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Material Systems and Structures in Mechanical and Aerospace Engineering

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 37001

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Guest Editor
Chonbuk National University, South Korea
Interests: non-destructive testing; THz imaging; laser ultrasonics; ultrasonic testing; smart materials and structures; fiber optic sensors; piezoelectric materials; composite materials and structures; structural dynamics and control
Railroad Safety Research Team, Korea Railroad Research Institute (KRRI), Uiwang, Gyeonggi-do 16105, Republic of Korea
Interests: nondestructive testing and evaluation skills; field application using structural health monitoring techniques; development of fiber optic sensors and field applications; convergence with internet of things technology
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Special Issue Information

Dear Colleagues,

We are pleased to announce that submissions are open for the Special Issue of Materials devoted to papers presented at the International Conference on Advances in Aerospace and Mechanical Engineering (AAME 2019), held July 9–12, 2019 in Incheon, Korea.

AAME 2019 focused on the identification and assessment of the state-of-the-art technologies in aerospace and mechanical engineering and aims to promote exchange and collaboration across disciplines and borders to explore new territories and frontiers in this field. Topics included in this Special Issue are smart materials, structural systems, solutions and optimization, and tools and methodologies, as well as bio-inspired system design. Applications include aerospace, automotive, and morphing structures, energy harvesting, structural health monitoring, mechatronics, and robotics.

We invite you to submit high-quality research, technical, or review papers to this Special Issue, with an emphasis on innovative new and emerging technologies that encompass the broad meanings of material-based mechanical and aerospace engineering applications.

Some areas of interest for this Special Issue include, but are not limited to, new skills and application results on multi-functional materials and structures, advanced composite materials and structures, advanced manufacturing and design technology, advanced technologies in safety, PHM and reliability, advanced structural health management, advanced dynamics and control, multi-physics computational modelling and simulation, emerging applications of 3D printing in aerospace and mechanical engineering, metamaterial technologies, smart machines and sensors, etc.

If you need any further information about this Special Issue, please do not hesitate to contact us.

Prof. Lae-Hyong Kang
Prof. Dr. Donghoon Kang
Guest Editors

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Keywords

  • Multi-functional materials and structures
  • Advanced composite materials and structures
  • Advanced manufacturing and design technology
  • Advanced robotics and mechatronics
  • Advanced technologies in safety, PHM, and reliability
  • Advanced structural health management
  • Machine learning and IT applications in aerospace and mechanical engineering
  • Advanced dynamics and control
  • Multi-physics computational modeling and simulation
  • Emerging applications of 3D printing in aerospace and mechanical engineering
  • Emerging technologies in fluids engineering
  • Emerging technologies in thermal engineering
  • Emerging transportation technologies
  • Metamaterial technologies
  • Multidisciplinary micro/nano system engineering
  • Nature-inspired/biomimetic technologies
  • Smart machines and sensors
  • Other emerging technologies in aerospace and mechanical engineering

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Published Papers (12 papers)

