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Metal Forming and Forging

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (10 October 2022) | Viewed by 35477

Special Issue Editors


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Guest Editor
Department of Mechanical and Industrial Production, Mondragon Unibertsitatea, Loramendi 4, 20500 Mondragon, Spain
Interests: sheet metal forming; forging; material and tribological characterization; modelling

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Guest Editor
1. Eurecat, Centre Tecnològic de Catalunya, Manresa, Barcelona, Spain
2. Division of Mechanics of Solid Materials, Luleå University of Technology, Luleå, Sweden
Interests: fracture mechanics; fatigue; advanced high strength steels
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Special Issue Information

Dear Colleagues,

Metal forming and forging and are used extensively for the industrial production of high-added-value components using different metal alloys. Continuous research in both production techniques is necessary to understand the mechanisms that govern the transformation of the metal into its final shape, avoid final defects, and predict the final properties of the components.

The aim of this Special Issue is to collect outstanding papers about the above-mentioned processes that can help to solve and understand real industrial problems for better and more robust process design, process monitoring, and control.

Of special interest will be the contributions about the development of new material and the tribological/contact characterization methods ending in advanced numerical models that enable the simulation of complex industrial processes and their understanding. Linked to this, we are also expecting contributions about innovative processes that allow the manufacturing of complex components using conventional and hard to process metals. These new processes could be based on numerical modelling or experimental observations.

Dr. Lander Galdós
Prof. Daniel Casellas
Guest Editors

Manuscript Submission Information

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Keywords

  • Sheet metal forming: deep drawing and stamping, hot stamping and press hardening, gas or fluid media forming, shear forming, roll forming, and levelling
  • Bulk metal forming, forging: cold and hot forging, rolling processes, and bulk sheet metal forming
  • Material and tribological/contact characterization and modelling
  • Microstructural evolution modelling
  • Damagen failure and ductile fracture modelling, final properties prediction
  • Model-based process control, analytical and empirical methods

Published Papers (16 papers)

