• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.20-23
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• 2010

In this study, the electromechanical property of REBCO coated conductor (CC) tape adopting a stainless steel substrate has been investigated. Sample was subjected to uniaxial tension and measured its mechanical properties at RT and 77 K. $I_c-{\varepsilon}_t$ relations was also studied in which the strain and stress corresponding to the 95% $I_c$ retention and reversible strain limit were measured. In addition, these results were compared to the case of conventional REBCO CC tape adopting a Hastelloy substrate. As a result, by adopting a stainless steel substrate comparable strength and good electromechanical property to Hastelloy one could be achieved.

• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.59-69
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• 2017

The field of fracture mechanics has gained significance because of its ability to address the behaviour of cracks. Predicting the fracture properties of concrete based on experimental investigations is a challenge considering the quasi-brittle nature of concrete. So, there is a need for developing a standard numerical tool which predicts the fracture energy of concrete which is at par with experimental results. The present study is an attempt to evaluate the fracture energy and characteristic length for different grades of concrete using Concrete Damage Plasticity (CDP) model. Indian Standard and EUROCODE are used for the basic input parameters of concrete. Numerical evaluation is done using Finite Element Analysis Software ABAQUS/CAE. Hsu & Hsu and Saenz stress-strain models are adopted for the current study. Mesh sensitivity analysis is also carried to study the influence of type and size of elements on the overall accuracy of the solution. Different input parameters like dilatation angle, eccentricity are varied and their effect on fracture properties is addressed. The results indicated that the fracture properties of concrete for various grades can be accurately predicted without laboratory tests using CDP model.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.365-375
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• 2010

Concrete-filled steel tube columns are expected to have confined effects of the steel on the concrete and reinforced local buckling effects of the concrete. After comparing the results of existing studies with the experimental results from this study, the stress-strain relations were modified by evaluating the load-displacement with consideration of the confined effects. The effects of the parameters on the load-displacement and moment-curvature relationship according to the sectional and material properties were analyzed.

• Steel and Composite Structures
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• v.28 no.3
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• pp.331-347
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• 2018

In this paper history of stresses, strains, radial and circumferential displacements of a functionally graded thick-walled hollow cylinder due to creep phenomenon is investigated. The cylinder is subjected to an arbitrary non-axisymmetric two dimensional thermo-mechanical loading and uniform magnetic field along axial direction. Using equilibrium, strain-displacements and stress-strain relations, the governing differential equations of the problem containing creep strains are derived in terms of radial and circumferential displacements. Since the displacements are varying with time due to creep phenomenon, an analytical solution is not available for these equations. Thus, a semi-analytical procedure based on separation of variables and Fourier series together with a numerical procedure is employed. The numerical results indicate that the non-axisymmetric loading and the material grading index have significant effect on stress redistributions. Moreover, by proper selection of material for any combination of non-axisymmetric loading, one can arrive suitable response for the cylinder to achieve optimal design. With some simplifications, the results are validated with the existing literature.

• Smart Structures and Systems
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• v.30 no.3
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• pp.245-253
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• 2022

A two-layer beam consisting of an elastoplastic layer and a functional layer made of shape memory alloy (SMA) TiNi is considered. Constitutive relations for SMA are set by a microstructural model capable to calculate strain increment produced by arbitrary increments of stress and temperature. This model exploits the approximation of small strains. The equations to calculate the variations of the strain and the internal variables are based on the experimentally registered temperature kinetics of the martensitic transformations with an account of the crystallographic features of the transformation and the laws of equilibrium thermodynamics. Stress and phase distributions over the beam height are calculated by steps, by solving on each step the boundary-value problem for given increments of the bending moment (or curvature) and the tensile force (or relative elongation). Simplifying Bernoulli's hypotheses are applied. The temperature is considered homogeneous. The first stage of the numerical experiment is modeling of preliminary deformation of the beam by bending or stretching at a temperature corresponding to the martensitic state of the SMA layer. The second stage simulates heating and subsequent cooling across the temperature interval of the martensitic transformation. The curvature variation depends both on the total thickness of the beam and on the ratio of the layer's thicknesses.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.767-772
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• 2009

