변형률 제어 반복직접단순전단시험에서 세립분이 모래-실트 혼합토의 간극수압에 미치는 영향

Tran Dong Kiem Lam,박성식,NGUYEN TAN NO,박재현,성희영,손준혁,황금비 한국지진공학회 2024 한국지진공학회논문집 Vol.28 No.1

Understanding the behavior of soil under cyclic loading conditions is essential for assessing its response to seismic events and potential liquefaction. This study investigates the effect of non-plastic fines content (FC) on excess pore pressure generation in medium-density sand-silt mixtures subjected to strain-controlled cyclic direct simple shear (CDSS) tests. The investigation is conducted by analyzing excess pore pressure (EPP) ratios and the number of cycles to liquefaction (Ncyc-liq) under varying shear strain levels and FC values. The study uses Jumunjin sand and silica silt with FC values ranging from 0% to 40% and shear strain levels of 0.1%, 0.2%, 0.5%, and 1.0%. The findings indicate that the EPP ratio increases rapidly during loading cycles, with higher shear strain levels generating more EPP and requiring fewer cycles to reach liquefaction. At 1.0% and 0.5% shear strain levels, FC has a limited effect on Ncyc-liq. However, at a lower shear strain level of 0.2%, increasing FC from 0 to 10% reduces Ncyc-liq from 42 to 27, and as FC increases further, Ncyc-liq also increases. In summary, this study provides valuable insights into the behavior of soil under cyclic loading conditions. It highlights the significance of shear strain levels and FC values in excess pore pressure generation and liquefaction susceptibility.

PLASTIC STRAIN RATIOS AND PLANAR ANIOSOTROPY OF AA5182/POLYPROPYLENE/AA5182 SANDWICH SHEETS

KIM K. J. The Korean Society of Automotive Engineers 2005 International journal of automotive technology Vol.6 No.3

In order to analyze the sheet drawability, the measurement of the plastic strain ratio was carried out for the 5182 aluminum alloy sheets in which were cold rolled without lubrication and subsequent recrystallization annealing. The average plastic strain ratio of the 5182 aluminum sheets was 1.50. It was considered that the higher plastic strain ratio was resulted from the ND//<111> component evolved during rolling and maintained during annealing. The AA5182/polypropylene/AA5182 (AA/PP/AA) sandwich sheets of the 5182 aluminum alloy skin sheet and the polypropylene core sheet with high formability have been developed for application for automotive body panels in future light weight vehicles with significant weight reduction. The AA/PP/AA sandwich sheets were fabricated by the adhesion of the core sheet and the upper and lower skin sheets. The AA/PP/AA sandwich sheet had high plastic strain ratio (1.58), however, the planar anisotropy of the sandwich sheet was little changed after fabrication. The optimum combination of directionality of the upper and lower skin sheets having high plastic strain ratio and low planar anisotropy was calculated theoretically and an advanced process for producing the sandwich sheets with high plastic strain ratio was proposed. The developed sandwich sheets have a high average plastic strain ratio of 1.55 and a low planar anisotropy of 0.17, which was improved more by 3.2 times than that of 5182 aluminum single sheet.

열간 비대칭 압연한 AA1050 Al 판재의 집합조직과 소성변형비 변화

보보무로드 함라쿠로프,이철우,김인수 한국소성∙가공학회 2019 소성가공 : 한국소성가공학회지 Vol.28 No.5

The plastic strain ratio is one of the factors of the deep drawability of metal sheets. The plastic strain ratio of Al sheet is low value. Therefore, it is necessary to increase the plastic strain ratio in order to improve the deep drawability of the Al sheet. This study investigated the increase in the plastic strain ratio and the texture change of AA1050 Al sheet after the hot asymmetric rolling. The average plastic strain ratio of initial AA1050 Al sheets was 0.41. After 84% hot asymmetric rolling at 400°C, the average plastic strain ratio was 0.77. The average plastic strain ratio of 84% hot asymmetrically rolled AA1050 Al sheet at 400°C is 1.9 times higher than that of initial AA1050 Al sheet. The ΔRof 84% hot asymmetrically rolled AA1050 Al sheet at 400°C is 1/2 times lower than that of initial AA1050 Al sheet. This result is due to the development of the intensity of the γ-fiber texture and the decrease of the intensity of {001}<100> texture after the hot asymmetric rolling of AA1050 Al sheet.

