Extrapolation of Imaginal Minimum Creep Rate in Compression by a Concept of SATO-Index

2017 ◽  
Vol 741 ◽  
pp. 99-104
Author(s):  
Hiroyuki Sato
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Strain Rate ◽  
Creep Curve ◽  
Minimum Creep Rate ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Strain Rate Change ◽  
Primary Stage ◽  
Strain Dependence

Creep characteristics of alloys and compounds have been evaluated mainly by the minimum creep rate or the steady-state creep rate, and by its stress and temperature dependences. In some cases, however, direct comparison of the minimum creep rate or the steady-state creep rate are not practically easy due to difficulties of experiment, i.e., a long duration of primary stage of creep deformation. The minimum creep rates are not always precise representative value, which is directly evaluated from experiments. It should be valuable, if one could estimate the minimum creep rate from creep curve in primary stage. I have proposed a method of quantitative evaluation of creep curve based on the evaluation of strain rate change and its strain dependence during creep [1-3]. The value that reflects a shape of creep curve is named “Strain Acceleration and Transition Objective-Index (SATO-Index)” [4]. SATO-Index and related differential equation show a strain dependence of strain rate and lead entre creep curve by numerical integration. This concept provides quantitative information of shape of each creep curve, and information of the entire creep curve. In this paper, examples of evaluation and extrapolation of creep rate from primary stage in compression are presented. It is concluded that the extrapolation with the concept of SATO-Index reasonably provides imaginal minimum creep rate. Usability of extrapolation of creep curve by the concept is presented.

scholarly journals Creep Investigation on Shale-Like Material with Preexisting Fissure under Coupling Temperatures and Confining Pressures

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Yongyan Wang ◽  
Hongwei Wang ◽  
Xiao Shi
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Strain Rate ◽  
Confining Pressure ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Creep Experiment ◽  
Uniaxial Creep ◽  
Confining Pressures ◽  
Triaxial Creep

In order to investigate the influence of temperature, confining pressure, and preexisting fissure on creep characteristics of rock mass, multistage creep experiments were performed on shale-like material, with preexisting fissure under different temperatures and confining pressures. The results showed that new microcracks generated and propagated with the increase of temperature in both uniaxial and triaxial creep experiments, and the generation and propagation were most pronounced at 60°C and least at 20∼50°C in uniaxial creep experiments. The generation and propagation were restricted by confining pressure. Temperature had less influence on the creep strain rate in triaxial creep experiment, whereas it had a significant influence on the steady-state creep rate in uniaxial creep experiment. The influence of confining pressure on the steady-state creep rate was slight when confining pressure was 1 MPa, whereas it was obvious when confining pressure was 3∼7 MPa. The closure of preexisting fissure promoted the creep strain rate, and the closure was incomplete when confining pressure was below 3 MPa, whereas it was complete when confining pressure at 5 and 7 MPa.

Extrapolation of Creep Curve and Creep Rate by Strain Acceleration Parameter in Al-Mg Solid Solution Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 307-312
Author(s):  
Hiroyuki Sato ◽  
Kosuke Omote ◽  
Akira Sato
Keyword(s):  
Solid Solution ◽  
Steady State ◽  
Creep Rate ◽  
Creep Curve ◽  
Creep Behavior ◽  
Minimum Creep Rate ◽  
Strain Rate Change ◽  
Acceleration Parameter ◽  
Creep Characteristics ◽  
Creep Curves

It has been widely accepted that the creep characteristics at high temperatures are mainly evaluated by a minimum creep rate. Although, a shape of creep curve may vary depending on deformation conditions, the apparent steady state or minimum creep rates be the same. Thus,for detailed analysis and prediction of creep behavior, other values which reflect the shape of each creep curve should be considered. For the purpose, authors have proposed Sato’s strain- acceleration-parameter (Strain Acceleration and Transition Objective index, SATO-index) which reflects strain rate change during creep deformation. Based on the concept of SATO-index, the whole creep curve can be represented by a set of small number of numerical parameters, and can be extrapolated from a part of creep curve. In this paper, application of the concept of SATO-index to the creep curves of aluminum-magnesium solid solutions that the creep behavior of the alloys are well investigated and analyzed. The creep curve can be extrapolated by the concept from transient part of creep curve, and the extrapolated creep rates at the minimum creep rate agree well with experiment. Efficiency of the concept of SATO-index to creep experiments is pronounced.

