Creep Prediction From Stress Relaxation Coupled With Equivalent Relaxation Rate

2014 ◽  
Vol 644-650 ◽  
pp. 1382-1385
Author(s):  
Jin Quan Guo ◽  
Wu Zhou Meng ◽  
Fei Li ◽  
Li Xin Wang
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Creep Rate ◽  
Stress Relaxation ◽  
Relaxation Rate ◽  
Steady State Creep ◽  
Creep Tests ◽  
Conversion Model ◽  
Two Stages ◽  
Good Agreement

Several stress relaxation and creep tests of high temperature material are performed. According to the characteristics of stress relaxations and the superposition equation of diffusion and Maxwell equations of two stages, equivalent relaxation time and equivalent relaxation rate are proposed. Considering equivalent relaxation rate as the creep rate under constant stress, the relaxation-creep conversion model is built up and presented. Then the steady-state creep curve and creep rate are calculated. The results show that the numerical results are in good agreement with the experimental data. It indicates that equivalent relaxation rate can be employed for the analysis of steady-state creep rate. The conversion model and method can be used to design the creep strength and predict the life of the component at high temperature.

scholarly journals Deformation of Floating Ice Shelves

1957 ◽  
Vol 3 (21) ◽  
pp. 38-42 ◽  
Author(s):  
J. Weertman
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Creep Deformation ◽  
Plasticity Theory ◽  
Steady State Creep ◽  
Creep Tests ◽  
Ice Shelves ◽  
The Antarctic ◽  
Good Agreement

AbstractThe problem of the creep deformation of floating ice shelves is considered. The problem is solved using Glen’s creep law for ice and Nye’s relation of steady-state creep (the analogue of the Lévy-Miles relation in plasticity theory). Good agreement is obtained between an observed creep rate at Maudheim in the Antarctic and that predicted from the results of creep tests made by Glen.

scholarly journals Deformation of Floating Ice Shelves

1957 ◽  
Vol 3 (21) ◽  
pp. 38-42 ◽  
Author(s):  
J. Weertman
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Creep Deformation ◽  
Plasticity Theory ◽  
Steady State Creep ◽  
Creep Tests ◽  
Ice Shelves ◽  
The Antarctic ◽  
Good Agreement

AbstractThe problem of the creep deformation of floating ice shelves is considered. The problem is solved using Glen’s creep law for ice and Nye’s relation of steady-state creep (the analogue of the Lévy-Miles relation in plasticity theory). Good agreement is obtained between an observed creep rate at Maudheim in the Antarctic and that predicted from the results of creep tests made by Glen.

Reloading Stress Relaxation Behavior Analysis Based on a Creep Model for High Temperature Bolting Steel

2013 ◽  
Vol 328 ◽  
pp. 950-954
Author(s):  
Wei Wei Zhang ◽  
Hong Xu ◽  
Hong Yuan Li
Keyword(s):  
High Temperature ◽  
Stress Relaxation ◽  
Steady State Creep ◽  
Relaxation Behavior ◽  
Creep Model ◽  
National Research Institute ◽  
Time Intervals ◽  
Stress Relaxation Behavior ◽  
Proposed Model ◽  
Good Agreement

An analytical method based on a creep model is being developed to investigate the effect of retightening on stress relaxation behavior for high-temperature turbine and valve studs/bolts. In order to validate the approach, the calculated results are compared to the results of uniaxial reloading stress relaxation testing, which were performed by the National Research Institute for Metals of Japan (NRIM) for 12Cr-1Mo-1W-1/4V stainless steel bolting material at 550°C. It was shown that the proposed model based on Altenbach-Gorash-Naumenko creep model for the primary and steady state creep could be applied for the present data. The calculated residual stresses versus time curves were in good agreement with the measured for initial stress level of 273.6MPa at 550°C and for specific reloading time intervals of 24, 72, 240, and 720 hours.

