• 한국전산구조공학회논문집
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• 제17권4호
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• pp.433-442
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• 2004

본 논문에서는 이웃한 빌딩의 기초가 서로 상이한 경우, 구조물과 지반의 상호작용에 대한 지진응답해석을 하였다. 세 가지 시스템에 대한 두 가지 모델에 대하여 연구하였다. 첫째 모델의 경우에는 빌딩은 프레임모델로 지반은 그리드모델로 설정하였고, 둘째 모델의 경우에는 구조물과 지반을 평면응력과 평면변형률로 모델화하였다. 또한 변형된 관성모멘트는 지반의 탄성모듈과 함께 구조물의 단면력에 영향을 미치므로 함께 고려되었다. 근사해석으로는 유한요소법과 응답스펙트럼이 적용되었으며 제시된 예를 통하여 안전성을 논증하였다.

• Elastomers and Composites
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• 제47권3호
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• pp.201-209
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• 2012

그로멧은 자동차의 고무부품들 중의 하나로 에틸렌 프로필렌 고무로 구성되어 있으며, 고무의 비선형 초탄성 성질은 고무제품의 거동을 예측하는데 중요하다. 본 논문에서는, 일축인장시험과 이축인장시험을 통하여 안정된 응력-변형률 관계를 구하고 그로멧에 대한 유한요소해석을 수행하였고, 수명예측을 위한 노화시험을 소개하였다.

• Geomechanics and Engineering
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• 제6권6호
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• pp.531-544
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• 2014

Studies of earthquakes over the last 50 years and the examination of dynamic soil behavior reveal that soil behavior is highly nonlinear and hysteretic even at small strains. Nonlinear behavior of soils during a seismic event has a predominant role in current site response analysis approaches. Common approaches to ground response analysis include linear, equivalent linear and nonlinear methods. These methods of ground response analysis may also be categorized into time domain and frequency domain concepts. Simplicity in developing analytical relations and accuracy in considering soils' dynamic properties dependency to loading frequency are benefits of frequency domain analysis. On the other hand, nonlinear methods are complicated and time consuming mainly because of their step by step integrations in time intervals. In part Ι of this paper, governing equations for seismic response analysis of surcharged and layered soils were developed using fundamental of wave propagation theory based on transfer function and boundary conditions. In this part, nonlinear seismic ground response is analyzed using extended HFTD method. The extended HFTD method benefits Newton-Raphson procedure which applies regular iterations and follows soils' fundamental stress-strain curve until convergence is achieved. The nonlinear HFTD approach developed here are applied to some examples presented in this part of the paper. Case studies are carried in which effects of some influencing parameters on the response are investigated. Results show that the current approach is sufficiently accurate, efficient, and fast converging. Discussions on the results obtained are presented throughout this part of the paper.

• Geomechanics and Engineering
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• 제23권6호
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• pp.503-512
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• 2020

Mining activities focus on the production of mineral resources for energy generation and raw material requirements worldwide and it is a known fact that shallow reserves become scarce. For this reason, exploration of new resources proceeds consistently to meet the increasing energy and raw material demand of industrial activities. Rock mechanics has a vital role in underground mining and surface mining. Devices and instruments used in laboratory testing to determine rock mechanics related parameters might have limited sensing capability of the failure behavior. However, methodologies such as, thermal cameras, digital speckle correlation method and acoustic emission might enable to investigate the initial crack formation in detail. Regarding this, in this study, thermographic analysis was performed to analyze the failure behaviors of different types of rock specimens during uniaxial compressive strength experiments. The energy dissipation profiles of different types of rocks were characterized by the temperature difference recorded with an infrared thermal camera during experiments. The temperature increase at the failure moment was detected as 4.45℃ and 9.58℃ for andesite and gneiss-schist specimens, respectively. Higher temperature increase was observed with respect to higher UCS value. Besides, a temperature decreases of about 0.5-0.6℃ was recorded during the experiments of the marble specimens. The temperature change on the specimen is related to release of radiation energy. As a result of the porosity tests, it was observed that increase in the porosity rate from 5.65% to 20.97% can be associated to higher radiation energy released, from 12.68 kJ to 297.18 kJ.

