An Investigation of Transient Creep by Means of Endochronic Viscoplasticity and Experiment

1995 ◽  
Vol 117 (3) ◽  
pp. 260-268 ◽  
Author(s):  
Han C. Wu ◽  
Chin C. Ho
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Creep Strain ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
Constant Stress ◽  
Stress Rate ◽  
304 Stainless Steel ◽  
Unified Approach ◽  
Creep Tests

Creep of metals has been investigated by means of the endochronic constitutive equation. This is a unified approach. Transient creep tests have been conducted on 304 stainless-steel specimens with carefully monitored precreep loading stage, either loaded at a prescribed constant strain-rate or at a constant stress-rate. It has been found that, for the same hold stress, the creep strain is larger for test with a constant stress-rate preloading than that for a constant strain-rate preloading. This is an effect of plasticity-creep interaction. In all cases, the initial creep strain rate is a continuation of the preloading strain rate. The theory satisfactorily describes the experimental results.

An Experimental Study on the Effect of Prior Plastic Straining on Creep Behavior of 304 Stainless Steel

1993 ◽  
Vol 115 (2) ◽  
pp. 200-203 ◽  
Author(s):  
Z. Xia ◽  
F. Ellyin
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Strain Rate ◽  
Creep Behavior ◽  
Test Procedure ◽  
Constant Strain Rate ◽  
304 Stainless Steel ◽  
Creep Model ◽  
Plastic Strain Rate ◽  
Creep Tests

Constant strain-rate plastic straining followed by creep tests were conducted to investigate the effect of prior plastic straining on the subsequent creep behavior of 304 stainless steel at room temperature. The effects of plastic strain and plastic strain-rate were delineated by a specially designed test procedure, and it is found that both factors have a strong influence on the subsequent creep deformation. A creep model combining the two factors is then developed. The predictions of the model are in good agreement with the test results.

Strain Hardening of Annealed 304 Stainless Steel by Creep

1993 ◽  
Vol 115 (4) ◽  
pp. 345-350 ◽  
Author(s):  
Han-Chin Wu ◽  
Chin-Cheng Ho
Keyword(s):  
Stainless Steel ◽  
Strain Hardening ◽  
Kinematic Hardening ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
304 Stainless Steel ◽  
Isotropic Hardening ◽  
Loading Surface ◽  
Before And After ◽  
Strain Hardening Behavior

Combined axial-torsional experiments have been conducted at room temperature on thin-walled tubes to investigate the strain hardening behavior of annealed 304 stainless steel due to creep. The constant strain-rate dynamic loading (or SCISR) surfaces representing the state of material before and after creep have benn determined. It has been found that transient creep essentially causes the loading surface to undergo kinematic hardening with insignificant amount of isotropic hardening for this material. A conclusion is drawn that the loading surface hardened by transient creep is the same as that hardened by plastic deformation. This is true both for specimens with pure tension and pure torsion loading paths. The results confirm assumptions of the overstress theory of viscoplasticity.

Transient creep behaviour of Ni3Al polycrystals

2000 ◽  
Vol 646 ◽  
Author(s):  
Tomas Kruml ◽  
Birgit Lo Piccolo ◽  
Jean-Luc Martin
Keyword(s):  
Strain Rate ◽  
Yield Point ◽  
Work Hardening ◽  
Creep Behaviour ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
Peak Temperature ◽  
Creep Tests ◽  
Repeated Stress ◽  
Deformation Parameters

ABSTRACTRepeated creep tests were used for measuring various constant strain-rate deformation parameters. The results are consistent with those of repeated stress relaxations, although the precision is lower for creep in the present case. The small yield point observed in reloading after the transient is directly related to the amount of exhausted mobile dislocations, i.e. it originates from multiplication processes. During the transient test (180s total), the total exhaustion rate of mobile dislocations can be as high as 99%. It exhibits a maximum at the same T (about 500 K) as the work hardening. This supports the validity of a model which considers the work-hardening peak temperature to correspond to the stress under which incomplete Kear-Wilsdorf locks yield.