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Research

15 pages, 7370 KiB  
Article
Behaviors of Micro-Arcs, Bubbles, and Coating Growth during Plasma Electrolytic Oxidation of β-Titanium Alloy
by Toshiaki Yasui, Katsuki Hayashi and Masahiro Fukumoto
Materials 2023, 16(1), 360; https://doi.org/10.3390/ma16010360 - 30 Dec 2022
Cited by 11 | Viewed by 2288
Abstract
The plasma electrolytic oxidation (PEO) of a titanium alloy, Ti-15V-3Cr-3Sn-3Al, was performed to develop mechanical applications by improving the tribological characteristics. The behaviors of micro-arcs, bubbles, and coating growth during the PEO process were investigated under three different operating conditions, constant voltage (CV) [...] Read more.
The plasma electrolytic oxidation (PEO) of a titanium alloy, Ti-15V-3Cr-3Sn-3Al, was performed to develop mechanical applications by improving the tribological characteristics. The behaviors of micro-arcs, bubbles, and coating growth during the PEO process were investigated under three different operating conditions, constant voltage (CV) operation, constant current operation (CC), and short treatment time (ST) operation, to control the surface structure and function by the PEO process. A low friction coefficient was achieved by CV operation at 500 V and by CC operation at 3.0 kA/m2. The maximum coating thickness of 6.88 μm was achieved by CV operation at 500 V and 60 s. From the observation of micro-arcs, bubbles, and discharge craters by ST operation, the minimum discharge diameter of the micro-arc was 8 μm, and the discharge craters had a discharge pore size of 0.3 μm in diameter in the center with a petal-shaped burr around the discharge pore. During the PEO process, no bubble bursts around the micro-arcs and no backfilling of the discharge pores by the ejected materials were observed. Thus, the discharge pores remain a porous structure in the PEO coating for Ti. The utilization efficiency of the total charge density by CV operation above 300 V was lower than that by the conventional anodization process. The utilization efficiency of total charge density by CC operation was higher than that by the conventional anodization process. Full article
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10 pages, 3436 KiB  
Article
Flexible Magnetic Polymer Composite Substrate with Ba1.5Sr1.5Z Hexaferrite Particles of VHF/Low UHF Patch Antennas for UAVs and Medical Implant Devices
by Sang-Eui Lee, Seong Pil Choi, Kyung-Sub Oh, Jaehwan Kim, Sang Min Lee and Kang Rae Cho
Materials 2020, 13(4), 1021; https://doi.org/10.3390/ma13041021 - 24 Feb 2020
Cited by 5 | Viewed by 2861
Abstract
Our goal is to fabricate flexible magnetic polymer composites as antenna substrates for very high frequency (VHF)/low ultra high frequency (UHF) antennas for unmanned aerial vehicles (UAVs) and medical devices. Magnetodielectric materials, which have permeability (μ) similar to permittivity (ε [...] Read more.
Our goal is to fabricate flexible magnetic polymer composites as antenna substrates for very high frequency (VHF)/low ultra high frequency (UHF) antennas for unmanned aerial vehicles (UAVs) and medical devices. Magnetodielectric materials, which have permeability (μ) similar to permittivity (ε), have attracted great attention, because they facilitate miniaturization of microwave devices while keeping or enhancing electromagnetic characteristics. Mechanically millled Ba1.5Sr1.5Co2Fe24O41 (Ba1.5Sr1.5Z) hexaferrite particles were used to increase permeability in the interesting frequency band. The microwave properties of Ba1.5Sr1.5Z composites were predicted and measured. Hansen’s zero-order analysis of antenna bandwidth and electromagnetic field simulation showed that the hexaferrite-based flexible composite could enhance a bandwidth and achieve the miniaturization of antennas as well. The magnetic antenna substrates can be a good solution to integrate antennas into the UAVs whose dimensions are comparable to or larger than communication wavelength. Full article
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16 pages, 7911 KiB  
Article
Fractal Characteristics of Chip Morphology and Tool Wear in High-Speed Turning of Iron-Based Super Alloy
by Xu Zhang, Guangming Zheng, Xiang Cheng, Rufeng Xu, Guoyong Zhao and Yebing Tian
Materials 2020, 13(4), 1020; https://doi.org/10.3390/ma13041020 - 24 Feb 2020
Cited by 8 | Viewed by 3397
Abstract
Considering that iron-based super alloy is a kind of difficult-to-cut material, it is easy to produce work hardening and serious tool wear during machining. Therefore, this work aims to explore the chip change characteristics and tool wear mechanism during the processing of iron-based [...] Read more.
