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stress-analysis
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Relief of edge effects in bi-adhesive composite joints
, Article Composites Part B: Engineering ; Volume 108 , 2017 , Pages 153-163 ; 13598368 (ISSN) ; Tahani, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
Three-dimensional thermo-mechanical stress analysis of composite joints with bi-adhesive bonding is presented using the full layerwise theory. Based on three-dimensional elasticity theory, sets of fully coupled governing differential equations are derived using the principle of minimum total potential energy and are simultaneously solved using the state space approach. Results show that bi-adhesive bonding substantially relieves the edge effects. Moreover, series of parametric studies reveal the nonlinear effects of bonding length ratio and the relative stiffness and coefficient of thermal expansion of the mid- and side-adhesives. It is also concluded that the optimum design of a bi-adhesive...
Decoupled stability equation for buckling analysis of FG and multilayered cylindrical shells based on the first-order shear deformation theory
, Article Composites Part B: Engineering ; Volume 154 , 2018 , Pages 225-241 ; 13598368 (ISSN) ; Taati, E ; Asghari, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Based on the first-order shear deformation and Donnell's shell theory with von Karman non-linearity, one decoupled stability equation for buckling analysis of functionally graded (FG) and multilayered cylindrical shells with transversely isotropic layers subjected to various cases of combined thermo-mechanical loadings is developed. To this end, the equilibrium equations are uncoupled in terms of the transverse deflection, the force function and a new potential function. Using the adjacent equilibrium method, one decoupled stability equation which is an eighth-order differential equation in terms of transverse deflection is obtained and conveniently solved to present analytical expressions...
An analytical study on the elastic-plastic pure bending of a linear kinematic hardening curved beam
, Article International Journal of Mechanical Sciences ; Volume 144 , 2018 , Pages 274-282 ; 00207403 (ISSN) ; Arghavani, J ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this study, an analytical solution is presented for elastic-plastic pure bending of a linear kinematic hardening curved beam with rectangular cross section both in monotonic loading and unloading. Compared to exact plane plasticity solution (already reported in the literature in loading) which needs solution of a system of equations, the proposed method is based on the hyperbolic strain distribution on the cross section which yields a simple approximate solution. To this end, we employ Winkler's theory, and assume plane cross sections remain plane after loading proved by the exact elasticity and plasticity solutions for pure bending of curved beams with rectangular cross section. At the...
Effect of stress direction on the cyclic resistance of sand
, Article Proceedings of the Institution of Civil Engineers: Geotechnical Engineering ; Volume 171, Issue 2 , April , 2018 , Pages 109-120 ; 13532618 (ISSN) ; Zamanian, M ; Sharif University of Technology
ICE Publishing
2018
Abstract
In total, 55 undrained cyclic torsional shear tests were conducted at a constant mean confining stress, σ0m, constant intermediate principal stress ratios, b = (σ2 − σ3)/(σ1 − σ3), and principal stress directions, α. The cyclic resistance of loose, isotropically consolidated specimens exhibited a dip in strength, with the lowest values for α being 45°, an angle at which α was oriented such that the potential shear band directions dovetailed with the plane having the weakest strength (i.e. horizontal plane). For a given α, the cyclic resistance decreased to the lowest values for b = 0·5, at which the value of the principal stresses was different in the three major directions. For dense...
Validity of menard relation in dynamic compaction operations
, Article Proceedings of the Institution of Civil Engineers: Ground Improvement ; Volume 162, Issue 1 , 2009 , Pages 37-45 ; 17550750 (ISSN) ; Pak, A ; Shahir, H ; Sharif University of Technology
2009
Abstract
Dynamic compaction (DC) is a common soil improvement technique, used extensively worldwide. DC treatment design is usually based upon empirical relations and past experience. The common problem with all empirical relations is oversimplification of the mechanisms, and the use of parameters that are highly dependent on engineering judgement. In this paper, a developed finite-element code is used for modelling the impact behaviour of dry and moist sandy soil. The code is verified against the results of centrifuge tests. Then the validity of the popular Menard empirical relation for determination of improvement depth in DC design is investigated. The effect of initial relative density, tamper...
