Tests and Analysis on Thermal Expansion Behaviour of Steel Strand used in Prestressed Concrete Structure under Low Temperatures

Jian Xie,Jia-Bao Yan 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.1

This paper presents the results of the tests and analysis on the coefficient of thermal expansion for the steel strand under combined low temperatures and prestressing forces. A test program was firstly carried out to study the thermal expansion behaviour of the seven-wire strand under combined different low temperatures ranging from 20 to - 165 °C and different prestressing levels ranging from 0 to 0.75 ft/ftk. The test results exhibited the thermal expansion behaviours of the steel strand under low temperatures in terms of thermal strain versus temperature curves, transit linear thermal expansion coefficient, and average thermal expansion coefficient. The influences of the low temperature and prestressing levels on the thermal expansion behaviours of the steel strand were separately discussed and analysed. Based on the test data, mathematical models were developed to predict the thermal expansion coefficients including transit and average of the steel strand. The developed regression models fully considered the influences of the low temperature and prestressing stresses acted on the strand. Finally, design equations were proposed to predict the transit and average thermal expansion coefficient of the steel strand under combined low temperature and prestressing forces.

폐유리 잔골재 혼합 시멘트 콘크리트의 혼화재 치환에 따른 열팽창 특성

김유경,이재훈,이재훈,김연태,정진훈 한국도로학회 2022 한국도로학회논문집 Vol.24 No.6

PURPOSES : The purpose of this study is to confirm the thermal expansion characteristics of concrete mixed with 1% waste glass fine aggregates, which is the amount stipulated for recycled aggregates in the current quality standard. METHODS : The coefficient of thermal expansion was measured by applying AASHTOT 336-10 using a LVDT. The results measured were used as physical properties in a finite element analysis to confirm the change in tensile stress and the displacement of the right angle section of the upper slab of a concrete pavement due to admixture substitution. RESULTS : The thermal expansion coefficients of concrete based on the replacement rate of the admixture when the waste glass fine aggregates are replaced are within the range of the thermal expansion coefficients of concrete specified in the Federal Highway Administration report. As the replacement rate of the admixture increases, the thermal expansion coefficient of concrete decreases. As the thermal expansion coefficient decreases, the slab pavement curling displacement and the tensile stress of the center of the upper slab of concrete decrease. CONCLUSIONS : In the short term, the presence or absence of waste glass fine aggregates does not significantly affect the thermal expansion coefficient of concrete. However, in the long term, waste glass fine aggregates are reactive aggregates that causes ASR, which creates an expandable gel around the aggregates and results in concrete expansion. Therefore, the relationship between ASR and the thermal expansion coefficient must be analyzed in future studies.

Effect of Carbon on the Coefficient of Thermal Expansion of As-Cast Fe-30wt.%Ni-12.5wt.%Co-xC Invar Alloys

Kim, Bong-Seo,Yoo, Kyung-Jae,Kim, Byung-Geol,Lee, Hee-Woong 대한금속학회 2002 METALS AND MATERIALS International Vol.8 No.3

The segregation (distribution) of nickel and the composition of its constituents influence the low thermal expansion characteristics (Invar effect) in Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy. The change of coefficient of the thermal expansion and magnetic properties were studied as an aspect of carbon addition causing the segregation of Ni in primary austenite of as-cast Fe-30 wt.% Ni-12.5 wt.% Co Invar alloy. The coefficient of thermal expansion of Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy showed its lowest value at 0.08 wt.% carbon, increased with increasing carbon content in the range of 0.08∼1.0 wt.%C, kept constant at 1.0∼2.0 wt.%C and decreased at carbon higher than 2.0 wt.%. The effective distribution of the coefficient of nickel in as-cast Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy increased with increasing carbon content. The volume fraction of they phase of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy increased with increasing carbon content. The microstructure of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy changed with the carbon content was independent of the coefficient of thermal expansion. The Curie temperature changed linearly with the carbon content and was similar to the change of the coefficient of thermal expansion. Moreover, the coefficient of thermal expansion decreased when the ratio of saturation magnetization to Curie temperature (σ_s/T_c) increased, decreasing the Curie temperature and showed a specific relationship with the magnetic properties of the Fe-30 wt.% Ni-12.5 wt.% Co-xCInvar alloy.

