• Journal of Power System Engineering
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• v.18 no.3
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• pp.100-105
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• 2014

This study is to investigate the effect of thermo mechanical treatment on the mechanical properties of 316L stainless steel. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite was formed by deformation. With increasing number of thermo mechanical treatment, volume fraction of martensite was increased rapidly, and then unchanged. With increasing number of thermo mechanical treatment, hardness and strength was increased rapidly, and then unchanged while elongation was decreased rapidly, and then unchanged. With increasing volume fraction of martensite formed by thermo mechanical treatment, hardness and strength was increased rapidly, elongation was decreased rapidly. Thus, hardness, strength and elongation of thermo mechanical treated 316L stainless steel was strongly affected by martensite formed by thermo mechanical treatment. Good combination of strength and elongation was obtained from thermomechanical treatment.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.2
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• pp.61-67
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• 2019

This study was carried out to investigate the effect of thermo-mechanical treatment on the tensile properties of Fe-20Mn-12Cr-3Ni-3Si alloy with deformation induced martensite transformation. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite, dislocation, stacking fault were formed, and grain size was refined by thermo-mechanical treatment. With the increasing cycle number of thermo-mechanical treatment, volume fraction of ${\varepsilon}$ and ${\alpha}^{\prime}$-martensite, dislocation, stacking fault were increased, and grain size decreased. In 5-cycle number thermo-mechanical treated specimens, more than 10% of the volume fraction of ${\varepsilon}$-martensite and less than 3% of the volume fraction of ${\alpha}^{\prime}$-martensite were attained. Tensile strength was increased and elongation was decreased with the increasing cycle number of thermo-mechanical treatment. Tensile properties of thermo-mechanical treated alloy with deformation induced martensite transformation was affected to formation of martensite by thermo-mechanical treatment, but was large affected to increasing of dislocation and grain refining.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.6
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• pp.271-278
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• 2017

This study was carried out to investigate the relationship between the mechanical properties and damping capacity of thermo-mechanical treated 316L stainless steel. Dislocations, ${\varepsilon}$ and ${\alpha}^{\prime}$-martensites were formed by thermo-mechanical treatment, and the grain size was changed from micrometer to sub-micrometer by 5-cycled thermo-mechanical treatment. The volume fraction of dislocations, ${\varepsilon}$ and ${\alpha}^{\prime}$-martensites was increased, and grain size of austenite increased and lengthened by the with increasing cycle number of thermo-mechanical treatment. In 5-cycled specimens, the volume fraction of ${\alpha}^{\prime}$-martensite was more than 25% and the less than 5% of volume fraction of ${\varepsilon}$-martensite was attained. With increasing number of thermo-mechanical treatment, hardness, strength and damping capacity were increased, but elongation was decreased. Damping capacity was increased with increased hardness and strength, but decreased with increased elongation, and this result was the opposite tendency for general metal.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2099-2106
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• 2003

In this paper, a novel fast response NDIR analyzer (FRNDIR), which uses an electrically pulsed semiconductor emitter and dual type PbSe detector for the PPM-level detection of carbon dioxide (CO$_2$) at a wavelength of 4.28 $\mu\textrm{m}$, is described. Modulation of conventional NDIR energy typically occurs at 1 to 20 Hz. To achieve real time high-speed measurement, the new analyzer employs a semiconductor light emitter that can be modulated by electrical chopping. Updated measurements are obtained every one millisecond. The detector has two independent lead selenide (PbSe) with IR band pass filters. Both the emitter accuracy and the detector sensitivity are increased by thermoelectric cooling of up to -20 degrees C in all semiconductor devices. Here we report the use of semiconductor devices to achieve improved performance such that these devices have potential application to CO$_2$ gas measurement and, in particular, the measurement of fast response CO$_2$ concentration at millisecond level.

