• Geomechanics and Engineering
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• 제29권2호
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• pp.193-205
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• 2022

The face stability of shield tunnelling is the most important control index for safety risk management. Based on the reliability of the transparent clay (TC) model test, a series of TC model tests under different buried depth were conducted to investigate the progressive failure mechanism of tunnel face. The support pressure was divided into the rapid descent stage, the slow descent stage and the basically stable stage with company of the local failure and integral failure in the internal of the soil during the failure process. The relationship between the support pressure and the soil movement characteristics of each failure stage was defined. The failure occurred from the soil in front of the tunnel face and propagated as the slip zone and the loose zone. The fitted formulas were proposed for the calculation of the failure process. The failure mode in clay was specified as the basin shape with an inverted trapezoid shape for shallow buried and appeared as the basin shape with a teardrop-like shape in deep case. The implications of these findings could help in the safety risk management of the underground construction.

• 한국지반공학회지:지반
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• 제12권3호
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• pp.49-62
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• 1996

인발시험은 보강토 구조물의 설계에 있어 보강재와 흙사이의 강도 정수를 결정하는데 사용된다. 그러나 이 시험의 해석시 보강재를 따라 발생하는 전단강도가 일정한 것으로 가정하는데 이는 인발시험중 흙과 보강재 사이의 점진성 전단으로 인해 흙과 보강재의 전단-변위 관계 계산시 오류가 발생하게 된다. 구과 보강재 사이의 shear stiffness계산시 점진성전단의 영향을 평가하기 위하여 유한요소법으로 인발시헙을 해석하였다. 흙과 보강재는 선형과 비선형거동으로 채석하였고 shear stiffnss는 일반적인 방법으로 계산하였는데 수정된 shear stiffness와는 많은 차이가 있었으며 그 차이로 인해 유한요소해석의 결과가 달라지게 된다. 본 논문에서는 유한요소해석결과와 시험치를 비교 분석하였으며 개선된 인발시험 해극방법에 대하여 논하였다.

• 한국자동차공학회논문집
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• 제18권3호
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• pp.149-155
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• 2010

Currently various safety tests are being performed in many countries with growing interest in vehicle safety. However the vehicles which have good safety performance in these tests could not secure the good performance in real car to car accident. So new test protocol using progressive deformable barrier (PDB) was proposed by EEVC in Europe, NHTSA in USA and some vehicle manufacturers, etc. The target of PDB test is to control partner protection in addition to self-protection on the same test. The proposal is to update current ECE R.94 frontal ODB test. So barrier, impact speed, overlap are changed to avoid bottoming-out in the test configuration. In this paper 3 different tests (R.94, EuroNCAP and PDB test) were carried out using current production vehicles with same structure. The results of these tests were compared to understand PDB test. As a result PDB test shows the highest vehicle deceleration and dummy injury because PDB offers a progressive increase in stiffness in depth and height. However vehicle intrusion was affected with rather test velocity than stiffness of deformable barrier. PDB deformation data is used for partner protection assessment using PDB software and it shows that the test vehicle is rather not aggressive.

• Archives of Plastic Surgery
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• 제39권6호
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• pp.659-662
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• 2012

Progressive facial hemiatrophy, also known as Parry-Romberg syndrome, is a progressive and self-limited deformation of the subcutaneous tissue volume on one side of the face that creates craniofacial asymmetry. We present the case of a patient with a five-year history of progressive right facial hemiatrophy, who underwent facial volumetric restoration using cell-assisted lipotransfer (CAL), which consists of an autologous fat graft enriched with adipose-derived stem cells (ASCs) extracted from the same patient. ASCs have the capacity to differentiate into adipocytes. They also promote angiogenesis, release angiogenic growth factors, and some can survive as stem cells. The use of autologous fat as a filler in soft tissue atrophy has been satisfactory in patients with mild and moderate Parry-Romberg syndrome. Currently, CAL has showed promising results in the long term by decreasing the rate of fat reabsorption. The permanence and stability of the graft in all the injected areas has showed that autologous fat grafts enriched with stem cells could be a promising technique for the correction of defects caused by this syndrome.

