Article
Mathematics, Interdisciplinary Applications
Bilal Ahmed, George Z. Voyiadjis, Taehyo Park
Summary: In this work, a nonlocal gradient enhanced damage model for concrete is proposed to account for shear induced damage, based on a stress decomposition. The model is an extension of a local plasticity damage model, capable of handling directional dependency of damage, pure shear, biaxial damage, activation/deactivation of damage, and microcracks opening/closure. The model is implemented in Abaqus and tested using examples of mixed crack mode and mode-I cracking to demonstrate its performance.
COMPUTATIONAL MECHANICS
(2021)
Article
Engineering, Mechanical
Jianfeng Zhao, Bo Zhang, Dabiao Liu, Avraam A. Konstantinidis, Guozheng Kang, Xu Zhang
Summary: This study has reformulated Aifantis' SGP model by incorporating a power-law relation for strain-dependent ILS and considering the grain size effect. The results show that the ILS depends on both the sample size and grain size and can be described by the strain hardening exponent.
ACTA MECHANICA SINICA
(2022)
Article
Mechanics
Chien H. Thai, A. J. M. Ferreira, H. Nguyen-Xuan, P. Phung-Van
Summary: An nonlocal strain gradient meshfree model utilizing NSGT and HSDT is developed to analyze the bending and free vibration behaviors of FG nanoplates, considering nonlocal and strain gradient effects in nanostructures. Material properties are calculated using power index and Mori-Tanaka schemes. The deflections and natural frequencies of the FG nanoplates are solved through MK meshfree method, showing significant differences compared to classical theory in numerical examples.
COMPOSITE STRUCTURES
(2021)
Article
Mechanics
Hridya P. Lal, B. R. Abhiram, Debraj Ghosh
Summary: Higher-order elasticity theories are used to model mechanics at the nanoscale, but the length-scale parameters in these theories need to be evaluated through experiments or MD simulations. This study shows that the length-scale parameter in the modified strain gradient theory varies with dimensions, boundary conditions, and deformation level for carbon and boron nitride nanotubes. To address this issue, a supervised ML-based framework is developed, combining MD simulations, continuum formulation, and ML to predict the length-scale parameter for a given material, dimension, and boundary condition. This predictive tool reduces the need for expensive MD simulations and opens up possibilities for applying non-classical continuum theories to nanoscale mechanics problems.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2024)
Article
Engineering, Mechanical
Jun Jin, Ningdong Hu, Hongping Hu
Summary: In this study, the size-dependent band structure of a phononic crystal (PnC) was investigated using nonlocal strain gradient theory (NSGT). Numerical simulations showed that as the lattice constant approached the nano-scale, the size effect became more significant and resulted in a narrower band gap. It was also found that the strength of the size effect was mainly influenced by the thickness of the minimum connector.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2022)
Article
Materials Science, Multidisciplinary
A. Hosseini-Hooshyar, A. Nayebi
Summary: This study explores the use of low-order stress-gradient plasticity deformation theory to model size-dependent elastic and plastic deformation, comparing the results with classical plasticity models and strain gradient plasticity models. It focuses on the impact of physical length scales and passivation on material deformation, and compares the stress gradient plasticity model with strain gradient plasticity models.
MECHANICS OF MATERIALS
(2021)
Article
Engineering, Mechanical
Chien H. Thai, Lieu B. Nguyen, H. Nguyen-Xuan, P. Phung-Van
Summary: This paper presents a size-dependent numerical model for free vibration and bending analysis of hexagonal beryllium crystal nanoplates, taking into account both nonlocal and strain gradient effects under the assumption of anisotropic material behavior. The study shows that the bending and vibration behaviors of the nanoplates are influenced by various factors, and the natural frequency predicted by the nonlocal strain gradient theory depends on the relationship between the material length scale parameter and the nonlocal parameter.
INTERNATIONAL JOURNAL OF MECHANICS AND MATERIALS IN DESIGN
(2021)
Article
Materials Science, Multidisciplinary
Bo Wang, Kyoko Kaede, Sadahiro Tsurekawa, Katerina E. Aifantis
Summary: The effect of annealing with molten lead-bismuth eutectic alloy (mLBE) on the mechanical properties of T91 steel was studied. Micropillar compression tests were conducted and the stress-strain curves showed significant stochastic effects. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed slip deformation and slip planes along random grain boundaries (RGBs). The use of interfacial gradient plasticity allowed for the determination of the mechanical interface parameter, which was found to be lower in pillars with severe slip at the grain boundaries. Annealing with mLBE can result in softening in the overall stress-strain by lowering the mechanical interface energy of GBs.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Computer Science, Interdisciplinary Applications
Chien H. Thai, H. Nguyen-Xuan, P. Phung-Van
Summary: This paper presents a size-dependent high-order shear deformation theory (HSDT) model for analyzing the static and free vibration of laminated composite and sandwich nanoplates. By introducing scale parameters, the size effect of nanostructures is considered, and a virtual work principle is used to establish the bending and free vibration analysis model. The results show that the characteristics of the nanostructures are influenced by the geometry, boundary condition, length-to-thickness ratio, strain gradient parameter, and nonlocal parameter.
