Effect of Previous Stress-Strain History on the Dynamic Hysteresis Loop for Rubber in Compression

Nature ◽  
1954 ◽  
Vol 173 (4397) ◽  
pp. 262-263
Author(s):  
D. M. DAVIES ◽  
H. McCALLION
Keyword(s):  
Hysteresis Loop ◽  
Strain History ◽  
Stress Strain ◽  
Dynamic Hysteresis

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

A New Look at Measurements of Network Density

1986 ◽  
Vol 59 (1) ◽  
pp. 138-141 ◽  
Author(s):  
Robert A. Hayes
Keyword(s):  
Hysteresis Loop ◽  
Interaction Parameters ◽  
Network Density ◽  
Stress Strain ◽  
Solvent Interaction ◽  
Solvent Method ◽  
Strain Data ◽  
Good Agreement ◽  
Polymer Solvent ◽  
New Look

Abstract A two-solvent method for determining the polymer-solvent interaction parameters independently of stress-strain data is described. The values obtained are much lower than those reported previously. Network densities calculated from swelling data and these interaction parameters are in good agreement with those calculated from the return portion of a hysteresis loop at high elongations.

scholarly journals A Simplified Method for Elastic-Plastic-Creep Structural Analysis

1985 ◽  
Vol 107 (1) ◽  
pp. 231-237 ◽  
Author(s):  
A. Kaufman
Keyword(s):  
Finite Element ◽  
Stress Relaxation ◽  
Kinematic Hardening ◽  
Nonlinear Finite Element ◽  
Strain History ◽  
Stress Strain ◽  
Element Analysis ◽  
Inelastic Analysis ◽  
Simplified Method ◽  
Time Required

A simplified inelastic analysis computer program (ANSYMP) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects can be calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials, and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

Strain Based Failure Assessment for Offshore Structures Under Seismic Loading

2008 ◽  
Author(s):  
Wangwen Zhao ◽  
Richard Turner ◽  
Jian Liang
Keyword(s):  
Hot Spots ◽  
Low Cycle Fatigue ◽  
Inelastic Strain ◽  
Seismic Loading ◽  
Offshore Structures ◽  
Fortran Program ◽  
Strain History ◽  
Stress Strain ◽  
Failure Assessment ◽  
Stress Reversals

Under seismic loading, structural hot spots can experience very high levels of stress and many random stress reversals. Conventional stress based methods cannot assess the failure state in detail when stress is beyond the elastic limit and nominal stress reversals are more than double the yield stress. A method has been created to fully reproduce the true stress/ strain history by using 1) generalised Masing’s rule with equivalent cyclic energy dissipation to model cyclic stress/strain relation, 2) Neuber’s method to calculate inelastic strain concentration factor, and 3) relative effective notch factor determined from comparing S-N curves of different joint classes. From this reproduced strain history, strain cycles can be counted and low cycle fatigue analysis can be conducted by using Miner’s rule and by estimating damage from the strain based failure criteria such as Coffin-Mason method. This method has been implemented in a numeric procedure and coded in a FORTRAN program called CYSTRA (as for CYclic STRain Analysis). It takes input of “nominal” random stress history directly from general structural software, linear or non-linear, local or global, and calculates extreme strain and strain cycles at multiple hot spots for the whole structure efficiently. Thus it greatly facilitates failure assessment for offshore structures which can have a large number of hot spots within the structure, unlike mechanical devices commonly assessed in strain based analysis where detailed FE based methods can be used.

A Mathematical Model Depicting the Stress-Strain Diagram and the Hysteresis Loop

1959 ◽  
Vol 26 (1) ◽  
pp. 95-100
Author(s):  
I. R. Whiteman
Keyword(s):  
Mathematical Model ◽  
Hysteresis Loop ◽  
Yield Stress ◽  
Frequency Distribution ◽  
Elastic Region ◽  
Tangent Modulus ◽  
Strain Diagram ◽  
Cumulative Frequency ◽  
Cumulative Frequency Distribution ◽  
Stress Strain

Abstract A model is made up of elastoplastic elements, all of which have the same value of Young’s modulus E, but which have different values of yield stress. It is shown that the dimensionless tangent modulus graph Et/E represents the cumulative frequency distribution of those elements which are in the elastic region. From the frequency distribution, the equations for the stress-strain diagram and the hysteresis loop can be written.

Thermo-Mechanical Fatigue of the Nickel Base Superalloy IN738LC for Gas Turbine Blades

2006 ◽  
Vol 321-323 ◽  
pp. 509-512 ◽  
Author(s):  
Jung Seob Hyun ◽  
Gee Wook Song ◽  
Young Shin Lee
Keyword(s):  
Gas Turbine ◽  
Turbine Blades ◽  
Material Behavior ◽  
Experimental Program ◽  
Nickel Base Superalloy ◽  
Strain History ◽  
Stress Strain ◽  
Mechanical Fatigue ◽  
Nickel Base ◽  
Base Superalloy

A more accurate life prediction for gas turbine blade takes into account the material behavior under the complex thermo-mechanical fatigue (TMF) cycles normally encountered in turbine operation. An experimental program has been carried out to address the thermo-mechanical fatigue life of the IN738LC nickel-base superalloy. High temperature out-of-phase and in-phase TMF experiments in strain control were performed on superalloy materials. Temperature interval of 450-850 was applied to thermo-mechanical fatigue tests. The stress-strain response and the life cycle of the material were measured during the test. The mechanisms of TMF damage is discussed based on the microstructural evolution during TMF. The plastic strain energy based life pediction models were applied to the stress-strain history effect on the thermo-mechanical fatigue lives.

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