• Computers and Concrete
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• v.2 no.4
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• pp.249-266
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• 2005

In the present paper a transient three-dimensional thermo-mechanical model for concrete is presented. For given boundary conditions, temperature distribution is calculated by employing a three-dimensional transient thermal finite element analysis. Thermal properties of concrete are assumed to be constant and independent of the stress-strain distribution. In the thermo-mechanical model for concrete the total strain tensor is decomposed into pure mechanical strain, free thermal strain and load induced thermal strain. The mechanical strain is calculated by using temperature dependent microplane model for concrete (O$\check{z}$bolt, et al. 2001). The dependency of the macroscopic concrete properties (Young's modulus, tensile and compressive strengths and fracture energy) on temperature is based on the available experimental database. The stress independent free thermal strain is calculated according to the proposal of Nielsen, et al. (2001). The load induced thermal strain is obtained by employing the biparabolic model, which was recently proposed by Nielsen, et al. (2004). It is assumed that the total load induced thermal strain is irrecoverable, i.e., creep component is neglected. The model is implemented into a three-dimensional FE code. The performance of headed stud anchors exposed to fire was studied. Three-dimensional transient thermal FE analysis was carried out for three embedment depths and for four thermal loading histories. The results of the analysis show that the resistance of anchors can be significantly reduced if they are exposed to fire. The largest reduction of the load capacity was obtained for anchors with relatively small embedment depths. The numerical results agree well with the available experimental evidence.

• Geomechanics and Engineering
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• v.32 no.2
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• pp.233-244
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• 2023

With the increasing amount of resources required by the society development, mining operations go deeper, which raises the requirements of studying the effects of temperature on the physical and mechanical properties of coal and adjacent rock. For now, these effects are yet to be fully revealed. In this paper, a mechanical-electromagnetic radiation (EMR) test system was established to understand the mechanical deterioration characteristics of coal by the effect of thermal treatment and its deformation and fracture characteristics under thermo-mechanical coupling conditions. The mechanical properties of high-temperature-treated coal were analyzed and recorded, based on which, reasons of coal mechanical deterioration as well as the damage parameters were obtained. Changes of the EMR time series under unconstrained conditions were further analyzed before characteristics of EMR signals under different damage conditions were obtained. The evolution process of thermal damage and deformation of coal was then analyzed through the frequency spectrum of EMR. In the end, based on the time-frequency variation characteristics of EMR, a method of determining combustion zones within the underground gasification area and combustion zones' stability level was proposed.

• Journal of Korea Foundry Society
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• v.35 no.4
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• pp.67-74
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• 2015

In this study, Mg-Zn alloys are investigated in terms of their thermal properties after an addition of Cu. Al element is added to improve the mechanical properties and castability in general case. However, it was excluded here because it significantly decreases the thermal conductivity. On the other hand, Zn was added as a major element, which had less influence on reducing the conductivity and can complement the mechanical properties as well. Cu was also added, and it improved the heat transfer characteristics as the amount was increased. The composition ranges of Zn and Cu are 6 wt.% and 0~1.5 wt.%, respectively. Mg-6Zn-xCu alloy was prepared by a gravity casting method using a steel mold and then the thermal conductivity and the microstructure of the as-cast material were investigated. By measuring the density_(${\rho}$), specific heat_(Cp) and thermal diffusivity_(${\alpha}$), the thermal conductivity_(${\lambda}$) was calculated by the equation ${\lambda}={\rho}{\cdot}Cp{\cdot}{\alpha}$. As the amount of Cu increased in the Mg-6Zn-xCu alloy, the heat transfer characteristics were improved, resulting in a synergistic effect which is slow when the added Cu exceeds 1 wt.%. In order to investigate the relative thermal conductivity/emission of the Mg-6Zn-xCu alloy, AZ91 and AZ31 were experimentally evaluated and compared using a separate test equipment. As a result, the Mg-6Zn-1.5Cu alloy when compared to AZ91 showed improvements in the thermal conductivity ranging from 30 to 60% with a nearly 20% improvement in the thermal emission.

• Composites Research
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• v.17 no.6
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• pp.44-51
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• 2004

To determine the effect of numbers of nitrogen atom bonded at ethyl group included in main chain of linear amine curing agents of epoxy-cure systems on the thermal and mechanical properties, standard epoxy resin DGEBF was cured with DETA, TETA and TEPA in a stoichiometrically equivalent ratio. From this work, the effect of curing agents of the DGEBF/amine systems oil the thermal and mechanical properties was significantly influenced by numbers of nitrogen atom of curing agents. The results showed that heat of reaction increased, and maximum exothermic temperature decreased with the decrease of numbers of nitrogen atom. In case of cured systems, density and maximum conversion(%) had no relation to numbers of nitrogen atom, but flexural modulus and tensile modulus increased with the decrease of numbers of nitrogen atom in main chain. Thermal stability, shrinkage(%), Tg, tensile and flexural strength showed irregular tendency having nothing to do with numbers of nitrogem atom at a sight. This findings imply that the differences in the maximum conversion(%) about the chain length of curing agents affect the thermal and mechanical properties.

