• Tunnel and Underground Space
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• v.27 no.3
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• pp.172-184
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• 2017

The hardness and mechanical properties of the minerals in the Daejeon granite according to depths were investigated by indentation test, load-unload test, and cycle test of dynamic ultra-micro hardness. As a result of the tests, it was possible to classify into three mineral groups (Group-1, -2, -3). The Martens hardness was not significantly different between 41 m and 223 m depths in three mode tests. Nevertheless, they showed in the order of a cycle test < load-unload test < indentation test. Considering the average Martens hardness, elastic modulus, and indentation work for each mineral group, their boundaries were relatively clear. In conclusion, A relatively accurate hardness of minerals can be obtained by three mode tests of dynamic ultra-micro hardness. In addtion, it was possible to characterize the elastic modulus and the elastic-plastic properties of the minerals from the load-unload and cycle tests.

• Journal of the Korean Vacuum Society
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• v.22 no.5
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• pp.245-249
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• 2013

The $HfO_X$ thin film was deposited what it has been paid attention to the next generation oxide thin layer of MOSFET (metal-Oxide semiconductor field-effect-transistor) by rf magnetron sputter on Si (100) substrate. The $HfO_X$ thin film was deposited using a various oxygen gas flows (5, 10, 15 sccm). After deposition, $HfO_X$ thin films were annealed from 400 to $800^{\circ}C$ for 20 min in nitrogen ambient. The electrical characteristics of the $HfO_X$ thin film was improved by leakage current properties, depending on the increase of oxygen gas flow and annealing temperature. In particular, the properties of nano-mechanics of $HfO_X$ thin films were measured by AFM and Nano-indenter. From the results, the maximum indentation depth at the basis of maximum indentation force was increased from 24.9 to 38.8 nm according to increase the annealing temperature. Especially, the indentation depth was increased rapidly at $800^{\circ}C$. The rapid increasement of indentation depth was expected to be due to the change of residual stress in the $HfO_X$ thin film, and this result was caused by relative flux of oxygen outgasing during the annealing process.

• Composites Research
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• v.31 no.5
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• pp.260-266
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• 2018

This study investigates thermal and mechanical characterization of Hafnium carbide coating on the $C_f-C$ composites. The hafnium carbide coatings by vacuum plasma spray on the C/C-SiC composites are prepared to evaluate oxidation and wear resistance. We perform the thermal durability tests by thermal cycling at $1200^{\circ}C$ for 10cycles in air and investigates the weight change of each cycle. We also evaluate the wear and indentation behavior using tungsten carbide ball indenter as a mechanical evaluation. As a result, the HfC coating is beneficial to reduce of weight loss during thermal cycling test and improve the elastic property of C/C-SiC composite. Especially, the HfC coating improves the wear resistance of C/C-SiC composite.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.346-351
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• 2009

Due to the decrease of line width and increase of the integration level of the device, it is expected that 'Bottom-up' method will replace currently used 'Top-down' method. Researches about 'Bottom-up' device production such as Nanowires and Nanobelts are widely held on. To utilize these technologies in devices, properties of matter should be exactly measured. Nano-indenters are used to measure the properties of nano-scale structures. Additionally, Nano-indenters provide AFM(Atomic Force Microscopy) function to get the image of the surface and get physical properties for exact position of nano-structure using this image. However, nano-indenter tips have relatively much bigger size than ordinary AFM probes, there occurs considerable error in surface image by Nano-Indenter. Accordingly, this research used 50nm Berkovich tip and 1um $90^{\circ}$ Conical tip, which are commonly used in Nano-Indenter. To find out the surface characteristics for each kind of tip, we indented the surface of thin layer by each tip and compared surface image and indentation depth. Then, we got image of 100nm-size structure by surface scanning using Nano-Indenter and compared it with surface image gained by current AFM technology. We calculated the errors between two images and compared it with theoretical error.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.516-522
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• 2002

For the experimental study of rotor steel, seven kind of specimens with different degradation levels were prepared by isothermal heat treatment at $630^{\circ}C$. Spherical indentation technique was developed to evaluate the flow properties of metallic materials in carbon steel, stainless steel, and alloys, etc. Through the spherical indentation test, differently degraded 1Cr-1Mo-0.25V steel's mechanical properties were observed and compared with conventional standard test data. The flow properties of 1Cr-1Mo-0.25V steel's were estimated by analyzing the indentation load-depth curve. To characterize the flow property, we used material yield slope and constraint factor index rather than strain-hardening exponent because the variation of strain-hardening exponent was very little and the data showed irregularly. And the constraint factor's effect was small when the material yield slope was taken into account.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.5
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• pp.385-392
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• 2016

Recently in the display industry, demands for high-luminance and resolution of display devices have been steadily increasing. Generally, micro linear patterns are applied to an optical film in order to improve its properties of light. However, these patterns are easily viewed to eyes and moire phenomenon can be occurred. Micro random patterns are proposed as a method to solve these problems, increasing light-luminance and light-diffusion. However, conventional pattern manufacturing technologies have long processing times and high costs making it difficult to apply to large area molds. In order to combat this issue, micro-random patterns are formed by using a roll to plate indentation method along with abrasive paper tools composed of AlSiO2, SiC, and diamond grains. Also, forming properties, such as size and fill-factor of random patterns, are analyzed depending on type, mesh of abrasive paper tools, and indentation forces.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.291-296
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• 2004

Cast austenitic stainless steel piping pump, valve casings, and elbows are susceptible to reductions in toughness and ductility because of long term exposure at the operating temperatures in LWR(light water reactor). In this paper, we have measured the material properties of long term aged CF-8A cast stainless steel, accelerated aging at $400^{\circ}C$. These studies have been carried out using Indentation tests(automated ball indentation and nano-indentation) and EDS(energy dispersive spectroscopy). The fracture toughness of CF-8A cast stainless steel was also determined by using standard fracture toughness and Automated Ball Indentation.

• Journal of Power System Engineering
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• v.16 no.1
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• pp.72-77
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• 2012

Acoustic emission (AE) is known to be sensitive to fracture process and so it was expected that AE data may propose as a means of monitoring the fracture information. The aim of this study is to analyze the characteristic of AE signal emitted from glass during Vickers indentation. To observe AE characteristics by surface effect, both glass and coating glass were studied. During Vickers indentation loading, AE signal resulted from penny-like crack is detected. During Vickers indentation unloading, AE signal resulted from both radial/median crack and lateral crack is detected. In case of indentation on glass, the emission energy(${\epsilon}$) is found to be approximately proportional to the fourth power of the crack length. In case of indentation on coating glass, the emission energy(${\epsilon}$) is approximately proportional to the crack length.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.483-488
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• 2001

Until now, the tensile properties of materials can be obtained just in accordance with conventional tensile testing methods which are described in several standards such as ASTM (American Society for Testing and Materials) standard and BS (British Standard). For some cases including on-service facility materials, however, the standard testing methods cannot be applicable due to the destructive testing procedure and specimen size requirement. Therefore, simple, non-destructive and advanced indentation technique was proposed. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. In this paper, the research trend of non-destructive evaluation of tensile properties using AIS (advanced indentation system) and its application fields are reviewed and discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.10
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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.