A Method for Quantifying Creep Strain Due to Cyclic Stress

1974 ◽  
Vol 41 (4) ◽  
pp. 953-958 ◽  
Author(s):  
J. J. Williams ◽  
F. A. Leckie
Keyword(s):  
Creep Strain ◽  
Creep Test ◽  
Cyclic Creep ◽  
Cyclic Stress ◽  
Constant Stress ◽  
Stress Tests ◽  
Creep Strains

A method is proposed for isolating the two constants required to quantify the creep strains caused by cyclic histories of stress. These constants can be determined from the results of a single cyclic creep test together with data from constant stress tests.

A Method for Estimating Creep Deformation of Structures Subjected to Cyclic Loading

1973 ◽  
Vol 40 (4) ◽  
pp. 928-934 ◽  
Author(s):  
J. J. Williams ◽  
F. A. Leckie
Keyword(s):  
Cyclic Loading ◽  
Creep Strain ◽  
Effective Stress ◽  
Creep Test ◽  
Creep Deformation ◽  
Cyclic Creep ◽  
Uniaxial Stress ◽  
Time Varying ◽  
Proportional Loading

A method is proposed for estimating structural creep deformation due to histories of cyclic proportional loading. The method applies to structures composed of materials whose creep strain due to constant uniaxial stress is given by an equation of the form ε(t)/ε0={σ/σ0}n{t/t0}m Knowledge of the form of the creep law for time-varying stress is not required, as use is made of an effective stress obtained from a single cyclic creep test.

Low-Cycle Fatigue Behaviour of Gas Turbine Alloys

1974 ◽  
Vol 188 (1) ◽  
pp. 321-328 ◽  
Author(s):  
W. J. Evans ◽  
G. P. Tilly
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
High Stress ◽  
Cyclic Creep ◽  
Fatigue Curve ◽  
Fatigue Behaviour ◽  
Material Surface ◽  
Tension Stress ◽  
Cycle Fatigue ◽  
Stress Tests

The low-cycle fatigue characteristics of an 11 per cent chromium steel, two nickel alloys and two titanium alloys have been studied in the range 20° to 500°C. For repeated-tension stress tests on all the materials, there was a sharp break in the stress-endurance curve between 103 and 104 cycles. The high stress failures were attributed to cyclic creep contributing to the development of internal cavities. At lower stresses, failures occurred through the growth of fatigue cracks initiated at the material surface. The whole fatigue curve could be represented by an expression developed from linear damage assumptions. Data for different temperatures and types of stress concentration were correlated by expressing stress as a fraction of the static strength. Repeated-tensile strain cycling data were represented on a stress-endurance diagram and it was shown that they correlated with push-pull stress cycles at high stresses and repeated-tension at low stresses. In general, the compressive phase tended to accentuate cyclic creep so that ductile failures occurred at proportionally lower stresses. Changes in frequency from 1 to 100 cycle/min were shown to have no significant effect on low-cycle fatigue behaviour.

An approach to the determination of cyclic creep strain

1979 ◽  
Vol 11 (11) ◽  
pp. 1225-1229 ◽  
Author(s):  
V. P. Golub
Keyword(s):  
Creep Strain ◽  
Cyclic Creep

On the Interrupted Creep Test Under Low Stress Levels for the Power Law Parameter Extraction

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Bin Yang ◽  
Fu-Zhen Xuan ◽  
Wen-Chun Jiang
Keyword(s):  
Creep Strain ◽  
Stress Level ◽  
Creep Test ◽  
Creep Deformation ◽  
Parameter Extraction ◽  
Tertiary Creep ◽  
Secondary Creep ◽  
Creep Stage ◽  
Strain Data

Abstract Low stress interrupted creep test, as an interim compromise, can provide essential data for creep deformation design. However, there are no clear guidelines on the characterization of the terminating time for interrupted low-stress creep test. To obtain a suitable terminating time in terms of economy and effectiveness, long-term creep strain data of 9%Cr steels are collected from literatures and their creep deformation characterization is analyzed. First, the variations of normalized time and strain of each creep stage with the stress level are discussed. Then, the effect of the terminating time on final fitted results of Norton–Bailey equation is estimated. Third, the relationship between demarcation points at different creep stages and minimum/steady-state creep rate is analyzed. The results indicate that when the creep rupture life is considered as an important factor for creep design, the tertiary creep stage is of greatest significance due to the largest life fraction and creep strain fraction at low stress level. However, the primary and secondary creep stages are of great significance for design due to their larger contribution to 1% limited creep strain. And the long-term secondary creep data could be extrapolated by combining the primary creep strain data obtained from interrupted creep tests with the time to onset of tertiary creep derived from a similar Monkman–Grant relationship.

