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17 pages, 3091 KiB

Open AccessArticle

A Volumetric Heat Source Model for Thermal Modeling of Additive Manufacturing of Metals

by Yabin Yang and Xin Zhou

Metals 2020, 10(11), 1406; https://doi.org/10.3390/met10111406 - 22 Oct 2020

Cited by 11 | Viewed by 3477

Abstract

In additive manufacturing of metallic materials, an accurate description of the thermal histories of the built part is important for further analysis of the distortions and residual stresses, which is a big issue for additively manufactured metal products. In the present paper, a [...] Read more.

In additive manufacturing of metallic materials, an accurate description of the thermal histories of the built part is important for further analysis of the distortions and residual stresses, which is a big issue for additively manufactured metal products. In the present paper, a computationally volumetric heat source model based on a semianalytical thermal modeling approach is proposed. The proposed model is applied to model the thermal response during a selective laser melting (SLM) process. The interaction between the laser and the material is described using a moving volumetric heat source. High computational efficiency can be achieved with considerable accuracy. Several case studies are conducted to examine the accuracy of the proposed model. By comparing with the experimentally measured melt-pool dimensions, it is found that the error between the predictions obtained by the proposed model and the experimental results can be controlled to less than 10%. High computational efficiency can also be achieved for the proposed model. It is shown that for simulating the thermal process of scanning a single layer with the dimension of 2 mm × 2 mm, the calculation can be finished in around 110 s. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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16 pages, 6637 KiB

Open AccessArticle

Achievements of Nearly Zero Earing Defects on SPCC Cylindrical Drawn Cup Using Multi Draw Radius Die

by Rudeemas Jankree and Sutasn Thipprakmas

Metals 2020, 10(9), 1204; https://doi.org/10.3390/met10091204 - 8 Sep 2020

Cited by 9 | Viewed by 3725

Abstract

In recent years, the old-fashioned cylindrical cup shapes are still widely used, and there are many defects which could not be solved yet. In the present research, the classical earing defects, which are mainly caused by the material mechanical property of the anisotropic [...] Read more.

In recent years, the old-fashioned cylindrical cup shapes are still widely used, and there are many defects which could not be solved yet. In the present research, the classical earing defects, which are mainly caused by the material mechanical property of the anisotropic property of the material (R-value), are focused on. The multi draw radius (MDR) deep drawing die is applied and investigated to achieve nearly zero earing defects by encountering the R-value during the deep drawing process. Based on the experiments, in different directions in the sheet plane, the somewhat concurrent plastic deformation could be controlled, and the uniform elongated grain microstructure and uniform strain distributions on the cup wall could be achieved. Therefore, on the basis of these characteristics, the earing defects could be prevented, and the nearly zero earing defects could be achieved. However, to achieve the nearly zero earing defects, the suitable MDR die design relating to the R-value should be strictly considered. In the present research, to apply the MDR die for the medium carbon steel sheet grade SPCC cylindrical drawn cup, the following was recommended: the large draw radius positioned at 45° to the rolling direction and the small draw radius positioned along the plane and at 90° to the rolling direction. Therefore, in the present research, it was originally revealed that the nearly zero earing defects could be successfully performed on the process by using the MDR die application. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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28 pages, 14314 KiB

Open AccessArticle

Thermomechanical Simulations of Residual Stresses and Distortion in Electron Beam Melting with Experimental Validation for Ti-6Al-4V

by Fawaz M. Abdullah, Saqib Anwar and Abdulrahman Al-Ahmari

Metals 2020, 10(9), 1151; https://doi.org/10.3390/met10091151 - 25 Aug 2020

Cited by 13 | Viewed by 3958

Abstract

Electron beam melting (EBM) is a relatively new process in three-dimensional (3D) printing to enable rapid manufacturing. EBM can manufacture metallic parts with thin walls, multi-layers, and complex internal structures that could not otherwise be produced for applications in aerospace, medicine, and other [...] Read more.

