• Journal of Forest and Environmental Science
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• 제26권3호
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• pp.193-202
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• 2010

To analyze the effects of tree roots on the stability of damage slope, distributional and physical properties of five-year Pinus densiflora roots were investigated. In the composition of roots, the proportion of main root to lateral root was 1 to 9 in slope condition. Root tensile force was increased in accordance with increased proportion to diameter of Pinus densiflora roots. However, tensile strength was decreased in proportion to diameter of roots. Root shear strength showed that soil containing Pinus densiflora roots was higher than that of non-treated soils. This result shows that Pinus densiflora roots significantly stabilize the surface-soil rather than sub-soil in damage slopes.

• 한국환경생태학회지
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• 제25권1호
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• pp.31-36
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• 2011

본 연구는 사면안정해석에 필요한 기초자료를 제공하고자 잣나무, 낙엽송, 소나무, 신갈나무, 오리나무를 대상으로 교목류 뿌리의 인장력 및 인장강도를 측정 분석하였다. 그 결과 인장력은 대부분 뿌리 직경의 거듭제곱의 형태로 증가하는 것으로 나타났다. 또한 뿌리의 평균 인장강도는 잣나무 $165.38kgf/cm^2$, 낙엽송 $172.78kgf/cm^2$, 소나무 $176.25kgf/cm^2$, 오리나무 $214.29kgf/cm^2$, 신갈나무 $224.19kgf/cm^2$로 나타났으며, 뿌리의 직경이 커질수록 인장강도가 감소하는 경향을 나타냈다. 측정 분석된 인장강도를 기초자료로 토양의 전단강도 증가값을 산출한 결과 잣나무 $0.099kgf/cm^2$, 낙엽송 $0.104kgf/cm^2$, 소나무 $0.106kgf/cm^2$, 오리나무 $0.129kgf/cm^2$, 신갈나무 $0.135kgf/cm^2$인 것으로 나타났다.

• 대한치과교정학회지
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• 제28권3호
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• pp.391-398
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• 1998

본 연구는 유한요소법을 사용하여 상악견치에 intrusion arch wire를 강제로 engage시켰을 때 상악 견치와 치근막에서 발생되는 압축력과 인장력의 분포의 양을 알아보고 어느 부분에 집중되는가를 분석하였다. 또한 각 부분에서의 압축력과 인장력의 비율을 비교하기 위해서 시행하여 다음과 같은 결과를 얻었다. 1. 상악 견치의 FA point와 백악법랑경계부분에서는 압축력과 인장력의 비율이 거의 비슷하게 나타났다. 2. 치근첨 부분에서는 압축력이 인장력의 거의 4배정도 크게 나타났다. Intrusion force적용시 치근흡수 정도가 치근첨에서 발생되는 것을 정량화시켜서 보여준 결과이다. 3. 백악법랑경계부분은 즉 FA point를 제외하고는 압축력과 인장력이 가장 큰 값을 보이고 있다. 즉 치아에 교정력이 직접 적용된 부분을 제외하고는 치아와 치주인대가 처음 접촉되는 백악법랑경계부에서 응력이 집중되는 것을 유추할 수 있다.

• 한국산림과학회지
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• 제97권4호
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• pp.392-397
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• 2008

산불피해지역의 소나무림을 대상으로 4년 동안 뿌리의 강도 특성변화를 시간의 경과에 따라 만능재료시험기를 이용하여 소나무 뿌리의 직경급별로 인장력과 인장강도를 측정 분석하였다. 그 결과 뿌리 직경급에 따른 산불발생 후 년차별 인장강도의 변화는 뿌리의 직경급이 큰 경우보다는 직경급이 작은 뿌리에서 강도저하폭이 큰 것으로 나타났다. 특히, 조사된 모든 직경급에서 2년차에 가장 많은 강도저하율을 나타냈고, 평균적으로는 약 61%의 인장강도가 저하되는 것으로 나타났다. 또한 시간변화에 따른 소나무뿌리의 직경급별 인장강도저하를 미분방정식을 통해 모델링한 결과, 모든 뿌리 직경급대에서 산불발생 후 2년 이내에 50%이상의 인장강도저하가 발생하는 것으로 분석되었다.