• Composites Research
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• v.33 no.4
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• pp.198-204
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• 2020

In this study, we employ the full atomistic molecular dynamics simulation and finite element homogenization method to predict the thermo-mechanical properties of nanocomposites including carbon nanotube bundle. As the number of carbon nanotubes within the single bundle increases, the effective in-plane Young's modulus and in-plane shear modulus decrease, and in-plane thermal expansion coefficient increases, despite the same volume fraction of carbon nanotubes. To investigate the thickness of interphase zone, we employ the radial density distribution. It is investigated that the interphase thickness is almost independent on the number of carbon nanotubes within the single bundle. It is assumed that the matrix and interphase are isotropic materials. According to the predicted thermo-mechanical properties of interphase zone, the Young's modulus and shear modulus of interphase zone clearly decrease, and the thermal expansion coefficient increases. Based on the thermo-mechanical interphase behavior, we developed the multiscale homogenization model to predict the thermo-mechanical properties of PLA nanocomposites that include the carbon nanotube bundle.

• Advances in materials Research
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• v.6 no.1
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• pp.27-43
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• 2017

The transient thermo-mechanical behavior of a simply-supported beam made of a functionally graded material (FGM) under the effect of a moving heat source is investigated. The FGM consists of a ceramic part (on the top), which is the hot side of the beam as the heat source motion takes place along this side, and a metal part (in the bottom), which is considered the cold side. Grading is in the transverse direction, with the properties being temperature-dependent. The main steps of the thermo-elastic modeling included deriving the partial differential equations for the temperatures and deflections in time and space, transforming them into ordinary differential equations using Laplace transformation, and finally using the inverse Laplace transformation to find the solutions. The effects of different parameters on the thermo-mechanical behavior of the beam are investigated, such as the convection coefficient and the heat source intensity and speed. The results show that temperatures, and hence the deflections and stresses increase with less heat convection from the beam surface, higher heat source intensity and low speeds.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1061-1064
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• 2006

Optimal design of functionally graded plates is investigated considering stress and critical temperature. Material properties are assumed to be temperature dependent and varied continuously in the thickness direction. The effective material properties are obtained by applying linear rule of mixtures. The 3-D finite element model is adopted using an 18-node solid element to analyze more accurately the variation of material properties and temperature field in the thickness direction. For stress analysis, the tensile stress ratio and compressive stress ratio of the structure under mechanical load are investigated. In the thermo-mechanical buckling analysis, temperature at each node is obtained by solving the steady-state heat transfer problem and Newton-Raphson method is used for material nonlinear analysis. Finally, the optimal design of FGM plates is studied for stress reduction and improving thermo-mechanical buckling behavior, simultaneously.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.2
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• pp.106-111
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• 2007

In this research work attempts were made to study the bonding of thermo-plastics with adhesives using solar radiation. In order to study the curing behaviour necessary experiments were conducted under varying conditions of temperature, exposure time and power of solar energy. The cured samples were then studied under the optical microscope before subjecting to tensile testing in order to study their mechanical properties of thermo-plastics. The fracture surfaces were further studied under the Scanning Electron Microscopy(SEM) in order to research the microstructural changes that are taken place during curing. In order to measure the performance of solar energy cured joints the parameters such as; bond strength, surface morphology, the microstructual changes, variation in properties of adhesives bonded joints are compared to that of specimen cured at ambient conditions and specimen cured using microwave techniques.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.304-311
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• 2001

The present work examines the influence of surface coating on the temperature and the thermo-mechanical stress field produced by friction due to sliding contact. A two-dimensional transient model of a layered medium submitted to a moving heat flux is prsented. A solution technique based on the boundary element method employing the multiregion technique is utilized. Results are presented showing the influence of coating thickness, thermal properties, Peclet number, and mechanical properties. It has been shown that the mechanical properties and thickness of coating have a significant influence on the stress field, even for low temperature increase. The effects of the ratios of shear modulus become more important for low temperature increase than the effects of the ratios of other mechanical properties.

• Polymer(Korea)
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• v.26 no.3
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• pp.381-388
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• 2002

The properties of polyurethane (PU) nanocomposites with organoclay have been compared in terms of their thermo-mechanical properties, morphology, and gas permeability. Hexadecylamine-montmorillonite ($C_{16}$-MMT) was used as an organoclay to make PU hybrid films. The properties were investigated as a function of organoclay content (1-4 wt%) in the PU matrix. Transmission electron microscopy (TEM) photographs showed that most clay layers were dispersed homogeneously into the matrix polymer in nano-scale, although some particles of clay were agglomerated. We also found that the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PU hybrid films while gas permeability was reduced. Even at low organoclay content (<5 wt%), the PU nanocomposite showed much better thermo-mechanical properties, and lower gas permeability than pure PU.