Considering that iron-based super alloy is a kind of difficult-to-cut material, it is easy to produce work hardening and serious tool wear during machining. Therefore, this work aims to explore the chip change characteristics and tool wear mechanism during the processing of iron-based super alloy, calculate the fractal dimensions of chip morphology and tool wear morphology, and use fractals to analyze their change trend. Meanwhile, a new cutting tool with a super ZX coating is used for a high-speed dry turning experiment. The results indicate that the morphology of the chip is saw-tooth, and its color changes gradually, due to the oxidation reaction. The main wear mechanisms of the tool involve abrasive wear, adhesive wear, oxidation wear, coating spalling, microcracking and chipping. The fractal dimension of the tool wear surface and chip is increased with the improvement of cutting speed. This work investigates the fractal characteristics of chip morphology and tool wear morphology. The fractal dimension changes regularly with the change of tool wear, which plays an important role in predicting this tool wear. It is also provides some guidance for the efficient processing of an iron-based super alloy. Full article
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11 pages, 4624 KiB  
Article
Mechanical Properties and Thermal Conductivity of Ytterbium-Silicate-Mullite Composites
by Jie Xiao, Wenbo Chen, Liangliang Wei, Wenting He and Hongbo Guo
Materials 2020, 13(3), 671; https://doi.org/10.3390/ma13030671 - 3 Feb 2020
Cited by 8 | Viewed by 2790
Abstract
Various Ytterbium-Silicate-Mullite composites were successfully fabricated by adding Yb2SiO5 into mullite ceramics and then using pressureless sintering at 1550 °C. The influence of Yb2SiO5 addition on the microstructure, mechanical properties, and thermal conductivity of ytterbium-silicate-mullite composites was [...] Read more.
Various Ytterbium-Silicate-Mullite composites were successfully fabricated by adding Yb2SiO5 into mullite ceramics and then using pressureless sintering at 1550 °C. The influence of Yb2SiO5 addition on the microstructure, mechanical properties, and thermal conductivity of ytterbium-silicate-mullite composites was investigated. Results show that the composites mainly consisted of a mullite matrix and some in situ formed Yb2Si2O7 and Al2O3 phases. By the addition of Yb2SiO5, the Vickers hardness of composites reached ~9.0 at an additive concentration of 5 mol %. Fracture toughness increased to ~2.7 MPa·m1/2 at the additive concentration of 15 mol %, owing to the trans-granular fracture and crack deflection of the pinning effect of the Al2O3 phase in the composites. With the increase of the Al2O3 phase in the composite, the thermal conductivity for the 15YbAM reached around 4.0 W/(m·K) at 1200 °C. Although the thermal conductivity increased, it is still acceptable for such composites to be used as environmental barrier coatings. Full article
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19 pages, 2994 KiB  
Article
Structural and Micromechanical Properties of Ternary Granular Packings: Effect of Particle Size Ratio and Number Fraction of Particle Size Classes
by Joanna Wiącek, Mateusz Stasiak and Jalal Kafashan
Materials 2020, 13(2), 339; https://doi.org/10.3390/ma13020339 - 11 Jan 2020
Cited by 12 | Viewed by 2543
Abstract
The confined uniaxial tests of packings with discrete particle size distribution (PSD) were modeled with the discrete element method. Ternary packings of spheres with PSD uniform or nonuniform by number of particles were examined in three-dimensional (3D) system. The study addressed an effect [...] Read more.
The confined uniaxial tests of packings with discrete particle size distribution (PSD) were modeled with the discrete element method. Ternary packings of spheres with PSD uniform or nonuniform by number of particles were examined in three-dimensional (3D) system. The study addressed an effect of the particle size ratio and the particle size fraction on structural and micromechanical properties of mixtures. A study of packing structure included porosity and coordination numbers, while the investigation of micromechanical properties included distribution of normal contact forces and stress transmission through the packing. A micro-scale investigation of the effect of particle size ratio on structure and mechanics of the ternary packings revealed a strong relationship between the properties of sample and the value of parameter till its critical value was reached. A further increase in particle size ratio did not significantly affect properties of packings. Contrary to the porosity and coordination numbers, the partial stresses were highly affected by the fraction of particle size classes in ternary mixtures. The contribution of the partial stress into the global stress was determined by number fraction of particles in packings with small particle size ratio, while it was mainly determined by particle size ratio in packings with small particle size ratio. Full article
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10 pages, 6098 KiB  
Article
A Study of Films Incorporating Magnetite Nanoparticles as Susceptors for Induction Welding of Carbon Fiber Reinforced Thermoplastic
