PREDICTION FOR FATIGUE CRACK GROWTH IN NOTCHED PLATES

2012 ◽  
Vol 06 ◽  
pp. 269-274
Author(s):  
K. SHOJIMA ◽  
K. YANASE ◽  
M. ENDO
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Plastic Behavior ◽  
Short Cracks ◽  
Major Factors

The notch is usually unavoidable in designing various mechanical components. As well known, those notches significantly influence the fatigue life and fatigue strength of materials. In addition, most fatigue cracks spend the vast majority of their lives as short cracks, and the behavior of such flaw is of significant importance in determining the fatigue lifetime of notched components. Correspondingly, in this research, we investigate the fatigue crack growth behavior and fatigue strength of notched plates. For the proposed method, the elastic-plastic behavior, the Kitagawa effect and the crack closure are taken into account as the major factors responsible for the peculiar behavior of small fatigue cracks emanating from notches. Regarding the experiment, the fatigue tests were conducted using the plates with a circular notch under uniaxial loading condition. The proposed approach is validated by comparing the predicted results to the experimental data.

Estimation of Fatigue Strength of Fabricated Component

2007 ◽  
Author(s):  
Duangporn Ounpanich ◽  
Yoshiharu Mutoh ◽  
Kenji Yoshii
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Defect ◽  
Fatigue Tests ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Threshold Region ◽  
Sinusoidal Waveform

This paper deals with the fatigue performance of fabricated component. The plain fatigue and fatigue crack growth tests were performed. The rectangular bar specimens sectioned from the fabricated components after rolling, forming and cold spinning processes were prepared. Four-point bend fatigue tests of the specimens with as-fabricated surfaces were carried out at a stress ratio of 0.1 and a frequency of 20 Hz with a sinusoidal waveform. The crack growth behavior of specimens at various stages of fabricating process was also investigated. The fatigue test results indicated that surface morphology and surface defect induced by each stage of fabricating process strongly degraded the fatigue strength. The limited influence of fabricating process on crack growth behavior was noticed only in the threshold region. Fatigue strength and fatigue life were estimated based on fracture mechanics approach using the fatigue crack growth curve obtained and the surface defect depth observed on the fabricated surface. The estimated fatigue strength and the experimental results were in good agreement.

A Method for the Analysis of the Growth of Short Fatigue Cracks

1995 ◽  
Vol 117 (4) ◽  
pp. 408-411 ◽  
Author(s):  
A. J. McEvily ◽  
Y.-S. Shin
Keyword(s):  
Experimental Data ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Material Constant ◽  
Plastic Zone Size ◽  
Surface Cracks ◽  
Zone Size ◽  
Short Cracks

A method for the analysis of the fatigue crack growth rate for short cracks has been developed and is applied to the case of fatigue crack growth of short surface cracks in a 1045 carbon steel. The method entails three modifications to standard LEFM procedures. These modifications include the use of a material constant to bridge between smooth and cracked specimen behavior, consideration of the plastic zone size to crack length ratio, and incorporation of the development of crack closure. Comparisons are made between calculations based upon this approach and experimental data.

Effect of KIII on Fatigue Crack Growth Behavior

2010 ◽  
Author(s):  
Masanori Kikuchi ◽  
Yoshitaka Wada ◽  
Chikako Ohdama
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Crack Growth Simulation ◽  
Slant Surface ◽  
Cracked Specimens

Mixed mode fatigue tests are conducted using surface cracked specimen. Slant surface cracked specimens are made where crack angle is 15°, 30°, 45° and 60°. It is shown that factory roof is made at deepest point of surface crack due to ΔKIII, and crack growth rate decreases by the factory roof. Fatigue crack growth is simulated using S-version FEM (Finite Element Method) using crack growth criteria. It is shown that conventional crack growth criteria are not available to predict fatigue crack growth with factory roof. In this study, modified criterion for the prediction of crack growth rate is proposed. By using this criterion, fatigue crack growth simulation is conducted, and results are compared with those of experiments and discussed.

