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3 pages, 182 KiB

Open AccessEditorial

Advances in Plastic Forming of Metals

by Myoung-Gyu Lee and Yannis P. Korkolis

Metals 2018, 8(4), 272; https://doi.org/10.3390/met8040272 - 16 Apr 2018

Cited by 4 | Viewed by 3489

Abstract

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(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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15 pages, 4661 KiB

Open AccessArticle

Sensitivity Analysis of Oxide Scale Influence on General Carbon Steels during Hot Forging

by Bernd-Arno Behrens, Alexander Chugreev, Birgit Awiszus, Marcel Graf, Rudolf Kawalla, Madlen Ullmann, Grzegorz Korpala and Hendrik Wester

Metals 2018, 8(2), 140; https://doi.org/10.3390/met8020140 - 17 Feb 2018

Cited by 7 | Viewed by 4197

Abstract

Increasing product requirements have made numerical simulation into a vital tool for the time- and cost-efficient process design. In order to accurately model hot forging processes with finite, element-based numerical methods, reliable models are required, which take the material behaviour, surface phenomena of [...] Read more.

Increasing product requirements have made numerical simulation into a vital tool for the time- and cost-efficient process design. In order to accurately model hot forging processes with finite, element-based numerical methods, reliable models are required, which take the material behaviour, surface phenomena of die and workpiece, and machine kinematics into account. In hot forging processes, the surface properties are strongly affected by the growth of oxide scale, which influences the material flow, friction, and product quality of the finished component. The influence of different carbon contents on material behaviour is investigated by considering three different steel grades (C15, C45, and C60). For a general description of the material behaviour, an empirical approach is used to implement mathematical functions for expressing the relationship between flow stress and dominant influence variables like alloying elements, initial microstructure, and reheating mode. The deformation behaviour of oxide scale is separately modelled for each component with parameterized flow curves. The main focus of this work lies in the consideration of different materials as well as the calculation and assignment of their material properties in dependence on current process parameters by application of subroutines. The validated model is used to carry out the influence of various oxide scale parameters, like the scale thickness and the composition, on the hot forging process. Therefore, selected parameters have been varied within a numerical sensitivity analysis. The results show a strong influence of oxide scale on the friction behaviour as well as on the material flow during hot forging. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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9 pages, 5196 KiB

Open AccessArticle

Generation of a Layer of Severe Plastic Deformation near Friction Surfaces in Upsetting of Steel Specimens

by Sergei Alexandrov, Leposava Šidjanin, Dragiša Vilotić, Dejan Movrin and Lihui Lang

Metals 2018, 8(1), 71; https://doi.org/10.3390/met8010071 - 19 Jan 2018

Cited by 10 | Viewed by 4017

Abstract

Narrow layers of severe plastic deformation are often generated near frictional interfaces in deformation processes as a result of shear deformation caused by friction. This results in material behavior that is very different from that encountered in conventional tests. To develop models capable [...] Read more.

Narrow layers of severe plastic deformation are often generated near frictional interfaces in deformation processes as a result of shear deformation caused by friction. This results in material behavior that is very different from that encountered in conventional tests. To develop models capable of predicting the behavior of material near frictional surfaces, it is necessary to design and carry out tests that account for typical features of deformation processes in a narrow sub-surface layer. In the present paper, upsetting of steel specimens between conical and flat dies is used as such a test. The objective of the paper is to correlate the thickness of the layer of severe plastic deformation generated near the friction surface and the die angle using a new criterion for determining the boundary between the layer of severe plastic deformation and the bulk. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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6868 KiB

Open AccessArticle

Effect of Constitutive Equations on Springback Prediction Accuracy in the TRIP1180 Cold Stamping

by Ki-Young Seo, Jae-Hong Kim, Hyun-Seok Lee, Ji Hoon Kim and Byung-Min Kim

Metals 2018, 8(1), 18; https://doi.org/10.3390/met8010018 - 30 Dec 2017

Cited by 23 | Viewed by 5659

Abstract

This study aimed to evaluate the effect of constitutive equations on springback prediction accuracy in cold stamping with various deformation modes. This study investigated the ability of two yield functions to describe the yield behavior: Hill’48 and Yld2000-2d. Isotropic and kinematic hardening models [...] Read more.