Electron beam melting (EBM) is a relatively new process in three-dimensional (3D) printing to enable rapid manufacturing. EBM can manufacture metallic parts with thin walls, multi-layers, and complex internal structures that could not otherwise be produced for applications in aerospace, medicine, and other fields. A 3D transient coupled thermomechanical finite element (FE) model was built to simulate the temperature distribution, distortion, and residual stresses in electron beam additive manufactured Ti-6Al-4V parts. This research enhances the understanding of the EBM-based 3D printing process to achieve parts with lower levels of residual stress and distortion and hence improved quality. The model used a fine mesh in the layer deposition zone, and the mesh size was gradually increased with distance away from the deposits. Then, elements are activated layer by layer during deposition according to the desired material properties. On the top surface, a Gaussian distributed heat flux is used to model the heat source, and the temperature-dependent properties of the powder and solid are also included to improve accuracy. The current simulation has been validated by comparing the FE distortion and temperature results with the experimental results and other reported simulation studies. The residual stress results calculated by the FE analysis were also compared with the previously reported simulation studies on the EBM process. The results showed that the finite element approach can efficiently and accurately predict the temperature field of a part during the EBM process and can easily be extended to other powder bed fusion processes. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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22 pages, 6076 KiB

Open AccessArticle

Prediction and Control Technology of Stainless Steel Quarter Buckle in Hot Rolling

by Hui Li, Chihuan Yao, Jian Shao, Anrui He, Zhou Zhou and Weigang Li

Metals 2020, 10(8), 1060; https://doi.org/10.3390/met10081060 - 6 Aug 2020

Cited by 4 | Viewed by 3280

Abstract

To obtain the good flatness of hot-rolled stainless-steel strips, high-precision shape control has always been the focus of research. In hot rolling, the quadratic wave (centre buckle and edge wave) can usually be controlled effectively. However, the quarter buckle of the strip is [...] Read more.

To obtain the good flatness of hot-rolled stainless-steel strips, high-precision shape control has always been the focus of research. In hot rolling, the quadratic wave (centre buckle and edge wave) can usually be controlled effectively. However, the quarter buckle of the strip is still a challenge to solve. In this paper, a prediction model of roll deflection and material flow is established to study the change rule and control technology of the quarter buckle. The effects of the process parameters on the quarter buckle are analysed quantitatively. The process parameters affect the quarter buckle and the quadratic wave simultaneously. This coupling makes the control of the quarter buckle difficult. The distribution of lateral temperature and the quartic crown of the strip have less effect on the quadratic wave but have a great effect on the quarter buckle. Finally, a new technology for work roll contour is developed to improve the quarter buckle. Through industrial application, the model and the new contour are proved to be effective. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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16 pages, 5838 KiB

Open AccessArticle

Analysis of Forming Parameters Involved in Plastic Deformation of 441 Ferritic Stainless Steel Tubes

by Orlando Di Pietro, Giuseppe Napoli, Matteo Gaggiotti, Roberto Marini and Andrea Di Schino

Metals 2020, 10(8), 1013; https://doi.org/10.3390/met10081013 - 28 Jul 2020

Cited by 4 | Viewed by 2813

Abstract

A welded stainless steel tube is a component used in several industrial applications. Its manufacturing process needs to follow specific requirements based on reference standards. This calls for a predictive analysis able to face some critical issues affecting the forming process. In this [...] Read more.

A welded stainless steel tube is a component used in several industrial applications. Its manufacturing process needs to follow specific requirements based on reference standards. This calls for a predictive analysis able to face some critical issues affecting the forming process. In this paper, a model was adopted taking into account the tube geometrical parameters that was able to describe the deformation process and define the best industrial practices. In this paper, the effect of different process parameters and geometric constraints on ferritic stainless steel pipe deformation is studied by finite element method (FEM) simulations. The model sensitivity to the input parameters is reported in terms of stress and tube thinning. The feasibility of the simulated process is assessed through the comparison of Forming Limit Diagrams. The comparison between the calculated and experimental results proved this approach to be a useful tool in order to predict and properly design industrial deformation processes. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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17 pages, 4587 KiB

Open AccessArticle

Multi Draw Radius Die Design for Increases in Limiting Drawing Ratio

by Wiriyakorn Phanitwong and Sutasn Thipprakmas

Metals 2020, 10(7), 870; https://doi.org/10.3390/met10070870 - 30 Jun 2020

Cited by 14 | Viewed by 6967

Abstract

As a major sheet metal process for fabricating cup or box shapes, the deep drawing process is commonly applied in various industrial fields, such as those involving the manufacture of household utensils, medical equipment, electronics, and automobile parts. The limiting drawing ratio (LDR) [...] Read more.