by Inseok Baek and Seoksoon Lee
Materials 2020, 13(2), 318; https://doi.org/10.3390/ma13020318 - 10 Jan 2020
Cited by 14 | Viewed by 3346
Abstract
Induction welding is a fast, clean, noncontact process that often uses a metal-mesh susceptor to facilitate localized controlled heating; however, the metal mesh presents various problems. In this study, the induction heating behavior of a 450 μ m thick thin-film susceptor, fabricated by [...] Read more.
Induction welding is a fast, clean, noncontact process that often uses a metal-mesh susceptor to facilitate localized controlled heating; however, the metal mesh presents various problems. In this study, the induction heating behavior of a 450 μ m thick thin-film susceptor, fabricated by mixing magnetite (Fe 3 O 4 ) nanoparticles (NPs) and PA6/carbon fiber (CF) (30%) thermoplastic resin, was examined with respect to the weight ratio of Fe 3 O 4 (50, 67, 75, and 80 wt%). The useful induction heating behavior of the 75 wt% Fe 3 O 4 susceptor suggested its suitability for additional heat treatment experiments, carried out at 3.4 kW at a frequency of 100 kHz. This susceptor attained the same maximum temperature during 10 cycles of repeated induction heating and cooling. It was then used to weld two thermoplastic composites, with 60 s of induction heating followed by 120 s of simultaneous cooling and pressing. The resulting welded joints had lap shear strength values of 36.8, 34.0, and 36.4 MPa under tensile test loads of 884, 817, and 874 N, respectively. Scanning electron microscopy images confirmed a uniform weld quality. Thus, the proposed manufacturing method, involving the incorporation of Fe 3 O 4 NPs into thermoplastic resin, should help expand the range of applications for thermoplastic composites. Full article
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22 pages, 10635 KiB  
Article
Bird-Strike Resistance of Composite Laminates with Different Materials
by Yadong Zhou, Youchao Sun and Tianlin Huang
Materials 2020, 13(1), 129; https://doi.org/10.3390/ma13010129 - 27 Dec 2019
Cited by 29 | Viewed by 4335
Abstract
To obtain some basic laws for bird-strike resistance of composite materials in aeronautical application, the high-velocity impact behaviors of composite laminates with different materials were studied by numerical methods. The smoothed particle hydrodynamics (SPH) and finite element method (FEM) coupling models were validated [...] Read more.
To obtain some basic laws for bird-strike resistance of composite materials in aeronautical application, the high-velocity impact behaviors of composite laminates with different materials were studied by numerical methods. The smoothed particle hydrodynamics (SPH) and finite element method (FEM) coupling models were validated from various perspectives, and the numerical results were comparatively investigated. Results show that the different composite materials have relatively little effect on projectile deformations during the bird impact. However, the impact-damage distributions can be significantly different for different composite materials. The strength parameters and fracture energy parameters play different roles in different damage modes. Lastly, modal frequency was tentatively used to explain the damage behavior of the composite laminates, for it can manifest the mass and stiffness characteristics of a dynamic structure. The dynamic properties and strength properties jointly determine the impact-damage resistance of composite laminates under bird strike. Future optimization study can be considered from these two aspects. Full article
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10 pages, 5579 KiB  
Article
Piezoelectric Characteristics of 0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr,Ti)O3 Ceramics with Different MnO2 Concentrations for Ultrasound Transducer Applications
by Myeongcheol Kang and Lae-Hyong Kang
Materials 2019, 12(24), 4115; https://doi.org/10.3390/ma12244115 - 9 Dec 2019
Cited by 7 | Viewed by 2871
Abstract
In this study, we investigate the piezoelectric characteristics of 0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr,Ti)O3 (PNN-PZT) with MnO2 additive (0, 0.25, 0.5, 1, 2, and 3 mol%). We focus on the fabrication of a piezoelectric ceramic for use as both [...] Read more.
In this study, we investigate the piezoelectric characteristics of 0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr,Ti)O3 (PNN-PZT) with MnO2 additive (0, 0.25, 0.5, 1, 2, and 3 mol%). We focus on the fabrication of a piezoelectric ceramic for use as both actuator and sensor for ultrasound transducers. The actuator and sensor properties of a piezoelectric ceramic depend on the piezoelectric strain coefficient d and piezoelectric voltage coefficient g, related as g = d/εT. To increase g, the dielectric constant εT must be decreased. PNN-PZT with MnO2 doping is synthesized using the conventional solid-state reaction method. The electrical properties are determined based on the resonant frequencies and vibration modes measured by using an impedance analyzer. The MnO2 addition initially improves the tetragonality of the PNN-PZT ceramic, which then saturates at a MnO2 content of 1 mol%. Therefore, the dielectric constant and piezoelectric coefficient d33 steadily decrease, while the mechanical properties (Qm, Young’s modulus), tanδ, electromechanical coupling coefficient k, and piezoelectric voltage coefficient g were improved at 0.5–1 mol% MnO2 content. Full article
