Loading...
Search for:
elastic-moduli
0.011 seconds
Total 146 records
Effects of saturation degrees, freezing-thawing, and curing on geotechnical properties of lime and lime-cement concretes
, Article Cold Regions Science and Technology ; Volume 160 , 2019 , Pages 242-251 ; 0165232X (ISSN) ; Saberian, M ; Tao, Z ; Mojtahedi, S.F ; Li, J ; Ghasemi, M ; Rezvani, S. S ; Li, W ; Sharif University of Technology
Elsevier B.V
2019
Abstract
There are very limited researches carried out to investigate the influence of saturation degrees, freezing-thawing, and curing times on geotechnical properties of lime concrete (LC) and lime-cement concrete (LCC) due to the capillary action and changes in groundwater table. Subsequently, the primary goal of this research is to investigate the influence of these parameters on mechanical properties of LC and LCC using unconfined compression tests, namely uniaxial compressive strength (UCS), stress-strain behavior, deformability index (I D ), secant modulus (E S ), failure strain, bulk modulus (K), resilient modulus (M R ), brittleness index (I B ), and shear modulus (G). At first, the...
Injectable in situ forming kartogenin-loaded chitosan hydrogel with tunable rheological properties for cartilage tissue engineering
, Article Colloids and Surfaces B: Biointerfaces ; Volume 192 , 2020 ; Chen, Y ; Wang, D ; Bagheri, R ; Solouk, A ; Wu, H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Limited regeneration capacity of cartilage can be addressed by tissue engineering approaches including localized delivery of bioactive agents using biomaterials. Although chitosan hydrogels have been considered as appropriate candidates for these purposes, however, their poor mechanical properties limit their real applications. Here, we develop in situ forming chitosan hydrogels with enhanced shear modulus by chemical modification of chitosan using N-(β-maleimidopropyloxy) succinimide ester (BMPS). Moreover, we utilize β-Glycerophosphate (β-GP) in the hydrogels for achieving thermosensitivity. We investigate the effects of BMPS, β-GP and chitosan concentration on rheological and swelling...
Weakly nonlocal micromorphic elasticity for diamond structures vis-à-vis lattice dynamics
, Article Mechanics of Materials ; Volume 147 , 2020 ; Moosavian, H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this work, after formulating the weakly nonlocal micromorphic equations of motion for non-Bravais crystals with general anisotropy, specialization to diamond structures is made. A critical dilemma is the determination of the elastic moduli tensor appearing in the equations of motion. From the equivalency of these equations with the pertinent equations obtained in the context of lattice dynamics, the expressions of the components of the elastic moduli tensors in terms of the atomic force constants are derived analytically. Subsequently, the atomic force constants are calculated via ab initio density functional perturbation theory (DFPT) with high precision. As a benchmark for the accuracy...
Nonlocal hcp kernel functions based on ab initio calculations: Pertinent dislocation problems revisited
, Article Mechanics of Materials ; Volume 160 , 2021 ; 01676636 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Eringen's nonlocal theory and an accurate determination of the nonlocal kernel functions for hexagonal close-packed (hcp) crystals are of interest. The kernel functions are closely related to the anisotropy as well as any crystalline symmetries. To this end, five new distinct nonlocal kernel functions which have the characteristics of discrete atomistic Green's functions in the stress space are obtained through consideration of the nonlocal dispersion relations associated with certain directions combined with ab initio Density Functional Perturbation Theory (DFPT) calculations of the pertinent phonon frequencies. This is the first work which provides the nonlocal hcp kernel functions...
Mechanical behaviors of titanium nitride and carbide MXenes: A molecular dynamics study
, Article Applied Surface Science ; Volume 566 , 2021 ; 01694332 (ISSN) ; Esfandiar, A ; Rajabpour, A ; Sharif University of Technology
Elsevier B.V
2021
Abstract
MXenes have recently witnessed significant evolution and advances in terms of their applications in different areas such as flexible electronics, energy storage devices, and coatings. Here, the mechanical properties of both pristine and functionalized Tin+1CnO2 and Tin+1NnO2 (n = 1, 2) are investigated utilizing classical molecular dynamics simulations. For eight different MXene structures, the stress-strain curves are calculated including Young's modulus, strength, and fracture strain. It is found that Ti2N holds the highest Young's modulus with the value of 517 GPa while Ti3C2 has the lowest one with the amount of 133 GPa. In addition, the strongest MXene structure is Ti2N while the...
