Research

20 pages, 8486 KiB

Open AccessArticle

Assessing Cast Aluminum Alloys with Computed Tomography Defect Metrics: A Gurson Porous Plasticity Approach

by Armağan Gul, Ozgur Aslan, Eyüp Sabri Kayali and Emin Bayraktar

Metals 2023, 13(4), 752; https://doi.org/10.3390/met13040752 - 12 Apr 2023

Cited by 2 | Viewed by 1122

Aluminum alloys have inherent tendencies to produce casting defects caused by alloying or metal melt flow inside the mold. The traditional detection method for these defects includes reduced pressure tests, which assess metal quality in a destructive manner. This leaves a gap between [...] Read more.

Aluminum alloys have inherent tendencies to produce casting defects caused by alloying or metal melt flow inside the mold. The traditional detection method for these defects includes reduced pressure tests, which assess metal quality in a destructive manner. This leaves a gap between metal quality assessments and tensile test correlations. Computed tomography (CT) scans offer crucial assistance in evaluating the internal quality of castings without damaging the structure. This provides a valuable opportunity to couple mechanical tests with numerical methods such as finite element analysis to predict the mechanical performance of the alloy. The present study aims to evaluate the internal quality of cast aluminum alloys using CT scans and to correlate the defect metrics obtained from CT scans with mechanical test results. The Gurson-type material model and finite element methodology have been used to validate the correlation studies. Therefore, we propose a more holistic approach to predicting the behavior of metals by coupling damage models with CT scans and mechanical tests. The study investigates several CT metrics such as the defect volume, total defect surface, biggest defect surface, and projected area of defects. The conclusion reveals that CT scans provide crucial assistance in evaluating the internal quality of castings, and CT defect metrics can be used to build correlations between mechanical tests and CT evaluations. The study also suggests that the concept of adjusted representative material yield parameter (ARMY) or computed representative material yield parameter (CRMY) can be used to correlate CT metrics with mechanical strength in cast materials and parts for a given aluminum alloy. Overall, the study proposes a more comprehensive methodology to assess the quality of cast aluminum alloys and couple the quality to mechanical performance. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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13 pages, 4721 KiB

Open AccessArticle

Physically-Based Methodology for the Characterization of Wrinkling Limit Curve Validated by Yoshida Tests

by João A.O. Santos, João P.G. Magrinho and Maria Beatriz Silva

Metals 2023, 13(4), 746; https://doi.org/10.3390/met13040746 - 12 Apr 2023

Viewed by 980

Abstract

This paper presents a new experimental methodology for determining the formability limits by wrinkling in sheet metal forming using Yoshida buckling tests (YBTs). The YBT has been the most used formability test by the scientific community to determine the occurrence of wrinkling, on [...] Read more.

This paper presents a new experimental methodology for determining the formability limits by wrinkling in sheet metal forming using Yoshida buckling tests (YBTs). The YBT has been the most used formability test by the scientific community to determine the occurrence of wrinkling, on the one hand, due to its simple clamping configuration directly related to the kinematics of tensile tests. On the other hand, the formability test replicates the occurrence of wrinkling in deformation regions under tension, similar to the side wall wrinkling of a deep drawn part. The new physically-based methodology is built upon the direct analysis of the in-plane minor strain and its strain rate for a point located at the center of the YBT specimen. Application of the methodology in AA1050–O aluminium alloy sheets enabled the experimental determination of the onset of wrinkling. Results also showed that in contrast to conventional techniques, where the wrinkling prediction is based in a specified percentage of the initial thickness of the blank (5–10%), considering a physical wrinkle-triggering factor enables one to identify the precise moment at which wrinkling occurs. The proposed physically-based methodology provides a new level of understanding of the YBT behavior and the onset of wrinkling determination for sheet metal forming with a higher degree of accuracy. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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15 pages, 2364 KiB

Open AccessArticle

An Upper Bound Solution for Axisymmetric Extrusion and Drawing Considering a Generalized Yield Criterion

by Sergei Alexandrov, Stanislav Strashnov and Yong Li

Metals 2023, 13(3), 602; https://doi.org/10.3390/met13030602 - 16 Mar 2023

Viewed by 932

Abstract

The yield criterion of many metallic materials differs from the von Mises yield criterion. However, the available upper bound solutions are almost all restricted to this criterion. The objective of the present paper was to derive an upper bound solution based on a [...] Read more.

