• 제목/요약/키워드: Large strain

검색결과 1,570건 처리시간 0.031초

Gamma TiAI 합금의 고온 변형거동 - 미세조직의 변화 및 변형기구 (High Temperature Deformation Behavior of Gamma TiAl Alloy - Microstructural Evolution and Mechanisms)

  • 김정한;장영원;이종수
    • 소성∙가공
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    • 제11권6호
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    • pp.529-537
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    • 2002
  • A series of load-relaxation tests and tensile tests were conducted to study the high temperature deformation mechanism of fine duplex gamma TiAl alloy at temperatures ranging from 800 to 105$0^{\circ}C$. Results of load relaxation test showed that deformation behavior at a small imposed strain ($\varepsilon$≒0.05) was dominated by dislocation glide and dislocation climb. To investigate the deformation behavior at a large amount of strain, the processing map was constructed using a dynamic materials model. Two domains were characterized in the processing map obtained at a strain level of 0.6. One domain was found at the region of 98$0^{\circ}C$ and $10^{-3}/sec$ with a peak efficiency of 48%, which was identified as a domain of dynamic recrystallization from the microstructural observation. The order was observed at the region of 125$0^{\circ}C$ and $10^{-4}/sec$ with a peak efficiency of 64%. The strain rate sensitivity measured indicates that the material was deformed by the superplasticity in the region.

선조질강 ESW95의 기계적 성질에 관한 연구 (Study on Mechanical Behavior of a Pre-Heat Treated Steel of ESW95)

  • 박지태;엄재근;김종훈;윤덕재;전만수
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2008년도 춘계학술대회 논문집
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    • pp.439-443
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    • 2008
  • We investigate the mechanical behavior of a pre-heat treated steel of ESW95, which is being used for automotive parts including tie-rods to save manufacturing cost and enhance product quality. SCM435 is also investigated to reveal the characteristics of the pre-heat treated steel tested. AFDEX/MAT is used to extract the true stress-strain curve over the large strain with higher accuracy. It has been found that ESW95 has very week strain-hardening behavior which can be negligible compared with SCM435 and that the initial yield strength is quite high and the toughness of ESW95 reaches nearly 75% of SCM435. ESW95 is characterized by the weak strain-hardening behavior and high yield strength that can be lead to minimization of post-processing including heat treatment and straightening. ESW95 and SCM435 are also compared by applying them to ball-stud forging by computer simulation. It is expected that a great deal of change may take place in production as well as in service if the pre-heated steels are adopted.

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Strain Transmission Characteristics of Packaged Fiber Bragg Grating Sensors for Structural Health Monitoring

  • Cho, Sung-In;Yoo, Seung-Jae;Kim, Eun-Ho;Lee, In;Kwon, Il-Bum;Yoon, Dong-Jin
    • 비파괴검사학회지
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    • 제30권3호
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    • pp.236-243
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    • 2010
  • Fiber Bragg grating(FBG) sensor arrays can be used to monitor the mechanical behavior of the large composite structures such as wind turbine rotor blades and aircrafts. However, brittle FBG sensors, especially multiplexed FBG sensors are easily damaged when they are installed in the flexible structures. As a protection of brittle FBG sensors, epoxy packaged FBG sensors have been presented in this paper. Finite element analysis and experiments were performed to evaluate the effects of adhesives, packaging materials and the bonding layer thickness on the strain transmission. Two types of epoxy were used for packaging FBG sensors and the sensor probes were attached with various bonding layer thickness. It was observed that thin bonding layer with high elastic modulus ratio of the adhesive to packaging provided good strain transmission. However, the strain transmission was significantly decreased when elastic modulus of the adhesive was much lower than the packaged FBG sensor probe's one.

Ultimate strength and strain models proposed for CFRP confined concrete cylinders

  • Berradia, Mohammed;Kassoul, Amar
    • Steel and Composite Structures
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    • 제29권4호
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    • pp.465-481
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    • 2018
  • The use of external carbon-fiber-reinforced polymer (CFRP) laminates is one of the most effective techniques existing for the confinement of circular concrete specimens. Currently, several researches have been made to develop models for predicting the ultimate conditions of this type of confinement. As most of the major existing models were developed based on limited experimental database. This paper presents the development of new confinement ultimate conditions, strength and strain models, for concrete cylinders confined with CFRP composites based on a statistical analysis of a large existing experimental database of 310 cylindrical concrete specimens wrapped with CFRP. The database is used to evaluate the performance of the proposed and major existing strength and strain models. Based on the two different statistical indices, the coefficient of determination ($R^2$) and the Root Mean Square Error (RMSE), the two proposed confinement ultimate conditions presents a good performance compared to the major existing models except the models of Lam and Teng (2003) and Youssef et al. (2007) which have relatively similar performance to the proposed models.