High-Temperature Creep Tests of Two Creep-Resistant Materials at Constant Stress and Constant Load

2019 ◽  
Vol 827 ◽  
pp. 246-251
Author(s):  
Vàclav Sklenička ◽  
Květa Kuchařová ◽  
Marie Kvapilová ◽  
Luboš Kloc ◽  
Jiří Dvořák ◽  
...  
Keyword(s):  
Creep Behaviour ◽  
Constant Load ◽  
Complex Stress ◽  
Constant Stress ◽  
Fracture Mechanisms ◽  
Stress Tests ◽  
Creep Tests ◽  
Deformation And Fracture ◽  
Dependent Component ◽  
The Difference

Creep is defined as a time dependent component of plastic deformation. Creep tests can be performed either at constant load or at constant applied stress. Engineering creep tests carried out at constant load are aimed at determination of the creep strength or creep fracture strength, i.e. the data needed for design. The constant stress tests are important as a data source for fundamental investigations of creep deformation and fracture mechanisms and for finite element modelling of more complex stress situations. For some materials, the difference between the two type of testing can be very small, while for other materials is large, depending on the creep plasticity of the material under testing. The paper aims to compare the creep results of two different creep-resistant materials: the advanced 9%Cr martensitic steel (ASME Grade P91) and a Zr1%Nb alloy obtained by both testing methods and to clarify the decisive factors causing observed differences in their creep behaviour.

Studies about the Drained Creep Characteristic of Silt Soil on k0 Consolidation

2014 ◽  
Vol 941-944 ◽  
pp. 2631-2635 ◽  
Author(s):  
Yan Fang Wang ◽  
Zhi Gang Zhou ◽  
Zheng Yin Cai
Keyword(s):  
Plastic Strain ◽  
Constitutive Model ◽  
Creep Strain ◽  
Creep Test ◽  
Empirical Formula ◽  
Axial Loading ◽  
Soil Creep ◽  
Time Extension ◽  
Creep Characteristic ◽  
Creep Constitutive Model

The creep characteristic of saturated silt soil was studied by k0 consolidation creep test through two stress paths of axial loading and lateral lightening. According to test datas, some conclusions were submitted. First, the axial creep laws between the two stress paths were consistent on drainage conditions. Volume strains were much smaller than Axial strains. Volume strains presented alternation characteristic between shear shrinkage and shear dilatancy along with time extension. The silt soil creep constitutive model was presented. The results suggested combining the NHRI model describing the transient elastic-plastic strain with the creep empirical formula describing creep strain to establish the creep constitutive model.

Cyclic Plasticity and Cyclic Creep in Austenitic-Ferritic Duplex Steel

2011 ◽  
Vol 465 ◽  
pp. 431-434
Author(s):  
Jaroslav Polák ◽  
Martin Petrenec ◽  
Jiří Man ◽  
Tomáš Kruml
Keyword(s):  
Creep Rate ◽  
Plastic Strain ◽  
Strain Amplitude ◽  
Cyclic Creep ◽  
Cyclic Stress ◽  
Plastic Strain Amplitude ◽  
Cyclic Plasticity ◽  
Stress Strain ◽  
Duplex Steel ◽  
Mean Stresses

Smooth specimens made from austenitic-ferritic duplex steel were subjected to constant stress amplitude loading with positive mean stresses. Hysteresis loops were recorded during the fatigue life and plastic strain amplitude and cyclic creep rate were determined. Fatigue hardening/softening curves, cyclic creep curves and cyclic stress-strain curves for different positive mean stresses were evaluated. Typical dislocation structures developed in both phases of the duplex steel were identified using TEM, compared with the saturated plastic strain amplitude and correlated with the decrease of the cyclic creep rate during cycling and the slope of the cyclic stress-strain curve.

scholarly journals Analysis of Test System Misalignment in the Creep Test

1982 ◽  
Vol 104 (4) ◽  
pp. 280-284
Author(s):  
Han C. Wu ◽  
T. P. Wang
Keyword(s):  
Creep Strain ◽  
Creep Test ◽  
Test System ◽  
Neutral Axis ◽  
Strain Level ◽  
Initial Strain ◽  
Creep Tests ◽  
Test Sheet ◽  
Creep Stress ◽  
Creep Time

An analysis of test system misalignment is presented for the creep test. Sheet type rectangular 1100-0 aluminum specimens are used for discussion. It is found that the creep strain at the geometric centerline of the specimen is different than that at the neutral axis. However, this difference in the creep strain decreases with time. Generally, the effect of misalignment decreases with creep time. Creep tests conducted with long pullrods and large initial strain level (high creep stress) will tend to minimize the effect of misalignment.

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