The yield criterion of many metallic materials differs from the von Mises yield criterion. However, the available upper bound solutions are almost all restricted to this criterion. The objective of the present paper was to derive an upper bound solution based on a generalized yield criterion for evaluating the extrusion and drawing force, assuming a conical die. The solution method differs from the conventional method used in conjunction with the von Mises yield criterion. The development of this method is necessary, since the work function is not readily expressed as an explicit function of strain rate invariants if the generalized yield criterion is adopted. The solution is illustrated using numerical examples, which show the effect of the yield criterion on the limit load. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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17 pages, 8861 KiB

Open AccessArticle

Process Design for Manufacturing Fiber-Reinforced Plastic Helical Gears Using a Rapid Heating and Cooling System

by Cheol Hwan Lee, Yong Ki Kang, Dong Kyu Kim, Sang Hyeon Kim and Young Hoon Moon

Metals 2023, 13(3), 483; https://doi.org/10.3390/met13030483 - 26 Feb 2023

Viewed by 1308

Abstract

In this study, a lightweight fiber-reinforced plastic (FRP) helical gear was fabricated to investigate the potential application of FRP in automobile parts that require high loads and reduced noise. High-performance aramid FRP processed using the wet-laid method was used in the tooth region, [...] Read more.

In this study, a lightweight fiber-reinforced plastic (FRP) helical gear was fabricated to investigate the potential application of FRP in automobile parts that require high loads and reduced noise. High-performance aramid FRP processed using the wet-laid method was used in the tooth region, and SCR420 steel was used in the inner hub region. A hot-forming system that combines rapid induction heating and water channel cooling methods was developed to reduce the cycle time. The cooling water flow conditions were analyzed to precisely control the mold temperature. Additionally, a rotating extraction system was developed to mitigate the extraction difficulty owing to the helix angle to the extraction direction. Using the innovative hot-forming system developed in this study, a helical gear without any process-induced defects was fabricated with a significantly reduced cycle time. The performance of the gear was successfully estimated using gear durability, torsional strength, and motion noise tests. The use of FRP materials offers significant potential to realize lightweight components; however, certain challenges related to their properties that may limit their application must be addressed on a case-by-case basis. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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18 pages, 9127 KiB

Open AccessArticle

Influence of the Grain-Flow Orientation after Hot Forging Process Evaluated through Rotational Flexing Fatigue Test

by Jaques Araripe Suris, Charles Chemale Yurgel and Ricardo Alves de Sousa

Metals 2023, 13(2), 187; https://doi.org/10.3390/met13020187 - 17 Jan 2023

Cited by 2 | Viewed by 1693

Abstract

The hot forging process brings significant advantages in terms of improved mechanical properties of the part compared with other processes, such as casting or machining. The metal flow in the forging process leads to texture modifications and can be macroscopically visualized by the [...] Read more.

The hot forging process brings significant advantages in terms of improved mechanical properties of the part compared with other processes, such as casting or machining. The metal flow in the forging process leads to texture modifications and can be macroscopically visualized by the so-called grain-flow orientation (GFO). This study showed the effect of GFO on fatigue life by using a rotational flexing fatigue test. The tests that were performed using SAE 1045H steel material, at rolling and transverse directions, showed the influence of GFO on the specimens’ mechanical properties compared with the reference samples taken from the machined rolled bar. The experimental results showed that the forged samples with the GFO in the main deformation direction presented a higher fatigue life than the other tested configurations. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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15 pages, 1880 KiB

Open AccessArticle

Review of the Upper Bound Method for Application to Metal Forming Processes

by Sergei Alexandrov and Marina Rynkovskaya

Metals 2022, 12(11), 1962; https://doi.org/10.3390/met12111962 - 16 Nov 2022

Cited by 2 | Viewed by 1362

Abstract

In this paper, we review the upper bound method in plasticity with special reference to metal forming processes. We focus on the method itself, solution methods, and restrictions of the upper bound method. Particular upper bound solutions are not considered. The upper bound [...] Read more.

In this paper, we review the upper bound method in plasticity with special reference to metal forming processes. We focus on the method itself, solution methods, and restrictions of the upper bound method. Particular upper bound solutions are not considered. The upper bound theorem is formulated using the work function, which is different from conventional proofs. This approach allows for a unified formulation for several types of rigid plastic materials. The solution methods include upper bound elemental techniques, streamline-based methods, and singular solutions. The major restrictions are related to stationary processes and friction laws. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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17 pages, 3793 KiB

Open AccessArticle

Research on Cracked Conditions in Nickel Chrome Alloy Ni50Cr33W4.5Mo2.8TiAlNb, Obtained by Direct Laser Deposition

by Alexander Khaimovich, Igor Shishkovsky, Yaroslav Erisov, Anton Agapovichev, Vitaliy Smelov and Vasilii Razzhivin

Metals 2022, 12(11), 1902; https://doi.org/10.3390/met12111902 - 07 Nov 2022

Cited by 3 | Viewed by 1260

Abstract

Nowadays, additive manufacturing (AM) is a powerful way to make complex-shaped components for airspace engineering from nickel-based superalloys. So, while nickel-based superalloys could easily be we L-DED in sheet-metal thicknesses, they suffered from strain-age cracking and solidification during AM or in the post-weld [...] Read more.