• Steel and Composite Structures
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• 제48권3호
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• pp.335-351
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• 2023

This research studies the primary resonance and nonlinear vibratory responses of multilayer functionally graded shallow (MFGS) shells under external excitations. The shells considered with functionally graded porous (FGP) core and resting on two types of nonlinear viscoelastic foundations (NVEF) governed by either a linear model with two parameters of Winkler and Pasternak foundations or a nonlinear model of hardening/softening cubic stiffness augmented by a Kelvin-Voigt viscoelastic model. The shells considered have three layers, sandwiched by functionally graded (FG), FGP, and FG materials. To investigate the influence of various porosity distributions, two types of FGP middle layer cores are considered. With the first-order shear deformation theory (FSDT), Hooke's law, and von-Kármán equation, the stress-strain relations for the MFGS shells with FGP core are developed. The governing equations of the shells are consequently derived. For the sake of higher accuracy and reliability, the P-T method is implemented in numerically analyzing the vibration, and the method of multiple scales (MMS) as one of the perturbation methods is used to investigate the primary resonance. The results of the present research are verified with the results available in the literature. The analytical results are compared with the P-T method. The influences of material, geometry, and nonlinear viscoelastic foundation parameters on the responses of the shells are illustrated.

• 대한조선학회논문집
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• 제28권1호
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• pp.108-116
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• 1991

선용재료중(船用材料中)에는 정적하중(靜的荷重)에 의한 정적거동(靜的擧動)(응력-변형률관계)과 반복하중(反復荷重)에 의한 반복거동(反復擧動)(응력진폭-변형률진폭관계)이 상이(相異)하게 되는 경우가 많다. 특히 탄소성(彈塑性) 응력집중부(應力集中部)에서 진전(進展)하는 초기의 짧은 피로균열(疲勞龜裂)은 재료(材料)의 반복거동(反復擧動)에 크게 의존하여 성장하므로 재료(材料)의 정적(靜的) 및 반복거동(反復擧動)의 비교, 검토가 요구된다. 본 연구에서는 2종류의 철강재료(鐵鋼材料)(SS41, HT80)와 5종류의 Al합금(合金)(A5083-O, A6N01-T5, A7N01-T4, A7016-T6, A7178-T6)에 대하여 정적(靜的) 및 반복하중(反復荷重)에 의한 재료(材料)의 응력-변형율(應力-變形率) 관계(關係)를 비교, 검토하였고, 각(各) 재료상수(材料常數)를 구하였다. 또한 응력집중부(應力集中部)에 일정 진폭의 반복하중(反復荷重)이 작용(作用)하여 탄소성(彈塑性) 변형(變形)할 때 그 선단(先端)의 응력(應力)과 변형률(變形率) 진폭(振幅)의 변화(變化)에 미치는 재료(材料)의 반복(反復) 경화특성(硬化特性)의 영향에 대하여 Neuber법칙(法則)과 중앙(中央)노치재(材의) 실험(實驗)에 의하여 고찰(考察을 행하였다.

• The Plant Pathology Journal
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• 제16권1호
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• pp.25-28
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• 2000

The effect of ionic osmotic potential (Ψ$\pi$), and matric potential (Ψm) in the range of -0.2 to -4.0 Mpa on mycelial growth of three species of Pleurotus (P.florida, P.ostrenatus and P.safor-caju) were determined over a range of temperature (15-3$0^{\circ}C$) on a 2% malt extract agar medium and compared with the Ψ$\pi$ effect on growth of two strains of Trichoderma green mould. With the ionic solute KCl, optimun Ψ$\pi$for growth was -0.2 MPa for P.floreda and in the range of -0.2 to -0.5 MPa, with slight growth at -3.0 MPa and with nogrowth at -4.0 MPa. Of the species of Pleurotus, P.florida grew signigicantly slower than the other two species. Growt of the species of Pleurocus was significantly slower when water potential (Ψ$\omega$) was modified matrically with polyethylene glycol (PEG) 8000 then osmotically with KCl. They were also more sensitive to changes in Ψm than Ψ$\pi$The optimum Ψm of the Pleurotus was -0.5 Ψm, with no growth below -3.0 MPa. Of the species of Pleurotus, P.florida was most sensitive and P.sajor-caju was more tolerent to lowered Ψ$\pi$,but P.sajor-caju was most sensitive to lowered Ψm. The growth rate of the Trichoderma green mould strains was much faster than that observed for the Pleurotus spp. Optimum growth for bot strains of Trichoderma was in the range of -0.2 to -0.5 MPa. Strain CNU 503 was more tolerant to water stress than strain CNU 501. Both strains were able to grow up to 30% of optimum growth at -4.0 MPa at 25-3$0^{\circ}C$.

