• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.167-168
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• 2010

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.413-417
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• 2004

Recent experiments have shown the 'size effects' in micro/nano scale. But the classical plasticity theories can not predict these size dependent deformation behaviors because their constitutive models have no characteristic material length scale. The Mechanism - based Strain Gradient(MSG) plasticity is proposed to analyze the non-uniform deformation behavior in micro/nano scale. The MSG plasticity is a multi-scale analysis connecting macro-scale deformation of the Statistically Stored Dislocation(SSD) and Geometrically Necessary Dislocation(GND) to the meso-scale deformation using the strain gradient. In this research we present a study of nano-indentation by the MSG plasticity. Using W. D. Nix and H. Gao s model, the analytic solution(including depth dependence of hardness) is obtained for the nano indentation , and furthermore it validated by the experiments.

• 터널과지하공간
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• 제27권3호
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• pp.172-184
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• 2017

동적 초미소 경도법의 압입시험, 하중-비하중 시험, 그리고 반복시험을 이용하여 심도별 대전화강암 내 광물들의 경도와 역학적 특성을 살펴보았다. 시험 결과 세 개 구간(Group-1, -2, -3)으로 광물 집단의 분류가 가능하였다. Martens 경도값은 세 가지 시험법 모두에서 41 m와 223 m 심도에 따른 차이가 크지 않았다. 그럼에도 불구하고, 그 크기는 반복시험<하중-비하중 시험<압입시험 순으로 나타났다. 광물 집단별 평균 Martens 경도, 탄성계수, indentation work 등을 고려해 볼때, 그들의 경계는 비교적 뚜렷하게 나타났다. 결론적으로 동적 초미소 경도법의 세 가지 형태 시험법을 이용함으로써 광물들에 대한 비교적 정확한 경도값을 얻을 수 있었다. 또한 하중-비하중 시험과 반복시험으로부터는 광물들의 탄성계수와 광물들의 탄성적-소성적 성질 특성 파악도 가능하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.144-149
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• 2004

Porous anodic alumina has been used widely for corrosion protection of aluminum surfaces or as dielectric material in micro-electronics applications. It exhibits a homogeneous morphology of parallel pores which can easily be controlled between 10 and 400nm. It has been applied as a template for fabrication of the nanometerscale composite. In this study, mechanical properties of the AAO structures are measured by the nano indentation method. Nano indentation technique is one of the most effective method to measure the mechanical properties of nano-structures. Basically, hardness and elastic modulus can be obtained by the nano-indentation. Using the nano-indentation method, we investigated the mechanical properties of the AAO structure with different size of nano-holes. In results, we find the hole effect that changes the mechanical properties as size of nano hole.

• 한국기계가공학회지
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• 제2권1호
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• pp.75-84
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• 2003

In this paper, a new nano/micro-mechanical processing test machine was developed. This new test machine, which is based on the principle of the scanning force controlled probe microscope, can realize nano/micro-mechanical machining and in-process profile measurement. Experimental results of nano/micro indentation and scratching show that the controllable cutting depth of the test machine can be controlled by PZT actuator. Profile measurement of the machined surface has also been performed by using the test machine and a conventional AFM(Atomic Force Microscopy). A good agreement of the two measurement results have been achieved.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.243-246
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• 2006

In this paper, Experimental results on the measurement of mechanical properties of fine patterns in the MEMS structure are described. The mechanical properties of embossing patterns on metallic thin foil is measured using the nano indentation system, that is developed by Korea Institute of Industrial Technology(KITECH). These micro embossing patterns are fabricated using CIP(Cold Isostatic Press) process on micro metallic thin foils(Al-1100) that are made by rolling process. These embossing patterned metallic thin foils(Al-1100) are used in the reflecting plate of BLU(Back Light Unit) and electrical/mechanical MEMS components. If these mechanical properties of fine patterns are utilized in a design procedure, the optimal design can be achieved in aspects of reliability as well as economy.

• 한국정밀공학회지
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• 제21권4호
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• pp.186-193
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• 2004

Porous anodic alumina has been used widely for corrosion protection of aluminum surfaces or as dielectric material in micro-electronics applications. It exhibits a homogeneous morphology of parallel pores which can easily be controlled between 10 and 400nm. It has been applied as a template for fabrication of the nanometer-scale composite. In this study, mechanical properties of the AAO structures are measured by the nano indentation method. Nano indentation technique is one of the most effective methods to measure the mechanical properties of nano-structures. Basically, hardness and elastic modulus can be obtained by the nano-indentation. Using the nano-indentation method, we investigated the mechanical properties of the AAO structure with different size of nano-holes. In results, we find the hole effect that changes the mechanical properties as size of nano hole.

• 대한기계학회논문집A
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• 제32권10호
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• pp.805-816
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• 2008

The present work reviews the methods to evaluate elastic-plastic material characteristics by indentation tests. Especially the representative stress and strain values used in some papers are critically analyzed. The values should not only represent the load-depth curve, but also represent the whole of deformed material around the impression. We briefly introduce other indentation techniques to evaluate residual stresses, creep properties, and fracture toughness. We also review some technical problems that are related to the accuracy issues in indentation tests.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.132-137
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• 2004

In this work, effects of hyper-elastic rubber material properties on the indentation load-deflection curve and subindenter deformation are first examined via [mite element (FE) analyses. An optimal data acquisition spot is selected, which features maximum strain energy density and negligible frictional effect. We then contrive two normalized functions. which map an indentation load vs. deflection curve into a strain energy density vs. first invariant curve. From the strain energy density vs. first invariant curve, we can extract the rubber material properties. This new spherical indentation approach produces the rubber material properties in a manner more effective than the common uniaxial tensile/compression tests. The indentation approach successfully measures the rubber material properties and the corresponding nominal stress.strain curve with an average error less than 3%.

• 대한기계학회논문집A
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• 제38권9호
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• pp.943-951
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• 2014

마이크로/나노 압입시험에 사용되는 각뿔 혹은 원뿔형 압입자의 선단 형상은 제작한계 및 사용 중 마모 등으로 인해 필수적으로 곡면 형태를 띄게 된다. 많은 압입시험 관련 연구에서 각뿔형 압입자의 선단 형상은 편의상 구형으로 가정한 후, 얕은 압입에 대한 구형압입 이론식을 적용하고 있다. 이러한 가정에는 근본적으로 두 가지 문제점이 있는데, 첫 번째로 이론해의 정확성은 재료 물성치 및 압입자 형상에 따라 변화한다는 점이며, 두 번째로 각뿔형 압입자의 실제 선단 형상은 이상적인 구형이 아니라는 점이다. 본 연구에서는 유한요소해석에 기반하여 압입시험에 미치는 이 두 요소의 영향을 분석한다. 먼저 탄성 구형 압입시험에 대해 푸아송비와 하중-변위 곡선의 상관관계를 살펴보고, 이를 기반으로 수정된 구형 탄성 압입 관계식을 제시한다. 이어 가정된 Berkovich 선단 형상의 3차원 유한요소해석으로부터 압입깊이에 따른 하중-변위 곡선의 특성을 분석한다.