열간 비대칭 압연한 AA3003 판재의 집합조직과 소성변형비 변화

보보무로드 함라쿠로프,이철우,김인수 한국소성∙가공학회 2019 소성가공 : 한국소성가공학회지 Vol.28 No.5

The plastic strain ratio is one of the factors of the deep drawability of metal sheets. The plastic strain ratio of Al sheet is low value. Therefore, it is necessary to increase the plastic strain ratio in order to improve the deep draw ability of the Al sheet. This study investigated the increase of the plastic strain ratio and the texture change of AA3003 sheet after the hot asymmetric rolling. The average plastic strain ratio of the initial AA3003 sheets was 0.69. After 83% hot asymmetric rolling at 200°C, the average plastic strain ratio was 0.83. The average plastic strain ratio of the 83% hot asymmetrically rolled AA3003 sheet at 200°C is 1.2 times higher than that of the initial AA3003 sheet. The ΔRof 83% hot asymmetrically rolled AA3003 sheet at 200°C is 0.83 times lower than that of the initial AA3003 sheet. This result is due to the development of the intensity of γ-fiber texture and reduces the intensity of {001}<110> and {001}<100> textures after hot asymmetric rolling of AA3003 sheet.

Texture Control of Aluminum, Iron, and Magnesium Alloy Sheets to Increase Their Plastic Strain Ratios

Dong Nyung Lee,Heung Nam Han 한국소성가공학회 2011 기타자료 Vol.2011 No.8

It is known that the limiting drawing ratio of sheet metals is proportional to their plastic strain ratios, and the plastic strain ratios of fcc and bcc metal sheets increase with increasing 〈111〉//ND component in their textures. Conventional cold rolling and subsequent annealing of fcc metals cannot give rise to the 〈111〉//ND component. Specifically, the cold rolling texture of polycrystalline fcc metals is characterized by the fiber connecting the {112}〈111〉, {123}〈634〉, and{011}〈211〉 orientations in the Euler space, which is often called the β-fiber. The density of each component in the fiber depends on the stacking fault energy of metals. The {112}〈111〉 and {123}〈634〉 textured Al alloy sheets evolve the {001}〈100〉 texture, when recrystallized. The low plastic strain ratios of the Al alloy sheets are attributed to the {001}〈100〉 texture. The 〈111〉//ND texture can be obtained in shear deformed fcc sheets. Bcc steels develop the 〈111〉//ND texture when cold rolled and recrystallized. However, the density of 〈111〉//ND depends on the content of dissolved interstitial elements such as carbon and nitrogen. The density of the 〈111〉//ND component decreases with increasing concentration of the dissolved interstitial elements. For a given steel, the density of the 〈111〉//ND component can vary with varying thermomechanical treatment. Magnesium alloy sheets are subjected to sheet forming processes at temperatures of 200℃ or higher because of their basal plane texture, or the 〈0002〉//ND orientation. Many studies have been made to alleviate the component so that the magnesium alloy sheets can have better formability. In this article, the above issues are briefly reviewed and discussed.

Effect of Freeze-Thaw Cycles on Dynamic Characteristics of Undisturbed Silty Clay

Gao Hang Cui,Zhuo Cheng,Daili Zhang,Shuxian Ma,Zhiqiang Liu 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.9

We conducted dynamic triaxial tests of undisturbed soil samples under different control parameters using the Global Digital Systems (GDS) dynamic triaxial instrument. We investigated the dynamic and engineering characteristics of undisturbed soil under a freeze–thaw cycle. When the dynamic load amplitude and the number of freeze–thaw cycles were adjusted, we explored the cumulative plastic strain, dynamic elastic modulus, and dynamic strength of undisturbed soil, and we then proposed appropriate fitting formulae to compute the cumulative plastic strain, dynamic elastic modulus, and dynamic strength. The findings revealed that as the number of freeze–thaw cycles increased, the cumulative plastic strain grew, the dynamic strength progressively fell, and the dynamic elastic modulus dropped first, but then increased. The critical physical and dynamic features of soil changed dramatically during one to six freeze–thaw cycles. This study’s suggested formula for the average growth ratio can directly reflect the cumulative plastic strain fluctuation of soil throughout freeze–thaw cycles. The formula has a good fitting effect on undisturbed soil, according to the test findings, and the accumulative plastic strain, dynamic elastic modulus, and dynamic strength may be computed within a specified range. The findings of this study contribute to a better understanding of the effect of the freeze–thaw cycle on the dynamic characteristics of undisturbed silty clay, as well as a theoretical foundation for the design and construction of silty clay highway subgrade in seasonally frozen regions as well as the dynamic analysis of vehicle simulation in seasonally frozen regions.