As a major sheet metal process for fabricating cup or box shapes, the deep drawing process is commonly applied in various industrial fields, such as those involving the manufacture of household utensils, medical equipment, electronics, and automobile parts. The limiting drawing ratio (LDR) is the main barrier to increasing the formability and production rate as well as to decrease production cost and time. In the present research, the multi draw radius (MDR) die was proposed to increase LDR. The finite element method (FEM) was used as a tool to illustrate the principle of MDR based on material flow. The results revealed that MDR die could reduce the non-axisymmetric material flow on flange and the asymmetry of the flange during the deep drawing process. Based on this material flow characteristic, the cup wall stretching and fracture could be delayed. Furthermore, the cup wall thicknesses of the deep drawn parts obtained by MDR die application were more uniform in each direction along the plane, at 45°, and at 90° to the rolling direction than those obtained by conventional die application. In the present research, a proper design for the MDR was suggested to achieve functionality of the MDR die as related to each direction along the plane, at 45°, and at 90° to the rolling direction. The larger draw radius positioned for at 45° to the rolling direction and the smaller draw radius positioned for along the plane and at 90° to the rolling direction were recommended. Therefore, by using proper MDR die application, the drawing ratio could be increased to be 2.75, an increase in LDR of approximately 22.22%. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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16 pages, 7433 KiB

Open AccessArticle

Finite Element Analysis on Ultrasonic Drawing Process of Fine Titanium Wire

by Shen Liu, Xiaobiao Shan, Hengqiang Cao and Tao Xie

Metals 2020, 10(5), 575; https://doi.org/10.3390/met10050575 - 28 Apr 2020

Cited by 7 | Viewed by 4068

Abstract

Ultrasonic drawing is a new technology to reduce the cross-section of a metallic tube, wire or rod by pulling through vibrating dies. The addition of ultrasound is beneficial for reducing the drawing force and enhancing the surface finish of the drawn wire, but [...] Read more.

Ultrasonic drawing is a new technology to reduce the cross-section of a metallic tube, wire or rod by pulling through vibrating dies. The addition of ultrasound is beneficial for reducing the drawing force and enhancing the surface finish of the drawn wire, but the underlying mechanism has not been fully understood. In this paper, an axisymmetric finite element model of the single-pass ultrasonic drawing was established in commercial FEM software based on actual wire length. The multi-linear kinematic hardening (MKINH) model was used to define the elastic and plastic characteristics of titanium. Influences of ultrasonic vibration on the drawing process were investigated in terms of four factors: location of the die, ultrasonic amplitude, drawing velocity, and friction coefficient within the wire-die contact zone. Mises stresses, as well as contact and friction stress, in conventional and ultrasonic drawing conditions, were compared. The results show that larger ultrasonic amplitude and lower drawing velocity contribute to greater drawing force reduction, which agrees with former research. However, their effectiveness is further influenced by the location of the die. When ultrasonic amplitude and drawing speed remain unchanged, the drawing force is minimized when the die locates at the half-wavelength position, while maximized at the quarter-wavelength position. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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23 pages, 9122 KiB

Open AccessArticle

Using DEFORM Software for Determination of Parameters for Two Fracture Criteria on DIN 34CrNiMo6

by Ivana Poláková, Michal Zemko, Martin Rund and Ján Džugan

Metals 2020, 10(4), 445; https://doi.org/10.3390/met10040445 - 28 Mar 2020

Cited by 6 | Viewed by 3476

Abstract

The aim of this study was to calibrate a material model with two fracture criteria that is available in the DEFORM software on DIN 34CrNiMo6. The purpose is to propose a type of simple test that will be sufficient for the determination of [...] Read more.

The aim of this study was to calibrate a material model with two fracture criteria that is available in the DEFORM software on DIN 34CrNiMo6. The purpose is to propose a type of simple test that will be sufficient for the determination of damage parameters. The influence of the quantity of mechanical tests on the accuracy of the fracture criterion was explored. This approach was validated using several tests and simulations of damage in a tube and a round bar. These tests are used in engineering applications for their ease of manufacturing and their strong ability to fracture. The prediction of the time and location of the failure was based on the parameters of the relevant damage model. Normalized Cockroft-Latham and Oyane criteria were explored. The validation involved comparing the results of numerical simulation against the test data. The accuracy of prediction of fracture for various stress states using the criteria was evaluated. Both fracture criteria showed good agreement in terms of the fracture locus, but the Oyane criterion proved more suitable for cases covering larger triaxiality ranges. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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11 pages, 7039 KiB

Open AccessArticle

Finite Element Analysis on the Temperature- Dependent Burst Behavior of Domed 316L Austenitic Stainless Steel Rupture Disc

by Hongbo Zhu, Weipu Xu, Zhiping Luo and Hongxing Zheng

Metals 2020, 10(2), 232; https://doi.org/10.3390/met10020232 - 8 Feb 2020

Cited by 9 | Viewed by 5086

Abstract

As a safety device, a rupture disc instantly bursts as a nonreclosing pressure relief component to minimize the explosion risk once the internal pressure of vessels or pipes exceeds a critical level. In this study, the influence of temperature on the ultimate burst [...] Read more.

