Effect of Solvent Diffusion on Crack-Tip Fields and Driving Force for Fracture of Hydrogels

2015 ◽  
Vol 82 (8) ◽  
Author(s):  
Nikolaos Bouklas ◽  
Chad M. Landis ◽  
Rui Huang
Keyword(s):  
Boundary Conditions ◽  
Energy Release Rate ◽  
Energy Release ◽  
Crack Growth ◽  
Release Rate ◽  
Crack Tip ◽  
Far Field ◽  
Solvent Diffusion ◽  
Effect Of Solvent ◽  
Transient Energy

Hydrogels are used in a variety of applications ranging from tissue engineering to soft robotics. They often undergo large deformation coupled with solvent diffusion, and structural integrity is important when they are used as structural components. This paper presents a thermodynamically consistent method for calculating the transient energy release rate for crack growth in hydrogels based on a modified path-independent J-integral. The transient energy release rate takes into account the effect of solvent diffusion, separating the energy lost in diffusion from the energy available to drive crack growth. Numerical simulations are performed using a nonlinear transient finite element method for center-cracked hydrogel specimens, subject to remote tension under generalized plane strain conditions. The hydrogel specimen is assumed to be either immersed in a solvent or not immersed by imposing different chemical boundary conditions. Sharp crack and rounded notch models are used for small and large far-field strains, respectively. Comparisons to linear elastic fracture mechanics (LEFM) are presented for the crack-tip fields and crack opening profiles in the instantaneous and equilibrium limits. It is found that the stress singularity at the crack tip depends on both the far-field strain and the local solvent diffusion, and the latter evolves with time and depends on the chemical boundary conditions. The transient energy release rate is predicted as a function of time for the two types of boundary conditions with distinct behaviors due to solvent diffusion. Possible scenarios of delayed fracture are discussed based on evolution of the transient energy release rate.

Mode I Steady Crack-Growth in Superelastic Shape Memory Alloys

2012 ◽  
Author(s):  
Theocharis Baxevanis ◽  
Dimitris Lagoudas ◽  
Chad Landis
Keyword(s):  
Shape Memory Alloys ◽  
Energy Release Rate ◽  
Shape Memory ◽  
Energy Release ◽  
Crack Growth ◽  
Release Rate ◽  
Crack Tip ◽  
Scale Transformation ◽  
Small Scale ◽  
Mode I

A numerical analysis of quasi-static, steady state crack growth in superelastic Shape Memory Alloys (SMAs) under small-scale transformation conditions is carried out for plane strain, mode I loading. Crack growth is assumed to proceed at a critical level of the crack-tip energy release rate. Finite-element results concerning the mechanical fields near the advancing crack tip are presented and the ratio of the far-field applied energy release rate to the crack-tip energy release rate is obtained for a range of thermomechanical parameters. A substantial fracture toughening is observed associated with closure stresses placed on the crack tip by the transformed material left behind in the wake of the advancing crack tip.

On Crack Growth in Composite Cylindrical Shells

1999 ◽  
Author(s):  
Hayder A. Rasheed ◽  
John L. Tassoulas
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Crack Growth ◽  
Release Rate ◽  
Cylindrical Shells ◽  
Applied Pressure ◽  
Fluid Pressure ◽  
Laminated Composite ◽  
Stable Crack Growth ◽  
Composite Cylindrical Shells

Abstract Interfacial defects, in the form of cracks or layer separation, may occur in composite cylindrical shells during the manufacturing process, transportation or service life. Such defects are expected to affect the integrity of laminated composite structural elements and may reduce their capacity to resist the applied loads. In this article, the growth of pre-existing cracks in moderately thick composite cylinders is studied for the case of externally applied fluid pressure. The cracks considered separate thick layers, which are unlikely to buckle locally prior to the final collapse of the structural component. The potential of growth is assessed by computing the energy release rate. It is found that any initial out-of roundness imperfection introduces a shear force at the crack tip by causing the cross section to ovalize slightly. The energy release rate is found to vary exponentially with the applied pressure, when geometric nonlinearities are considered. The analysis is applied to a carbon/glass-fiber hybrid composite tube and the parameters influencing growth are examined. Crack length, through the thickness location, circumferential location relative to the ovalization orientation and the amount of imperfection are found to control the nature of growth. Unstable as well as stable crack growth and arrest cases are observed for various combinations of these parameters.

scholarly journals Crack Growth and Energy Release Rate for an Angled Crack under Mixed Mode Loading

2020 ◽  
Vol 10 (12) ◽  
pp. 4227
Author(s):  
Yali Yang ◽  
Seok Jae Chu ◽  
Wei song Huang ◽  
Hao Chen
Keyword(s):  
Energy Release Rate ◽  
Numerical Method ◽  
Energy Release ◽  
Release Rate ◽  
Mixed Mode ◽  
Crack Tip ◽  
Theoretical Expression ◽  
Propagation Mechanism ◽  
Mode I ◽  
Theoretical Derivation

The evaluation of energy release rate with angle is still a challenging task in metal crack propagation analysis, especially for the mixed Mode I-II-III loading situation. In this paper, the energy release rate associated with stress intensity factors at an arbitrary angle under mixed mode loadings has been investigated using both a numerical method and theoretical derivation. A relatively simple and precise numerical method was established through a series of spatial-inclined ellipses in Mode I-II and ellipsoids in Mode I-II-III, with different propagation angles computed from simulation. Meanwhile, a theoretical expression of the energy release rate with angle for a crack tip under a I-II-III mixed mode crack was deduced based on the propagation mechanism of the crack tip under the influence of a stress field. It is confirmed that the theoretical expression deduced could provide results as accurately as the present numerical method. The present results were confirmed to be effective and accurate by comparison with experimental data and other literature.

On Global Energy Release Rate of a Permeable Crack in a Piezoelectric Ceramic

2003 ◽  
Vol 70 (2) ◽  
pp. 246-252 ◽  
Author(s):  
S. Li
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Crack Growth ◽  
Release Rate ◽  
Piezoelectric Ceramic ◽  
Piezoelectric Materials ◽  
Dielectric Medium ◽  
Crack Model ◽  
Permeable Crack ◽  
Global Energy

A permeable crack model is proposed to analyze crack growth in a piezoelectric ceramic. In this model, a permeable crack is modeled as a vanishing thin, finite dimension, rectangular slit with dielectric medium inside. A first-order approximation solution is derived in terms of the slit height, h0. The main contribution of this paper is that the newly proposed permeable crack model reveals that there exists a realistic leaky mode for electrical field, which allows applied electric field passing through the dielectric medium inside a crack. By taking into account the leaky mode effect, a correct estimation of electrical and mechanical fields in front of a crack tip in a piezoelectric ceramic is obtained. To demonstrate this new finding, a closed-form solution is obtained for a mode III permeable crack under both mechanical as well electrical loads. Both local and global energy release rates are calculated based on the permeable crack solution obtained. It is found that the global energy release rate derived for a permeable crack is in a broad agreement with some known experimental observations. It may be served as a fracture criterion for piezoelectric materials. This contribution reconciles the outstanding discrepancy between experimental observation and theoretical analysis on crack growth problem in piezoelectric materials.

Finite Element Modeling for Energy Release Rate in Human Cortical Bone

Volume 2 ◽  
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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