ENGINEERING WITH COMPUTERS
(2023)
Article
Mechanics
Amin Vahidi-Moghaddam, Arman Rajaei, Ehsan Azadi Yazdi, Mohammad Eghtesad, Dan Sorin Necsulescu
Summary: This paper investigates the nonlinear forced vibrations of homogeneous Euler-Bernoulli microbeams with clamped-clamped boundary conditions. By incorporating the nonlocal strain gradient theory, the governing nonlinear partial differential equation of motion including mid-plane stretching and damping effects is derived. Through the Galerkin approach, a reduced equation of motion is obtained under a central harmonic force. The perturbation technique is used to examine the nonlinear forced vibration behavior of the microbeam, and the simulation results show the role of size effect on the vibration behavior. Moreover, the effects of different physical parameters on the vibration behavior of the microbeam are studied. Finally, the proposed approach is compared with a numerical solution to validate the accuracy and validity of the presented analytical solution.
MECHANICS BASED DESIGN OF STRUCTURES AND MACHINES
(2023)
Article
Engineering, Civil
Ramin Panahi, Mohsen Asghari, Vahid Borjalilou
Summary: The paper presents an upgraded formulation for studying the nonlinear forced vibration behavior of a micro-rotating shaft-disks system. By incorporating geometrical nonlinearity and using the nonlocal strain gradient theory, the governing equations of the system are derived and solved to obtain the vibrational amplitude and natural frequencies. A parametric study is conducted to assess the impact of various factors on the motion amplitude and natural frequencies.
ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING
(2023)
Article
Computer Science, Interdisciplinary Applications
P. Phung-Van, Chien H. Thai
Summary: This paper introduces a novel nonlocal strain gradient isogeometric model for functionally graded carbon nanotube-reinforced composite nanoplates, capturing both nonlocal effects and strain gradient effects. The model is based on higher-order shear deformation theory and virtual work principle, and is analyzed using isogeometric analysis to study the deflection and natural frequency of nanoplates. The effects of nonlocal parameter, strain gradient parameter, CNT volume fraction, CNT distributions, and length-to-thickness ratios on deflection and natural frequency are examined through numerical results. Stiffness-softening and stiffness-hardening mechanisms are shown by the present model.
ENGINEERING WITH COMPUTERS
(2022)
Article
Computer Science, Interdisciplinary Applications
P. Phung-Van, H. Nguyen-Xuan, Chien H. Thai
Summary: This paper investigates the free vibration analysis of functionally graded graphene platelet-reinforced composites (FG GPLRC) plates using a nonlocal strain gradient isogeometric model based on the higher order shear deformation theory. Various distributed patterns of graphene platelets (GPLs) are considered, and the effects of different parameters on the natural frequencies of the nanoplates are examined. The results obtained in this study can serve as benchmark results for further research on FG GPLRC nanoplates.
ENGINEERING WITH COMPUTERS
(2023)
Article
Engineering, Multidisciplinary
P. Phung-Van, A. J. M. Ferreira, H. Nguyen-Xuan, Chien H. Thai
Summary: The nonlinear bending behavior of nanoporous metal foam plates was investigated using isogeometric analysis and higher-order plate theory. A scale dependent model was established taking into account the length scale and nonlocal parameters. It was found that factors such as pore dispersion and nonlocal parameters have a significant impact on the nonlinear deflection of the plate.
ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS
(2021)
Article
Mathematics
Ammar Melaibari, Alaa A. Abdelrahman, Mostafa A. Hamed, Ahmed W. Abdalla, Mohamed A. Eltaher
Summary: This study presents a mathematical model for investigating the dynamic behavior of a sandwich perforated nanobeam with flexoelectricity effect. Parametric studies show that the flexoelectric and piezoelectric parameters increase the vibration frequency of the nanobeam, while the nonlocal parameter reduces it.
Article
Engineering, Mechanical
Reem Abo Znemah, George Z. Voyiadjis, Paul Wood, Edris Akbari
Summary: This work studied the microstructure and mechanical hardness of Inconel 718 hexagonal honeycomb cellular structure manufactured by selective laser melting (SLM). The study found that the variation in cell wall thickness significantly affected grain size and hardness. Additionally, the hardness and strain rate sensitivity exhibited anisotropy in different directions. A model was modified to evaluate the factors influencing hardness.
JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME
(2022)
Article
Engineering, Mechanical
George Z. Voyiadjis, Hossein Bahrami, S. H. Hoseini
Summary: The effect of Ti-rich areas on the fracture of NiTi alloys is studied through experimental tests and numerical analyses. Tensile tests on NiTi smooth and notched bars with different notch sizes are conducted, and SEM observation and EDX analyses are performed. A numerical procedure based on the GTN micro-mechanical model is implemented using the finite element method. The results show that Ti-rich areas significantly affect fracture initiation, where cross-shaped cracks nucleate and accelerate the fracture process with excessive plastic deformation.
ENGINEERING FAILURE ANALYSIS
(2023)
Article
Materials Science, Multidisciplinary
George Z. Voyiadjis, Hossein Bahrami, S. H. Hoseini
Summary: In this study, an indirect approach using the response surface method (RSM) was employed to determine the GTN model parameters of a NiTi alloy. The method combined with polynomial regression was used to establish a relationship between the experimental results and GTN model parameters. Genetic algorithm technique was used to find the tuned values of the parameters. Simulation results with the calibrated parameters accurately predicted the fracture process of NiTi compared to experimental results.
JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE
(2023)
Article
Energy & Fuels
George Z. Voyiadjis, Edris Akbari, Peter I. Kattan
Summary: In this study, a damage model is presented to address the degradation of stiffness in lithium-ion battery components under mechanical loading conditions. The proposed model is based on the principles of continuum damage mechanics and employs a non-associated flow rule in an elastoplastic constitutive model. A robust and efficient VUMAT subroutine in Abaqus/Explicit is developed to evaluate the damage in the battery cell. The approach significantly reduces computational time for analyzing nonlinear large deformation battery cells. The constitutive equation and damage mechanism are validated by predicting force-displacement graphs and detecting damage in quasi-static loading conditions (radial, indentation, axial, and three-point bending).
JOURNAL OF ENERGY STORAGE
(2023)
Article
Engineering, Civil
Abdallah Ikbarieh, MohammadAli Izadifar, Murad Y. Abu-Farsakh, George Z. Voyiadjis
Summary: This paper presents the results of a finite element parametric study on the performance of a pile-supported embankment system built over soft soil with a geosynthetic-reinforced load transfer platform (GLTP). The study investigated various parameters and their effects on maximum geosynthetic tensile strain, settlement, and slope stability. The results showed that extending the GLTP to certain extents and increasing the number of geosynthetic layers can improve slope stability and reduce geosynthetic strains, while increasing the thickness of the top soft layer and the GLTP thickness can mainly affect strains and settlement.
TRANSPORTATION GEOTECHNICS
(2023)
Article
Materials Science, Multidisciplinary
Amir Shojaei, George Z. Voyiadjis
Summary: Damage healing mechanics has seen significant development in the past decade with the proposal of various constitutive models for different materials. However, in order to bridge the gap between the physics and the theoretical framework, it is necessary to consider the statistical nature of damage healing mechanics. This study proposes a framework that integrates statistical mechanics into the continuum of damage healing mechanics, allowing for more realistic simulations and optimization of healing methods and parameters.
INTERNATIONAL JOURNAL OF DAMAGE MECHANICS
(2023)
Review
Materials Science, Multidisciplinary
Bilal Ahmed, Taehyo Park, George Z. Voyiadjis
Summary: A comprehensive review of destructive testing techniques for understanding concrete behavior was conducted, summarizing the literature from the past three decades on topics including size effects, crack estimation and propagation, material property determination, creep and early age shrinkage behavior, and strain rate effects in concrete. The review focuses on experimental work related to each topic, while acknowledging the importance of theoretical basics and numerical implementation. Specific research findings and future directions are presented in each section.
INTERNATIONAL JOURNAL OF DAMAGE MECHANICS
(2023)
Article
Engineering, Civil
Murad Abu-Farsakh, Ahmad Souri, George Voyiadjis
Summary: In this study, three-dimensional finite element dynamic analyses were conducted to evaluate the effect of barge impact on the lateral performance of different pile group configurations. The results showed that the vertical pile group had the lowest lateral stiffness, while the battered and mixed pile groups had higher stiffness. The foundation contributed up to 82% of the total lateral force in the battered and mixed pile groups. The piles in the vertical pile group had notably higher bending moment due to larger pile cap displacement.