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12 pages, 6272 KiB  
Article
Defect Visualization of a Steel Structure Using a Piezoelectric Line Sensor Based on Laser Ultrasonic Guided Wave
by Sang-Hyeon Kang, Dae-Hyun Han and Lae-Hyong Kang
Materials 2019, 12(23), 3992; https://doi.org/10.3390/ma12233992 - 2 Dec 2019
Cited by 6 | Viewed by 3040
Abstract
We studied the detection and visualization of defects in a test object using a laser ultrasonic guided wave. The scan area is irradiated by a laser generated from a Nd:YAG 532 nm Q-switched laser generator through a galvanometer scanner. The laser irradiation causes [...] Read more.
We studied the detection and visualization of defects in a test object using a laser ultrasonic guided wave. The scan area is irradiated by a laser generated from a Nd:YAG 532 nm Q-switched laser generator through a galvanometer scanner. The laser irradiation causes the surface temperature to suddenly rise and then become temporarily adiabatic. The locally heated region reaches thermal equilibrium with the surroundings. In other words, heat energy propagates inside the object in the form of elastic energy through adiabatic expansion. This thermoelastic wave is typically acquired by a piezoelectric sensor, which is sensitive in the ultrasonic domain. A single piezoelectric sensor has limited coverage in the scan area, while multi-channel piezoelectric sensors require many sensors, large-scale wiring, and many channeling devices for use and installation. In addition, the sensors may not acquire signals due to their installed locations, and the efficiency may be reduced because of the overlap between the sensing areas of multiple sensors. For these reasons, the concept of a piezoelectric line sensor is adopted in this study for the first time. To verify the feasibility of the line sensor, I- and L-shaped sensors were attached to a steel structure, and the ultrasound signal from laser excitation was obtained. If the steel structure has defects on the back, the ultrasonic propagation image will be distorted in the defect area. Thus, we can detect the defects easily from the visualization image. Three defects were simulated for the test. The results show that the piezoelectric line sensor can detect defects more precisely and accurately compared to a single piezoelectric sensor. Full article
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12 pages, 4762 KiB  
Article
Piezoresistive Multi-Walled Carbon Nanotube/Epoxy Strain Sensor with Pattern Design
by Mun-Young Hwang, Dae-Hyun Han and Lae-Hyong Kang
Materials 2019, 12(23), 3962; https://doi.org/10.3390/ma12233962 - 29 Nov 2019
Cited by 14 | Viewed by 3099
Abstract
Carbon nanotube/polymer-based composites have led to studies that enable the realization of low-cost, high-sensitivity piezoresistive strain sensors. This study investigated the characteristics of piezoresistive multi-walled carbon nanotube (MWCNT)/epoxy composite strain sensors subjected to tensile and compressive loads in one direction at relatively small [...] Read more.
Carbon nanotube/polymer-based composites have led to studies that enable the realization of low-cost, high-sensitivity piezoresistive strain sensors. This study investigated the characteristics of piezoresistive multi-walled carbon nanotube (MWCNT)/epoxy composite strain sensors subjected to tensile and compressive loads in one direction at relatively small amounts of strain. A patterned sensor was designed to overcome the disadvantage of the load direction sensitivity differences in the existing sensors. The dispersion state of the MWCNTs in the epoxy polymer matrix with the proposed dispersion process was verified by scanning electron microscopy. An MWCNT/epoxy patterned strain sensor and a patch-type strain sensor were directly attached to an acrylic cantilever beam on the opposite side of a commercial metallic strain gauge. The proposed patterned sensor had gauge factors of 2.52 in the tension direction and 2.47 in the compression direction. The measured gauge factor difference for the patterned sensor was less than that for the conventional patch-type sensor. Moreover, the free-vibration frequency response characteristics were compared with those of metal strain gauges to verify the proposed patch-type sensor. The designed drive circuit compensated for the disadvantages due to the high drive voltage, and it was confirmed that the proposed sensor had higher sensitivity than the metallic strain gauge. In addition, the hysteresis of the temperature characteristics of the proposed sensor is presented to show its temperature range. It was verified that the patterned sensor developed through various studies could be applied as a strain sensor for structural health monitoring. Full article
