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    Effective strain based on shear and principal strains in equal channel angular extrusion with outer curved corner

    , Article Computational Materials Science ; Volume 41, Issue 3 , 2008 , Pages 409-419 ; 09270256 (ISSN) Eivani, A. R ; Karimi Taheri, A ; Sharif University of Technology
    In this paper, with introducing and based on a new configuration of equal channel angular extrusion (ECAE) process, nominated as multi-stage equal channel angular extrusion, two relationships are derived to calculate the effective strain based on shear and principal strains. First, a solution is presented for evaluating the effective strain in multi-stage ECAE dies consisting of two or more ECAE sub-dies. Then, the solution is extended to calculate the effective strains in ECAE dies with outer curved corner. The effective strain based on shear strains shows an exact agreement with previously published results. The derived relationships were compared with each other, with the relationships... 

    Impact of Changes in Matric Suction on Dynamic Properties of Unsaturated Silty Soil from Small to Large Strain During Drying Path

    , M.Sc. Thesis Sharif University of Technology Banar, Shaya (Author) ; Haeri, Mohsen (Supervisor) ; Khosravi, Ali (Supervisor)
    Shear modulus and damping ratio are of the most important parameters for geotechnical structures during dynamic and seismic loading. Secant shear modulus is the slope of hysteresis shear stress-shear strain loop, and damping ratio is indicative of dissipation of waves energy during propagation in the soil. These parameters mainly depend on void ratio, stress state, and shear strain of the soil. Climate changes cause some drying and wetting process which changes the soil state from saturated to unsaturated form. Previous researches indicated that the shear modulus and damping ratio change with the amount of matric suction. During the drying process, the matric suction increases,therefore,... 

    Coupled effects of suction and degree of saturation on large strain shear modulus of unsaturated sands

    , Article Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 ; Vol. 2, issue , July , 2014 , p. 1559-1564 ; 978-1-138-00150-3 Jafarzadeh, F ; Ahmadinezhad, A ; Sadeghi, H ; Sharif University of Technology
    Predictions of soil behavior in response to dynamic loads require an understanding of dynamic properties of soil. Studies on dynamic properties of unsaturated soils at large-strains are quite limited, while some dynamic loadings, like earthquakes, are in the medium to large-strain ranges. A cyclic simple shear apparatus was developed to measure large-strain shear modulus and damping ratio under different matric suction or degree of saturation. Six cyclic tests, with referring to the soil-water retention curve, were conducted on clean medium sand. Results indicated that shear modulus slightly increases when suction varies from zero up to the air entry value. Approaching the residual value, a... 

    Development of an accurate finite element model for N-layer MR-laminated beams using a layerwise theory

    , Article Mechanics of Advanced Materials and Structures ; Volume 25, Issue 13 , 2018 , Pages 1148-1155 ; 15376494 (ISSN) Momeni, S ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Laminated composite beams incorporated with magneto-rheological fluid are being used in variety of critical applications. An N-layer magneto-rheological-laminated beam based on layerwise theory has been developed to study the dynamic characteristics. For simulation purpose, an MR-laminated beam with five layers is considered in which two layers filled with magneto-rheological and three layers are made of composite materials. The results of simulations are compared with existing layerwise, first-order shear-deformation theory and experimental tests where it shows the accuracy and functionality of the present model. The complex shear modulus of magneto-rheological fluid has been determined... 

    Crack-based healing master curve derived from linear amplitude sweep tests: a cohesive healing indicator for asphalt binders

    , Article Materials and Structures/Materiaux et Constructions ; Volume 54, Issue 4 , 2021 ; 13595997 (ISSN) Asadi, B ; Tabatabaee, N ; Hajj, R ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    This investigation employed an interrupted torsion fatigue test using the linear amplitude sweep procedure to assess the intrinsic self-healing potential of unaged, aged, rejuvenated, and re-aged asphalt binders. Continuous oscillatory shear strain loading at different damage levels were interrupted with a single rest period of different durations. An index based on the decrease in crack length following the rest period (Ha) has been defined to accurately reflect the occurrence of healing. The results indicate that Ha is higher at lower damage levels and for longer rest-period durations. The amount of irreversible crack growth increased with an increase in crack propagation and aging level.... 

