• Title/Summary/Keyword: Strain Capacity

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Effect of Cooling Rate on Damping Capacity of Magnesium (마그네슘의 진동감쇠능에 미치는 냉각 속도의 영향)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.30 no.6
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    • pp.258-263
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    • 2017
  • The effect of cooling rate on the damping capacity of pure Mg was studied. Two Mg samples with different cooling rates were prepared by heat treatment at 873 K for 24 h, followed by water quenching and by furnace cooling to room temperature, respectively. The average grain sizes of the Mg samples were almost identical regardless of the cooling rate, but more twins were observed in the sample with faster cooling rate. The calculated vacancy fraction was higher in the fast cooling sample than the slow cooling one. It is noted that the fast cooling sample exhibited lower damping capacity both in the strain-amplitude independent and strain-amplitude dependent regions. Higher values of vacancy concentration and number density of twins in the fast cooling sample are considered to be responsible for the deteriorated damping capacity in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

Strain Amplitude Dependence of Damping Capacity in Mg-AI-Si Alloy (Mg-Al-Si 합금에서 진동감쇠능의 변형진폭 의존성)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.24 no.3
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    • pp.144-148
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    • 2011
  • Change in damping capacity with strain amplitude was studied in Mg-Al-Si alloy in as-cast, solution-treated and aged states, respectively. The as-cast microstructure of the alloy is characterized by eutectic ${\beta}$($Mg_{17}Al_{12}$) phase and Chinese script type $Mg_2Si$ particles. The solution treatment dissolved the ${\beta}$ phase into the matrix, while the aging treatment resulted in the distribution of continuous and discontinuous type ${\beta}$ precipitates. The solution-treated microstructure showed better damping capacity than as-cast and aged microstructures both in strain-dependent and strain-independent damping regions. The decrease in second-phase particles which weakens the strong pinning points on dislocations and distribution of solute atoms in the matrix, would be responsible for the enhanced damping capacity after solution treatment.

Effect of ε Martensite Content and Strain Amplitude on Damping Capacity of Fe-17%Mn Alloy (Fe-17%Mn 합금의 진동감쇠능에 미치는 ε 마르텐사이트 함량과 진폭변형율의 영향)

  • Jun, Joong-Hwan;Lee, Young-Kook;Choi, Chong-Sool
    • Journal of the Korean Society for Heat Treatment
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    • v.9 no.2
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    • pp.112-120
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    • 1996
  • The effects of ${\varepsilon}$ martensite content and strain amplitude on damping capacity of an Fe-17%Mn alloy have been studied to establish damping mechanism of Fe-Mn system corresponding to the magnitude of strain amplitude. In a range of $1{\times}10^{-4}{\sim}3{\times}10^{-4}$ strain amplitude, the damping capacity is linearly proportional to the ${\varepsilon}$ martensite content, which suggests that stacking faults and ${\varepsilon}$ martensite variant boundaries are the principal damping sources. In the range of $4{\times}10^{-4}{\sim}6{\times}10^{-4}$ strain amplitude, however, a maximum damping capacity is observed around 68 vol.% ${\varepsilon}$. This behavior is very similar to dependence of relative area of ${\gamma}/{\varepsilon}$ interface on ${\varepsilon}$ martensite content. This means that in this strain range, ${\gamma}/{\varepsilon}$ interface acts as damping source in addition to the stacking faults and variant boundaries in Fe-17%Mn alloy.

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An Experimental Study on the Engineering Properties of HPFRCC According to Kinds, Shapes and Volume Fraction of Fibers (섬유의 종류, 형상 및 치환율에 따른 HPFRCC의 공학적 특성에 관한 실험적 연구)

  • 김영덕;조봉석;김재환;김규용;최경렬;김무한
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2003.05a
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    • pp.59-62
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    • 2003
  • Kinds, shapes and fraction ratios of fibers have influence on properties of HPFRCC(High-Performance Fiver Reinforced Cementitious Concrete ) like bending strength, strain capacity and fracture toughness. For example, hydrophilic fibers have different chemical bond strength from hydrophobic fibers, fiber shapes influence on fiber pull-out and rupture, and fiber volume fraction influence on bending strength. In this study, to estimate influences of kinds, shapes and fraction ratios of fibers, we make HFRCC with 3 kind of fiber in various volume fraction of fiber and compare cracking, bending strength and fracture toughness. As the results, bending strength of HPFRCC was increased as fiber volume fraction was Increase and fiber tensile strength was increase, and strain capacity and fracture toughness of HFRCC was higher in fiber pull-out fracture than in fiber rupture fracture. And HFRCC showing pseudo strain hardening has higher fiber reinforce efficiency than others.

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Modeling of heated concrete-filled steel tubes with steel fiber and tire rubber under axial compression

  • Sabetifar, Hassan;Nematzadeh, Mahdi;Gholampour, Aliakbar
    • Computers and Concrete
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    • v.29 no.1
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    • pp.15-29
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    • 2022
  • Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750℃ temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750℃ exhibits a higher load bearing contribution compared to those under 20, 250, and 500℃. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%.

