• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.87-90
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• 2001

In particle or short-fiber reinforced composites, cracking of the reinforcements is a significant damage mode because the broken reinforcements lose load carrying capacity. This paper deals with elastic stress distributions and load carrying capacity of intact and cracked ellipsoidal inhomogeneities. Three dimensional finite element analysis has been carried out on intact and broken ellipsoidal inhomogeneities in an infinite body under pure shear. For the intact inhomogeneity, as well known as Eshelby(1957) solution, the stress distribution is uniform in the inhomogeneity and non-uniform in the surrounding matrix. On the other hand, for the broken inhomogeneity, the stress in the region near crack surface is considerably released and the stress distribution becomes more complex. The average stress in the inhomogeneity represents its load carrying capacity, and the difference of average stresses between the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The load carrying capacity of the broken inhomogeneity is expressed in terms of the average stress of the intact inhomogeneity and some coefficients. It is found that the broken inhomogeneity with higher aspect ratio still maintains higher load carrying capacity.

• Journal of the Korean Geotechnical Society
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• v.35 no.1
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• pp.43-53
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• 2019

This paper described a result of finite element analysis considering sewerage damage scale and soil depth, in order to analyze quantitatively for cavity and relaxation zone of underground due to sewerage damage. The mechanical model, which was verified by previous studies, was applied to the finite element analysis. In addition, the mechanical behavior of the soil around the sewerage damage due to the soil loss was simulated by using the forced displacement. Based on finite element analysis results, characteristics of the void ratio distribution, ground subsidence, and shear stress distribution according to sewerage damage scale and soil depth were analyzed. And then, The boundaries of the underground cavity and relaxation zone were determined by using the shear stress reduction characteristics of the ground. Also, an occurrence scope of the cavity and relaxation zone was quantitatively evaluated by the change of sewerage damage scale and soil depth.

• International Journal of Industrial Entomology and Biomaterials
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• v.2 no.1
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• pp.75-78
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• 2001

The whitefly, Dialeuropora decempuncta Quaintance and Baker (Homoptera : Aleyrodidae) causing considerable damage to mulberry, Morus alba. Crop loss caused by the whitefly was estimated in mulberry. Quantitative yield loss was estimated on the basis of harvest data from both sprayed and unsprayed plots. Data on pest incidence has been recorded at weekly intervals in both sprayed and unsprayed plots from 30 th day of plant age till harvesting i.e., 60 days after pruning in August October season. An attempt has been made to establish a relationship between whitefly population and percentage of crop loss due to it. Percentage of crop loss due to whitefly has got a linear relationship with the whitefly population. An initial population of 24 adults/top leaf would be able to cause 24% loss (l,630 Kg leaf/ha ) in a period of 30 days. Economic analysis postulates that application of pesticide can stove a net amount of 1,630 Kg leaf/ha which is sufficient to produce 67.65 Kg of additional multivoltine cocoons. This determines the cost/benefit ratio which will enable to workout the economics of management practices.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.524-535
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• 2013

Catastrophe risk models require the damage functions of each vulnerable item in inventory to estimate volcanic ash losses. The damage functions are used to represent the relation between damage factors and damage and also widely used in engineering and natural hazard studies to calculate the vulnerability. In most cases, damage functions are constructed as fragility or vulnerability curves, and researchers are confused by the similarities between them particularly when they perform interdisciplinary research. Thus, we aim to explain the similarities and differences between fragility and vulnerability curves and their relationship by providing case studies to construct them. In addition, we suggest a simple method to construct the damage functions between damage ratio and volcanic ash thickness using limited damage data. This study comes from the fact that damage functions are generally constructed using damage data. However, there is no available volcanic ash damage data in Korea, and not even enough volcanic disaster data to construct damage functions in the world, compared to other hazards. Using the method suggested in the study and the limited damage data from Japan and New Zealand, we construct Weibull-type functions or linear functions dependent of available data to calculate volcanic ash loss estimation, which we think need to be corrected to make it more suitable for inventory characteristics and environmental conditions in Korea.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.381-390
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• 2002

Direct seeding of rice-seed pellets is expected to be an alternative for solving problems in current direct seeding cultivation of rice. but mass production of rice-seed pellets is prerequisite for practical application. Design. construction and performance evaluation of an experimental rice seed pelleting machine were carried out for mass production of rice-seed pellets. The pelleting machine intended to make a ball type rice-seed pellet, which have 3∼5 rice seeds and diameter of which is 12 mm. Pellet materials ; rice seeds, soil, and binder were mixed and kneaded by the mixer. The designed rice seed pelleting machine fed pellet materials by screw conveyor to forming rolls and made rice-seed pellets. Capacity, ratio of perfect rice-seed pellets, seed and pellet material loss were investigated as mixing ratio of soil to rice seed and feeding rate of pellet materials. The pelleting machine showed up to 37,000 pellets/h of pelleting rate, 61∼71% of weight ratio of perfect rice-seed pellets to pellet materials supplied, 17∼48% of seed loss ratio. Average weight and average diameter of the pellets were 1.66 g and 12.0 mm. respectively. More than 3 rice seeds were included in most pellets at 6 : 1 of mixing ratio of soil to rice seed. And compression strength of the pellets was in the range of 88-130 N. To improve performance of the pelleting machine, improvements of the forming rolls, feeding mechanism, and discharging mechanism for reducing loss of pellet materials and seeds damage are needed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.66 no.3
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• pp.183-189
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• 2021