This study aimed to evaluate the effect of constitutive equations on springback prediction accuracy in cold stamping with various deformation modes. This study investigated the ability of two yield functions to describe the yield behavior: Hill’48 and Yld2000-2d. Isotropic and kinematic hardening models based on the Yoshida-Uemori model were adopted to describe the hardening behavior. The chord modulus model was used to calculate the degradation of the elastic modulus that occurred during plastic loading. Various material tests (such as uniaxial tension, tension-compression, loading-unloading, and hydraulic bulging tests) were conducted to determine the material parameters of the models. The parameters thus obtained were implemented in a springback prediction finite element (FE) simulation, and the results were compared to experimental data. The springback prediction accuracy was evaluated using U-bending and T-shape drawing. The constitutive equations wielded significant influence over the springback prediction accuracy. This demonstrates the importance of selecting appropriate constitutive equations that accurately describe the material behaviors in FE simulations. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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5888 KiB

Open AccessArticle

Revisiting Formability and Failure of AISI304 Sheets in SPIF: Experimental Approach and Numerical Validation

by Gabriel Centeno, Andrés Jesús Martínez-Donaire, Isabel Bagudanch, Domingo Morales-Palma, María Luisa Garcia-Romeu and Carpóforo Vallellano

Metals 2017, 7(12), 531; https://doi.org/10.3390/met7120531 - 28 Nov 2017

Cited by 20 | Viewed by 4551

Abstract

Single Point Incremental Forming (SPIF) is a flexible and economic manufacturing process with a strong potential for manufacturing small and medium batches of highly customized parts. Formability and failure in SPIF have been intensively discussed in recent years, especially because this process allows [...] Read more.

Single Point Incremental Forming (SPIF) is a flexible and economic manufacturing process with a strong potential for manufacturing small and medium batches of highly customized parts. Formability and failure in SPIF have been intensively discussed in recent years, especially because this process allows stable plastic deformation well above the conventional forming limits, as this enhanced formability is only achievable within a certain range of process parameters depending on the material type. This paper analyzes formability and failure of AISI304-H111 sheets deformed by SPIF compared to conventional testing conditions (including Nakazima and stretch-bending tests). With this purpose, experimental tests in SPIF and stretch-bending were carried out and a numerical model of SPIF is performed. The results allow the authors to establish the following contributions regarding SPIF: (i) the setting of the limits of the formability enhancement when small tool diameters are used, (ii) the evolution of the crack when failure is attained and (iii) the determination of the conditions upon which necking is suppressed, leading directly to ductile fracture in SPIF. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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6104 KiB

Open AccessArticle

Radial Basis Functional Model of Multi-Point Dieless Forming Process for Springback Reduction and Compensation

by Misganaw Abebe, Jun-Seok Yoon and Beom-Soo Kang

Metals 2017, 7(12), 528; https://doi.org/10.3390/met7120528 - 27 Nov 2017

Cited by 13 | Viewed by 4802

Abstract

Springback in multi-point dieless forming (MDF) is a common problem because of the small deformation and blank holder free boundary condition. Numerical simulations are widely used in sheet metal forming to predict the springback. However, the computational time in using the numerical tools [...] Read more.

Springback in multi-point dieless forming (MDF) is a common problem because of the small deformation and blank holder free boundary condition. Numerical simulations are widely used in sheet metal forming to predict the springback. However, the computational time in using the numerical tools is time costly to find the optimal process parameters value. This study proposes radial basis function (RBF) to replace the numerical simulation model by using statistical analyses that are based on a design of experiment (DOE). Punch holding time, blank thickness, and curvature radius are chosen as effective process parameters for determining the springback. The Latin hypercube DOE method facilitates statistical analyses and the extraction of a prediction model in the experimental process parameter domain. Finite element (FE) simulation model is conducted in the ABAQUS commercial software to generate the springback responses of the training and testing samples. The genetic algorithm is applied to find the optimal value for reducing and compensating the induced springback for the different blank thicknesses using the developed RBF prediction model. Finally, the RBF numerical result is verified by comparing with the FE simulation result of the optimal process parameters and both results show that the springback is almost negligible from the target shape. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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6536 KiB

