Finite element calculation of energy release rate for single-fibre pull-out test

The energy release rate for propagation of a debond in a single-fibre pull out test was derived analytically. The key finding was that an accurate analysis can be derived by a global energy analysis that includes effects of residual stresses and interfacial friction but does not need to include the details of the stress state at the interfacial crack tip. By comparison to finite elements analysis, it was verified that the analytical results are very accurate provided the debond tip is not too close to either end of the specimen. By casting the results in terms of net-specimen stress, it was possible to derive a general energy release rate result that applies to both the pull-out test and the related microbond test. The energy release rate expressions can be used to determine interfacial fracture toughness from single-fibre pull-out tests or microbond tests.

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Calculating Energy Release Rate as a Function of Crack Length Using a Multiple-Step Crack Closure Technique in Tire Finite Element Models

Tire Science and Technology ◽

10.2346/tire.18.460302 ◽

2018 ◽

Vol 46 (3) ◽

pp. 130-152

Author(s):

Dennis S. Kelliher

Keyword(s):

Finite Element ◽

Energy Release Rate ◽

Crack Length ◽

Energy Release ◽

Crack Closure ◽

Release Rate ◽

Fatigue Behavior ◽

Three Dimensions ◽

Quantitative Prediction ◽

Closure Technique

ABSTRACT When performing predictive durability analyses on tires using finite element methods, it is generally recognized that energy release rate (ERR) is the best measure by which to characterize the fatigue behavior of rubber. By addressing actual cracks in a simulation geometry, ERR provides a more appropriate durability criterion than the strain energy density (SED) of geometries without cracks. If determined as a function of crack length and loading history, and augmented with material crack growth properties, ERR allows for a quantitative prediction of fatigue life. Complications arise, however, from extra steps required to implement the calculation of ERR within the analysis process. This article presents an overview and some details of a method to perform such analyses. The method involves a preprocessing step that automates the creation of a ribbon crack within an axisymmetric-geometry finite element model at a predetermined location. After inflating and expanding to three dimensions to fully load the tire against a surface, full ribbon sections of the crack are then incrementally closed through multiple solution steps, finally achieving complete closure. A postprocessing step is developed to determine ERR as a function of crack length from this enforced crack closure technique. This includes an innovative approach to calculating ERR as the crack length approaches zero.

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Study of Strain-Hardening Behaviour of Fibre-Reinforced Alkali-Activated Fly Ash Cement

Materials ◽

10.3390/ma12234015 ◽

2019 ◽

Vol 12 (23) ◽

pp. 4015

Author(s):

Hyuk Lee ◽

Vanissorn Vimonsatit ◽

Priyan Mendis ◽

Ayman Nassif

Keyword(s):

Fly Ash ◽

Energy Release Rate ◽

Strain Hardening ◽

Energy Release ◽

Release Rate ◽

Critical Energy ◽

Critical Energy Release Rate ◽

Pull Out ◽

Alkali Activated ◽

Alkali Activated Cement

This paper presents a study of parameters affecting the fibre pull out capacity and strain-hardening behaviour of fibre-reinforced alkali-activated cement composite (AAC). Fly ash is a common aluminosilicate source in AAC and was used in this study to create fly ash based AAC. Based on a numerical study using Taguchi’s design of experiment (DOE) approach, the effect of parameters on the fibre pull out capacity was identified. The fibre pull out force between the AAC matrix and the fibre depends greatly on the fibre diameter and embedded length. The fibre pull out test was conducted on alkali-activated cement with a capacity in a range of 0.8 to 1.0 MPa. The strain-hardening behaviour of alkali-activated cement was determined based on its compressive and flexural strengths. While achieving the strain-hardening behaviour of the AAC composite, the compressive strength decreases, and fine materials in the composite contribute to decreasing in the flexural strength and strain capacity. The composite critical energy release rate in AAC matrix was determined to be approximately 0.01 kJ/m 2 based on a nanoindentation approach. The results of the flexural performance indicate that the critical energy release rate of alkali-activated cement matrix should be less than 0.01 kJ/m 2 to achieve the strain-hardening behaviour.

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Finite Element Modeling for Energy Release Rate in Human Cortical Bone

Volume 2 ◽

10.1115/esda2004-58307 ◽

2004 ◽

Author(s):

Saiphon Charoenphan ◽

Apiwon Polchai

Keyword(s):

Finite Element ◽

Crack Propagation ◽

Finite Element Modeling ◽

Energy Release Rate ◽

Cortical Bone ◽

Energy Release ◽

Crack Growth ◽

Release Rate ◽

Slow Crack Growth ◽

Finite Element Models

The energy release rates in human cortical bone are investigated using a hybrid method of experimental and finite element modeling techniques. An explicit finite element analysis was implemented with an energy release rate calculation for evaluating this important fracture property of bones. Comparison of the critical value of the energy release rate, Gc, shows good agreement between the finite element models and analytical solutions. The Gc was found to be approximately 820–1150 J/m2 depending upon the samples. Specimen thickness appears to have little effect on the plane strain condition and pure mode I assumption. Therefore the energy release rate can be regarded as a material constant and geometry independent and can be determined with thinner specimens. In addition, the R curve resulting from the finite element models during slow crack growth shows slight ductility of the bone specimen that indicates an ability to resist crack propagation. Oscillations were found at the onset of the crack growth due to the nodal releasing application in the models. In this study light mass-proportional damping was used to suppress the noises. Although this techniques was found to be efficient for this slow crack growth simulation, other methods to continuously release nodes during the crack growth would be recommended for rapid crack propagation.

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