As a safety device, a rupture disc instantly bursts as a nonreclosing pressure relief component to minimize the explosion risk once the internal pressure of vessels or pipes exceeds a critical level. In this study, the influence of temperature on the ultimate burst pressure of domed rupture discs made of 316L austenitic stainless steel was experimentally investigated and assessed with finite element analysis. Experimental results showed that the ultimate burst pressure gradually reduced from 6.88 MPa to 5.24 MPa with increasing temperature from 300 K to 573 K, which are consistent with the predicted instability pressures acquired by nonlinear buckling analysis using ABAQUS software. Additionally, it was found that a gradual transition from opening ductile mode to cleavage mode happened with increasing temperature due to more cross slips occurring under serious plastic deformation. The equivalent stress, equivalent strain and strain hardening rates acquired by static analysis were effective at rationalizing the temperature-dependent fracture behavior of the domed rupture discs. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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11 pages, 2874 KiB

Open AccessArticle

Identification of the Flow Properties of a 0.54% Carbon Steel during Continuous Cooling

by Christoph Rößler, David Schmicker, Oleksii Sherepenko, Thorsten Halle, Markus Körner, Sven Jüttner and Elmar Woschke

Metals 2020, 10(1), 104; https://doi.org/10.3390/met10010104 - 9 Jan 2020

Cited by 1 | Viewed by 2912

Abstract

The determinination of material properties is an essential step in the simulation of manufacturing processes. For hot deformation processes, consistently assessed Carreau fluid constitutive model derived in prior works by Schmicker et al. might be used, in which the flow stress is described [...] Read more.

The determinination of material properties is an essential step in the simulation of manufacturing processes. For hot deformation processes, consistently assessed Carreau fluid constitutive model derived in prior works by Schmicker et al. might be used, in which the flow stress is described as a function of the current temperature and the current strain rate. The following paper aims to extend the prior mentioned model by making a distinction, whether the material is being heated or cooled, enhancing the model capabilities to predict deformations within the cooling process. The experimental identifaction of the material parameters is demonstrated for a structural carbon steel with 0.54% carbon content. An approach to derive the flow properties during cooling from the same samples used at heating is presented, which massively reduces the experimental effort in future applications. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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12 pages, 9855 KiB

Open AccessArticle

Effect of Cutting Crystal Directions on Micro-Defect Evolution of Single Crystal γ-TiAl Alloy with Molecular Dynamics Simulation

by Jianhua Li, Ruicheng Feng, Haiyang Qiao, Haiyan Li, Maomao Wang, Yongnian Qi and Chunli Lei

Metals 2019, 9(12), 1278; https://doi.org/10.3390/met9121278 - 28 Nov 2019

Cited by 20 | Viewed by 2994

Abstract

In this work, the distribution and evolution of micro-defect in single crystal γ-TiAl alloy during nanometer cutting is studied by means of molecular dynamics simulation. Nanometer cutting is performed along two typical crystal directions:

[\bar{1} 00]

and [...] Read more.

In this work, the distribution and evolution of micro-defect in single crystal γ-TiAl alloy during nanometer cutting is studied by means of molecular dynamics simulation. Nanometer cutting is performed along two typical crystal directions:

[\bar{1} 00]

and

[\bar{1} 01]

. A machined surface, system potential energy, amorphous layer, lattice deformation and the formation mechanism of chip are discussed. The results indicate that the intrinsic stacking fault, dislocation loop and atomic cluster are generated below the machined surface along the cutting crystal directions. In particular, the Stacking Fault Tetrahedron (SFT) is generated inside the workpiece when the cutting crystal direction is along

[\bar{1} 00]

. However, a “V”-shape dislocation loop is formed in the workpiece along

[\bar{1} 01]

. Furthermore, atomic distribution of the machined surface indicates that the surface quality along

[\bar{1} 00]

is better than that along

[\bar{1} 01]