Open AccessFeature PaperArticle

Anisotropic Hardening Behaviour and Springback of Advanced High-Strength Steels

by Jaebong Jung, Sungwook Jun, Hyun-Seok Lee, Byung-Min Kim, Myoung-Gyu Lee and Ji Hoon Kim

Metals 2017, 7(11), 480; https://doi.org/10.3390/met7110480 - 6 Nov 2017

Cited by 27 | Viewed by 8074

Abstract

Advanced high-strength steels (AHSSs) exhibit large, and sometimes anisotropic, springback recovery after forming. Accurate description of the anisotropic elasto-plastic behaviour of sheet metals is critical for predicting their anisotropic springback behaviour. For some materials, the initial anisotropy is maintained while hardening progresses. However, [...] Read more.

Advanced high-strength steels (AHSSs) exhibit large, and sometimes anisotropic, springback recovery after forming. Accurate description of the anisotropic elasto-plastic behaviour of sheet metals is critical for predicting their anisotropic springback behaviour. For some materials, the initial anisotropy is maintained while hardening progresses. However, for other materials, anisotropy changes with hardening. In this work, to account for the evolution of anisotropy of a dual-phase steel, an elastoplastic material constitutive model is developed. In particular, the combined isotropic–kinematic hardening model was modified. Tensile loading–unloading, uniaxial and biaxial tension, and tension–compression tests were conducted along the rolling, diagonal, and transverse directions to measure the anisotropic properties, and the parameters of the proposed constitutive model were determined. For validation, the proposed model was applied to a U-bending process, and the measured springback angles were compared to the predicted ones. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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735 KiB

Open AccessArticle

On the Use of Maximum Force Criteria to Predict Localised Necking in Metal Sheets under Stretch-Bending

by Domingo Morales-Palma, Andrés J. Martínez-Donaire and Carpóforo Vallellano

Metals 2017, 7(11), 469; https://doi.org/10.3390/met7110469 - 2 Nov 2017

Cited by 12 | Viewed by 4757

Abstract

The maximum force criteria and their derivatives, the Swift and Hill criteria, have been extensively used in the past to study sheet formability. Many extensions or modifications of these criteria have been proposed to improve necking predictions under only stretching conditions. This work [...] Read more.

The maximum force criteria and their derivatives, the Swift and Hill criteria, have been extensively used in the past to study sheet formability. Many extensions or modifications of these criteria have been proposed to improve necking predictions under only stretching conditions. This work analyses the maximum force principle under stretch-bending conditions and develops two different approaches to predict necking. The first is a generalisation of classical maximum force criteria to stretch-bending processes. The second approach is an extension of a previous work of the authors based on critical distance concepts, suggesting that necking of the sheet is controlled by the damage of a critical material volume located at the inner side of the sheet. An analytical deformation model is proposed to characterise the stretch-bending process under plane-strain conditions. Different parameters are considered, such as the thickness reduction, the gradient of variables through the sheet thickness, the thickness stress and the anisotropy of the material. The proposed necking models have been successfully applied to predict the failure in different materials, such as steel, brass and aluminium. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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5405 KiB

Open AccessArticle

Numerical Predictions of the Occurrence of Necking in Deep Drawing Processes

by Hocine Chalal and Farid Abed-Meraim

Metals 2017, 7(11), 455; https://doi.org/10.3390/met7110455 - 27 Oct 2017

Cited by 12 | Viewed by 5615

Abstract

In this work, three numerical necking criteria based on finite element (FE) simulations are proposed for the prediction of forming limit diagrams (FLDs) for sheet metals. An elastic–plastic constitutive model coupled with the Lemaitre continuum damage theory has been implemented into the ABAQUS/Explicit [...] Read more.

