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Nanomechanics and Plasticity
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Nanomechanics and Plasticity

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanofabrication and Nanomanufacturing".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 31867

Special Issue Editor

Dr. Haifei Zhan

E-Mail Website
Guest Editor
1. College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
2. School of Mechanical Medical and Process Engineering, Queensland University of Technology, Brisbane, QLD 4000, Australia
Interests: nanomechanics; nanoscale thermal transport
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nanomaterials and nanostructures have seen appealing applications in broad fields, such as defense, aerospace, civil engineering, mechanical engineering, electronics, and biomedicine. To facilitate the engineering implementation, a comprehensive understanding of their mechanical properties and deformation mechanism is usually a prerequisite. Different nanomaterials and nanostructures are currently being investigated through experiments or atomistic simulations, such as low-dimensional nanostructures, nanocomposites, nanofibers, biomaterials, and other nanostructures. Not only under the ambient conditions, the mechanical properties or behaviors of nanomaterials at extreme conditions such as high temperature or pressure are also attracting extensive efforts. There is also currently great interest in the study of the physical or chemical properties of advanced nanomaterials under mechanical strain, which is emerging as a fascinating and challenging avenue to enable nanomaterials with unique properties.

This Special Issue of Nanomaterials will attempt to cover the most recent advances in “Nanomechanics and Plasticity”, concerning not only the mechanical properties, behaviors, and deformation mechanisms of nanomaterials or nanostructures, but also their novel physical or chemical phenomena or responses as triggered by mechanical strain.

Dr. Haifei Zhan
Guest Editor

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Keywords

  • nanomechanics
  • plasticity
  • mechanical properties
  • mechanical behavior
  • nanostructures
  • nanomaterials
  • nanocomposites
  • nanofibers

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Editorial

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3 pages, 194 KiB  
Editorial
Nanomechanics and Plasticity
by Haifei Zhan
Nanomaterials 2022, 12(21), 3807; https://doi.org/10.3390/nano12213807 - 28 Oct 2022
Viewed by 838
Abstract
Nanomaterials and nanostructures are continuously driving technology revolutions in broad engineering fields, such as defense [...] Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)

Research

Jump to: Editorial

7 pages, 19098 KiB  
Article
Structure and Nanomechanics of PPTA-CNT Composite Fiber: A Molecular Dynamics Study
by Tong Li, Zebei Mao, Juan Du and Zhuoyu Song
Nanomaterials 2022, 12(18), 3136; https://doi.org/10.3390/nano12183136 - 09 Sep 2022
Cited by 5 | Viewed by 1461
Abstract
Poly phenylene terephthalamide (PPTA) fiber has both high mechanical properties and low thermal conductivities, making it ideal for the design of thermal protection material in hypersonic vehicles. In this paper, the impact of CNT additions on the nanostructure and mechanical performances of PPTA [...] Read more.
Poly phenylene terephthalamide (PPTA) fiber has both high mechanical properties and low thermal conductivities, making it ideal for the design of thermal protection material in hypersonic vehicles. In this paper, the impact of CNT additions on the nanostructure and mechanical performances of PPTA fibers is investigated by coarse-grained molecular dynamics (CGMD) simulation. It can be found that CNT addition performs as the skeleton of PPTA polymer and induces a higher degree of alignment of polymers under shear deformation during the fabrication process. Both strength and Young’s modulus of the PPTA fiber can be improved by the addition of CNTs. The interaction between CNTs and PPTA polymer in PPTA fiber is important to further improve the efficiency of force transfer and mechanical performance of PPTA-CNT composite fibers. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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10 pages, 4277 KiB  
Article
Controllable Valley Polarization and Strain Modulation in 2D 2H–VS2/CuInP2Se6 Heterostructures
by Fan Yang, Jing Shang, Liangzhi Kou, Chun Li and Zichen Deng
Nanomaterials 2022, 12(14), 2461; https://doi.org/10.3390/nano12142461 - 18 Jul 2022
Cited by 3 | Viewed by 1698
Abstract
Two–dimensional (2D) transition metal dichalcogenides endow individually addressable valleys in momentum space at the K and K’ points in the first Brillouin zone due to the breaking of inversion symmetry and the effect of spin–orbit coupling. However, the application of 2H–VS2 monolayer [...] Read more.