• Composites Research
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• 제12권5호
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• pp.1-11
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• 1999

본 연구는 단섬유보강 금속복합재료의 피로 및 주기적 거동에 관한 연구로서, 가압용침법을 이용하여 제조된 Al6061과 이를 기지금속으로 사용한 단섬유보강 Al/$Al_2O_3$-15% 복합재료의 주기적변형(cyclic deformation)과 피로거동(fatigue behavior)에 대해서 실험적으로 고찰하였다. Al/$Al_2O_3$ 복합재로의 피로강도는 210MPa로 나타났고 기지금속은 170MPa로 나타났다. 영구소성변형에 의한 합변위는 피로수명 초기 5%이내에서 대부분 발생하며 파단시의 합변위는 복합재료와 기지금속 모두 축적된 소성변형으로 인하여 인장시험에서의 연신율에 비해 작은 값을 가진다. 금속복합재료의 주기적 변위는 보강재가 전위 전파의 저지역할을 함으로써 기지금속에 비하여 다소 감소하는 것으로 나타났다. 파면관찰결과 기지금속의 경우 금속복합재료에 비해 전체 시험편 단면에서 넓은 영역에서 균열전파 형태를 관찰할 수 있었으며, 또한 금속복합재료의 파면에서는 연속적인 피로하중에 의한 기지금속과 보강재간의 분리(debonding)등의 결과로 보강재가 뽑혀나간 흔적이 관찰되고 있다.

• Geomechanics and Engineering
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• 제12권4호
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• pp.561-577
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• 2017

Vast parts of the east of Tabriz city have been covered by Baghmisheh formation marls. These marls can be classified into three types based on their color as identified in yellow, green, and gray marls. Many high-rise buildings and other projects were founded and now is constructing on these marls. Baghmisheh formation marls are classified as stiff soil to very weak rock, therefore they undergo considerable consolidation settlement under foundation loads. This study presents the physical properties and consolidation behavior of these marls. According to the XRD tests, major clay minerals of marls are Illite, Kaolinite, Montmorillonite and Chloride. Uniaxial compressive strength are 100-250, 300-480 and 500-560 kPa for yellow, green and gray marls, respectively. Consolidation and creep behavior of Baghmisheh marls investigated by using of one dimensional consolidation apparatus under stress level up to 5 MPa. The results indicate that yellow marls have high compressibility, settlement and deformation modules. Green marls have an intermediate compressibility and settlement and while gray marls have low compressibility and settlement and from the foundation point of view have high stability. According to the creep test results, all types of marls have not been entered to progressive creep phase up to pressure 5 MPa.

• 대한조선학회논문집
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• 제30권3호
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• pp.100-115
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• 1993

본 논문에서는 구조전체의 최종붕괴강도에 대한 국부 구성부재의 과도인장변형효과를 고려하기 위하여 기존의 이상화구조요소들, 즉 이상화 보-기동요소, 이상화 판요소 및 이상화 보강판요소의 적용범위를 확장하며, 이를 위해 간이 역학적모델을 제시한다. Leander급 Frigate함의 1/3 축척 선각구조모형에 대해 Dow가 수행한 최종 종강도실험결과와 본 해석결과를 비교한 결과, 압축에 의한 구조부재의 파손 뿐만아니라 과도인장변형에 의한 파손도 구조전체적인 붕괴거동, 특히 붕괴후 거동에 크게 영향을 미침을 알 수 있었다.

