Creep and Plastic Strains Under Stress Reversal in Torsion With and Without Simultaneous Tension for 304 Stainless Steel at 593°C

1983 ◽  
Vol 50 (3) ◽  
pp. 587-592 ◽  
Author(s):  
U. W. Cho ◽  
W. N. Findley
Keyword(s):  
Viscoelastic Model ◽  
Single Step ◽  
304 Stainless Steel ◽  
Creep Recovery ◽  
Plastic Strains ◽  
Test Results ◽  
Aging Effects ◽  
Stress Changes ◽  
Constant Tension ◽  
Stress Reversals

Results of creep experiments under stress reversals in torsion with and without constant tension are reported. Constitutive equations based on data for single step creep and creep recovery tests previously reported are used to describe the test results. A viscous-viscoelastic model with aging effects and modifications for step-down stress changes and stress reversals predicted the creep behavior reasonably well. The prediction of time-independent plastic strains is also described.

Creep and Plastic Strains Under Side Steps of Tension and Torsion for 304 Stainless Steel at 593°C

1983 ◽  
Vol 50 (3) ◽  
pp. 580-586 ◽  
Author(s):  
U. W. Cho ◽  
W. N. Findley
Keyword(s):  
Viscoelastic Model ◽  
Single Step ◽  
304 Stainless Steel ◽  
Plastic Strains ◽  
Test Results ◽  
Aging Effects ◽  
Creep And Recovery ◽  
Stress Changes ◽  
Abrupt Changes ◽  
Step Down

Results of nonproportional stress changes on creep and plastic strains resulting from abrupt changes in proportion of tension and torsion are reported. Both step-up and step-down changes are included. Constitutive equations based on data for single step creep and recovery tests previously reported are used to describe the test results. A viscous-viscoelastic model with aging effects and modifications for step-down tests predicted the creep behavior reasonably well. The prediction of time-independent plastic strains is also described.

Creep and Plastic Strains of 304 Stainless Steel at 593°C Under Step Stress Changes, Considering Aging

1982 ◽  
Vol 49 (2) ◽  
pp. 297-304 ◽  
Author(s):  
U. W. Cho ◽  
W. N. Findley
Keyword(s):  
Stainless Steel ◽  
Constitutive Equations ◽  
Time Dependent ◽  
304 Stainless Steel ◽  
Flow Rule ◽  
Strain Component ◽  
Plastic Strains ◽  
Aging Effects ◽  
Stress Changes ◽  
Step Down

Nonlinear constitutive equations for varying stress histories are developed and used to predict the creep behavior of 304 stainless steel at 593°C (1100°F) under variable tension or torsion stresses including reloading, complete unloading, step-up, and step-down stress changes. The strain in the constitutive equations (a viscous-viscoelastic model) consists of: linear elastic, time-independent plastic, time-dependent-recoverable viscoelastic, and time-dependent-nonrecoverable viscous components. For variable stressing, the modified superposition principle, derived from the multiple integral representation, and the strain hardening theory were used to represent the recoverable and nonrecoverable components, respectively, of the time-dependent strain. Time-independent plastic strains were described by a flow rule of similar form to that for nonrecoverable, time-dependent strains. The material constants of the theory were determined from constant stress creep and creep recovery data. Considerable aging effects were found and the effects on the strain components were incorporated in each strain predicted by the theory. Some modifications of the theory for the viscoelastic strain component under step-down stress changes were made to improve the predictions. The final predictions combining the foregoing features made satisfactory agreements with the experimental creep data under step stress changes.

A Constitutive Model of Creep Describing Creep Recovery and Material Softening Caused by Stress Reversals

1985 ◽  
Vol 107 (1) ◽  
pp. 1-6 ◽  
Author(s):  
N. Ohno ◽  
S. Murakami ◽  
T. Ueno
Keyword(s):  
Constitutive Model ◽  
Creep Strain ◽  
304 Stainless Steel ◽  
Creep Recovery ◽  
Creep Tests ◽  
Constant Tension ◽  
Stress Reversals ◽  
Strain Space ◽  
Type 304 ◽  
Type 304 Stainless Steel

The constitutive model of creep proposed by the present authors on the basis of a creep-hardening surface in creep strain space (CHS model) is first modified to incorporate creep recovery. It is assumed that total creep strain can be divided into two parts; i.e., a part which recovers anelastically after stress removal and an irrecoverable part. These two parts are described by McVetty’s equation and the CHS model, respectively. Then, the validities of the modified and the original CHS model are discussed by performing creep tests of type 304 stainless steel under cyclic reversed torsion combined with constant tension at 600°C.