Two–dimensional (2D) transition metal dichalcogenides endow individually addressable valleys in momentum space at the K and K’ points in the first Brillouin zone due to the breaking of inversion symmetry and the effect of spin–orbit coupling. However, the application of 2H–VS2 monolayer in valleytronics is limited due to the valence band maximum (VBM) located at the Γ point. Here, by involving the 2D ferroelectric (FE) CuInP2Se6 (CIPSe), the ferrovalley polarization, electronic structure, and magnetic properties of 2D 2H–VS2/CIPSe heterostructures with different stacking patterns and FE polarizations have been investigated by using first–principles calculations. It is found that, for the energetically favorable AB–stacking pattern, the valley polarization is preserved when the FE polarization of CIPSe is upwards (CIPSe↑) or downwards (CIPSe↓) with the splitting energies slightly larger or smaller compared with that of the pure 2H–VS2. It is intriguing that, for the FE CIPSe↑ case, the VBM is expected to pass through the Fermi energy level, which can be eventually achieved by applying biaxial strain and thus the valleytronic nature is turned off; however, for the CIPSe↓ situation, the heterostructure basically remains semiconducting even under biaxial strains. Therefore, with the influence of proper strains, the FE polar reversal of CIPSe can be used as a switchable on/off to regulate the valley polarization in VS2. These results not only demonstrate that 2H–VS2/CIPSe heterostructures are promising potential candidates in valleytronics, but also shed some light on developing practical applications of valleytronic technology. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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11 pages, 12261 KiB  
Article
Atomistic Investigation of the Titanium Carbide MXenes under Impact Loading
by Kang Xia, Haifei Zhan, Xinjie Zhang and Zhiyong Li
Nanomaterials 2022, 12(14), 2456; https://doi.org/10.3390/nano12142456 - 18 Jul 2022
Cited by 3 | Viewed by 1532
Abstract
2D Titanium carbide MXenes with a structural formula recognized as Tin+1Cn have attracted attention from both the academic and industry fields due to their intriguing mechanical properties and appealing potential in a variety of areas such as nano-electronic circuits/devices, bio [...] Read more.
2D Titanium carbide MXenes with a structural formula recognized as Tin+1Cn have attracted attention from both the academic and industry fields due to their intriguing mechanical properties and appealing potential in a variety of areas such as nano-electronic circuits/devices, bio sensors, energy storage and reinforcing material for composites. Based on mutli-body comb3 (third-generation Charge-Optimized Many-Body) potential, this work investigated the impact resistance of monolayer Tin+1Cn nanosheets (namely, Ti2C Ti3C2 and Ti4C3) under hypervelocity up to 7 km/s. The deformation behavior and the impact resist mechanisms of Tin+1Cn nanosheets were assessed. Penetration energy is found to positively correlate with the number of titanium atom layer (n). However, in tracking atomic Von Mises stress distribution, Ti2C exhibits the most significant elastic wave propagation velocity among the examined nanosheets, suggesting the highest energy delocalization rate and stronger energy dissipation via deformation prior to bond break. Consistently, Ti2C presents superior specific penetration energy due its Young’s-modulus-to-density ratio, followed by Ti3C2 and Ti4C3, suggesting an inverse correlation between the titanium atom layer number and specific penetration energy. This study provides a fundamental understanding of the deformation and penetration mechanisms of titanium carbide MXene nanosheets under impact, which could be beneficial to facilitating their emerging impact protection applications. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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14 pages, 4349 KiB  
Article
Effect of Hydrothermal Method Temperature on the Spherical Flowerlike Nanostructures NiCo(OH)4-NiO
by Kai Wang, Meini Yuan, Xiaochen Cao, Congming Ding, Jian Ma and Zeyuan Wei
Nanomaterials 2022, 12(13), 2276; https://doi.org/10.3390/nano12132276 - 01 Jul 2022
Cited by 3 | Viewed by 1389
Abstract
NiCo(OH)4-NiO composite electrode materials were prepared using hydrothermal deposition and electrophoretic deposition. NiCo(OH)4 is spherical and flowerlike, composed of nanosheets, and NiO is deposited on the surface of NiCo(OH)4 in the form of nanorods. NiCo(OH)4 has a large [...] Read more.
