The Effect of Multiaxiality and Follow-Up on Creep Damage

1990 ◽  
Vol 112 (4) ◽  
pp. 378-385 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Relaxation Process ◽  
Approximate Method ◽  
Creep Damage ◽  
Local Stress ◽  
Relaxation Response ◽  
Relaxation Model ◽  
Stress Strain ◽  
Theoretical Formulation

A simple approximate method for estimating creep damage in pressure components experiencing multiaxial relaxation and follow-up is presented. The theoretical formulation essentially relates the relaxation process that accounts for multiaxiality and follow-up to the uniaxial relaxation model. The effect of follow-up is determined by studying the relaxation response on the Generalized Local Stress Strain (GLOSS) diagram. A procedure for partitioning creep damage into load and deformation-controlled fractions is also discussed. GLOSS analysis is applied to several component configurations that exhibit follow-up potential.

Multiaxial Relaxation and Creep Damage Assessments—A Comparison of ASME N-47 and GLOSS Time-Scaling Methods

1993 ◽  
Vol 115 (1) ◽  
pp. 32-37 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Relaxation Process ◽  
Theoretical Basis ◽  
Creep Damage ◽  
Scaling Method ◽  
G Factor ◽  
Time Scaling ◽  
Scaling Methods ◽  
Asme Code

Two simplified methods for determining multiaxial relaxation and creep damage, the GLOSS time-scaling and the ASME Code Case N-47 method, are described in this paper. The theoretical basis and applicability of the methods to various pressure component configurations are discussed in detail. The G-factor in the ASME formula in effect speeds up or slows down the uniaxial relaxation process, similar to the GLOSS time-scaling method. The two methods are compared, and the differences are attributed to local follow-up not being accounted for in the ASME formula.

The Generalized Local Stress Strain (GLOSS) Analysis—Theory and Applications

1991 ◽  
Vol 113 (2) ◽  
pp. 219-227 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Stress Relaxation ◽  
Low Cycle Fatigue ◽  
Creep Damage ◽  
Local Stress ◽  
Inelastic Strain ◽  
Uniaxial Stress ◽  
Linear Elastic ◽  
Analysis Theory ◽  
Stress Classification

GLOSS analysis is a simple and systematic method for carrying out inelastic evaluations of mechanical components and structures on the basis of two linear elastic finite element analyses. The underlying theory relates redistribution of inelastic stresses at a given location under consideration to the uniaxial stress relaxation process. GLOSS analysis is emerging as a useful technique for determining multiaxial stress relaxation, follow-up, creep damage, inelastic strain concentrations and low-cycle fatigue estimates, limit analysis and issues pertaining to stress-classification.

Effects of local stress, strain, and hydrogen content on hydrogen-related fracture behavior in low-carbon martensitic steel

2021 ◽  
pp. 116828
Author(s):  
Akinobu Shibata ◽  
Takashi Yonemura ◽  
Yuji Momotani ◽  
Myeong-heom Park ◽  
Shusaku Takagi ◽  
...  
Keyword(s):  
Hydrogen Content ◽  
Fracture Behavior ◽  
Martensitic Steel ◽  
Local Stress ◽  
Low Carbon ◽  
Stress Strain ◽  
Carbon Martensitic Steel

scholarly journals Thermodynamic Analysis of Relaxation Model for Non-Equilibrium Phase Behavior of Hydrocarbon Mixtures

2021 ◽  
Vol 2090 (1) ◽  
pp. 012138
Author(s):  
I M Indrupskiy ◽  
P A Chageeva
Keyword(s):  
Relaxation Time ◽  
Phase Behavior ◽  
Relaxation Process ◽  
Thermodynamic Analysis ◽  
Balance Equation ◽  
Equilibrium Phase ◽  
Characteristic Relaxation Time ◽  
Relaxation Model ◽  
Entropy Balance ◽  
Non Equilibrium

