Shape of creep curves in frozen soils and polycrystalline ice

1987 ◽  
Vol 24 (4) ◽  
pp. 623-629 ◽  
Author(s):  
Anatoly M. Fish
Keyword(s):  
Constitutive Equation ◽  
Creep Strain ◽  
Failure Time ◽  
Frozen Soil ◽  
Time To Failure ◽  
Secondary Creep ◽  
Creep Failure ◽  
Creep Tests ◽  
Creep Curves ◽  
Polycrystalline Ice

A new method was developed for determining creep parameters, particularly the time to failure, from a single linear plot in which an individual creep curve forms a straight line for primary and tertiary creep. Secondary creep is considered to be a principal point on this line that predetermines the onset of failure. The times to failure can be predicted even when creep tests are not complete by extrapolating information obtained for primary creep. Based upon T. H. Jacka's test data, prediction of creep strain was evaluated using the constitutive equation of A. M. Fish for entire creep and compared with the modified Sinha equation of M. F. Ashby and P. Duval for attenuating creep as well as with models for primary and secondary creep. It is shown that the shape of the creep curves, and thus the creep parameters, varies with stress, temperature, and other factors. Hence, a family of creep curves cannot be described by a constitutive equation with a single set of creep parameters that do not take into account these variations without loss in the accuracy of the creep strain calculations. Key words: frozen soil, polycrystalline, ice, creep, failure, time to failure, attenuation, constitutive modelling.

scholarly journals Creep Strain and Permeability Evolution in Cracked Granite Subjected to Triaxial Stress and Reactive Flow

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Fan Zhang ◽  
Jianjian Zhao ◽  
Dawei Hu ◽  
Qian Sheng ◽  
Jianfu Shao
Keyword(s):  
Acid Solution ◽  
Strain Rate ◽  
Creep Strain ◽  
Alkaline Solution ◽  
Confining Pressure ◽  
Creep Strain Rate ◽  
Reactive Flow ◽  
Secondary Creep ◽  
Creep Tests ◽  
Creep Stage

Fluid flow and fluid-rock interaction mainly take place in fracture network, consequently resulting in deformation and permeability variation of rock and deterioration of the wellbore performance. Mechanical-reactive flow coupling creep tests are performed on cracked granite under various confining pressures and acid and alkaline solution flows. The testing results show that the confining pressure and solution pH significantly influence the creep deformation, creep strain rate, and permeability. A primary creep stage and secondary creep stage are observed in all creep tests in this study; notably, the sample under a confining pressure of 10 MPa and acid solution injection undergoes creep failure for over 2700 hours. The acid solution has a more obvious influence on the creep behavior than that of the alkaline solution. With an increase in confining pressure, the total creep strain and creep strain rate in the samples gradually decrease during the injection of either solution. The permeability of the samples injected with either solution gradually deceases during the testing process, and this deceasing rate increases with the confining pressure. The scanning electron microscopy observations on the crack surfaces after the creep tests show that the surfaces of the fractures injected with the acid solution are smooth due to the dissolution of the matrix, while those injected with the alkaline solution include voids due to the dissolution of quartz. These experimental results could improve the understanding of the long-term transport and mechanical behaviors of wellbore.

Simulation of Creep Deformation and Rupture of Notched Bar Specimens of Grade 92 Steel

2015 ◽  
Author(s):  
Haruhisa Shigeyama ◽  
Yukio Takahashi ◽  
Jonathan Parker
Keyword(s):  
Creep Strain ◽  
Creep Behavior ◽  
Power Plants ◽  
Thermal Power ◽  
Failure Criteria ◽  
Creep Rupture ◽  
Creep Failure ◽  
Creep Tests ◽  
Round Bar ◽  
Grade 92 Steel

Creep strain equations of Grade 92 steel which is used in boilers and piping systems of ultra-supercritical (USC) thermal power plants were developed based on the results of creep tests on smooth round bar specimens of three kinds of Grade 92 steels. In these equations, primary creep behavior was represented by a power-law and tertiary creep behavior was described by an exponential function. Creep parameters were determined as a function of creep rupture times which were calculated from stress and absolute temperature. Additionally, generalized creep failure criteria considering the multiaxial stress were established on the basis of results of creep tests on circumferentially notched round bar specimens. These creep strain equations and creep failure criteria were incorporated into finite element analysis software. Then, creep failure analyses were carried out and the resulting deformation behavior and rupture times were compared with the experimental results. Creep rupture lives were predicted with a good accuracy, within a factor of two in most cases.

