scholarly journals Effect of Initial Crack Length and Specimen Size on Delayed Failure Time in Perfectly Brittle Materials

1998 ◽  
Vol 106 (1229) ◽  
pp. 70-74
Author(s):  
Taketoshi NOJIMA
Keyword(s):  
Crack Length ◽  
Failure Time ◽  
Brittle Materials ◽  
Initial Crack ◽  
Specimen Size ◽  
Initial Crack Length ◽  
Delayed Failure

Initial crack length on the interlaminar fracture of woven carbon/epoxy laminates

2015 ◽  
Vol 16 (4) ◽  
pp. 894-901 ◽  
Author(s):  
P. N. B. Reis ◽  
J. A. M. Ferreira ◽  
F. V. Antunes ◽  
J. D. M. Costa
Keyword(s):  
Crack Length ◽  
Initial Crack ◽  
Initial Crack Length ◽  
Interlaminar Fracture

A finite element model on effects of impact load and cavitation on fatigue crack propagation in mechanical bileaflet aortic heart valve

2008 ◽  
Vol 222 (7) ◽  
pp. 1115-1125 ◽  
Author(s):  
H Mohammadi ◽  
R J Klassen ◽  
W-K Wan
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Length ◽  
Heart Valve ◽  
Heart Valves ◽  
Element Model ◽  
Initial Crack ◽  
Initial Crack Length ◽  
Element Approach ◽  
The Impact

Pyrolytic carbon mechanical heart valves (MHVs) are widely used to replace dysfunctional and failed heart valves. As the human heart beats around 40 million times per year, fatigue is the prime mechanism of mechanical failure. In this study, a finite element approach is implemented to develop a model for fatigue analysis of MHVs due to the impact force between the leaflet and the stent and cavitation in the aortic position. A two-step method to predict crack propagation in the leaflets of MHVs has been developed. Stress intensity factors (SIFs) are computed at a small initiated crack located on the leaflet edge (the worst case) using the boundary element method (BEM). Static analysis of the crack is performed to analyse the stress distribution around the front crack zone when the crack is opened; this is followed by a dynamic crack analysis to consider crack propagation using the finite element approach. Two factors are taken into account in the calculation of the SIFs: first, the effect of microjet formation due to cavitation in the vicinity of leaflets, resulting in water hammer pressure; second, the effect of the impact force between the leaflet and the stent of the MHVs, both in the closing phase. The critical initial crack length, the SIFs, the water hammer pressure, and the maximum jet velocity due to cavitation have been calculated. With an initial crack length of 35 μm, the fatigue life of the heart valve is greater than 60 years (i.e. about 2.2×109 cycles) and, with an initial crack length of 170 μm, the fatigue life of the heart valve would be around 2.5 years (i.e. about 9.1×107 cycles). For an initial crack length greater than 170 μm, there is catastrophic failure and fatigue cracking no longer occurs. A finite element model of fatigue analysis using Patran command language (PCL custom code) in MSC software can be used to evaluate the useful lifespan of MHVs. Similar methodologies can be extended to other medical devices under cyclic loads.

Tearing behavior of membrane coated fabrics based on the DIC method under the effect of initial crack length

2019 ◽  
Vol 61 (1) ◽  
pp. 41-48
Author(s):  
Zhou-Lian Zheng ◽  
Yuan Tian ◽  
Dong Li ◽  
Chang-Jiang Liu
Keyword(s):  
Crack Length ◽  
Initial Crack ◽  
Initial Crack Length ◽  
Coated Fabrics

Predicting the Initial Crack Length in a Solid Propellant

2001 ◽  
Author(s):  
C. T. Liu ◽  
Y. G. Kwon ◽  
T. L. Hendrickson
Keyword(s):  
Crack Length ◽  
Solid Propellant ◽  
Initial Crack ◽  
Initial Crack Length
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