. In a certain range, the thickness of the amorphous layer increases gradually with the rise of cutting force during nanometric cutting process. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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16 pages, 7337 KiB

Open AccessArticle

A Phenomenological Mechanical Material Model for Precipitation Hardening Aluminium Alloys

by Hannes Fröck, Lukas Vincent Kappis, Michael Reich and Olaf Kessler

Metals 2019, 9(11), 1165; https://doi.org/10.3390/met9111165 - 29 Oct 2019

Cited by 5 | Viewed by 4434

Abstract

Age hardening aluminium alloys obtain their strength by forming precipitates. This precipitation-hardened state is often the initial condition for short-term heat treatments, like welding processes or local laser heat treatment to produce tailored heat-treated profiles (THTP). During these heat treatments, the strength-increasing precipitates [...] Read more.

Age hardening aluminium alloys obtain their strength by forming precipitates. This precipitation-hardened state is often the initial condition for short-term heat treatments, like welding processes or local laser heat treatment to produce tailored heat-treated profiles (THTP). During these heat treatments, the strength-increasing precipitates are dissolved depending on the maximum temperature and the material is softened in these areas. Depending on the temperature path, the mechanical properties differ between heating and cooling at the same temperature. To model this behavior, a phenomenological material model was developed based on the dissolution characteristics and experimental flow curves were developed depending on the current temperature and the maximum temperature. The dissolution characteristics were analyzed by calorimetry. The mechanical properties at different temperatures and peak temperatures were recorded by thermomechanical analysis. The usual phase transformation equations in the Finite Element Method (FEM) code, which were developed for phase transformation in steels, were used to develop a phenomenological model for the mechanical properties as a function of the relevant heat treatment parameters. This material model was implemented for aluminium alloy 6060 T4 in the finite element software LS-DYNA (Livermore Software Technology Corporation). Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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15 pages, 6456 KiB

Open AccessArticle

Analysis of Melt-Pool Behaviors during Selective Laser Melting of AISI 304 Stainless-Steel Composites

by Daniyal Abolhasani, S. M. Hossein Seyedkashi, Namhyun Kang, Yang Jin Kim, Young Yun Woo and Young Hoon Moon

Metals 2019, 9(8), 876; https://doi.org/10.3390/met9080876 - 8 Aug 2019

Cited by 27 | Viewed by 5450

Abstract

The melt-pool behaviors during selective laser melting (SLM) of Al₂O₃-reinforced and a eutectic mixture of Al₂O₃-ZrO₂-reinforced AISI 304 stainless-steel composites were numerically analyzed and experimentally validated. The thermal analysis results show that the [...] Read more.

The melt-pool behaviors during selective laser melting (SLM) of Al₂O₃-reinforced and a eutectic mixture of Al₂O₃-ZrO₂-reinforced AISI 304 stainless-steel composites were numerically analyzed and experimentally validated. The thermal analysis results show that the geometry of the melt pool is significantly dependent on reinforcing particles, owing to the variations in the melting point and the thermal conductivity of the powder mixture. With the use of a eutectic mixture of Al₂O₃-ZrO₂ instead of an Al₂O₃ reinforcing particle, the maximum temperature of the melt pool was increased. Meanwhile, a negligible corresponding relationship was observed between the cooling rate of both reinforcements. Therefore, it was identified that the liquid lifetime of the melt pool has the effect on the melting behavior, rather than the cooling rate, and the liquid lifetime increases with the eutectic ratio of Al₂O₃-ZrO₂ reinforcement. The temperature gradient at the top surface reduces with the use of an Al₂O₃-ZrO₂ reinforcement particle due to the wider melt pool. Inversely, the temperature gradient in the thickness direction increases with the use of an Al₂O₃-ZrO₂ reinforcement particle. The results of melt-pool behaviors will provide a deep understanding of the effect of reinforcing particles on the dimensional accuracies and properties of fabricated AISI 304 stainless-steel composites. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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18 pages, 2815 KiB

Open AccessArticle

Optimization of the Continuous Galvanizing Heat Treatment Process in Ultra-High Strength Dual Phase Steels Using a Multivariate Model

by Patricia Costa, Gerardo Altamirano, Armando Salinas, David S. González-González and Frank Goodwin

Metals 2019, 9(6), 703; https://doi.org/10.3390/met9060703 - 21 Jun 2019

Cited by 13 | Viewed by 6371

Abstract

The main process variables to produce galvanized dual phase (DP) steel sheets in continuous galvanizing lines are time and temperature of intercritical austenitizing (t_IA and T_IA), cooling rate (CR₁) after intercritical austenitizing, holding time at the [...] Read more.