NiCo(OH)4-NiO composite electrode materials were prepared using hydrothermal deposition and electrophoretic deposition. NiCo(OH)4 is spherical and flowerlike, composed of nanosheets, and NiO is deposited on the surface of NiCo(OH)4 in the form of nanorods. NiCo(OH)4 has a large specific surface area and can provide more active sites. Synergistic action with NiO deposits on the surface can provide a higher specific capacitance. In order to study the influence of hydrothermal reaction temperature on the properties of NiCo(OH)4, the prepared materials of NiCo(OH)4-NiO, the hydrothermal reaction temperatures of 70 °C, 90 °C, 100 °C, and 110 °C were used for comparison. The results showed that the NiCo(OH)4-NiO-90 specific capacitance of the prepared electrode material at its maximum when the hydrothermal reaction temperature is 90 °C. The specific capacitance of the NiCo(OH)4-NiO-90 reaches 2129 F g−1 at the current density of 1 A g−1 and remains 84% after 1000 charge–discharge cycles. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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9 pages, 3124 KiB  
Article
Deformation of Copper Nanowire under Coupled Tension–Torsion Loading
by Hongquan Lu, Bin Dong, Junqian Zhang, Chaofeng Lü and Haifei Zhan
Nanomaterials 2022, 12(13), 2203; https://doi.org/10.3390/nano12132203 - 27 Jun 2022
Cited by 1 | Viewed by 1370
Abstract
Metallic nanowires (NWs) are essential building blocks for flexible electronics, and experience different deformation modes due to external mechanical loading. Using atomistic simulations, this work investigated the deformation behavior of copper nanowire under coupled tension–torsion loading. A transition in both yielding pattern and [...] Read more.
Metallic nanowires (NWs) are essential building blocks for flexible electronics, and experience different deformation modes due to external mechanical loading. Using atomistic simulations, this work investigated the deformation behavior of copper nanowire under coupled tension–torsion loading. A transition in both yielding pattern and dislocation pattern were observed with varying torsion/tension strain ratios. Specifically, increasing the torsion/tension strain ratio (with larger torsional strain) triggered the nucleation of different partial dislocations in the slip system. At low torsion/tension strain ratios, plastic deformation of the nanowire was dominated by stacking faults with trailing partial dislocations pinned at the surface, shifting to two partial dislocations with stacking faults as the strain ratio increases. More interestingly, the NW under tension-dominated loading exhibited a stacking fault structure after yielding, whereas torsion-dominated loading resulted in a three-dimensional dislocation network within the structure. This work thus suggests that the deformation behavior of the NW varies depending on the coupled mechanical loading, which could be beneficial for various engineering applications. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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12 pages, 7014 KiB  
Article
Mechanical Behaviors in Janus Transition-Metal Dichalcogenides: A Molecular Dynamics Simulation
by Fan Yang, Jing Shang, Liangzhi Kou, Chun Li and Zichen Deng
Nanomaterials 2022, 12(11), 1910; https://doi.org/10.3390/nano12111910 - 02 Jun 2022
Cited by 3 | Viewed by 1764
Abstract
In this work, molecular dynamics simulations are performed to investigate the mechanical properties of Janus WSSe and MoSSe monolayers considering the effects of structural anisotropy, temperature, and tensile strain rates. The results demonstrate that Janus WSSe and MoSSe monolayers show strong mechanical anisotropy [...] Read more.