Atomistic simulations of mechanical properties and fracture of graphene: A review
, Article Computational Materials Science ; Volume 210 , 2022 ; 09270256 (ISSN) ; Kouchakzadeh, M. A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Material properties and fracture characteristics are among the most prominent parameters that should be considered for a wide range of graphene applications. This article reviews recent advances in theoretical studies on the mechanical properties and fracture behaviors of graphene, focusing on the effect of various simulation models. Most studies investigated single-layer graphene sheets (SLGSs) under uniaxial tensile tests using different common interatomic potentials, particularly AIREBO. Although researchers have examined a similar problem, specifically for pristine graphene, the differences in the reported values are considerable. These discrepancies are most evident in fracture...
Atomistic study of the effect of crystallographic orientation on the twinning and detwinning behavior of NiTi shape memory alloys
, Article Computational Materials Science ; Volume 203 , 2022 ; 09270256 (ISSN) ; Izadifar, M ; Dolado, J. S ; Ramazani, A ; Sadrnezhaad, S. K ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Understanding the effect of crystallographic orientation on the twinnin/detwinning mechanisms in NiTi shape memory alloys at an atomistic scale can help to control and tune the mechanical properties and failure behavior of such materials. In this work, we employed classical molecular dynamics (MD) and density functional theory (DFT) computational methods to better understand how twinning and detwinning occurs through a combination of slip, twin, and shuffle on 〈0 1 0〉, 〈1 1 0〉, and 〈1 1 1〉 crystallographic orientations under uniaxial tensile test. Elastic constants including Young's Modulus (E), Bulk modulus (B), Poisson's ratio (ν), and Shear Modulus (G) are obtained and computed for...
An exact analysis for the hoop elasticity and pressure-induced twist of CNT-nanovessels and CNT-nanopipes
, Article Mechanics of Materials ; Volume 82 , 2015 , Pages 47-62A ; 01676636 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier
2015
Abstract
Carbon nanotubes (CNTs) with and without end caps may be used for fluid storage and transport, respectively, referred to as CNT-nanovessel and CNT-nanopipe. The determination of the stiffness in the hoop (circumferential) and radial directions, ideal hoop strength, and hoop stress-strain curve of such nanostructures is of particular interest. Due to the proposed viewpoint, a chiral free-standing single-walled CNT (SWCNT) has a natural angle of twist and natural extension along the axis of the tube. For example, for the SWCNT (9,3) with diameter of 0.85 nm and chirality angle of 13.9°, the natural angle of twist per unit length is 1.45×10-3 rad/nm. Previously, only Vercosa et al. (2010) who...
Adhesive and cohesive properties by indentation method of plasma-sprayed hydroxyapatite coatings
, Article Applied Surface Science ; Volume 253, Issue 11 , 2007 , Pages 4960-4965 ; 01694332 (ISSN) ; Ziaei Moayyed, A. A ; Mesgar, A. S. M ; Sharif University of Technology
Elsevier
2007
Abstract
Adhesive and cohesive properties of the plasma-sprayed hydroxyapatite (HA) coatings, deposited on Ti-6Al-4V substrates by varying the plasma power level and spray distance (SD), were evaluated by an indentation method. The crystallinity and the porosity decreased with increasing both of these two parameters. The microhardness value, Young's modulus (E) and coating fracture toughness (K C ) were found to increase with a combinational increase in spray power and SD. The Knoop and Vickers indentation methods were used to estimate E and K C , respectively. The critical point at which no crack appears at the interface was determined by the interface indentation test. This was used to define the...
Molecular dynamics simulation of nanoindentation of nanocrystalline Al/Ni multilayers
, Article Computational Materials Science ; Volume 112 , 2016 , Pages 175-184 ; 09270256 (ISSN) ; Farrahi, G. H ; Movahhedy, M. R ; Sharif University of Technology
Elsevier
Abstract
Molecular dynamics simulations are employed to investigate material properties of nanocrystalline aluminum and nanocrystalline Al/Ni multilayers at low temperature. For this purpose, both single crystal and nanocrystalline multilayers with different grain sizes and grain morphology are used as the substrate. The results of the simulations show that hardness and elastic modulus decrease with refinement of grain size in nanocrystalline aluminum and refinement of grain size and layer thickness in nanocrystalline Al/Ni multilayers, regardless of grain morphology. Furthermore, the angle between two adjacent grains, which is directly connected to the grain boundary thickness, has a great influence...