Creep damage evaluation of thick-walled spheres using a long-term creep constitutive model
, Article Journal of Mechanical Science and Technology ; Volume 23, Issue 10 , 2009 , Pages 2577-2582 ; 1738494X (ISSN) ; Shokouhi, N ; Sharif University of Technology
2009
Abstract
This paper describes a numerical model developed for the computation of creep damages in a thick-walled sphere subjected to an internal pressure and a thermal gradient. The model predicts the creep damage histories during the life of the sphere, owing to variations in stresses with time and through-thickness variations. The creep damage fraction is based on the Robinson's linear life fraction damage rule, which has been incorporated in a nonlinear time-dependent stress analysis. Following the stress histories, the effective stress histories are obtained and the creep damages are calculated and summed during the life of the sphere. The material long-term creep properties up to the rupture and...
Stress dependency of permeability, porosity and flow channels in anhydrite and carbonate rocks
, Article Journal of Natural Gas Science and Engineering ; Volume 70 , 2019 ; 18755100 (ISSN) ; Foroozesh, J ; Pourafshary, P ; Salmanpour, S ; Sharif University of Technology
Elsevier B.V
2019
Abstract
This study investigates the effect of stress magnitude and stress history on porosity and permeability values of anhydride and carbonate rocks. Porosity and permeability properties are measured for twelve anhydride and carbonate core samples under stress loading and unloading conditions. The results of permeability measurements show that tighter core samples are more stress dependent while the anhydride samples are generally more sensitive to the stress. The gap between stress loading and unloading (hysteresis) is more considerable at lower effective stress values. The results also indicate that the hysteresis is more noticeable in the anhydride core samples. The gas slippage factor is also...
A comparative study on the fatigue life of the vehicle body spot welds using different numerical techniques: Inertia relief and modal dynamic analyses
, Article Frattura ed Integrita Strutturale ; Volume 14, Issue 52 , 2020 , Pages 67-81 ; Farrahi, G. H ; Kashyzadeh, K. R ; Azadi, S ; Jahani, K ; Sharif University of Technology
Gruppo Italiano Frattura
2020
Abstract
Owing to the expensive and time-consuming nature of durability experiments, finite element based durability analysis is quite prevalent in the automotive industry. Numerical fatigue life analyses are typically divided into two different categories, the quasi-static methods which are faster and the dynamic methods which are more accurate. The aim of this paper is to compare the inertia relief and modal dynamic approaches in terms of formulation, accuracy and computation time. The chosen case study is the fatigue life of the vehicle body which is considered the main load-bearing component in a vehicle. By utilizing multi-body dynamics model and driving the vehicle on different standardized...
On the effect of detwinning-induced plasticity in compressive cyclic loading of NiTi shape memory alloys
, Article Mechanics of Materials ; Volume 148 , 2020 ; Arghavani, J ; Naghdabadi, R ; McGarry, J. P ; Sharif University of Technology
Elsevier B.V
2020
Abstract
A new inelastic mechanism, detwinning-induced plasticity (DIP), is proposed to model the response of NiTi SMAs to cyclic loading, based on thermodynamic considerations. DIP is incorporated into a constitutive framework for NiTi SMA. The constitutive framework also includes well-established inelastic mechanisms of phase transformation, transformation-induced plasticity, residual martensite, and detwinning. The model is constructed at the single crystal scale using the framework of thermodynamics and a crystal plasticity formulation. An explicit scale-transition rule is adopted for the simulation of polycrystalline materials, allowing direct comparison of the model predictions with published...
Block shear failure in welded gusset plates under combined loading
, Article Journal of Constructional Steel Research ; Volume 170 , July , 2020 ; Ghaderi Garekani, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Block shear failure in the base metal of welded steel connections is a potential failure mode affecting many steel structures. However, there are only a few studies on the block shear failure of welded connections under combined shear and axial loading. Combined loading is defined as a simultaneous loading parallel and perpendicular to the weld lines (or an inclined loading) in the plane of the connecting plate. In this research, a nonlinear finite element model is used to study the effect of connection geometry and weld group configuration on the block shear strength of welded connections under combined loading. In current design standards, the block shear failure planes are assumed to...
