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

Deadline for manuscript submissions: closed (20 February 2022) | Viewed by 28077

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Prof. Dr. Dong Won Jung

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School of Mechanical Engineering, Jeju National University, Jeju 63243, Republic of Korea
Interests: constitutive modeling at hot working conditions; cold- and hot-roll forming; incremental sheet forming; cold and hot stamping; computational modeling for metal forming applications; formability in sheet metal forming; friction stir welding
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Special Issue Information

Dear Colleagues,

We would like to bring your attention to a Special Issue of Materials on "Recent Advances in Metal Forming Technology". Plastic deformation is always a crucial part of the metal forming process. By achieving proper plastic deformation in the work material, the formed parts tend to be a better product in terms of quality and reliability. Producing the most efficient and economical manufacturing process in any forming division is one of the most challenging tasks. Research challenges in metal forming process remain the same and are growing day-by-day in terms of minimizing product defects and waste management.

The purpose of this Special Issue is to collect valuable research articles in which improved techniques are presented with significant contributions to the forming process. The goal of this issue is to improve the understanding of the forming process by presenting both positive and negative aspects. For example, by explaining the advantages and disadvantages of procedures involved in the forming process, it will allow the reader to understand more about the process and will help them to think and develop more optimized procedures in the near future. As research about metal forming methods never ends, some aspects will always require continuous improvements. Topics of interest include but are not limited to the following:

Recent developments in the metal forming process
Constitutive modeling at hot working conditions
Optimized computational procedures for metal forming applications
Formability improvement in incremental sheet forming process
Hybrid metal forming process
Spring back modeling methods
Optimization procedures of forming process
Damage models (cold and hot)
Tool wear and fracture

I am looking forward to your contributions.

Prof. Dr. Dong Won Jung
Guest Editor

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Keywords

metal forming process
material modeling
formability improvement
spring back and fracture model estimation
optimization procedures

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Published Papers (10 papers)

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Research

18 pages, 5933 KiB

Open AccessArticle

Constitutive Model Parameter Identification Based on Optimization Method and Formability Analysis for Ti6Al4V Alloy

by Xuewen Chen, Bo Zhang, Yuqing Du, Mengxiang Liu, Rongren Bai, Yahui Si, Bingqi Liu, Dong-Won Jung and Akiyoshi Osaka

Materials 2022, 15(5), 1748; https://doi.org/10.3390/ma15051748 - 25 Feb 2022

Cited by 7 | Viewed by 2360

Abstract

Titanium alloy is widely applied in aerospace, medical, shipping and other fields due to its high specific strength and low density. The purpose of this study was to analyze the formability of Ti6Al4V alloys at elevated temperatures. An accurate constitutive model is the basic condition for accurately simulating the plastic forming of materials, and it is an important basis for optimizing the parameters of the hot forging forming process. In this study, the optimization algorithm was used to accurately identify the high-temperature constitutive model parameters of Ti6Al4V titanium alloy, and the hot working diagram was established to optimize the hot forming process parameters. The optimal forming conditions of Ti6Al4V titanium alloy are given. Ti6Al4V alloy was subjected to high-temperature compression tests at 800–1000 °C and at strain rates of 0.01–5 s⁻¹ on a Gleeble-1500D thermal/mechanical simulation machine. Each parameter of the Hansel–Spittel constitutive model was taken as an independent variable, and the accumulated error between the stress calculated by the constitutive model and the stress obtained by experimentation was used as an objective function. Based on response surface methodology, an inverse optimization method for identifying the parameters of the high-temperature constitutive model of Ti6Al4V alloy is proposed in this paper. An orthogonal test design was adopted to obtain sample point data, and a third-order response surface approximate model was established. The genetic algorithm (GA) was applied to reversely optimize the parameters of the constitutive model. To verify the accuracy of the optimized constitutive model, the average absolute relative error (AARE) and correlation coefficient (R) were used to evaluate the reliability of optimized constitutive model. The R value of the model was 0.999, and the AARE value was 0.048, respectively, indicating that the established high-temperature constitutive model for Ti6Al4V alloy has good calculation accuracy. The flow stress behavior of the material could be accurately delineated. Meanwhile, in order to study the formability of Ti6Al4V alloy, the hot processing map of the alloy, based on a dynamic material model, was established in this paper. The optimum hot working domains of the Ti6Al4V alloy were determined within 840–920 °C/0.01–0.049 s⁻¹ and 940–980 °C/0.11–1.65 s⁻¹; the hot processing map was verified in combination with the microstructure, and the fine and equiaxed grains and a large amount of β phase could be found at 850 °C/0.01 s⁻¹. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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20 pages, 22831 KiB