In this work, molecular dynamics simulations are performed to investigate the mechanical properties of Janus WSSe and MoSSe monolayers considering the effects of structural anisotropy, temperature, and tensile strain rates. The results demonstrate that Janus WSSe and MoSSe monolayers show strong mechanical anisotropy under tension along the armchair and zigzag directions, respectively. This anisotropy displays distinct temperature dependence. When the coupled effects of the temperature and anisotropy are considered for the tensions along the zigzag direction, there is a transition of ductile-to-brittle failure in the Janus WSSe monolayer at the critical temperature range of 80~90 K due to the competition between atomic thermal vibrations and structural bending/wrinkles. This phenomenon is further confirmed by both stress–strain curves and structural evolutions of the systems. Finally, a strain rate hardening mechanism is found when various strain rates are applied, and it demonstrates that the Janus monolayer could maintain stable mechanical properties under different loading conditions. Our investigations provide a helpful reference for subsequent theoretical and experimental studies on the mechanical properties of Janus monolayer structures and could shed some light on the design of promising nanoscale functional devices based on Janus transition-metal dichalcogenides. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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13 pages, 4233 KiB  
Article
Evolution of Preset Void and Damage Characteristics in Aluminum during Shock Compression and Release
by Ya-Ting Wan, Jian-Li Shao, Guang-Ze Yu, Er-Fu Guo, Hua Shu and Xiu-Guang Huang
Nanomaterials 2022, 12(11), 1853; https://doi.org/10.3390/nano12111853 - 28 May 2022
Cited by 1 | Viewed by 1551
Abstract
It is well known that initial defects play an essential role in the dynamic failure of materials. In practice, dynamic tension is often realized by release of compression waves. In this work, we consider void-included single-crystal aluminum and investigate the damage characteristics under [...] Read more.
It is well known that initial defects play an essential role in the dynamic failure of materials. In practice, dynamic tension is often realized by release of compression waves. In this work, we consider void-included single-crystal aluminum and investigate the damage characteristics under different shock compression and release based on direct atomistic simulations. Elastic deformation, limited growth and closure of voids, and the typical spall and new nucleation of voids were all observed. In the case of elastic deformation, we observed the oscillatory change of void volume under multiple compression and tension. With the increase of impact velocity, the void volume reduced oscillations to the point of disappearance with apparent strain localization and local plastic deformation. The incomplete or complete collapsed void became the priority of damage growth under tension. An increase in sample length promoted the continuous growth of preset void and the occurrence of fracture. Of course, on the release of strong shock, homogeneous nucleation of voids covered the initial void, leading to a wider range of damaged zones. Finally, the effect of the preset void on the spall strength was presented for different shock pressures and strain rates. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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13 pages, 5712 KiB  
Article
Atomistic Simulations of the Permeability and Dynamic Transportation Characteristics of Diamond Nanochannels
by Bingqing Li, Bin Dong, Tianxiang Shi, Haifei Zhan and Yongqiang Zhang
Nanomaterials 2022, 12(11), 1785; https://doi.org/10.3390/nano12111785 - 24 May 2022
Cited by 3 | Viewed by 1518
Abstract
Through atomistic simulations, this work investigated the permeability of hexagonal diamond nanochannels for NaCl solution. Compared with the multilayer graphene nanochannel (with a nominal channel height of 6.8 Å), the diamond nanochannel exhibited better permeability. The whole transportation process can be divided into [...] Read more.
Through atomistic simulations, this work investigated the permeability of hexagonal diamond nanochannels for NaCl solution. Compared with the multilayer graphene nanochannel (with a nominal channel height of 6.8 Å), the diamond nanochannel exhibited better permeability. The whole transportation process can be divided into three stages: the diffusion stage, the transition stage and the flow stage. Increasing the channel height reduced the transition nominal pressure that distinguishes the diffusion and flow stages, and improved water permeability (with increased water flux but reduced ion retention rate). In comparison, channel length and solution concentration exerted ignorable influence on water permeability of the channel. Further simulations revealed that temperature between 300 and 350 K remarkably increased water permeability, accompanied by continuously decreasing transition nominal pressure. Additional investigations showed that the permeability of the nanochannel could be effectively tailored by surface functionalization. This work provides a comprehensive atomic insight into the transportation process of NaCl solution in a diamond nanochannel, and the established understanding could be beneficial for the design of advanced nanofluidic devices. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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14 pages, 3278 KiB  
Article
Multiscale Simulation on the Thermal Response of Woven Composites with Hollow Reinforcements
by Xiaoyu Zhao, Fei Guo, Beibei Li, Guannan Wang and Jinrui Ye
Nanomaterials 2022, 12(8), 1276; https://doi.org/10.3390/nano12081276 - 08 Apr 2022
Cited by 3 | Viewed by 1310
Abstract
In this paper, we established a progressive multiscale model for a plain-woven composite with hollow microfibers and beads and investigated the general conductive thermal response. Micromechanic techniques were employed to predict the effective conductivity coefficients of the extracted representative volume elements (RVEs) at [...] Read more.
