• Advances in Computational Design
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• 제7권4호
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• pp.371-393
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• 2022

This paper presents a three-dimensional flexible pavement simulated in ANSYS subjected to moving vehicular load on the surface of the pavement typical for the road section in Nepal. The adopted finite element (FE) model of pavement is validated with the classical theoretical formulations for half-space pavement. The validated model is further utilized to understand the damping and dynamic response of the pavement. Transient analysis of the developed FE model is done to understand the time varying response of the pavement under a moving vehicle. The material properties of pavement considered in the analysis is taken from typical road section used in Nepal. The response quantities of pavement with nonlinear viscoelastic asphalt layer are found significantly higher compared to the elastic pavement counterpart. The structural responses of the pavement decrease with increase in the vehicle speed due to less contact time between the tires of the vehicle and the road pavement.

• 한국자동차공학회논문집
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• 제24권5호
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• pp.596-604
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• 2016

In this study, we used a stochastic approach for guaranteeing the reliability and robustness of the performance with regard to the design of polymer components, while taking into consideration the degradation properties and operating conditions in automobiles. Creep and tensile tests were performed for obtaining degradation properties. The Prony series, which described the viscoelastic models, were calculated to use the creep data by the Maxwell fluid model. We obtained the stress data from the frequency response analysis of the polymer components while considering the degradation properties. Limit state functions are generated by using these data. Reliability assessments are conducted under the variation of the degradation properties and area of frequency at peak response. For this study, the input parameters are assumed to be a normal distribution, and the reliability under the yield stress criteria is evaluated by using the Monte Carlo Simulation. As a result, the reliabilities, according to the three types of polymer materials in automotive components, are compared to each other and suggested the applicable possibility of polymeric materials in automobiles.

• 한국정밀공학회지
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• 제17권3호
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• pp.184-191
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• 2000

Properties of pad are investigated to find the relationship between the chemical mechanical polishing(CMP) results, such as material removal rate and within wafer non-uniformity(WIWNU), and its properties. Polishing pressure is considered as important factors to affect the results, so behavior of ordinary polymer is studied to define the polishing result affecting properties of pad. Experimental setup is devised to identify the behavior of pad and several different pads are used in chemical mechanical polishing experiments to verify the correlations between pad properties and polishing results. The results indicate that the viscoelastic properties of pad had relationships with the polishing results, and shows correlation between suggested properties of pad and polishing result.

• Korean Chemical Engineering Research
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• 제43권3호
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• pp.401-406
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• 2005

본 연구에서는 다중벽 탄소나노튜브의 화학적 표면처리가 에폭시 매트릭스 복합재료의 유리전이온도, 열안정성 그리고 동적 점탄성거동에 미치는 영향을 고찰하기 위하여 시차주사열량계(DSC), 열중량분석기(TGA) 그리고 동적 기계적 분석기(DMA)를 통하여 각각 측정하였다. 탄소나노튜브의 표면처리는 35 wt％의 $H_3PO_4$(A-MWNTs) 혹은 35 wt％ KOH(B-MWNTs) 용액으로 화학적 표면처리를 하였으며, 표면처리 후 표면특성 변화는 pH, 표면 산 및 염기도, 적외선 분광법(FT-IR)과 자외선 광전자 스펙트럼(XPS) 분석을 통하여 알아보았다. 그 결과로서, 산-염기 상호반응에 의한 각각의 표면처리는 탄소나노튜브의 표면특성 및 화학적 조성 변화를 가져오며, 산처리한 MWNTs/에폭시 복합재료의 경우가 염기처리 및 미처리 시편과 비교하여 열안정성 및 동적 점탄성 특성에 있어서 탄소나노튜브 표면에 도입된 산성 관능기 그룹의 영향으로 큰 값을 나타내었다. 이는 염기성을 가지는 에폭시 수지와 산성을 가지는 탄소나노튜브와의 산-염기 및 수소결합에 의한 계면결합력의 향상 때문이라 생각된다.

• 폴리머
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• 제25권3호
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• pp.406-413
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• 2001

고분자의 블렌드는 새로운 성질을 가지는 재료의 제조를 위한 하나의 방법으로 제시되고 있다. 그러나 대부분의 재료는 재료사이의 점탄성, 표면에너지 그리고 상호결합력의 차이로 인하여 비상용성을 지니며, 이로 인하여 블렌드물은 예상되는 물성을 나타내지 못하는 경우가 있다. 실리콘 고무는 우수한 내열성과 전기적 성질을 가지며, ethylene propylene diene monomer (EPDM) 고무는 우수한 기계적 물성을 지니고 있다. 본 실험에서는 실리콘과 EPDM 고무의 블렌드를 통한 전기적 성질과 기계적 물성이 우수한 새로운 기능성 재료의 개발에 목적을 두었다.