On Statistical Properties of High Temperature Creep Rupture Data in STS304 Stainless Steels

2006 ◽  
Vol 326-328 ◽  
pp. 553-556
Author(s):  
Seon Jin Kim ◽  
Yu Sik Kong ◽  
Young Jin Roh ◽  
Won Taek Jung
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Stainless Steels ◽  
Probability Distributions ◽  
Creep Rupture ◽  
Steady State Creep ◽  
Rupture Time ◽  
Steady State Creep Rate ◽  
Rupture Data ◽  
Short Time

This paper deals with the statistical properties of short time creep rupture characteristic values (for example, creep rupture time, steady state creep rate, total creep rate, initial strain, etc.) in STS304 stainless steels. From short time creep rupture tests performed by constant stresses at three different elevated temperatures 600, 650 and 700, the scatter and probability distributions were investigated for rupture time, total creep rate, steady state creep rate, initial strain, and others. The effect of temperature on the statistical scatter of rupture time was the smallest at 700. The effect of stress on the statistical scatter of rupture time was smaller with increasing stresses. The probability distributions of short time creep rupture data were well followed 2-parameter Weibull.

On Creep Rupture Characteristics in STS304 Stainless Steels

2006 ◽  
Vol 326-328 ◽  
pp. 1309-1312
Author(s):  
Seon Jin Kim ◽  
Yu Sik Kong ◽  
Young Join Noh ◽  
Won Taek Jung ◽  
Sang Woo Kwon
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Stress Exponent ◽  
Stainless Steels ◽  
Elevated Temperatures ◽  
Creep Rupture ◽  
Steady State Creep ◽  
Rupture Time ◽  
Steady State Creep Rate ◽  
Creep Stress

In this study, the creep rupture tests of STS304 stainless steels were investigated at three different elevated temperatures of 600, 650 and 700 under the constant creep stresses. Creep rupture characteristics such as creep stress, creep rupture time, steady state creep rate and so on were evaluated. The behaviors of creep rate curve and initial strain are compared at three different elevated temperatures. The stress exponent (n) at 600, 650 and 700 based on steady state creep rate showed 22.5, 20.6 and 11.4 respectively. By increasing the temperature, the stress exponent is decreased. At the temperature of 700, the lowest stress exponents are shown and this behavior is also observed in the case of stress exponent based on rupture time. The creep life prediction by LMP method is presented and the equation of this result is as follows: T(logtr+20)=-0.005152-14.56+24126.

A Parametric Approach to Cyclic Creep

1976 ◽  
Vol 43 (1) ◽  
pp. 28-32
Author(s):  
V. M. Radhakrishnan
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Maximum Stress ◽  
Pure Aluminum ◽  
Cyclic Creep ◽  
Steady State Creep ◽  
Strain Accumulation ◽  
Parametric Approach ◽  
Steady State Creep Rate ◽  
Reference Stress

Investigations have been carried out to study the effect of oscillating stress on the strain accumulation in pure aluminum at elevated temperature. The creep rate under the oscillating stress has been found to increase with increasing value of the alternating component of the stress and is somewhat higher than the steady-state creep rate corresponding to the maximum stress, in the range of temperature used. The rupture time is inversely proportional to the cyclic creep rate. A model for obtaining the reference stress has been proposed and based on the data obtained, a parametric approach is presented.

scholarly journals A statistical model to predict the steady-state creep rate

2014 ◽  
Vol 63 (2) ◽  
pp. 028101
Author(s):  
Li Jing-Tian ◽  
Wang Jian-Lu ◽  
Zhang Bang-Qiang ◽  
Rong Xi-Ming ◽  
Ning Xi-Jing
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Statistical Model ◽  
Steady State Creep ◽  
Steady State Creep Rate
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