Laser shock peening(LSP) is proving to be better surface treatment than conventional one such as shot peening. The LSP process has a compressive residual stress into a metal alloy and a significant improvement in fatigue life. Our research is focused on applying finite element method to the prediction of residual stress through the LSP processing in some LSP conditions such as pressure and spot size induced by laser. Two analysis methods are considered to calculating the compressive residual stress. But the explicit solution and the static one after partially explicit solving are almost same. In LSP, because of very high strain rate($10^6s^{-1}$), HEL(Hugoniot Elastic Limit) is the most important parameter in material behavior modeling. As the circular laser spot is considered, 2-D axisymmetric elements are used and the infinite elements are applied to boundaries for no reflection. The relations of material properties and the LSP are also important parts in this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.570-573
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• 2006

It is proposed that the electromechanical relation of the conductive materials with high electrical resistance may be used to estimate the current stress of prestressing tendons. To choose the best conductive material to this end, we studied the electromechanical relations of carbon fibers and metalic heat wires experimentally. It is found that the relation of carbon fibers can be modelled by a parabolic(or hyperbolic) function in the early stage of deformation. Metallic heat wires show a consistent linear relation during loading and unloading in the elastic deformation and are suitable for this purpose. We propose a new kind of prestressing tendons whose stress can be monitored.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.692-697
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• 2001

It is necessary to analyze the mechanical behaviors of the power steering hose, which must play a proper role under severe operating conditions, in order to prepare a preventive measure fur contrary effects expected in unfavorable circumstances. In this paper, the stress and deformation characteristics of the hose components such as rubber, sleeve, nipple and reinforced braids during the swaging process, are analyzed using the finite element method. Contact conditions identical to the manufacturing process are taken into account, and the material properties based on experimental data are used in the analysis. Investigations into the mutual relations between the manufacturing conditions and the hose performances are done with respect to the jaw stroke on the basis of the stress and strain values of the hose components after swaging process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1521-1528
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• 2011

We studied the material properties for reliability improvement in finite element analysis results for a nitrile butadiene rubber hub-bearing seal and for a carbon-filled rubber mount used in a vehicle. It was difficult to measure the material properties of hundreds of types of rubber for the mount design. Thus, we suggested that the engineering stressstrain relations from pure shear test data could be synthesized by using simple tension data and Poisson's ratio. We defined Poisson's ratio by using a function of principal stretches to synthesize the stress-strain relations for a pure shear test. A transformation of the pure shear data was applied to the experimental values to obtain the predicted results when the strain approaches 100%. In the finite element analysis for the contact force of a hub-bearing seal, the strain results that used the transformation of the pure shear data and simple tension data almost corresponded to the experimental values. Ogden constants were used to analyze.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.31-42
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• 2015

The plastic stress distribution method and the strain compatibility method are the two representative methods to calculate the P-M interaction strength of RCFT (rectangular concrete filled tube) columns. The plastic stress distribution method is approximate while the stress compatibility method should approach the exact solution if accurate constitutive relations of the materials involved are used. Recent study by the authors pointed out that, because of lack of accurate constitutive model for the concrete confined by the rectangular steel tube, no strain compatibility method according to the current structural provisions provides a satisfactory prediction of the P-M interaction strength of RCFT columns under various material combinations. An empirical constitutive model which can capture the stress-strain characteristics of the confined concrete of RCFT columns is proposed based on analyzing extensive exisitng test database. The key idea was to define the concrete crushing strain as a function of steel-to-concrete strength ratio and width-to-thickness ratio of steel tube. It was shown that the proposed model leads to more accurate and more consistent prediction of the P-M interaction strength of RCFT columns under general design conditions.