Creep and Creep Recovery of 304 Stainless Steel Under Combined Stress With a Representation by a Viscous-Viscoelastic Model

1980 ◽  
Vol 47 (4) ◽  
pp. 755-761 ◽  
Author(s):  
U. W. Cho ◽  
W. N. Findley
Keyword(s):  
Stainless Steel ◽  
Viscoelastic Model ◽  
Multiple Integral ◽  
Time Dependent ◽  
304 Stainless Steel ◽  
Creep Recovery ◽  
Strain Component ◽  
Stress Dependence ◽  
Nonlinear Stress ◽  
Stress States

Creep and creep-recovery data of 304 stainless steel are reported for experiments under constant combined tension and torsion at 593°C (1100°F). The data were represented by a viscous-viscoelastic model in which the strain was resolved into five components—elastic, plastic (time-independent), viscoelastic (time-dependent recoverable), and viscous (time-dependent nonrecoverable) which has separate positive and negative components. The data are well represented by a power function of time for each time-dependent strain. By applying superposition to the creep-recovery data, the recoverable creep strain was separated from the nonrecoverable. The form of stress-dependence associated with a third-order multiple integral representation was employed for each strain component. The time-dependent recoverable and nonrecoverable strains had different nonlinear stress dependence; but, the time-independent plastic strain and time-dependent nonrecoverable strain had similar stress-dependence. A limiting stress below which creep was very small or negligible was found for both recoverable and nonrecoverable components as well as a yield limit. The limit for recoverable creep was substantially less than the limits for nonrecoverable creep and yielding. The results showed that the model and equations used in the analysis described quite well the creep and creep-recovery under the stress states tested.

Creep and Creep Recovery of 304 Stainless Steel at Low Stresses With Effects of Aging on Creep and Plastic Strains

1981 ◽  
Vol 48 (4) ◽  
pp. 785-790 ◽  
Author(s):  
U. W. Cho ◽  
W. N. Findley
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Viscoelastic Model ◽  
Time Dependent ◽  
304 Stainless Steel ◽  
Dislocation Creep ◽  
Creep Recovery ◽  
Power Functions ◽  
Transition Stress ◽  
Stress Levels

Creep and creep recovery data of 304 stainless steel are reported for experiments at low stress levels under combined tension and torsion at 593°C (1100°F). The data were represented by a viscous-viscoelastic model in which the strain was resolved into five components—elastic, plastic (time-independent), viscoelastic (time-dependent recoverable), and viscous (time-dependent nonrecoverable) which has separate positive and negative components. Only part of the creep strain at low stresses was recovered upon complete unloading following creep (as also found at high stresses), and each time-dependent strain data was well represented by a power function of time. But the stress dependence below a transition stress was approximately a linear relation with no creep limits and no cross effects such as were found in a previous analysis for higher stress levels above a transition stress. The transition stress for nonrecoverable strains agrees with the Frost-Ashby boundary between diffusional flow and dislocation creep. Aging decreased the creep rate and plastic strain. Results for different times of aging at 593°C (1100°F) under pure tension stresses were well represented by power functions of aging time up to 1000 h for each creep component and plastic strain.

48 Hour Multiaxial Creep and Creep Recovery of 2618 Aluminum Alloy at 200°C

1984 ◽  
Vol 51 (1) ◽  
pp. 125-132 ◽  
Author(s):  
J.-L. Ding ◽  
W. N. Findley
Keyword(s):  
Homogeneous Function ◽  
Maximum Shear Stress ◽  
Full Range ◽  
Viscoelastic Model ◽  
Multiple Integral ◽  
Constant Stress ◽  
Time Dependent ◽  
Creep Recovery ◽  
Aging Effects ◽  
Data Set

Data are reported from 48 hour constant multiaxial stress creep followed by 48 hour creep recovery with the magnitudes of the effective stress ranging from 34.5 MPa (5.00 ksi) to 175.5 MPa (25.46 ksi). They differed from a previous data set in the much longer constant-stress durations and the inclusion of data from low stress creep, compression creep, and short term aging tests. Data were represented by a viscous-viscoelastic model in which the time-dependent strain was resolved into recoverable and nonrecoverable components. Previous stress-strain relations for constant stress creep and recovery were modified to include the current experimental observations of the nonexistence of creep limits, negligible aging effects, and symmetry in tension and compression. The time dependence was represented by a power of time with different exponents for the recoverable and nonrecoverable components. A homogeneous function of maximum shear stress was developed to represent the full range of stress dependence of the nonrecoverable time-dependent components; the third-order multiple integral representation was used for the recoverable component.

scholarly journals Effects of extended short-term aging duration on asphalt binder behaviour at high temperatures