Design of Pressurized Cylinders for High-Temperature Applications

1960 ◽  
Vol 82 (2) ◽  
pp. 477-481
Author(s):  
J. F. Traexler
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Creep Rate ◽  
Plane Strain ◽  
Material Properties ◽  
Rate Function ◽  
Specific Form ◽  
Steady State Creep ◽  
Numerical Examples ◽  
Walled Cylinder

General equations for the stresses in a thick-walled cylinder in a state of plane strain are derived considering “steady-state” creep. A specific form of the creep-rate function is assumed and numerical examples are included to show the effect of geometry and material properties.

Prediction Methodology of Creep Performance from Stress Relaxation Measurements

2013 ◽  
Vol 401-403 ◽  
pp. 920-923 ◽  
Author(s):  
Jin Quan Guo ◽  
Hui Chao Shi ◽  
Wu Zhou Meng
Keyword(s):  
High Temperature ◽  
Stress Relaxation ◽  
Creep Strain ◽  
Estimation Method ◽  
Creep Tests ◽  
High Temperature Materials ◽  
Relaxation Measurements ◽  
Isothermal Creep ◽  
The Relationship ◽  
Good Agreement

An estimation method to predict creep performances of high temperature structural materials has been proposed. The method is to use a simplified and normalized model of stress relaxation to derive creep strain rates and creep strain vs. time curves from stress relaxation measurements through an integrated analytical procedure according to the relationship between stress relaxation and creep. In order to validate the approach, the predicted results are compared to the experimental results of uni-axial isothermal creep tests conducted on 1Cr10NiMoW2VNbN steel with the same temperature of stress relaxation tests. Good agreement between results of relaxation tests and the predicted results indicates that the developed method can be recommended in the creep behavior evaluation of high temperature materials.

High Temperature Creep Behavior of Zn-1.0Cu-0.2Ti Alloy

2011 ◽  
Vol 287-290 ◽  
pp. 769-776 ◽  
Author(s):  
Lai Rong Xiao ◽  
Xi Min Zhang ◽  
Yan Wang ◽  
Wei Li ◽  
Quan Sheng Sun ◽  
...  
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Creep Rate ◽  
Grain Boundary ◽  
Testing Machine ◽  
Steady State Creep ◽  
Diffusional Creep ◽  
High Temperature Creep ◽  
Steady State Creep Rate ◽  
Temperature Creep

In the present work, Zn-1.0Cu-0.2Ti alloy was prepared by melt casting and extruding processes. High temperature creep property of the alloy was determined using electronic creep relaxation testing machine. Microstructures of the alloy before and after creep test were observed and its high temperature creep mechanism was discussed. The results show that the steady-state creep rate of the alloy increases with temperature and stress. The logarithm of steady-state creep rate (ln) shows a linearity relationship with the logarithm of the stress (lnσ) and reciprocal of temperature (1/T). The stress exponent and apparent activation energy for creep have been determined to be 5.10 and 83.7 kJ/mol, separately. The predominant mechanism is mainly self-diffusional creep. The second phases on the grain boundary can block the slip of grain boundary and dislocation motion which can improve creep resistance of the alloy.

Creep Based Prediction Model of Stress Relaxation Behavior for High Temperature Materials

2010 ◽  
Vol 139-141 ◽  
pp. 356-359 ◽  
Author(s):  
Jin Quan Guo ◽  
Li Xin Wang ◽  
Fu Zhen Xuan
Keyword(s):  
High Temperature ◽  
Creep Rate ◽  
Stress Relaxation ◽  
Creep Damage ◽  
Relaxation Behavior ◽  
Assessment Procedure ◽  
Stress Relaxation Behavior ◽  
High Temperature Materials ◽  
Two Stages ◽  
Rate Conversion

An average creep rate conversion model based on Schlottner-Seeley creep assessment procedure and creep damage equation has been developed by considering the relationship that two stages of stress relaxation are corresponding to the first and the second creep stage respectively and the effect of these two kinds of creep rate on relaxation, and stress relaxation is creep at various stresses. And an incremental calculation prediction methodology of stress relaxation performance was established. The predicted results are compared with the data of stress relaxation tests conducted on bolting steel 1Cr10NiMoW2VNbN used in ultra-supercritical turbines. Validation results indicate that the developed model has led to better consistent results with the measured data and thus can be recommended in stress relaxation behavior prediction of high temperature materials.