열 변형 해석을 위한 허니컴 샌드위치 평판의 물성치 예측에 관한 연구

홍석민(Seok-min Hong),변재기(Jae-ki Byun),최지원(Ji-won Choi),최영돈(Young-don Choi) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

Thermal problem that is directly related to the lifetime of electronic device is becoming increasingly important due to the miniaturization of electronic device. In order to solve these problems, thermal stability studies through the thermal diffusion and insulation are required. Therefore using lamination consisting of different materials or composite for getting anisotropic thermal properties is inevitable. However, using lamination causes thermal deformation because of the different coefficient of thermal expansion. Thus, in order to solve thermal problem, thermal deformation must be considered. Honeycomb sandwich plate has anisotropic thermal conductivity. To analyze thermal deformation of system that applies the honeycomb sandwich plate, thermal and elastic properties are needed. In this study, thermal and elastic properties of honeycomb sandwich plate are predicted such as coefficient of thermal expansion, elastic modulus, poisson’s ratio, shear modulus. Because properties of honeycomb sandwich plate vary according to Hexagon size, thickness and the material properties.

딥러닝을 통한 광용적맥파 복원에 관한 연구

이민형(Min-Hyung Lee),김경호(Kyoung-Ho Kim) 대한전기학회 2022 대한전기학회 학술대회 논문집 Vol.2022 No.1

전부도재관 제작용 침투유리의 열팽창계수의 결정

김병수,이득용,김학관,장주웅 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.1

치과용 재료를 포함한 생체재료로 각광을 받고 있는 알루미나-유리복합체에 사용되는 유리침투재의 적정 조성은 열팽창계수가 중요 인자로, 적합한 열팽창계수를 가지는 적정 조성 유리 개발을 효율적으로 달성하기 위하여 다구치 실험계획법을 도입하였다. 이러한 방법을 이용하여 유리 침투재의 열팽창에 가장 많은 영향을 미치는 알칼리 산화물과 알칼리 토류 산화물의 영향을 관찰하였다. 치과용 유리침투재의 제성분들을 고려할 때 유리의 열팽창계수에 미치는 영향은 $Na_2$O≫K$_2$O≫MgO≒CaO의 순서로 $Na_2$O의 영향력은 MgO, CaO의 약 8배로 나타났으며 $K_2$O의 영향력은 MgO, CaO의 약 4배로 계산되었다. 또 각 인자간의 교호작용(interaction affects) 중 $K_2$O-CaO의 교호 작용이 가장 유의하게 나타났으며 각 인자와 교호 작용의 수준별 기여율을 계산하여 특성 조성의 열팽창 특성치를 예측하였다. Using alumina-glass infiltrated material which has been in the spotlight of biomaterials including dental material, appropriate composition of glass infiltrated material mainly depends on the thermal expansion coefficient. To obtain proper compositional glass of suitable thermal expansion coefficient effiiently. a Taguchi analysis was conducted. The influence of alkali oxide and alkali earths oxide, which affect mostly the thermal expansion coefficient of glass infiltrated material, was infiltrated material, the effect having influenced on the thermal expansion coefficient of glass was presented in this order (Na$_2$O≫K$_2$O ≫MgO≒CaO). The effect of Na$_2$O was about eight times as great as the effects of MgO, CaO and $K_2$O was about four times. Among the interaction affects of each variables the interaction affects of $K_2$O-CaO showed most significantly and thermal expansion property of specified composition was predicted by calculating contribution rate on each level of variables and interaction affects.

