• 제목/요약/키워드: Effective Strain

검색결과 1,805건 처리시간 0.027초

Inconel 706의 열간단조 공정 중 재가열과 변형양에 따른 결정립 미세화에 대한 분석 (Analysis of Microstructural Refinement for Inconel 706 during Hot Forging Process through Reheating and Strain)

  • 성상규;강현준;이영선;이상용;이의종;제환일;신정호;윤은유
    • 소성∙가공
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    • 제32권5호
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    • pp.239-246
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    • 2023
  • To reduce the forming load due to the temperature drop, during the hot forging process, a reheating hot forging process design is required that to repeat heating and forging. However, if the critical strain required for recrystallization is not induced during forging and grain growth becomes dominant due to the reduction in dislocation density due to repeated heating, the mechanical properties may deteriorate. Therefore, in this study, Inconel 706 alloy was applied, and the grain refinement behavior was comparatively analyzed according to the number of reheating times and effective strain during reheating hot forging process. Reheating was carried out with a total compression rate of 40% up to 4 times. The Inconel 706 compression test specimens heated once showed finer grains as the effective strain increased due to the dynamic recrystallization phenomenon. However, as the number of heating increases, grain refinement was observed even in a low effective strain distribution of 0.43 due to static recrystallization during reheating. Moreover, grain growth occurs at a relatively low effective strain of 0.43 when the number of reheating is four or more. Therefore, it was effective to apply an effective strain of 0.43 or more during hot forging to Inconel 706 in order to induce crystallization through grain refinement and improve the properties of forged products. In addition, we could notice that up to three reheating times condition was appropriate to prevent grain growth and maintain fine grain size.

SCM 440 강재의 동적 재결정 조직 변화에 관한 연구 (The Evolution of Dynamically Recrystallized Microstructure for SCM 440)

  • 한형기;유연철
    • 소성∙가공
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    • 제10권1호
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    • pp.35-41
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    • 2001
  • The high temperature deformation behavior of SCM 440 can be characterized by the hot torsion test in the temperature ranges of $900^{\circ}C$~$1100^{\circ}C$ and strain rate ranges of 0.05/sec~5/sec. The aim of this paper is to establish the quantitative equation of the volume fraction of dynamic recrystallization (DRX) as a function of processing variables, such as strain rate ($\varepsilon$), temperature (T), and strain ('$\varepsilon$). During hot deformation, the evolution of microstructure could be analyzed from work hardening rate ($\theta$). For the exact prediction of dynamic softening mechanism the critical strain ($\varepsilon_c$), the strain for maximum softening rate ($\varepsilon^*$ and Avrami' exponent (m') were quantitatively expressed by dimensionless parameter, Z/A, respectively. The transformation-effective strain-temperature curve for DRX could be composed. It was found that the calculated results were agreed with the experimental data for the steel at any deformation conditions.

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Strain interaction of steel stirrup and EB-FRP web strip in shear-strengthened semi-deep concrete beams

  • Javad Mokari Rahmdel;Erfan Shafei
    • Steel and Composite Structures
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    • 제47권3호
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    • pp.383-393
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    • 2023
  • Conventional reinforced concrete design codes assume ideal strain evolution in semi-deep beams with externally bonded fiber-reinforced polymer (EB-FRP) web strips. However, there is a strain interaction between internal stirrups and web strips, leading to a notable difference between code-based and experimental shear strengths. Current study provides an experiment-verified detailed numerical framework to assess the potential strain interaction under quasi-static monotonic load. Based on the observations, steel stirrups are effective only for low EB-FRP amounts and the over-strengthening of semi-deep beams prevents the stirrups from yielding, reducing its shear strength contribution. A notable difference is detected between the code-based and the study-based EB-FRP strain values, which is a function of the normalized FRP stress parameter. Semi-analytical relations are proposed to estimate the effective strain and stress of the components considering the potential strain interaction. For the sake of simplification, a linearized correction factor is proposed for the EB-FRP web strip strain, assuming its restraining effect as constant for all steel stirrup amounts.

Lateral strain-axial strain model for concrete columns confined by lateral reinforcement under axial compression

  • Hou, Chongchi;Zheng, Wenzhong
    • Structural Engineering and Mechanics
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    • 제84권2호
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    • pp.239-251
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    • 2022
  • The use of lateral reinforcement in confined concrete columns can improve bearing capacity and deformability. The lateral responses of lateral reinforcement significantly influence the effective confining pressure on core concrete. However, lateral strain-axial strain model of concrete columns confined by lateral reinforcement has not received enough attention. In this paper, based on experimental results of 85 concrete columns confined by lateral reinforcement under axial compression, the effect of unconfined concrete compressive strength, volumetric ratio, lateral reinforcement yield strength, and confinement type on lateral strain-axial strain curves was investigated. Through parameter analysis, it indicated that with the same level of axial strain, the lateral strain slightly increased with the increase in the unconfined concrete compressive strength, but decreased with the increase in volumetric ratio significantly. The lateral reinforcement yield strength had slight influence on lateral strain-axial strain curves. At the same level of lateral strain, the axial strain of specimen with spiral was larger than that of specimen with stirrup. Furthermore, a lateral strain-axial strain model for concrete columns confined by lateral reinforcement under axial compression was proposed by introducing the effects of unconfined concrete compressive strength, volumetric ratio, confinement type and effective confining pressure, which showed good agreement with the experimental results.

