• Steel and Composite Structures
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• 제46권5호
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• pp.649-658
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• 2023

Although some scholars have studied the thermal post-buckling of graphene platelets strengthened metal foams (GPLRMFs) plates, they have not considered the influence of initial geometrical imperfection. Inspired by this fact, the present paper studies the thermal post-buckling characteristics of GPLRMFs plates with initial geometrical imperfection. Three kinds of graphene platelets (GPLs) distribution patterns including three patterns have been considered. The governing equations are derived according to the first-order plate theory and solved with the help of the Galerkin method. According to the comparison with published paper, the accuracy and correctness of the present research are verified. In the end, the effects of material properties and initial geometrical imperfection on the thermal post-buckling response of the GPLRMFs plates are examined. It can be found that the presence of initial geometrical imperfection reduces the thermal post-buckling strength. In addition, the present study indicates that GPL-A pattern is best way to improve thermal post-buckling strength for GPLRMFs plates, and the presence of foams can improve the thermal post-buckling strength of GPLRMFs plates, the Foam- II and Foam- I patterns have the lowest and highest thermal post-buckling strength. Our research can provide guidance for the thermal stability analysis of GPLRMFs plates.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.731-737
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• 2018

In this research paper, the thermal transport in thorium dioxide is investigated by using nonequilibrium molecular dynamics. The thermal conductivity of bulk thorium dioxide was measured to be 20.8 W/m-K, confirming reported values, and the phonon mean free path was estimated to be between 7 and 8.5 nm at 300 K. It was observed that the thermal conductivity of thorium dioxide shows a strong dependency on temperature; the highest thermal conductivity was estimated to be 77.3 W/m-K at 100 K, and the lowest thermal conductivity was estimated to be 4.3 W/m-K at 1200 K. In addition, by simulating thorium dioxide structures with different lengths at different temperatures, it was identified that short wavelength phonons dominate thermal transport in thorium dioxide at high temperatures, resulting in decreased intrinsic phonon mean free paths and minimal effect of boundary scattering while long wavelength phonons dominate the thermal transport in thorium dioxide at low temperatures.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1909-1923
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• 2021

We experimentally investigated the effects of thermal aging and cold work on the microstructure, mechanical properties, and primary water stress corrosion cracking (PWSCC) initiation time for Alloy 182 welds. The effects of thermal aging and cold work on the PWSCC initiation time of Alloy 182 were modeled based on the plastic energy concept and the PWSCC initiation data of this study and previous reports by considering censored data. Based on the results, it is estimated that the PWSCC resistance of the Alloy 182 weld firstly increases and then decreases with thermal aging time when the applied stress is kept constant.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.823-830
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• 2001

The single fiber pull-out technique has been commonly used to characterize the mechanical behavior of fiber/matrix interface in fiber reinforced composite materials. In this study, an improved analysis considering the effect of thermal residual stresses in both radial and axial directions is developed for the single fiber pull-out test. It is found to have the pronounced effects on the stress transfer properties across the interface and the interfacial debonding behavior.

• Journal of Mechanical Science and Technology
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• 제19권4호
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• pp.958-967
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• 2005

The mathematical model for tension behaviors of a moving web by Shin (2000) is extended to the tension model considering the thermal strain due to temperature variation in furnace. The extended model includes the terms that take into account the effect of the change of the Young's Modulus, the thermal coefficient, and the thermal strain on the variation of strip tension. Computer simulation study proved that the extended tension model could be used to analyze tension behaviors even when the strip goes through temperature variation. By using the extended tension model, a new tension control method is suggested in this paper. The key factors of suggested tension control method include that the thermal strain of strip could be compensated by using the velocity adjustment of the helper-rollers. The computer simulation was carried out to confirm the performance of the suggested tension control method. Simulation results show that the suggested tension control logic not only overcomes the problem of the traditional tension control logic, but also improves the performance of tension control in a furnace of the CAL (Continuous Annealing Line).