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Research

27 pages, 11775 KiB  
Article
Dynamic Analysis of Closed Die Electromagnetic Sheet Metal Forming to Predict Deformation and Failure of AA6061-T6 Alloy Using a Fully Coupled Finite Element Model
by Zarak Khan, Mushtaq Khan, Se-Jin Yook, Ashfaq Khan, Muhammad Younas, Muhammad Zeeshan Zahir and Muhammad Asad
Materials 2022, 15(22), 7997; https://doi.org/10.3390/ma15227997 - 12 Nov 2022
Cited by 2 | Viewed by 1488
Abstract
This research presents a fully coupled 3D numerical model to analyse the dynamics of high-speed electromagnetic forming process for aluminium alloy AA6061-T6. The effect of Lorentz force distribution, velocity and kinetic energy on deformation, the bounce back effect and failure of the sheet [...] Read more.
This research presents a fully coupled 3D numerical model to analyse the dynamics of high-speed electromagnetic forming process for aluminium alloy AA6061-T6. The effect of Lorentz force distribution, velocity and kinetic energy on deformation, the bounce back effect and failure of the sheet has been investigated. Experiments were performed for AA6061-T6 alloy using an 18.750 KJ electromagnetic forming machine for varying the sheet thickness (0.5 mm, 1.02 mm and 1.63 mm) compared with the simulation results. The results showed that increasing the sheet thickness increases the Lorentz force due to a higher induced current. The inertial forces were more pronounced in thicker sheets (1.63 mm) as compared to the thinner sheets (0.5 mm and 1.02 mm), resulting in a higher bounce back effect for the thicker sheet. The numerical model accurately predicted the sheet failure for the 0.5-mm sheet, as also observed from the experimentation. The sheet deformation from simulations was found to be in good agreement with the experimental results. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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20 pages, 6489 KiB  
Article
An Experimental Analysis of the High-Cycle Fatigue Fracture of H13 Hot Forging Tool Steels
by Erik Calvo-García, Sara Valverde-Pérez, Antonio Riveiro, David Álvarez, Manuel Román, César Magdalena, Aida Badaoui, Pedro Moreira and Rafael Comesaña
Materials 2022, 15(21), 7411; https://doi.org/10.3390/ma15217411 - 22 Oct 2022
Cited by 2 | Viewed by 1634
Abstract
In this study, the axial fatigue behaviour of hot forging tool steels at room temperature was investigated. Fatigue tests were performed on two steels within the same H13 specification. The fatigue tests were carried out in the high-cycle fatigue domain under normal conditions. [...] Read more.
In this study, the axial fatigue behaviour of hot forging tool steels at room temperature was investigated. Fatigue tests were performed on two steels within the same H13 specification. The fatigue tests were carried out in the high-cycle fatigue domain under normal conditions. These tests were also performed on specimens in contact with a corrosive medium, applying stress values that led to the high-cycle fatigue domain under normal conditions for the sake of comparison. Both materials showed similar fatigue strengths when they were tested under normal conditions. In contrast, corrosion fatigue lives were much lower than in normal tests and differed significantly between the two steels. Crack initiation was triggered by microstructural and surface defects in the normal tests, whereas the formation of corrosion pits caused crack initiation in the corrosion fatigue tests. Moreover, a fracture surface analysis revealed dissimilar crack propagation areas between both steels, which suggested that both steels had different fracture toughness. These results were in line with the differences observed between the carbide and grain sizes of both of the material microstructures. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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24 pages, 10872 KiB  
Article
Hardness Assessment Considering Nitrided Layers Based on Tempering Tests for Numerical Wear Prediction for Forging Processes
by Bernd-Arno Behrens, Kai Brunotte, Hendrik Wester, Uwe Lorenz and Felix Müller
Materials 2022, 15(20), 7105; https://doi.org/10.3390/ma15207105 - 13 Oct 2022
Cited by 2 | Viewed by 1261
Abstract
The nitriding of forging tools is an industrially established standard used to increase the hardness of the tool surface layer and reduce wear. However, this modification of the tool surface layer, as well as the microstructural changes that occur during this operation due [...] Read more.
The nitriding of forging tools is an industrially established standard used to increase the hardness of the tool surface layer and reduce wear. However, this modification of the tool surface layer, as well as the microstructural changes that occur during this operation due to the thermo-mechanical load, cannot be considered during wear calculations with the widely used Archard wear model in the context of FE simulations. Based on previous work, this study further develops two tempering tests for the investigation of the hardness evolution of two nitride profiles based on H11 tool steel. Here, significant tempering effects could be observed depending on temperature, mechanical stress superposition and time. The results are used for setting up a new material model that is implemented in an existing numerical wear model. The validation is carried out in two laboratory forging test series. The evaluation shows that the hardness development in terms of tempering effects of a nitrided forging tool can be numerically predicted, especially for high forging cycles. However, due to the unexpected occurrence of adhesion effects, only limited applicability of the wear prediction then carried out is achieved. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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19 pages, 5398 KiB  