Creep Contributes to the Fatigue Behavior of Bovine Trabecular Bone

1998 ◽  
Vol 120 (5) ◽  
pp. 647-654 ◽  
Author(s):  
S. M. Bowman ◽  
X. E. Guo ◽  
D. W. Cheng ◽  
T. M. Keaveny ◽  
L. J. Gibson ◽  
...  
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Trabecular Bone ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Hysteresis Loops ◽  
Steady State Creep ◽  
Time To Failure ◽  
Steady State Creep Rate ◽  
Creep Tests

Repetitive, low-intensity loading from normal daily activities can generate fatigue damage in trabecular bone, a potential cause of spontaneous fractures of the hip and spine. Finite element models of trabecular bone (Guo et al., 1994) suggest that both creep and slow crack growth contribute to fatigue failure. In an effort to characterize these damage mechanisms experimentally, we conducted fatigue and creep tests on 85 waisted specimens of trabecular bone obtained from 76 bovine proximal tibiae. All applied stresses were normalized by the previously measured specimen modulus. Fatigue tests were conducted at room temperature; creep tests were conducted at 4, 15, 25, 37, 45, and 53°C in a custom-designed apparatus. The fatigue behavior was characterized by decreasing modulus and increasing hysteresis prior to failure. The hysteresis loops progressively displaced along the strain axis, indicating that creep was also involved in the fatigue process. The creep behavior was characterized by the three classical stages of decreasing, constant, and increasing creep rates. Strong and highly significant power-law relationships were found between cycles-to-failure, time-to-failure, steady-state creep rate, and the applied loads. Creep analyses of the fatigue hysteresis loops also generated strong and highly significant power law relationships for time-to-failure and steady-state creep rate. Lastly, the products of creep rate and time-to-failure were constant for both the fatigue and creep tests and were equal to the measured failure strains, suggesting that creep plays a fundamental role in the fatigue behavior of trabecular bone. Additional analysis of the fatigue strain data suggests that creep and slow crack growth are not separate processes that dominate at high and low loads, respectively, but are present throughout all stages of fatigue.

A Correlation Law for Steady State Creep and Stress Relaxation Tests on the Al-Al2Cu Composite

1981 ◽  
Vol 12 ◽  
Author(s):  
M. Ignat ◽  
R. Bonnet ◽  
F. Durand
Keyword(s):  
Steady State ◽  
Stress Relaxation ◽  
Threshold Stress ◽  
Preexponential Factor ◽  
Grain Boundary Sliding ◽  
Steady State Creep ◽  
Physical Models ◽  
Creep Tests ◽  
Linear Defects ◽  
Creep And Stress Relaxation

ABSTRACTDeformation by creep or by stress-relaxation involve similar thermally activated phenomena. In particular our microstructural observations on the Al-Al2Cu lamellar composite illustrated the importance of the interphase accommodation mechanisms, specially movements of linear defects at the phase boundaries.Our experimental results have shown that the asymptotic stress measured in stress-relaxation tests takes the same value as the threshold stress limiting the steady state creep domain. From this finding we develop a simple Bingham rheological model in which a temperature dependent threshold stress is combined with a generalized Dorn viscosity law. The model correlates satisfactorily the results of both steady state creep tests and the results of stress-relaxation tests.The calculated activation energy and stress exponent are compared with the values deduced from physical models of deformation accommodation through grain boundary sliding. The preexponential factor of the viscosity law is discussed with reference to its dependence on the dislocation substructure.

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