In this work, three numerical necking criteria based on finite element (FE) simulations are proposed for the prediction of forming limit diagrams (FLDs) for sheet metals. An elastic–plastic constitutive model coupled with the Lemaitre continuum damage theory has been implemented into the ABAQUS/Explicit software to simulate simple sheet stretching tests as well as Erichsen deep drawing tests with various sheet specimen geometries. Three numerical criteria have been investigated in order to establish an appropriate necking criterion for the prediction of formability limits. The first numerical criterion is based on the analysis of the thickness strain evolution in the central part of the specimens. The second numerical criterion is based on the analysis of the second time derivative of the thickness strain. As to the third numerical criterion, it relies on a damage threshold associated with the occurrence of necking. The FLDs thus predicted by numerical simulation of simple sheet stretching with various specimen geometries and Erichsen deep drawing tests are compared with the experimental results. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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11741 KiB

Open AccessArticle

The Mechanism of Inhomogeneous Grain Refinement in a NiTiFe Shape Memory Alloy Subjected to Single-Pass Equal-Channel Angular Extrusion

by Yanqiu Zhang and Shuyong Jiang

Metals 2017, 7(10), 400; https://doi.org/10.3390/met7100400 - 29 Sep 2017

Cited by 7 | Viewed by 5002

Abstract

Based on electron backscattered diffraction analysis and transmission electron microscopy observation, the mechanism of inhomogeneous grain refinement in a NiTiFe shape memory alloy (SMA) subjected to single-pass equal-channel angular extrusion (ECAE) was investigated. The results show that refined grains are mainly nucleated near [...] Read more.

Based on electron backscattered diffraction analysis and transmission electron microscopy observation, the mechanism of inhomogeneous grain refinement in a NiTiFe shape memory alloy (SMA) subjected to single-pass equal-channel angular extrusion (ECAE) was investigated. The results show that refined grains are mainly nucleated near grain boundaries and a small fraction of them emerges in the grain interior. The size of refined grains increases as deformation temperature increases, which indicates that a higher deformation temperature is adverse to grain refinement in the ECAE of NiTiFe SMAs. It is the accumulation and rearrangement of geometrically necessary dislocations as plastic strain increases that leads to the transition of lower angle subgrain boundaries, and finally higher angle subgrain boundaries are induced and finer grains are formed. Due to the limitation of slip systems, the mechanism of grain refinement in a NiTiFe SMA subjected to ECAE is different from that in face-centered cubic and body-centered cubic crystals. Dislocation cells and shear bands are two transition microstructures of grain refinement in the ECAE of NiTiFe SMAs. The nucleation of fine grains mainly occurs along shear bands or grain boundaries, which leads to the inhomogeneity of grain refinement. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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5129 KiB

Open AccessArticle

Effect of Computational Parameters on Springback Prediction by Numerical Simulation

by Tomasz Trzepiecinski and Hirpa G. Lemu

Metals 2017, 7(9), 380; https://doi.org/10.3390/met7090380 - 19 Sep 2017

Cited by 50 | Viewed by 8317

Abstract

Elastic recovery of the material, called springback, is one of the problems in sheet metal forming of drawpieces, especially with a complex shape. The springback can be influenced by various technological, geometrical, and material parameters. In this paper the results of experimental testing [...] Read more.

Elastic recovery of the material, called springback, is one of the problems in sheet metal forming of drawpieces, especially with a complex shape. The springback can be influenced by various technological, geometrical, and material parameters. In this paper the results of experimental testing and numerical study are presented. The experiments are conducted on DC04 steel sheets, commonly used in the automotive industry. The numerical analysis of V-die air bending tests is carried out with the finite element method (FEM)-based ABAQUS/Standard 2016 program. A quadratic Hill anisotropic yield criterion is compared with an isotropic material described by the von Mises yield criterion. The effect of a number of integration points and integration rules on the springback amount and computation time is also considered. Two integration rules available in ABAQUS: the Gauss’ integration rule and Simpson’s integration rule are considered. The effect of sample orientation according to the sheet rolling direction and friction contact behaviour on the prediction of springback is also analysed. It is observed that the width of the sample bend in the V-bending test influences the stress-state in the cross-section of the sample. Different stress-states in the sample bend of the V-shaped die cause that the sheet undergoes springback in different planes. Friction contact phenomena slightly influences the springback behaviour. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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5955 KiB

Open AccessArticle

Reduction of Induced Central Damage in Cold Extrusion of Dual-Phase Steel DP800 Using Double-Pass Dies

by Francisco Javier Amigo and Ana María Camacho

Metals 2017, 7(9), 335; https://doi.org/10.3390/met7090335 - 31 Aug 2017

Cited by 11 | Viewed by 5202

Abstract

Advanced High Strength Steels (AHSS) are a promising family of materials for applications where a high strength-to-weight ratio is required. Central burst is a typical defect commonly found in parts formed by extrusion and it can be a serious problem for the in-service [...] Read more.