Numerical analysis of thermal post-buckling strength of laminated skew sandwich composite shell panel structure including stretching effect

  • Katariya, Pankaj V.;Panda, Subrata Kumar
    • Steel and Composite Structures
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    • 제34권2호
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    • pp.279-288
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    • 2020
  • The computational post-buckling strength of the tilted sandwich composite shell structure is evaluated in this article. The computational responses are obtained using a mathematical model derived using the higher-order type of polynomial kinematic in association with the through-thickness stretching effect. Also, the sandwich deformation behaviour of the flexible soft-core sandwich structural model is expressed mathematically with the help of a generic nonlinear strain theory i.e. Green-Lagrange type strain-displacement relations. Subsequently, the model includes all of the nonlinear strain terms to account the actual deformation and discretized via displacement type of finite element. Further, the computer code is prepared (MATLAB environment) using the derived higher-order formulation in association with the direct iterative technique for the computation of temperature carrying capacity of the soft-core sandwich within the post-buckled regime. Further, the nonlinear finite element model has been tested to show its accuracy by solving a few numerical experimentations as same as the published example including the consistency behaviour. Lastly, the derived model is utilized to find the temperature load-carrying capacity under the influences of variable factors affecting the soft-core type sandwich structural design in the small (finite) strain and large deformation regime including the effect of tilt angle.

Novel Fungal Species Belonging to the Genus Acaulium Isolated from Riptortus clavatus (Heteroptera: Alydidae) in Korea

  • Lee, Ju-Heon;Ten, Leonid N.;Lee, Seung-Yeol;Jung, Hee-Young
    • 한국균학회지
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    • 제49권4호
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    • pp.477-486
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    • 2021
  • A survey of insect-associated fungi in Korea revealed a novel fungal strain isolated from the bean bug Riptortus clavatus (Heteroptera: Alydidae). Culturally and morphologically, the fungal strain designated KNUF-20-INY03, shares features with members of the genus Acaulium. Phylogenetic analyses based on the concatenated nucleotide sequences of the internal transcribed spacer regions (ITS) regions and partial sequences of the translation elongation factor 1-alpha (TEF1-α), and β-tubulin (β-TUB), and large subunit of the nuclear ribosomal RNA (LSU) genes showed that the isolate is part of a clade that includes other Acaulium species, but it occupies a distinct phylogenetic position. Based on the shape, size, and color of its conidia and conidiogenous cells, strain KNUF-20-INY03 is readily distinguishable from the closely related A. acremonium, A. albonigrescens, A. caviariformis, A. pannemaniae, and A. retardatum. The conidial length-to-width ratio (1.6) of the novel isolate is significantly lower than that of A. acremonium (1.9), A. albonigrescens (2.4), and A. pannemaniae (2.4), and KNUF-20-INY03 produces hyaline conidia and elliptical conidiogenous cells while A. caviariformis forms brown conidia and A. retardatum produces flask-shaped conidiogenous cells. Thus, both phylogenetic and morphological analyses indicate that this strain is a novel species in the genus Acaulium, and we propose the name Acaulium microspora sp. nov.

Response of a laterally loaded pile group due to cyclic loading in clay

  • Shi, Jiangwei;Zhang, Yuting;Chen, Long;Fu, Zhongzhi
    • Geomechanics and Engineering
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    • 제16권5호
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    • pp.463-469
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    • 2018
  • In offshore engineering, lateral cyclic loading may induce excessive lateral movement and bending strain in pile foundations. Previous studies mainly focused on deformation mechanisms of single piles due to lateral cyclic loading. In this paper, centrifuge model tests were conducted to investigate the response of a $2{\times}2$ pile group due to lateral cyclic loading in clay. After applying each loading-unloading cycle, the pile group cannot move back to its original location. It implies that residual movement and bending strain are induced in the pile group. This is because cyclic loading induces plastic deformation in the soil surrounding the piles. As the cyclic load increases from 62.5 to 375 kN, the ratio of the residual to the maximum pile head movements varies from 0.30 to 0.84. Moreover, the ratio of the residual to the maximum bending strains induced in the piles is in a range of 0.23 to 0.82. The bending strain induced in the front pile is up to 3.2 times as large as that in the rear pile. Thus, much more protection measures should be applied to the front piles to ensure the serviceability and safety of pile foundations.