Article
Friction Modelling for Tube Hydroforming Processes—A Numerical and Experimental Study with Different Viscosity Lubricants
by Lander Galdos, Javier Trinidad, Nagore Otegi and Carlos Garcia
Materials 2022, 15(16), 5655; https://doi.org/10.3390/ma15165655 - 17 Aug 2022
Cited by 4 | Viewed by 1352
Abstract
The final quality of sheet and tube metal–formed components strongly depends on the tribology and friction conditions between the tools and the material to be formed. Furthermore, it has been recently demonstrated that friction is the numerical input parameter that has the biggest [...] Read more.
The final quality of sheet and tube metal–formed components strongly depends on the tribology and friction conditions between the tools and the material to be formed. Furthermore, it has been recently demonstrated that friction is the numerical input parameter that has the biggest effect in the numerical models used for feasibility studies and process design. For these reasons, industrial dedicated software packages have introduced friction laws which are dependent on sliding velocity, contact pressure and sometimes strain suffered by the sheet, and currently, temperature dependency is being implemented as it has also a major effect on friction. In this work, three lubricants having different viscosity have been characterized using the tube-sliding test. The final aim of the study is to fit friction laws that are contact pressure and sliding velocity dependent for their use in tube hydroforming modeling. The tests performed at various contact pressures and velocities have demonstrated that viscosity has a major effect on friction. Experimental hydroforming tests using the three different lubricants have corroborated the importance of the lubricant in the final forming of a triangular shape. The measurement of the axial forces and the final principal strains of the formed tubes have shown the importance of using advanced friction laws to properly model the hydroforming process using the finite element modeling. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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15 pages, 8246 KiB  
Article
Study on Mandrel Forging and Necking Process of a Hollow Shaft with an Inner Stepped Hole
by Xiqing Ge, Chensheng Tian, Yupeng Lu and Guangchun Wang
Materials 2022, 15(15), 5431; https://doi.org/10.3390/ma15155431 - 7 Aug 2022
Viewed by 2901
Abstract
An advanced process of mandrel forging and necking (MFN) was proposed for a hollow shaft with an inner stepped hole. The conventional mandrel forging process with an equal-diameter mandrel was used to form the outer stepped preform, and then the preform was formed [...] Read more.
An advanced process of mandrel forging and necking (MFN) was proposed for a hollow shaft with an inner stepped hole. The conventional mandrel forging process with an equal-diameter mandrel was used to form the outer stepped preform, and then the preform was formed into the hollow shaft with an inner stepped hole using the MFN process. A numerical simulation model was established to study the effect of the pressing reduction and the rotation angle on the MFN process. A preforming design method based on the isometric radius difference was given according to the principle of the equal volume, and the parameter relationships between the outer and inner stepped shapes were clarified. The experimental deformation laws of the MFN process were consistent with those obtained by the simulation. The MFN process and its preforming design method provide a new free forging approach for large hollow forgings with inner stepped holes. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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21 pages, 2493 KiB  
Article
A Reinforcement Learning Control in Hot Stamping for Cycle Time Optimization
by Nuria Nievas, Adela Pagès-Bernaus, Francesc Bonada, Lluís Echeverria, Albert Abio, Danillo Lange and Jaume Pujante
Materials 2022, 15(14), 4825; https://doi.org/10.3390/ma15144825 - 11 Jul 2022
Cited by 4 | Viewed by 1450
Abstract
Hot stamping is a hot metal forming technology increasingly in demand that produces ultra-high strength parts with complex shapes. A major concern in these systems is how to shorten production times to improve production Key Performance Indicators. In this work, we present a [...] Read more.
Hot stamping is a hot metal forming technology increasingly in demand that produces ultra-high strength parts with complex shapes. A major concern in these systems is how to shorten production times to improve production Key Performance Indicators. In this work, we present a Reinforcement Learning approach that can obtain an optimal behavior strategy for dynamically managing the cycle time in hot stamping to optimize manufacturing production while maintaining the quality of the final product. Results are compared with the business-as-usual cycle time control approach and the optimal solution obtained by the execution of a dynamic programming algorithm. Reinforcement Learning control outperforms the business-as-usual behavior by reducing the cycle time and the total batch time in non-stable temperature phases. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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17 pages, 3352 KiB  
