scholarly journals Effect of Initial Crack Length of C(T) Specimen on Crack Propagation Measurement by Dc Potential Drop Method

2018 ◽  
Vol 408 ◽  
pp. 012011
Author(s):  
Ni Chenqiang ◽  
Xue He ◽  
Wang Weibing
Keyword(s):  
Crack Propagation ◽  
Crack Length ◽  
Potential Drop ◽  
Initial Crack ◽  
Initial Crack Length ◽  
Drop Method ◽  
Dc Potential ◽  
Propagation Measurement

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.

scholarly journals Crack Detection and Crack Length Measurement with the DC Potential Drop Method–Possibilities, Challenges and New Developments

2020 ◽  
Vol 10 (23) ◽  
pp. 8559
Author(s):  
Jürgen Bär
Keyword(s):  
Crack Length ◽  
Crack Detection ◽  
Potential Drop ◽  
General Information ◽  
Ambient Atmosphere ◽  
New Developments ◽  
Drop Method ◽  
Notched Specimens ◽  
Dc Potential ◽  
Crack Length Measurement

The direct current potential drop method (DCPDM) is widely used to determine the crack length in fatigue experiments. In practice, some special features of this method must be considered. Aside from general information on the experimental setup and calibration, some special features of the method, such as the influence of the ambient atmosphere and the application of the method to ferromagnetic materials, are presented and discussed. In addition, with the multiple potential drop measurement, a method is presented which improves the resolution of the DCPDM for detection of cracks and allows to determine crack initiation sites. The capabilities provided by this method are demonstrated on the basis of measurements undertaken on notched round bars and single edged notched specimens.

An Efficient Numerical Scheme for Sizing of Cavity Defect in Metallic Foam From Signals of DC Potential Drop Method

2014 ◽  
Vol 50 (2) ◽  
pp. 125-128 ◽  
Author(s):  
Xiaojuan Wang ◽  
Shejuan Xie ◽  
Zhenmao Chen
Keyword(s):  
Numerical Scheme ◽  
Potential Drop ◽  
Metallic Foam ◽  
Drop Method ◽  
Dc Potential

NDT of Cavity Defect in Metallic Plate Using dc Potential Drop Method

2018 ◽  
Vol 46 (2) ◽  
pp. 20170092
Author(s):  
Xiaojuan Wang ◽  
Wenlu Cai ◽  
Zhenmao Chen
Keyword(s):  
Potential Drop ◽  
Metallic Plate ◽  
Drop Method ◽  
Dc Potential

DC potential drop method for evaluating material degradation

2004 ◽  
Vol 18 (8) ◽  
pp. 1368-1374 ◽  
Author(s):  
Chang-Sung Seok ◽  
Bong Kook Bae ◽  
Jae-Mean Koo
Keyword(s):  
Potential Drop ◽  
Material Degradation ◽  
Drop Method ◽  
Dc Potential

scholarly journals Effects of Initial Crack Length and Specimen Thickness on Fracture Toughness of Compact Bone.

1999 ◽  
Vol 42 (3) ◽  
pp. 532-538 ◽  
Author(s):  
Yuji TANABE ◽  
William BONFIELD
Keyword(s):  
Fracture Toughness ◽  
Crack Length ◽  
Compact Bone ◽  
Initial Crack ◽  
Specimen Thickness ◽  
Initial Crack Length

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
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