FINITE ELEMENT CALCULATION OF ENERGY RELEASE RATE PRIOR TO CRACK KINKING IN 2-D SOLIDS

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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Energy release rate and crack kinking

International Journal of Solids and Structures ◽

10.1016/0020-7683(81)90050-0 ◽

1981 ◽

Vol 17 (1) ◽

pp. 107-114 ◽

Cited By ~ 43

Author(s):

K. Hayashi ◽

S. Nemat-Nasser

Keyword(s):

Energy Release Rate ◽

Energy Release ◽

Release Rate ◽

Crack Kinking

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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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