TRANSPORTATION RESEARCH RECORD
(2023)
Article
Materials Science, Multidisciplinary
Mohammed H. Saffarini, George Z. Voyiadjis
Summary: The plastic flow behavior of metallic foams has been rarely studied, despite its scientific and technological significance. This study employs atomistic simulations and previous research findings to propose a physical atomistic-continuum dislocations-based constitutive model for the plastic flow of metallic foams. The results of this work provide valuable insights for the design and manufacturing of metallic foams.
Article
Materials Science, Multidisciplinary
George Z. Voyiadjis, Reem Abo Znemah, Paul Wood
Summary: This study investigates the combined effect of microstructure and geometry on the deformation modes and energy absorption characteristics of laser powder bed fusion (LPBF) manufactured Inconel 718 (IN718) hexagonal honeycomb structures. The results show that LPBF-manufactured IN718 hexagonal honeycomb structures exhibit increasing plateau stress and specific energy absorption (SEA) with high SEA/plateau stress ratios, making them suitable for energy absorption applications. The reduction in cell wall thickness influences the instability failure mechanism for one direction, but not for another. A non-normalized anisotropic form of the Gibson-Ashby model is proposed to characterize the mechanical properties of the honeycomb structure. This study provides useful insights for optimizing the design of metallic lattice structures manufactured through additive manufacturing (AM).
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Construction & Building Technology
George Z. Voyiadjis, Peter I. Kattan
Summary: The development of undamageable and bimodal self-regenerating materials theories leads to the emergence of four-dimensional materials. The authors find that undamageable materials represent the ultimate form of Voyiadjis-Kattan materials as n approaches infinity, while bimodal materials represent the ultimate form of self-regenerating materials as n approaches infinity. This study establishes a solid connection between these recently developed theories and the future advancements in four-dimensional materials. It is concluded that both undamageable and bimodal materials are prime examples of four-dimensional materials, supported by rigorous mathematical and mechanical principles.
FRONTIERS IN BUILT ENVIRONMENT
(2023)
Article
Electrochemistry
George Z. Voyiadjis, Edris Akbari, Bartosz Luczak, Wojciech Sumelka
Summary: The study investigates the mechanical damage and internal short circuit (ISC) of cylindrical lithium-ion battery cells through non-destructive corrosion tests, and proposes a new analytical model to measure the contact area between the two cylinders (battery and indenter). The model assumes anisotropic hyperelasticity and predicts the increasing load-carrying capacity.
Article
Construction & Building Technology
Murad Abu-Farsakh, Mehdi Zadehmohamad, George Z. Voyiadjis
Summary: The integration of geosynthetic reinforcement in pavement structures can effectively increase their longevity. A finite element (FE) study was conducted to evaluate the impact of various parameters on the structural benefits of geosynthetic reinforcement. Results showed significant enhancement in rutting performance with the addition of geosynthetics, especially geogrids. The values of traffic benefit ratio (TBR), base effective resilient modulus (MR-eff), and factor of base course reduction (BCR) increased with increasing geosynthetic tensile stiffness and decreasing subgrade stiffness.
Article
Energy & Fuels
George Z. Voyiadjis, Edris Akbari
Summary: This study proposes a novel approach to convert load-depth curves into stress-strain curves in experimental indentation tests on cylindrical lithium-ion battery (LIB) cells. By combining analytical analysis and inverse optimization, the elastoplastic constitutive equation of LIB cells under cylindrical indenters is determined. The obtained load-depth curves successfully match the experimental loading-unloading curves, and a new definition of contact area is introduced. The analytical approach accurately captures the stress-strain curve and single indentation tests estimate the reduction of Young's modulus with increasing indentation depth. Damage consideration and measuring cell voltage further enhance the understanding of internal short circuit and thermal runaway in LIB cells.
Article
Mechanics
A. Abdul-Latif, F. Abed, Ch Oucif, G. Z. Voyiadjis
Summary: This study experimentally investigates the thermomechanical response of 42CrMo steel under various combinations of temperatures and strain-rates. Two different test configurations were used to characterize the flow stress of this steel, and key features such as work-hardening, grain size, dynamic strain aging, and microcavity formation were examined. The results showed that the strain-rate sensitivity of the steel increased with increasing temperatures, and high temperatures had a significant impact on the alloy's microstructure and mechanical properties.
ARCHIVES OF MECHANICS
(2022)
Article
Materials Science, Multidisciplinary
Nizar Lefi, Salem Neily, Roland Bonnet
Summary: This paper investigates the elastic field in a bi-material crystal with an angular dislocation line with one branch placed in the crystal and the other along a strongly bound or welded interface. The analysis formulates the elastic field of a closed dislocation loop and solves it using the knowledge of the Green's tensor of the bi-material. The study provides a faster calculation method and has important implications for solving interfacial angular dislocation problems.
PHILOSOPHICAL MAGAZINE
(2024)