• 대한기계학회논문집
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• 제14권5호
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• pp.1193-1199
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• 1990

본 연구에서는 가공경화지수 (n)가 서로 다른 몇가지 재료를 선택하고 과대하 중의 비 (%PL)를 달리하는 단일 과대하중 피로 시험을 행하여 재료의 가공경화지수가 피로 균열 진파의 지연거동에 미치는 영향과 아울러 균열닫힘현상과의 관계를 구명하였다.

• 소성∙가공
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• 제1권1호
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• pp.42-51
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• 1992

The ring compression test has been widely employed as an experimental means to determine the friction factor. The calibration curves are obtained by the rigid-plastic finite element analysis for various work-hardening exponent and strain-rate hardening exponent. The effects of work-hardening exponent and strain-rate hardening exponent are thoroughly studied and discussed from the finite element computation. The change of friction factor during height reduction in ring compression is also discussed. Then, the method to estimate the change of friction factor during ring compression is proposed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.262-262
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• 2004

오오스테나이트 스테인리스강은 강도, 연성, 인성, 내식성 등이 우수하여 광범위하게 사용되고 있지만 절삭 시 전단저항이 크므로 절삭날 결손이나 용융을 유발하여 가공면을 안정시키기 어려우며 난삭재로서 가공경화가 매우 큰 재료이다. 그리고 질소를 약 0.1wt.％ 첨가한 316LN강은 316L강에 비해 고온강도 특성이 우수하여 주목받고 있는 새로운 재료이이지만, 저탄소의 강도 약점을 보완하기 위하여 고용강화원소로 질소를 첨가하기 때문에 높은 강도로 인하여 절삭가공에 난점이 있으므로 이 재료를 응용하기 위해서는 절삭 시 재료 표층부에 발생하는 가공 변질층에 관한 연구가 필요하다.(중략)

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.523-528
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• 2001

In this study we tried to determine the work-hardening exponent using continuous indentation test. Work-hardening exponent, which was determined by Hollomon equation, in tensile test, is an important parameter to determine plastic deformation and brittle/ductile property of materials. For using Hollomon equation, true stress and true strain were defined by indentation depth and indentation load. Using them the new equation, which is constituted by indentation depth, indentation load and work-hardening exponent, was induced. Indentation depth was calibrated because of elastic deflection and pile-up/sink-in phenomena. Work-hardening exponents of various steels derived by it showed good agreement to the results of tensile tests. In addition to experiments, FEM simulation was accomplished to investigate changes of real contact depth with materials properties changes. Through this simulation it is concluded that the real contact depth is changed by Y/E value which affect the early stage of indentation, and work-hardening exponent which the latter stage.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.256-261
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• 2000

In this study, we derived work-hardening exponent using continuous indentation test technique. Continuous indentation test technique is a powerful method to evaluate mechanical properties, such as hardness, modulus, ${\sigma}-{\varepsilon}$ curves and etc. It has many merits conventional indentation test has. The relationship between true stress and mean contact pressure and between strain and indentation depth were derived. While the indenter pushes the materials, the region around the indenter is deflected elastically. It is called elastic deflection. And pile-up phenomenon related to plastic deformation around the indenter increased the contact depth, and sink-in phenomenon decreases. So we calibrated contact depth change by considering elastic deflection and pile-up/sink-in. Using calibrated contact depth we redefined the relationship between true stress and mean contact pressure and between strain and contact depth. Through these relationship we could derive work-hardening exponent by analyzing load-depth curves. And it showed good agreement with tensile test results.

• Elastomers and Composites
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• 제44권3호
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• pp.315-322
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• 2009

이피디엠/폴리프로필렌 열가소성 경화물을 오일의 배합 순서를 달리한 두 가지 방식(오일 블렌드 후 가교방식과 가교 후 오일 블렌드 방식)으로 제조하여 가교도(겔분율), 경도, 인장강도, 신율, 용융흐름지수 등을 조사, 오일의 블렌드 방식이 열가소성 경화물의 물성에 미치는 영향을 알아보았다. 오일의 블렌드 방식에 따른 두 경화물의 가교도와 기계적 물성의 차는 크지 않았으나, 가공성에 있어서는 가교 후 오일 블렌드 방식으로 제조한 경화물의 용융흐름지수가 현저히 증가한 결과를 보였다.

• 소성∙가공
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• 제3권2호
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• pp.215-228
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• 1994

The purpose of this paper is to pursue a general method to determine both the flow stress of a material and the friction factor by ring compression test. The materials are assumed to obey the expanded n-power hardening rule including the strain-rate effect. Ring compression is simulated by the rigid-plastic finite element method to obtain the database used in determining the flow stress and friction factor. The Simulation is conducted for various strain hardening exponent, strain-rate sensitivity, friction factor, and compressing speed, as variables. It is assumed that the friction factor is constant during the compression process. To evaluate the compatibility of the database, experiments are carried out at room and evaluated temperature using specimens of aluminum 6061-T6 under dry and grease lubrication condition. It is shown that the proposed test method is useful and easy to use in determining the flow stress and the friction factor.

• 대한기계학회논문집
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• 제12권6호
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• pp.1335-1342
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• 1988

본 연구에서는 일반적인 구조물에 가장 많이 사용되는 연강박판재(SM12C)가 반복인장하중을 받았을 경우, 즉 이 재료가 프리응력과 프리변형을 받았을 때 시간의 경과에 따르는 경도, 항복강도 및 가공경화지수의 변화를 살펴보았다. 이와 같은 실 험을 통하여 재료가 서서히 안정화되어가는 상태를 왁인하였으며 이를 기초로 하여 레 지듀얼강도(residual strength)와 피로크랙진전속도의 거동을 체계적으로 구명하여 이 연강박판재의 구조물의 안전사용에 기여하도록 하는데 그 목적을 두었다. 아울러 프 리응력 및 프리변형을 받았을 때의 연강박판재의 기계적 성질의 변화를 Taylor의 가공 경화이론에 대응시켜 검토하였다.

• 한국정밀공학회지
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• 제21권1호
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• pp.71-79
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• 2004

The deformed layers generated in face milling works were comparatively investigated to type 316L and nitrogen(N)-added type 316LN stainless steels. In order to characterize mechanical properties between type 316L and type 316LN, high-temperature tensile tests were conducted with different temperatures: R.T to $700^{\circ}C$. The cutting forces of three components, Fx, Fy and Fz were measured using a tool dynamometer through the face milling cutting tests. The deformed layers were measured by micro-hardness tests along deformed layers. The results of mechanical properties showed that type 316LN was superior to type 316L. The deformed layers of two steels were generated in the 1501m-3001m ranges, and type 316L was higher than type 316LN. The reason for this is due to the high strength properties by nitrogen effect. It was found that deformed structures were well observed for type 316L, but were minutely observed for type 316LN in this cutting conditions.

• 한국해양공학회지
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• 제11권2호
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• pp.57-69
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• 1997

The objetive of this study is to compare the mechanical proprties of 6000 series Al-Mg-Si aluminum alloy (AC120) with 5000 series Al-Mg aluminum alloy (TG25), and to investigate the influence of corrosion solution for fatigue life. Comparing of TG25 and AC120 alloy sheets, TG25 alloy sheets showing higher plastic ratio and total elongation have better formability than AC120 alloy sheets. The hardness of nugget area was a little higher than that of base metal area. Also, grain coarsening was observed in HAZ(Heat Affected Zone). In a corrosion fatigue experiment, the fatigue life decreased as concentration increased, when a dipping time was constant. The life decreased as dippling time increased, when a concentration was constant.