scholarly journals An approximate solution of compact test specimen for mode I fracture test by variational approach: Applied to fibrous composite

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 7223-7233
Author(s):  
Yuling Bian ◽  
Baolu Sheng ◽  
Aiping Zhou
Keyword(s):  
Approximate Solution ◽  
Test Specimen ◽  
Fibrous Composite ◽  
Initial Crack ◽  
Standard Test ◽  
Fe Model ◽  
Fracture Test ◽  
Initial Crack Length ◽  
Calculation Results ◽  
Compact Test

The present work presented an approximate solution for a compact test (CT) specimen that was employed as a standard test provided by ASTM E399-19 (2019). The variational method was employed to obtain the solution. The method used a two-step strategy to approximate the displacement response of the CT specimen. The first step was to obtain the general form of displacement solution, and then, the Rayleigh-Ritz approach was employed to modify the solution of the first step. A compliance equation of the CT specimen was obtained, and furthermore, the formula to calculate the stress intensity factor was obtained. The solution was validated by finite element (FE) model and the formula specified in ASTM E399-19 (2019). It was concluded that the calculation results of the proposed solution agreed well with the results of the FE model prediction for the ratio of initial crack length-to-ligament length, which was in the range of 0.25 to 0.35. Furthermore, compared to the results predicted by using the formula addressed in ASTM E399-19 (2019), the method proposed in the present study can achieve closer results than that of the FE model.

Numerical analysis of a new mixed mode I/III fracture test specimen

2015 ◽  
Vol 134 ◽  
pp. 95-110 ◽  
Author(s):  
M.R.M. Aliha ◽  
A. Bahmani ◽  
Sh. Akhondi
Keyword(s):  
Numerical Analysis ◽  
Test Specimen ◽  
Mixed Mode ◽  
Mode I ◽  
Fracture Test

Three-Dimensional Finite Element Analysis of a Mixed Mode I/II Fracture Test Specimen: Asymmetric Four-Point Shear Specimen

2017 ◽  
Author(s):  
Mark Cohen ◽  
Xin Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Test Specimen ◽  
Mixed Mode ◽  
Three Dimensional ◽  
Mode I ◽  
Fracture Test ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, extensive three-dimensional finite element analysis is conducted to study the asymmetric four-point shear (AFPS) specimen: a widely used mixed mode I/II fracture test specimen. Complete solutions of fracture mechanics parameters KI, KII, KIII, T11, and T33 have been obtained for a wide range of a/W and t/W geometry combinations. It is demonstrated that the thickness of the specimen has a significant effect on the variation of fracture parameter values. Their effects on crack tip plastic zone are also investigated. The results presented here will be very useful for the toughness testing of materials under mixed-mode loading conditions.

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.

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