• Design & Manufacturing
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• 제15권4호
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• pp.51-56
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• 2021

Piercing is the process of shearing a circular hole in sheet metal, whose high shear force makes it difficult to secure the durability of tools. In addition, uneven clearance between tools due to poor alignment of the piercing punch causes accelerated die wear and breakage of the tool. This study reviewed the feasibility of in-situ determining alignment failure during the piercing process by analyzing the signal deviation of a bolt-type piezo sensor installed inside the tool whose alignment level was controlled. Finite element analysis was performed to select the optimal sensor location on the piercing tool for sensitive detection of process signals. A well-aligned piercing process results in uniform deformation in the circumferential direction, and shearing is completed at a stroke similar to the sheet thickness. Afterward, a sharp decrease in shear load is observed. The misaligned piecing punch leads to a gradual decrease in the load after the maximum shear load. This gradual decrease is due to the progressive shear deformation that proceeds in the circumferential direction after the initial crack occurs at the narrow clearance site. Therefore, analyzing the stroke at which the maximum shear load occurs and the load reduction rate after that could detect the misalignment of the piercing punch in real-time.

• 한국지반공학회논문집
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• 제19권6호
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• pp.189-206
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• 2003

터널시공 중, 터널자체의 안정성 확보와 주변지반 및 인접 구조물의 안정성 확보를 위한 체계화된 계측관리는 매우 중요한 사항이라고 할 수 있는데, 지반조건이 불리한 도심지 터널공사나 지반조건이 급격하고 빈번하게 변화하는 경우에 있어서는 그 중요성이 더욱 증대되는 것이 사실이다. 최근 오스트리아에서는, 임의 시점에 대한 절대변위를 계측하고 분석하는 기존의 방법 대신, Geodetic을 이용한 각 시공단계별 상대변위의 계측 및 분석방법이 널리 증가하고 있는데, 이를 통해 지반조건의 급격한 변화 예측 및 이에 상응하는 굴착방법과 지보방식의 변경등이 용이해지고 있다. 한편, 지반의 변위는 막장 굴착이 시공되기 이전부터 발행하기 시작하므로 막장 전방의 응력상태는 향후 변위 진행과정에 있어 매우 중요한 요소라 할 수 있다. 즉, 막장 전방의 강성이나 응력상태는 굴착 후의 장기적인 터널안정성 및 인접 구조물의 안정성 확보와 관련된 주요 변수라 할 수 있다. 본 논문에서는 이와 관련된 다양한 조건에 대한 3차원 변위해석을 실시하였으며, 그 결과를 통해 터널 굴착시의 수직변위 및 벡터회전, 막장면 변위 등의 변화를 살펴보았다.

• 자원환경지질
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• 제24권4호
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• pp.435-446
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• 1991

Ductile shear zones developed in Jurassic granites in the Yonggwang area show NE trend at the eastern part and nearly EW trend at the western part, respectively. Judged from shear sense indicators, they have resulted from dextral strike-slip movement. The intersection of both trends is thought to be due to the truncation and offset of NE shear zone Chonju Shear zone by the brittle Yonggwang fault which runs in near EW direction with sinistral movement sense. The simple shear deformation was predominate through the deformation in this ductile shear zone. Based on this deformation mechanism, the shear strain (${\gamma}$) estimated in domain 1 increases from 0.14 at the shear zone margin to 9.41 toward the center of shear zone. Total displacement obtained only from this measured section(JK 59 to JK14) appecars to be 1434.5 meters. The sequential development of microstructures can be divided into three stages; weakly-foliated, well-foliated and banded-foliated stages. In the weakly-foliated stage dislocation glide mechanism might be predominant. In the well-foliated stage grain boundary migration and progressive misorientation of subgrains was remarkable during dynamic recovery and recrystallization. In the banded-foliated stage grain boundary sliding and microfracturing mechanisms accompanied with crushing and cracking were marked. According to strain analysis from quartzites of the metasedimentary rocks, strain intensity (${\gamma}$) of the samples within the ductile shear zone ranges from 2.7 to 5.7, while that of the samples out of the ductile shear zone appears to be about 1.7.