Notch Root Displacement (NRD) Approach to Predict Crack Initiation Life of Notched Specimen in High-Temperature Multiaxial Low Cycle Fatigue

1990 ◽  
Vol 112 (4) ◽  
pp. 429-434 ◽  
Author(s):  
Hiroshi Umeda ◽  
Masao Sakane ◽  
Masateru Ohmani
Keyword(s):  
High Temperature ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Notch Root ◽  
Three Dimensional ◽  
Fem Analysis ◽  
Cycle Fatigue ◽  
Notched Specimen ◽  
Crack Initiation Life ◽  
Three Dimensional Finite Element

This paper describes the notch root displacement (NRD) approach to assess the crack initiation life of notched specimens in high-temperature multiaxial low cycle fatigue. Two and three-dimensional finite element method (FEM) analyses were made to estimate the local displacement at the notch root in tension, torsion, and combined tension/torsion. From the FEM analysis, a simple equation which expresses the intensity of the notch root displacement was derived and it was applied to the experimental data. The equation well correlates the crack initiation life of the notched specimen in high-temperature multiaxial low cycle fatigue.

Life Prediction for Notched Components in Nonproportional Low Cycle Fatigue: Experiment and FEM Analysis

2004 ◽  
Author(s):  
Masao Sakane ◽  
Tsuneo Itoh ◽  
Tomoshige Susaki ◽  
Yoshiyasu Kawazoe
Keyword(s):  
Crack Initiation ◽  
Linear Models ◽  
Low Cycle Fatigue ◽  
Notch Root ◽  
Fem Analysis ◽  
Local Strain ◽  
304 Stainless Steel ◽  
Cycle Fatigue ◽  
Notched Specimens ◽  
Strain Paths

This paper studies the low cycle fatigue of circumferential notched specimens of type 304 stainless steel in nonproportional loading. Strain controlled tension-torsion low cycle fatigue tests were carried out using the notched specimens under 15 strain paths. Crack initiation lives detected by a d.c. potential method were discussed in relation to the strain concentration factors and strain histories. Finite element analyses were carried out for evaluating the local strain at the notch root using elastic-perfectly plastic and bi-linear models. The maximum principal strain and nonproportional strain ranges conservatively estimated the crack initiation lives of the notched specimens.

Prediction of Low-Cycle Fatigue Life of Specimens With Fabrication Flaws

1968 ◽  
Vol 90 (4) ◽  
pp. 620-626 ◽  
Author(s):  
A. G. Pickett
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Small Specimen ◽  
Cycle Fatigue ◽  
Notch Stress ◽  
Weld Defect ◽  
Life Analysis ◽  
Fatigue Life Analysis ◽  
Crack Initiation Life

A modification of the notch stress procedure for fatigue-life analysis is presented. The importance of considering the mechanics of the specimen and the effects of the notch on specimen mechanics is illustrated by example. The procedure is applied to correlate the results of small specimen tests with large weld defect specimen tests. The significance of crack-initiation life and crack-propagation life and the dependence of these portions of total fatigue life on specimen geometry and loading is developed.

CDM Approach Applied to Crack Initiation and Propagation under Variable Amplitude

2016 ◽  
Vol 829 ◽  
pp. 55-60
Author(s):  
Jin Yang Chu ◽  
Jian Xing Mao
Keyword(s):  
Crack Initiation ◽  
Damage Accumulation ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Continuum Damage Mechanics ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Crack Initiation Life ◽  
Initiation Stage

In this paper, the low cycle fatigue crack initiation life was regarded as a process of damage accumulation and a damage accumulation model was established based on the Continuum Damage Mechanics. By the model, we analyzed how the variable amplitude applied at the crack initiation stage influenced the low cycle fatigue life of high temperature materials. With the parameters of GQGH4169 alloy at room temperature, we determined the specific values of damage parameters by finite element method and numerical analysis method. Then, the crack initiation life predictions were carried out. The results show that using this approach can not only predict the crack initiation life of CT specimen accurately, but also reflect a definite influence of variable amplitude on the crack propagation life combining with the Paris Law, and the test costs reduced consequently.

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