• 대한치과교정학회지
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• 제32권5호
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• pp.343-353
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• 2002

제1소구치 발치를 동반한 설측교정치료시 lingual K-loop archwire로 전치부 후방견인을 시 행한 경우 전치부 및 구치부에서 치조골에 발생하는 초기응력을 알아보기 위하여, K-loop의 vortical leg 길이는 15mm로 하고 편측당 350gm의 힘으로 활성화시 킨 후 상악궁 광탄성 모형의 응력동결을 시행하고 각 치아별로 절단하여 3차원 광탄성법으로 분석한 바 다음과 같은 결론을 얻었다. 1. 중절치의 근심면은 치관측일수록 더 큰 인장응력을 보였으며 원심면은 치관측일수록 더 큰 압축응력을 보였다. 순면에서는 치관측일수록 더 큰 인장응력을 보였으며 설면에서는 치근측일수록 더 큰 압축응력을 보였다 치근첨에서는 압축응력이 나타났다. 2. 측절치의 근심면에서는 치관측만 인장응력이 관찰되었고 원심면에서는 고른 압축응력을 보였다. 순면에서는 치관측일수록 더 큰 인장응력이 관찰되었고 설면에서는 치관측에서는 인장응력을, 치근측에서는 압축응력을 보였다. 치근첨에서는 압축응력이 관찰되었다. 3. 견치의 근심면은 치관측에서는 인장응력을, 치근측에서는 압축응력을 보였고 원심면은 인장응력을 보였다. 순면과 설면은 치관측일수록 큰 인장응력을 보였다. 순면보다 설면에서 더 큰 인장응력을 보였다. 치근첨에서는 압축응력이 관찰되었다. 4. 제2소구치는 근심면은 인장응력을 보이며 원심면은 치관측에서는 압축응력을, 치근측에서는 인장응력을 보였다. 협면은 치관측에서 압축응력을 보였으며, 설면은 치관측일수록 더 큰 인장응력이 관찰되었다. 치근첨에서는 인장응력을 보였다. 5. 제1대구치는 근원심면 모두에서 치관측일수록 더 큰 인장응력을 보였다. 협면에서는 응력이 나타나지 않았고, 설면은 치관측일수록 더 큰 인장응력이 관찰되었다. 협측치근들의 치근첨에서는 압축응력을, 구개측치근의 치근첨에서는 무응력을 보였다. 6. 제2대구치는 모든 치근의 치근첨에서 압축응력이 관찰되었다. 근심면은 치관측일수록 더 큰 압축응력을, 원심면은 치관측일수록 더 큰 인장응력을 보였다 협면은 치관측일수록 더 큰 인장응력을, 설면은 치관측일수록 더 큰 압축응력을 나타내었다. 따라서 전치부 후방견인시 transverse bowing effect는 뚜렷이 나타났으나, vertical bowing effect는 나타나지 않고 오히려 전치부가 함입되려는 응력이 발생하였다.

• 대한치과보철학회지
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• 제31권4호
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• pp.468-481
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• 1993

The Purpose of this study was to analyze the stresses and displacements of various post and core. The Finite element models of central incisors were divided into seven types according to the various amount of remaining tooth structures. $10kgf/mm^2$ force was applied respectively as follows : 1) Horizontal on the labial surface 2) $26^{\circ}$ diagonal direction on the lingual surface. Material property, geometry, and load condition of each model were inputted to the two dimensional ANSYS 4.4A finite element program : stresses and displacements were analyzed. Results were follows : 1. In the case of $130^{\circ}$ shoulder post and core, Maximum tensile and shear stresses were observed in the crown margin. 2. Maximum shear stress was about 29% reduced by contrabevel. 3. In the case of 1mm axial tooth structure, Maximum tensile stress observed in the dentin. 4. In the case of but joint of cervix, Maximum stress concentration was observed in the dentin by the inclined and horizontal force. 5. Horizontal force produced the extraordinary high stresses in dentin and supporting structures. 6. The amount of remaining tooth structure affected the level of stress significantly and it determined the location of stress concentration.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.774-780
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• 1999

