Coupled Fracture Mechanics‐Geochemical Model of Reaction‐Driven Cracking

Experimental investigation of the effect of dissolution on sandstone permeability, porosity, and reactive surface area

Mechanics of crack initiation, propagation and crack grain boundary interaction in bicrystal silicon using near-tip localized stress calculation

Accurate and efficient numerical integration of weight functions using Gauss-Chebyshev quadrature

SIFs of part-through mode I cracks for uniform crack surface pressure

Experimental dissolution of dolomite by CO2-charged brine at 100 °C and 150 bar: Evolution of porosity, permeability, and reactive surface area

An experimental study of the reactive surface area of the Fontainebleau sandstone as a function of porosity, permeability, and fluid flow rate

Steady-state thermo-elastic field in an infinite medium weakened by a penny-shaped crack: Complete and exact solutions

A procedure has been developed to derive stress intensity factors (SIFs) for part-elliptical cracks based on an approximate crack surface displacement mode assumption for general configurations. The crack surface displacement mode is composed of available 2D crack surface displacement modes at intersections of the crack surface and boundaries, or in symmetry planes. Along with the obtained crack surface displacement mode, SIFs are determined by the magnitude of the crack surface displacement derived from energy release rate for virtual crack increments. The procedure was analytically verified with the exact solution for an embedded crack in an infinite body subjected to uniform crack surface pressure. Several examples show the obtained results in acceptable agreements with available solutions.

A generalised approximate crack surface displacement solution for the two-dimensional part-elliptical mode I crack was developed. This solution includes the surface crack, corner crack and embedded crack, which is subjected to the arbitrary crack surface pressure. The crack surface displacement is derived from stress intensity factor solution and corresponding crack surface pressure distribution. Comparisons of the solution with accurate solutions showed that rather high accuracy has been achieved with the developed solution for various surface, embedded and corner crack problems. This solution can be used to derive three-dimensional weight functions as long as the stress intensity factor and the corresponding crack surface pressure are available for arbitrary mode I problems.

The linear amplitude sweep (LAS) test has been widely accepted for estimating the fatigue resistance of asphalt binders in the last 10 years. This paper proposes a fracture mechanics–based analytical approach for crack initiation and propagation characterization in the LAS test, aiming to more precisely explore the binder crack growth and failure mechanism. Seven unmodified neat asphalt binders and one styrene-butadiene-styrene (SBS) polymer-modified binder are selected in this study. The crack length (a), rate of cracking (da/dN), stress intensity factor (K), and energy release rate (G) are the fundamental parameters for the data interpretation approach proposed in this paper. Experimental and analysis results demonstrate that the energy-based failure definition (either from continuum damage mechanics or fracture mechanics) should be utilized to detect the material-dependent failure occurrence in LAS test. The fracture behavior of asphalt binder in the LAS test follows the two-phase crack growth (TPCG) model in terms of the crack initiation and crack propagation. The crack propagation phase further consists of stable crack growth and unstable crack growth. It is found that the fatigue performance of asphalt binder is intrinsically governed and dominated by its resistance to the crack propagation. The SBS binder in this study clearly displays slower crack propagation behavior than other neat binders. Additionally, the traditional fatigue life can also be divided into the crack initiation life and crack propagation life, which is promising to clarify the specific modification contribution to binder fatigue resistance. The two critical crack lengths of initiated crack and propagated crack for a given asphalt binder are found to be correlated to each other, indicating the potential links between the binder crack initiation and propagation behaviors.

Dynamic propagation behavior of cracks emanating from tunnel edges under impact loads

Analytical and numerical investigations of dynamic crack propagation in brittle rocks under mixed mode loading

Many uncertainties exist in geochemical modeling. Mineral reactive surface area is one of the uncertain parameters. QEMSCAN analyses are performed on sandstone samples from a Dutch CO2 natural analogue to determine reactive surface areas. Geochemical modeling is performed using QEMSCAN surface areas and surface areas which are conventionally used in modeling. The model predicts that the QEMSCAN reactive surface areas result in higher reaction rates and faster equilibration of the sandstones with CO2. The fact that reactions are predicted to occur in a sandstone which has been in contact with CO2 for geological times suggests that the reservoir mineralogy is not yet in equilibrium with CO2. This would indicate that, even if mineral reactive surface areas are determined in detail, geochemical models strongly overestimate reaction kinetics. Other uncertain parameters which can affect kinetics, like mineral nucleation and ion diffusion, should be evaluated in order to be able to better predict long-term CO2-mineral reactions and storage integrity.

Current theories of dynamic fracture are based on elastodynamic analyses of mathematically sharp plane cracks and as such do not explain the observed terminal velocities or the phenomenon of crack branching satisfactorily. The present investigation addresses the above problems by using both microscopic and macroscopic interpretations. The experimental scheme that is used in this investigation is the configuration of a pressure loaded semi-infinite crack in an infinite medium. The loading is achieved through an electromagnetic device which provides highly repeatable loading. The method of caustics is used in conjunction with a high speed camera to obtain the time histories of the crack tip stress intensity factor and the crack position. The problems of crack initiation and crack arrest are explored. The stress intensity factor at initiation is found to be independent of the rate of applied loading when the latter is below about 104MPA/sec, but the initiation stress intensity factor increases considerably when the loading rate is increased further. Crack arrest is obtained in large specimen by using very low energy loading pulses. It was found that the stress intensity factor at crack arrest was constant and also that, within the time resolution of the high speed camera (5 μsec), the crack comes to a stop abruptly. The crack propagation and branching aspects were investigated first using post-mortem analysis of the fracture surfaces and high speed photomicrography to get an idea of the microscopic processes that occur in the fracure process. From this investigation, it was found that crack propagation involving high stress intensity factor and high velocity situations takes place by the growth and interaction of microcracks, due to the voids present in the material. A surprising result of this investigation was that cracks propagated at a constant velocity, although the stress intensity factor varied. Current theories of dynamic fracture cannot explain such behaviour. The crack branching process was found to be a continuous process arising out of propagation along a straight line. High speed photomicrographs of the branching process indicated the presence of a number of part-through attempted branches that interact with one another and finally the successful emergence of a few full fledged branches. The microscopic observations on the crack propagation and branching process leads to a new interpretation of dynamic fracture that attempts to qualitatively explain the constancy of the velocity of propagation, the terminal velocity and crack branching. The crack branching mechanism is a logical continuation of the mechanism for crack propagation.

This study presents an analytical analysis on the propagation of a semi-infinite crack in a pre-stressed functionally graded orthotropic strip (FGOS) impacted by the propagation of horizontally polarized shear waves. The Wiener–Hopf technique and two-sided Fourier integral transforms have been employed in the solution treatment of the model to achieve the closed-form expression of the stress intensity factor (SIF) for the force of constant intensity (CF). The effect of crack speed, crack length, horizontal compressive pre-stress/horizontal tensile pre-stress, vertical compressive pre-stress/vertical tensile pre-stress, functional gradient parameter, and anisotropy parameter on the SIF in a pre-stressed FGOS has been unraveled through numerical computation and graphical demonstration. Furthermore, some special cases have been deduced from the derived expression of the SIF for CF. The comparative analysis has been made for the SIF in the considered strip with distinct configuration. Moreover, for the sake of validation, the obtained results for CF with constant load have been matched with the pre-established results as a special case of the problem.