The main process variables to produce galvanized dual phase (DP) steel sheets in continuous galvanizing lines are time and temperature of intercritical austenitizing (t_IA and T_IA), cooling rate (CR₁) after intercritical austenitizing, holding time at the galvanizing temperature (t_G) and finally the cooling rate (CR₂) to room temperature. In this research work, the effects of CR₁, t_G and CR₂ on the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of cold rolled low carbon steel were investigated by applying an experimental central composite design and a multivariate regression model. A multi-objective optimization and the Pareto Front were used for the optimization of the continuous galvanizing heat treatments. Typical thermal cycles applied for the production of continuous galvanized AHSS-DP strips were simulated in a quenching dilatometer using miniature tensile specimens. The experimental results of UTS, YS and EL were used to fit the multivariate regression model for the prediction of these mechanical properties from the processing parameters (CR₁, t_G and CR₂). In general, the results show that the proposed multivariate model correctly predicts the mechanical properties of UTS, YS and %EL for DP steels processed under continuous galvanizing conditions. Furthermore, it is demonstrated that the phase transformations that take place during the optimized t_G (galvanizing time) play a dominant role in determining the values of the mechanical properties of the DP steel. The production of hot-dip galvanized DP steels with a minimum tensile strength of 1100 MPa is possible by applying the proposed methodology. The results provide important scientific and technological knowledge about the annealing/galvanizing thermal cycle effects on the microstructure and mechanical properties of DP steels. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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11 pages, 3951 KiB

Open AccessArticle

Influence of Niobium or Molybdenum Addition on Microstructure and Tensile Properties of Nickel-Chromium Alloys

by Marisa Aparecida de Souza, Bárbara de Oliveira Fiorin, Tomaz Manabu Hashimoto, Ana Paula Rosifini, Carlos Angelo Nunes, Carlos Antônio Reis Pereira Baptista and Alfeu Saraiva Ramos

Metals 2019, 9(5), 589; https://doi.org/10.3390/met9050589 - 22 May 2019

Cited by 1 | Viewed by 4197

Abstract

This work discusses on influence of niobium or molybdenum addition on microstructure and tensile properties of NiCr-based dental alloys. In this regard, the Ni-24Cr-8Nb, Ni-22Cr-10Nb and Ni-20Cr-12Nb (wt. %) alloys produced by arc melting process. To compare the typical Ni-22Cr-10Mo dental alloy was [...] Read more.

This work discusses on influence of niobium or molybdenum addition on microstructure and tensile properties of NiCr-based dental alloys. In this regard, the Ni-24Cr-8Nb, Ni-22Cr-10Nb and Ni-20Cr-12Nb (wt. %) alloys produced by arc melting process. To compare the typical Ni-22Cr-10Mo dental alloy was also produced. These ternary alloys were analyzed by chemical analyses, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive spectrometry (EDS), thermogravimetric analysis (TG), Vickers hardness and tensile tests. Although the mass losses of the samples during arc melting, the optical emission spectrometry showed that the initial compositions were kept. The Ni-22Cr-10Mo alloy produced a matrix of Ni_ss (ss—solid solution), whereas Ni₃Nb disperse in a Ni_ss matrix was also identified in Ni-Cr-Nb alloys. Excepting for the Ni-22Cr-10Nb alloy with mass gain of 0.23%, the as-cast Ni-Cr alloys presented mass gains close to 0.4% after heating up to 1000 °C under synthetic airflow. The hardness values, the modulus of elasticity, yield strength and ultimate tensile strength have enhanced, whereas the ductility was reduced with increasing niobium addition of up to 12 wt.-%.The Ni-22Cr-10Mo alloy presented an intergranular fracture mechanism containing deep dimples and quasi-cleavage planes, whereas the shallow dimples were identified on fracture surface of the as-cast Nb-richer Ni-Cr alloys due to the presence of higher Ni₃Nb amounts. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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16 pages, 7373 KiB

Open AccessArticle

Fracture Toughness Calculation Method Amendment of the Dissimilar Steel Welded Joint Based on 3D XFEM

by Yuwen Qian and Jianping Zhao

Metals 2019, 9(5), 509; https://doi.org/10.3390/met9050509 - 30 Apr 2019

Cited by 6 | Viewed by 4410

Abstract

The dissimilar steel welded joint is divided into three pieces, parent material–weld
metal–parent material, by the integrity identification of BS7910-2013. In reality, the undermatched
welded joint geometry is dierent: parent material–heat aected zone (HAZ)–fusion line–weld metal.
A combination of the CF62 (parent material) [...] Read more.

