• Journal of Power System Engineering
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• v.3 no.2
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• pp.51-56
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• 1999

Fatigue crack propagation rates and characteristics of the SA516-70 steel which is used for the low temperature pressure vessels, were studied in the room temperature of $10^{\circ}C$ and low temperature ranges of $-10^{\circ}C,\;-30^{\circ}C,\;-50^{\circ}C,\;and\;-70^{\circ}C$ with stress ratio of R=0.05. The obtained experimental results are as follows; 1) In the logarithmic relationship between the fatigue crack propagation rate(da/dN) and stress intensity factor K, the linear relationship was obtained up to da/dN > $8{\times}10^3$ mm/cycle in the same of room temperature, but in low temperature case, the relationship was extended to the range of low crack propagation rate. 2) The lower limit stress intensity factor of SA516-70 ${\Delta}K_{th}\;was\;23MPa\sqrt{m}$ and in the case of low temperature $-50^{\circ}C\;and\;-70^{\circ}C$, the crack propagation rate da/dN which showed a linear relation, reached rapidly to the ${\Delta}K_{th}$. As the results, the crack propagation rates of $-50^{\circ}C\;and\;-70^{\circ}C$ were lower than that of room temperature and according to the testing temperature the rates were decreased rapidly to the ${\Delta}K_{th}$. 3) On the relationship between the stress intensity factor ${\Delta}K$ and the track propagation cycle, the stress intensity factors of low cycle region was rapidly increased at low temperature, but ${\Delta}K$ was increased rapidly at room temperature of high cycle. 4) On the relationship between the fatigue crack propagation rate and cycle, the fatigue crack propagation rate showed higher gradient in the room temperature than the low temperature due to the increment in ductility at low temperature.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.240-245
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• 2000

Fatigue crack propagation rates and characteristics of the SA516-60 steel which is used for the low temperature pressure vessels, were studied in the room temperature of $25^{\circ}C$ and low temperature ranges of $10^{\circ}C,\; -10^{\circ}C,\; -30^{\circ}C,\; -50^{\circ}C, \;and\; -70^{\circ}C4 with stress ratio of R=0.05. The obtained experimental results are as follows; 1) In the logarithmic relationship between the fatigue crack propagation rate(da/dN) and stress intensity factor K, the linear relationship was obtained up to da/dN 〉$8\times10^{-3}$/mm/cycle in the same of room temperature, but in low temperature case, the relationship was extended to the range of crack propagation rate. 2) The lower limit stress intensity factor of SA516-60 $\DeltaK_{th}$ was 15.8MPa and in the case of low temperature $-50^{\circ}C\; and\; -70^{\circ}C$, the crack propagation rate da/dN which showed a linear relation, reached rapidly to the $\DeltaK_{th}$/. As the results, the crack propagation rates of $-50^{\circ}C\; and\; -70^{\circ}C$ were lower than that of room temperature and according to the testing temperature the rates were decreased rapidly to the $\DeltaK_{th}$/. 3) On the relationship between the stress intensity factor $\DeltaK$ and the crack propagation cycle, the stress intensity factors of low cycle region was rapidly increased at low temperature, but $\DeltaK$ was increased rapidly at room temperature of high cycle. 4) On the relationship between the fatigue crack propagation rate and cycle, the fatigue crack propagation rate showed higher gradient in the room temperature than the low temperature due to the increment in ductility at low temperature.

• Geomechanics and Engineering
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• v.33 no.5
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• pp.427-437
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• 2023

The objective of this work is to study the wave propagation of an FGM plate via a new integral inverse shear model with temperature-dependent material properties. In this contribution, a new model based on a high-order theory field of displacement is included by introducing indeterminate integral variables and inverse co-tangential functions for the presentation of shear stress. The temperature-dependent properties of the FGM plate are assumed mixture of metal and ceramic, and its properties change by the power functions of the thickness of the plate. By applying Hamilton's principle, general formulas of wave propagation were obtained to plot the phase velocity curves and wave modes of the FGM plate with simply supported edges. The effects of the temperature and volume fraction by distributions on wave propagation of the FGM plate are investigated in detail. The results of the dispersion and the phase velocity curves of the propagation wave in the functionally graded plate are compared with previous research.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.146-151
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• 2001

Low temperature fatigue crack propagation ratio and characteristics of the pressure structural steel which is used for the low temperature pressure vessels. Fatigue crack properties was studied at room temperature of $25^{\circ}C$ and low temperature ranges $-60^{\circ}C,\; -80^{\circ}C \;and\; -100^{\circ}C$ with stress ratio of R=0.05, 0.1, 0.3 in the logarithmic relationship between the fatigue crack propagation rate (da/dN) and stress intensity factor $\DeltaK$, in low temperature case the relationship was extend to the range of low crack propagation rate. The fractured specimens were examined by SEM tested. That results showed specimen failed at low temperature exhibit the quasi-cleavage fracture formation, however, considerable ductility proceed final fracture.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.41-47
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• 2000

Fatigue crack propagation rate and threshold characteristics of the SA516/70 steel which is used for the low temperature pressure vessels, were studied in the room temperature of $25^{\circ}C$ and low temperature ranges of $-10^{\circ}C,\;-30^{\circ}C,\;-60^{\circ}C\;and\;-80^{\circ}C$ with stress ratio of R=0.1. In the logarithmic relationship between the fatigue crack propagation rate($d{\alpha}/dN$) and stress intensity factor range ${\Delta}K$, the linear relationship was obtained up to $d{\alpha}/dN=4.425{\times}10^4mm/cycle$ in the same of room temperature, but in low temperature case, the relationship was extended to the range of low crack propagation rate. The fractured specimens were examined by SEM. Tested results showed that specimen failed at low temperature exhibit the quasi-cleavage fracture formation however considerable ductility proceed final fracture.

