• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.294-297
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• 2009

The frictional behaviors of Cermets/Cr-Ceramics and Cu-Al coatings of piston ring were investigated. Friction tests were carried out by pin-on-disk test and materials properties of coating layer were analyzed by nano indentation tester. Higher friction coefficient was obtained at harder coating with rougher surface. In case of hard-coating, the scratch depth, width and pile-up height had close relationship with indentation hardness. So the scratch width, depth and pile-up height increases with decreasing friction coefficient. But in case of soft-coating, the friction coefficients are strongly dependent on the morphological characteristics after nano scratching more than indentation hardness.

• 대한기계학회논문집A
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• 제21권2호
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• pp.305-316
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• 1997

A more efficient method for obtaining the fatigue life enhancement of a structure member with fastener holes is described. It is based on the combined process of cold-expansion and ring-indentation. Residual stresses were induced onto premachined holes using ring-indentation process near the fastener hole combined with cold-expansion. And residual stresses at the vicinity of a hole were evaluated using a fracture mechanics approach. The compressive residual stresses were larger using the combined process than is in the case of simple cold-expansion. Fatigue testing of aluminum specimens showed that the fatigue crack growth retardation emanating from a circular hole was greater for the combined process than for a simple cold-expansion alone.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.597-602
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• 2001

A method for the retardation of fatigue crack growth using ring indentation at the vicinity of a crack is examined. Residual stresses near crack tip are evaluated using fracture mechanics approach. The motivation is to develop a simple and effective method for obtaining an increase in fatigue lives to total failure of materials with crack. Fatigue testing of aluminum specimen showed that the retardation effects are observed after the application of the method.

• 한국항공우주학회지
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• 제31권10호
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• pp.27-33
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• 2003

균열주위에 링압인을 부가함으로서 피로균열을 지연하는 수법을 제시하였다. 균열주위의 잔류응력분포는 Bueckner가중함수를 이용한 파괴역학적 수법으로 평가하였다. 본 연구는 균열을 가진 재료에 대한 파단시까지의 피로수명을 향상시키기 위한 단순하면서도 표과적인 수법을 개발하는데 있다. 알루미늄재료에 대한 피로실험결과 본 수법이 피로지연효과를 효율적으로 얻을 수 있는 것으로 나타났다.

• 대한기계학회논문집
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• 제8권4호
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• pp.313-320
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• 1984

본 연구에서는 원형 단면 링 압인(circularcross-section ring indentation) 을 노치 주위에 주고 피로 하중하에서 발생한 균열이 성장하는 거동을 관찰하고 해석 하므로써 균열의 저지 및 지연 방법으로써 가능성을 제시하고자 한다.

• 소성∙가공
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• 제18권6호
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• pp.465-470
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• 2009

The frictional behaviors of Cermets/Cr-Ceramics and Cu-Al coatings of piston ring were investigated. Friction tests were carried out by pin-on-disk test and materials properties of coating layer were analyzed by nano indentation tester. The effect of surface roughness of cylinder liner on the friction coefficient was analyzed. This study provided tribological data of hard and soft piston ring coatings against cylinder liner. The surface roughness does exert an influence on the average friction coefficient, with smoother surfaces generally yielding lower friction coefficients. In case of hard-coating, the scratch depth, width and pile-up height had close relationship with hardness. So the scratch width, depth and pile-up height increases with decreasing friction coefficient. But in case of soft-coating, the friction coefficients are strongly dependent on the morphological characteristics such as, scratch depth, width, pile-up height and elastic modulus.

• Composites Research
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• 제24권2호
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• pp.9-13
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• 2011

본 논문에서는 zinc blende계열의 결정구조를 갖는 실리콘 내부의 결함을 분석할 수 있는 대칭축 파라메터 (Symmetric axis parameter)방법을 이용하여, 탄성 및 소성 변형을 구별하는 방법을 제시하였다. 분자 동력학 해석프로그램인 LAMMPS를 사용하여, 실리콘에 대한 나노인덴테이션 해석을 수행하였다. 구형 인덴터 아래에 발생한 실리콘내부의 결함은 ring crack에서의 threefold 무늬와 전위발생경로를 보여주였다. 또한, 해석결과는 기존의 이론이나, 실험결과와도 일치하는 것을 확인하였다.

• 대한기계학회논문집A
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• 제20권12호
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• pp.3847-3855
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• 1996

In order to study the relationship between static and cynamic behaviors of silion caride, both quasi-static indentaiton and impact experiments of spherical particle have been conducted. The difference inmaterial behavior when using the two mehtods suggests a loading rate difference in the damate pattrern and fracture strength of silicon carbide. This investigation showed some difference in damage pattern according to particla property, especially inthe case of particle impact. There was no differences in deformation behaviors according to the loading rate when the crater profiles were compared with each other at the same contact radius. From the result of residual strength evaluation, it was found that the strength degradation began at the initiation of ring crack and its behavior was colsely related to morphologies of the damage developed which was also dependent upon the extent of deformation atthe loaidng point. In the case of static indentation, there didnot exist the particle property effects onthe strength degradation behavior.

• Design & Manufacturing
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• 제11권3호
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• pp.46-50
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• 2017

Press processing is one of the best machining methods capable of mass production, satisfying dimensional, shape and quality among the methods of processing a metal plate. Among them, Fine blanking is a method of obtaining a precise cross-section such as machining of the shear surface shape. In this research, Using SCP-1 and SHP-1 materials. The deformation behaviors of the material flow affecting the die height of the shear section in accordance with the position of the V-ring in the Fine blanking were compared and analyzed. Result of interpretation, It was confirmed that the force acts on the position where the material flow direction accurately forms the die roll that the material of SCP-1 is at a position of 1.5 mm and the material of SHP-1 is at 2.0 mm. As a result, it was confirmed that the state of fo1111ing the shear surface by the V-ring was excellent. Using analysis results, In the experiment, the height of the die roll was considered by applying The position of the V-ring was 1.5 mm in SCP-1 and 2.0 mm in SHP-1. As a result of comparing the height of the die rolls, the height values of the die rolls were different from each other, It has been considered that the tendency of the die rolls to coincide with each other. It is considered that the difference of the die roll height is caused by the pressure input of the V-ring. In this study, the deformation behavior of the material(In addition to the position of the V-ring, the flow direction of the material depends on the shape of the V-ring and the Indentation amount) is considered to be an important factor in determining die roll height.

• 한국재료학회지
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• 제8권3호
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• pp.200-205
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• 1998

질화규소-질화붕소 복합재료의 접촉하중에 의한 손상거동을 질화붕소 첨가량의 함수로 고찰하였다. Indentation응력-변형율 곡선은 선형성을 벗어나 소성 특성을 갖는 재료임이 밝혀졌으며, 재료 표면으로 부터의 ring이나 cone형상의 균열 대신 표면하부에 전단응력에 의한 마이크로 크기의 준소성 변형 영역이 넓게 형성되어 손상저항성이 높은 재료로의 활용이 기대되었다. 이 때 마이크로 파괴와 연관된 shear faults가 이 재료의 소성을 갖도록 하는데 중요한 역할을 하였다. 질화붕소의 첨가량이 증가함에 따라 질화규소-질화붕소 재료는 보다 soft해지고 준소성의 특성을 나타내었다.