scholarly journals Brittle Creep Failure, Critical Behavior, and Time-to-Failure Prediction of Concrete under Uniaxial Compression

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Yingchong Wang ◽  
Na Zhou ◽  
Fuqing Chang ◽  
Shengwang Hao
Keyword(s):  
Creep Rate ◽  
Uniaxial Compression ◽  
Power Law ◽  
Critical Behavior ◽  
Creep Process ◽  
Time To Failure ◽  
Secondary Creep ◽  
Creep Failure ◽  
Brittle Creep ◽  
Secondary Creep Rate

Understanding the time-dependent brittle deformation behavior of concrete as a main building material is fundamental for the lifetime prediction and engineering design. Herein, we present the experimental measures of brittle creep failure, critical behavior, and the dependence of time-to-failure, on the secondary creep rate of concrete under sustained uniaxial compression. A complete evolution process of creep failure is achieved. Three typical creep stages are observed, including the primary (decelerating), secondary (steady state creep regime), and tertiary creep (accelerating creep) stages. The time-to-failure shows sample-specificity although all samples exhibit a similar creep process. All specimens exhibit a critical power-law behavior with an exponent of −0.51 ± 0.06, approximately equal to the theoretical value of −1/2. All samples have a long-term secondary stage characterized by a constant strain rate that dominates the lifetime of a sample. The average creep rate expressed by the total creep strain over the lifetime (tf-t0) for each specimen shows a power-law dependence on the secondary creep rate with an exponent of −1. This could provide a clue to the prediction of the time-to-failure of concrete, based on the monitoring of the creep behavior at the steady stage.

Creep rates of spray ice

1990 ◽  
Vol 27 (2) ◽  
pp. 185-194 ◽  
Author(s):  
D. Shields ◽  
L. Domaschuk ◽  
E. Funegard
Keyword(s):  
Power Law ◽  
Constant Pressure ◽  
Creep Behaviour ◽  
Primary Creep ◽  
Control Device ◽  
Petroleum Exploration ◽  
Secondary Creep ◽  
Creep Tests ◽  
Pressure Tests ◽  
Polycrystalline Ice

Mars Island, a man-made spray ice island, was constructed in January and February 1986, and was used as a drill platform for petroleum exploration in the Alaskan Beaufort Sea. A series of pressuremeter creep tests was run in the spray ice of Mars Island in March 1986. Individual constant-pressure tests lasted up to 5 days.It is possible to compare the creep behaviour of the spray ice as interpreted from the pressuremeter tests with the creep behaviour interpreted from the island settlement records. These comparisons are made for both primary and secondary creep on the basis of conventional power law theory. The following points are of particular interest: (1) The primary creep data can be characterized using a simple power law. The exponent of time for spray ice is similar to that for solid polycrystalline ice. The exponent of stress is different for the two kinds of ice. (2) Pressuremeter tests gave secondary creep information that correlates well with the steady-rate settlement of the island. (3) Research into the possible range of primary creep parameters for spray ice is required, given that primary creep accounted for a large portion of the settlement of Mars Island. In particular, the effect of ice density on creep rates mast be resolved. (4) The pressuremeter is potentially an excellent design control device during the manufacture of future spray ice islands. The results of constant-pressure tests of 1–2 days duration could be used to check the design assumptions pertaining to the expected consolidation of the ice mass with time. Key words: spray ice, creep, artificial islands, pressuremeter, settlement.