Nowadays, additive manufacturing (AM) is a powerful way to make complex-shaped components for airspace engineering from nickel-based superalloys. So, while nickel-based superalloys could easily be we L-DED in sheet-metal thicknesses, they suffered from strain-age cracking and solidification during AM or in the post-weld aging treatment. This is attributed to the fact that besides the limitation of γ′- phase forming elements (Al and Ti), as they form by AM very rapidly and reduce ductility, the majority of the superalloys contain carbide-forming elements such as Cr, Mo, and W. The precipitation of carbides, which is very effective in strengthening, develops cracks in the heat-affected zone (HAZ) during AM. The difference in isochoric heat capacities and the thermal expansion coefficient (TEC) at the phase boundary leads to the appearance of dangerous local destruction energy. If the area of the interfacial interface is sufficiently extended, then the accumulation of this energy reaches a level sufficient for a crack formation. We have proposed a crack initiation criterion (CIC) for assessing the dangerous level of fracture energy. The CIC was derived from an estimate of the local energy balance from the heat transfer equation for the two-phase area. Practical approbation of the criterion was carried out after L-DED of samples from Ni50Cr33W4.5Mo2.8TiAlNb (EP648) alloy powder with an increased carbon content based on the study of the chemical composition near the crack formed during solidification. Using the proposed criterion provides an opportunity to give the rank to carbide-forming elements according to the degree of their influence on the fracture energy. Thus, the release of aluminum carbide turned out to be 5.48 times more dangerous than the release of titanium carbide and more than 5 times more dangerous than the release of tungsten carbide and molybdenum. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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13 pages, 1647 KiB

Open AccessArticle

Prediction of a Material Property Gradient near the Friction Surface in Axisymmetric Extrusion and Drawing

by Elena Lyamina

Metals 2022, 12(8), 1310; https://doi.org/10.3390/met12081310 - 04 Aug 2022

Cited by 2 | Viewed by 1086

Abstract

The present paper provides a theoretical prediction of the evolution of material properties near the friction surface in axisymmetric extrusion and drawing. The method employed is based on the strain rate intensity factor and uses empirical equations that connect the integrated strain rate [...] Read more.

The present paper provides a theoretical prediction of the evolution of material properties near the friction surface in axisymmetric extrusion and drawing. The method employed is based on the strain rate intensity factor and uses empirical equations that connect the integrated strain rate intensity factor with the thickness of a narrow layer of intensive plastic deformation and the hardness of the surface layer. The material obeys Hosford’s yield criterion. Therefore, the empirical equations above are reformulated in terms of the work rate intensity factor. Since no numerical method is available, the strain rate and work rate intensity factors are determined from an approximate solution. The solution reveals the effect of process and material parameters on the thickness of a layer of intensive plastic deformation and the hardness of the surface layer. Since the solution is semi-analytical, it is straightforward to use its results to design the metal forming processes. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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10 pages, 2705 KiB

Open AccessArticle

Investigations on Effects of Forming Parameters on Product Dimensions in Cold Drawing of AISI-316 Stainless Steel Rods

by Yeong-Maw Hwang, Hiu Shan Rachel Tsui and Man-Ru Lin

Metals 2022, 12(4), 690; https://doi.org/10.3390/met12040690 - 18 Apr 2022

Cited by 2 | Viewed by 1657

Abstract

Cold drawing is a commonly used metal forming technique carried out by pulling a billet through a die cavity to obtain desired dimensions. Ideally, the cross-sectional area of the drawn product should be equal to that of the die at its exit; however, [...] Read more.

Cold drawing is a commonly used metal forming technique carried out by pulling a billet through a die cavity to obtain desired dimensions. Ideally, the cross-sectional area of the drawn product should be equal to that of the die at its exit; however, the former one is always larger after drawing, in practice. In this study, cold drawing of an AISI-316 stainless steel rod is investigated through finite element analysis. The difference between the product radius and the die radius is denoted by ∆R. A series of simulations using combinations of various forming parameters, including semi-die angle, bearing ratio, reduction ratio, drawing speed and friction coefficient, are conducted to find out the dominant factors of ∆R. It is found that ∆R is mainly affected by semi-die angle, reduction ratio and friction. An empirical formula for ∆R, including various parameters, is established according to the simulation results and verified by drawing experiments as well. Using this empirical formula, the product dimensions can be predicted in advance and proper forming parameters can be chosen to decrease ∆R and improve the product quality. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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14 pages, 6041 KiB

Open AccessArticle

Zoning Lubricant Die Application for Improving Formability of Box-Shaped Deep Drawn Parts

by Wiriyakorn Phanitwong, Juksawat Sriborwornmongkol and Sutasn Thipprakmas

Metals 2021, 11(7), 1015; https://doi.org/10.3390/met11071015 - 24 Jun 2021

Cited by 4 | Viewed by 2052

Abstract

The ‘formability’ of sheet metal is a major keyword referring to process design in the sheet metal forming industry. Higher formability could reflect lower production costs and time. Many studies have been carried out to improve formability in various ways, by using the [...] Read more.