Advanced High Strength Steels (AHSS) are a promising family of materials for applications where a high strength-to-weight ratio is required. Central burst is a typical defect commonly found in parts formed by extrusion and it can be a serious problem for the in-service performance of the extrudate. The finite element method is a very useful tool to predict this type of internal defect. In this work, the software DEFORM-F2 has been used to choose the best configurations of multiple-pass dies, proposed as an alternative to single-pass extrusions in order to minimize the central damage that can lead to central burst in extruded parts of AHSS, particularly, the dual-phase steel DP800. It has been demonstrated that some geometrical configurations in double-pass dies lead to a minimum value of the central damage, much lower than the one obtained in single-pass extrusion. As a general rule, the position of the minimum damage leads to choosing higher values of the contacting length between partial reductions (L) for high die semiangles (α) and to lower values of the reduction in the first pass (R_A) for low total reductions (R_T). This methodology could be extended to find the best configurations for other outstanding materials. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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16582 KiB

Open AccessArticle

Particle Size and Particle Percentage Effect of AZ61/SiCp Magnesium Matrix Micro- and Nano-Composites on Their Mechanical Properties Due to Extrusion and Subsequent Annealing

by Weigang Zhao, Song-Jeng Huang, Yi-Jhang Wu and Cheng-Wei Kang

Metals 2017, 7(8), 293; https://doi.org/10.3390/met7080293 - 1 Aug 2017

Cited by 21 | Viewed by 5675

Abstract

Magnesium metal matrix composites (Mg MMCs) possess relatively more favorable mechanical properties than Mg alloys because they add reinforcements, such as small particles, short fibers, or continuous fibers, into the matrix. This study investigated the influence of adding different sizes and percentages of [...] Read more.

Magnesium metal matrix composites (Mg MMCs) possess relatively more favorable mechanical properties than Mg alloys because they add reinforcements, such as small particles, short fibers, or continuous fibers, into the matrix. This study investigated the influence of adding different sizes and percentages of silicon carbide particles (SiCp) for manufacturing AZ61/SiCp Mg alloy composite extrusion plates on the mechanical properties of SiCp. We also examined the impact and discussed the evolution of microstructures, changes of material strength, ductility, formability, and other mechanical properties caused by a subsequent annealing treatment after plate extrusion. The results showed that the mechanical properties of plates can be improved by adding reinforcement particles. The effects of grain refinement were as follows: the smaller the size of the reinforcement particles, the greater the enhancement of mechanical properties. Among them, the AZ61/1 wt % SiCp/50 nm MMC plate had relatively excellent mechanical properties. Specifically, the ultimate tensile strength, yielding strength, ductility, hardness, and grain size of the plate were 331 MPa, 136.4 MPa, 43.1%, 62 HV, and 3.3 μm, respectively. Compared with SiCp-free Mg MMC plates, these properties of the AZ61/1 wt % SiCp/50 nm MMC plate were enhanced (or refined) by 6.4%, 3.4%, 83.4%, 2%, and 13.2%, respectively; by contrast, formability decreased by 9.1%. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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6315 KiB

Open AccessArticle

Design of U-Geometry Parameters Using Statistical Analysis Techniques in the U-Bending Process

by Wiriyakorn Phanitwong, Untika Boochakul and Sutasn Thipprakmas

Metals 2017, 7(7), 235; https://doi.org/10.3390/met7070235 - 26 Jun 2017

Cited by 7 | Viewed by 6168

Abstract

The various U-geometry parameters in the U-bending process result in processing difficulties in the control of the spring-back characteristic. In this study, the effects of U-geometry parameters, including channel width, bend angle, material thickness, tool radius, as well as workpiece length, and their [...] Read more.