2016 ◽  
Vol 11 (4) ◽  
pp. 302-312 ◽  
Author(s):  
Meor Othman Hamzah ◽  
Seyed Reza Omranian
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
High Temperatures ◽  
Test Temperature ◽  
Asphalt Binder ◽  
Pavement Performance ◽  
Test Results ◽  
Aging Effects ◽  
Short Term ◽  
Surface Method

Many factors affecting pavement performance include variations in binder composition and environmental conditions during asphalt mixture production. Hence, predicting pavement performance is a difficult task. This paper aims to investigate the effects of short term aging on binder viscosity at high temperature. In order to predict the effects of short term aging on the asphalt binder viscosity at high temperatures, a Response Surface Method was performed on the Rotational Viscometer test results. An experimental matrix was planned based on the central composite design for aging duration and test temperature. The test results showed that aging increased the binder viscosity, while increasing test temperature decreased the corresponding value. However, aging effects differ and depend on binder types, test temperatures and aging conditions. It was also found that the Response Surface Method is a fast, effective and reliable method to predict the effects of aging on binder viscosity behaviour at high temperatures.

Viscoelastic–Viscoplastic Cyclic Deformation of Polycarbonate Polymer: Experiment and Constitutive Model

2016 ◽  
Vol 83 (4) ◽  
Author(s):  
Chao Yu ◽  
Guozheng Kang ◽  
Fucong Lu ◽  
Yilin Zhu ◽  
Kaijuan Chen
Keyword(s):  
Constitutive Model ◽  
Kinematic Hardening ◽  
Viscoelastic Model ◽  
Creep Recovery ◽  
Strong Nonlinearity ◽  
Viscoplastic Strain ◽  
Cyclic Tension ◽  
Nonlinear Viscoelastic ◽  
Tension Tests ◽  
Proposed Model

A series of uniaxial tests (including multilevel loading–unloading recovery, creep-recovery, and cyclic tension–compression/tension ones) were performed to investigate the monotonic and cyclic viscoelastic–viscoplastic deformations of polycarbonate (PC) polymer at room temperature. The results show that the PC exhibits strong nonlinearity and rate-dependence, and obvious ratchetting occurs during the stress-controlled cyclic tension–compression/tension tests with nonzero mean stress, which comes from both the viscoelasticity and viscoplasticity of the PC. Based on the experimental observation, a nonlinear viscoelastic–viscoplastic cyclic constitutive model is then constructed. The viscoelastic part of the proposed model is constructed by extending the Schapery's nonlinear viscoelastic model, and the viscoplastic one is established by adopting the Ohno–Abdel-Karim's nonlinear kinematic hardening rule to describe the accumulation of irrecoverable viscoplastic strain produced during cyclic loading. Furthermore, the dependence of elastic compliance of the PC on the accumulated viscoplastic strain is considered. Finally, the capability of the proposed model is verified by comparing the predicted results with the corresponding experimental ones of the PC. It is shown that the proposed model provides reasonable predictions to the various deformation characteristics of the PC presented in the multilevel loading–unloading recovery, creep-recovery, and cyclic tension–compression/tension tests.

scholarly journals Development of novel apparatus to obtain soil resistance–displacement relationship for well conductor fatigue analysis

2017 ◽  
Vol 54 (10) ◽  
pp. 1435-1446 ◽  
Author(s):  
Arash Zakeri ◽  
Hendrik Sturm ◽  
Rune Dyvik ◽  
Philippe Jeanjean
Keyword(s):  
Cyclic Loading ◽  
Interaction Mechanism ◽  
Physical Modelling ◽  
Fatigue Analysis ◽  
Test Results ◽  
Major Step ◽  
Soil Response ◽  
Geotechnical Centrifuge ◽  
Field Samples ◽  
Stress Changes

An important aspect of deepwater well integrity is development of accurate conductor fatigue analysis due to cyclic loading during drilling operations. Fatigue damage in a structure occurs from stress changes in response to cyclic loading. In practice, the lateral cyclic soil response is typically modelled using Winkler lateral load–displacement (p–y) springs. However, recently developed soil models for conductor fatigue analysis are based on physical modelling in a geotechnical centrifuge. Notwithstanding the advantages of centrifuge modelling for investigating the conductor–soil interaction mechanism, development of simple laboratory tools to obtain p–y data directly from intact soil samples obtained from the field can also be very beneficial. This paper describes the development of a novel apparatus to obtain p–y and soil damping relationships from field samples specifically tailored for well conductor fatigue analysis. In addition, it compares test results obtained using reconstituted kaolin clay and intact natural Onsøy clay with centrifuge test results; ultimately demonstrating a satisfactory agreement between the two techniques. The results are highly encouraging and are believed to present a major step forward in deepwater well conductor fatigue analysis. The findings may also be beneficial to the offshore renewable energy sector.

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