• 전산구조공학
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• 제7권3호
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• pp.133-141
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• 1994

강도활용을 극대화한 볼트의 소성역체결시 볼트의 항복은 볼트에 발생한 인장응력과 너트 나사산과의 접촉면에서 오는 마찰토오크에 의한 전단응력과의 조합에 의한 영향을 받는다. 볼트는 최소단면적인 나사부중 너트와 물리지 않은 여우나사부에서 먼저 항복을 일으킨다. 볼트재료는 대체로 항복과 더불어 소성경화를 보이며 그 정도는 고강도재료에서 인장강도의 10%정도이다. 본 연구에서는 소성역체결시의 거동해석을 변형도증분이론에 의거 해석하였다. 항복은 최소단명이 원통의 표면에서 시작되며 이를 두께가 얇은 원통으로 취급하였다. 항복의 전파는 이들 얇은 원통이 체결이 진행됨에 따라 순차적으로 항복에 이르는 것으로 보고 이 얇은 원통들을 항복시키는데 필요한 축력과 토오크를 합하여 체결종료시의 볼트축력과 (나사면마찰) 토오크로 하였다. M10미터 가는 나사를 계산과 실험에 사용하였다. 축력과 마찰토오크의 마찰계수에 대한 변화관계를 보여주는 그래프와 더불어 실험에서 사용한 볼트의 설계보조 선도를 제시하였다. 이 설계보조용 선도는 실험실에서 얻어진 토오크계수와 마찰계수와의 관계를 그린 것으로 윤활, 포면처리등 현장조건에 따라 달라진 마찰계수를 적절히 취급하는데 효과적으로 활용이 가능하다.

• 한국염색가공학회지
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• 제7권4호
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• pp.25-32
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• 1995

This study was carried out to examine the influences of fatigue and perspiration on the deterioration of chrome leather for shoes. The samples were treated with acidic and alkaline artificial perspirations and applied cyclic tensile stress, and the elastic recovery from fatigue strain, tensile strength and elongation, stiffness etc. by regions and directions were determined. The physical properties generally indicate considerable difference by regions and directions due to the thickness, entangling state, and arrangement direction of fiber buldles within the leather. By the treatment of artificial perspirations, the length, weight, strength, elastic recovery from fatigue of the lether are decreased and the thicknes, elongation, and stiffness are increased; and their extents by the alkaline perspiration are higher than those by the acidic one. The elastic recovery from fatigue of samples are decreased with increasing fatigue cylcle; and indicate regressive relations against the logarithm of the elapsed time, and the means of regression coefficients are 2.73 > 2.55 > 2.22 for samples treated by the acidic perspiration, untreated, and treated by the alkaline perspiration, respectively. The tensile strength is decreased and elogation is increased by fatigue, but the changes are diminished likely due to a rearrangment of fiber bundles with increasing fatigue cycle. And the samples become a little flexible immediately after fatigue; but stiffen again with elastic recovery from fatigue strain, consequently for some cases their stiffness after recovery are rather greater than those before fatigre.

• 지질공학
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• 제32권4호
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• pp.597-610
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• 2022

중간주응력을 고려한 마찰재료의 파괴거동에 대한 확고한 이해는 대심도 보어홀 안정성 및 단층해석 등과 관련된 현장 적용의 고도화를 위한 필수적인 과정이다. 본 연구는 진삼축압축 조건을 물리적으로 구현하는 장비를 설계·제작하였으며 마찰재료로 제작된 석고 시료에 대한 진삼축압축시험을 통하여 재료의 파괴거동 특성을 논의하고 삼차원파괴함수의 적용성을 검토하였다. 진삼축압축시험을 위한 석고 재료는 52(w) × 52(l) × 104(h) mm의 직육면체 시료로 성형하였으며 다양한 조합의 𝜎₃, 𝜎₂의 조건으로 총 24회의 진삼축압축시험이 수행되었다. 또한, 삼차원 파괴기준식의 파라미터로 사용되는 석고의 강도정수 측정을 위하여 전통적인 일축압축시험 및 삼축압축시험이 수행되었다. 석고 재료의 응력-변형 특성은 중간주응력과 최소주응력의 차이가 클수록 취성거동이 더욱 강하게 나타났으며, 시료의 강도 및 변형은 중간주응력의 변화를 반영하는 것으로 평가되었다. 주응력 좌표계에서 시험 데이터에 대한 비선형 다중회귀분석을 수행한 결과 수정 Wiebols-Cook 파괴기준 및 수정 Lade 파괴기준이 석고 시료에 대한 삼차원 파괴기준으로 가장 적합하였다.