A Study on the Section Design of FRP-Concrete Composite Slabs Considering Failure Behaviors (파괴 거동을 고려한 FRP-콘크리트 합성 바닥판의 단면 설계에 관한 연구)

  • 조근희;김병석;이영호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.641-646
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    • 2002
  • FRP-concrete composite slab is consisted of brittle materials and then shows brittle failure mechanism. This study suggests a new design approach that FRP-concrete composite slab leads to ductile failure, and investigates their failure behaviors for two types of section by numerical analysis. Box-type section is higher than I-type section in load capacity to required FRP quantity. Each section was designed so that the strain of FRP plate is 50% to its ultimate strain on initiation of concrete crushing, and it is verified that displacement ductility is more than two. Ductility capacity can be improved by reducing the strain of FRP on initiation of concrete crushing, but as the strain of FRP is reduced load capacity to required FRP quantity is also reduced. Therefore section optimization study is needed considering safety and economical efficiency.

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Mechanical Properties of Aluminium Alloy with Cellular Structure. (미세기공 알루미늄 소재의 기계적 성질)

  • 윤성원;이승후;강충길
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.695-698
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    • 2002
  • Induction heating process is one of the most efficient heating process in terms of temperature control accuracy and heating time saving. In the past study, fabrication process of cellular 6061 alloys by powder metallurgical route and induction heating process was studied. To supplement the framing conditions that studied in past study, effect of induction heating capacity and holding time at foaming temperature were investigated. Under the achieved framing conditions, teamed 6061 alloys were fabricated for variation of foaming temperature, and porosities(%)-foaming temperature curves were obtained by try-error experimental method. Uniaxial compression tests were performed to investigate the relationship between porosities(%) and stress-strain curves of framed 6061 alloy. Also, energy absorption capacity and efficiency were calculated from stress-strain curves to investigated. Moreover, dependence of plateau stress on strain rate was investigated in case of cellular 6061 alloy with low porosities(%)

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A Plan to Develop Seismic Capacity Verification Procedures Based on the Elastic-Plastic Strain Features (탄소성 변형률 기반 내진성능 평가 절차서 개발 방안)

  • Hwang, Jong Keun;Jeong, Ill Seok;Kim, Beom Shig;Ahn, Sang Won;Bang, Hye Jin;Lee, Min Hee;Jeong, Hyeon Seob
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.14 no.2
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    • pp.11-15
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    • 2018
  • A development plan for seismic capacity verification procedures of nuclear components based on the elastic-plastic strain (EPS) features is explained in this paper. The EPS methodology is more realistic to assess seismic responses of components to extreme seismic events beyond the safe shutdown earthquake (SSE) than current practices with the criteria of stress limits. The EPS based approach to analyze the seismic capacity of components can reduce over-conservatism in the current stress-based criteria and can incorporate the seismic responses of components deformed in plastic behavior by the motion of extreme earthquake.

Yield penetration in seismically loaded anchorages: effects on member deformation capacity

  • Tastani, S.P.;Pantazopoulou, S.J.
    • Earthquakes and Structures
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    • v.5 no.5
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    • pp.527-552
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    • 2013
  • Development of flexural yielding and large rotation ductilities in the plastic hinge zones of frame members is synonymous with the spread of bar reinforcement yielding into the supporting anchorage. Yield penetration where it occurs, destroys interfacial bond between bar and concrete and reduces the strain development capacity of the reinforcement. This affects the plastic rotation capacity of the member by increasing the contribution of bar pullout. A side effect is increased strains in the compression zone within the plastic hinge region, which may be critical in displacement-based detailing procedures that are linked to concrete strains (e.g. in structural walls). To quantify the effects of yield penetration from first principles, closed form solutions of the field equations of bond over the anchorage are derived, considering bond plastification, cover debonding after bar yielding and spread of inelasticity in the anchorage. Strain development capacity is shown to be a totally different entity from stress development capacity and, in the framework of performance based design, bar slip and the length of debonding are calculated as functions of the bar strain at the loaded-end, to be used in calculations of pullout rotation at monolithic member connections. Analytical results are explored parametrically to lead to design charts for practical use of the paper's findings but also to identify the implications of the phenomena studied on the detailing requirements in the plastic hinge regions of flexural members including post-earthquake retrofits.

Experimental Evaluation of Seismic Performance of Laminated Elastomeric Bearing and Lead-Rubber Bearing (적층고무베어링과 납-고무베어링의 내진 성능에 관한 실험적 평가)

  • 김대곤;이상훈;김대영;박칠림
    • Journal of the Earthquake Engineering Society of Korea
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    • v.2 no.4
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    • pp.53-62
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    • 1998
  • Experimental studies for the laminated elastomeric bearing and the lead-rubber bearing, those are often used to improve the seismic capacity of the structures recently, are conducted to evaluate the seismic capacity of the bearings. The shear stiffness of the bearings decreases as the shear strain amplitude or the constant axial load level increases, but not sensitive to the strain rates effect. Bearings are strong for the axial compression but weak for the axial tension.

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