Evaluation of Crack Growth Retardation Effect Due to Nano-scale Voids Based on Molecular Dynamics Method

2011 ◽  
Vol 1297 ◽  
Author(s):  
Shin Taniguchi ◽  
Toshihiro Kameda
Keyword(s):  
Molecular Dynamics ◽  
Crack Growth ◽  
Growth Retardation ◽  
Md Simulations ◽  
Retardation Effect ◽  
Shielding Effect ◽  
Nano Scale ◽  
Optimum Placement ◽  
Yield Stress Increase ◽  
Crack Growth Retardation

ABSTRACTThis study has investigated the crack growth retardation effect due to plural nano-scale voids in Cu single crystals using a molecular dynamics (MD) method. Focusing on an interaction between nano-scale voids and dislocations, we have evaluated the optimum placement for crack growth retardation. MD simulations showed that the dislocation activity was further enhanced due to plural nano-scale voids continuously placed on the primary slip direction. The significant ductility enhancement and slight yield stress increase due to the crack shielding effect of nano-scale voids were observed.

Effect of Hydrostatic Retest on the Fatigue Behavior of a Steel Gas Cylinder

1991 ◽  
Vol 113 (4) ◽  
pp. 556-559 ◽  
Author(s):  
G. S. Bhuyan ◽  
A. Akhtar ◽  
C. T. L. Webster
Keyword(s):  
Beneficial Effect ◽  
Crack Growth ◽  
Growth Retardation ◽  
Fatigue Behavior ◽  
Crack Size ◽  
Retardation Effect ◽  
Gas Cylinder ◽  
Post Test ◽  
Crack Growth Retardation

Retardation effect of the hydrostatic test on the subsequent crack growth in an AISI 4130X steel gas cylinder has been predicted. The post-test retardation period depends upon the size of the crack; the smaller the crack size the larger the crack growth retardation period. The beneficial effect of the present recertification test, conducted at 5-yr interval at a pressure of 1.67 times the design service pressure, depends upon the number of pressure cycles incurred between retests.

Fatigue Crack Growth Retardation in Titanium Alloy

2017 ◽  
Author(s):  
Sachin Biradar ◽  
Jyoti Shankar Jha ◽  
Sushil Mishra ◽  
Asim Tewari
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Length ◽  
Crack Growth ◽  
Growth Retardation ◽  
Retardation Effect ◽  
Number Of Cycles ◽  
Crack Growth Retardation

The gas turbine components undergo fatigue load spectrum of variable amplitude loading. In this study, fatigue crack growth rate after multiple cycles of tensile overload has been investigated in Ti-2.77Sn-0.48Cu-1.15Fe-6.61V alloy. The overload at the crack tip produces the plastic zone at the vicinity, which retards the crack growth. Crack growth retardation effect has been studied at 15% and 25% overload percentages to observe its retardation effect. The multiple overloads applied after fixed interval of cycles produces a plastic region around the crack. After reloading the specimen further with constant loading, the crack growth rate is retarded thus causing increase in the fatigue life, which is observed in the graph of crack length vs number of cycles. The microstructure study has been carried out using Scanning Electron Microscope (SEM) and Electron Back Scatter Diffraction (EBSD), which gives qualitative information of strain to characterize the fatigue crack growth. The slope of crack length vs number of cycles before and after tensile peak overload was compared to evaluate the retardation effect at varying overload percentages.

Estimation of fatigue crack growth retardation due to crack branching

2004 ◽  
Vol 29 (4) ◽  
pp. 446-452 ◽  
Author(s):  
D.G. Pavlou ◽  
N.V. Vlachakis ◽  
M.G. Pavlou ◽  
V.N. Vlachakis
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Retardation ◽  
Crack Branching ◽  
Crack Growth Retardation

The Effect of Crack Growth Retardation when Comparing Constant Amplitude to Variable Amplitude Loading in an Aluminium Alloy

2014 ◽  
Vol 891-892 ◽  
pp. 948-954 ◽  
Author(s):  
Madeleine Burchill ◽  
Simon A. Barter ◽  
Michael Jones
Keyword(s):  
Growth Rate ◽  
Fatigue Life ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Growth Retardation ◽  
Crack Front ◽  
Constant Amplitude ◽  
Variable Amplitude ◽  
Growth Increments ◽  
Crack Growth Retardation

It has often been observed that the growth of short fatigue cracks under variable amplitude (VA) cyclic loading is not well predicted when utilising standard constant amplitude (CA) crack growth rate/stress intensity data (da/dN v DK). This paper outlines a coupon fatigue test program and analyses, investigating a possible cause of crack growth retardation from CA-only testing. Various test loading spectra were developed with sub-blocks of VA and CA cycles, then using quantitative fractography (QF) the sub-block crack growth increments were measured. Comparison of these results found that, after establishing a consistent uniform crack front using a VA load sequence, the average crack growth rate then progressively slowed down with the number of subsequent CA load cycles applied. Further fractographic investigation of the fracture surface at the end of each CA and VA sub-block crack growth, identified significant crack front morphology differences. Thus it is postulated that a variation or deviation from an efficient crack path is a driver of local retardation in short crack growth during CA loading. This may be a source of error in analytical predictions of crack growth under VA spectra loading that may need to be considered in addition to other potential effects such asless closure whilst cracks are small. For aircraft designers, using solely CA data for fatigue life predictions this may result in non-conservative estimates of total crack fatigue life, producing unexpected failures or an increased maintenance burden.

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