Probabilistic tolerance analysis of compliant assemblies
, Article 2007 World Congress, Detroit, MI, 16 April 2007 through 19 April 2007 ; 2007 ; 01487191 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
SAE International
2007
Abstract
Tolerance analysis is essential for estimation of final error of key product characteristic (KPC) in a mechanical assembly caused by errors in production and assembly of individual parts. Many mechanical assemblies, especially in automotive and aerospace industries, include sheet metal parts with a small ratio of thickness to width or length. Such parts are substantially flexible and thus, are prone to large errors due to elastic deformations during assembly production. Phenomena such as deformation due to fixture force, spring back, welding distortion and so on are common to such parts. Unlike tolerance analysis of rigid parts, here, the elastic deformation of the parts plays a significant...
Effects of conventional and severe shot peening on residual stress and fatigue strength of steel aisi 1060 and residual stress relaxation due to fatigue loading: experimental and numerical simulation
, Article Metals and Materials International ; Volume 27, Issue 8 , 2021 , Pages 2575-2591 ; 15989623 (ISSN) ; Farrahi, G. H ; Reza Kashyzadeh, K ; Unal, O ; Gugaliano, M ; Bagherifard, S ; Sharif University of Technology
Korean Institute of Metals and Materials
2021
Abstract
Abstract: This study investigates and compares the effects of different shot peening treatments including conventional and severe shot peening on microstructure, mechanical properties, fatigue behavior, and residual stress relaxation of AISI 1060 steel. Shot peening treatments were applied with two Almen intensities of 17 and 21 A and a wide ranges of coverage (100%–1500%). Various microstructural observations were carried out to analyze the evolution of microstructure. Microhardness, residual stress and surface roughness measurements and also axial fatigue test were performed. Moreover, the extent of the residual stress relaxation during cyclic loading was investigated by means of XRD...
Influence of joint arrangement on the fracture behavior of lead-free solder joints
, Article Journal of Electronic Materials ; Volume 50, Issue 4 , 2021 , Pages 2117-2128 ; 03615235 (ISSN) ; Nourani, A ; Honarmand, M ; Assempour, A ; Sharif University of Technology
Springer
2021
Abstract
The capability to standardize the fracture strength of solder joints is an effective tool to investigate the reliability of electronic devices. To achieve this purpose, in this research, the influences of joint arrangement (loading arm and load sharing) on the level of constraint imposed on joint deformation, fracture energy, and generally, fracture behavior of solder joints were investigated. Fracture behavior of solder joints using double-cantilever-beam (DCB) specimens as a function of loading arm and load sharing (i.e., the distance between two solder joints) was studied under mode I loading conditions at a strain rate of 0.03 s−1. By increasing the loading arm, the fracture force, Fci,...
Elastodynamic Green’s functions of transversely isotropic n-layer half- and full-spaces subjected to a surface or buried time-harmonic annular loading and associated material degeneracy
, Article Journal of Engineering Mathematics ; Volume 136, Issue 1 , 2022 ; 00220833 (ISSN) ; Shodja, H. M ; Rashidinejad, E ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
The elastodynamic behavior of layered media consisting of an arbitrary combination of isotropic and transversely isotropic layers is of great importance for many engineering applications. In this work, some appropriate elastodynamic Green’s functions pertinent to both the displacement and the stress fields are devised so that the problems associated with the n-layer semi-infinite and infinite media with any combinations of transversely isotropic and isotropic layers subjected to surface and buried oblique time-harmonic annular loading can all be treated in a unified manner. The material degeneracy arising due to the scenarios where one or more regions are isotropic is also discussed and...
A modified two-surface plasticity model for saturated and unsaturated soils
, Article Indian Geotechnical Journal ; Volume 52, Issue 4 , 2022 , Pages 865-876 ; 09719555 (ISSN) ; Hajitaheriha, M. M ; Hasani Motlagh, A ; Sadeghi, H ; Sharif University of Technology
Springer
2022
Abstract
A modified two-surface critical state plasticity model for saturated and unsaturated soil is presented in this study. The key modification in new model is inclusion of an alternative yield surface used to simulate the behavior of unsaturated soils in addition to corresponding saturated conditions. Moreover, a numerical technique is used to obtain an incremental stress–strain response from loading curves. Modification is applied continuously in each incremental step to return the final stress states and hardening parameters to the yield surface. Results revealed that the adopted modeling approach can predict two independent sets of laboratory unsaturated experiments under various conditions...