Creep Behavior for Alloy 617 in Air at 950°C

2010 ◽  
Vol 654-656 ◽  
pp. 508-511 ◽  
Author(s):  
Woo Gon Kim ◽  
Song Nan Yin ◽  
Gyeong Geon Lee ◽  
Yong Wan Kim
Keyword(s):  
Creep Behavior ◽  
Primary Creep ◽  
Secondary Creep ◽  
Creep Tests ◽  
Alloy 617 ◽  
Very High Temperature Reactor ◽  
Creep Curves ◽  
High Temperature Reactor ◽  
Very High ◽  
Cr2o3 Layer

Creep behavior for Alloy 617, which is considered as one of the major structural materials of a very high temperature reactor, was investigated in air at 950oC. Creep experimental data was obtained by a series of creep tests with different stress levels at 950oC. Alloy 617 revealed little primary creep strains and unclear secondary creep stages. A tertiary creep stage was initiated from a low strain level and was dominant in full creep curves. The creep constants of A, n, m, and C in Norton’s power law and Monkman-Grant relationships were determined. In microstructure observations of crept specimens, it was found that a Cr2O3 oxidation layer was formed on the surface, and just beneath the Cr2O3 layer, an internal Al-oxide sub layer was formed with rod shapes. Also, below the internal sub layer, a thick carbide-depleted zone was developed due to reaction of the chromia and carbide precipitates. The thickness of the outer Cr-oxide layer increased with increasing creep rupture times. The increasing tendency showed a smooth slope like a parabolic curve.

scholarly journals Experimental Study on the Short-Term Uniaxial Creep Characteristics of Sandstone-Coal Composite Samples

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1398
Author(s):  
Dawei Yin ◽  
Feng Wang ◽  
Jicheng Zhang ◽  
Faxin Li ◽  
Chun Zhu ◽  
...  
Keyword(s):  
Creep Strain ◽  
Stress Level ◽  
Creep Strength ◽  
Creep Deformation ◽  
Shear Failure ◽  
Composite Sample ◽  
Short Term ◽  
Creep Failure ◽  
Creep Tests ◽  
Composite Samples

In this investigation, the uniaxial short-term creep tests with multi-step loading were conducted on the sandstone-coal composite samples, and the characteristics of creep strength, creep deformation, acoustic emission (AE), and creep failure of composite samples were studied, respectively. The creep strength of the composite sample decreased with the stress-level duration, which was mainly determined by the coal and influenced by the interactions with the sandstone. The creep deformation and damage of sandstone weakened the deformation and damage accumulation within the coal, resulting in the larger strength for the composite sample compared with the pure coal sample. The axial creep strain of composite sample generally increased with the stress-level or the stress-level duration under same conditions. The AE characteristics of composite sample were related to the creep strain rate, the stress level, the stress level duration, and the local failure or fracture during creep loading. The micro or macro failure and fracture within the composite sample caused the rise in the axial creep strains and the frequency and intensity of AE signals, especially the macro failure and fracture. The creep failures of composite samples mainly occurred within the coal with the splitting ejection failure accompanied by the local shear failure, and no obvious failures were found within the sandstone. The coal in the composite sample became more broken with the stress-level duration.

Effect of the type of creep constitutive equation on strain and stress distributions of notched cylindrical bars under tension creep

1998 ◽  
Vol 33 (5) ◽  
pp. 347-356 ◽  
Author(s):  
T Majima ◽  
Q Liu ◽  
K Haruki
Keyword(s):  
Constitutive Equation ◽  
Creep Strain ◽  
Tertiary Creep ◽  
Secondary Creep ◽  
Stress Distributions ◽  
Notch Radius ◽  
Two Factors ◽  
Strain Components ◽  
The Difference ◽  
High Degree

A finite element calculation was performed to investigate the effect of differences in the type of creep constitutive equation on the distributions of strain and stress on the net section of notched cylindrical bars subjected to large deformation. Three different types of creep constitutive equation were employed; they are of primary-tertiary creep, primary-secondary creep and tertiary creep. The effect of type of creep constitutive equation on the creep strain components versus deformation at the net section 2 In(d0/d) relations and on the distribution of axial creep strain decreases with decreasing notch radius. For a small notch radius the values of creep strain components on the net section are determined to a high degree of accuracy only by two factors of notch radius and 2 In(d0/d). The deep concave distribution of axial creep strain and high strain concentration are maintained during creep deformation. The axial and equivalent stresses versus 2 In(d0/d) relations are strongly affected by the difference in type of creep constitutive equation.

scholarly journals Micromechanical Modeling of Creep Behavior in Particle-Reinforced Silicone-Rubber Composites

