• Title/Summary/Keyword: Thermo-Physical Properties

Search Result 97, Processing Time 0.027 seconds

Residual Stress Distribution on the Fillet Weldment used by Finite Element Method (유한요소법을 이용한 필렛용접 이음부의 잔류응력분포)

  • Kim, Hyun Sung;Woo, Sang Ik;Jung, Kyoung Sup
    • Journal of Korean Society of Steel Construction
    • /
    • v.12 no.2 s.45
    • /
    • pp.197-207
    • /
    • 2000
  • A transient heat transfer analysis and thermo-elastic analysis have been performed for the residual stress distribution on the fillet weldment used by finite element method. Specimen is fabricated single-pass fillet welding. This computation was performed for conditions including surface heat flux and temperature dependent thermo-physical properties using by heat input as parameter. Also, cut-off temperature of residual stress estimation by thermo-elastic analysis is determined. The fillet weldment were measured to determined their residual stress distributions for using hole-drilling method. As result, it was found that large tensile residual stress is about material yield strength, and the numerical simulation results for finite element method similar to residual stresses by hole-drilling method and other exiting research. Also, cut-off temperature is effectively determined by temperature which calculated maximum thermal stress equal to material yield strength.

  • PDF

Application of the BWRS equation of state of polar halocarbons (극성 할로겐 탄화수소 화합물 물성 예측에 BWRS 상태 방정식의 응용)

  • 이태종;김부웅
    • Journal of Energy Engineering
    • /
    • v.2 no.3
    • /
    • pp.315-322
    • /
    • 1993
  • The generalized 23 constants of the Benedict-Webb-Rubin-Starling (BWRS) equation of state were modified to achieve accurate predictions of thermo-physical properties for polar halocarbons. Multiproperty analysis was employed to obtain an optimum set of 23 constants for individual halocarbons. The overall average absolute deviations of predicted properties for those halocarbons using the 23 constants optimized for each halocarbon with use of either an acentric factor or orientation parameters are 0.41% for density, 0.33 Kcal/kg for enthalpy and 0.39% for vapor pressure. These results show a remarkable improvement in predicting properties over the ones obtained by use of the generalized constants for all the ten halocarbons tested here.

  • PDF

Steel nitriding optimization through multi-objective and FEM analysis

  • Cavaliere, Pasquale;Perrone, Angelo;Silvello, Alessio
    • Journal of Computational Design and Engineering
    • /
    • v.3 no.1
    • /
    • pp.71-90
    • /
    • 2016
  • Steel nitriding is a thermo-chemical process leading to surface hardening and improvement in fatigue properties. The process is strongly influenced by many different variables such as steel composition, nitrogen potential, temperature, time, and quenching media. In the present study, the influence of such parameters affecting physic-chemical and mechanical properties of nitride steels was evaluated. The aim was to streamline the process by numerical-experimental analysis allowing defining the optimal conditions for the success of the process. Input parameters-output results correlations were calculated through the employment of a multi-objective optimization software, modeFRONTIER (Esteco). The mechanical and microstructural results belonging to the nitriding process, performed with different processing conditions for various steels, are presented. The data were employed to obtain the analytical equations describing nitriding behavior as a function of nitriding parameters and steel composition. The obtained model was validated, through control designs, and optimized by taking into account physical and processing conditions.

Structures and Physical Properties of in situ composite based on Liquid Crystalline Polymer and Poly(ethylene 2,6-naphthalate) Blends

  • Yoo, Hyun-Oh;Kim, Seong-Hun;Hong, Soon-Man;Hwang, Seung-Sang
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 1998.10a
    • /
    • pp.236-239
    • /
    • 1998
  • The in situ composites based on poly(ethylene 2,6-naphthalate) and thermotropic liquid crystalline polymer (LCP) have been an area of increasing interest and study, since LCP exhibits high chemical stabilities and excellent thermo mechanical properties such as high strength and modulus. In a binary, however, poor compatibility and interfacial adhesions between two phases frequently results in deteriorated mechanical properties. (omitted)

  • PDF

A Numerical Analysis of Supersonic Intake Buzz in an Axisymmetric Ramjet Engine

  • Yeom, Hyo-Won;Sung, Hong-Gye;Yang, Vigor
    • International Journal of Aeronautical and Space Sciences
    • /
    • v.16 no.2
    • /
    • pp.165-176
    • /
    • 2015
  • A numerical analysis was conducted to investigate the inlet buzz and combustion oscillation in an axisymmetric ramjet engine with wedge-type flame holders. The physical model of concern includes the entire engine flow path, extending from the leading edge of the inlet center-body through the exhaust nozzle. The theoretical formulation is based on the Farve-averaged conservation equations of mass, momentum, energy, and species concentration, and accommodates finite-rate chemical kinetics and variable thermo-physical properties. Turbulence closure is achieved using a combined scheme comprising of a low-Reynolds number k-${\varepsilon}$ two-equation model and Sarkar's compressible turbulence model. Detailed flow phenomena such as inlet flow aerodynamics, flame evolution, and acoustic excitation as well as their interactions, are investigated. Mechanisms responsible for driving the inlet buzz are identified and quantified for the engine operating at subcritical conditions.