A Rate-Dependent Stress-Strain Relationship for Sea Ice

1983 ◽  
Vol 105 (1) ◽  
pp. 2-5 ◽  
Author(s):  
Y. S. Wang
Keyword(s):  
Sea Ice ◽  
Strain Rate ◽  
Nonlinear Models ◽  
Constant Strain Rate ◽  
Relative Difference ◽  
Constant Stress ◽  
Stress Rate ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Relationship

A one-dimensional rate-sensitive stress-strain relationship is developed to describe the uniaxial mechanical behavior in compression for sea ice. It is a one-term, nonlinear model and is simpler in form than the nonlinear models proposed by other investigators. It contains four independent constants that are determined by experimental data. This model can describe the behavior of sea ice very well under constant strain rate loading, constant stress rate loading and creep loading conditions. In particular, it describes the following features of sea behavior: 1 the increase in ice strength with strain rate and with stress rate; 2 the increase in strain-softening effects with strain rate; 3 the relative difference between the strengths obtained by constant stress rate and constant strain rate tests; 4 the rate dependence of ice stiffness; 5 primary, secondary, and tertiary creep, where the duration and rate depend on the applied stress level. This paper presents the proposed rate-sensitive stress-strain relationship and discusses its behavior under various loading conditions. A set of coefficients has been selected to compare with test results under constant strain rates. Agreement between predicted and observed stress-strain behaviors is very good. Predicted behavior under constant stress rate and creep are also presented.

Reliability Prediction of 304 Stainless Steel Using Sine-Hyperbolic Creep-Damage Model With Monte Carlo Simulation Method

2019 ◽  
Author(s):  
Md Abir Hossain ◽  
Calvin Maurice Stewart
Keyword(s):  
Stainless Steel ◽  
Monte Carlo ◽  
Strain Rate ◽  
Creep Strain ◽  
Creep Deformation ◽  
Stress Rupture ◽  
Material Constant ◽  
Creep Strain Rate ◽  
304 Stainless Steel ◽  
Material Constants

Abstract Typically continuum damage mechanics (CDM) based constitutive models are applied deterministically where the uncertainty of experiments is not considered. This is also true for the Sine-hyperbolic (Sinh) CDM-based constitutive model where the model is calibrated to represent 50% reliability of creep data. There is a need to implement Sinh in a more stochastic manner. The objectives of this study is to incorporate the probabilistic feature in the Sinh creep damage model to reliably predict the minimum-creep-strain-rate, creep-rupture and creep deformation. This will be achieved using Monte-Carlo methods. Creep deformation data for 304 Stainless Steel is collected from literature consisting of tests conducted at 300 and 320 MPa at 600°C with five replicates. The replicate tests exhibited substantial scatter in the minimum-creep-strain-rate, stress-rupture, and overall creep deformation. Subsequently, upon calibration using the Sinh model, the material constants among the replicates varied. The trends of uncertainty carried by each material constant are studied. The interdependence of the material constants is evaluated to determine if the uncertainty carried by each material constant can be regressed using a co-dependence function. The Monte Carlo method was applied to determine the extent that the creep deformation curve varies taking into consideration the variability of the material constants. Monte Carlo simulations show that the predicted creep deformation persists within the bounds of the experimental data. A large number of Monte Carlo simulations using the Sinh model enabled the creation of credible reliability bands for the minimum-creep-strain-rate, stress-rupture, and creep deformation of 304 Stainless Steel. In future work, this statistical method will be applied to the variability of service conditions, pre-existing defects, and material constants to quantitatively establish the reliability of the Sinh model in simulating component-level creep deformation to rupture.

Evaluation of Creep Constitutive Equations for Type 304 Stainless Steel Under Repeated Multiaxial Loading

1982 ◽  
Vol 104 (3) ◽  
pp. 159-164 ◽  
Author(s):  
Y. Ohashi ◽  
N. Ohno ◽  
M. Kawai
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Strain Hardening ◽  
Deviatoric Stress ◽  
304 Stainless Steel ◽  
Multiaxial Loading ◽  
Mixed Hardening ◽  
Principal Axes ◽  
Type 304 ◽  
Type 304 Stainless Steel

Four kinds of creep constitutive models, i.e., strain-hardening, modified strain-hardening, kinematic-hardening, and mixed-hardening theory, are evaluated on the basis of creep-test results on type 304 stainless steel at 650°C under repeated multiaxial loading. The predictions of the four models are compared with the experimental results. It is shown that substantial differences appear among these predictions under large rotations of the principal axes of the deviatoric stress tensor, and that none of them can describe with sufficient accuracy the transient increase of strain-rate and the noncollinearity between the deviatoric stress and creep strain-rate vectors which are observed just after the stress-rotations.

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