Article
Theoretical and Experimental Study on the Effect of Selected Parameters in a New Method of Extrusion with a Movable Sleeve
by Grzegorz Winiarski
Materials 2022, 15(13), 4585; https://doi.org/10.3390/ma15134585 - 29 Jun 2022
Cited by 3 | Viewed by 1451
Abstract
This paper presents a new method for forming hollow flanged products. The method involves extrusion with the use of a sleeve moving in the opposite direction to that of the punch. A tube with a constant hole diameter and two different outside diameters, [...] Read more.
This paper presents a new method for forming hollow flanged products. The method involves extrusion with the use of a sleeve moving in the opposite direction to that of the punch. A tube with a constant hole diameter and two different outside diameters, made of aluminum alloy EN AW 6060 was used as a material. Numerical calculations were performed using Deform 2D/3D. Experiments were conducted on the PYE 160SS hydraulic press equipped with a specially designed device in which the punch is driven by the press slide while the moveable sleeve is driven by two hydraulic servomotors. Both numerical simulations and experiments were conducted under cold forming conditions. The aim of this study was to determine the effect of selected parameters (flange diameter, height of the cavity in the moveable sleeve, and the chamfer angle between the regions with different outside diameters on the workpiece and in the moveable sleeve cavity) on the stability of the extrusion process. Results were then used to undertake detailed comparative analyses of underfill, flange heights, and flange flank inclination angles. Findings of the analyses served as a basis for drawing conclusions regarding the effect of the analyzed parameters on the investigated extrusion process. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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27 pages, 2963 KiB  
Article
Machine Learning-Based Surrogate Model for Press Hardening Process of 22MnB5 Sheet Steel Simulation in Industry 4.0
by Albert Abio, Francesc Bonada, Jaume Pujante, Marc Grané, Nuria Nievas, Danillo Lange and Oriol Pujol
Materials 2022, 15(10), 3647; https://doi.org/10.3390/ma15103647 - 20 May 2022
Cited by 6 | Viewed by 2596
Abstract
The digitalization of manufacturing processes offers great potential in quality control, traceability, and the planning and setup of production. In this regard, process simulation is a well-known technology and a key step in the design of manufacturing processes. However, process simulations are computationally [...] Read more.
The digitalization of manufacturing processes offers great potential in quality control, traceability, and the planning and setup of production. In this regard, process simulation is a well-known technology and a key step in the design of manufacturing processes. However, process simulations are computationally and time-expensive, typically beyond the manufacturing-cycle time, severely limiting their usefulness in real-time process control. Machine Learning-based surrogate models can overcome these drawbacks, and offer the possibility to achieve a soft real-time response, which can be potentially developed into full close-loop manufacturing systems, at a computational cost that can be realistically implemented in an industrial setting. This paper explores the novel concept of using a surrogate model to analyze the case of the press hardening of a steel sheet of 22MnB5. This hot sheet metal forming process involves a crucial heat treatment step, directly related to the final part quality. Given its common use in high-responsibility automobile parts, this process is an interesting candidate for digitalization in order to ensure production quality and traceability. A comparison of different data and model training strategies is presented. Finite element simulations for a transient heat transfer analysis are performed with ABAQUS software and they are used for the training data generation to effectively implement a ML-based surrogate model capable of predicting key process outputs for entire batch productions. The resulting final surrogate predicts the behavior and evolution of the most important temperature variables of the process in a wide range of scenarios, with a mean absolute error around 3 °C, but reducing the time four orders of magnitude with respect to the simulations. Moreover, the methodology presented is not only relevant for manufacturing purposes, but can be a technology enabler for advanced systems, such as digital twins and autonomous process control. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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20 pages, 12988 KiB  
Article
Stating Failure Modelling Limitations of High Strength Sheets: Implications to Sheet Metal Forming
by Olle Sandin, Pär Jonsén, David Frómeta and Daniel Casellas
Materials 2021, 14(24), 7821; https://doi.org/10.3390/ma14247821 - 17 Dec 2021