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21 pages, 8295 KiB  
Article
Analysis of Important Fabrication Factors That Determine the Sensitivity of MWCNT/Epoxy Composite Strain Sensors
by Mun-Young Hwang and Lae-Hyong Kang
Materials 2019, 12(23), 3875; https://doi.org/10.3390/ma12233875 - 24 Nov 2019
Cited by 3 | Viewed by 2569
Abstract
Composite sensors based on carbon nanotubes have been leading to significant research providing interesting aspects for realizing cost-effective and sensitive piezoresistive strain sensors. Here, we report a wide range of piezoresistive performance investigations by modifying fabrication factors such as multi-wall carbon nanotubes (MWCNT) [...] Read more.
Composite sensors based on carbon nanotubes have been leading to significant research providing interesting aspects for realizing cost-effective and sensitive piezoresistive strain sensors. Here, we report a wide range of piezoresistive performance investigations by modifying fabrication factors such as multi-wall carbon nanotubes (MWCNT) concentration and sensor dimensions for MWCNT/epoxy composites. The resistance change measurement analyzed the influence of the fabrication factors on the changes in the gauge factor. The dispersion quality of MWCNTs in the epoxy polymer matrix was investigated by scanning electron microscopy (SEM) images and conductivity measurement results. A configuration circuit was designed to use the composite sensor effectively. It has been shown that, in comparison with commercially available strain gauges, composites with CNT fillers have the potential to attain structural health monitoring capabilities by utilizing the variation of electrical conductivity and its relation to strain or damage within the composite. Based on the characteristics of the MWCNT, we predicted the range of conductivity that can be seen in the fabricated composite. The sensor may require a large surface area and a thin thickness as fabrication factors at minimum filler concentration capable of exhibiting a tunneling effect, in order to fabricate a sensor with high sensitivity. The proposed composite sensors will be suitable in various potential strain sensor applications, including structural health monitoring. Full article
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17 pages, 6169 KiB  
Article
Acquisition of Dynamic Material Properties in the Electrohydraulic Forming Process Using Artificial Neural Network
by Min-A Woo, Young-Hoon Moon, Woo-Jin Song, Beom-Soo Kang and Jeong Kim
Materials 2019, 12(21), 3544; https://doi.org/10.3390/ma12213544 - 29 Oct 2019
Cited by 6 | Viewed by 2840
Abstract
Electrohydraulic forming is a high-velocity forming process that deforms sheet metals with velocities above 100 m/s and strain rates more than 100 s−1. This experiment was conducted in a closed space because of safety concerns related to the high-velocity conditions; therefore, [...] Read more.
Electrohydraulic forming is a high-velocity forming process that deforms sheet metals with velocities above 100 m/s and strain rates more than 100 s−1. This experiment was conducted in a closed space because of safety concerns related to the high-velocity conditions; therefore, we were not able to examine the deformation process of the sheet metal. To observe the electrohydraulic forming process in detail, we performed virtual numerical simulations using accurate material properties. Therefore, in this paper, we obtained the material property of a sheet metal from a numerical estimation by using a surrogate model based on the reduced order model and the artificial neural network. The Cowper–Symonds constitutive equation was selected for the Al 6061-T6 sheet metal, and two strain rate parameters were adopted as the unknown parameters. From the two sampling techniques, the training and test samples were extracted from the specific ranges of two unknown parameters, and a numerical simulation was performed for these samples by using the LS-DYNA program. The z-axis displacements of the deformed sheet metal were obtained from the results of the numerical simulation, and two basis vectors were extracted by using principal component analysis. In addition, to predict the weighting coefficients of the two basis vectors at the defined range of parameters, we used the artificial neural network technique as a surrogate model. By comparing the surrogate model and the experimental results and calculating the root mean square error value, we estimated the optimal parameter for Al 6061-T6. Finally, the reliability of the obtained material parameters was proved by comparing the experimental results, the surrogate model, and LS-DYNA. Full article
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