In this paper, we established a progressive multiscale model for a plain-woven composite with hollow microfibers and beads and investigated the general conductive thermal response. Micromechanic techniques were employed to predict the effective conductivity coefficients of the extracted representative volume elements (RVEs) at different scales, which were then transferred to higher scales for progressive homogenization. A structural RVE was finally established to study the influence of microscale parameters, such as phase volume fraction, the thickness of the fibers/beads, etc., on the effective and localized behavior of the composite system It was concluded that the volume fraction of the hollow glass beads (HGBs) and the thickness of the hollow fibers (HFs) had a significant effect on the effective thermal coefficients of the plain-woven composites. Furthermore, it was found that an increasing HGB volume fraction had a more significant effect in reducing the thermal conductivity of composite. The present simulations provide guidance to future experimental testing. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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8 pages, 1205 KiB  
Article
Lightweight and Flexible Graphene Foam Composite with Improved Damping Properties
by Tong Li, Juan Du, Mi Xu, Zhuoyu Song and Mingfa Ren
Nanomaterials 2022, 12(8), 1260; https://doi.org/10.3390/nano12081260 - 08 Apr 2022
Cited by 5 | Viewed by 1654
Abstract
As an elastomer, PDMS can effectively suppress vibration in various fields in a certain temperature range by its viscoelastic behavior in the vitrification transition region, but the vibration isolation effect is poor at high temperature. In this paper, a three-dimensional graphene oxide (GO) [...] Read more.
As an elastomer, PDMS can effectively suppress vibration in various fields in a certain temperature range by its viscoelastic behavior in the vitrification transition region, but the vibration isolation effect is poor at high temperature. In this paper, a three-dimensional graphene oxide (GO) foam is fabricated by solution processing method and freeze-drying techniques. After sequential infiltration synthesis, a GO-foam-reinforced PDMS nanocomposite (GO/PDMS) is fabricated with improved damping ability. By adjusting the content of GO, the micros-tructure of GO foam can be sensitively changed, which is crucial to the damping properties of composites. In this paper, by the dynamic mechanical analysis (DMA) of pure PDMS and five kinds of GO/PDMS composites, it is proved that the GO/PDMS composites developed in this work have reliable elasticity and viscoelasticity at 25 °C, which is 100 °C higher than the applicable temperature of pure PDMS. The storage modulus can reach 3.58 MPa, and the loss modulus can reach 0.45 MPa, which are 1.87 times and 2.0 times of pure PDMS, respectively. This GO-based nanocomposite is an ideal candidate for damping materials in passive vibration isolation devices. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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16 pages, 4590 KiB  
Article
A First-Principle Study of Interactions between Magnesium and Metal-Atom-Doped Graphene
by Yaoming Li, Xin Pei, Huang Zhang and Meini Yuan
Nanomaterials 2022, 12(5), 834; https://doi.org/10.3390/nano12050834 - 01 Mar 2022
Cited by 5 | Viewed by 2157
Abstract
In this study, the interactions of magnesium (Mg) atom and Mg(001) surface with different metal-atom-doped graphene were investigated using a density functional theory (DFT) method. For the interactions of magnesium with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene, it was found that [...] Read more.