On the Fatigue Crack Growth Behavior of a Nitrided and Shot Peened Steel

2007 ◽  
Vol 345-346 ◽  
pp. 375-378 ◽  
Author(s):  
Mario Guagliano ◽  
Laura Vergani
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Residual Stresses ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Initiation Point ◽  
Growth Properties ◽  
Micro Hole ◽  
Rotating Bending Fatigue

In this paper the fatigue crack growth properties of a nitrided shot-peened steel is dealt with: different peening intensities were considered and the resulting residual stresses measured by means of an X-ray diffractometer. Rotating bending fatigue tests were executed on specimens with a blind micro-hole, acting as a pre-existent crack. The results allowed determining the threshold of propagation of the nitrided and of nitrided and shot peened material. It was also possible to relate the crack initiation point with the applied and the residual stresses.

Effects of Laser Peening on Fatigue Crack Behaviors in Pre-Cracked Cast Aluminum Alloy

2007 ◽  
Vol 345-346 ◽  
pp. 255-258 ◽  
Author(s):  
Yasuo Ochi ◽  
Kiyotaka Masaki ◽  
Takashi Matsumura ◽  
Yuji Sano ◽  
Koichi Akita ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Crack Growth Behavior ◽  
Cast Aluminum Alloy ◽  
Laser Peening ◽  
Cast Aluminum ◽  
Surface Fatigue

In order to investigate effects of low energy laser peening (LP) without protective coating on surface fatigue crack growth behavior, rotating bending fatigue tests were carried out on cast Al-Si-Mg aluminum alloy with a pre-cracked round bar type specimens. As the results, the fatigue crack growth was restrained by the compressive residual stress induced by laser peening treatment. And also, the three dimensional (3D) image of surface fatigue cracks was reconstructed by using a micro computed tomography (μCT) with phase contrast technique. It was also shown that the surface crack growth was restrained for the laser peened materials.

Fatigue Crack Growth and Threshold Behavior of DMLS Ti6Al4V

2017 ◽  
Vol 267 ◽  
pp. 157-161
Author(s):  
Radomila Konečná ◽  
Ludvík Kunz ◽  
Pavel Pokorný ◽  
Gianni Nicoletto
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Processing Parameters ◽  
Crack Growth Behavior ◽  
Threshold Values ◽  
Stress Relieving ◽  
Crack Growth Curve

Growth of long fatigue cracks in Ti6Al4V alloy manufactured by direct metal laser sintering (DMLS) was investigated. Two DMLS systems, EOSINT M270 and EOSINT M290, with different process parameters were used for production of CT specimens having three different orientations of crack propagation with respect to the DMLS build direction. The as-built specimens were stress relieved at 740 °C. The fatigue crack growth curve and the threshold values of the stress intensity factor for crack propagation were experimentally determined. It has been found that the chosen DMLS processing parameters and the used stress relieving procedure results in material exhibiting isotropic crack growth behavior, i.e. the crack growth was found to be independent of the DMLS build direction. The fatigue crack growth rates and the threshold values for the crack growth were compared with published results characterizing the as-built material and material after different post processing heat treatments.

A Methodology for Predicting Variability in Microstructurally Short Fatigue Crack Growth Rates

1997 ◽  
Vol 119 (2) ◽  
pp. 171-179 ◽  
Author(s):  
Ken Gall ◽  
Huseyin Sehitoglu ◽  
Yavuz Kadioglu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Growth Parameters ◽  
Fatigue Cracks ◽  
Upper And Lower Bounds ◽  
Short Cracks ◽  
Band Size ◽  
Crack Growth Rates

