• Journal of Power System Engineering
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• v.18 no.5
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• pp.66-73
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• 2014

This study was considered to occur the local wall thinning at elbow which is flowing the steam and high-pressure water of high-temperature. The angle of elbow is ${\Theta}=45^{\circ}$ and $67.545^{\circ}$. The damage behaviors of inner or outer wall thinning elbow under internal pressure were calculated by FEA(finite element analysis). We compared the simulated results by FEA with experimental data. The FEA results are as follows: In the FEA results of three types of wall thinning ratio, the circumferential and longitudinal stresses show the similar values regardless of the angle of elbow, respectively. The circumferential strain was greater at elbow of small angle, but the longitudinal strain was nearly same. The FEM stress of outer wall thinning elbow was slightly higher than that of the inner wall thinning elbow, and strain was also slightly higher. In the experiments, the circumferential strain was increased with the increase in the internal pressure, and increased rapidly on about 0.2% of strain. The longitudinal strain was small. The strain at break was much smaller than 0.2%. In the relation between pressure and eroded ratio, the criteria that can be used safely under operating pressure and design pressure were obtained. The results of FEA were in relatively good agreement with those of the experiment.

• Journal of Ocean Engineering and Technology
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• v.21 no.1 s.74
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• pp.51-58
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• 2007

This study on the effects of local wall-thinned location on the fracture behavior of pipes was carried out, and the results were compared with the analytical results. Local wall-thinning for the bending test was machined with various sizes on the outside of pipes, in order to simulate the metal loss, due to erosion/corrosion. In addition, we had carried out FE analysis for the pipes with local wall thinning on the inside, and its results were comparatively studied with that of the outside. Three-dimensional elasto-plastic analyses were able to accurately simulate fracture behaviors of inner or outer wall thinning. Fracture types, obtained from the experiments and analyses, could be classified into ovalization, local buckling and crack initiation, depending on the thinned length and thinned ratio. Based on the results, the fracture behaviors of pipes with the outer wall thinning can be applied to estimate the fracture behaviors of pipes with the inner wall thinning.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.76-83
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• 2014

This study was carried out an experimental and finite element analysis on the fracture behavior of straight pipes with local wall thinning under internal pressure. Local wall thinning was machined on the pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area has an eroded ratio of d/t=0.80~0.92 and an eroded length of l=25, 50 and 102 mm. Three-dimensional elastic-plastic analyses were also carried out using the finite element method, which is able to accurately simulate failure behaviors. In regards to the relation ship between pressure and eroded ratio, the criterion that can be used safely under operating pressure and design pressure were obtained from this calculation. The results of this calculation were in relatively good agreement with that of the experiment.

• Journal of Power System Engineering
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• v.18 no.5
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• pp.80-87
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• 2014

The pipelines are apt to erosion or corrosion because of the high-speed flow of water and steam with high temperatures or high pressures. This study was carried out a finite element analysis (FEA) and an experimental for the fracture behavior of T-joint pipes with local wall thinning under internal pressure. Local wall thinning was machined on the pipes in order to simulate erosion and corrosion of the metal. The configurations of the eroded area included an eroded ratio of d/t=0.80~0.963 and an eroded length of l=25 mm, 50 mm, and 102 mm. Three-dimensional elastic-plastic analyses were also carried out using FEA, which accurately simulates failure behaviors. In regards to the relationship between pressure and eroded, the criterion that indicates what can be used safely under operating pressure and design pressure were obtained from FEA. The FEA results were in relatively good agreement with that of the experiment.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.57-62
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• 2008

Difference of failure modes was studied by finite element analysis for elbows with local wall thinning area particularly at inner surface of intrados of the elbow. Longitudinal wall thinning length, minimum thickness were kept constant but circumferential wall thinning width was varied to get $90^{\circ}$, $180^{\circ}$ and $360^{\circ}$ thinning width. Elastic-plastic analysis were carried out under the combined loading conditions of internal pressure and in-plane bending moment closing the elbow. Von Mises stress were obtained from the outer surface central surface location in intrados, extrados and crown parts in elbow. The results showed that the plastic deformation and failure started from the crown location when the thinning width small ($90{\sim}180^{\circ}$). However, plastic collapse started from the intrados location when the thinning width is approaching $360^{\circ}C$. This should be reflected to assess structural integrity of elbows after wall thinning measurement is made.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.463-470
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• 2017

