• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술.기술논문발표회
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• pp.77-86
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• 2002

In this study we intended to investigate properties of cement mortar with recycled PET fiber, PE fiber, and PP fiber such as slump flow, compressive strength, tensile strength, and flexural strength. As results of experiment, several properties of specimen with recycled PET fiber were little low comparing those of specimen with PE fiber and PP fiber. But if we see from point of economy and recycle of industrial wastes, it has enough reason to be used. Compressive strength of specimen with recycled PET fiber at 56 days was about 10% higher, but tensile strength and flexural strength were lower than that of no-fiber.

• 한국건축시공학회지
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• 제2권4호
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• pp.113-122
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• 2002

In this study we intended to investigate properties of cement mortar with recycled PET fiber, PE fiber. and PP fiber such as slump flow, compressive strength, tensile strength, and flexural strength. At results of experiment. several properties of specimen with recycled PET fiber were little low comparing those of specimen with PE fiber and PP fiber. But if we see from point of economy and recycle of industrial wastes, it has enough reason to be used. Compressive strength of specimen with recycled PET fiber at 55 days was about 10% higher. but tensile strength and flexural strength were lower than that of no-fiber.

• 한국산학기술학회논문지
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• 제19권3호
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• pp.52-60
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• 2018

최근 자동차 산업에서는 연비향상 및 안전규제 강화에 따라 차량 경량화가 필수적으로 요구됨에 따라 DP강(Dual Phase steel), CP강(Complex Phase steel), MS강(Martensitic Steel), TRIP강(Transformation Induced Plasticity steel), TWIP강(Twinning Induced Plasticity steel) 등과 같은 인장강도 700MPa 이상인 초고장력강(Ultra High Strength Steel)의 적용이 증가하고 있다. 초고장력강을 차체에 적용하기 위해서는 용접공정이 필수적이며, 원가 측면에서 유리한 전기저항점용접(Resistance Spot Welding, RSW)이 차체 용접에서 80%이상으로 가장 많이 적용되고 있다. 초고장력강은 강도향상을 위해 합금원소 함량을 늘이기 때문에 일반적으로 용접성이 열악한 것으로 알려져 있다. 이러한 초고장력강의 저항점용접의 경우 적정 용접조건 영역이 축소되고 용접부에서 계면파단 및 부분계면파단이 발생하는 것으로 보고되어 있어 결함 및 품질을 실시간으로 예측할 수 있는 용접품질 판정 연구가 활발히 진행되고 있다. 이에 따라 본 연구에서는 저항 점 용접을 수행할 때 검출되는 2차 회로 공정 변수를 이용하여 용접부의 동저항을 모니터링하고, 이 동저항 패턴에서 용접 품질 판단에 필요한 인자들을 추출하였다. 추출한 인자들을 상관분석하여 용접 품질과의 상관성을 파악하였으며, 상관성이 높은 인자들을 이용하여 회귀분석을 실시하였다. 이를 근거로 현장 적용이 가능한 회귀 모델을 제시하였다.

• 토지주택연구
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• 제10권4호
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• pp.51-59
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• 2019

The government is encouraging the notice of obligatory reclaimed asphalt as a result of the economic and social positioning of green growth to reduce the amount of waste resources and to solve natural resource problems by recycling continuously generated waste resources. However, it is necessary to develop application guideline for each application to apply reclaimed asphalt to the site because quality control of the reclaimed asphalt is difficult and the specifications are ambiguous as well. Therefore, in this study, the mix design, quality test, performance test, and finite element analysis about reclaimed Asphalt Pavement were conducted to develop application guideline for reclaimed hot asphalt. The mix design was carried out for the comparative general hot mix asphalt mixture, the reclaimed hot mix asphalt mixture using the additive, and the reclaimed hot mix asphalt mixture without the additive. Indirect tensile strength and tensile strength ratio tests were used to characterize the reclaimed hot mix asphalt mixture. Using the results of dynamic modulus test and FWD test for KPRP analysis and finite element analysis, the performance life was evaluated for general pavement and pavement using recycled aggregate. Finally, the life cycle cost analysis was used to compare and analyze the economics of reclaimed asphalt concrete pavement.

• 한국건설순환자원학회논문집
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• 제5권3호
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• pp.305-312
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• 2017

본 연구에서는 국내 화력발전소에서 발생되고 있는 산업부산물을 활용하여 아스팔트 콘크리트용 채움재를 개발 및 혼합물에 적용하여 함량에 따른 특성 및 소성변형 저항성에 미치는 영향을 관찰하였다. 실험결과 석탄회 기반 채움재를 사용할 경우 최적아스팔트함량(OAC)는 기존 채움재 대비 0.1% 낮은 값을 나타내었다. 도출된 최적아스팔트함량에서 채움재 함량에 따른 간접인장강도 및 인장강도비 측정 결과 함량 증가에 따라 높은 성능을 발현하였고, 2.0% 이상의 함량에서 국내 단체표준 품질관리 기준 각 0.8 이상과 0.75 이상을 만족하는 결과를 얻을 수 있었다. 동적안정도는 채움재 2.5%의 함량에서 가장 높은 저항성을 나타내었으며, 함량이 2.5%를 넘어설 때 오히려 성능발현이 저하되는 결과를 나타내었다. 과도한 채움재의 혼입은 상대적으로 아스팔트 함량이 감소되기 때문에 취성파괴를 유발할 수 있으므로 최적의 채움재/아스팔트 의 비율을 찾아 적용하는 방안이 필요할 것으로 판단된다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.347-347
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• 2005

• 한국정밀공학회지
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• 제16권10호
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• pp.141-151
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• 1999

