The Influence of Strain Conditions in Steel Samples on the Fatigue Crack Growth and Delay after Overload

2014 ◽  
Vol 224 ◽  
pp. 151-156
Author(s):  
Krzysztof Werner
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress State ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Strain State ◽  
Plane Stress State ◽  
Test Results ◽  
Single Overload ◽  
Flat Steel

The work presents the results of the analysis of fatigue crack growth in flat steel samples for different strain conditions on crack tip in the sample. Growth of fatigue crack in the samples was studied in conditions of a plane strain state, plane stress state and in the transitory zone between those states. Test results showed a clear influence of these conditions on the fatigue crack growth rate. The paper also includes the test results of effectiveness of retardation of fatigue crack growth after single overload cycles used in different strain conditions.

Effects of a Single Overload on Fatigue Crack Growth of Type 316 Stainless Steel

2021 ◽  
Author(s):  
Koji Miyoshi ◽  
Masayuki Kamaya
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Opening ◽  
Constant Amplitude ◽  
Single Overload ◽  
Tensile Overload

Abstract The effect of a single overload on the fatigue crack growth rate was investigated for Type 316 stainless steel. Fatigue crack growth tests were conducted by controlling strain and load. Tensile and compressive overloads were applied during constant amplitude cycling. The overload ratio, which was defined as the ratio of overload size to baseline constant amplitude, was also changed. The constant amplitude tests were conducted at the strain or the stress ratio of −1.0 which was defined as the ratio of the minimum value to the maximum value. The crack opening point was obtained by the unloading elastic compliance method. The crack growth rate increased after the single compressive overload. The accelerating rate increased with the overload ratio. In contrast, not only the acceleration but also the retardation of the crack growth rate was observed for some tensile overload cases. The crack growth rate increased for relatively small tensile overload cases and decreased for relatively large tensile overload cases. The change in the crack opening level was examined. The crack growth rates after tensile and compressive single overloads correlated with the effective strain and stress intensity factor ranges both for load and strain controlling modes.

Effects of a Single Overload Event on the Fatigue Crack Growth Rate of a Low Alloyed Rotor Steel

2008 ◽  
Author(s):  
J. C. Le Roux ◽  
F. Hasnaoui
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Stress Ratio ◽  
Numerical Results ◽  
Experimental Results ◽  
Single Overload

The aim of this work is to study the effect of the overload on the fatigue crack growth rate properties of a low alloyed steel used for rotor disk. On one hand, experimental fatigue tests during which a single overload event is applied are performed on CT specimens. Different loading conditions are imposed in order to study the effects of these parameters on the retardation of the fatigue crack due to the overload. On the other hand, two dimensions elastic plastic Finite Element calculations of crack propagation using nodes release method were used to estimate the effects of a single overload event on the fatigue crack growth rate. Different loading conditions, as for the experimental tests, are used in order to study numerically the effects of these parameters on the retardation of the fatigue crack due to the overload. The experimental and numerical results show the decrease of the crack growth rate due to the overload. This decrease depends on different parameters as overload ratio, stress ratio used for the constant amplitude cyclic loading and ΔK at which the overload is applied. From experimental test results, it can be observed that the decrease is as significant as the overload ratio is high, and as the ΔK at which overload is applied and stress ratio are low. Numerical results show similarities with experimental results, for instance the decrease of the fatigue crack growth is linked to the increase of the overload ratio or to the decrease to the ΔK at which overload is applied. Differences are also observed i.e. the increase of the stress ratio seems to increase the effect of the overload in the numerical calculations in contrary of the experimental results. By comparing to the numerical results, the quality of the results obtained from simplified models has been assessed in regard of the overload effect. A modified Kim and al. model seems to be representative of the different effects of the overload on the fatigue crack growth rate. The future work to be done consists to improve the comparison between experimental and numerical studies.

Investigation on the Abnormal Crack Front in Fatigue Crack Growth Rate Test for Thick High Tensile Steel Plate

2013 ◽  
Author(s):  
Yan Dong ◽  
Jingxia Yue ◽  
Qian Yi ◽  
Heng Zhou ◽  
Hao Huang
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress State ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Crack Front ◽  
Abnormal Behavior ◽  
Rate Test

Complex environmental loads unavoidably lead to fatigue damage in marine structures, and it becomes worse in high tensile steel thick-welded structure which has typical tri-axial stress state and the feature of brittleness. In this paper, a standard fatigue crack growth rate test for high-tensile steel Q370QE with thickness of 36 mm was carried out, and some material parameters and the threshold of stress intensity factor were obtained. Then, the abnormal behavior of a crack front during crack growth was analyzed by finite element method. Accordingly, the varying tendency of crack front shape could be qualitatively defined, and the plastic zoon at both flat and slope crack fronts for different crack depth was demonstrated based on plasticity analysis. Finally, local constraint factor was introduced to quantitatively describe the stress state along the crack front with the growth of fatigue crack, which provided proper explanation to why the crack front changes from slope to straight with the crack growing.

scholarly journals Study on the Influence of the Gurson–Tvergaard–Needleman Damage Model on the Fatigue Crack Growth Rate

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1183
Author(s):  
Edmundo R. Sérgio ◽  
Fernando V. Antunes ◽  
Diogo M. Neto ◽  
Micael F. Borges
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Plastic Strain ◽  
Crack Growth ◽  
Damage Model ◽  
Crack Tip ◽  
Strength Parameter ◽  
Stress Intensity Factor Range

The fatigue crack growth (FCG) process is usually accessed through the stress intensity factor range, ΔK, which has some limitations. The cumulative plastic strain at the crack tip has provided results in good agreement with the experimental observations. Also, it allows understanding the crack tip phenomena leading to FCG. Plastic deformation inevitably leads to micro-porosity occurrence and damage accumulation, which can be evaluated with a damage model, such as Gurson–Tvergaard–Needleman (GTN). This study aims to access the influence of the GTN parameters, related to growth and nucleation of micro-voids, on the predicted crack growth rate. The results show the connection between the porosity values and the crack closure level. Although the effect of the porosity on the plastic strain, the predicted effect of the initial porosity on the predicted crack growth rate is small. The sensitivity analysis identified the nucleation amplitude and Tvergaard’s loss of strength parameter as the main factors, whose variation leads to larger changes in the crack growth rate.

Influence of reactor water of nominal parameters on fatigue crack growth rate in 15Kh2NMFA steel

1985 ◽  
Vol 21 (2) ◽  
pp. 130-133
Author(s):  
V. I. Pokhmurskii ◽  
A. S. Zubchenko ◽  
A. A. Popov ◽  
I. P. Gnyp ◽  
V. M. Timonin ◽  
...  
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Reactor Water ◽  
15Kh2nmfa Steel
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