The objectives of this study are to obtain the basic knowledge of anatomical characteristics and wood properties of thinning trees of young teak (Tectona grandis L.F.) for fulfill the timber demand in Indonesia. Nine thinning trees of 5-year-old teak clone trees were used for analyzing the cell morphology and air-dry density. Vessel diameters in pore and outer pore zones were 165 and $90{\mu}m$, respectively. Mean value of fiber diameter, cell wall thickness, and fiber length in outer pore zone were $14.6{\mu}m$, $2.07{\mu}m$, and 1.04 mm, respectively. In addition, mean value of air-dry density was $0.55g/cm^3$. The measurement and values of vessel diameter, fiber diameter, cell wall thickness, fiber length and air-dry density in the experimental had lower than those in the older teak. Therefore, it could be suggested that the wood from thinning young teaks was not appropriate as construction material, but it could be used for furniture which do not need high of strength properties. Furthermore, since the measurements values of anatomical characteristics were still increasing from pith to bark, it could be suggested that 5-year-old teak clones are still in a juvenile phase. Positively significant correlations were found between air-dry density and cell wall thickness, indicating that cell wall thickness is strongly correlated with wood density of teak.

• Journal of Energy Engineering
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• v.28 no.3
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• pp.1-9
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• 2019

A major stress determining the remaining life of the tube in feedwater heater of fossil fuel power plant is hoop stress by the internal pressure. However, thermal stress due to temperature difference across the wall thickness also contributed to reduce the remaining life of the tube. Therefore, thermal loading must be considered even though the contribution of internal pressure loading to the stresses of the tube was known to be much higher than that of the thermal loading. In this study, thermal stress of the tubes in the de-superheating zone was estimated, which was generated due to the temperature difference across the tube thickness. Analytic equations were shown for determining the hoop stress and the radial stress of the tube with uniform thinning and for the temperature across the tube thickness. Accuracy and effectiveness of the analytic equations for the stresses were verified by comparing the results obtained by the analytic equations with those obtained from finite element analysis. Using finite element analysis, the stresses for eccentric thinning were also determined. The effect of heat transfer coefficient on thermal stress was investigated using series of finite element analyses with various values of heat transfer coefficient for both inner and outer surface of the tube. It was shown that the effect of heat transfer coefficient at outer surface was larger than that of heat transfer coefficient at inner surface on the thermal stress of the tube. Also, the hoop stress was larger than the radial stress for both cases of uniformly and eccentrically thinned tubes when the thermal loading was only considered without internal pressure loading.

• Korean Journal of Food Science and Technology
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• v.20 no.6
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• pp.742-748
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• 1988

The macro-and microstructure of Chinese cabbage used for Korean Kimchi preparation were examined and the texture characteristics of raw cabbage leaf and salted or blanched leaves were evaluated by cutting test. The length and thickness of leaf stalk increased with the order of pyllotaxis, but the thinning effect of outermost leaves was observed. The microstructure of cut-profile of stalk showed densely compacted vascular systems aligned in the center of stalk and the outer space was filled with large parenchima cells. Due to this structure, characteristic cutting curves were obtained by cutting test, composing three peaks of cutting for inner surface skin, center vascular system and outer surface skin. Salting and blanching increased the cutting force mainly due to the increase of Gutted cell wall number caused by the structure collapse.

• Corrosion Science and Technology
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• v.18 no.2
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• pp.55-60
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• 2019

Corrosion failure in the convection part of peak load boiler (PLB) of the district heating system led to water leakage. Herein, Internal Rotary Inspection System (IRIS) inspection was employed to examine wall thinning and the cause of leakage in the flue tube. The corrosive products of the turbulator and tube were investigated using scanning electron microscope combined with energy dispersive spectroscopy, X-ray diffraction, and inductively coupled plasma (ICP). Majority of the serious corrosion damage was observed near the turbulator located in the upper flue tube. ICP analysis of the boiler water revealed oxide formation of sodium chloride in the lower end part of the flue tube. A cross-sectional view of the turbulator revealed the presence of double-layers of the oxide film, indicating environmental change during operation associated with water leakage. The outer surface of the turbulator consisted of the acid oxides such as $NO_x$ and $SO_x$ along with sodium and chloride ions. Dew-point corrosion is hypothesized as the main cause for the formation of acid oxides in the region of contact of the flue tube and the turbulator.