Search for: stress-strain-relationship
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    Multiaxial stress-strain modeling and effect of additional hardening due to nonproportional loading

    , Article Journal of Mechanical Science and Technology ; Volume 21, Issue 8 , 2007 , Pages 1153-1161 ; 1738494X (ISSN) Rashed, G ; Ghajar, R ; Farrahi, G ; Sharif University of Technology
    Korean Society of Mechanical Engineers  2007
    Most engineering components are subjected to multiaxial rather than uniaxial cyclic loading, which causes multiaxial fatigue. The pre-requisite to predict the fatigue life of such components is to determine the multiaxial stressstrain relationship. In this paper the multiaxial cyclic stress-strain model under proportional loading is derived using the modified power law stress-strain relationship. The equivalent strain amplitude consisted of the normal strain excursion and maximum shear strain amplitude is used in the proportional model to include the additional hardening effect due to nonproportional loading. Therefore a new multiaxial cyclic stress-strain relationship is devised for out of... 

    Shear capacity of C-shaped and L-shaped angle shear connectors

    , Article PLoS ONE ; Volume 11, Issue 8 , 2016 ; 19326203 (ISSN) Tahmasbi, F ; Maleki, S ; Shariati, M ; Ramli Sulong, N. H ; Tahir, M. M ; Sharif University of Technology
    Public Library of Science 
    This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress... 

    Constitutive modelling of cemented gravelly sands

    , Article Geomechanics and Geoengineering ; Volume 4, Issue 2 , 2009 , Pages 123-139 ; 17486025 (ISSN) Haeri, S. M ; Hamidi, A ; Sharif University of Technology
    A constitutive model is developed for a cemented gravelly sand. The model is based on the separation of the cemented soil to the uncemented part and cemented bonds and combining the mechanical behaviour of each part using consistency and energy equilibrium equations. The uncemented part was modelled using the Pastor et al. (1985) model for sands. A new model was developed and proposed for the cemented bonds. Combination of these parts resulted in the modelling of cemented soil behaviour with a very good consistency both in drained and undrained conditions. The pore pressure in undrained conditions and the volumetric strains in the drained state were also modelled successfully using this... 

    Some improvements on the unfolding inverse finite element method for simulation of deep drawing process

    , Article International Journal of Advanced Manufacturing Technology ; Vol. 72, issue. 1-4 , 2014 , pp. 447-456 ; ISSN: 02683768 Bostan Shirin, M ; Assempour, A ; Sharif University of Technology
    The linear unfolding inverse finite element method (IFEM) has been modified and enhanced by implementing large deformation relations. The method is helpful to predict forming severity of the part that should be deep drawn as well as its blank shape and strain distribution in preliminary design stage. The approach deals with minimization of potential energy and large deformation relations with membrane elements. To reduce the computation time, the part is unfolded properly on the flat sheet and treated as 2D problem. Moreover, the nonlinear stress-strain relationship of plastic material properties has been considered to increase the accuracy of the results. An experiment set up has been... 

    Evaluation of the effect of anisotropic consolidation and principle stress rotation on undrained behavior of silty sands

    , Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1637-1653 ; 10263098 (ISSN) Keyhani, R ; Haeri, S. M ; Sharif University of Technology
    Sharif University of Technology  2013
    The dependence of undrained behavior of silty sand on initial state of stress and direction of principal stresses with respect to vertical (ff) is assessed under generalized loading paths using hollow cylinder apparatus. During applying shear load, value of intermediate principal stress parameter (b) is held constant and ff value is increased from zero to the aimed value and held constant. Specimens are consolidated, both, isotropically and anisotropically to evaluate the effect anisotropic consolidation on the behavior of these soils. The wet tamping method was selected to prepare specimen. Shear loading was carried out under strain-controlled condition to capture post-peak strain-softening... 