Evaluation of the effects of principal stress direction on shear modulus of unsaturated sand using hollow cylinder apparatus
, Article 7th International Conference on Earthquake Geotechnical Engineering, ICEGE 2019, 17 January 2019 through 20 January 2019 ; 2019 , Pages 3102-3108 ; 9780367143282 (ISBN) ; Ahmadi Givi, F ; Ahmadinezhad, A ; Silvestri F ; Moraci N ; Sharif University of Technology
CRC Press/Balkema
2019
Abstract
Determination of soil shear modulus is one of the most controversial topics in unsaturated soil dynamics. Due to the fact that soils have an anisotropic response, the shear strength and stiffness of geological materials are greatly dependent on the principal stress direction and the intermediate principal stress. In this study, the effects of principal stress direction on shear modulus of unsaturated medium-dense sand have been investigated using cyclic hollow cylinder apparatus. Three series of stress-controlled cyclic tests with different fixed principal stress directions were carried out on the sand sample under different values of suction. Results reveal that shear modulus of unsaturated...
Evaluation of the effects of principal stress direction on shear modulus of unsaturated sand using hollow cylinder apparatus
, Article 7th International Conference on Earthquake Geotechnical Engineering, ICEGE 2019, 17 January 2019 through 20 January 2019 ; Pages 3102-3108 , 2019 ; 9780367143282 (ISBN) ; Ahmadi Givi, F ; Ahmadinezhad, A ; Silvestri F ; Moraci N ; Sharif University of Technology
CRC Press/Balkema
2019
Abstract
Determination of soil shear modulus is one of the most controversial topics in unsaturated soil dynamics. Due to the fact that soils have an anisotropic response, the shear strength and stiffness of geological materials are greatly dependent on the principal stress direction and the intermediate principal stress. In this study, the effects of principal stress direction on shear modulus of unsaturated medium-dense sand have been investigated using cyclic hollow cylinder apparatus. Three series of stress-controlled cyclic tests with different fixed principal stress directions were carried out on the sand sample under different values of suction. Results reveal that shear modulus of unsaturated...
Effect of specimen preparation techniques on dynamic properties of unsaturated fine-grained soil at high suctions
, Article Canadian Geotechnical Journal ; Volume 54, Issue 9 , 2017 , Pages 1310-1319 ; 00083674 (ISSN) ; Baghbanrezvan, S ; Sadeghi, H ; Zhou, C ; Jafarzadeh, F ; Sharif University of Technology
Canadian Science Publishing
2017
Abstract
The seismic response of soil depends on proper evaluation and use of soil dynamic properties, including shear modulus and damping ratio at various strain levels. Despite extensive studies on the shear modulus and damping ratio of saturated soils, research on the dynamic properties of unsaturated fine-grained soils — especially at high suction — is limited. This study aims to investigate the dynamic properties of loess at a variety of initial states resulting from different specimen preparation techniques (reconstituted, recompacted, and intact) and their evolutions due to suction-induced desiccation. Results of resonant column tests show that at initial states, the specimen preparation...
On the theoretical and molecular dynamic methods for natural frequencies of multilayer graphene nanosheets incorporating nonlocality and interlayer shear effects
, Article Mechanics of Advanced Materials and Structures ; 2021 ; 15376494 (ISSN) ; Taati, E ; Asghari, M ; Sharif University of Technology
Bellwether Publishing, Ltd
2021
Abstract
In this paper, a multiplate nonlocal shear model and molecular dynamic simulations are presented to investigate the effects of interlayer shear and nonlocality on the natural frequencies of multilayer graphene sheets (MLGSs). From one aspect in the optimal design of such structures, the interaction between graphene layers, which can significantly vary the static and dynamic behavior due to lack of solidity of layers stack, should be considered. On the other hand, it is requied that the nonlocality phenomenon which has an effective role in the mechanical analysis of nanostructures is taken into account. To this aim, the equation of motion along with corresponding boundary conditions is...
Contribution of ordered-inordered phenomenon within the interphase region toward increasing elastic modulus in CNT/polymer nanocomposites
, Article Materials Science and Technology Conference and Exhibition 2015, MS and T 2015, 4 October 2015 through 8 October 2015 ; Volume 1 , October , 2015 , Pages 595-602 ; 9781510813939 (ISBN) ; Goodarzi Hosseinabadi, H ; NACE International ; Sharif University of Technology
Association for Iron and Steel Technology, AISTECH
2015
Abstract
Exceptional mechanical properties of carbon nanotubes (CNTs) such as high elastic modulus, stiffness and tensile strength have made them as promising reinforcement in polymer nanocomposite systems. The characteristics of CNTs/polymer interphase region directly affect the efficiency of nanotubes for improving the nanocomposite mechanical properties. In this work, the influence of chains alignment within the interphase region on elastic response of the nanocomposite is assessed using a novel ordered-inordered approach. The applicability of the presented approach is examined by implementing the approach on a series of reported data available in the literature. The effects of CNT content,...