Cited by 7 | Viewed by 2504
Abstract
This article discusses the fracture modelling accuracy of strain-driven ductile fracture models when introducing damage of high strength sheet steel. Numerical modelling of well-known fracture mechanical tests was conducted using a failure and damage model to control damage and fracture evolution. A thorough [...] Read more.
This article discusses the fracture modelling accuracy of strain-driven ductile fracture models when introducing damage of high strength sheet steel. Numerical modelling of well-known fracture mechanical tests was conducted using a failure and damage model to control damage and fracture evolution. A thorough validation of the simulation results was conducted against results from laboratory testing. Such validations show that the damage and failure model is suited for modelling of material failure and fracture evolution of specimens without damage. However, pre-damaged specimens show less correlation as the damage and failure model over-predicts the displacement at crack initiation with an average of 28%. Consequently, the results in this article show the need for an extension of the damage and failure model that accounts for the fracture mechanisms at the crack tip. Such extension would aid in the improvement of fracture mechanical testing procedures and the modelling of high strength sheet metal manufacturing, as several sheet manufacturing processes are defined by material fracture. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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14 pages, 8243 KiB  
Article
Pilot Demonstration of Hot Sheet Metal Forming Using 3D Printed Dies
by Jaume Pujante, Borja González and Eduard Garcia-Llamas
Materials 2021, 14(19), 5695; https://doi.org/10.3390/ma14195695 - 30 Sep 2021
Cited by 5 | Viewed by 2525
Abstract
Since the popularization of press hardening in the early noughties, die and tooling systems have experienced considerable advances, with tool refrigeration as an important focus. However, it is still complicated to obtain homogeneous cooling and avoid hot spot issues in complex geometries. Additive [...] Read more.
Since the popularization of press hardening in the early noughties, die and tooling systems have experienced considerable advances, with tool refrigeration as an important focus. However, it is still complicated to obtain homogeneous cooling and avoid hot spot issues in complex geometries. Additive Manufacturing allows designing cavities inside the material volume with little limitation in terms of channel intersection or bore entering and exit points. In this sense, this technology is a natural fit for obtaining surface-conforming cooling channels: an attractive prospect for refrigerated tools. This work describes a pilot experience in 3D-printed press hardening tools, comparing the performance of additive manufactured Maraging steel 1.2709 to conventional wrought hot work tool steel H13 on two different metrics: durability and thermal performance. For the first, wear studies were performed in a controlled pilot plant environment after 800 hot stamping strokes in an omega tool configuration. On the second, a demonstrator tool based on a commercial tool with hot spot issues, was produced by 3D printing including surface-conformal cooling channels. This tool was then used in a pilot press hardening line, in which tool temperature was analyzed and compared to an equivalent tool produced by conventional means. Results show that the Additive Manufacturing technologies can be successfully applied to the production of press hardening dies, particularly in intricate geometries where new cooling channel design strategies offer a solution for hot spots and inhomogeneous thermal loads. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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14 pages, 3286 KiB  
Article
A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in Heat-Assisted Forming Operations
by Alan A. Camberg, Tobias Erhart and Thomas Tröster
Materials 2021, 14(17), 5106; https://doi.org/10.3390/ma14175106 - 6 Sep 2021
Cited by 2 | Viewed by 2689
Abstract
Heat-assisted forming processes are becoming increasingly important in the manufacturing of sheet metal parts for body-in-white applications. However, the non-isothermal nature of these processes leads to challenges in evaluating the forming limits, since established methods such as Forming Limit Curves (FLCs) only allow [...] Read more.
Heat-assisted forming processes are becoming increasingly important in the manufacturing of sheet metal parts for body-in-white applications. However, the non-isothermal nature of these processes leads to challenges in evaluating the forming limits, since established methods such as Forming Limit Curves (FLCs) only allow the assessment of critical forming strains for steady temperatures. For this reason, a temperature-dependent extension of the well-established GISSMO (Generalized Incremental Stress State Dependent Damage Model) fracture indicator framework is developed by the authors to predict forming failures under non-isothermal conditions. In this paper, a general approach to combine several isothermal FLCs within the temperature-extended GISSMO model into a temperature-dependent forming limit surface is investigated. The general capabilities of the model are tested in a coupled thermo-mechanical FEA using the example of warm forming of an AA5182-O sheet metal cross-die cup. The obtained results are then compared with state of the art of evaluation methods. By taking the strain and temperature path into account, GISSMO predicts greater drawing depths by up to 20% than established methods. In this way the forming and so the lightweight potential of sheet metal parts can by fully exploited. Moreover, the risk and locus of failure can be evaluated directly on the part geometry by a contour plot. An additional advantage of the GISSMO model is the applicability for low triaxialities as well as the possibility to predict the materials behavior beyond necking up to ductile fracture. