• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 추계학술발표대회 논문집
• /
• pp.87-90
• /
• 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.

• 한국지반공학회논문집
• /
• 제35권1호
• /
• pp.43-53
• /
• 2019

본 논문에서는 하수관거 파손에 따른 토사 유실로 인해 발생되는 지중 공동 및 이완영역의 규모를 정량적으로 분석하기 위해 하수관거 파손 폭과 하수관거 상부의 토피고 변화를 고려한 유한요소 수치해석을 실시하였다. 수치해석에서는 선행 연구에서 검증된 역학모델을 적용하였으며, 강제변위법을 이용하여 토사 유실에 따른 하수관거 파손부 주변지반의 역학적 거동을 모사하였다. 수치해석 결과로부터 파손 폭 및 토피고 변화에 따른 모형지반의 간극비 분포, 지표면 침하, 전단응력 분포 특성을 분석하였다. 또한, 지중의 전단응력 감소 특성을 분석하여 지중 공동 및 이완영역의 경계를 결정하였으며, 파손 폭과 토피고 변화에 따른 공동 및 이완영역의 발생 규모를 정량적으로 평가하였다.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제2권1호
• /
• pp.75-78
• /
• 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.

• 한국지구과학회지
• /
• 제34권6호
• /
• pp.524-535
• /
• 2013

재난 리스크 모델을 활용하여 화산재 손실을 평가하기 위해서는 목적물별 손상함수가 정의되어야 한다. 손상함수란 목적물의 재해취약도를 정량화한 함수로, 공학 및 자연재해 연구 분야에서 널리 사용되고 있다. 특히 손상도, 취약성 곡선 등으로 연구되고 있는데, 학제간 연구를 수행하는 과정에서 혼란을 주기도 한다. 이에 본 연구는 손상함수의 유형을 정리하고, 손상함수를 구축한 사례를 소개하고자 한다. 손상함수는 일반적으로 과거 피해사례를 기반으로 구축된다. 국내에 화산재 피해사례가 없음을 고려할 때, 남한지역의 화산재 손상함수를 구축하기 위해서는 해외사례를 참고하여야 할 것이다. 한편 국외에서도 화산재에 대한 손상함수 연구는 다른 재난에 비해 적은데, 화산 피해사례도 적은편이다. 이에 본 연구는 극소수 피해자료를 활용하여 손상함수를 구축할 수 있는 방안을 제시하고, 뉴질랜드와 일본에서 보고된 실제 피해사례를 바탕으로 와이블함수 혹은 선형함수의 취약성 곡선을 구축하였다. 본 연구가 해외사례를 기반으로 손상함수를 구축하였음을 고려할 때, 본 연구에서 제시하는 손상함수를 이용하여 남한지역의 화산재 손실을 평가하기 위해서는 국내 목적물 특성 및 환경 조건에 맞게 손상함수를 보정할 필요가 있다.

• Journal of Biosystems Engineering
• /
• 제27권5호
• /
• pp.381-390
• /
• 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.

• 한국작물학회지
• /
• 제66권3호
• /
• pp.183-189
• /
• 2021

볍씨 종자의 최아정도 및 최아 손상정도에 따른 출현율 및 초기생육변화를 분석한 결과는 다음과 같다. 1. 볍씨 최아 길이가 길수록 출현율은 다소 감소하였으며 생육온도가 18℃ 이상으로 높을수록 차이가 큰 것으로 나타났다. 2. 최아 길이가 길수록 초장신장 속도가 감소하였으며 생육온도가 21℃ 이상으로 높을 시 최아길이 3 mm에서 초장이 크게 감소하였다. 3. 최아길이에 따른 엽수변화는 없었으나 줄기 두께 및 줄기 건물중, 뿌리 건물중은 최아길이가 길수록 유의하게 감소하였다. 4. 최아 손상정도가 증가할수록 출현율은 유의하게 감소하였으며 생육온도가 높을수록 감소폭은 증가하으며 엽수변화는 없었으나 줄기 두께 및 줄기 건물중, 뿌리 건물중은 최아 손상도가 길수록 유의하게 감소하였다. 최아 길이 및 종자 손상정도별 뿌리 건물중과 줄기 건물 중 변화는 유의한 정의 상관관계를 보였다.

• Geomechanics and Engineering
• /
• 제21권2호
• /
• pp.95-102
• /
• 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
• /
• 제20권5호
• /
• pp.281-288
• /
• 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
• /
• 제26권3호
• /
• pp.163-177
• /
• 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
• /
• 제33권6호
• /
• pp.643-658
• /
• 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.