The study of bond behavior between concrete and rebar has been performed for a long time. On this study, we tried to analysed variation of bond behaviors quantitatively with varying the strength of concrete. Bond stress which observed below the neutral surface of beam and at connecting part of beam and column is affected by various bond parameters. Resistance of deformed bars which embedded in concrete to the pullout force is divided 1) chemical adhesive force 2) frictional force 3) mechanical resistance of ribs to the concrete and these horizontal components of resistance is being bond strength. We selected the most common and typical variable which is concrete strength among various variables. So we used two kinds of concrete strength like as 25MPa(NSC) and 65MPa(HSC). Tension Test was performed to verify how bond behavior varied with two kinds of concrete strength. Concentration of bond stress was observed at load-end commonly in Tension Test of the initial load stage. At this stage stress distribution was almost coincident at each strength. As tension load added, this stress distribution had difference gradually and movement of pick point of bond stress to free-end and central section was observed. This tendency was observed at first and moving speed was more fast in NSC. At the preceeding result the reason of this phenomenon is considered to discretion of chemical adhesion and local failure of concrete around rebar in load-end direction. Especially, when concrete strength was increased 2.6 times in tension test, ultimate bond strength was increased 1.45 times. In most recent used building codes, bond strength is proportioned to sqare root of concrete compressive strength but comparison of normalized ultimate bond strength was considered that the higher concrete strength is, the lower safety factor of bond strength is in each strength if we use existing building codes. In Tension Test, in case of initial tensile force state, steel tensile stress of central cross section is not different greatly at each strength but tensile force increasing, that of central cross section in NSC was increased remarkably. Namely, tensile force which was shared in concrete in HSC was far greater than that of concrete in NSC at central section.

• 대한치과교정학회지
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• 제46권3호
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• pp.155-162
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• 2016

Objective: The aim of this study was to investigate whether labial tooth inclination and alveolar bone loss affect the moment per unit of force ($M_t/F$) in controlled tipping and consequent stresses on the periodontal ligament (PDL). Methods: Three-dimensional models (n = 20) of maxillary central incisors were created with different labial inclinations ($5^{\circ}$, $10^{\circ}$, $15^{\circ}$, and $20^{\circ}$) and different amounts of alveolar bone loss (0, 2, 4, and 6 mm). The $M_t/F$ necessary for controlled tipping ($M_t/F_{cont}$) and the principal stresses on the PDL were calculated for each model separately in a finite element analysis. Results: As labial inclination increased, $M_t/F_{cont}$ and the length of the moment arm decreased. In contrast, increased alveolar bone loss caused increases in $M_t/F_{cont}$ and the length of the moment arm. When $M_t/F$ was near $M_t/F_{cont}$, increases in Mt/F caused compressive stresses to move from a predominantly labial apical region to a palatal apical position, and tensile stresses in the labial area moved from a cervical position to a mid-root position. Although controlled tipping was applied to the incisors, increases in alveolar bone loss and labial tooth inclination caused increases in maximum compressive and tensile stresses at the root apices. Conclusions: Increases in alveolar bone loss and labial tooth inclination caused increases in stresses that might cause root resorption at the root apex, despite the application of controlled tipping to the incisors.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.487-490
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• 2004

In this paper, we investigated the characteristics of initiation and propagation behavior for fatigue crack observed by changing various shapes of initial crack and magnitudes of loading in modified compact tension shear(CTS) specimen subjected to shear loading. In the low-loading condition, the secondary fatigue crack was created in the notch root due to friction on the pre-crack face grew to a main crack. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Influenced by the shear loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. The propagation path of fatigue crack under the Mode II loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.302-307
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• 2004

This paper reviewed characteristics of fatigue crack behavior observed by changing various shapes of initial crack and magnitudes of loading in compact tension shear(CTS) specimen subjected to shear loading. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Meanwhile, the secondary fatigue crack in the low-loading condition which was created in the notch root due to friction on the pre-crack face grew to a main crack. Influenced by the mode II loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. Propagation path of fatigue crack under the shear loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.