• Elastomers and Composites
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• 제23권4호
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• pp.299-307
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• 1988

The mono-, di- and polysulfidic concentrations of the carbon black filled NR and SBR vucanizates which have different cure systems were determined. The n-decane was used as a swelling solvent. The propane-2-thiol and hexane thiol were used as specific chemical probes to cleavage the chemical crosslinks such as di- and polysulfide. In order to understand the effect of crosslink structure on the physical properties of vulcanizates, the tensile properties, fatigue failure, heat build up, compression set and viscoelastic properties were measured. From the results, the significant relationships between crosslink sturctures and physical properties, especially a gins resistance were obtained. Therefore, the better performances of the product can be satisfied by using the interpretations and approaches in this study.

• 폴리머
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• 제34권3호
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• pp.226-236
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• 2010

UV조사에 의한 공중합반응을 통해 PDP의 방열패드용 무용제형 아크릴계 점착제를 제조하고 이때 도입되는 공단량체의 곁사슬의 화학적 구조와 가교제의 종류에 따른 점착제의 젖음성을 온도별로 조사하였다. 또한, 동일 조건에서 점착제의 초기 접착력 및 박리강도와 주파수 변화에 따른 점착제의 점탄성 거동 간의 상관관계를 확인하였다. 공단량체의 곁사슬의 길이가 짧을수록 넓은 온도범위에서 우수한 젖음성과 점착 물성을 보였으며 경화제로는 di(ethylene glycol) dimethylacrylate(DEGDMA)를 사용한 계가 우수한 박리 에너지를 보였는데, 이것은 유리전이온도와 점탄성거동의 차이에 기인하는 것으로 판단된다.

• Elastomers and Composites
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• 제39권1호
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• pp.51-60
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• 2004

본 연구에서는 organoclay를 혼합한 NR/BR blend의 가황특성, 동적점탄성 및 기계적 물성을 carbon black 및 silica를 함유한 배합고무와 비교 평가하였다. Solution 혼합법을 이용함으로써 광범위한 나노 복합체를 제조할 수 있었으며, 충전제의 함량은 10phr로 고정하였다. XRD 실험으로 clay의 삽입 및 박리정도를 측정하였다. 통상적인 혼합법을 이용할 경우 clay의 박리 또는 삽입정도가 미약한 반면 solution 혼합법을 이용할 경우 광범위한 박리형태의 clay 배합고무를 얻을 수 있음을 확인하였다. Clay 배합고무는 carbon black 및 silica를 함유한 배합고무에 비해 높은 tan ${\delta}$값을 나타내며, solution 혼합법을 이용할 경우 통상적인 혼합법에 의해 제조된 clay 배합고무에 비해 우수한 기계적 물성을 가짐을 확인할 수 있었다.

• Journal of Biosystems Engineering
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• 제18권1호
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• pp.30-36
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• 1993

Cucumbers being living biological materials are generally vulnerable to external forces, especially, bending force during the processes, because they have usually longish shape. Understanding the mechanical and viscoelastic properties of cucumber is important to analyze various characteristics which might be helpful in determining design parameters for the processing equipment such as sorting, packaging and transporting machine. The objectives of this study were to determine ultimate bending strength, deflections, and hysteresis losses for the cucumbers from the bending tests. Within the range of loading rate from 20 to 100mm/min, the ultimate bending strength of the cucumber samples were 525-630kPa at the Gyeousalicheongjang and the Baekdadagi, and 476~618kPa at the Cheongjangmadi, respectively, but the ultimate bending deflection ratio of the Cheongjangmadi showed the highest value among the tested samples. The effect of loading rate on the physical properties of the cucumber was relatively significant, all considered physical properties and degree of elasticity of the cucumber increased with the loading rate, but the hysteresis loss decreased with it.

• 대한가정학회지
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• 제26권3호
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• pp.93-102
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• 1988

Rheological properties of cowpea and mung bean starch gels and pastes were investigated and compared with Instron Universal Testing machine and Brabender Viscometer. As the result of puncture test of gels, yield point force of mung bean starch gel was higher than that of cowpea starch gel. Compression coefficient of cowpea starch gel calculated by Bourne's equation was lower than that of mung bean starch gel. the stress relaxation test showed that viscoelastic properties of cowpea and mung bean starch gels may be represented by six element Maxwell model consisting of three Maxwell element in parallel. Cowpea and mung bean starch pastes showed bingham pseudoplastic behavior in 3, 5, 6, 7 and 8%. The consistency index in 7∼8% of cowpea starch paste were lower than those of mung bean starch paste. concentration dependence on consistency index and yield stress in mung bean starch were higher than those of cowpea starch. The yield stress of starch pastes was significantly correlated with yield point force by puncture test (r=0.996).