• Steel and Composite Structures
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• v.19 no.6
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• pp.1333-1354
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• 2015

A higher order analytical solution for static analysis of a truncated conical composite sandwich panel subjected to different loading conditions was presented in this paper which was based on a new improved higher order sandwich panel theory. Bending analysis of sandwich structures with flexible cores subjected to concentrated load, uniform distributed load on a patch, harmonic and uniform distributed loads on the top and/or bottom face sheet of the sandwich structure was also investigated. For the first time, bending analysis of truncated conical composite sandwich panels with flexible cores was performed. The governing equations were derived by principle of minimum potential energy. The first order shear deformation theory was used for the composite face sheets and for the core while assuming a polynomial description of the displacement fields. Also, the in-plane hoop stresses of the core were considered. In order to assure accuracy of the present formulations, convergence of the results was examined. Effects of types of boundary conditions, types of applied loads, conical angles and fiber angles on bending analysis of truncated conical composite sandwich panels were studied. As, there is no research on higher order bending analysis of conical sandwich panels with flexible cores, the results were validated by ABAQUS FE code. The present approach can be linked with the standard optimization programs and it can be used in the iteration process of the structural optimization. The proposed approach facilitates investigation of the effect of physical and geometrical parameters on the bending response of sandwich composite structures.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.222-227
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• 2007

The adsorption features of fluoride ion on the oyster shell have been investigated for the purpose of the employment of waste oyster shell as an adsorbent for the treatment of fluoride ion-containing wastewater. The major component of oyster shell was examined to be Ca with minor components of Na, Si, Mg, Al, and Fe. As the initial concentration of fluoride ion was raised, its absorbed amount was enhanced at equilibrium, however, the adsorption ratio of fluoride ion compared with its initial concentration was shown to be decreased. Also, adsorption of fluoride ion onto the oyster shell resulted in the formation of $CaF_2$ in the morphological structure of adsorbent. Kinetic analysis showed that the adsorption reaction of fluoride ion generally followed a second order reaction with decreasing rate constant with the initial concentration of adsorbate. Freundlich model agreed well with the adsorption behavior of fluoride ion at equilibrium and the adsorption reaction of fluoride ion was examined to be endothermic. Several thermodynamic parameters for the adsorption reaction were calculated based on thermodynamic equations and the activation energy for the adsorption of fluoride ion onto oyster shell was estimated to be ca. 13.589 kJ/mole.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.96-96
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• 2009

The purpose of this study is to clarify the transitional behavior and main factor of excessive welding distortion caused by fabrication process of STS 304 vacuum vessel having double curvature for the efficient quality control of vacuum vessel. In order to do it, the predictive equations of the welding distortion in simple weldment of vacuum vessel were established by conventional finite element analysis. And the principal factor controlling the welding distortion was identified by evaluating the welding distortion of vacuum vessel in each fabrication process with FEA and simplified thermo elastic method. Based on the results, the principal factors of distortion of vacuum vessel were clarified as angular distortion and transverse shrinkage which are a source of excessive out-of plane distortion in the double curved vacuum vessel. It was expected that the FE analysis results of this study could contribute to establish the proper control method of welding distortion for double curved vacuum vessel.

• Computers and Concrete
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• v.33 no.2
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• pp.205-216
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• 2024

Self-Curing Self Compacting Concrete (SCSCC), is a special concrete in contemporary construction practice aimed at enhancing the performance of structural concrete. Its primary function is to ensure a sufficient moisture supply that facilitates hydration along with flow, particularly in the context of high-rise buildings and tall structures. This innovative concrete addresses the challenges of maintaining adequate curing conditions in large-scale projects, maintaining requisite workability, contributing to the overall durability and longevity of concrete structures. For implementing such a versatile material in construction, it is imperative to understand the stress-strain (S-S) behaviour. The primary aim of this study is to develop the S-S curves for TCSCSCC and compare through experimental results. Finite element (FE) analysis based ATENA-GiD was employed for the numerical simulation and develop the analytical stress-strain curves by introducing parameters viz., grade of concrete, tie diameter, tie spacing and yield strength. The stress ratio and the strain ratios are evaluated and compared with experimental values. The mean error is 1.2% with respect to stresses and 2.2% in case of strain. Finally, the stress block parameters for tie confined SCSCC are evaluated and equations are proposed for the same in terms of confinement index.

• Advances in nano research
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• v.16 no.4
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• pp.325-340
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• 2024