    Thermodynamically consistent and scale-dependent phase field approach for crack propagation allowing for surface stresses

    , Article International Journal of Plasticity ; Volume 111 , 2018 , Pages 1-35 ; 07496419 (ISSN) Levitas, V. I ; Jafarzadeh, H ; Farrahi, G. H ; Javanbakht, M ; Sharif University of Technology
    Elsevier Ltd  2018
    A thermodynamically-consistent phase field approach for crack propagation which includes the following novel features is presented. (1) Scale dependency was included by relating the length scale to the number of cohesive interatomic planes at the crack tip. Because of this, the developed theory is applicable from the atomistic to the macroscopic scales. (2) The surface stresses (tension) are introduced by employing some geometrical nonlinearities even in small strain theory. They produce multiple contributions to the Ginzburg-Landau equation for crack propagation. (3) Crack propagation in the region with compressive closing stresses is eliminated by employing a stress-state-dependent kinetic... 

    Rock joint modeling using a visco-plastic multilaminate model at constant normal load condition

    , Article Geotechnical and Geological Engineering ; Volume 24, Issue 5 , 2006 , Pages 1449-1468 ; 09603182 (ISSN) Mahin Roosta, R ; Sadaghiani, M. H ; Pak, A ; Saleh, Y ; Sharif University of Technology
    Rock joints play an important role in the behavior of rock masses under normal and shear loading conditions. Numerical simulation of the behavior of jointed rock masses is not an easy task due to complexities involved in the problem such as joint roughness, joint shear strength, hardening and softening phenomenon and mesh dependency. In this study for modeling purposes, a visco-plastic multilaminate model considering hardening and softening effects has been employed. For providing the necessary data for numerical simulation, a series of laboratory experiments have been carried out on regular tooth-shape asperities made by gypsum, under constant normal load conditions. Shear stress-shear... 

    Molecular dynamics investigation of β-SiC behavior under three-axial tensile loading

    , Article Journal of Computational and Theoretical Nanoscience ; Volume 8, Issue 11 , 2011 , Pages 2187-2192 ; 15461955 (ISSN) Mortazavi, B ; Simchi, A ; Besharati Givi, M. K ; Rajabpour, A ; Sharif University of Technology
    Molecular dynamics (MD) simulations were used to study the mechanical behaviour of β-SiC at nano-scale under tensile loading. Effects of loading rate and tensile temperature on the mechanical properties and failure were studied. Modified embedded-atom method (MEAM) potential and Berendsen thermostat were utilized for modelling. Periodic boundary conditions were employed and the behaviour of material was analyzed under three-axial loading condition at which the stress- strain relation was acceptably size independent. It is shown that with increasing the loading rate from 5 m/s to 70 m/s, the failure strain increases without a remarkable change in the stress-strain relationship. The MD... 

    Effect of soil structure and disturbance on hydromechanical behavior of collapsible loessial soils

    , Article International Journal of Geomechanics ; Volume 17, Issue 1 , 2017 , Pages 1-15 ; 15323641 (ISSN) Mohsen Haeri, S ; Khosravi, A ; Akbari Garakani, A ; Ghazizadeh, S ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2017
    To characterize the role of specimen disturbance and structure in the hydromechanical behavior of collapsible soils, two sets of wetting-induced collapse and suction-controlled triaxial tests were conducted on intact and reconstituted specimens of a loessial soil taken from a loess deposit in Gorgan, a city in the northeastern Golestan province of Iran. The testing approach used an advanced triaxial testing device that was specifically modified to control pressures applied to a soil specimen and to monitor and measure the amount of changes in volume and water content of the soil specimens during testing using highly sensitive digital sensors with an accuracy of 60.01 cm3. Results of the... 

    A simple model for various types of concretes and confinement conditions based on disturbed state concept

    , Article Scientia Iranica ; Volume 25, Issue 2A , 2018 , Pages 557-564 ; 10263098 (ISSN) Hosseinali, M ; Toufigh, V ; Sharif University of Technology
    Sharif University of Technology  2018
    Concrete is widely used for many practices in Civil Engineering. Therefore, an understanding of its behavior helps engineers and researchers to perform more accurate and cost-effective analyses and designs. In this respect, several models have been proposed to predict the behaviors of concrete most of which are satisfactorily accurate. However, by increasing the accuracy of the models, their computational cost increases, too. In this study, a model with the least computational cost is proposed to predict the behaviors of various concretes and confinement conditions. This model does not require any experimental tests to determine its parameters. It was proved to be able to predict the... 