In this study, the interactions of magnesium (Mg) atom and Mg(001) surface with different metal-atom-doped graphene were investigated using a density functional theory (DFT) method. For the interactions of magnesium with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene, it was found that the magnesium atoms were physisorbed into the hollow sites of the intrinsic graphene with only the smallest interaction energy (approximately −1.900 eV). However, the magnesium atoms tended to be chemisorbed on the doped graphene, which exhibited larger interaction energies and charge transfers. Additionally, the Zn-doped graphene displayed the largest interaction energy with the Mg atom (approximately −3.833 eV). For the interactions of Mg(001) with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene (intrinsic and doped graphene/Mg interface), doped atoms interacted with a Mg layer to make graphene wrinkle, resulting in a higher specific surface area and better stability. Mg–C chemical bonds were formed at the Al-, Zn-, and Zr-doped interface, and Mg–Mn chemical bonds were formed at the Mn-doped interface. This study provided the fundamental research for future research into doped atoms on graphene reinforced magnesium matrix composites. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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18 pages, 7182 KiB  
Article
Torsional Properties of Bundles with Randomly Packed Carbon Nanotubes
by Hanqing Wei, Heidi Zhi Jin Ting, Yongji Gong, Chaofeng Lü, Olga E. Glukhova and Haifei Zhan
Nanomaterials 2022, 12(5), 760; https://doi.org/10.3390/nano12050760 - 24 Feb 2022
Cited by 4 | Viewed by 1826
Abstract
Carbon nanotube (CNT) bundles/fibers possess promising applications in broad fields, such as artificial muscles and flexible electronics, due to their excellent mechanical properties. The as-prepared CNT bundles contain complex structural features (e.g., different alignments and components), which makes it challenging to predict their [...] Read more.
Carbon nanotube (CNT) bundles/fibers possess promising applications in broad fields, such as artificial muscles and flexible electronics, due to their excellent mechanical properties. The as-prepared CNT bundles contain complex structural features (e.g., different alignments and components), which makes it challenging to predict their mechanical performance. Through in silico studies, this work assessed the torsional performance of CNT bundles with randomly packed CNTs. It is found that CNT bundles with varying constituent CNTs in terms of chirality and diameter exhibit remarkably different torsional properties. Specifically, CNT bundles consisting of CNTs with a relatively large diameter ratio possess lower gravimetric energy density and elastic limit than their counterpart with a small diameter ratio. More importantly, CNT bundles with the same constituent CNTs but different packing morphologies can yield strong variation in their torsional properties, e.g., up to 30%, 16% and 19% difference in terms of gravimetric energy density, elastic limit and elastic constants, respectively. In addition, the separate fracture of the inner and outer walls of double-walled CNTs is found to suppress the gravimetric energy density and elastic limit of their corresponding bundles. These findings partially explain why the experimentally measured mechanical properties of CNT bundles vary from each other, which could benefit the design and fabrication of high-performance CNT bundles. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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17 pages, 8603 KiB  
Article
Exact Solutions for Torsion and Warping of Axial-Loaded Beam-Columns Based on Matrix Stiffness Method
by Wen-Hao Pan, Chuan-Hao Zhao, Yuan Tian and Kai-Qi Lin
Nanomaterials 2022, 12(3), 538; https://doi.org/10.3390/nano12030538 - 04 Feb 2022
Cited by 3 | Viewed by 2496
Abstract
The typically-used element torsional stiffness GJ/L (where G is the shear modulus, J the St. Venant torsion constant, and L the element length) may severely underestimate the torsional stiffness of thin-walled nanostructural members, due to neglecting element warping deformations. In order [...] Read more.
