Development of an Automated Fatigue Crack Propagation Test System

2008 ◽  
pp. 44-44-23 ◽  
Author(s):  
RS Vecchio ◽  
DA Jablonski ◽  
BH Lee ◽  
RW Hertzberg ◽  
CN Newton ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Test System ◽  
Fatigue Crack Propagation Test

scholarly journals Uncertainty Modeling of Fatigue Crack Growth and Probabilistic Life Prediction for Welded Joints of Nuclear Stainless Steel

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3192 ◽  
Author(s):  
Haijun Chang ◽  
Mengling Shen ◽  
Xiaohua Yang ◽  
Junxia Hou
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Life Prediction ◽  
Power Plants ◽  
Test System

Welded joints are widely used in the pipeline connection of nuclear power plants. Defects in these joints are an important factor leading to the failure of welded joints. It is critical to study the fatigue crack growth and life prediction methods for the welded joints with defects, to reduce their likelihood. In this paper, we present our study of the uncertainty of fatigue crack propagation and probabilistic life prediction for welded joints of nuclear stainless steel. The standard compact tension (CT) specimens were fabricated according to the American Society for Testing and Materials (ASTM) standard. Fatigue crack propagation tests with different stress ratios were performed on CT specimens, using the Mei Te Si (MTS) fatigue test system. A fatigue crack propagation rate model considering the uncertainty of material parameters, and based on the Paris formula and crack propagation experimental data, was established. A probabilistic life prediction method based on Monte Carlo simulation was developed. The fatigue crack propagation prediction result of a CT specimen was compared with the actual tested result, to verify the effectiveness of the proposed method. Finally, the method was applied to an embedded elliptical crack in welded joints of nuclear stainless steel, to predict the fatigue crack growth life and evaluate the reliability.

scholarly journals The Variation Law of Mechanical Parameters of Type I Fatigue Crack Tip Under High Frequency Resonant Loading

2015 ◽  
Vol 9 (1) ◽  
pp. 379-387
Author(s):  
Gao Hong-Li ◽  
Zheng Huan-Bin ◽  
Qiu Xin-Guo ◽  
Liu Huan ◽  
Liu Hui
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
High Frequency ◽  
Crack Tip ◽  
Type I ◽  
Mechanical Parameters ◽  
Stress Cycle ◽  
Fatigue Crack Propagation Test

This work explores the variation law of mechanical parameters at fatigue crack tip of compact tension specimen with type I pre-notch based on dynamic finite element method (FEM) in the high frequency resonant fatigue crack propagation test. The displacement fields, the strain fields and the stress intensity factors (SIF) at CT specimen fatigue crack tip in one stress cycle and at different crack lengths under constant amplitude high frequency sinusoidal alternating loading condition are calculated and the related variation laws of mechanical parameters are analyzed. In order to calculate the dynamic SIF at fatigue crack tip, the static SIF has been calculated first. The compared results of the static finite element analysis with the theoretical calculation show that finite element modeling and calculating method and respective results are accurate. Secondly, the variation law of SIF at crack tip during the process of fatigue crack propagation test is studied by dynamic FEM. Finally, the high frequency resonant fatigue crack propagation test has been performed and the dynamic strain gauge is used to measure the strain at crack tip during one stress cycle. The research results show that during crack stable propagation stage, the displacement, strain and SIF at type I fatigue crack tip are in the same form having high frequency resonant load, and the displacement, strain and SIF amplitude increase with the crack growth. The error of static SIF between the calculated result by FEM and the theoretical result is 2.51%. The maximum error of the strain at crack tip between the FEM calculating result and the experimental result is 2.93%.

Image Based Displacement Vector Estimation Method around the Fatigue Crack Tip

2010 ◽  
Vol 452-453 ◽  
pp. 341-344
Author(s):  
Masao Moriyama ◽  
Daisuke Ushijima ◽  
Junichi Katsuta
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Strain Field ◽  
High Speed ◽  
Displacement Vector ◽  
Estimation Method ◽  
Crack Tip ◽  
Instantaneous Strain ◽  
Fatigue Crack Propagation Test

To clarify the instantaneous strain field during the fatigue crack propagation test, an attempt is made to estimate the displacement vector of the small area of the crack tip from the high speed movie. The key theory of the estimation is Particle Image Velocimetry (PIV) which is frequently use in the fluid dynamical data analysis. PIV means the area based correlation matching between the sequential image pair. At first the earlier image divided into the small subareas, and on the later image most correspondent position to the subarea is searched. The each displacement of the subarea position between earlier and later image means the local deformation of the crack tip. Through the numerical simulation, the subarea size and search area size are defined to get the realistic result. To make the instantaneous deformation within a cycle of the fatigue crack propagation test, high-speed camera with high-power camera is used. The frame rate is beyond 1000Hz and shutter speed is 1/8000 second. By using the such camera and optimized PIV algorithm, the instantaneous strain field can be estimated and this will analyze the phenomenon of fatigue crack propagation.

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