• Composites Research
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• v.29 no.5
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• pp.276-281
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• 2016

Improvement of the thermal and adhesion properties of stone/wood composites was studied. Tensile test was performed for wood and stone to know the basic mechanical properties. Real-time temperature of stone and wood was measured when stone and wood was heated. To compare thermal transfer properties of stone/wood composites, two types of specimens were tested: one was stone upper whereas another was wood upper. Real time temperature measurement and lap shear test were performed to know thermal and adhesion properties by using CNT-epoxy adhesive in which CNT was dispersed in epoxy adhesive uniformly. The thermal transfer property was better for the wood upper case than stone upper case. Adding CNT improved the heat transfer as well as mechanical properties including lap shear strength.

• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.251-258
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• 2000

Thermal deformation in an electronic package due to thermal strain mismatch is investigated. The warpage and the in-plane deformation of the package after encapsulation is analyzed using the laminated plate theory. An exact solution for the thermal deformation of an electronic package with circular shape is derived. Theoretical results are presented on the effects of the layer geometries and material properties on the thermal deformation. Several applications of the exact solution to electronic packaging product development are illustrated. The applications include lead on chip package, encapsulated chip on board and chip on substrate.

• Archives of Metallurgy and Materials
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• v.65 no.3
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• pp.1029-1033
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• 2020

In this study, we investigated the effect of Fe addition (0, 0.25, 0.50 and 0.75 wt.%) on the microstructure, mechanical properties and electrical conductivity of as-cast and as-extruded Al-RE alloys. As the Fe element increased by 0 and 0.75wt.%, the phase fraction increased to 5.05, 5.76, 7.14 and 7.38 %. The increased intermetallic compound increased the driving force for recrystallization and grain refinement. The electrical conductivity of Al-1.0 wt.%RE alloy with Fe addition decreased to 60.29, 60.15, 59.58 and 59.13 %IACS. With an increase in the Fe content from 0 to 0.75 wt.% the ultimate tensile strength (UTS) of the alloy increased from 74.3 to 77.5 MPa. As the mechanical properties increase compared to the reduction of the electrical conductivity due to Fe element addition, it is considered to be suitable for fields requiring high electrical conductivity and strength.

• Smart Structures and Systems
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• v.9 no.5
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• pp.427-439
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• 2012

The present paper deals with the analytical solution of a functionally graded piezoelectric (FGP) cylinder in the magnetic field under mechanical, thermal and electrical loads. All mechanical, thermal and electrical properties except Poisson ratio can be varied continuously and gradually along the thickness direction of the cylinder based on a power function. The cylinder is assumed to be axisymmetric. Steady state heat transfer equation is solved by considering the appropriate boundary conditions. Using Maxwell electro dynamic equation and assumed magnetic field along the axis of the cylinder, Lorentz's force due to magnetic field is evaluated for non homogenous state. This force can be employed as a body force in the equilibrium equation. Equilibrium and Maxwell equations are two fundamental equations for analysis of the problem. Comprehensive solution of Maxwell equation is considered in the present paper for general states of non homogeneity. Solution of governing equations may be obtained using solution of the characteristic equation of the system. Achieved results indicate that with increasing the non homogenous index, different mechanical and electrical components present different behaviors along the thickness direction. FGP can control the distribution of the mechanical and electrical components in various structures with good precision. For intelligent properties of functionally graded piezoelectric materials, these materials can be used as an actuator, sensor or a component of piezo motor in electromechanical systems.

• Composites Research
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• v.18 no.4
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• pp.14-20
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• 2005

To determine the effect of chemical structure of aromatic amino curing agents on thermal and mechanical properties, standard epoxy resin DGEBF (diglycidylether of bisphenol F) was cured with diaminodiphenyl methane (DDM) and diaminodiphenyl sulphone (DDS) in a stoichiometrically equivalent ratio. From this work the effect of aromatic amino curing agents on the thermal and mechanical properties is significantly influenced by the chemical structure of curing agents. In contrast, the results show that the DGEBF/DDS system having the sulfone structure between the benzene rings had higher values in the thermal stability, density, shrinkage ($\%$), thermal expansion coefficient, tensile modulus and strength, flexural modulus and strength than the DGEBF/DDM system having methylene structure between the benzene rings, whereas the DGEBF/DDS system presented low values in maximum exothermic temperature, conversion of epoxide, and grass transition temperature. These results are caused by the relative effects of sulfone group having strong electronegativity and methylene group having (+) repulsive property. The result of fractography shows that the grain distribution of DGEBF/DDS system is more irregular than that of the DGEBF/DDM system.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.2
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• pp.85-90
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• 2021

The gamma irradiation was on to Poly(butylene sebacate-co-terephthalate) (PBSeT), Poly(butylene adipate-co-terephthalate) (PBAT), Poly(lactic acid) (PLA) and casting polypropylene (CPP) at dose levels from 0 to 50 kGy. The properties of gamma irradiated samples were analyzed using DSC, TGA, UTM and FT-IR spectra. The mechanical and thermal properties of PBSeT and PBAT after gamma irradiation were less affected than CPP. The tensile strength and elongation of PBSeT was not affected by gamma irradiation, while these of PBAT, PLA and CPP were significantly decreased at 50 kGy gamma-ray dose. The thermal stability of PBSeT, PBAT, PLA and CPP showed a similar tendency to tensile strength. The glass transition temperature(T_g) and melting temperature(T_m) of PBSeT and PBAT were not altered by increasing gamma-ray dose, while these of PLA and CPP decreased. The chemical composition of all samples was not modified by gamma irradiation, and it was confirmed by FT-IR spectra. Based on mechanical and thermal stability studies of gamma irradiation on bioplastics, tested biodegradable packaging materials showed a potential to be used in sterilization process up to 35 kGy.