The typically-used element torsional stiffness GJ/L (where G is the shear modulus, J the St. Venant torsion constant, and L the element length) may severely underestimate the torsional stiffness of thin-walled nanostructural members, due to neglecting element warping deformations. In order to investigate the exact element torsional stiffness considering warping deformations, this paper presents a matrix stiffness method for the torsion and warping analysis of beam-columns. The equilibrium analysis of an axial-loaded torsion member is conducted, and the torsion-warping problem is solved based on a general solution of the established governing differential equation for the angle of twist. A dimensionless factor is defined to consider the effect of axial force and St. Venant torsion. The exact element stiffness matrix governing the relationship between the element-end torsion/warping deformations (angle and rate of twist) and the corresponding stress resultants (torque and bimoment) is derived based on a matrix formulation. Based on the matrix stiffness method, the exact element torsional stiffness considering the interaction of torsion and warping is derived for three typical element-end warping conditions. Then, the exact element second-order stiffness matrix of three-dimensional beam-columns is further assembled. Some classical torsion-warping problems are analyzed to demonstrate the established matrix stiffness method. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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13 pages, 3824 KiB  
Article
Atomistic Simulations on Metal Rod Penetrating Thin Target at Nanoscale Caused by High-Speed Collision
by Yong-Chao Wu, Jin-Ming Liu, Wei Xie, Qing Yin and Jian-Li Shao
Nanomaterials 2021, 11(11), 3160; https://doi.org/10.3390/nano11113160 - 22 Nov 2021
Cited by 1 | Viewed by 1716
Abstract
The penetration process has attracted increasing attention due to its engineering and scientific value. In this work, we investigate the deformation and damage mechanism about the nanoscale penetration of single-crystal aluminum nanorod with atomistic simulations, where distinct draw ratio (∅) and [...] Read more.
The penetration process has attracted increasing attention due to its engineering and scientific value. In this work, we investigate the deformation and damage mechanism about the nanoscale penetration of single-crystal aluminum nanorod with atomistic simulations, where distinct draw ratio (∅) and different incident velocities (up) are considered. The micro deformation processes of no penetration state (within 2 km/s) and complete penetration (above 3 km/s) are both revealed. The high-speed bullet can cause high pressure and temperature at the impacted region, promoting the localized plastic deformation and even solid-liquid phase transformation. It is found that the normalized velocity of nanorod reduces approximately exponentially during penetration (up < 3 km/s), but its residual velocity linearly increased with initial incident velocity. Moreover, the impact crater is also calculated and the corresponding radius is manifested in the linear increase trend with up while inversely proportional to the ∅. Interestingly, the uniform fragmentation is observed instead of the intact spallation, attributed to the relatively thin thickness of the target. It is additionally demonstrated that the number of fragments increases with increasing up and its size distribution shows power law damping nearly. Our findings are expected to provide the atomic insight into the micro penetration phenomena and be helpful to further understand hypervelocity impact related domains. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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13 pages, 6358 KiB  
Article
Microscopic and Macroscopic Fragmentation Characteristics under Hypervelocity Impact Based on MD and SPH Method
by Wei-Dong Wu, Jin-Ming Liu, Wei Xie, Yan Xing and Jian-Li Shao
Nanomaterials 2021, 11(11), 2953; https://doi.org/10.3390/nano11112953 - 04 Nov 2021
Cited by 2 | Viewed by 1899
Abstract
This work investigates the difference in the fragmentation characteristics between the microscopic and macroscopic scales under hypervelocity impact, with the simulations of Molecular Dynamics (MD) and Smoothed Particle Hydrodynamics (SPH) method. Under low shock intensity, the model at microscopic scale exhibits good penetration [...] Read more.
This work investigates the difference in the fragmentation characteristics between the microscopic and macroscopic scales under hypervelocity impact, with the simulations of Molecular Dynamics (MD) and Smoothed Particle Hydrodynamics (SPH) method. Under low shock intensity, the model at microscopic scale exhibits good penetration resistance due to the constraint of strength and surface tension. The bullet is finally embedded into the target, rather than forming a typical debris cloud at macroscopic scale. Under high shock intensity, the occurrence of unloading melting of the sample reduces the strength of the material. The material at the microscopic scale has also been completely penetrated. However, the width of the ejecta veil and external bubble of the debris cloud are narrower. In addition, the residual velocity of bullet, crater diameter and expansion angle of the debris cloud at microscopic scale are all smaller than those at macroscopic scale, especially for low-velocity conditions. The difference can be as much as two times. These characteristics indicate that the degree of conversion of kinetic energy to internal energy at the microscopic scale is much higher than that of the macroscopic results. Furthermore, the MD simulation method can further provide details of the physical characteristics at the micro-scale. As the shock intensity increases, the local melting phenomenon becomes more pronounced, accompanied by a decrease in dislocation atoms and a corresponding increase in disordered atoms. In addition, the fraction of disordered atoms is found to increase exponentially with the increasing incident kinetic energy. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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16 pages, 8222 KiB  
Article
Spallation Characteristics of Single Crystal Aluminum with Copper Nanoparticles Based on Atomistic Simulations
by Dong-Dong Jiang, Peng-Yu Chen, Pei Wang and An-Min He
Nanomaterials 2021, 11(10), 2603; https://doi.org/10.3390/nano11102603 - 03 Oct 2021
Cited by 10 | Viewed by 1827
Abstract
In this study, the effects of Cu nanoparticle inclusion on the dynamic responses of single crystal Al during shockwave loading and subsequent spallation processes have been explored by molecular dynamics simulations. At specific impact velocities, the ideal single crystal Al will not produce [...] Read more.