There are several novel uses for dispersing many nanoparticles into a conventional fluid, including dynamic sealing, damping, heat dissipation, microfluidics, and more. Therefore, melting heat and mass transfer characteristics of a 3-D MHD Hybrid Nanofluid flow over a rotating disc with presenting dufour and soret effects are assessed numerically in this study. In this instance, we investigated both ferric sulfate and molybdenum disulfide as nanoparticles suspended within base fluid water. The governing partial differential equations are transformed into linked higher-order non-linear ordinary differential equations by the local similarity transformation. The collection of these deduced equations is then resolved using a Chebyshev spectral collocation-based algorithm built into the Mathematica software. To demonstrate how different instances of hybrid/ nanofluid are impacted by changes in temperature, velocity, and the distribution of nanoparticle concentration, examples of graphical and numerical data are given. For many values of the material parameters, the computational findings are shown. Simulations conducted for different physical parameters in the model show that adding hybrid nanoparticle to the fluid mixture increases heat transfer in comparison to simple nanofluids. It has been identified that hybrid nanoparticles, as opposed to single-type nanoparticles, need to be taken into consideration to create an effective thermal system. Furthermore, porosity lowers the velocities of simple and hybrid nanofluids in both cases. Additionally, results show that the drag force from skin friction causes the nanoparticle fluid to travel more slowly than the hybrid nanoparticle fluid. The findings also demonstrate that suction factors like magnetic and porosity parameters, as well as nanoparticles, raise the skin friction coefficient. Furthermore, It indicates that the outcomes from different flow scenarios correlate and are in strong agreement with the findings from the published literature. Bar chart depictions are altered by changes in flow rates. Moreover, the results confirm doctors' views to prescribe hybrid nanoparticle and particle nanoparticle contents for achalasia patients and also those who suffer from esophageal stricture and tumors. The results of this study can also be applied to the energy generated by the melting disc surface, which has a variety of industrial uses. These include, but are not limited to, the preparation of semiconductor materials, the solidification of magma, the melting of permafrost, and the refreezing of frozen land.

• Applied Chemistry for Engineering
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• v.34 no.4
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• pp.412-420
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• 2023

In this study, red mud/fly ash based geopolymer adsorbents (RFGPA) were prepared with calcination temperatures of 200, 400, and 600 ℃, and the effects of these calcination temperatures on the adsorption of methylene blue (MB) were investigated. In addition, the prepared RFGPA was characterized using X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) spectroscopy, and Brunauer-EmmettTeller (BET) analysis. The results of the adsorption kinetics of MB at RFGPA prepared calcination temperatures indicated that the adsorption equilibrium of MB was reached after about 72 h. From the results of the adsorption isotherm, we verified that the degree of adsorption increased with increasing MB concentrations. In addition, the adsorption amount (Q) of MB decreased with an increase in calcination temperature. The experimental adsorption isotherm data were well fitted to the Freundlich and Sips equations compared to the Langmuir equation. In order to verify the effects of photocatalytic decomposition (C/C₀) of MB on Fe₂O₃ present in prepared RFGPA, the degree of decomposition of MB was examined under dark and visible conditions. Results indicated that the decomposition of MB in visible conditions was about 3.0 times faster than that in dark conditions.

• Structural Monitoring and Maintenance
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• v.5 no.1
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• pp.151-171
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• 2018

Transmission tower-line systems are commonly slender and generally possess a small stiffness and low structural damping. They are prone to impulsive excitations induced by cable rupture and may experience strong vibration. Excessive deformation and vibration of a transmission tower-line system subjected to cable rupture may induce a local destruction and even failure event. A little work has yet been carried out to evaluate the performance of transmission tower-line systems in mountain areas subjected to cable rupture. In addition, the control for cable rupture induced vibration of a transmission tower-line system has not been systematically conducted. In this regard, the dynamic response analysis of a transmission tower-line system in mountain areas subjected to cable rupture is conducted. Furthermore, the feasibility of using viscous fluid dampers to suppress the cable rupture-induced vibration is also investigated. The three dimensional (3D) finite element (FE) model of a transmission tower-line system is first established and the mathematical model of a mountain is developed to describe the equivalent scale and configuration of a mountain. The model of a tower-line-mountain system is developed by taking a real transmission tower-line system constructed in China as an example. The mechanical model for the dynamic interaction between the ground and transmission lines is proposed and the mechanical model of a viscous fluid damper is also presented. The equations of motion of the transmission tower-line system subjected to cable rupture without/with viscous fluid dampers are established. The field measurement is carried out to verify the analytical FE model and determine the damping ratios of the example transmission tower-line system. The dynamic analysis of the tower-line system is carried out to investigate structural performance under cable rupture and the validity of the proposed control approach based on viscous fluid dampers is examined. The made observations demonstrate that cable rupture may induce strong structural vibration and the implementation of viscous fluid dampers with optimal parameters can effectively suppress structural responses.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.1-11
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• 2011

The typical truss-lattice material successively packed by repeated cubic symmetric unit cells consists of sub-elements (SE) proposed in this study. The representative continuum model for this truss-lattice material such as the effective strain and stress relationship can be formulated by the homogenization procedure based on the notation of averaged mechanical properties. The volume fractions of micro-scale struts have a significant influence on the effective strength as well as the relative density in the lattice plate with replicable unit cell structures. Most of the strength contribution in the lattice material is induced by axial stiffness under uniform stretching or compression responses. Therefore, continuum based constitutive models composed of homogenized member stiffness include these mechanical characteristics with respect to strength, internal stress state, material density based on the volume fraction and even failure modes. It can be also recognized that the stress state of micro-scale struts is directly associated with the continuum constitutive model. The plastic flow at the micro-scale stress can extend the envelope of the analytical stress function on the surface of macro-scale stress derived from homogenized constitutive equations. The main focus of this study is to investigate the basic topology of unit cell structures with the cubic symmetric system and to formulate the plastic models to predict pressure dependent macro-scale stress surface functions.