• Geomechanics and Engineering
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• 제12권6호
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• pp.1021-1046
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• 2017

The assessment of slope stability is an essential task in geotechnical engineering. In this paper, a three-dimensional (3D) finite element analysis (FEA) was employed to investigate the performance of different shear pin arrangements to increase the stability of a soil block resting on an inclined plane with a low-interface friction plane. In the numerical models, the soil block was modeled by volume elements with linear elastic perfectly plastic material in a drained condition, while the shear pins were modeled by volume elements with linear elastic material. Interface elements were used along the bedding plane (bedding interface element) and around the shear pins (shear pin interface element) to simulate the soil-structure interaction. Bedding interface elements were used to capture the shear sliding of the soil on the low-interface friction plane while shear pin interface elements were used to model the shear bonding of the soil around the pins. A failure analysis was performed by means of the gravity loading method. The results of the 3D FEA with the numerical models were compared to those with the physical models for all cases. The effects of the number of shear pins, the shear pin locations, the different shear pin arrangements, the thickness and the width of the soil block and the associated failure mechanisms were discussed.

• 비파괴검사학회지
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• 제13권4호
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• pp.32-41
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• 1994

탄성파에 의한 미소 동적 변위를 측정하기 위하여 안정화 회로가 부착된 Michelson 간섭계를 개발하였다. 안정화 회로는 외부 진동신호에 따른 광로차의 교란을 보상하기 위하여 압전구동기가 부착된 기준거울을 사용하였다. 안정화 회로를 사용함으로써, 간섭계는 외부 진동신호의 영향을 줄일 수 있었고, 항상 직각조건(quadrature condition)을 만족하여 광검출기의 출력신호가 최대의 감도와 선형성을 유지할 수 있었다. 검출가능한 최소 변위는 10MHz 대역에서 0.3nm 이었다. 개발된 간섭계를 사용하여 유리관 파괴 및 강철구 충격에 의한 진앙점에서의 변위를 검출하여 이론적으로 계산된 값과 비교하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.275-279
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• 1996

In this study, the effect of external restraint on the thermal stresses and thermal cracking mode in mass concrete are analysed using the two major factors affecting external restraint such as the ratio of width go height of the placed structure (L/H) and the elastic modulus of base structure (E). For this parametric study, many cases with different values of L/H and Er are analysed by the FEM program and the co-relationship of the those major factors is examined. To evaluate the effect of external restraint on the thermal behavior of placing structure, internal restraint stress caused by temperature difference is subtracted from total thermal stress. In the case of small value of L/H or Er, it shows as internally restricted mode indicating maximum tensile stress in surface at early age, and the external restraint makes the possibility of thermal cracking higher. However, in the case of the large values of L/H and Er, the crack index at center is smaller than at surface due to the effect of external restraint. Thus, the initial location of the thermal crack is shifted from the surface to the center and the resulting crack is formed at later age.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4642-4647
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• 2011

평면 변형률 상태에 있는 탄성지반의 해를 변분법을 적용하여 유도하여 보았다. 변분법 적용시 종방향 변위분포 함수는 선형함수를 고려하였다. 탄성지반상에 작용하는 하중조건은 집중하중과 분포하중을 고려하였는데 집중하중 작용시 탄성지반의 종방향 변위분포양상은 하중 작용점에서 멀어질수록 변위가 급격하게 감소하는 양상을 나타내었다. 등분포하중 작용시 지표면 변위는 압축층 두께에 대한 재하폭의 반의 비(B/H)값이 클수록 하중재하부분 아래에서 보다 균등하게 발생하였다. 또한 하중재하부분을 벗어난 영역에서는 B/H 값이 커질수록 하중재하 모서리 부분으로부터 짧은 거리에서 변위가 0에 수렴하였다.

• 소성∙가공
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• 제22권4호
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• pp.196-203
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• 2013

Flexible stretch forming is an appropriate process for manufacturing of components for aerospace, shipbuilding and architecture structures. Flexible stretch forming has several advantages including that it could be applied to form various shapes such as ones with double curved surfaces. In this study, a systematic numerical simulation was conducted for forming double curved surfaces using flexible stretch forming. The desired surface had a saddle type configuration. It had two radii one of 2500mm and the other of 2000mm along its length and width. In the simulation, the decrease of elastic recovery due to the stretching was confirmed. Experiments were also conducted to confirm the viability of the process. By comparing the simulation to the experiment results, the suitability of flexible stretch forming for double curved surfaces was verified. From the results, the maximum error from desired surface was confirmed at about 1.3mm at the edge of the surface. Hence, it is confirmed that flexible stretch forming has the capability and feasibility to manufacture curved surfaces for architectural skin-structures of buildings.

