• Steel and Composite Structures
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• v.46 no.3
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• pp.293-318
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• 2023

This study aims to examine the elastic stiffness properties of Elliptic-Braced Moment Resisting Frame (EBMRF) subjected to lateral loads. Installing the elliptic brace in the middle span of the frames in the facade of a building, as a new lateral bracing system not only it can improve the structural behavior, but it provides sufficient space to consider opening it needed. In this regard, for the first time, an accurate theoretical formulation has been developed in order that the elastic stiffness is investigated in a two-dimensional single-story single-span EBMRF. The concept of strain energy and Castigliano's theorem were employed to perform the analysis. All influential factors were considered, including axial and shearing loads in addition to the bending moment in the elliptic brace. At the end of the analysis, the elastic lateral stiffness could be calculated using an improved relation through strain energy method based on geometric properties of the employed sections as well as specifications of the utilized materials. For the ease of finite element (FE) modeling and its use in linear design, an equivalent element was developed for the elliptic brace. The proposed relation was verified by different examples using OpenSees software. It was found that there is a negligible difference between elastic stiffness values derived by the developed equations and those of numerical analysis using FE method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.2
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• pp.105-118
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• 2008

The newly developed analysis method for nanoindentation load-displacement curves are focused on not only obtaining elastic modulus and hardness values but also other mechanical properties, such as yield strength and strain hardening properties. Dao et al. developed a forward and reverse algorithm to extract the elasto-plastic properties of materials from the load-displacement curves obtained in nanoindentation test. These algorithms were only applicable for engineering metals (Poisson#s ratio 0.3) using the equivalent conical indenter of the Berkovich. However, the applicable metals are substantially limited because range of used in the finite element analysis is narrow. This study is designed to expand range of the applicable metals in the reverse algorithms established by Dao et al. and to improve the accuracy of that for extracting the elasto-plastic properties of materials. In this study, a representative strain was assumed to vary according to specific range of $E^*/{\sigma}_r$ and was defined as function of $E^*/{\sigma}_r$. Also, an initial unloading slope in reverse algorithms improved in this study was not considered as independent parameters of the load-displacement curves. The mechanical properties of materials for finite element analysis were modeled with the elastic modulus, E, the yield strength, ${\sigma}_y$, and the strain hardening exponents, n. We showed that the representative strain (0.033) suggested by Dao et al. was no longer applicable above the $E^*/{\sigma}_r$ of 400 and depended on values of $E^*/{\sigma}_r$. From these results, we constructed the dimensionless functions, in where the initial unloading slope was not included, for engineering metals up to $E^*/{\sigma}_r$ of 1500. These functions allow us to determine the mechanical properties with greater accuracy than Dao#s study.

• Advances in aircraft and spacecraft science
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• v.4 no.5
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• pp.585-611
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• 2017

This article covenants with the post buckling witticism of carbon nanotube reinforced composite (CNTRC) beam supported with an elastic foundation in thermal atmospheres with arbitrary assumed random system properties. The arbitrary assumed random system properties are be modeled as uncorrelated Gaussian random input variables. Unvaryingly distributed (UD) and functionally graded (FG) distributions of the carbon nanotube are deliberated. The material belongings of CNTRC beam are presumed to be graded in the beam depth way and appraised through a micromechanical exemplary. The basic equations of a CNTRC beam are imitative constructed on a higher order shear deformation beam (HSDT) theory with von-Karman type nonlinearity. The beam is supported by two parameters Pasternak elastic foundation with Winkler cubic nonlinearity. The thermal dominance is involved in the material properties of CNTRC beam is foreseen to be temperature dependent (TD). The first and second order perturbation method (SOPT) and Monte Carlo sampling (MCS) by way of CO nonlinear finite element method (FEM) through direct iterative way are offered to observe the mean, coefficient of variation (COV) and probability distribution function (PDF) of critical post buckling load. Archetypal outcomes are presented for the volume fraction of CNTRC, slenderness ratios, boundary conditions, underpinning parameters, amplitude ratios, temperature reliant and sovereign random material properties with arbitrary system properties. The present defined tactic is corroborated with the results available in the literature and by employing MCS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.461-464
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• 2004

