• Title, Summary, Keyword: Creep Analysis

Search Result 582, Processing Time 0.032 seconds

Crack Tip Creep Deformation Behavior in Transversely Isotropic Materials (횡방향으로 등방성인 재료에서 균열선단 크리프 변형 거동)

  • Ma, Young-Wha;Yoon, Kee-Bong
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.33 no.12
    • /
    • pp.1455-1463
    • /
    • 2009
  • Theoretical mechanics analysis and finite element simulation were performed to investigate creep deformation behavior at the crack tip of transversely isotropic materials under small scale creep (SCC) conditions. Mechanical behavior of material was assumed as an elastic-$2^{nd}$ creep, which elastic modulus ( E ), Poisson's ratio ( ${\nu}$ ) and creep stress exponent ( n ) were isotropic and creep coefficient was only transversely isotropic. Based on the mechanics analysis for material behavior, a constitutive equation for transversely isotropic creep behavior was formulated and an equivalent creep coefficient was proposed under plain strain conditions. Creep deformation behavior at the crack tip was investigated through the finite element analysis. The results of the finite element analysis showed that creep deformation in transversely isotropic materials is dominant at the rear of the crack-tip. This result was more obvious when a load was applied to principal axis of anisotropy. Based on the results of the mechanics analysis and the finite element simulation, a corrected estimation scheme of the creep zone size was proposed in order to evaluate the creep deformation behavior at the crack tip of transversely isotropic creeping materials.

A Study on the Creep Analysis of Reinforced and Prestressed Concrete Structures Using Creep Recovery Function (크리프 회복식을 이용한 철근콘크리트 및 프리스트레이트 콘크리트 부재의 크리프 해석에 고나한연구)

  • 오병환;김세훈;양인환
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • /
    • pp.339-345
    • /
    • 1998
  • The creep of concrete structures caused by variable stresses is mostly calculated by step-by-step method based on the superposition of creep function. Although most practical application is carried out by this linear assumption, significant deviations between predictions and experiments have been observed when unloading takes place, that is, stress is reduced. The recovery is overestimated. The main purpose of this study is to present the application method of the creep analysis model which is expressed with both creep function and creep recovery function to concrete structures where is expressed with both creep function and creep recovery function to concrete structures where increase or decrease of stress is repeated . To apply two function method to time analysis of concrete structures, this study presents the calculation method of creep strain increment for stress variation. Then, this paper executes the time analysis for an example using suggested method, and compares theses results with the previous analysis values and experimental results.

  • PDF

Time-Dependent Analysis of Reinforced and Prestressed Concrete Structures Considering Tensile Creep of Concrete (인장크리프모델을 고려한 철근 및 프리스트레스트 콘크리트 구조의 시간의존적 해석)

  • 오병환;이형준
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • /
    • pp.473-479
    • /
    • 1996
  • Until now, we assumed in the time-dependent analysis of concrete structure that tensile creep has same characteristics as compressive creep has. But, in according to results of researches, it appears that tensile creep is different from compressive creep in quantity and in mechanics because tensile creep is affected significantly by micro cracking. The test results indicate that the creep behavior of concrete in compression and tension is rather different. The test data shows that the amount of creep under tensile loading is larger than that under compressive loading. In this paper, a realistic tensile creep model is suggested and incorporated in the formulation. In order to get more accurate results of time-dependent analysis. The present study indicates that the long-term deflection of concrete structures under realistic tensile creep model is somewhat larger than that under ordinary compressive creep model.

  • PDF

High Temperature Creep Behavior of Cr3C2 Composites (크롬-카바이드 복합체의 고온 크리프 거동)

  • 김지환;한동빈;김기태
    • Journal of the Korean Ceramic Society
    • /
    • v.32 no.11
    • /
    • pp.1219-1226
    • /
    • 1995
  • Creep behaviors of Cr3C2 composites containing 90 wt% Cr3C2 and 10 wt% Ni were studied at high temperature. Compression tests at 100$0^{\circ}C$ and bending tests at 100$0^{\circ}C$ and 105$0^{\circ}C$ were done in argon environment. In all test conditions primary and steady-state creep behaviors were observed. Stress exponent and activatiion energy were determined from the experimental data. By microstructural analysis of Cr3C2 composites after creep test, the separate agglomerations of Ni phase were observed. Numerical analysis was also studied to analyze bending creep behaviors of Cr3C2 by assumming different tensile and compressive creep behavior in a bending sample. From the analysis, it was found that the stress state at the compressive region as applied stress increased. The observed creep rates were compared with the predicted creep rates by estimating power-law creep parameters from bending test data.

  • PDF

Tensile Creep Model of Concrete Incorporation the Effects of Humidity and Time at Loading (재하시 재령과 습도의 영향을 고려한 콘크리트의 합리적인 인장크리프 모델)

  • 이형준;오병환
    • Journal of the Korea Concrete Institute
    • /
    • v.11 no.4
    • /
    • pp.3-11
    • /
    • 1999
  • The creep characteristics of concrete under tensile stress has been usually assumed to have the same characteristics as that under compressive stress in the time-dependent analysis of concrete structures. However, it appears from the recent experimental studies that tensile creep behavior is much different from compressive one. In particular, high sustaining tensile stress may cause time-dependent cracking and thus lead to tensile failure. It is, therefore, necessary to model the tensile creep behavior accurately for realistic time-dependent analysis of concrete structures. The present paper to have been focused to suggested more realistic model for the tensile creep behavior of concrete. The models are compared with tensile creep test data available in the literature. The proposed model may allow more refined analysis of concrete structures under time-dependent loading.