Thermal Strain Analysis of Composite Materials by Electronic Speckle Pattern Interferometry

Kim, Koung-Suk,Jang, Wan-Shik,Hong, Myung-Seak,Kang, Ki-Soo,Jung, Hyun-Chul,Kang, Young-Jun,Yang, Sung-Pil The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.5

This study discusses a non-contact optical technique (electronic speckle pattern interferometry) that is well suited for thermal deformation measurement without any surface preparation and compensating process. Fiber reinforced plastics ($[0]_{16},\;[0/90]_{8S}$) were analyzed by ESPI to determine their thermal expansion coefficients. The thermal expansion coefficient of the transverse direction of a uniaxial composite is evaluated as $48.78{\times}10^{-6}(1/^{\circ}C)$. Also, the thermal expansion coefficient of the cross-ply laminate $[0/90]_{8S}$ is numerically estimated as $3.23{\times}10^{-6}(1/^{\circ}C)$ that is compared with that measured by ESPI.

Energy Partitioning Approach를 이용한 Solder Joint의 열 피로 수명 예측

오재응(Jaeeung Oh),강원호(Wonho Kang),이해진(Haejin Lee),안영찬(Youngchan Ahn),이정윤(Jungyoun Lee),신승우(Seungwoo Shin) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Thermal fatigue of solder joints is critical to electronic package performance and service life. The electronic package are composed of different materials, thermal stresses generate at near the interface, such as solder joints due to the differences of thermal expansion coefficients. Results of thermal stress-strain occur thermal fatigue fracture at the interface of different materials. The represent study established finite element analysis to determine the stress and strain history in the solder, due to thermal cycling. The computed stress and strain histories are utilized to construct hysteresis plots at each location in the solder joint. The hysteresis plots are then partitioned into elastic strain energy, plastic work and creep work dissipation. The fatigue life of the solder joint is then estimated through an energy partitioning analysis.

A measurement of thermal expansion-contraction characteristics of stainless steel using hightemperature digital image correlation method

레빈퉁,하넉산,구남서,전호찬 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4

고온환경에서의 재료의 열적 성능은 고속 비행차량의 열구조 설계에 매우 중요하다. 이 연구에서의 측정방법은 재료의 열적 물리특성과 재료의 거동이 고온에서 비접촉 전영역 고온기법 측정방법을 이용하여 구축되였다. 이 측정방법은 적외선 가열 장치를 채용하여 스테인레스 스틸(s304) 샘플을 590℃ 가열하였다. 다양한 온도에서의 열적 부하로 인한 샘플표면의 이미지는 CCD 카메라를 사용하여 기록되였다. 그리고 샘플의 전영역 열변형은 디지털 영상 상관(DIC)을 이용하여 측정되였고 터멀 팽창계수(CTE) 및 수축계수 결과는 존재한 값과 비교할것이다. 비교에 의하면 CTE 는 핸드북에서 사용할수 있는 값과 접근했다. 결과에 의하면 DIC 는 기계 및 항공 우주 공학에서 전영역 고온 열변형을 측정하는것에 아주 효율적이고 정확적이였다는 것을 알수 있다. Thermal performance of materials in high-temperature environments is important for thermal-structural design of highspeed flight vehicle. In this study, the measurement method for thermal physical properties of material and the behavior of material at high temperature were established, using a non-contact and full-filed high-temperature measurement technique. This technique employs an infrared radiation heating device to heat a stainless steel (S304) sample up to 590℃. The images of the sample surface due to thermal load at various temperatures were recorded using CCD cameras. Afterwards, full-field thermal deformation of the sample was determined using digital image correlation (DIC). The results of the coefficient of thermal expansion (CTE) and contraction will be compared with exist values. According to a comparison, CTE were close to the values available in handbook. The results reveal that DIC is an effectiveness and accuracy for measuring full field high-temperature thermal deformation in mechanical and aerospace engineering.

그래핀의 페르미온 개스에 의한 열팽창계수

임국형 ( Gukhyung Ihm ) 충남대학교 기초과학연구원 2018 충남과학연구지 Vol.35 No.1

We present the thermal expansion coefficient of Fermi gas in graphene. We use the Sommerfeld expansion method to obtain the heat capacity and the relation between chemical potential and electron density, which are crucial in determining the thermal expansion coefficient. As a result, in contrast to ordinary two dimensional electron systems, the compressibility of graphene has been shown to have non-linear temperature dependence. The possibility of negative thermal expansion coefficient are also discussed in accordance with recent experiments.