Investigating the behavior of cracks in welded zones of supporting structure of spherical pressure vessel under seismic loading
, Article Journal of Constructional Steel Research ; Volume 191 , 2022 ; 0143974X (ISSN) ; Ghazi, M ; Adibnazari, S ; Rofooei, F. R ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
In this paper, the numerical studies on the semi-elliptical crack behavior in different locations of welded zones in the supporting structure of a spherical pressure vessel under an earthquake are presented. The cracks in the welded zones of supporting structures under earthquake effects may jeopardize the safety of spherical pressure vessels and result in catastrophic failure. A detailed finite element sub-modeling technique is carried out to compute the mixed-mode stress intensity factors along the crack front. Furthermore, crack behavior with different aspect ratios a/c: 0.25, 0.5, and 0.75 at the weld and the heat-affected zone of the supporting structure is evaluated. The...
Semi-exact solution for thermo-mechanical analysis of functionally graded elastic-strain hardening rotating disks
, Article Communications in Nonlinear Science and Numerical Simulation ; Volume 17, Issue 9 , 2012 , Pages 3747-3762 ; 10075704 (ISSN) ; Hojjati, M. H ; Farrahi, G. H ; Alashti, R. A ; Sharif University of Technology
Abstract
In this paper, distributions of stress and strain components of rotating disks with non-uniform thickness and material properties subjected to thermo-elasto-plastic loading are obtained by semi-exact method of Liao's homotopy analysis method (HAM) and finite element method (FEM). The materials are assumed to be elastic-linear strain hardening and isotropic. The analysis of rotating disk is based on Von Mises' yield criterion. A two dimensional plane stress analysis is used. The distribution of temperature is assumed to have power forms with the hotter point located at the outer surface of the disk. A mathematical technique of transformation has been proposed to solve the homotopy equations...
Effect of pore geometry and loading direction on deformation mechanism of rapid prototyped scaffolds
, Article Acta Materialia ; Volume 60, Issue 6-7 , 2012 , Pages 2778-2789 ; 13596454 (ISSN) ; Bagheri, R ; Zehtab Yazdi, A ; Sharif University of Technology
2012
Abstract
Rapid prototyping is a promising technique for producing tissue engineering scaffolds due to its capacity to generate predetermined forms and structures featuring distinct pore architectures. The objective of this study is to investigate the influences of different pore geometries and their orientation with respect to the compressive loading direction on mechanical responses of scaffolds. Plastic models of scaffolds with cubic and hexagonal unit cells were fabricated by three-dimensional (3-D) printing. An in situ imaging technique was utilized to study the progressive compressive deformation of the scaffold models. In both cubic and hexagonal geometries, organized buckling patterns relevant...
Analytical approach to dynamic and vibration analysis of a spherical ball under contact stress
, Article Scientia Iranica ; Volume 18, Issue 6 , 2011 , Pages 1306-1312 ; 10263098 (ISSN) ; Hosseinzadeh, A ; Foumani, M. S ; Sharif University of Technology
2011
Abstract
This paper presents a nonlinear model to illustrate the effect of contact stress in the vibration behavior of mechanical components, especially rotating systems. The problem is considered in the case of the vertical vibration of a sphere on a plate. The Hertzian contact theory is used to obtain the relationship between contact force and the deflection of the mass center of the sphere. Modeling the system by a mass and a nonlinear spring, the vibration equation of the mass center of the sphere is derived. The method of LindstedtPoincar is implemented to solve the equation of motion, and obtain vibration characteristics under a compressive preload. The dependency of frequency on several...
Nonlinear vibration analysis of nano to micron scale beams under electric force using nonlocal theory
, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011 ; Volume 7 , August , 2011 , Pages 145-151 ; 9780791854846 (ISBN) ; Vaghasloo, Y. A ; Ahmadian, M. T ; Moheimani, R ; Sharif University of Technology
2011
Abstract
Electrostatically actuated beams are fundamental blocks of many different nano and micro electromechanical devices. Accurate design of these devices strongly relies on recognition of static and dynamic behavior and response of mechanical components. Taking into account the effect of internal forces between material particles nonlocal theories become highly important. In this paper nonlinear vibration of a microano doubly clamped and cantilever beam under electric force is investigated using nonlocal continuum mechanics theory. Implementing differential form of nonlocal constitutive equation the nonlinear partial differential equation of motion is reformulated. The equation of motion is...