Effect of Hydrogen Environment of Fatigue Crack Initiation and Fatigue Crack Growth from Small Holes in SUS304 Steel

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.

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A Probabilistic Micromechanical Code for Predicting Fatigue Life Variability: Model Development and Application

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2180811 ◽

2005 ◽

Vol 128 (4) ◽

pp. 889-895 ◽

Cited By ~ 8

Author(s):

K. S. Chan ◽

M. P. Enright

Keyword(s):

Fatigue Crack ◽

Fatigue Life ◽

Fatigue Crack Growth ◽

Crack Initiation ◽

Crack Growth ◽

Model Development ◽

Fatigue Crack Initiation ◽

Crack Size ◽

Crack Initiation Life ◽

Variability Model

This paper summarizes the development of a probabilistic micromechanical code for treating fatigue life variability resulting from material variations. Dubbed MICROFAVA (micromechanical fatigue variability), the code is based on a set of physics-based fatigue models that predict fatigue crack initiation life, fatigue crack growth life, fatigue limit, fatigue crack growth threshold, crack size at initiation, and fracture toughness. Using microstructure information as material input, the code is capable of predicting the average behavior and the confidence limits of the crack initiation and crack growth lives of structural alloys under LCF or HCF loading. This paper presents a summary of the development of the code and highlights applications of the model to predicting the effects of microstructure on the fatigue crack growth response and life variability of the α+β Ti-alloy Ti-6Al-4V.

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Machine Learning Based Prognostics of Fatigue Crack Growth in Notch Pre-cracked Aluminum 7075-T6 Rivet Hole

Annual Conference of the PHM Society ◽

10.36001/phmconf.2018.v10i1.549 ◽

2018 ◽

Vol 10 (1) ◽

Author(s):

Robert Haynes ◽

Ghanashyam Joshi ◽

Natasha Bradley

Keyword(s):

Machine Learning ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Initiation ◽

Crack Length ◽

Crack Growth ◽

Particle Filtering ◽

Fatigue Crack Initiation ◽

Length Measurements ◽

Aluminum 7075

Constant stress amplitude fatigue tests were conducted on the notch pre-cracked Aluminum 7075-T6 rivet hole dog-bone coupons. Monitoring of visible surface crack length by special surface engraving using digital microscope images and by ultrasonic sensors signals was carried out to yield fatigue crack length measurements in relation to number of fatigue cycles applied. The experimental results provide ultrasonic sensor validation for fatigue crack length measurements. Fracto-graphic examination of failed fatigue surfaces has provided further confirmation of notch pre-crack length, crack initiation process, and crack growth marker bands. These experimental inputs were used in NASGRO and AFGROW software fatigue crack growth simulations. The simulation results did not match the crack initiation fatigue life measured by experiments. However, there was good agreement with crack growth simulations of larger cracks. Hence, we plan to develop a machine learning application that will learn the fatigue crack initiation and crack growth processes from data obtained from our own experiments and other fatigue data available from AFGROW databases. Nonlinear AutoRegressive models with eXogenous input (NARX) artificial neural network were used to predict crack growth longer than 5.0-mm. Particle filtering modeling with Bayesian updating was applied to these experimental data for prognostics of fatigue crack growth. A concept design and preliminary implementation results will be presented.

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Fatigue Crack Initiation and Growth Behaviour of 316L Stainless Steel Manufactured Through Selective Laser Melting

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2017-65410 ◽

2017 ◽

Cited By ~ 1

Author(s):

C. M. Davies ◽

H. Thomlinson ◽

P. A. Hooper

Keyword(s):

Stainless Steel ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Initiation ◽

Crack Growth ◽

316L Stainless Steel ◽

Fatigue Crack Initiation ◽

Compact Tension ◽

Growth Behaviour ◽

Laser Melting

Selective Laser Melting (SLM) is a relatively new manufacturing technique that offers many benefits. However the utilisation of SLM manufactured components depends on the assurance of their integrity during operation. Tensile and high cycle fatigue tests have been performed on uniaxial samples manufactured using SLM of 316L stainless steel to examine the elastic-plastic deformation and fatigue crack initiation behaviour of the material. In addition, the fatigue crack growth behaviour has been determined from tests on compact tension samples manufactured using SLM. The influence of build orientation has been examined on the compact tension samples. The results are compared to values obtained from conventional manufacturing methods. The tensile samples have a higher strength but significantly lower ductility than wrought material. The fatigue strength of the SLM material was substantially less than wrought material, though a similar fatigue limit maybe seen, this may be attributed to porosity in the material. The fatigue crack growth rate of the SLM material was 5–10 times faster, for a given stress intensity factor, than wrought materials and strongly depended on crack orientation in relation to the build direction.

