• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.310-315
• /
• 2000

We analyzed thermal stress of the STS VOD ladle by the variation of material property of refractory, and determined the location of back filler using FE analysis. Thermal distribution of refractory of ladle between hot face and back face were decreased by the increasing the thermal conductivity, and thermal stress of refractory were decreased about 2 to 4 times with the decreasing the young's modulus coefficients. Back filler, which is constructed to absorb the thermal expansion of dolomite refractory, has relatively low thermal conductivity. Inner side of refractory of ladle maintained high temperature, but temperature of outer side of ladle decreased low. Consequently, inner expansion and outer contraction were appeared. and thermal stress were increased, so thermal stress by the construction of back filler were increased.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.10
• /
• pp.1571-1579
• /
• 1997

The development of a new material which should be continuously use under severe environment of very high temperature has been urgently requested. For the development of such super-heat resistant materials, the main problem is not only to make the superior thermal barrier properties but also to actively release thermal stress. So, a new concept of functionally graded material(FGM) has been proposed to overcome this problem. A composition and microstructure of FGM are varied continuously from place to place in ways designed to provide it with the maximum function of mitigating the induced thermal stress. So, FGM can be applied in the aerospace, the electronic and the medical field, etc.. In this study, thermal stress analysis of sintering PSZ/NiCrAlY graded material was conducted theoretically using a finite-element program. The temperature condition was sintering temperature assuming a cooling-down process up to room temperature. Fracture damage mechanism was anlayzed by the parameters of residual stress. It could be known that FGM provided with the function of mitigating the induced thermal stress.

• Nuclear Engineering and Technology
• /
• v.33 no.2
• /
• pp.132-144
• /
• 2001

Fracture mechanics is one of the major areas of the pressurized thermal shock (PTS) evaluation. To evaluate the reactor pressure vessel integrity associated with PTS, PFM methodology demands precise calculation of temperature, stress, and stress intensity factor for the variety of PTS transients. However, the existence of stainless steel cladding, with different thermal, physical, and mechanical property, at the inner surface of reactor pressure vessel complicates the fracture mechanics analysis. In this paper, treatment schemes to evaluate stress and resulting stress intensity factor for RPV with stainless steel clad are introduced. For a reference transient, the effects of clad thermal conductivity and thermal expansion coefficients on deterministic fracture mechanics analysis are examined.

• Nuclear Engineering and Technology
• /
• v.54 no.6
• /
• pp.2188-2197
• /
• 2022

To ensure the safety margin of a reactor pressure vessel (RPV) under normal operating conditions, it is regulated through the pressure-temperature (P-T) limit curve. The stress intensity factor (SIF) obtained by the internal pressure and thermal load should be obtained through crack analysis of the nozzle corner crack in advance to generate the P-T limit curve for the nozzle. In the ASME code Section XI, Appendix G, the SIF via the internal pressure for the nozzle corner crack is expressed as a function of the cooling or heating rate, and the wall thickness, however, the SIF via the thermal load is presented as a polynomial format based on the stress linearization analysis results. Inevitably, the SIF can only be obtained through finite element (FE) analysis. In this paper, simple prediction equations of the SIF via the thermal load under, cool-down and heat-up conditions are presented. For the Korean standard nuclear power plant, three geometric variables were set and 72 cases of RPV models were made, and then the heat transfer analysis and thermal stress analysis were performed sequentially. Based on the FE results, simple engineering solutions predicting the value of thermal SIF under cool-down and heat-up conditions are suggested.

• Journal of Korea Foundry Society
• /
• v.11 no.3
• /
• pp.245-253
• /
• 1991

It is known that the analysis of thermal stresses is substantially important in optimal design of casting mould. In this paper unsteady state thermal stresses generated in ingot and mould during the solidification process are analyzed by the two dimensional thermal elasto-plastic analysis. Distribution of temperature and stress of the mould is calculated using the finite element method and compared with experimental result. The significant results obtained in this study are as follows. At the early stage of the casting process, abrupt temperature change was shown in the vicinity of the inner surface of the mould. The largest temperature gradient is occurred at the corner of the mould. In the thermal stress analysis, compressible stress occurred in the inside wall of the mould where as tensile stress on outside wall. Smaller thermal stress is observed at the rounded corner. It is also observed that the shown is influenced by the thickness of the wall. A fairly good coincidence is found between analytical and experimental results, showing that the proposed analytical methodology is reliable.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1617-1621
• /
• 2005

In this study, as a basic research to improve braking efficiency of a ventilated disk brake, we carried out a thermal stress analysis. From analysis result, we knew that a maximum mechanical stress by braking pressure and friction force is applicable to 5 percent of yield strength and has no effect on a fatigue life's decrease for brake disk material. While, a maximum thermal stress by frictonal heat is applicable to 43 percent of yield strength and locates on a friction surface. So, we have found that a thermal stress is the primary factor of crack initiation on a friction surface of disk brake

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.11
• /
• pp.227-232
• /
• 1998

The purpose of this study is to develop a numerical method for analyzing the transient heat transfer and evaluating the residual stress. The analysis of heat transfer and thermal stress are carried out by three-dimensional finite element method. Thermal spraying is one of the most common surface coating techniques to be used for many applications. In order to improve the mechanical properties of flame-sprayed ceramic coating layer, the accurate and effective analysis of heat transfer and thermal stress is essentially required.

• Journal of Welding and Joining
• /
• v.19 no.6
• /
• pp.658-663
• /
• 2001

Residual stress caused in the weldments with high restraint force are often during welding observed in the weldments of large size nozzles or radial tanks. The reason is that quantitative analysis about thermal stresses during welding is lack for this weldments. To verify FEM theory, the temperature was measured with thermocouple in a real time in this paper. Also analysis of the thermal stress for welding condition is performed by ABAQUS program package on various welding condition in STS butt welding.

• Journal of Korea Foundry Society
• /
• v.13 no.1
• /
• pp.81-93
• /
• 1993

It is well-known that the analysis of elasto-plastic thermal stress and deformation are substantially important in optimal design of metal casting mould. The unsteady state thermal stress and deformation generated during the solidification process of ingot and mould have been analyzed by two dimensional thermal elasto-plastic theories. Distributions of temperature, stress and relative displacement of the mould are calculated by the finite element method and compared with experimental results. In the elasto-plastic thermal stress analysis, compressive stress occurred at the inside wall of the mould whereas tensile stress occurred at outside wall. A coincidence between the analytical and experimental results is found to be fairly good, showing that the proposed analytical method is reliable.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.789-794
• /
• 2002

The relationship is investigated between material modeling of concrete and the evaluation procedure of thermal stress by the hydration heat. In this respect, some important points are suggested to which special attention should be paid to reasonably evaluate the thermal stress using the widely-used structural analysis programs. This study indicates that proper material model should be used to draw incremental stress evaluation that takes into account the change of elastic modulus with time. Some correction techniques are also presented when using the program that don't have proper built-in procedure for the calculation of the thermal stress.