Identifying the Significance of Factors Affecting Creep of Concrete: A Probabilistic Analysis of RILEM Database

  • Adam, Ihab;Taha, Mahmoud M. Reda
    • International Journal of Concrete Structures and Materials
    • /
    • v.5 no.2
    • /
    • pp.97-111
    • /
    • 2011
  • Modeling creep of concrete has been one of the most challenging problems in concrete. Over the years, research has proven the significance of creep and its ability to influence structural behavior through loss of prestress, violation of serviceability limit states or stress redistribution. Because of this, interest in modeling and simulation of creep has grown significantly. A research program was planned to investigate the significance of different factors affecting creep of concrete. This research investigation is divided into two folds: first, an in-depth study of the RILEM creep database and development of a homogenous database that can be used for blind computational analysis. Second: developing a probabilistic Bayesian screening method that enables identifying the significance of the different factors affecting creep of concrete. The probabilistic analysis revealed a group of interacting parameters that seem to significantly influence creep of concrete.

Assessment of Material Properties Using Finite Element Analysis for Small Punch Creep Testing (SP 크리프 시험의 유한요소해석을 이용한 재료물성 평가)

  • Park, Tae-Kyu;Ma, Young-Wha;Yoon, Kee-Bong;Jeong, Ill-Seok
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.511-516
    • /
    • 2001
  • Recently small punch creep testing (or miniature disc bend creep test) has received much attention through European collaborative research projects. This method was considered as a substitute for the conventional creep rupture testing by which the residual creep life is measured from the specimen taken out from serviced components of high temperature plants. It would be beneficial if the material creep properties such as power law creep constants as well as the creep rupture life can be measured from the small punch creep test. In this paper a method of assessing creep constants from the small punch creep testing is proposed. Finite element analyses were performed to investigate evolution of stress and strain rate at the weakest locations of the small punch creep specimen. Elastic-plastic-secondary creep analyses were carried out. The estimation equations for creep constants by the small punch creep testing are proposed based on the finite analysis results. Small punch creep tests were also performed with 9Cr steel and the accuracy of the proposed equation was verified by the experimental results.

  • PDF

Finite Element Analysis of Creep Crack Growth Behavior Including Primary Creep Rate (1차 크리프 속도를 고려한 크리프 균열 진전의 유한요소 해석)

  • Choi, Hyeon-Chang
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.23 no.7
    • /
    • pp.1120-1128
    • /
    • 1999
  • An elastic-viscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. In Cr-Mo steel stress fields obtained from the crack growth method by mesh translation were compared with both cases that the secondary creep rate is only used as creep material property and the primary creep rate is included. Analytical stress fields, Riedel-Rice(RR) field, Hart-Hui-Riedel(HR) field and Prime(named in here) field, and the results obtained by numerical method were evaluated in details. Time vs. stress at crack tip was showed and crack tip stress fields were plotted. These results were compared with analytical stress fields. There is no difference of stress distribution at remote region between the case of 1st creep rate+2nd creep rate and the case of 2nd creep rate only. In case of slow velocity of crack growth, the effect of 1st creep rate is larger than the one of fast crack growth rate. Stress fields at crack tip region we, in order, Prime field, HR field and RR field from crack tip.

Finite Element Analysis of Creep Crack Growth Behavior (크리프 균열 진전 거동의 유한 요소 해석)

  • 최현창
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.22 no.4
    • /
    • pp.490-497
    • /
    • 1998
  • An elast-biscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. The results of mesh translation method are compared with those of node release method. Load line displancement curve obtained from the crack growth analysis by mesh translation shows the improved results than that obtained from the crack growth by node release method when the secondary creep rate is only used as creep material property. The results of accounting for primary creep rate and instantaneous plasticity shows a good agreement with the experimental result.

  • PDF

Reference Stress Based Stress Analysis for Local Creep Rupture of a T-pipe (참조응력법에 입각한 T-배관 국부 크리프 파단 평가를 위한 응력해석 사례연구)

  • Shin Kyu-In;Yoon Kee-Bong;Kim Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.30 no.8
    • /
    • pp.873-879
    • /
    • 2006
  • To investigate applicability of the reference stress approach as simplified inelastic stress analysis to estimate local creep rupture, detailed finite element stress analyses of a T-piece pipe with different inner pressure and system loading levels are performed. The reference stresses are obtained from the finite element (FE) limit analysis based on elastic-perfectly-plastic materials, from which the local reference stress for creep rupture is determined from R5. The resulting inelastic stresses are compared with elastic stresses resulting from linear elastic FE calculations. Furthermore they are also compared with the stresses from full elastic-creep FE analyses. It shows that the stresses estimated from the reference stress approach compare well with those from full elastic-creep FE analysis, which are significantly lower than the elastic stress results. Considering time and efforts for full inelastic creep analysis of structures, the reference stress approach is shown to be a powerful tool for creep rupture estimates and also to reduce conservatism of elastic stress analysis significantly.