Numerical calculation and test of the composite materials under dynamic loading

  • Liu, Fei;Li, Lianghui
    • Steel and Composite Structures
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    • 제38권1호
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    • pp.79-86
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    • 2021
  • Due to the complex geological conditions, a large number of high quality coal seams was buried in the western of China which cannot be mining in open-pit methods. The dynamic properties of that coal cannot be studied easily in real site for the complex working condition. The compound coal blocks made on the basis of the real situation were studied in the laboratory. The physical and mechanical properties of the compound coal blocks and the raw coal were contrasted by using the UCS tests. The results show that the compound coal blocks made by mixing coal powder, cement and water in proportion of 2.5:2:1 are the closest to that of standard raw coal. Then the propagation of strain waves and crushing effects on the coal were studied in the compound coal blocks by using the super dynamic strain test system and the numerical calculated method of ANSYS/LS-DYNA. The results show that the diameter of the crushing zone in the compound coal blocks was similar to that in the numerical results. The fractures distribution in laboratory tests also has a similar trend to the calculation results. The measured strain waves at the distance of 50 cm, 100 cm, and 150 cm from the center of the charge are mainly concerned at -1.0×104 με and have a similar trend as that in the numerical simulation.

토종오리 대형종의 육성기 능력 (Performance of Growing Period of Large-Type Korean Native Ducks)

  • 홍의철;추효준;강보석;김종대;허강녕;이명지;황보종;서옥석;최희철;김학규
    • 한국가금학회지
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    • 제39권2호
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    • pp.143-149
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    • 2012
  • 본 시험은 토종오리 대형종의 육성기 성적을 조사하기 위해 수행하였다. 공시동물은 A와 B계통 대형종 토종오리에서 발생한 오리 병아리를 암수 각각 210수씩 선별하여 총 420수를 이용하였다. 시험설계는 계통에 따른 2처리구(A, B)와 성별에 따른 2처리구(암, 수)로 나누어 $2{\times}2$의 복합요인으로 총 4처리구, 처리구당 3반복, 반복당 35수씩 완전임의 배치하였다. 4처리구의 비교에서는 4주령 이후부터 B계통 수컷의 체중이 가장 높았다(P<0.05). 계통간의 비교에서는 전 주령에서 B계통이 A계통에 비해 높았으며(P>0.05), 암수 비교에서는 4주령 이후부터 수컷의 체중이 암컷에 비해 높았다(P<0.05). 4처리구의 0주령부터 8, 12, 16주령 및 20주령까지의 증체량은 B계통 수컷에서 가장 높았다(P<0.05). 계통간 비교에서는 전 기간에서 A와 B계통 사이에 차이가 없었으며, 암수 비교에서는 0~4주령에서 차이가 없었으나(P>0.05), 0주령부터 8, 12, 16 및 20주령까지는 수컷의 증체량이 암컷에 비해 높았다(P<0.05). 0주령부터 4주령, 12주령, 16주령 및 20주령까지의 누적사료 섭취량은 B계통 수컷에서 가장 높았다(P<0.05). 암수 비교에서는 0주령부터 12, 16 및 20주령까지는 수컷의 섭취량이 암컷에 비해 높았다(P<0.05). 4처리구의 사료 요구율은 0~4주령에서 B계통 수컷이 가장 높았고(P<0.05), 0~8주령 및 0~12주령에서는 A계통 암컷이 가장 높았다(P<0.05). 암수 비교에서는 0~8주령에암컷, 0~20주령에수컷의사료요구율이높았다(P<0.05). 이런 결과들은 토종오리 대형종의 육성 성적에 대한 기초적인 자료로서 이용될 것이라 사료된다.

Effect of axial stretching on large amplitude free vibration of a suspended cable

  • Chucheepsakul, Somchai;Wongsa, Sanit
    • Structural Engineering and Mechanics
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    • 제11권2호
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    • pp.185-197
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    • 2001
  • This paper presents the effect of axial stretching on large amplitude free vibration of an extensible suspended cable supported at the same level. The model formulation developed in this study is based on the virtual work-energy functional of cables which involves strain energy due to axial stretching and work done by external forces. The difference in the Euler equations between equilibrium and motion states is considered. The resulting equations govern the horizontal and vertical motion of the cables, and are coupled and highly nonlinear. The solution for the nonlinear static equilibrium configuration is determined by the shooting method while the solution for the large amplitude free vibration is obtained by using the second-order central finite difference scheme with time integration. Numerical examples are given to demonstrate the vibration behaviour of extensible suspended cables.