Open AccessArticle

Toolpath Planning and Generation for Multi-Stage Incremental Forming Based on Stretching Angle

by Hu Zhu, Guixi Cheng and Dongwon Jung

Materials 2021, 14(17), 4818; https://doi.org/10.3390/ma14174818 - 25 Aug 2021

Cited by 8 | Viewed by 1993

Abstract

To solve the problems that exist in the multi-stage forming of the straight wall parts, such as the sheet fracture, uneven thickness distribution, and the stepped feature sinking, a new forming toolpath planning and generation method for the multi-stage incremental forming was proposed based on the stretching angle. In this method, the parallel planes that were used for forming toolpath generation were constructed by using the stretching angle so that the distances between the parallel planes and the forming angles were gradually reduced. This makes the sheet material flow become changed and the thickness thinning is relieved. The software system for the toolpath generation was developed by using C++, VC++, and OpenGL library. In order to verify the feasibility of the proposed method, numerical simulation and forming experiments were carried out for the single stage forming, the traditional multi-stage forming, and multi-stage forming based on the proposed forming toolpath, using 1060 aluminum sheets. The comparative analysis of the thickness distribution, profile curve, strain curve, and sheet material flow shows that the proposed method is feasible, and the profile dimension accuracy is better, the thickness distribution is more uniform, and the sinking and bulging are significantly reduced. The formed sheet part with the stretching angle of 15° has higher dimensional accuracy, smaller bottom subsidence, and larger thickness than that of the stretching angle 5°. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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15 pages, 11148 KiB

Open AccessArticle

The Influence of Sheet Tilting on Forming Quality in Single Point Incremental Forming

by Hu Zhu, Yang Wang, Yibo Liu and Dongwon Jung

Materials 2021, 14(14), 3907; https://doi.org/10.3390/ma14143907 - 13 Jul 2021

Cited by 3 | Viewed by 2036

Abstract

In the CNC incremental forming process, the sheet tilting method can be used to realize the non-fracture forming of a surface with large forming angles. However, the forming effect of the formed part will have big differences when the inclined angle of the sheet is different. Therefore, four different tilted sheets with inclined angles of 15°, 20°, 25°, and 30° were used to study the influence of sheet tilting on forming quality by using 1060 Aluminum sheet as the forming sheet in single point CNC incremental forming. First, the influence of four different inclined angles of the sheet on the overall thickness distribution, plastic strain, and material flow of the formed part was studied by using numerical simulation. Then, the influence of four different inclined angles of sheets on the profile accuracy and thickness thinning rate of the formed part was studied through single point incremental forming experiments. The research results show that sheet tilting has little effect on the profile accuracy of the formed part, but has a great influence on the material flow, plastic strain, and thickness distribution. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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21 pages, 11452 KiB

Open AccessArticle

Study on the Time-Dependent Mechanical Behavior and Springback of Magnesium Alloy Sheet (AZ31B) in Warm Conditions

by Jae-Hyeong YU and Chang-Whan Lee

Materials 2021, 14(14), 3856; https://doi.org/10.3390/ma14143856 - 9 Jul 2021

Cited by 6 | Viewed by 2119

Abstract

In this study, the time-dependent mechanical behavior of the magnesium alloy sheet (AZ31B) was investigated through the creep and stress relaxation tests with respect to the temperature and pre-strain. The microstructure changes during creep and stress relaxation were investigated. As the tensile deformation increased in the material, twinning and dynamic recrystallization occurred, especially after the plastic instability. As a result, AZ31B showed lower resistance to creep and stress relaxation due to dynamic recrystallization. Additionally, time-dependent springback characteristics in the V- and L-bending processes concerning the holding time and different forming conditions were investigated. We analyzed changes of microstructure at each forming temperature and process. The uniaxial tensile creep test was conducted to compare the microstructures in various pre-strain conditions with those at the secondary creep stage. For the bending process, the change of the microstructure after the forming was compared to that with punch holding maintained for 1000 s after forming. Due to recrystallization, with the holding time in the die set of 60 s, the springback angle decreased by nearly 70%. Increased holding time in the die set resulted in a reduced springback angle. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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15 pages, 7580 KiB