A finite element model, which implements single crystal constitutive relationships, was used to simulate fatigue cracks growing at the microstructural level. Plastic deformation (slip) was allowed along two specified microscopic crystallographic planes. As the orientations of the slip systems were changed several crucial fatigue crack growth parameters, measured over all possible orientations, were found to vary: (1) crack tip forward slip band size, rp, 0.03 ≤ rp/(Kmax/λo)2 ≤ 0.31 where λo is the critical resolved shear stress on a slip system, (2) crack opening displacement, δ, 1.2 ≤ δ/(Kmax2/Emσo) ≤ 7.8 where Em and σo are the elastic modulus and yield stress of a polycrystalline material with many randomly oriented double slip crystals, and(3) crack closure level, Sopen/Smax, 0.02 ≤ Sopen/Smax ≤ 0.35. Corresponding to these differences in crack growth parameters, crack growth laws were used to estimate the expected changes in crack growth rates when microstructurally short cracks grow through grains with different crystallographic orientations. The resulting predictions form approximate upper and lower bounds on crack growth rates for microstructurally short cracks. For several different materials, the crack growth rate variability predictions were in the range 7 ≤ (da/dN)(max)/(da/dN)(min) ≤ 37, which is consistent with experimentally measured variations.

Study on Banded Structure in Low Carbon Vessel Plate for Nuclear Power Plant

2010 ◽  
Vol 44-47 ◽  
pp. 1763-1766
Author(s):  
Fei Xue ◽  
Zhi Feng Luo ◽  
Wei Wei Yu ◽  
Zhao Xi Wang ◽  
Lu Zhang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Nuclear Power ◽  
Power Plants ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Low Carbon ◽  
Banded Structure ◽  
Crack Retardation

In this paper, the role of the pearlite-banded structure on fatigue crack growth behavior was investigated on carbon vessel plate material SA516, which is commonly used in the nuclear power plants. Along pearlite-banded orientation, in situ fatigue tests indicate that the crack initiated and propagated in the ferrite and then extended along the ferrite-pearlite interface when it met pearlitic colony. For comparison, the cyclic loading was also carried out perpendicular to the banding direction of the microstructure, and an intense crack branching was observed which led to fatigue crack retardation. Besides, the orientation perpendicular to banded pearlite in the investigated ferrite-pearlite steel was found to have a lower fatigue crack growth rate.

Fatigue Lifetime and Crack Growth Behavior of WC-Co Cemented Carbide

2014 ◽  
Vol 891-892 ◽  
pp. 955-960 ◽  
Author(s):  
Hiroko Mikado ◽  
Sotomi Ishihara ◽  
Noriyasu Oguma ◽  
Kenichi Masuda ◽  
Shingo Kawamura
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Growth Behavior ◽  
Cemented Carbide ◽  
Fatigue Properties ◽  
Crack Growth Behavior ◽  
Fatigue Lifetime

It is well known that WC-Co cemented carbides have excellent wear resistance. However, information about their fatigue crack growth behavior and fatigue properties is limited. In the present study, rotating bending fatigue tests were carried out on a fine grained WC-Co cemented carbide to evaluate its fatigue lifetime and crack growth behavior. From observations of the micro-notched specimen surface during the fatigue process, it was revealed that most of the fatigue lifetime of the tested WC-Co cemented carbide is comprised of crack growth cycles. Using the basic equation of fracture mechanics, the relation between the rate of fatigue crack growth da/dN and the maximum stress intensity factor Kmax of the WC-Co cemented carbide was derived. From this relation, both the threshold intensity factor Kth and the fatigue fracture toughness Kfc of the material were determined. Fatigue lifetime of the WC-Co cemented carbide was estimated based on the fatigue crack growth law.

Effect of KIII on Fatigue Crack Growth Behavior

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Masanori Kikuchi ◽  
Yoshitaka Wada ◽  
Chikako Ohdama
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Crack Growth Simulation ◽  
Slant Surface ◽  
Cracked Specimens

In this study, mixed-mode fatigue tests are conducted using surface-cracked specimens. Slant surface-cracked specimens are prepared with crack angles of 15 deg, 30 deg, 45 deg, and 60 deg. It is shown that a “factory roof” fracture is formed at the deepest point of the surface crack due to ΔKIII and causes the crack growth rate to decrease. Additionally, fatigue crack growth is simulated using the superposition finite element method (FEM) with crack growth criteria. It is shown that conventional crack growth criteria are not applicable to factory roof fractures. Finally, a modified criterion for the prediction of crack growth rate is proposed, fatigue crack growth simulation is conducted using this criterion, and the results are compared with experimental results.

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