• Journal of Mechanical Science and Technology
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• 제14권2호
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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.

• Journal of Mechanical Science and Technology
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• 제19권10호
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• pp.1932-1938
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• 2005

Graphite foams consist of a network of interconnected graphite ligaments and are beginning to be applied to thermal management of electronics. The thermal conductivity of the bulk graphite foam is similar to aluminum, but graphite foam has one-fifth the density of aluminum. This combination of high thermal conductivity and low density results in a specific thermal conductivity about five times higher than that of aluminum, allowing heat to rapidly propagate into the foam. This heat is spread out over the very large surface area within the foam, enabling large amounts of energy to be transferred with relatively low temperature difference. For the purpose of graphite foam thermosyphon design in electronics cooling, various effects such as graphite foam geometry, sub-cooling, working fluid effect, and liquid level were investigated in this study. The best thermal performance was achieved with the large graphite foam, working fluid with the lowest boiling point, a liquid level with the exact height of the graphite foam, and at the lowest sub-cooling temperature.

• 폴리머
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• 제39권2호
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• pp.200-209
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• 2015

In this study, the influence of dilauroyl peroxide on mechanical and thermal properties of different polypropylene (PP) matrices was investigated. Polypropylene matrices, different molecular weight isotactic PP containing 0.01, 0.02, 0.04, 0.06, 0.08, and 0.1 wt% of dilauroyl peroxide (DLP) were prepared by using a single-screw extruder. The effect of the visbreaking agent (DLP) on mechanical, physical, thermal and morphological properties of different molecular weight PP had been studied. Mechanical properties (tensile strength at break point, at yield and elongation at break point), melt flow index (MFI), scanning electron microscope (SEM) and differential scanning calorimetric (DSC) analyses of these matrices were examined. Melting ($T_m$) and crystallization ($T_c$) temperatures, crystallinity ratio (%) and enthalpies were determined. The microstructure of isotactic polypropylene matrix was investigated by scanning electron microscopy (SEM). From SEM analysis, it was observed that the surface disorder increased by the increasing amount of DLP. As a result of DSC analyses, the crystallinity ratio of the PP matrices has varied between 1.64-7.27%. Mechanical properties of the matrices have been improved. Particularly, the mechanical tests of PP have given interesting results when compounded with 0.06-0.08 wt% dilauroyl peroxide (DLP). Mechanical properties and thermal decomposition processes were all changed by increasing the amount of DLP in the matrix structure.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.64-71
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• 2005

The welding methods have been applied to the most structural products used in the automobile, ship construction, and construction. The structure steel must have sufficient strength of structure; However, the mechanical properties of the welded part changes when it is welded. Therefore, the stability or life of the structure may be affected by the changed mechanical properties. The mechanical properties of the welded part must be examined in order to ensure the safety of structure. In this research, the SS400 steel and the STS304 steel were used to estimate the mechanical properties of the HAZ by weld thermal cycle simulation. In this study, the materials were used to examine the weld thermal cycle simulation characteristic, under two conditions: the drawing with diameter of $\Phi$10 and the residual stress removal treatment. To examine the mechanical properties by the weld thermal cycle simulation, the tensile test was carried out in room temperature. The crosshead speed was lmm/min.

• 비파괴검사학회지
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• 제34권1호
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• pp.10-17
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• 2014

A 3D model based on the finite element method (FEM) was built to simulate the infrared thermography (IRT) inspection process. Thermal contrast is an important parameter in IRT and was proven to be a function of defect parameters. Parametric studies were conducted on internal defects with different depths, thicknesses, and orientations. Thermal contrast evolution profiles with respect to the time of the defect and host material were obtained through numerical simulation. The thermal contrast decreased with defect depth and slightly increased with defect thickness. Different orientations of thin defects were detected with IRT, but doing so for thick defects was difficult. These thermal contrast variations with the defect depth, thickness, and orientation can help in optimizing the experimental process and interpretation of data from IRT.