The various U-geometry parameters in the U-bending process result in processing difficulties in the control of the spring-back characteristic. In this study, the effects of U-geometry parameters, including channel width, bend angle, material thickness, tool radius, as well as workpiece length, and their design, were investigated using a combination of finite element method (FEM) simulation, and statistical analysis techniques. Based on stress distribution analyses, the FEM simulation results clearly identified the different bending mechanisms and effects of U-geometry parameters on the spring-back characteristic in the U-bending process, with and without pressure pads. The statistical analyses elucidated that the bend angle and channel width have a major influence in cases with and without pressure pads, respectively. The experiments were carried out to validate the FEM simulation results. Additionally, the FEM simulation results were in agreement with the experimental results, in terms of the bending forces and bending angles. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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11471 KiB

Open AccessArticle

Advanced Plasticity Modeling for Ultra-Low-Cycle-Fatigue Simulation of Steel Pipe

by Rongting Li, Philip Eyckens, Daxin E, Jerzy Gawad, Maarten Van Poucke, Steven Cooreman and Albert Van Bael

Metals 2017, 7(4), 140; https://doi.org/10.3390/met7040140 - 14 Apr 2017

Cited by 8 | Viewed by 6409

Abstract

Pipelines and piping components may be exposed to extreme loading conditions, for instance earthquakes and hurricanes. In such conditions, they undergo severe plastic strains, which may locally reach the fracture limits due to either monotonic loading or ultra-low cycle fatigue (ULCF). Aiming to [...] Read more.

Pipelines and piping components may be exposed to extreme loading conditions, for instance earthquakes and hurricanes. In such conditions, they undergo severe plastic strains, which may locally reach the fracture limits due to either monotonic loading or ultra-low cycle fatigue (ULCF). Aiming to investigate the failure process and strain evolution of pipes enduring ULCF, a lab-scale ULCF test on an X65 steel pipeline component is simulated with finite element models, and experimental data are used to validate various material modeling assumptions. The paper focuses on plastic material modeling and compares different models for plastic anisotropy in combination with various hardening models, including isotropic, linear kinematic and combined hardening models. Both isotropic and anisotropic assumptions for plastic yielding are considered. As pipes pose difficulty for the measurement of plastic properties in mechanical testing, we calibrate an anisotropic yield locus using advanced multi-scale simulation based on texture measurements. Moreover, the importance of the anisotropy gradient across thickness is studied in detail for this thick-walled pipeline steel. It is found that the usage of a combined hardening model is essential to accurately predict the number of the cycles until failure, as well as the strain evolution during the fatigue test. The advanced hardening modeling featuring kinematic hardening has a substantially higher impact on result accuracy compared to the yield locus assumption for the studied ULCF test. Cyclic tension-compression testing is conducted to calibrate the kinematic hardening models. Additionally, plastic anisotropy and its gradient across the thickness play a notable, yet secondary role. Based on this research, it is advised to focus on improvements in strain hardening characteristics in future developments of pipeline steel with enhanced earthquake resistance. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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16551 KiB

Open AccessArticle

Design and Mechanical Properties Analysis of AA5083 Ultrafine Grained Cams

by Daniel Salcedo, Carmelo J. Luis, Rodrigo Luri, Ignacio Puertas, Javier León and Juan P. Fuertes

Metals 2017, 7(4), 116; https://doi.org/10.3390/met7040116 - 28 Mar 2017

Cited by 4 | Viewed by 4117

Abstract

This present research work deals with the development of ultrafine grained cams obtained from previously ECAP (Equal Channel Angular Pressing)-processed material and manufactured by isothermal forging. The design and the manufacturing of the dies required for the isothermal forging of the cams are [...] Read more.

This present research work deals with the development of ultrafine grained cams obtained from previously ECAP (Equal Channel Angular Pressing)-processed material and manufactured by isothermal forging. The design and the manufacturing of the dies required for the isothermal forging of the cams are shown. Optimization techniques based on the combination of design of experiments, finite element and finite volume simulations are employed to develop the dies. A comparison is made between the mechanical properties obtained with the cams manufactured from material with no previous deformation and with those from previously SPD (Severe Plastic Deformation)-processed material. In addition, a comparative study between the experimental results and those obtained from the simulations is carried out. It has been demonstrated that it is possible to obtain ultrafine grained cams with an increase of 10.3% in the microhardness mean value as compared to that obtained from material with no previous deformation. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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3483 KiB

Open AccessArticle

Modeling the Constitutive Relationship of Al–0.62Mg–0.73Si Alloy Based on Artificial Neural Network

by Ying Han, Shun Yan, Yu Sun and Hua Chen

Metals 2017, 7(4), 114; https://doi.org/10.3390/met7040114 - 26 Mar 2017

Cited by 9 | Viewed by 4835

Abstract

In this work, the hot deformation behavior of 6A02 aluminum alloy was investigated by isothermal compression tests conducted in the temperature range of 683–783 K and strain-rate range of 0.001–1 s⁻¹. According to the obtained true stress–true strain curves, the constitutive [...] Read more.