The dissimilar steel welded joint is divided into three pieces, parent material–weld
metal–parent material, by the integrity identification of BS7910-2013. In reality, the undermatched
welded joint geometry is dierent: parent material–heat aected zone (HAZ)–fusion line–weld metal.
A combination of the CF62 (parent material) and E316L (welding rod) was the example undermatched
welded joint, whose geometry was divided into four pieces to investigate the fracture toughness of the
joint by experiments and the extended finite element method (XFEM) calculation. The experimental
results were used to change the fracture toughness of the undermatched welded joint, and the XFEM
results were used to amend the fracture toughness calculation method with a new definition of the
crack length. The research results show that the amendment of the undermatched welded joint
geometry expresses more accuracy of the fracture toughness of the joint. The XFEM models were
verified as valid by the experiment. The amendment of the fracture toughness calculation method
expresses a better fit by the new definition of the crack length, in accordance with the crack route
simulated by the XFEM. The results after the amendment coincide with the reality in engineering. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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19 pages, 15642 KiB

Open AccessArticle

Process Parameters Decision to Optimization of Cold Rolling-Beating Forming Process through Experiment and Modelling

by Long Li, Yan Li, Mingshun Yang and Tong Tong

Metals 2019, 9(4), 405; https://doi.org/10.3390/met9040405 - 2 Apr 2019

Cited by 3 | Viewed by 3225

Abstract

The cold roll-beating forming (CRBF) process is a particular cold plastic bulk forming technology for metals that is adequate for shaping the external teeth of important parts. The process parameters of the CRBF process were studied in this work to improve the process [...] Read more.

The cold roll-beating forming (CRBF) process is a particular cold plastic bulk forming technology for metals that is adequate for shaping the external teeth of important parts. The process parameters of the CRBF process were studied in this work to improve the process performance. Of the CRBF process characteristics, the forming forces, tooth profile angle, surface roughness, and forming efficiency were selected as the target indices to describe the process performance. Single tooth experimental tests of ASTM 1045 steel were conducted with different roll-beating modes, spindle rotation speeds, and feed speeds. Using analysis of variance (ANOVA) and regression analysis, the influence of the process parameters in each index was investigated, and regression models of each index were established. Then, the linear weighted sum method and compound entropy weight method were used to determine the process parameters for multi-objective optimization. The results show that the impact capacity and optimum value range of the process parameters vary in different indices, and that, to achieve the comprehensive optimum effect of a small forming force, high product quality, and high forming efficiency, the optimal process parameter combination is the up-beating mode, a spindle rotation speed of 801 r/min, and a feed speed of 960 mm/min. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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18 pages, 11791 KiB

Open AccessArticle

Numerical Simulation of Three-Dimensional Mesoscopic Grain Evolution: Model Development, Validation, and Application to Nickel-Based Superalloys

by Zhao Guo, Jianxin Zhou, Yajun Yin, Xu Shen and Xiaoyuan Ji

Metals 2019, 9(1), 57; https://doi.org/10.3390/met9010057 - 9 Jan 2019

Cited by 5 | Viewed by 3946

Abstract

The mesoscopic grain model is a multiscale model which takes into account both the dendrite growth mechanism and the vast numerical computation of the actual castings. Due to the pursuit of efficient computation, the mesoscopic grain calculation accuracy is lower than that of [...] Read more.

The mesoscopic grain model is a multiscale model which takes into account both the dendrite growth mechanism and the vast numerical computation of the actual castings. Due to the pursuit of efficient computation, the mesoscopic grain calculation accuracy is lower than that of dendrite growth model. Improving the accuracy of mesoscopic grain model is a problem to be solved urgently. In this study, referring to the calculation method of solid fraction in microscopic dendrite growth model, a cellular automata model of 3D mesoscopic grain evolution for solid fraction calculated quantitatively at the scale of cell is developed. The developed model and algorithm validation for grain growth simulation is made by comparing the numerical results with the benchmark experimental data and the analytical predictions. The results show that the 3D grain envelopes simulated by the developed model and algorithm are coincident with the shape predicted by the analytical model to a certain extent. Then, the developed model is applied to the numerical simulation of solidification process of nickel-based superalloys, including equiaxed and columnar dendritic grain growth. Our results show good agreement with the related literature. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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14 pages, 3716 KiB