Open AccessEditor’s ChoiceArticle

The Parameters Identification of High-Temperature Constitutive Model Based on Inverse Optimization Method and 3D Processing Map of Cr8 Alloy Steel

by Xuewen Chen, Tingting Lian, Bo Zhang, Yuqing Du, Kexue Du, Bingqi Liu, Zhipeng Li, Xuanhe Tian and Dong-Won Jung

Materials 2021, 14(9), 2216; https://doi.org/10.3390/ma14092216 - 26 Apr 2021

Cited by 4 | Viewed by 2228

Abstract

As a novel kind of cold roller steel, Cr8 alloy steel has the characteristics of high hardness, high wear resistance and good toughness, which can effectively prolong the service life of the roller that is an important part of the steel rolling mill. How to accurately define the constitutive model parameters of metal materials is the major problem, because it seriously affects the accuracy of numerical simulation results of the roller hot forming process. In the study of Cr8 alloy steel’s thermal deformation behavior of the present paper, the high temperature compression test was done on a Gleebel-1500D thermal/force simulation testing machine. A novel method of parameter identification was proposed based on inverse optimization. The Hansel–Spittel constitutive model was established by using the inverse optimization method. To carry out the verification on the accuracy of the established constitutive model, the predicted flow-stress of constitutive model was made a contrast to the experimental flow-stress, and the standard statistical parameters were also applied to further evaluation. The results showed a relatively high prediction accuracy of the Hansel–Spittel constitutive model based on the inverse optimization algorithm. Meanwhile, to obtain optimal parameters of Cr8 alloy steel in the thermal processing, 3D thermal processing maps concerning strain-rate, strain and temperature were built based on the dynamic material model. According to the 3D processing map, the most adequate thermal processing parameters of Cr8 alloy steel were obtianed as follows: strain 0.2–0.4, strain-rate 0.05–0.005 s⁻¹, temperature 1100–1150 °C. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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15 pages, 5902 KiB

Open AccessArticle

Design and Mechanical Compatibility of Nylon Bionic Cancellous Bone Fabricated by Selective Laser Sintering

by Xuewen Chen, Tingting Lian, Bo Zhang, Yuqing Du, Kexue Du, Nan Xiang, Dong-Won Jung, Guangxin Wang and Akiyoshi Osaka

Materials 2021, 14(8), 1965; https://doi.org/10.3390/ma14081965 - 14 Apr 2021

Cited by 11 | Viewed by 2524

Abstract

In order to avoid the stress shielding phenomenon in orthopedic bionic bone implantation, it is necessary to consider the design of mechanical compatible implants imitating the host bone. In this study, we developed a novel cancellous bone structure design method aimed at ensuring the mechanical compatibility between the bionic bone and human bone by means of computer-aided design (CAD) and finite element analysis technology (specifically, finite element modeling (FEM)). An orthogonal lattice model with volume porosity between 59% and 96% was developed by means of CAD. The effective equivalent elastic modulus of a honeycomb structure with square holes was studied by FEM simulation. With the purpose of verifying the validity of the cancellous bone structure design method, the honeycomb structure was fabricated by selective laser sintering (SLS) and the actual equivalent elastic modulus of the honeycomb structure was measured with a uniaxial compression test. The experimental results were compared with the FEM values and the predicted values. The results showed that the stiffness values of the designed structures were within the acceptable range of human cancellous bone of 50–500 MPa, which was similar to the stiffness values of human vertebrae L1 and L5. From the point of view of mechanical strength, the established cellular model can effectively match the elastic modulus of human vertebrae cancellous bone. The functional relationship between the volume porosity of the nylon square-pore honeycomb structure ranging from 59% to 96% and the effective elastic modulus was established. The effect of structural changes related to the manufacture of honeycomb structures on the equivalent elastic modulus of honeycomb structures was studied quantitatively by finite element modeling. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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26 pages, 25953 KiB