1997 ◽  
Vol 64 (4) ◽  
pp. 781-786 ◽  
Author(s):  
Chao-Hsun Chen ◽  
Chaing-Ho Cheng
Keyword(s):  
Creep Strain ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Micromechanical Modeling ◽  
Elastic Behavior ◽  
Rubber Matrix ◽  
Secondary Creep ◽  
Rubber Composites ◽  
Creep Tests ◽  
Two Phase

A micromechanically based composite model is proposed to study the viscoelastic behavior of solid-filled rubber composites. A nonlinear So-Chen’s (1991) mechanical model which describes the viscoelastic behavior of the rubber matrix is proposed to relate volume-average deformation and stress within the two-phase composite inclusion to the remote (macroscopic) fields. The influence of the volume fractions of inclusions on the overall creep strain of a rubber-matrix composite is investigated at the level of dilute concentration. The creep rate of the rubber matrix, which depends nonlinearly on the creep strain and the primary creep and secondary creep resulting from the viscous flow of creep deformation, is also considered in addition to the usual steady-state, or secondary, creep. The method developed for the calculation of the incremental process is based upon Eshelby’s (1957) equivalence principle of an inhomogeneity-transformation problem and Mori-Tanaka’s (1973) idea of mean-field stress. In order to examine the applicability of the model as well as the nonlinear stretch parameter, a series of experiments on solid-filled silicone rubbers has been carried out, which included constant rate of tensile tests and creep tests. It is demonstrated that this simple, albeit approximate micromechanical modeling is capable of predicting the volume fraction dependence of the time dependent creep, with characteristic consistency with the known elastic behavior.

Creep Failure Behavior of Notched Structure in the Simulated Steam Turbine Rotor: Experimental and Damage Analysis

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Tian-Ye Niu ◽  
Cheng Gong ◽  
Jian-Guo Gong ◽  
Fu-Zhen Xuan
Keyword(s):  
Constitutive Equation ◽  
Steam Turbine ◽  
Contact Region ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Failure Behavior ◽  
Creep Failure ◽  
Creep Tests ◽  
Blade Root ◽  
Evolution Behavior

Abstract Notched structures widely exist in steam turbine components in fossil power plant, e.g., the groove of the rotor, etc. Previous studies indicate that creep failures occur at the groove of the rotor or the adjacent regions. Thus, it is essential to study the creep failure behavior of the notched structures for the safe operation of the system. In this work, creep tests of the simulated steam turbine component have been conducted at the temperature of 605 °C, and the creep-damage constitutive equation is used to track the evolution behavior of creep strain and damage of this component. The influence of structural and loading configurations on creep failure behavior of the component is discussed. Results demonstrate that the shearing failure at the contact area between the blade root and the rotor is observed for the tested component, while the cracking at the groove of the rotor is not found. Creep-damage constitutive equation employed in this work could provide an adequate solution of the simulated component. Parametric studies indicate that creep crack initiation and creep failure of the simulated components may occur at the contact region (i.e., between the blade root and the rotor) and the groove of the rotor, which is closely related to structural and loading configurations of the components.

Predicting the Time to Failure in Heavily Loaded Masonry Specimens with the Acoustic Emission Technique

2010 ◽  
Vol 133-134 ◽  
pp. 217-222 ◽  
Author(s):  
Els Verstrynge ◽  
Luc Schueremans ◽  
Dionys Van Gemert
Keyword(s):  
Acoustic Emission ◽  
Failure Time ◽  
Event Rate ◽  
Creep Damage ◽  
Time To Failure ◽  
Creep Tests ◽  
Strain Monitoring ◽  
Specimen Processing ◽  
Term Creep

This paper presents the results of a research project in which the knowledge on testing of creep damage in masonry and acoustic emission (AE) monitoring are combined. Results from different types of creep tests are combined to investigate whether AE monitoring could predict the failure time of the masonry specimens. In previous work, it was observed that the AE event rate is related to the time to failure of the specimen. Processing of the results of new tests enables to update the previously found relation between AE event rate and failure time and to indicate a confidence interval for predictions made with this model. Additionally, the question can be raised whether temporary monitoring could detect unstable damage accumulation and predict failure. Therefore, the results of long-term creep tests are analysed and compared with data from strain monitoring. The results indicate that in most cases, the failure can be predicted.

Sign in / Sign up

Export Citation Format

Share Document