    Combination of water head control and axis translation techniques in new unsaturated cyclic simple shear tests

    , Article Soil Dynamics and Earthquake Engineering ; Volume 126 , 2019 ; 02677261 (ISSN) Ahmadinezhad, A ; Jafarzadeh, F ; Sadeghi, H ; Sharif University of Technology
    Elsevier Ltd  2019
    A cyclic simple shear device was modified for testing coarse-grained soils at unsaturated conditions. A combined methodology of controlling suction for the practical range of coarse-grained soil water retention curves was adopted. Water head control method was used to accurately control suction within capillary and transition zones of such soils. The axis translation technique, on the other hand, was employed as a complementary approach to reach higher suction values within residual zone. In order to evaluate the performance of the new setup, independent cyclic tests were carried out at various initial suctions including all key points and zones along the primary drying path. The analyses of... 

    On the modeling of human intervertebral disc annulus fibrosus: Elastic, permanent deformation and failure responses

    , Article Journal of Biomechanics ; Volume 102 , 2020 Ghezelbash, F ; Shirazi Adl, A ; Baghani, M ; Eskandari, A. H ; Sharif University of Technology
    Elsevier Ltd  2020
    As a primary load-resisting component, annulus fibrosus (AF) maintains structural integrity of the entire intervertebral disc. Experiments have demonstrated that permanent deformation and damage take place in the tissue under mechanical loads. Development of an accurate model to capture the complex behaviour of AF tissue is hence crucial in disc model studies. We, therefore, aimed to develop a non-homogenous model to capture elastic, inelastic and failure responses of the AF tissue and the entire disc model under axial load. Our model estimations satisfactorily agreed with results of existing uniaxial (along fiber, circumferential and axial directions) and biaxial tissue-level tests. The... 

    Effect of EPS beads in lightening a typical zeolite and cement-treated sand

    , Article Bulletin of Engineering Geology and the Environment ; Volume 80, Issue 11 , 2021 , Pages 8615-8632 ; 14359529 (ISSN) Khajeh, A ; Ebrahimi, S. A ; MolaAbasi, H ; Jamshidi Chenari, R ; Payan, M ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    The current study aims to assess the influence of EPS beads inclusion on the strength properties of stabilized poorly-graded sands. Various contents of zeolite and cement as stabilizing agents, with the total amounts of 4, 8, and 12% by dry soil weight, and also 0, 0.25, and 0.5% weight ratios of EPS beads (η) are examined. Zeolite is opted among a variety of pozzolanic materials so as to replace a part of cement (0, 10, 30, 50, 70, and 90%) due to its superior environmentally friendly properties. The stress–strain behavior, unconfined compressive strength (UCS), peak strain energy (Eu), and California bearing capacity (CBR) of the zeolite and cement-treated sand-EPS beads mixtures are... 

    Investigation of the effect of high +Gz accelerations on human cardiac function

    , Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 27 , 2013 , Pages 54-63 ; 17516161 (ISSN) Jamshidi, M ; Ahmadian, M. T ; Sharif University of Technology
    This study investigates the effect of body acceleration on human cardiac function. Finite element analysis is conducted to simulate geometrical and mechanical properties of human heart. Heart geometrical modeling in three-dimension is performed by segmentation of cardiac MRI images. The nonlinear mechanical behavior of myocardium is modeled by Mooney-Rivlin, Polynomial, Ogden and Yeoh hyperelastic material models. Stress-strain curves of myocardial tissue are obtained from experimental compression tests on bovine heart samples. The experimental results are employed for the evaluation of material coefficients by the nonlinear least squares method. Among hyperelastic models, the Yeoh model...