In this study, the effects of Cu nanoparticle inclusion on the dynamic responses of single crystal Al during shockwave loading and subsequent spallation processes have been explored by molecular dynamics simulations. At specific impact velocities, the ideal single crystal Al will not produce dislocation and stacking fault structure during shock compression, while Cu inclusion in an Al–Cu nanocomposite will lead to the formation of a regular stacking fault structure. The significant difference of a shock-induced microstructure makes the spall strength of the Al–Cu nanocomposite lower than that of ideal single crystal Al at these specific impact velocities. The analysis of the damage evolution process shows that when piston velocity up ≤ 2.0 km/s, due to the dense defects and high potential energy at the interface between inclusions and matrix, voids will nucleate preferentially at the inclusion interface, and then grow along the interface at a rate of five times faster than other voids in the Al matrix. When up ≥ 2.5 km/s, the Al matrix will shock melt or unloading melt, and micro-spallation occurs; Cu inclusions have no effect on spallation strength, but when Cu inclusions and the Al matrix are not fully diffused, the voids tend to grow and coalescence along the inclusion interface to form a large void. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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Article
3D Printed Multi-Functional Scaffolds Based on Poly(ε-Caprolactone) and Hydroxyapatite Composites
by Fan Liu, Honglei Kang, Zhiwei Liu, Siyang Jin, Guoping Yan, Yunlong Sun, Feng Li, Haifei Zhan and Yuantong Gu
Nanomaterials 2021, 11(9), 2456; https://doi.org/10.3390/nano11092456 - 21 Sep 2021
Cited by 17 | Viewed by 2551
Abstract
3D Printed biodegradable polymeric scaffolds are critical to repair a bone defect, which can provide the individual porous and network microenvironments for cell attachment and bone tissue regeneration. Biodegradable PCL/HA composites were prepared with the blending of poly(ε-caprolactone) (PCL) and hydroxyapatite nanoparticles (HA). [...] Read more.
3D Printed biodegradable polymeric scaffolds are critical to repair a bone defect, which can provide the individual porous and network microenvironments for cell attachment and bone tissue regeneration. Biodegradable PCL/HA composites were prepared with the blending of poly(ε-caprolactone) (PCL) and hydroxyapatite nanoparticles (HA). Subsequently, the PCL/HA scaffolds were produced by the melting deposition-forming method using PCL/HA composites as the raw materials in this work. Through a serial of in vitro assessments, it was found that the PCL/HA composites possessed good biodegradability, low cell cytotoxicity, and good biocompatibility, which can improve the cell proliferation of osteoblast cells MC3T3-E1. Meanwhile, in vivo experiments were carried out for the rats with skull defects and rabbits with bone defects. It was observed that the PCL/HA scaffolds allowed the adhesion and penetration of bone cells, which enabled the growth of bone cells and bone tissue regeneration. With a composite design to load an anticancer drug (doxorubicin, DOX) and achieve sustained drug release performance, the multifunctional 3D printed PCL/HA/DOX scaffolds can enhance bone repair and be expected to inhibit probably the tumor cells after malignant bone tumor resection. Therefore, this work signifies that PCL/HA composites can be used as the potential biodegradable scaffolds for bone repairing. Full article
(This article belongs to the Special Issue Nanomechanics and Plasticity)
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