• Journal of the Korean Society of Combustion
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• v.1 no.2
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• pp.21-29
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• 1996

Flame propagation characteristics of propane-air mixtures were experimentally investigated in constant-volume combustion chambers. Flame propagation process was observed as a function of mixture strength, initial mixture temperature and initial mixture pressure in quiescent mixtures. A cylindrical combustion chamber and a spherical combustion chamber contain a pair of parallel windows through which optical access into the chamber can be provided. Laser two beam deflection method was adopted to measure the local flame propagation, which gave information on the flame size and flame propagation speed. Pressure development was also measured by a piezoelectric pressure transducer to characterize combustion in quiescent mixtures. Burning velocity was calculated from flame propagation and pressure measurements. The effect of flow on flame propagation was also investigated under flowing mixture conditions. Laser two beam method was found to be feasible in measuring flame propagation of quiescent mixtures. Flame was observed to propagate faster with higher initial mixture temperature and lower initial pressure. Combustion duration was shortened in the highly turbulent flowing mixtures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.12
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• pp.1608-1614
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• 2000

For the purpose of obtaining fundamental data which is needed to develope combustion system of LPG engine, we made constant volume chamber and analyzed flame propagation characteristics under different intial temperature, initial pressure and equivalence ratio which affect combustion of LPG. We investigated flame propagation speed of each fuel using laser deflection method and compared with the investigated flame propagation speed of each fuel using laser deflection method and compared with the results of image processing of flame. As a result, the maximum flame propagation speed was found at equivalence ratio 1.0 and 1.1 for LPG and gasoline, respectively. In the lean region, we can see that flame propagation speed of LPG surpasses that of gasoline. On the contrary, flame propagation speed of gasoline surpasses LPG in the rich region. As initial temperature and initial pressure were higher, flame propagation speed was faster. And, as equivalence ratio was larger and initial temperature was higher, combustion duration was shorter and maximum combustion pressure was higher.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.2
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• pp.225-231
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• 1998

Flame propagation speed characteristics of methante-air mixtures were experimentally investigated in combustion chamber modelled engine. Flame propagation process was known as a funtion of equivalence ratio initial pressure and initial temperature. Ion probe and schlieren photograph were applied to measure the local flame speed and flame radius in quiescent mixtures. Pressure was also measured to make sure of the reproducibility and to apply combustion analysis. Burning velocity was calculated from the flame propagation speed and combustion analysis. Flames were developed faster with higher initial pressure and initial temperature but showed maximum propagation speed at equivalence ratio 1.1 regardless of initial pressure and temperature. Local flame speed was maximum values at near midpoint between center and wall.

• Geomechanics and Engineering
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• v.31 no.6
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• pp.615-622
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• 2022

In this paper, considering the temperature dependence of material physical parameters as well as the effects of thermal effect and shear deformation, we have conducted an in-depth study on the wave propagation of functionally graded (FG) materials circular plate in thermal environment based on the physical neutral surface concept. The dynamic governing equations of functionally graded plates are established, and the dispersion relation of wave propagation is derived. The influence of different temperature fields on the propagation characteristics of flexural waves in FG circular plates is discussed in detail. It can be found that the phase velocity and group velocity of wave propagation in the plate decrease with the increase of temperature.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.70-77
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• 1996

Fatigue tests were carried out at high temperature on a Cr-Mo-V steel in order to assess the fatigue life of components used in power plants. The characteristics of high temperature fatigue were divided in terms of cycle-dependent fatigue and time-dependent fatigue, each crack propagation rate was examined with respect to fatigue J-integral range, .DELTA. J$_{f}$and creep J-integral range, .DELTA. J$_{c}$. The fatigue life was evaluated by analysis of J-integral value at the crack tip with a dimensional finite element method. The results obtained from the present study are summarized as follows : The propagation characteristics of high temperature fatigue cracks are determined by .DELTA. J$_{f}$for the PP(tensile plasticity-compressive plasticity deformation) and PC(tensile plasticity - compressive creep deformation) stress waveform types, and by .DELTA. J$_{c}$for the CP(tensile creep- compressive plasticity deformation) stress waveform type. The crack propagation law of high temperature fatigue is obtained by analysis of J-integral value at the crack tip using the finite element method and applied to examine crack propagation behavior. The fatigue life is evaluated using the results of analysis by the finite element method. The predicted life and the actual life are close, within a factor of 2.f 2.f 2.