Open AccessArticle

Formability and Failure Evaluation of AA3003-H18 Sheets in Single-Point Incremental Forming Process through the Design of Experiments

by Mohanraj Murugesan and Dong Won Jung

Materials 2021, 14(4), 808; https://doi.org/10.3390/ma14040808 - 8 Feb 2021

Cited by 18 | Viewed by 3167

Abstract

The single-point incremental forming process (SPIF) is one of the emerging manufacturing methods because of its flexibility in producing the desired complex shapes with higher formability at low-cost compared to traditional sheet forming methods. In this research work, we experimentally investigate the forming process to determine the influence of process parameters and their contribution to enhancing the formability without causing a fracture by combining the design of experiments (DOE), grey relational analysis (GRA), and statistical analysis of variance (ANOVA). The surface morphology and the energy dispersive X-ray spectroscopy (EDS) method are used to perform elemental analysis and examine the formed parts during three forming stages. The DOE procedure, a central composite design with a face-centered option, is devised for AA3003-H18 Al alloy sheet for modeling the real-time experiments. The response surface methodology (RSM) approach is adopted to optimize the forming parameters and recognize the optimal test conditions. The statistically developed model is found to have agree with the test measurements. The prediction model’s capability in

R^{2}

is computed as 0.8931, indicating that the fitted regression model adequately aligns with the estimated grey relational grade (GRG) data. Other statistical parameters, such as root mean square error (RMSE) and average absolute relative error (AARE), are estimated as 0.0196 and 2.78%, respectively, proving the proposed regression model’s overall closeness to the measured data. In addition, the prediction error range is identified as −0.05 to 0.05, which is significantly lower and the residual data are distributed normally in the design space with variance and mean of 3.3748 and −0.1232, respectively. ANOVA is performed to understand the adequacy of the proposed model and the influence of the input factors on the response variable. The model parameters, including step size, feed rate, interaction effect of tool radius and step size, favorably influence the response variable. The model terms X₂ (0.020 and 11.30), X₃ (0.018 and 12.16), and X₁X₂ (0.026 and 9.72) are significant in terms of p-value and F-value, respectively. The microstructural inspection shows that the thinning behavior tends to be higher as forming depth advances to its maximum; the deformation is uniform and homogeneous under the predefined test conditions. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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19 pages, 43847 KiB

Open AccessArticle

Experimental and Numerical Investigation of AA5052-H32 Al Alloy with U-Profile in Cold Roll Forming

by Mohanraj Murugesan, Muhammad Sajjad and Dong Won Jung

Materials 2021, 14(2), 470; https://doi.org/10.3390/ma14020470 - 19 Jan 2021

Cited by 15 | Viewed by 3949

Abstract

The cold roll forming process is broadly used to produce a specific shape of cold-roll formed products for their applications in automobiles, aerospace, shipbuilding, and construction sectors. Moreover, a proper selection of strip thickness and forming speed to avoid fracture is most important for manufacturing a quality product. This research aims to investigate the presence of longitudinal bow, the reason behind flange height deviation, spring-back, and identification of thinning location in the cold roll-forming of symmetrical short U-profile sheets. A room temperature tensile test is performed for the commercially available AA5052–H32 Al alloy sheets using Digital Image Correlation (DIC) technique, which allows complete displacement and strain data information at each time-step. The material properties are estimated from the digital images using correlation software for tested samples; the plastic strain ratios are also calculated from samples at 0°, 45°, and 90° to the rolling direction. The tested sample’s surface morphology and the elemental analysis are conducted using scanning electron microscopy (SEM) method and energy-dispersive X-ray spectroscopy (EDS) analytical technique combined with element mapping analysis, respectively. The cold roll forming experiments are systematically carried out, and then finite element analysis is utilized to correlate the experiment with the model. The performed cold roll forming numerical model outcome indicates a good agreement with the experimental measurements. Overall, the presented longitudinal strain was observed to influence the geometry profile. The spring-back is also noticed at the profile tail end and is more pronounced at high forming speed with lower strip thickness. Conversely, while the forming speed is varied, the strain and stress variations are observed to be insignificant, and the similar results also are recognized for the thinning behavior. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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16 pages, 7056 KiB