    Interlaminar hygrothermal stresses in laminated plates

    , Article International Journal of Solids and Structures ; Volume 44, Issue 25-26 , 2007 , Pages 8119-8142 ; 00207683 (ISSN) Bahrami, A ; Nosier, A ; Sharif University of Technology
    Within the elasticity formulation the most general displacement field for hygrothermal problems of long laminated composite plates is presented. The equivalent single-layer theories are then employed to determine the global deformation parameters appearing in the displacement fields of general cross-ply, symmetric, and antisymmetric angle-ply laminates under thermal and hygroscopic loadings. Reddy's layerwise theory is subsequently used to determine the local deformation parameters of various displacement fields. An elasticity solution is also developed in order to validate the efficiency and accuracy of the layerwise theory in predicting the interlaminar normal and shear stress... 

    The effects of nonlinearities on the vibration of viscoelastic sandwich plates

    , Article International Journal of Non-Linear Mechanics ; Vol. 62 , 2014 , Pages 41-57 ; ISSN: 00207462 Mahmoudkhani, S ; Haddadpour, H ; Navazi, H. M ; Sharif University of Technology
    The nonlinear free and forced bending vibration of sandwich plates with incompressible viscoelastic core is investigated under the effects of different source of nonlinearities. For the core constrained between stiffer layers, the transverse shear strains, as well as the rotations are assumed to be moderate. The linear and quadratic displacement fields are also adopted for the in-plane and out-of-plane displacements of the core, respectively. The assumption of moderate transverse strains requires a nonlinear constitutive equation which is obtained from a single-integral nonlinear viscoelastic model using the assumed order of magnitudes for linear strains and rotations. The 5th-order method... 

    Experimental study on dynamic properties of sand with emphasis on the degree of saturation

    , Article Soil Dynamics and Earthquake Engineering ; Volume 32, Issue 1 , 2012 , Pages 26-41 ; 02677261 (ISSN) Jafarzadeh, F ; Sadeghi, H ; Sharif University of Technology
    Cyclic drained and undrained tests were performed in a modified simple shear device in order to specifically investigate the effect of saturation ratio on shear modulus and damping parameters of sand. In addition to the degree of saturation, the effects of number of cycles, vertical consolidation stress, shear strain amplitude and relative density on dynamic properties of sand were investigated. Dynamic stiffness and damping characteristic were found to be substantially independent of saturation ratio in the range of 25-75%. However, by approaching the full saturation state, the values of modulus fall sharply and damping of loose samples increases dramatically from corresponding values of... 

    Dynamic parameters of saturated and unsaturated sand at different ranges of shear strain levels in cyclic simple shear tests

    , Article 14th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering ; 2011 Jafarzadeh, F ; Golshan, Z ; Sharif University of Technology
    In order to evaluate dynamic properties of Babolsar and Toyoura sands at saturation levels of 25, 50, 75 & 100%, a series of cyclic simple shear tests were carried out. The SGI type cyclic simple shear device was used to study the shear modulus, G, and damping ratio, D, of the above mentioned sands at cyclic shear strain of 0.5, 5 & 10%. The effect of degree of saturation (S), vertical consolidation stress (σ vc) and number of loading cycles (N) were investigated. On the basis of the tests results, the shear modulus approximately remains constant by change of degree of saturation from 25 to 50% and decreases when reaches the degree of saturation 75%. Damping ratio approximately is constant... 

    Nonlinear displacement-based and hybrid-mixed quadrilaterals for three-dimensional stress analysis through sampling surfaces formulation

    , Article Thin-Walled Structures ; Volume 155 , October , 2020 Kulikov, G. M ; Bohlooly, M ; Plotnikova, S. V ; Kouchakzadeh, M. A ; Glebov, A. O
    Elsevier Ltd  2020
    The finite deformation displacement-based and hybrid-mixed four-node quadrilateral elements using the sampling surfaces (SaS) technique are developed. The SaS formulation is based on choosing inside the plate N not equally spaced SaS parallel to the middle surface to introduce the displacements of these surfaces as basic plate unknowns. Such choice of unknowns with the consequent use of Lagrange polynomials of degree N–1 in the thickness direction permits the presentation of the plate formulation in a very compact form. The SaS are located at only Chebyshev polynomial nodes that allows one to minimize uniformly the error due to the Lagrange interpolation. To circumvent shear locking and have... 

