• 소성∙가공
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• 제28권6호
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• pp.354-360
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• 2019

The plastic strain ratio is one of the factors that affect the deep drawability of metal sheets. The plastic strain ratio of fully annealed Cu sheet is low because its texture has {001}<100>. In order to improve the deep drawability of Cu sheet, it is necessary to increase the plastic strain ratio of Cu sheet. This study investigate the increase of plastic strain ratio of a Cu sheet after the first asymmetry rolling and annealing, and the second asymmetry rolling and annealing in air and Ar gas conditions. The average plastic strain ratio (R_m) was 0.951 and |ΔR| value was 1.27 in the initial Cu sheet. After the second 30.1% asymmetric rolling and annealing of Cu sheet at 1000℃ in air condition, the average plastic strain ratio (R_m) was 1.03 times higher. However, |ΔR| was 0.12 times lower than that of the initial specimen. After the second 18.8% asymmetric rolling and annealing of Cu sheet at 630℃ in Ar gas condition, the average plastic strain ratio (R_m) was 1.68 times higher and |ΔR| was 0.82 times lower than that of the initial specimen. These results are attributed to the change of the texture of Cu sheet due to the different annealing conditions.

• 소성∙가공
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• 제28권5호
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• pp.287-293
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• 2019

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 $400^{\circ}C$, the average plastic strain ratio was 0.77. The average plastic strain ratio of 84% hot asymmetrically rolled AA1050 Al sheet at $400^{\circ}C$ is 1.9 times higher than that of initial AA1050 Al sheet. The ${\mid}{\Delta}R{\mid}$ of 84% hot asymmetrically rolled AA1050 Al sheet at $400^{\circ}C$ is 1/2 times lower than that of initial AA1050 Al sheet. This result is due to the development of the intensity of the ${\gamma}-fiber$ texture and the decrease of the intensity of {001}<100> texture after the hot asymmetric rolling of AA1050 Al sheet.

• 소성∙가공
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• 제28권5호
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• pp.281-286
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• 2019

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 $200^{\circ}C$, the average plastic strain ratio was 0.83. The average plastic strain ratio of the 83% hot asymmetrically rolled AA3003 sheet at $200^{\circ}C$ is 1.2 times higher than that of the initial AA3003 sheet. The ${\mid}{\Delta}R{\mid}$ of 83% hot asymmetrically rolled AA3003 sheet at $200^{\circ}C$ is 0.83 times lower than that of the initial AA3003 sheet. This result is due to the development of the intensity of ${\gamma}-fiber$ texture and reduces the intensity of {001}<110> and {001}<100> textures after hot asymmetric rolling of AA3003 sheet.

• 농업과학연구
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• 제37권3호
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• pp.491-499
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• 2010

This study was carried out to investigate the consolidation characteristics of the remolded clay by the oedometer and the constant rate of strain(CRS) consolidation tests. As the rate of strain increases, the settlement rapidly decreased. As the ratio of the sand in the specimen increases, its effect on the rate of strain to the settlement was reduced. As the effective stress increased, the void ratio decreased, while the rate of strain increased, it did not show a clear variation. The reduction of the void ratio was shown to be less than the oedometer test. The coefficient of vertical consolidation with effective stress showed very large variation around preconsolidation stress, but the rate of strain did not provide significant effects. The rate of strain with effective stress gradually decreased at all tests and mixed ratio of sand. The rate of strain at the constant rate of strain tests showed smaller than in the oedometer test. The coefficient of consolidation at the constant rate of strain tests showed much more increase than in the oedometer test. The ratio of the vertical coefficient of consolidation by the odometer and the constant rate of strain tests showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to designing the soft ground improvement.

• International Journal of Automotive Technology
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• 제6권3호
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• pp.259-268
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• 2005

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.

• Composites Research
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• 제31권6호
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• pp.429-434
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• 2018

본 연구에서는 구조물에 부착된 분포형 광섬유 센서의 변형률을 정밀하게 분석하기 위해 위치에 따른 변형률의 변화를 고려하여 광섬유 센서의 변형률 전달률을 분석하였다. 표면에 부착된 코팅된 광섬유 센서의 모델로부터 해석적으로 광섬유 센서의 변형률 전달률을 유도하였으며, 유도된 변형률 전달률은 유한요소해석을 통해 수치적으로 해석한 결과와 비교 검증하였다. 주 구조물의 변형률이 동일한 파장을 가지며 변하는 경우 센서의 변형률 전달률은 위치에 따라 동일한 값을 보였으며, 따라서 변형률 분포의 형상은 왜곡되지 않는다. 하지만 위치에 따라 변형률 파장이 변하면 변형률의 전달률이 위치에 따라 달라져 변형률 분포의 형상이 왜곡될 수 있음을 확인하였다. 본 연구를 통해 얻어진 파장에 따른 변형률 전달률은 분포형 광섬유 센서로부터 주 구조물의 변형률 분포를 정밀하게 추정하는데 유용하게 사용될 것으로 기대된다.