In this paper, the elastic epoxy added elastomer having viscoelasticity to existing epoxy was measured thermal, structural properties through TGA(Thermogravimetric Analysis) and FESEM(Field Emission Scanning Electron Microscope). Specimens were made of dumbbell forms by the ratio of 5[phr], 10[phr], 15[phr], and 20[phr] by regulation with elastomer contents. The measurement temperature dimensions of TGA were $0[^{\circ}C]\;to\;800[^{\circ}C]$, and rising temperature was $5[^{\circ}C/min]$. And we observed structure through FESEM at the magnification of 1000times with the voltage of 15[kV] after breaking by quenching specimens. As thermal analysis results, we could know that thermal and structural properties was improved quantity according to decrease of elastomer contents. In general, thermal, structural properties of 15[phr] was excellent among the specimens.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.795-798
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• 2002

In this investigation, experimental attempts were made to observe and determine the variations in elastic of the PVC depending on the amounts of MBS added to the mixture, PVC/MBS, and also on the thicknesses of the specimens. An acoustic resonance technique was used for the tests in this investigation. It serves as a method to characterize properties of materials set in vibrational motions, which is initiated by low level stresses generated by externally supplied acoustic energy. Substantial variations were observed in the test results with the addition of the MBS to the PVC. It was found that the magnitudes of elastic constants decrease when MBS rubber was added in the range up to 9 phr and the shape factor effect in torsional vibration is more significant than the shape factor effect in flexural vibration.

• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.1-10
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• 2017

The present paper deals with the free vibration and buckling problem with consideration of surface properties of circular nanobeams and nanoarches. The Gurtin-Murdach theory is used for investigating the surface effects parameters including surface tension, surface density and surface elasticity. Both linear and nonlinear elastic foundation effect are considered on the circular curved nanobeam. The analytically Navier solution is employed to solve the governing equations. It is obviously detected that the natural frequencies of a curved nanobeams is substantially influenced by the elastic foundations. Besides, it is revealed that by increasing the thickness of curved nanobeam, the influence of surface properties and elastic foundations reduce to vanished, and the natural frequency and critical buckling load turns into to the corresponding classical values.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.3
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• pp.39-46
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• 2006

This paper presents an elastic deformation model of a spindle unit (S/U), which takes into account the non-linear properties of high-speed ball bearings (particularly the effect of high rotational speed). For this, a software for the estimation of the S/U elastic deformation properties was developed and intended for use by S/U designers. A computer aided analysis of the model using the developed software was carried out and experiments showed the significant effect of rotational speed, cutting load and bearing axial preload, and showed some new phenomena, from which the criteria for the choice of bearing axial preload is given.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.655-665
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• 2002

Two-dimensional elastic analysis of doubly periodic circular holes in an infinite plane is given in this paper. Two cases of loading, remote tension and remote shear, are considered. A rectangular cell is cut from the infinite plane. In both cases, the boundary value problem can be reduced to a complex mixed one. It is found that the eigenfunction expansion variational method is efficient to solve the problem. Based on the deformation response under certain loading, the notched medium could be modeled by an orthotropic medium without holes. Elastic properties for the equivalent orthotropic medium are investigated, and the stress concentration along the hole contour is studied. Finally, numerical examples and results are given.

• Steel and Composite Structures
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• v.16 no.1
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• pp.77-96
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• 2014

In this paper, magneto-thermo-elastic problem of a thick truncated conical shell immersed in a uniform magnetic field and subjected to internal pressure is investigated. Material properties of the shell including the elastic modulus, magnetic permeability, coefficients of thermal expansion and conduction are assumed to be isotropic and graded through the thickness obeying the simple power law distribution, while the poison's ratio is assumed to be constant. The temperature distribution is assumed to be a function of the thickness direction. Governing equations of the truncated conical shell are derived in terms of components of displacement and thermal fields and discretised with the help of differential quadrature (DQ) method. Results are obtained for different values of power law index of material properties and effects of thermal load on displacement, stress, temperature and magnetic fields are studied. Results of the present method are compared with those of the finite element method.

• Journal of the Korean Ceramic Society
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• v.35 no.5
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• pp.437-442
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• 1998

In order to investigate the mechanical properties of several fibers for reinforced cement these speciments with 2wol% of ARG and organic fibers were formed by vacuum extrusion process. After steam curing and autoclaving the flexural strength and the elastic modulus of FRC were measured. It was found that the ARG-FRC showed the elastic-brittle fracture behavior in both steam cured and autoclaved condition. And also the steam cured PP and PVA-FRC had elstic-plastic behavior but their ductility were reduced and changed to the elastic-brittle after autoclaving This change in mechanical behavior was found to be related to the thermal stablity of thes organic fibers.