Open AccessArticle

Tool Path Design of the Counter Single Point Incremental Forming Process to Decrease Shape Error

by Kyu-Seok Jung, Jae-Hyeong Yu, Wan-Jin Chung and Chang-Whan Lee

Materials 2020, 13(21), 4719; https://doi.org/10.3390/ma13214719 - 22 Oct 2020

Cited by 19 | Viewed by 2825

Abstract

Incremental sheet metal forming can manufacture various sheet metal products without a dedicated punch and die set. In this study, we developed a two-stage incremental forming process to decrease shape errors in the conventional incremental forming process. The forming process was classified into the first single point incremental forming (1st SPIF) process for forming a product and the counter single point incremental forming (counter SPIF) process to decrease shape error. The counter SPIF gives bending deformation in the opposite direction. Furthermore, the counter SPIF compensates for shape errors, such as section deflection, skirt spring-back, final forming height, and round. The tool path of the counter SPIF has been optimized through a relatively simple optimization method by modifying the tool path of the previous step. The tool path of the 1st SPIF depends on the geometry of the product. An experiment was performed to form a circular cup shape to verify the proposed tool path of the 1st and counter SPIF. The result confirmed that the shape error decreased when compared to the conventional SPIF. For the application, the ship-hull geometry was adopted. Experimental results demonstrated the feasibility of the two-stage incremental forming process. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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18 pages, 6344 KiB

Open AccessArticle

Microstructural, Tribology and Corrosion Properties of Optimized Fe₃O₄-SiC Reinforced Aluminum Matrix Hybrid Nano Filler Composite Fabricated through Powder Metallurgy Method

by Negin Ashrafi, M. A. Azmah Hanim, Masoud Sarraf, S. Sulaiman and Tang Sai Hong

Materials 2020, 13(18), 4090; https://doi.org/10.3390/ma13184090 - 15 Sep 2020

Cited by 24 | Viewed by 3272

Abstract

Hybrid reinforcement’s novel composite (Al-Fe₃O₄-SiC) via powder metallurgy method was successfully fabricated. In this study, the aim was to define the influence of SiC-Fe₃O₄ nanoparticles on microstructure, mechanical, tribology, and corrosion properties of the composite. Various researchers confirmed that aluminum matrix composite (AMC) is an excellent multifunctional lightweight material with remarkable properties. However, to improve the wear resistance in high-performance tribological application, hardening and developing corrosion resistance was needed; thus, an optimized hybrid reinforcement of particulates (SiC-Fe₃O₄) into an aluminum matrix was explored. Based on obtained results, the density and hardness were 2.69 g/cm³, 91 HV for Al-30Fe₃O₄-20SiC, after the sintering process. Coefficient of friction (COF) was decreased after adding Fe₃O₄ and SiC hybrid composite in tribology behaviors, and the lowest COF was 0.412 for Al-30Fe₃O₄-20SiC. The corrosion protection efficiency increased from 88.07%, 90.91%, and 99.83% for Al-30Fe₃O₄, Al-15Fe₃O₄-30SiC, and Al-30Fe₃O₄-20SiC samples, respectively. Hence, the addition of this reinforcement (Al-Fe₃O₄-SiC) to the composite shows a positive outcome toward corrosion resistance (lower corrosion rate), in order to increase the durability and life span of material during operation. The accomplished results indicated that, by increasing the weight percentage of SiC-Fe₃O₄, it had improved the mechanical properties, tribology, and corrosion resistance in aluminum matrix. After comparing all samples, we then selected Al-30Fe₃O₄-20SiC as an optimized composite. Full article

(This article belongs to the Special Issue Recent Advances in Metal Forming Technology)

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