Abstract Mathematical models of phase behavior are widely used to describe multiphase oil and gas-condensate systems during hydrocarbon recovery from natural petroleum reservoirs. Previously a non-equilibrium phase behavior model was proposed as an extension over generally adopted equilibrium models. It is based on relaxation of component chemical potentials difference between phases and provides accurate calculations in some typical situations when non-instantaneous changing of phase fractions and compositions in response to variations of pressure or total composition is to be considered. In this paper we present a thermodynamic analysis of the relaxation model. General equations of non-equilibrium thermodynamics for multiphase flows in porous media are considered, and reduced entropy balance equation for the relaxation process is obtained. Isotropic relaxation process is simulated for a real multicomponent hydrocarbon system with different values of characteristic relaxation time using the non-equilibrium model implemented in the PVT Designer module of the RFD tNavigator simulation software. The results are processed with a special algorithm implemented in Matlab to calculate graphs of the total entropy time derivative and its constituents in the entropy balance equation. It is shown that the constituents have different signs, and the greatest influence on the entropy is associated with the interphase flow of the major component of the mixture and the change of the total system volume in the isotropic process. The characteristic relaxation time affects the rate at which the entropy is approaching its maximum value.

Modelling Recovery and Recrystallisation Kinetics after Intercritical Deformation in 0.19 wt% C 1.5 wt% Mn Steel

2004 ◽  
Vol 467-470 ◽  
pp. 329-334 ◽  
Author(s):  
A. Smith ◽  
A. Miroux ◽  
Haiwen Luo ◽  
Jilt Sietsma ◽  
Sybrand van der Zwaag
Keyword(s):  
Stress Relaxation ◽  
Stress Distribution ◽  
Strain Distribution ◽  
Local Stress ◽  
Stress Strain ◽  
Simple Modification ◽  
Single Grain ◽  
Grain Model ◽  
Mn Steel ◽  
Kinetics Of

The softening kinetics of a 0.19 wt% C 1.5 wt% Mn steel deformed at two intercritical temperatures have been characterised using the stress relaxation technique. Recrystallisation of intercritical austenite has been modelled using a single grain model (Chen et al., 2002 [1]), whilst recovery of both intercritical austenite and ferrite has been modelled using a model in the literature [Verdier et al., 1999 [2]). The models are combined to predict the overall softening kinetics with a rule of mixtures formulation. Comparison of the model with experiment shows significant deviations. The reasons are discussed with reference to the mixture rule and to the local stress-strain distribution which exists in the deformed samples. A simple modification to the model is proposed which takes into account the effect of a local stress distribution in deformed austenite.

Comparison of R5 and ASME NH Creep-Fatigue Damage Assessment Methodologies

2013 ◽  
Author(s):  
Michael Sheridan ◽  
David Knowles ◽  
Oliver Montgomery
Keyword(s):  
Fatigue Damage ◽  
Structural Integrity ◽  
Temperature Response ◽  
Creep Damage ◽  
Basic Principles ◽  
Metallic Structures ◽  
Reference Stress ◽  
Creep Fatigue ◽  
Design Generation

The R5 volume 2/3 procedures [1] were developed by British Energy (now EDF Energy) to assess the high temperature response of uncracked metallic structures under steady state or cyclic loading. They contain the basic principles of: • Application of reference stress methods • Consideration of elastic follow up • A ductility exhaustion approach to calculate creep damage accumulation. These considerations represent a fundamental distinction from ASME BPVC Section III, Subsection NH [2]. This paper draws on literature review and experience to explain the principal differences in the limits of application, cycle construction and damage calculation between these codes/procedures focusing on creep-fatigue damage determination. The implications of the differences between the codes and standards are explored. The output of this work is aimed at two groups of structural integrity engineers; those using these codes and standards to assess existing conventional and nuclear plant, and also those looking to ASME and R5 to design Generation IV PWRs with design temperatures much elevated from those of Generation III and III+. The conclusions from this paper offer some practical guidance to structural integrity engineers which may assist in selecting the more appropriate procedure to assess creep-fatigue damage for a particular situation.

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