Methodical approach for studying kinetics of short and long fatigue cracks growth for irradiated reactor materials. Part 1. Statement of problem. The effect of the initial notch acuity on the fatigue crack rate on small-sized specimens

2019 ◽  
pp. 191-204 ◽  
Author(s):  
V. I. Smirnov ◽  
A. J. Minkin ◽  
B. Z. Margolin ◽  
V. I. Kokhonov
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth ◽  
Growth Kinetics ◽  
Fatigue Cracks ◽  
Stress Concentration Zone ◽  
Concentration Zone ◽  
Methodical Approach ◽  
Reactor Materials ◽  
Kinetics Of

The paper considers methodical issues in the experimental research of fatigue crack growth kinetics when testing irradiated small-sized specimens. The effect of the initial notch acuity is studied on the long crack growth rate. The stress concentration zone sizes are estimated for notches of various types. A brif literature review of the main problems in the study of the growth kinetics of short fatigue cracks has been performed. The tasks of further research are formulated. 

Fatigue crack growth at stress concentrators under spectrum loading

2005 ◽  
Vol 40 (2) ◽  
pp. 117-127
Author(s):  
R. V Prakash
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Growth ◽  
Surface Defects ◽  
Fatigue Cracks ◽  
Mapping Technique ◽  
Critical Dimensions ◽  
Small Cracks ◽  
Stress Raisers ◽  
Kinetics Of

Fatigue cracks initiate at stress raisers such as notches, discontinuities, and surface defects. Many of the field failures that indicate the presence of a fatigue crack at failure can be traced to crack initiation from one or more crack initiation sites and merger of cracks over a period of service. Substantial service life is spent in the growth of small cracks from an initial size of few micrometres before they coalesce and grow to critical dimensions that cause fracture. This paper summarizes research that was carried out in order to understand the kinetics of crack growth of small cracks at notches under simulated FALSTAFF service loading. This paper also presents a method used to understand crack growth kinetics in a pin-loaded lug joint through a crack-front-mapping technique.

Crack Growth Path in Specimens with Rectangular Section under Bending with Torsion

2014 ◽  
Vol 224 ◽  
pp. 133-138
Author(s):  
Sebastian Faszynka ◽  
Dariusz Rozumek ◽  
Janusz Lewandowski
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Fatigue Cracks ◽  
Experimental Tests ◽  
Stress Intensity Factor Range ◽  
Crack Growth Path

The paper presents the results of tests on the fatigue crack growth rate for a constant moment amplitude under combined bending with torsion in the aluminium alloy AlCuMg1. The tests were performed under different values of the stress ratio R. Plane specimens with stress concentrators in form of the external one-sided sharp notch were tested. The results of experiments were described on graphs of the fatigue crack growth rate versus changes of the stress intensity factor range ΔK. A non-uniform fatigue cracks growth on both lateral surfaces of specimens was observed during experimental tests.

Mechanistic Features of Short Fatigue Crack Growth Kinetics for High Strength Steels in Sea Water

2004 ◽  
Vol 128 (2) ◽  
pp. 169-176 ◽  
Author(s):  
Kijoon Kim ◽  
William H. Hartt
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Kinetics ◽  
High Strength Steels ◽  
High Strength ◽  
Offshore Structures ◽  
Rate Kinetics

The importance of fatigue to the integrity of offshore structures is well documented. Also, it has been demonstrated that much of the service life of members and components such as tendons and risers is comprised of an extension of cracks from initial surface defects to a size of several millimeters. At the same time, the growth kinetics of such short cracks has been shown to be more rapid than those of long cracks; however, it is upon the latter that most historical studies have focused. In the present paper, the results of scanning electron microscope fractographic analyses performed upon five high strength steels fatigued in air and seawater are presented. These revealed fracture surface morphology distinctions that were a unique function of material, environment (air versus seawater), potential, and crack length, and that the enhanced fatigue crack growth rate in the short crack regime was relatable to these morphological features. Of particular importance were (1) the development of secondary cracks as a precursor for the short crack to long crack growth rate kinetics transition, and (2) a change in fracture mode, either from quasicleavage (QC) to microvoid coalescence (MVC) or from intergranular to QC or MVC with increasing crack length. The results are discussed within the context of (1) alloy development for applications where a significant portion of the fatigue life transpires while cracks are relatively short such that the enhanced growth rate kinetics apply; and (2) materials selection and fatigue design of riser and tendon systems for deep water offshore structures.

scholarly journals Fatigue Crack Growth Under General-Yielding Cyclic-Loading

1986 ◽  
Vol 108 (3) ◽  
pp. 201-205 ◽  
Author(s):  
Zheng Minzhong ◽  
H. W. Liu
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
The Finite Element Method ◽  
General Yielding

In low cycle fatigue, cracks are initiated and propagated under general-yielding cyclic-loading. For general-yielding cyclic-loading, Dowling and Begley have shown that fatigue crack growth rate correlates well with the measured ΔJ. The correlation of da/dN with ΔJ has also been studied by a number of other investigators. However, none of these studies has correlated da/dN with ΔJ calculated specifically for the test specimens. Solomon measured fatigue crack growth in specimens in general-yielding cyclic-loading. The crack tip fields for Solomon’s specimens are calculated, using the finite element method, and the J-values of Solomon’s tests are evaluated. The measured crack growth rate in Solomon’s specimens correlates very well with the calculated ΔJ.

Setup for studying the kinetics of crack growth in cyclic bending tests

2020 ◽  
Vol 86 (7) ◽  
pp. 59-64
Author(s):  
V. N. Pustovoit ◽  
S. A. Grishin ◽  
V. V. Duka ◽  
V. V. Fedosov
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Computer Processing ◽  
Crack Development ◽  
Potential Difference ◽  
Fatigue Crack Development ◽  
Kinetics Of

The goal of the study is analysis of the features of fatigue cyclic fracture of steels. An installation has been designed to induce fatigue cracks and to study the kinetics of fatigue crack development. Crack growth is recorded by the method of potential difference. The data on the crack growth kinetics were processed on a computer using LGraph2 programs and Excel spreadsheets. When studying the kinetics of the fatigue crack development, the electrodes were soldered to the edges of the initial notch of the sample and time dependence of the potential difference was recorded on a computer during crack growth. To interpret the experimental data, a calibration chart in the coordinates «potential difference (U) – the crack length (Lcr)» constructed on the basis of the millivoltmeter readings was used, with due regard for the size of the sample section, current flow and length of the fatigue crack. Cyclic loading of the sample resulted in a stepwise character of the crack growth: first occurred zone of plastic deformation of the metal is then followed by accumulation of stresses of a certain size, their relaxation in the form of a crack and sudden crack growth. An abrupt crack growth is clearly visible on a graph of the fatigue crack growth rate obtained upon computer processing of experimental data. Using a graphical editor KOMPAS, a graph was constructed which characterized the growth of the fatigue crack against the number of cycles of fatigue tests for bending. The experimental setup provides the possibility of fatigue crack formation for impact tests, determination of the work of crack propagation, as well as studying of the kinetics of crack development and computer processing of experimental data.

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