콕스밀에서 평균변형율, 압하력, 단면감소율에 대한 수식모델개발 (Development of Online Model for Mean Effective Strain, Roll Force and Area Reduction in Bar Rolling with Three Rolls)

  • 제상현;황상무
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2001년도 추계학술대회 논문집
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    • pp.162-165
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    • 2001
  • In industrial practice, caliber design in shape rolling depends on the designer's experience, which in general is obtained through costly trial-and error process. on-line model which is relations of mean effective strain, roll force and area reduction is derived from finite element process simultion in bar rolling with three rolls.

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Impact of Strain Effects on Hole Mobility and Effective Mass in the p-Channel Nanowire Cross-Section

  • Jang, Geon-Tae
    • EDISON SW 활용 경진대회 논문집
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    • 제6회(2017년)
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    • pp.424-427
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    • 2017
  • This study investigated the effect of strain on hole mobility and hole effective mass in a p-channel rectangular nanowire with two-dimensional confinement. We obtained the valence energy band structure using the six-band k.p method and calculated the mobility and effective mass of the hole in the [100] direction taking the strain effect into account in the inversion region. The hole mobility of strained silicon was calculated using Kubo-Greenwood formalism. As a result, it showed good performance compared to relaxed silicon, but its magnitude was insignificant.

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Strength model for square concrete columns confined by external CFRP sheets

  • Benzaid, Riad;Mesbah, Habib Abdelhak
    • Structural Engineering and Mechanics
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    • 제46권1호
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    • pp.111-135
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    • 2013
  • An experimental study has been carried out on square plain concrete (PC) and reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. A total of 78 specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. Slenderness of the columns, number of wrap layers and concrete strength were the test parameters. Compressive stress, axial and hoop strains were recorded to evaluate the stress-strain relationship, ultimate strength and ductility of the specimens. Results clearly demonstrate that composite wrapping can enhance the structural performance of square columns in terms of both maximum strength and ductility. On the basis of the effective lateral confining pressure of composite jacket and the effective FRP strain coefficient, new peak stress equations were proposed to predict the axial strength and corresponding strain of FRP-confined square concrete columns. This model incorporates the effect of the effective circumferential FRP failure strain and the effect of the effective lateral confining pressure. The results show that the predictions of the model agree well with the test data.

경도-유효변형률 관계에 관한 유한요소 해석 (Finite Element Analysis for the Relation between Hardness and Effective Strain)

  • 권순구;박준홍
    • 한국산업융합학회 논문집
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    • 제2권2호
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    • pp.125-130
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    • 1999
  • It is already known that hardness value of cold-forged product is in close conjunction with its effective strain. This paper presents the method to predict the relation between effective strains and hardness values by using FE-simulation of hardness test from the conception that hardness indicates resistance to plastic deformation. The results of FE-simulation for the material with pre-strain arc compared with those of experiments of the references to show the feasibility of the proposed method.

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탄소섬유복합체로 보강된 RC부재의 보강재 강성에 따른 휨 보강성능 (Flexural Performance of RC Beams Strengthened with Diffrent Amount of CFRP Composite)

  • 유영찬;최기선;김긍환
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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    • pp.129-132
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    • 2006
  • It is generally reported that most of RC beams strengthened with simply bonded FRP composite is failed by FRP debonding. Also, the flexural performance of RC member strengthened with FRP composite can be calculated using the effective strain of FRP. The effective strain as a result of the debonding failure depends on many variables, such as FRP stiffness including the thickness($t_f$) and modulus of elasticity($E_f$), the amount of FRP but the FRP stiffness is reportedly the most influential. The purpose of this paper, therefore, is to examine effects of FRP stiffness on the flexural strengthening of RC beams. 4 different stiffness of CFRP composite including CFRP sheet and laminae were selected. From the tests, it was found that the flexural performance of RC beams strengthened with CFRP composite can be calculated based on the effective strain of the CFRP composite and the effective strain is inversely proportional to the CFRP stiffness.

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모델재를 이용한 축대칭 평금형 압출공정의 변형가시화 해석 (A Visioplasticity Analysis for Axisymmetric Extrusion through Square Dies Using Model Material)

  • 한철호;엄태복
    • 소성∙가공
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    • 제5권2호
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    • pp.156-164
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    • 1996
  • To investigate the behavior of plastic deformation in axisymmetric extrusion through square dies, experimental works with the plasticine as a model material are carried out at the room temperature. Some mechanical properties of the model material are determined by compression and ring compression tests. Visioplasticity method using expermental grid distortion in extrusion is introduced to analyze the plastic flow strain rate and strain distribution. In spite of severe deformation during the extrusion through square die the visioplasticity method shows good results for the distribution of effective strain rate and effective strain.

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