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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23 pages, 13434 KiB  
Article
Analysis of Deformation, the Stressed State and Fracture Predictions for Cogging Shafts with Convex Anvils
by Marcin Kukuryk
Materials 2021, 14(11), 3113; https://doi.org/10.3390/ma14113113 - 6 Jun 2021
Cited by 1 | Viewed by 2021
Abstract
In this article, a new manner of cogging a forging (type: shaft), consisting in the application of a two-stage process composed of preliminary shaping in convex anvils, and also principal forging in flat or shaped anvils, is presented. A new manner of forging [...] Read more.
In this article, a new manner of cogging a forging (type: shaft), consisting in the application of a two-stage process composed of preliminary shaping in convex anvils, and also principal forging in flat or shaped anvils, is presented. A new manner of forging brought about the formation of favorable conditions for achieving the maximum values of the effective strain in the central part of a forging, accompanied by a simultaneous absence of tensile stresses, which was exerting a favorable influence upon reforging the axial zone of an ingot. What was determined, was the effective geometric shapes of convex anvils; the efficiency of different technological parameters in the case of the intensity of reforging the axial zone of an ingot was analyzed as well. The investigations were complemented by means of predicting the formation of ductile fractures in the course of forging with the application of three different ductile fracture criteria. The comparison of theoretical and experimental outcomes of investigations indicates a good level of being commensurate. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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12 pages, 7598 KiB  
Article
Free-Forging of Pure Titanium with High Reduction of Thickness by Plasma-Carburized SKD11 Dies
by Tatsuhiko Aizawa, Tomoaki Yoshino, Yohei Suzuki and Tomomi Shiratori
Materials 2021, 14(10), 2536; https://doi.org/10.3390/ma14102536 - 13 May 2021
Cited by 9 | Viewed by 1572
Abstract
A tool steel type SKD11 punch was plasma carburized at 673 K for 14.4 ks at 70 Pa to make carbon supersaturation. This carburized SKD11 punch was employed for upsetting the pure titanium wire with the diameter of 1.00 mm up to the [...] Read more.
A tool steel type SKD11 punch was plasma carburized at 673 K for 14.4 ks at 70 Pa to make carbon supersaturation. This carburized SKD11 punch was employed for upsetting the pure titanium wire with the diameter of 1.00 mm up to the reduction of thickness by 70% in a single shot. Its contact interface to titanium work was analyzed to describe the anti-galling behavior in this forging. Little trace of titanium proved that the galling process was suppressed by the in situ solid lubrication. The isolated free carbon agglomerates are wrought as a solid lubricant to sustain the galling-free forging process. This anti-galling upsetting reduced the residual strains in the forged wires. A long titanium wire with a length of 45 mm was incrementally upset to yield the titanium ribbon with a thickness of 0.3 mm, the width of 2.3 mm, and the length of 50 mm. The grain size of original pure titanium was much reduced to 2 μm on average. A micro-pillared microtexture was imprinted onto this forged titanium ribbon. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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15 pages, 4949 KiB  
Article
Numerical Investigations on Thermal Forming Limit Testing with Local Inductive Heating for Hot Forming of AA7075
by Franz Reuther, Thomas Lieber, Jürgen Heidrich and Verena Kräusel
Materials 2021, 14(8), 1882; https://doi.org/10.3390/ma14081882 - 9 Apr 2021
Cited by 5 | Viewed by 2130
Abstract
Forming 7000-series aluminum alloys under elevated temperatures is particularly attractive due to their increased formability. To enable process design by finite element simulation for hot forming, strain-based criteria, such as temperature-dependent forming limit diagrams (TFLD), can be consulted to assess forming feasibility. This [...] Read more.