• 대한소아치과학회지
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• 제21권2호
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• pp.510-517
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• 1994

It is a relatively common clinical experience to see a impacted maxillary central incisor. This is apparent at the dental age of about eight years and over, when the patient is in the early mixed dentition stage. The adjacent teeth may tilt toward the site of the missing tooth with resulting space closure and midline deviation. Most often, the central incisor is impacted labially. The labial impaction has been indicated as the most difficult to manage. Each of the current articles describing labial impactions shows at least one case with mucogingival recession or a minimal zone of attached gingiva. This report described the surgical uncovering and orthodontic-physiologic positioning methods with labially impacted maxillary central incisors. Through surgical exposure and direct bonding of lingual botton, the central incisors were brought into proper eruption path with elastic traction. The case 1 and 2 were treated with the physiologic erupting forces. The case 3 was applied with continuous orthodontic force. The case 1 and 2 resulted in good positioning, good esthetics and adequate width of keratinised gingiva. The case 3 resulted in local inflammation and inadequate width of keratinised gingiva.

• Geomechanics and Engineering
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• 제8권6호
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• pp.829-844
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• 2015

In the current paper the results of a numerical simulation that were verified by a well instrumented experimental procedure for studying the arching effect over a trapdoor in sand is presented. To simulate this phenomenon with continuum mechanics, the experimental procedure is modeled in ABAQUS code using stress dependent hardening in elastic state and plastic strain dependent frictional hardening-softening with Mohr Coulomb failure criterion applying user sub-routine. The apparatus comprises rectangular trapdoors with different width that can yield downward while stresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole soil mass deforms elastically. However, after an immediate specified displacement, depending on the width of the trapdoor, the soil mass behaves plastically. This behavior of sand occurs due to the flow phenomenon and continues until the stress on trapdoor is minimized. Then the failure process develops in sand and the measured stress on the trapdoor shows an ascending trend. This indicates gradual separation of the yielding mass from the whole soil body. Finally, the flow process leads to establish a stable vault of sand called arching mechanism or progressive collapse of the soil body.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1579-1586
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• 2020

Dissimilar metal joints (DMJs) are more common in the application of piping system of many industries. A 2- D and 3-D finite element analysis (FEA) is carried out on dissimilar metal Single Edged Notch Bending (DMSENB) specimens fabricated from ferritic steel, austenitic steel and Inconel - 182 alloy to study the behavior of DMJs with constraints by using linear elastic fracture mechanics (LEFM) principles. Studies on DMSENB specimens are conducted with respect to (i) dissimilar metal joint width (DMJW) (geometrical constraints) (5 mm, 10 mm, 20 mm, 30 mm and 50 mm) (ii) strength mismatch (material constraints) and (iii) crack lengths (16 mm, 20 mm and 24 mm) to study the DMJ behavior. From the FEA investigation, it is observed that (i) SIF increases with increase of crack length and DMJWs (ii) significant constraint effect (geometry, crack tip and strength mismatch) is observed for DMJWs of 5 mm and 10 mm (iii) stress distribution at the interfaces of DMSENB specimen exhibits clear indication of strength mismatch (iv) 3-D FEA yields realistic behavior (v) constraint effect is found to be significant if DMJW is less than 20 mm and the ratio of specimen length to the DMJW is greater than 7.4.

• 대한토목학회논문집
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• 제12권3호
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• pp.17-24
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• 1992

철근(鐵筋)콘크리트 슬래브교(橋) 설계시(設計時) 교각(橋脚)을 T형 및 ${\Pi}$형식으로 취하는 것보다 기둥만으로 슬래브를 직접 지지(支持)하도록 함으로써 유효공간(有效空間) 확보 뿐만 아니라 슬래브 자체(自體)의 내하력(耐荷力)을 이용함으로써 구조적(構造的)인 효율측면(效率側面)에도 유리하다. 그러나 기둥으로 지지된 슬래브교의 설계를 위한 휨모멘트계산은 아직 체계화(體系化)되어 있지 않은 상태이다. 중간지지점(中間支持點)의 종방향(縱方向) 최대휨모멘트를 유효폭개념(有效幅槪念)을 적용하여 가상지간(假像支間)을 이용한 단순보해석으로 간단히 구할 수 있는 방법(方法)에 대하여 연구하고 유효폭을 수식화(數式化)하였다. 주요변수(主要變數)는 지간(支間), 교폭(橋幅), 슬래브 두께 및 기둥단면(斷面)으로 하고 유한요소법(有限要素法)을 이용하여 단면력(斷面力)의 변화를 조사하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.343-343
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• 2008

Newly designed structure of a thin ultrasonic rotary motor was proposed. Thin brass plate was used as a cross shaped vibrator and eight ceramic plates were attached on the upper and bottom sides of the brass plate as in Figure 1. The thin type ultrasonic motor has the structure adherent piezoelectric ceramic on the top and bottom surface of the thin elastic body. The direction of polarization is decided so as to occur the elliptical displacement in regular sequence at touch point A, B, C and D of stator contacted with rotor. By applying two electric fields which have 90 degree phase difference on the ceramics, each contact points make rotational displacements as in figure 2. Finite element analysis program ATILA was used to find the optimal size of the stator. As a result of the simulation, elliptical displacements of the tips were obtained at off-resonance frequencies. The maximum displacements of the contact tips were obtained at the length of 16[mm], width of 6[mm] and thickness of 0.4[mm]. Changes of the resonance frequencies were inversely proportional to the length of ceramic and proportional to the width of ceramic. Elliptical motions of the contact tips. of the stator were consistently obtained at off resonance frequencies. From a prototype motor, speed of 600[rpm] was obtained at 20[Vrms].