We checked the emergence rate and early growth characteristics of young rice plants according to the germination length and seed damage ratio in direct seeding. The emergence rate was reduced according to the longer germination length and higher seed damage ratio. The emergence rate was further reduced under high-temperature conditions. The leaf number did not show a significant difference according to germination length and seed damage ratio. However, shoot and root dry weights were reduced according to the germination length and seed damage ratio. The root dry weight was highly correlated with the shoot dry weight. Based on these results, we concluded that a longer germination length and seed damage could induce the loss of nutrients and affect poor root growth, consequently inducing poor emergence and growth in the early growth stage of rice seeds. Therefore, in rice direct seeding, seed conditions of less than 1 mm of germination length should be checked for a sufficiently high standing rate and adequate growth characteristics after seeding.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.95-102
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• 2020

Population concentration in urban areas has led traffic management a central issue. To mitigate traffic congestions, the government has planned to construct large-cross-section tunnels deep underground. This study focuses on estimating the damage caused to frame structures owing to tunnel excavation. When constructing a tunnel network deep underground, it is necessary to divide the main tunnel and connect the divergence tunnel to the ground surface. Ground settlement is caused by excavation of the adjacent divergence tunnel. Therefore, predicting ground settlement using diverse variables is necessary before performing damage estimation. We used the volume loss and cover-tunnel diameter ratio as the variables in this study. Applying the ground settlement values to the settlement induction device, we measured the extent of damage to frame structures due to displacement at specific points. The vertical and horizontal displacements that occur at these points were measured using preattached LVDT (Linear variable differential transformer), and the lateral strain and angular distortion were calculated using these displacements. The lateral strain and angular distortion are key parameters for structural damage estimation. A damage assessment chart comprises the "Negligible", "Very Slight Damage", "Slight Damage", "Moderate to Severe Damage", and "Severe to Very Severe Damage" categories was developed. This table was applied to steel frame and concrete frame structures for comparison.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.281-288
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• 2021

Due to advancement of the industry, operation of a device in a harsh environment is increasing. Especially, the marine environment contains Cl^- ions which causes localized corrosion such as pitting and crevice corrosion of stainless steel and various metals. In this study, electrochemical corrosion behaviors of austenitic stainless steel (STS 316L) and nickel alloy (Inconel 600) with different seawater concentrations (fresh water, seawater, mixed water) were investigated. The STS 316L and Inconel 600 were etched in 10% oxalic acid and composed of an austenitic phase. Results of Tafel analysis in seawater showed that STS 316L and Inconel 600 presented the highest corrosion current densities of 7.75 × 10^-4 mA/cm² and 1.11 × 10^-4 mA/cm² and the most negative pitting potentials of 0.94 V and 1.06 V, respectively. The maximum damage depths and surface damage ratio by pitting corrosion increased with chloride concentration. The STS 316L had higher PREN than Inconel 600. However, the surface damage and weight loss of Inconel 600 were superior to STS 316L. It was difficult to compare the pitting resistance of STS 316L based on Fe and Inconel 600 based on Ni with PREN simply.

• Wind and Structures
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• v.26 no.3
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• pp.163-177
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• 2018

Tornadoes are one of the world's deadliest natural phenomena. They are characterized by short life span and danger. It has been observed through post-damage surveys that localities with large numbers of buildings suffer major damage during a tornado attack resulting in huge loss of life and property. Thus,it is important to study interfering buildings exposed to tornado-like vortices. The present study focuses on external and internal pressures developed on building models exposed to translating tornado-like vortices in the presence of an interfering building model. The effects of translating speed and swirl ratio of a tornado-like vortex on external and internal pressures for a principal building in the vicinity of an interfering building are investigated. Results indicate that external and internal pressures are enhanced or reduced depending on the location of the interfering building with respect to the principal building.

• Computers and Concrete
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• v.33 no.6
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• pp.643-658
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• 2024

To date, shell-solid and fibre element model analysis are the most commonly used methods to investigate the seismic performance of concrete-filled steel tube (CFST) bridge piers. However, most existing research does not consider the loss of bearing capacity caused by the fracture of the outer steel tube. To fill this knowledge gap, a refined finite element (FE) model considering the ductile damage of steel tubes and the behaviour of infilled concrete with cracks is established and verified against experimental results of unidirectional, bidirectional cyclic loading tests and pseudo-dynamic loading tests. In addition, a parametric study is conducted to investigate the seismic performance of CFST bridge piers with different concrete strength, steel strength, axial compression ratio, slenderness ratio and infilled concrete height using the proposed model. The validation shows that the proposed refined FE model can effectively simulate the residual displacement of CFST bridge piers subjected to highintensity earthquakes. The parametric analysis indicates that CFST piers hold sufficient strength reserves and sound deformation capacity and, thus, possess excellent application prospects for bridge construction in high-intensity areas.