• 한국지반공학회논문집
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• 제34권5호
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• pp.5-17
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• 2018

본 연구에서는 풍화암에 근입된 강관 매입말뚝의 안전율 제안을 위하여 정재하시험과 동재하시험을 수행하였다. 현장재하시험은 직경이 0.508, 0.457m 인 시험말뚝을 제작하여 정재하시험(14회)과 동재하시험(EOID 14회, Restrike 14회)을 실시하였다. 이때, 재하시험은 시험말뚝 시공완료 후 (1)초기동재하시험(EOID)을 수행하였으며, (2)시공완료 28일 후 정재하시험을 시행하였으며, (3)정재하시험 완료 후 15일 후에 재항타동재하시험(Restrike)을 실시하였다. 본 연구 결과 Davisson 판정법의 동재하시험을 이용한 지지력 산정 결과 정재하시험 대비 재항타동재하시험은 약 15% 낮게 나타났다. 정재하시험과 동재하시험의 지지력 분석을 통하여 안전율을 비교하였고, 최종적으로 동재하시험 안전율을 기존 2.0에서 1.75로 수정 제안하였다.

• 대한산업공학회지
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• 제4권2호
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• pp.49-58
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• 1978

The purpose of this study was to analyze the actual condition of curriculum composition by factor analysis, then to find out the peculiarity of each factor through factor loading. The method adopted here is to classify and arrange the curricula in accordance with the similarity of each subject, to put it into computer, and to get 16 factors whose eigenvalues are at least 1.00. Consequentely, before the orthogonal rotation 67% of the curricula which have the given factors and maximum factor loading were distributed from factor 1 to factor 4, and after orthogonal rotation 45% of the curricula were distribued.

• 대한기계학회논문집A
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• 제23권6호
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• pp.961-967
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• 1999

A model is constructed to evaluate the mode III stress intensity factor(SIF) for orthotropic three-layered material with a center crack subjected to uniform anti-plane shear loading. A mixed boundary value problem is formulated by Fourier integral transform method and a Fredholm integral equation of the second kind is derived. The integral equation is numerically analyzed to evaluate the effects of the ratio of shear modulus, strength of each layer and crack length to layer thickness on the stress intensity factor.

• 대한기계학회논문집
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• 제19권1호
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• pp.170-180
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• 1995

A parallel crack in bonded dissimilar orthotropic planes under out-of-plane loading is analyzed. The problem is formulated by Fourier integral transforms, and reduced to a pair of dual integral equations. By solving the integral equations, the asymptotic stress and displacement fields near the crack tip are determined in closed form, from which the stress intensity factor and energy release rate are obtained. Discontinuity in the stress intensity factor as the distance ratio h/a of the parallel crack approaches zero is found, while the energy releas rate is shown to be continuous at h/a = 0. This information can immediately be used to generate the stress intensity factor for the parallel crack near the interface. By employing "the maximum energy release rate criterion", it could be shown in the case of no existing crack initially that the parallel crack is formed far from the interface for the more compliant material, while it is formed close to the interface for the stiffer material. material.

• Nuclear Engineering and Technology
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• 제38권3호
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• pp.277-284
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• 2006

In order to ensure the structural integrity of nuclear welded structures during design life, the fatigue life has to be evaluated by fatigue analysis procedures presented in technical codes such as ASME B&PV Code Section III. However, existing fatigue analysis procedures do not explicitly consider the presence of welded joints. A new fatigue analysis procedure based on a structural stress/fracture mechanics approach has been recently developed in order to reduce conservatism by erasing uncertainty in the analysis procedure. A recent review of fatigue crack growth data under various mean loading conditions using the structural stress/fracture mechanics approach, does not consider the mean loading effect, revealed some significant discrepancies in fatigue crack growth curves according to the mean loading conditions. In this paper, we propose the use of the stress intensity factor range ${\Delta}K$ characterized with loading ratio R effects in terms of the structural stress. We demonstrate the effectiveness in characterizing fatigue crack growth and S-N behavior using the well-known data. It was identified that the S-N data under high mean loading could be consolidated in a master S-N curve for welded joints.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.286-291
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• 2001

Most cracks in the structure occur under mixed mode loadings and those propagation depend on the stress ratio very much. So, it is necessary to study the fatigue behavior under mixed mode loading as stress ratio changes. In this paper, fatigue crack propagation behavior was investigated respectively at stress ratio 0.1, 0.3, 0.5, 0.7 and we change loading application angle to $0^{\circ},\;30^{\circ},\;60^{\circ}$ to apply various loading. mode. The mode I and II stress intensity factors of CTS specimen used in this study were calculated by displacement extrapolation method using FEM(ABAQUS). Using both the study through the experiment and the theoretical study through FEM analysis, we studied the relation between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress condition and given loading mode condition, we studied what the dominant factors of the crack propagation rate were at each case.