Approximate Solution for Conjugate Heat Transfer of Laminar Film Condensation on a Flat Plate (평판의 층류 막응축에서 복합열전달에 대한 근사해)

  • Lee Euk-Soo
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.29 no.5
    • /
    • pp.509-518
    • /
    • 2005
  • Liquid film thickness in laminar film condensation for flow over a flat plate generally is so thin that both fluid acceleration and thermal convection within the liquid film can be neglected. An integral solution method is proposed to solve the conjugate problems of laminar film condensation and heat conduction in a solid wall. It is found that approximate solutions of the governing equations involve four physical parameters to describe the conjugate heat transfer problem for laminar film condensation. It is shown that the effects of interfacial shear. mass transfer and local heat transfer are strongly dependent on the thermo-physical properties of the working fluids and the Jacob number.

Preparation and Hydrogen Permeability of SiC-Y2O3 Composite Membranes

  • Son, Boyoung;Jung, Miewon
    • Journal of the Korean Ceramic Society
    • /
    • v.50 no.6
    • /
    • pp.495-497
    • /
    • 2013
  • SiC-$Y_2O_3$ porous composites were fabricated using $Y_2O_3$ powders synthesized by sol-gel process to control physical and thermo-chemical properties. $Y_2O_3$ powders were mixed with SiC powders by co-pressing with HPCS (hydridopolycarbosilane) binder at moderate temperature. The properties of membranes were characterized by XRD, FE-SEM, and BET surface analysis. Hydrogen permeability was performed at various temperatures.

An Finite Element Analysis for Elasto-Plastic Thermal Stresses Considerating Strain Hysteresis at Quenching Process of Carbon Steel(II) - Analysis of elasto-viscoplastic thermal stress - (탄소강의 퀜칭처리 과정에서 변형율이력을 고려한 탄소성열응력의 유한요소 해석(II) - 탄점소성 열응력 해석 -)

  • Kim, Ok-Sam;Koo, Bon-Kwon
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.9 no.2
    • /
    • pp.147-158
    • /
    • 1996
  • Generally, analytical consideration on the behaviour of metallic structures during quenching process, and analysis on the thermal stress and deformation after heat treatment are very important in presumption of crack and distorsion of quenched material. In this study a set of constitute equations relevant to the analysis of thermo elasto-viscoplastic materials with strain hysteresis during quenching process way presented on the basis of contimuum thermo-dynamics mechanics. The thermal stresses were numerically calculated by finite element technique of weighted residual method and the principle of virtual work. In the calculation process, the temperature depandency of physical and mechaniclal properties of the material in consideration. On the distribution of elasto-viscoplastic thermal stresses according to radial direction, axial and tangential stress are tensile stress(50MPa, 1.5GPa and 300MPa) in surface and compressive stress(-1.2GPa, -1.14GPa and -750MPa) in the inner part on the other hand, radial stress is tensile stress(900MPa) in area of analysis. According to axial direction, tangential stress gradients are average 60MPa/mm on the whole. The reversion of stress takes place at 11.5 to 16.8mm from the center in area of analysing.

  • PDF

A thermal properties of micro hot-plate fabricated by using the Pt/Cr bilayer (Pt/Cr 이중층을 이용한 미세 발열체의 제작과 발열특성)

  • Yi, Seung-Hwan;Suh, Im-Choon;Sung, Yong-Kwon
    • Proceedings of the KIEE Conference
    • /
    • 1996.07c
    • /
    • pp.1982-1984
    • /
    • 1996
  • In this paper, we have evaluated the physical characteristicsof the Pt/Cr bilayer, fabricated the micro hot plate by using the Pt/Cr bilayer and E-beam evaporated oxide as a passivation layer, and simulated the thermal distribution by using the commercial software FIDAP. From the researches the sheet resistance of Pt/Cr bilayer didn't be affected by the Cr layer thickness. This results was considered due to the Cr-oxide resided at the interface between Pt and Cr layer. After manufacturing the hot plate, we measured its temperature by type k thermo-couple and I.R. thermo-vision system. In those experiments, the emission coefficient( ${\varepsilon}$ ) of the E-beam evaporated oxide was 0.5 and the temperature of centural region was reached about $305\;^{\circ}C$ at 1.3 watts. The temperature simulation obtained by FIDAP commercial package stewed that the temperature of centural region was about $311\;^{\circ}C$ after 5 sec.

  • PDF

Physical Properties of Graphite Nanofiber Filled Nylon6 Composites

  • Park, Eun-Ha;Joo, Hyeok-Jong
    • Carbon letters
    • /
    • v.7 no.2
    • /
    • pp.87-96
    • /
    • 2006
  • This paper describes the physical properties of filled Nylon6 composites resin with nano-sized carbon black particle and graphite nanofibers prepared by melt extrusion method. In improving adhesions between resin and fillers, the surface of the carbon filler materials were chemically modified by thermo-oxidative treatments and followed by treatments of silane coupling agent. Crystallization temperature and rate of crystallization increased with increases in filler concentration which would act as nuclei for crystallization. The silane treatments on the filler materials showed effect of reduction in crystallization temperature, possibly from enhancement in wetting property of the surface of the filler materials. Percolation transition phenomenon at which the volume resistivity was sharply decreased was observed above 9 wt% of carbon black and above 6 wt% of graphite nanofiber. The graphite nanofibers contributed to more effectively in an increase in electrical conductivity than carbon black did, on the other hand, the silane coupling agent negatively affected to the electrical conductivity due to the insulating property of the silane. Positive temperature coefficient (PTC) phenomenon, was observed as usual in other composites, that is, temperature increase results conductivity increase. The dispersity of the fillers were excellently approached by melt extrusion of co-rotational twin screw type and it could be illustrated by X-ray diffraction and SEM.

  • PDF