In this work, the hot deformation behavior of 6A02 aluminum alloy was investigated by isothermal compression tests conducted in the temperature range of 683–783 K and strain-rate range of 0.001–1 s⁻¹. According to the obtained true stress–true strain curves, the constitutive relationship of the alloy was revealed by establishing the Arrhenius-type constitutive model and back-propagation (BP) neural network model. It is found that the flow characteristic of 6A02 aluminum alloy is closely related to deformation temperature and strain rate, and the true stress decreases with increasing temperatures and decreasing strain rates. The hot deformation activation energy is calculated to be 168.916 kJ mol⁻¹. The BP neural network model with one hidden layer and 20 neurons in the hidden layer is developed. The accuracy in prediction of the Arrhenius-type constitutive model and BP neural network model is eveluated by using statistics analysis method. It is demonstrated that the BP neural network model has better performance in predicting the flow stress. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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4037 KiB

Open AccessArticle

Comparison of Hydrostatic Extrusion between Pressure-Load and Displacement-Load Models

by Shengqiang Du, Xiang Zan, Ping Li, Laima Luo, Xiaoyong Zhu and Yucheng Wu

Metals 2017, 7(3), 78; https://doi.org/10.3390/met7030078 - 1 Mar 2017

Cited by 3 | Viewed by 5028

Abstract

Two finite element analysis (FEA) models simulating hydrostatic extrusion (HE) are designed, one for the case under pressure load and another for the case under displacement load. Comparison is made of the equivalent stress distribution, stress state ratio distribution and extrusion pressure between [...] Read more.

Two finite element analysis (FEA) models simulating hydrostatic extrusion (HE) are designed, one for the case under pressure load and another for the case under displacement load. Comparison is made of the equivalent stress distribution, stress state ratio distribution and extrusion pressure between the two models, which work at the same extrusion ratio (R) and the same die angle (2α). A uniform Von-Mises equivalent stress gradient distribution and stress state ratio gradient distribution are observed in the pressure-load model. A linear relationship is found between the extrusion pressure (P) and the logarithm of the extrusion ratio (lnR), and a parabolic relationship between P and 2α, in both models. The P-value under pressure load is smaller than that under displacement load, though at the same R and α, and the difference between the two pressures becomes larger as R and α grow. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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9886 KiB

Open AccessArticle

Hot Deformation Behavior of As-Cast 30Cr2Ni4MoV Steel Using Processing Maps

by Peng Zhou, Qingxian Ma and Jianbin Luo

Metals 2017, 7(2), 50; https://doi.org/10.3390/met7020050 - 9 Feb 2017

Cited by 10 | Viewed by 5025

Abstract

The hot deformation behavior of as-cast 30Cr2Ni4MoV steel was characterized using processing maps in the temperature range 850 to 1200 °C and strain rate range 0.01 to 10 s⁻¹. Based on the obtained flow curves, the power dissipation maps at different [...] Read more.

The hot deformation behavior of as-cast 30Cr2Ni4MoV steel was characterized using processing maps in the temperature range 850 to 1200 °C and strain rate range 0.01 to 10 s⁻¹. Based on the obtained flow curves, the power dissipation maps at different strains were developed and the effect of the strain on the efficiency of power dissipation was discussed in detail. The processing maps at different strains were obtained by superimposing the instability maps on the power dissipation maps. According to the processing map and the metallographic observation, the optimum domain of hot deformation was in the temperature range of 950–1200 °C and strain rate range of 0.03–0.5 s⁻¹, with a peak efficiency of 0.41 at 1100 °C and 0.25 s⁻¹ which were the optimum hot working parameters. Full article

(This article belongs to the Special Issue Advances in Plastic Forming of Metals)

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