The ‘formability’ of sheet metal is a major keyword referring to process design in the sheet metal forming industry. Higher formability could reflect lower production costs and time. Many studies have been carried out to improve formability in various ways, by using the finite element method and experimental approaches. In the present research, a new zoning lubricant technique is proposed. The stainless steel SUS304 square deep drawn box is used as an investigative model. Based on the material flow analysis, we found that zoning lubricant die application could reduce the difference in material flow velocity between wall and corner zones. This material flow characteristic resulted in decreased nonconcurrent plastic deformation during the deep drawing process, as well as decreased stretching in the cup wall and the delaying of the fracture. In the present research, the design of the zoning lubricant die was strictly concerned with achieving functionality related to the friction coefficient, area of zoning, and blank-holder pressure. A smaller friction coefficient positioned in the corner zone and larger friction coefficient positioned in the wall zone are recommended. It was revealed that, by appropriate zoning lubricant die application, formability could be increased in terms of box height by approximately 7 mm or 10%. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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16 pages, 6798 KiB

Open AccessArticle

Hot Deformation Constitutive Equation and Plastic Instability of 30Cr4MoNiV Ultra-High-Strength Steel

by Gang Chen, Yuanchao Yao, Yuzhen Jia, Bin Su, Guoyue Liu and Bin Zeng

Metals 2021, 11(5), 769; https://doi.org/10.3390/met11050769 - 07 May 2021

Cited by 8 | Viewed by 2179

Abstract

In this work, the hot deformation behavior of 30Cr4MoNiV ultra-high-strength steel is investigated by isothermal compression tests using the Gleeble-3500 thermal simulation machine (Dynamic Systems Inc., New York, NY, USA) at a temperature range of 1173–1373 K under the strain rate of 0.01–10 [...] Read more.

In this work, the hot deformation behavior of 30Cr4MoNiV ultra-high-strength steel is investigated by isothermal compression tests using the Gleeble-3500 thermal simulation machine (Dynamic Systems Inc., New York, NY, USA) at a temperature range of 1173–1373 K under the strain rate of 0.01–10 s⁻¹. A constitutive equation with strain-dependent constants and processing maps suitable for 30Cr4MoNiV ultra-high-strength steel are established. The results show that the combination of the hyperbolic sine function and the Zener-Hollomon parameter can accurately represent the influences of deformation temperature, strain rate, and strain on the flow stress of the 30Cr4MoNiV ultra-high-strength steel. The applicability of plastic instability criteria such as m,

\dot{m}

, S,

\dot{S}

and the instability parameter ξ are analyzed, the stability and instability regions are clarified accurately, and the optimized processing regions are given in the stability regions. The optimized regions are verified by the uniform equiaxed grains, and the plastic instability is validated by dynamic strain aging and the microstructure of the voids. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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16 pages, 6359 KiB

Open AccessArticle

Effects of Variable Punch Speed and Blank Holder Force in Warm Superplastic Deep Drawing Process

by Ken-ichi Manabe, Kentaro Soeda and Akinori Shibata

Metals 2021, 11(3), 493; https://doi.org/10.3390/met11030493 - 17 Mar 2021

Cited by 9 | Viewed by 2850

Abstract

A cylindrical deep drawing test was conducted for the purpose of improving the drawability, product accuracy, and quality in warm deep drawing using a superplastic material with large strain rate dependence. Then, the effects of blank holding force (BHF) and punch speed (SPD) [...] Read more.

A cylindrical deep drawing test was conducted for the purpose of improving the drawability, product accuracy, and quality in warm deep drawing using a superplastic material with large strain rate dependence. Then, the effects of blank holding force (BHF) and punch speed (SPD) on the flange wrinkle behavior and wall thickness distribution were investigated by experiments and theoretical analysis. A Zn-22Al-0.5Cu-0.01Mg alloy superplastic material SPZ2 with a sheet thickness of 1 mm was employed as the experimental material, and a cylindrical deep drawing experiment with the drawing ratio (DR) of 3.1 and 5 was performed at 250 °C. A good agreement was qualitatively obtained between the elementary theory on the flange wrinkle limit, the fracture limit, and the experimental results. In addition, the authors examined each variable BHF and SPD method obtained from the theory and experimentally demonstrated that the variable BHF method has a great effect on uniform wall thickness distribution and that variable SPD has a great effect on shortening the processing time for superplastic materials. Furthermore, the authors demonstrated the effectiveness of the variable BHF/SPD deep drawing method that varies both BHF and SPD simultaneously. Full article

(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)

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