    Vibration Analysis of viscoelastic Sandwich Plates Under the Effects of Nonlinearities and Random Excitations

    , Ph.D. Dissertation Sharif University of Technology Mahmoudkhani, Saeed (Author) ; Haddadpour, Hassan (Supervisor)
    Different aspects of oscillatory behaviors of sandwich structures with viscoelastic cores are investigated in the present study in four parts. In the first part, an analytical study is conducted to determine the variation of linear frequencies and damping ratio of different families of modes with system parameters. The participation of different families of modes such as the so-called pumping or thickness-shear modes along with the overall bending modes in the transverse response of the structure to transverse wide-band excitation is also investigated in this part. The formulation of the problem is established by assuming quadratic variation of displacement components of the core through the... 

    Determination of Strain Dependent Dynamic Parameters of Unsaturated a Silty Soil During Drying path using Resonant Column-Torsional Shear Device

    , M.Sc. Thesis Sharif University of Technology Zahed Kameh Olya, Vahid (Author) ; Haeri, Mohsen (Supervisor)
    Shear modulus and damping ratio are the most important parameters for evaluating the performance of geotechnical systems under seismic and dynamic loads. According to the definition, secant shear modulus is the slope of the hysteresis shear stress-shear strain loop and damping ratio indicates the dissipation of wave energy during propagation in the soil. These parameters depend on stress state, shear strain and void ratio of the soil. Shear strain amplitude has an important effect on the behavior of shear modulus and damping ratio and it is necessary to study the behavior of these parameters in the range of small to large strains. In addition to dynamic loading, climate change and wet and... 

    Sandwich beam model for free vibration analysis of bilayer graphene nanoribbons with interlayer shear effect

    , Article Journal of Applied Physics ; Vol. 115, issue. 17 , May , 2014 ; ISSN: 00218979 Nazemnezhad, R ; Shokrollahi, H ; Hosseini-Hashemi, S ; Sharif University of Technology
    In this study, sandwich beam model (SM) is proposed for free vibration analysis of bilayer graphene nanoribbons (BLGNRs) with interlayer shear effect. This model also takes into account the intralayer (in-plane) stretch of graphene nanoribbons. The molecular dynamics (MD) simulations using the software LAMMPS and Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential are done to validate the accuracy of the sandwich model results. The MD simulation results include the two first frequencies of cantilever BLGNRs with different lengths and two interlayer shear moduli, i.e., 0.25 and 4.6GPa. These two interlayer shear moduli, 0.25 and 4.6GPa, can be obtained by sliding a small... 

    Influence of fines content and type on the small-strain shear modulus of sand

    , Article Scientia Iranica ; Vol. 21, issue. 4 , 2014 , p. 1281-1296 Paydar, N. A ; Ahmadi, M. M ; Sharif University of Technology
    The small-strain shear modulus, Go, is an important fundamental soil property. Although many studies have been conducted on this property for clean sands and pure clays, small-strain behavior for mixtures of sand and fines has been less addressed. This paper presents the results of a comprehensive laboratory study on G0 value of sand containing various amounts of different fines. To this aim, bender elements were integrated into a conventional triaxial apparatus, and shear wave velocity was measured on samples of sand with different amounts of highly-plastic, medium-plastic, low-plastic, or non-plastic fines at different void ratios. Measuring the shear wave velocity and thus... 

    The cold welding of copper to aluminum using equal channel angular extrusion (ECAE) process

    , Article Journal of Materials Processing Technology ; Volume 211, Issue 6 , June , 2011 , Pages 1034-1043 ; 09240136 (ISSN) Zebardast, M ; Taheri, A. K ; Sharif University of Technology
    In this research, it is shown that the production of bimetallic Al/Cu rod by cold ECAE process is feasible. The mechanism of the cold weld between the copper sheath and aluminum core is assessed using the characteristics of the mating surfaces both theoretically and by examining the SEM micrographs of the peeled surfaces. It is shown that the stretch produced by the shear strain in the process leads to the fracture of the work-hardened layer of the mating surfaces and then by extruding the virgin metal through the cavities of the cracks a cold weld is developed between the sheath and core of the rod. To achieve the cold weld, a threshold surface stretch of about 59% is required. It is shown... 

