Improvement of J Estimation Schemes Based on Reference Stress for Linear Hardening Behavior

2018 ◽  
Author(s):  
Philippe Gilles
Keyword(s):  
Plasticity Theory ◽  
Practical Case ◽  
Linear Hardening ◽  
Hardening Behavior ◽  
Hardening Law ◽  
Reference Stress ◽  
Deformation Plasticity ◽  
3D Applications ◽  
Reference Stress Approach ◽  
J Estimation

In Elastic-Plastic Fracture Mechanics, several J-estimation schemes are based on the reference stress approach. This approach has been developed initially for creep analyses and later on for elasto-plastic fracture assessments in 1984, then included in the R6 rule. Much later, other methods, based on the reference stress concept, were derived for 3D applications like the Js method introduced in the French RSE-M code in 1997 and the Enhanced Reference Stress (ERS) method in Korea around 2001. However, these developments are based on the J2 deformation plasticity theory and well established for a pure power hardening law. Js and ERS schemes propose some corrections for recorded behavior laws which cannot be fitted by a power law. Nevertheless, their application to materials governed by a bilinear hardening law has been called into question by several studies. One of these, carried out by M. T. Kirk and R. H. Dodds [1, 2] is of great interest since addressing the practical case of a surface cracked plate.

Effect of the Type of Stress-Strain Law on the Validity of the Reference Stress Approach in Fracture Mechanics

2014 ◽  
Author(s):  
Philippe Gilles ◽  
Gongchen Zhang ◽  
Komlanvi Madou
Keyword(s):  
Fracture Mechanics ◽  
Power Law ◽  
Plasticity Theory ◽  
Material Behavior ◽  
Stress Strain ◽  
Hardening Law ◽  
Reference Stress ◽  
Deformation Plasticity ◽  
Reference Stress Approach ◽  
J Estimation

In fracture mechanics, several J-estimation schemes are based on the reference stress approach. This approach has been developed initially in the frame of the R5 rule for creep and R6 rule for elasto-plastic fracture assessments. Later other methods, based on the reference stress concept, where derived like the Js method introduced in the French RSE-M code en 1997 and the Enhanced Reference Stress (ERS) method in Korea around 2001. However these developments are based on the J2 deformation plasticity theory and well established for a pure power hardening law. Even in this latter case, the reference stress depends on the hardening exponent. Js and ERS attempt to minimize this dependence and propose some corrections for recorded behavior laws which cannot be fitted by a power law. However their validation has been established mainly on cases where the material behavior is governed by a Ramberg-Osgood (R0) law. The question may be raised, as for the bilinear hardening law case, of the existence of a reference stress for non RO laws.

Engineering J Estimation Equations for Spent Fuel Canisters Under Combined Mechanical and Welding Residual Stresses

2018 ◽  
Author(s):  
Hyun-Jae Lee ◽  
Jae-Yoon Jeong ◽  
Yun-Jae Kim ◽  
Poh-Sang Lam
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Fe Analysis ◽  
Welding Residual Stress ◽  
Spent Fuel ◽  
Basic Form ◽  
Estimation Equations ◽  
Reference Stress ◽  
J Estimation

This paper provides engineering J estimation equations for Spent Fuel Canisters (SFCs) under combined mechanical and welding residual stress (WRS) fields. The basic form of estimation equations is reference stress-based ones as in R6. Interaction between mechanical (primary) and residual (secondary) stresses is treated using the V-factor. Based on systematic finite element (FE) analysis and J results, the V-factors for the combined mechanical and welding residual stresses are reported.

A Reference Stress Approach to Creep Bending of Straight Tubes

1974 ◽  
Vol 16 (3) ◽  
pp. 125-138 ◽  
Author(s):  
J. Fairbairn
Keyword(s):  
Entire Range ◽  
Creep Behaviour ◽  
Tensile Creep ◽  
Bending Moments ◽  
Stress Distributions ◽  
Creep Tests ◽  
Reference Stress ◽  
Hyperbolic Sine ◽  
Rotation Method ◽  
Reference Stress Approach

Reference-stress parameters, based on the Norton constitutive equation, are developed for creep bending of circular and elliptical tubes. The parameters are presented in the form of a design chart. The reference stress methods apply also to other simple constitutive equations of the power law, exponential and hyperbolic sine forms, and also to two complex equations describing creep behaviour over the entire range from primary to tertiary. In these equations the functions of stress and time are not separable and reference stress techniques provide a convenient method of evaluating stationary stress distributions and investigating the variation of these stresses with time. Aluminium alloy tubes were creep tested with cyclic uniform bending moments. Creep strains to fracture were measured by an end-rotation method. The creep behaviour of the tubes was well predicted by reference-stress cyclic tensile creep tests.

Material Data for Modelling Density Distributions in Green Parts

2011 ◽  
Vol 672 ◽  
pp. 207-214
Author(s):  
C. Shang ◽  
I. Csaba Sinka ◽  
J. Pan
Keyword(s):  
Constitutive Models ◽  
Powder Materials ◽  
Density Distributions ◽  
State Variable ◽  
Hardening Law ◽  
Deformation Plasticity ◽  
Powder Pressing ◽  
Die Compaction ◽  
Complex Parts ◽  
Cam Clay

Die compaction of powders is a process which involves filling a die with powder, compaction using rigid punches to form a dense compact and ejection from the die. The process can be treated as a large deformation plasticity problem. The challenge is to develop and implement appropriate constitutive models that capture the evolution of the powder from a loose state into a dense compact. In this paper we describe data analysis procedures and calibrate classic incremental plasticity models, such as Cam-Clay, Drucker-Prager cap models. The complexity of the models is increased from models with a hardening law to more complex constitutive models using density as state variable. The compaction behaviour of a range of powder materials is characterized experimentally. Numerical simulation of the compaction of simple parts and complex parts is demonstrated. The merits of various models are evaluated in terms of the balance between complexity and practicality. The discussion is illustrated with case studies exploring the applicability of the models specific to various powder pressing scenarios.

scholarly journals Mathematical modeling of materially nonlinear problems in structural analyses, Part I: Theoretical fundamentals

2010 ◽  
Vol 8 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Zoran Bonic ◽  
Verka Prolovic ◽  
Biljana Mladenovic
Keyword(s):  
Nonlinear Problems ◽  
Failure Surface ◽  
Plasticity Theory ◽  
Rigid Plastic ◽  
Material Models ◽  
Linear Elastic ◽  
Hardening Law ◽  
Plastic Yield ◽  
Normality Condition ◽  
Von Mises

Material models describe the way they behave when loaded. The paper presents the development of the model beginning with the simplest linear-elastic and rigid-plastic ones. The basic data in the plasticity theory have been defined, such as criterion and yield (failure) surface, hardening law, plastic yield law and normality condition. Yield criteria of Tresca, Von Mises, Mohr-Coulomb and Drucker-Prager were given separately.

Sign in / Sign up

Export Citation Format

Share Document