• Advances in concrete construction
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• 제2권3호
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• pp.177-192
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• 2014

One of the main applications of FRP composites is confining concrete columns. Hence identifying the cyclic and monotonic stress-strain behavior of confined concrete columns and the parameters influencing this behavior is inevitable. Two significant parameters affecting the stress-strain behavior are aspect ratio and corner radius. The present study aims to scrutinize the effects of corner radius and aspect ratio on different aspects of stress-strain behavior of FRP confined concrete specimens (rectangular, square and circular). Hence 44 FRP confined concrete specimens were tested and the results of the tests were investigated. The findings indicated that for specimens with different aspect ratios, the relationship between the ultimate stress and the corner radius is linear and the variations of the ultimate stress versus the corner radius decreases as a result of an increase in aspect ratio. It was also observed that increase of the corner radius results in increase of the compressive strength and ultimate axial strain and increase of the aspect ratio causes an increase of the ultimate axial strain but a decrease of the compressive strength. Investigation of the ultimate condition showed that the FRP hoop rupture strain is smaller in comparison with the one obtained from the tensile coupon test and also the ultimate axial strain and confined concrete strength are smaller when a prism is under monotonic loading. Other important results of this study were, an increase in the axial strain during the early stage of unloading paths and increase of the confining effect of FRP jacket with the increase and decrease of the corner radius and aspect ratio respectively, a decrease in the slope of reloading branches with cycle repetitions and the independence of this trend from the variations of the aspect ratio and corner radius and also quadric relationship between the number of each cycle and the plastic strain of the same cycle as well as the independence of this relationship from the aspect ratio and corner radius.

• Steel and Composite Structures
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• 제21권4호
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• pp.921-947
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• 2016

Concrete Filled Fibre Reinforced Polymer Tube (CFFT) for new columns construction has attracted significant research attention in recent years. The CFFT acts as a formwork for new columns and a barrier to corrosion accelerating agents. It significantly increases both the strength capacity (Strength enhancement ratio) and the ductility (Strain enhancement ratio) of reinforced concrete columns. In this study, based on predefined selection criteria, experimental investigation results of 134 circular CFFT columns under axial compression have been compiled and analysed from 599 CFFT specimens available in the literature. It has been observed that actual confinement ratio (expressed as a function of material properties of fibres, diameter of CFFT and compressive strength of concrete) has significant influence on the strength and ductility of circular CFFT columns. Design oriented models have been proposed to compute the strength and strain enhancement ratios of circular CFFT columns. The proposed strength and strain enhancement ratio models have significantly reduced Average Absolute Error (AAE), Mean Square Error (MSE), Relative Standard Error of Estimate (RSEE) and Standard Deviation (SD) as compared to other available strength and strain enhancement ratios of circular CFFT column models. The predictions of the proposed strength and strain enhancement ratio models match well with the experimental strength and strain enhancement ratios investigation results in the compiled database.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.85-92
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• 1996

The Measurement method of the plastic strain ratio is various in Automotive sheet steel. In this paper, the measurement of the plastic strain are used two different methods, ASTM E 517 method and the automatic strain measurement tensile specimen during the tensile test, and compared the plastic strain ratios from the two methods. The experimental results showed that the measured plastic strain ratios from the automatic strain measurement method are coincide with that from the ASTM E 517 standard measurement in various specimens. Therefore, automatic strain measurement method by two extensometers shows good accuracy. Also, the strain dependance of plastic strain ratios could be recorded by the computer continuously and anisotropy of the strength coefficient, K, and strain hardening exponent, n ,could be compared with each direction automatically through the use of automatic strain measurement system.

• 소성∙가공
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• 제23권2호
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• pp.82-87
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• 2014

The plastic strain ratio is one of the factors that affect the deep drawability of Al alloy sheet. The deep drawability of Al alloy sheet is limited because of its low plastic strain ratio. Therefore an increase in the plastic strain ratio to improve the deep drawability of Al alloy sheet is needed. The current study investigated the increase of the plastic strain ratio and the change in texture of AA5083 Al alloy sheet after a 2 step asymmetric rolling with heat treatments. The average plastic strain ratio of initial AA5083 Al alloy sheets was 0.83. After the first asymmetric rolling step of 88% deformation and subsequent heat treatment at $320^{\circ}C$ for 10 minutes the value was still 0.83. After the second asymmetric rolling of 14% reduction and subsequent heat treatment at $330^{\circ}C$ for 10 minutes the plastic strain ratio rose to 1.01. The average plastic strain ratio after the 2 step asymmetric rolling and heat treatment is 1.2 times higher than that of initial AA5083 Al alloy sheet. This result is related to the development of ND/<111> texture component after the second asymmetric rolling and heat treatment.