    Impact of void ratio and state parameters on the small strain shear modulus of unsaturated soils

    , Article 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability ; 2015 , Pages 241-246 Khosravi, A ; Gheibi, A ; Rahimi, M ; McCartney, J. S ; Haeri, S. M
    The unsaturated small strain shear modulus, Gmax, is a key reference value in predicting relationships between dynamic shear modulus and shear strain amplitude and is thus a key quantity to properly model the behavior of dynamically-loaded geotechnical systems such as pavements, rail beds, and machine foundations. From the interpretation of the experimental Gmax results for unsaturated soils, different definitions of trends between Gmax and the stress state of the unsaturated soils and material properties are proposed. However, in most of trends, the relationship between the stress state and void ratio is considered and the effect of void ratio on the unsaturated small strain shear modulus... 

    Scattering of an anti-plane shear wave by an embedded cylindrical micro-/nano-fiber within couple stress theory with micro inertia

    , Article International Journal of Solids and Structures ; Volume 58 , April , 2015 , Pages 73-90 ; 00207683 (ISSN) Shodja, H. M ; Goodarzi, A ; Delfani, M. R ; Haftbaradaran, H ; Sharif University of Technology
    Elsevier Ltd  2015
    The inadequacy of traditional theory of elasticity in describing such a phenomenon as dispersion associated to a propagating wave with wavelength comparable to the intrinsic length of the medium of interest is well-known. Moreover, under certain circumstances it is incapable of capturing all the propagating waves. A remedy to such dilemmas is the employment of the more accurate higher order continuum theories which give rise to the appearance of at least one new characteristic length in the formulation. The experimental evidences as well as lattice dynamic analysis suggest that, although higher order continuum theories result in some improvements, but cannot fully overcome the... 

    Suction-induced hardening effects on the shear modulus of unsaturated silt

    , Article International Journal of Geomechanics ; Volume 16, Issue 6 , 2016 ; 15323641 (ISSN) Khosravi, A ; Salam, S ; McCartney, J. S ; Dadashi, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    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... 

    Layerwise theory in modeling of magnetorheological laminated beams and identification of magnetorheological fluid

    , Article Mechanics Research Communications ; Volume 77 , 2016 , Pages 50-59 ; 00936413 (ISSN) Naji, J ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Elsevier Ltd 
    In recent years, structures integrated with magnetorheological (MR) fluid have been considered for their tunable dynamic characteristics. Shear modulus of MR layer in composite structure is dramatically lower than the elastic layers, leading to high shear deformation inside the MR layer, thus classical theories are not accurate enough to predict the dynamic behavior of such structures. In present study a layerwise displacement theory has been utilized to predict a more accurate deformation for MR-composite beam and equation of motions derived using finite element model (FEM). ASTM E756-98 was employed to evaluate the complex shear modulus of MR fluid. By experimental test a practical... 

    The effects of die geometry in tube channel pressing: Severe plastic deformation

    , Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 230, Issue 1 , 2016 , Pages 263-272 ; 14644207 (ISSN) Farshidi, MH ; Kazeminezhad, M ; Sharif University of Technology
    SAGE Publications Ltd 
    The effects of die geometry on the deformation behavior of aluminum 6061 alloy tube in a novel severe plastic deformation (SPD) process called tube channel pressing (TCP) were studied using the Abaqus 6.10 software. Using the optimized die geometry, 1 to 3 passes of TCP is imposed not only to validate the simulation results, but also to investigate the performance of TCP as a SPD process. The finite element method (FEM) simulation results show that the moderated plastic strain, the lower inhomogeneity in distribution of plastic strain, and the lower risk of fracture during process can be obtained using the proper die geometry. In addition, the imposed strain is a mixture of shear strain and...