The resistance Spot Welding is widely used in the field of assembling the plates. However we don't still have any satisfactory solution, which is non-destructive quality evaluation in real-time or on-line, against it. Moreover, even though the rate of welding under the condition of expulsion has been high until now, quality control of welding against expulsion hasn't still been established. In this paper, it was proposed on the quality assurance technique of resistance spot welding pieces using Neuro-Fuzzy algorithm. Four parameters from electrode separation signal in the case of non-expulsion, and dynamic resistance patterns in the case of expulsion are selected as fuzzy input parameters. The parameters consist of Fuzzy Inference System are determined through Neuro-Learning algorithm. And then, fuzzy Inference System is constructed. It was confirmed that the fuzzy inference values of strength have within ${\pm}$4% error specimen in comparison with real strength for the total strength range, and the specimen percent having within ${\pm}$1% error was 88.8%. According to KS(Korean Industrial Standard), tensile-shear strength limit for electric coated of zinc is 400kgf/mm2. Judging to the quality of welding is good or bad, according to this criterion and the results of inference, the probability of misjudgement that good quality is valuated into poor one was 0.43%, on contrary it was 2.59%. Finally, the proposed Neuro-Fuzzy Inference System can infer the tensile-shear strength of resistance spot welding pieces with high performance for all cases-non-expulsion and expulsion. And On-Line Welding Quality Inspection System will be realized sooner or later.

• 지질공학
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• 제25권2호
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• pp.237-250
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• 2015

지진 시에 지하구조물은 지상구조물보다 더욱 안전한 것으로 간주되어 왔으나, 1995년 고베지진 시 발생한 지하철터널의 피해 이후 지하구조물의 피해 사례가 점점 증가하고 있다. 본 논문에서는 풍화토로 되메움한 개착식 터널과 주변 지반의 지진 시 거동을 Mohr-Coulomb모델을 이용하여 수치해석을 수행하였다. 지반의 측면 경계조건, 인장강도, 최대지진가속도에 따른 개착식 터널과 주변 지반의 변위 및 터널 라이닝에 작용하는 응력을 예측하였다. 지반의 측면 경계조건(자유장 경계조건과 일반 경계조건)과 주변 지반의 인장강도의 변화에 따라 계산된 변위와 응력은 상당한 차이를 나타냈다. 좌우경계조건이 자유장 조건인 경우에는 지반의 잔류변형이 거의 발생하지 않았으나, 구속된 일반 조건인 경우에는 지진으로 인한 주변 및 기초 지반의 융기로 인한 잔류변형이 크게 발생하였다. 하지만 주변 및 기초 지반의 인장강도를 점착력의 100%로 가정하였을 경우 개착식 터널은 측면 경계조건이나 입력된 최대가속도에 관계없이 잔류변위는 1 cm 이내로 무시할 수준이다. 뿐만 아니라, 최대변위 발생 시 및 최종 단계에서 터널 라이닝에서 발생하는 응력은 모두 허용응력 이내이므로 안전한 것으로 판단된다. 동적 수치해석에서는 주변 지리적 조건을 고려하여 적절한 경계조건을 설정하고 인장강도와 같은 지반의 물성치를 정확하게 구하는 것이 매우 중요한 것으로 판단된다.

• 대한기계학회논문집A
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• 제27권8호
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• pp.1398-1408
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• 2003

Tensile and LCF(low cycle fatigue) tests were carried out in air at wide temperature range 20$^{\circ}C$-750$^{\circ}C$ and strain rates of 1${\times}$10$\^$-4//s-1${\times}$10$\^$-2/ to ascertain the influence of strain rate on tensile and LCF properties of prior cold worked 316L stainless steel, especially focused on the DSA(dynamic strain aging) regime. Dynamic strain aging induced the change of tensile properties such as strength and ductility in the temperature region 250$^{\circ}C$-600$^{\circ}C$ and this temperature region well coincided with the negative strain rate sensitivity regime. Cyclic stress response at all test conditions was characterized by the initial hardening during a few cycles, followed by gradual softening until final failure. Temperature and strain rate dependence on cyclic softening behavior appears to result from the change of the cyclic plastic deformation mechanism and DSA effect. The DSA regimes between tensile and LCF loading conditions in terms of the negative strain rate sensitivity were well consistent with each other. The drastic reduction in fatigue resistance at elevated temperature was observed, and it was attributed to the effects of oxidation, creep and dynamic strain aging or interactions among them. Especially, in the DSA regime, dynamic strain aging accelerated the reduction of fatigue resistance by enhancing crack initiation and propagation.

• 열처리공학회지
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• 제33권4호
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• pp.161-172
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• 2020

The tensile property of A5082 and A6060 aluminium wrought alloys was investigated, in terms of the strain rate sensitivity on alloy conditions by heat treatment and bake hardenability on pre-strain prior to strain ageing. The tensile test was carried out in a range of strain rate of 4.17 × 10^-5 s^-1 ~ 4.17 × 10^-5 s^-1 in room temperature and the nominal range of pre-strain was 3.0 ~ 10.5%. The tensile deformation of A5082 alloys is characterized as typical case of dynamic strain ageing with negative strain rate sensitivity for all conditions, and the tensile strength indicates a similar level regardless of alloy conditions, except only in full annealed condition. The stress-relief annealing on A6060 alloys can induce practical decrease in strength level of over approximately 100 MPa without any ductility loss, compared to as-rolled condition, while a full annealed and aged condition leads remarkable strengthening effect with the decrease of tensile elongation. Additionally, the bake hardenability of A5082 alloy by strain ageing indicates a negative dependence upon the increase of pre-strain, while A6060 alloy exhibits a positive sign even in low level relatively compared with conventional SPCC.