냉간 단조된 5083 알루미늄 합금에서의 집합조직 발달과 소성변형 비

한준현,지광구,오규환 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.6

5083 aluminum alloys were cold-forged to study the possibility of enhancing the formability and reducing the planar anisotropy. Texture evolution during cold forging was discussed with pole figure and orientation distribution function (ODF). The formability and planar anisotropy in forged 5083 aluminum alloys were evaluated in terms of the r-value (plastic strain ratio or Lankford parameter) which was not only calculated from the measured pole figures but also measured in direct by tensile tests. The (110) <uvw> fiber texture was developed during cold forging, by which the 5083 aluminum alloy having high formability and low planar anisotropy could be produced. (Received March 18, 2004)

가능최대지진(MCE)을 적용한 콘크리트 댐 피어부 내진성능평가 방안 개선

오정근,정영석,권민호 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 논문집 Vol.27 No.6

본 논문에서는 MCE를 적용한 콘크리트 댐 피어부의 동적소성해석을 통한 내진성능평가 수행 시 소성재료모델, 성능수준 평가 방법에 대한 현행 기준의 적용성을 검토하고 개선안을 제시하였다. 다양한 조건으로 동적소성해석을 수행하여 소성재료모델에 대한 적용성을검토하였고, 그 결과 현행 댐 내진성능평가요령에서 제시하는 평균응력-평균변형률 기법은 최소철근비가 확보되지 않은 조건에서 동적탄성해석으로 예측한 결과보다 피어부의 응답을 과소평가하는 것으로 확인되었다. 따라서 최소철근비가 확보되지 않은 댐 피어부는 무근콘크리트로 간주하여 콘크리트 인장거동특성에 파괴에너지를 적용하는 방법으로 피어부 성능수준을 평가하도록 하는 개선안을 도출하였다. 개선사항적용할 경우 현행 내진성능평가 방법보다 보수적인 평가결과를 도출할 수 있다. This paper assesses the suitability of existing standards for plastic material models and performance level evaluation methods in seismic performance evaluations of concrete dam piers during Maximum Credible Earthquakes (MCE). Dynamic plastic analysis was conducted to examine the applicability of the plastic material model under various conditions. As a result reveal that when the minimum reinforcement ratio is not met, the average stress-average strain method recommended in current dam seismic performance evaluation guidelines tends to underestimate pier responses compared to the predicted outcomes of dynamic elastic analysis. Consequently, the paper proposes an improvement plan that treats dam piers with an insufficient minimum reinforcement ratio as unreinforced and integrates fracture energy into concrete tensile behavior characteristics for performance level evaluation. Implementing these improvements can lead to more conservative evaluation outcomes compared to current seismic performance evaluation methods.

무윤활 압연한 알루미늄 합금의 집합조직과 성형성

아크라모프 사이드무로드(Saidmurod Akramov),김인수(Insoo Kim) 한국소성·가공학회 2009 소성가공 : 한국소성가공학회지 Vol.18 No.2

Formability and other mechanical properties of sheet metals are strongly dependent on the texture. It was studied to improve the formability of the Al alloy(AA3003) sheets which were rolled under the non-lubrication condition and subsequent heat treated. In the non-lubrication rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios were investigated in this study. Non-lubrication rolled Al sheets showed a fine grain size and after subsequent heat treated specimens showed that the β-fiber texture component was increased. The plastic strain ratios of the nonlubrication rolled and subsequent heat treated Al alloy sheets were about two times higher than those of the original Al sheets. These could be related to the formation of β-fiber texture components through the non-lubrication rolling and subsequent heat treatment in Al sheet.

자동차 차체용 알루미늄 합금 판재의 기계적특성과 부식피로수명

박인덕(In-Duck Park),윤옥남(Ok-Nam Yoon),남기우(Ki-Woo Nam) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.2

The objective of this study is to compare the mechanical properties 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.<br/> Comparing of TG25 and AC120 alloy sheets, TG25 alloy sheets showing higher plastic strain 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 and the columnar structure and dendritic structure was observed in nugget 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 fatigue life decreased as dipping time increased, when a concentration was constant.