• Structural Engineering and Mechanics
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• 제17권5호
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• pp.627-639
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• 2004

The objective of this research was to evaluate the performance of metal-plate-connected truss joints subjected to cyclic loading conditions that simulated seismic events in the lives of the joints. We also investigated the duration of load factor for these joints. We tested tension splice joints and heel joints from a standard 9.2-m Fink truss constructed from $38-{\times}89-mm$ Douglas-fir lumber: 10 tension splice joints for static condition and for each of 6 cyclic loading conditions (70 joints total) and 10 heel joints for static condition and for each of 3 cyclic loading conditions (40 joints total). We evaluated results by comparing the strengths of the control group (static) with those of the cyclic loading groups. None of the cyclic loading conditions showed any strength degradation; however, there was significant stiffness degradation for both types of joint. The results of this research show that the current duration of load factor of 1.6 for earthquake loading is adequate for these joints.

• 한국정밀공학회지
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• 제22권4호
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• pp.159-166
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• 2005

This study deals with the correction of gear tooth profile error by finish roll forming. First, we experimentally confirmed that the tooth profile error is a synthesis of the concave error and the pressure angle error. Since various types of tooth profile errors appear in the experiments, we introduced evaluation parameters for rolling gears to objectively evaluate profile quality. Using these evaluation parameters, we clarified the relationship among the tooth profile error, the addendum modification factor (A. M. factor), and the tool loading force. We verified the character of concave error, pressure angle error, tool loading force and number of cycles of finish roll forming by using a forced displacement method. This study makes clear that tool loading force and number of cycles of finish roll forming are very important factors that affect involute tooth profile error. The results of the experiment and analysis show that the proposed method reduces concave and pressure angle errors.

• The Journal of Korean Physical Therapy
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• 제19권5호
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• pp.51-63
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• 2007

Diabetic foot ulcers result from abnormal mechanical loading of the foot, such as repetitive pressure applied to the plantar aspect of the foot while walking. Diabetic peripheral neuropathy causes changes in foot structure, affecting foot function and subsequently leading to increased plantar foot pressure, which is a predictive risk factor for the development of diabetic foot ulceration. To early identify the insensitive foot makes it possible to prevent diabetic foot ulceration and to protect the foot at risk from abnormal biomechanical loading. Abnormal foot pressures can be reduced using several different approaches, including callus debridement, prescription of special footwear, foot orthosis. injection of liquid silicone, Achilles tendon lengthening, and so forth. Off-loading of the diabetic wound is a key factor to successful wound healing as it is associated with reduced inflammatory and accelerated repair processes. Pressure relief can be achieved using various off-loading modalities including accommodative dressing, walking splints, ankle-foot orthosis, total contact cast, and removable and irremovable cast walkers.

• 한국지반공학회논문집
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• 제30권3호
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• pp.59-72
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• 2014

모래지반 표면에 위치한 강체 원형기초를 대상으로 수치해석을 통하여 수직-모멘트 조합하중 조건에서의 지지력을 구하였다. 지반은 Mohr-Coulomb 소성모델을 이용하여 모델링하였으며 관련흐름법칙을 적용하였고, 거친 기초 바닥면 조건에 대하여 검토하였다. 적은 수의 해석으로 조합하중 상관도를 산출할 수 있는 swipe 재하 방법과 통상적인 재하실험에서 적용되는 probe 재하 방법을 적용하여 비교한 결과, 두 방법은 유사한 결과를 나타내었다. 모멘트하중을 고려하기 위하여 전통적으로 사용되는 유효폭 및 유효면적 개념을 사용한 결과와 편심계수($e_{\gamma}$)를 사용한 방법들을 비교하였으며, 기존의 제안식들과 수치모델링으로 구해진 본 연구의 결과를 비교하였다. 수직-모멘트 조합하중 지지력의 내부마찰각에 따른 변화는 미미한 것으로 나타났으며, 유효폭 개념은 편심계수의 형태로 변환하여 원형기초에도 그대로 적용이 가능한 것으로 나타났다. 본 연구의 수치모델링 결과는 기존의 실험에 기반한 결과들에 비해 다소 작은 값을 주는 것으로 나타났으며, 편심 및 모멘트하중이 증가할수록 그 차이는 증가하였다. 수치모델링과 실험 결과가 차이를 나타내는 요인과 향후 연구 방향에 대하여 고찰하였다.