double-Roll Rotary Forging of Large Diameter Thin-Walled Disk

by Zhongquan Yu, Mingchao Chen, Chong Ma, Site Luo and Chundong Zhu

Metals 2021, 11(11), 1767; https://doi.org/10.3390/met11111767 - 03 Nov 2021

Cited by 1 | Viewed by 1518

Abstract

Double-roll rotary forging is an emerging plastic forming technology based on rotary forging. Owing to the advantages of being labor-saving, a small eccentric load, low noise and vibration, good uniformity, high surface quality, and material saving, it is very promising for the fabrication [...] Read more.

Double-roll rotary forging is an emerging plastic forming technology based on rotary forging. Owing to the advantages of being labor-saving, a small eccentric load, low noise and vibration, good uniformity, high surface quality, and material saving, it is very promising for the fabrication of large diameter thin-walled disks. To date, little relevant research on the double-roll rotary forging technology of large diameter thin-walled metal disks has been reported, and the deformation characteristic and the influence of three key parameters on the double-roll rotary forging process remain uninvestigated. Herein, a reasonable 3D rigid-plastic numerical model of the double-roll rotary forging of a disk workpiece is established under the Deform software environment. Based on the valid 3D numerical model, the deformation mechanism, and the effective laws of three key parameters (feed rate v of the lower die, rotational speed n of the upper die, and the initial temperature T of the disk workpiece) on the metal flow and force and power parameters in the double-roll rotary forging process have been explored. The research results provide valuable guidelines for a better understanding of double-roll rotary forging for the fabrication of large diameter thin-walled disks. Full article

(This article belongs to the Special Issue Sheet Metal Forming)

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