Open AccessArticle

Atomistic Simulations of Pure Tin Based on a New Modified Embedded-Atom Method Interatomic Potential

by Won-Seok Ko, Dong-Hyun Kim, Yong-Jai Kwon and Min Hyung Lee

Metals 2018, 8(11), 900; https://doi.org/10.3390/met8110900 - 3 Nov 2018

Cited by 32 | Viewed by 5165

Abstract

A new interatomic potential for the pure tin (Sn) system is developed on the basis of the second-nearest-neighbor modified embedded-atom-method formalism. The potential parameters were optimized based on the force-matching method utilizing the density functional theory (DFT) database of energies and forces of [...] Read more.

A new interatomic potential for the pure tin (Sn) system is developed on the basis of the second-nearest-neighbor modified embedded-atom-method formalism. The potential parameters were optimized based on the force-matching method utilizing the density functional theory (DFT) database of energies and forces of atomic configurations under various conditions. The developed potential significantly improves the reproducibility of many fundamental physical properties compared to previously reported modified embedded-atom method (MEAM) potentials, especially properties of the β phase that is stable at the ambient condition. Subsequent free energy calculations based on the quasiharmonic approximation and molecular-dynamics simulations verify that the developed potential can be successfully applied to study the allotropic phase transformation between α and β phases and diffusion phenomena of pure tin. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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16 pages, 9640 KiB

Open AccessArticle

Mathematical Model for Prediction and Optimization of Weld Bead Geometry in All-Position Automatic Welding of Pipes

by Baoyi Liao, Yonghua Shi, Yanxin Cui, Shuwan Cui, Zexin Jiang and Yaoyong Yi

Metals 2018, 8(10), 756; https://doi.org/10.3390/met8100756 - 25 Sep 2018

Cited by 11 | Viewed by 4975

Abstract

In this study all-position automatic tungsten inert gas (TIG) welding was exploited to enhance quality and efficiency in the welding of copper-nickel alloy pipes. The mathematical models of all-position automatic TIG weld bead shapes were conducted by the response surface method (RSM) on [...] Read more.

In this study all-position automatic tungsten inert gas (TIG) welding was exploited to enhance quality and efficiency in the welding of copper-nickel alloy pipes. The mathematical models of all-position automatic TIG weld bead shapes were conducted by the response surface method (RSM) on the foundation of central composition design (CCD). The statistical models were verified for their significance and adequacy by analysis of variance (ANOVA). In addition, the influences of welding peak current, welding velocity, welding duty ratio, and welding position on weld bead geometry were investigated. Finally, optimal welding parameters at the welding positions of 0° to 180° were determined by using RSM. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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18 pages, 3805 KiB

Open AccessTechnical Note

Performance of Optimization Algorithms in the Model Fitting of the Multi-Scale Numerical Simulation of Ductile Iron Solidification

by Eva Anglada, Antton Meléndez, Alejandro Obregón, Ester Villanueva and Iñaki Garmendia

Metals 2020, 10(8), 1071; https://doi.org/10.3390/met10081071 - 8 Aug 2020

Cited by 5 | Viewed by 3144

Abstract

The use of optimization algorithms to adjust the numerical models with experimental values has been applied in other fields, but the efforts done in metal casting sector are much more limited. The advances in this area may contribute to get metal casting adjusted [...] Read more.

The use of optimization algorithms to adjust the numerical models with experimental values has been applied in other fields, but the efforts done in metal casting sector are much more limited. The advances in this area may contribute to get metal casting adjusted models in less time improving the confidence in their predictions and contributing to reduce tests at laboratory scale. This work compares the performance of four algorithms (compass search, NEWUOA, genetic algorithm (GA) and particle swarm optimization (PSO)) in the adjustment of the metal casting simulation models. The case study used in the comparison is the multiscale simulation of the hypereutectic ductile iron (SGI) casting solidification. The model fitting criteria is the value of the tensile strength. Four different situations have been studied: model fitting based in 2, 3, 6 and 10 variables. Compass search and PSO have succeeded in reaching the error target in the four cases studied, while NEWUOA and GA have failed in some cases. In the case of the deterministic algorithms, compass search and NEWUOA, the use of a multiple random initial guess has been clearly beneficious. Full article

(This article belongs to the Special Issue Numerical Modelling and Simulation of Metal Processing)

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