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A Probabilistic Micromechanical Code for Predicting Fatigue Life Variability: Model Development and Application

Volume 4: Turbo Expo 2005 ◽

10.1115/gt2005-68983 ◽

2005 ◽

Author(s):

K. S. Chan ◽

M. P. Enright

Keyword(s):

Fatigue Crack ◽

Fatigue Life ◽

Fatigue Crack Growth ◽

Crack Initiation ◽

Crack Growth ◽

Model Development ◽

Fatigue Crack Initiation ◽

Crack Size ◽

Crack Initiation Life ◽

Variability Model

This paper summarizes the development of a probabilistic micromechanical code for treating fatigue life variability resulting from material variations. Dubbed MicroFaVa (Micromechanical Fatigue Variability), the code is based on a set of physics-based fatigue models that predict fatigue crack initiation life, fatigue crack growth life, fatigue limit, fatigue crack growth threshold, crack size at initiation, and fracture toughness. Using microstructure information as material input, the code is capable of predicting the average behavior and the confidence limits of the crack initiation and crack growth lives of structural alloys under LCF or HCF loading. This paper presents a summary of the development of the code and highlights applications of the model to predicting the effects of microstructure on the fatigue crack growth response and life variability of the α + β Ti-alloy Ti-6Al-4V.

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Fatigue Crack Initiation in Pressure Vessel Steels Using a Distance Parameter

Design and Analysis of Pressure Vessels and Piping: Implementation of ASME B31, Fatigue, ASME Section VIII, and Buckling Analyses ◽

10.1115/pvp2003-2192 ◽

2003 ◽

Author(s):

Somnath Chattopadhyay

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Initiation ◽

Crack Growth ◽

Fatigue Crack Initiation ◽

Crack Tip ◽

Pressure Vessels ◽

Linear Elastic ◽

Short Cracks ◽

Distance Parameter

The propagation behavior of short cracks cannot be studied by linear elastic methods because of large plastic region near the crack tip, as well as a breakdown in correlation of the stress intensity factor with the fatigue crack growth rates. The proposed fatigue design approach incorporates a distance parameter in conjunction with linear elastic fracture mechanics and effectively integrates long and short crack growth test data. This distance parameter is a material constant that allows for the effects of (a) large-scale plasticity, (b) crack closure and (c) fatigue crack threshold. Furthermore, this parameter can be used to successfully predict fatigue crack growth behavior of short cracks. The practical application of this method to study fatigue crack initiation in pressure vessels rests on the concept that initiation occurs only when the material ahead of the crack tip is damaged enough by cyclic straining.

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Shape of a crack growth front under fatigue in the range of 106 - 107cycles

ANNUAL JOURNAL OF TECHNICAL UNIVERSITY OF VARNA BULGARIA ◽

10.29114/ajtuv.vol4.iss1.162 ◽

2020 ◽

Vol 4 (1) ◽

pp. 30-39

Author(s):

Georgi Georgiev Georgiev

Keyword(s):

Stainless Steel ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Initiation ◽

Crack Growth ◽

Fatigue Crack Initiation ◽

Growth Front ◽

Physical Endurance ◽

Similar Materials ◽

3D Computer Model

The paper explores the shape of a fatigue crack initiation in the interval of 106-107cycles of duplex stainless steel, commercially designated as SAF 2507. Particular emphasis is placed upon the development of the crack’s growth front and its subsequent expansion in three directions x, y, z. Created, accordingly, on the basis of the experimentally obtained results, is a 3D computer model to help provide a further prediction for the physical endurance of similar materials. The growth of a fatigue crack is modeled by using The SolidWorks and AutoCAD software tools for constructing the model of fatigue crack growth.

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