Forming 7000-series aluminum alloys under elevated temperatures is particularly attractive due to their increased formability. To enable process design by finite element simulation for hot forming, strain-based criteria, such as temperature-dependent forming limit diagrams (TFLD), can be consulted to assess forming feasibility. This work numerically investigates the extent to which in-plane experimental concepts with partial inductive heating are suitable for detecting discrete failure points in TFLD. In particular, an alternative to the currently widely used thickness-reduced specimen geometries was created for cruciform specimens under biaxial tension. First, the temperature-dependent and strain-rate-dependent flow behavior was investigated for AA7075 under uniaxial tension. A heat source model for partial inductive heating was inversely parameterized based on heating experiments. Subsequently, the test procedures were simulated with different specimen geometries under discrete strain conditions. Different concepts were discussed for deriving a suitable specimen shape for the biaxial tension case, and the influence of different notch and slot forms were shown. The simulations showed that partial inductive heating was suitable to induce failure situations, thus creating TFLDs. For the biaxial tension case, a sufficiently large temperature gradient was required to use cruciform specimens without thickness reduction. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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14 pages, 3123 KiB  
Article
An Analytical Model for Estimating the Bending Curvatures of Metal Sheets in Laser Peen Forming
by Yunxia Ye, Zeng Nie, Xu Huang, Xudong Ren and Lin Li
Materials 2021, 14(2), 462; https://doi.org/10.3390/ma14020462 - 19 Jan 2021
Viewed by 2218
Abstract
Laser peen forming (LPF) is suitable for shaping sheet metals without the requirement for die/mold and without causing high temperatures. An analytical model for estimating the bending curvatures of LPF is convenient and necessary for better understanding of the physical processes involved. In [...] Read more.
Laser peen forming (LPF) is suitable for shaping sheet metals without the requirement for die/mold and without causing high temperatures. An analytical model for estimating the bending curvatures of LPF is convenient and necessary for better understanding of the physical processes involved. In this paper, we describe a new analytical model based on internal force balance and the energy transformation in LPF. Experiments on 2024 aluminum alloy sheets of 1–3 mm thickness were performed to validate the analytical model. The results showed that for 1 mm and 3 mm thick–thin plates, the curvature obtained by the analytical model changes from −14 × 10−4 mm−1 and −1 × 10−4 mm−1 to 55 × 10−4 mm−1 and −21 × 10−4 mm−1, respectively, with the increase of laser energy, which is consistent with the experimental trend. So, when either the stress gradient mechanism (SGM) or the shock bending mechanism (SBM) overwhelmingly dominated the forming process, the analytical model could give relatively accurate predicted curvatures compared with the experimental data. Under those conditions where SGM and SBM were comparable, the accuracy of the model was low, because of the complex stress distributions within the material, and the complex energy coupling process under these conditions. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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21 pages, 5577 KiB  
Article
Reconfigurable Multipoint Forming Using Waffle-Type Elastic Cushion and Variable Loading Profile
by Mohammed Moheen, Adel Abdel-Wahab, Hany Hassanin and Khamis Essa
Materials 2020, 13(20), 4506; https://doi.org/10.3390/ma13204506 - 12 Oct 2020
Cited by 4 | Viewed by 2725
Abstract
There is an increasing demand for flexible, relatively inexpensive manufacturing techniques that can accommodate frequent changes to part design and production technologies, especially when limited batch sizes are required. Reconfigurable multi-point forming (MPF) is an advanced manufacturing technique which uses a reconfigurable die [...] Read more.
There is an increasing demand for flexible, relatively inexpensive manufacturing techniques that can accommodate frequent changes to part design and production technologies, especially when limited batch sizes are required. Reconfigurable multi-point forming (MPF) is an advanced manufacturing technique which uses a reconfigurable die consisting of a set of moveable pins to shape sheet metal parts easily. This study investigates the use of a novel variable thickness waffle-type elastic cushion and a variable punch-loading profile to either eliminate or minimise defects associated with MPF, namely wrinkling, thickness variation, shape deviation, and dimpling. Finite element modelling (FEM), analysis of variance (ANOVA), and the response surface methodology (RSM) were used to investigate the effect of process parameters pertaining to the cushion dimensions and type of loading profile on the aforementioned defects. The results of this study indicate that the most significant process parameters were maximum cushion thickness, cushion cut-out base radius, and cushion cut-out profile radius. The type of loading profile was found to be insignificant in all responses, but further investigation is required as the rate, and the thermal effects were not considered in the material modelling. Optimal process parameters were found to be a maximum cushion thickness of 3.01 mm, cushion cut-out base radius of 2.37 mm, cushion cut-out profile radius of 10 mm, and a “linear” loading profile. This yielded 0.50 mm, 0.00515 mm, 0.425 mm for peak shape deviation, thickness variation, and wrinkling, respectively. Full article
(This article belongs to the Special Issue Metal Forming and Forging)
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