Comparison of the experimental behavior of a shape memory alloy in compression and tension
, Article 2003 ASME International Mechanical Engineering Congress, Washington, DC., 15 November 2003 through 21 November 2003 ; Volume 68 , 2003 , Pages 471-478 ; 07334230 (ISSN) ; Ghorashi, M ; Inman, D. J ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2003
Abstract
The concept of Shape Memory Alloy (SMA) has been a subject of extensive research in the recent few years. In many SMA applications, wire elements have been used in order to control structural specifications like shape and stiffness. Since a wire can only be subjected to tensile forces, the available theoretical models for SMA discuss only the tensile loading. The present paper is an endeavor to overcome this shortcoming. It gives experimental results for tension and compression tests on specimens (having different geometries) made of an identical shape memory alloy. The corresponding results are compared with each other. Using stress-strain diagrams, several important material properties are...
Modeling and analysis of AN ultra light slow flyer with variable shape control surfaces using shape memory alloy actuators
, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 2 , 2004 , Pages 153-162 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Alemohamad, S. H ; Khiabani, R. H ; Khalighi, Y ; Sharif University of Technology
American Society of Mechanical Engineers
2004
Abstract
Applying flexible variable shape control surfaces (wing and elevator) structures is a way to increase efficiency and maneuverability of the planes, which is recently under research. In this paper, modeling of the flight of an unmanned ultra light plane is discussed. The modeling is done based on a real ultra light plane presented recently. To increase maneuverability of the plane, flexible variable shape structures are designed for the wing and the elevator. In design procedure, having an ultra light plane is considered. The elevator and the wing are used as control surfaces for longitudinal and lateral maneuvers respectively. Shape memory alloys (SMA) are used for reshaping the flexible...
Suction-induced hardening effects on the shear modulus of unsaturated silt
, Article International Journal of Geomechanics ; Volume 16, Issue 6 , 2016 ; 15323641 (ISSN) ; Salam, S ; McCartney, J. S ; Dadashi, A ; Sharif University of Technology
American Society of Civil Engineers (ASCE)
Abstract
The small-strain shear modulus Gmax is a key material parameter in modeling the behavior of soils subjected to dynamic loading. Recent experimental results indicate that seasonal weather interaction with near-surface soils causes Gmax to change by up to an order of magnitude in some climates, with a hysteretic response upon drying and wetting. The increase in Gmax during drying and the stiffer response during subsequent wetting have been postulated to be due to plastic hardening during drying. To further understand this behavior, a series of isotropic compression tests were performed on compacted silt specimens at different values of matric suction to evaluate changes in the preconsolidation...
Thermal buckling analysis of bridged single walled carbon nanotubes using molecular structural mechanics
, Article Journal of Applied Physics ; Volume 117, Issue 11 , 2015 ; 00218979 (ISSN) ; Badri Kouhi, E ; Sharif University of Technology
American Institute of Physics Inc
2015
Abstract
This paper is concerned with the stability analysis of bridged single walled carbon nanotubes (SWCNT) under temperature changes. A molecular structural mechanics model is utilized to investigate the free vibration frequencies and thermal buckling of SWCNT. In comparison with most of the previous studies, a temperature-variable thermal-expansion-coefficient is used that is negative under a certain temperature. Also thermal variation of Young's modulus of the CNTs is considered. Several studies are performed to investigate the critical temperature change due to heating and cooling of SWCNTs with different chiralities and slenderness ratios and the stability boundaries are determined
Hybrid anisotropic pentamode mechanical metamaterial produced by additive manufacturing technique
, Article Applied Physics Letters ; Volume 117, Issue 6 , 2020 ; Movahhedy, M. R ; Shishkovsky, I ; Hedayati, R ; Sharif University of Technology
American Institute of Physics Inc
2020
Abstract
Pentamode metamaterials are a type of extremal designer metamaterials, which are able to demonstrate extremely high rigidity in one direction and extremely high compliance in other directions. Pentamodes can, therefore, be considered as building blocks of exotic materials with any arbitrarily selected thermodynamically admissible elasticity tensor. The pentamode lattices can then be envisioned to be combined to construct intermediate extremal materials, such as quadramodes, trimodes, and bimodes. In this study, we constructed several primary types of anisotropic pentamode lattices (with midpoint positioning of 10%, 15%, 20%, 25%, 30%, 35%, and 42% of the main unit cell diagonal) and then...