This study investigates the angles θ1, θ2, and θ3 that squat crack faces form with respect to three orthogonal planes: the rail top, the longitudinal-vertical cross-section and the lateral-vertical cross-section. Rail samples with squats of various severities are obtained from the field. Their three-dimensional crack networks are reconstructed using CT (computed tomography) scanning and serial cutting

Accurate evaluation of the thermal shock resistance is great importance when estimating both the life and the performance of piezoelectric structures under thermal shock load. Non-Fourier heat conduction law assumed that the speed of heat propagation in a body is finite, which is more exact to evaluate the thermal shock resistance when the thermal shock time reduces to ps/fs scale or the length size

The aim of this paper is to present a new approach for predicting the mixed-mode fracture resistance of rock-type specimens containing U-shaped notches. The new approach is a modified form of maximum tangential stress (MTS) criterion which states the fracture takes place when the maximum tangential stress at the critical distance from the notch border attains critical value. The critical distance in

The fracture energy constitutes an important input parameter for non-linear finite element analysis of concrete structures. Characterization of such parameter based on standard RILEM three-point bending test or wedge splitting test is known to depend on the size of the specimen. For the assessment example of large hydraulic structures using non-linear finite elements, it is important to develop an

For the mitigation of micro-seismicity during hydraulic stimulation, we introduce the concept of time-delayed pressurization (TDP) which involves arresting the constant-rate process of borehole pressurization for a given delay period, and then resuming it until breakdown occurs. The additional fluid permeation into a porous media by the TDP scheme allows for the manipulation of pore fluid pressure

We performed uniaxial compression tests on sandstone with variable water contents (dry, natural, and fully saturated) and monitored deformation and failure in real-time using acoustic emission (AE) techniques. We propose sandstone damage variables on the basis of accumulative AE energy and dissipated energy theory. The results provide a useful framework for evaluating rock failure and structural design

Unloading can cause many geotechnical disasters, e.g., the rock burst. The underlying mechanism of rock failure is the propagation and coalescence of cracks. To get insight into rock unloading failure, the discretized virtual internal bond (DVIB) model in conjunction with element partition method (EPM) is used to simulate the dynamic fracturing process under unloading conditions. At first, the samples

The micro-structures of rock govern meso- and macro-scale rock behaviours and their failure mechanisms. This paper applied the experimental study (uniaxial and triaxial compressive tests) and scanning electron microscope (SEM) method to illustrate the relationship between microscopic damage and mesoscopic fracture. Specifically, this study carried out that there are three main pre-existing micro-structures

Based on the fracture mechanics concept, effects of specimen geometry on the tensile and compressive strength of magnetite-based heavyweight fly ash-based geopolymer concrete have been investigated both experimentally and analytically. In the experimental program, three mix designs have been prepared containing 0, 50, and 100% magnetite heavyweight aggregate (HWA) and were subjected to the fresh and

The material fracture behavior and associated mechanism is known to be affected by the stress state and strain rate. Using a recently developed rectangular hat-shaped specimen, the fracture behavior of Ti6Al4V was investigated with a stress triaxiality varying from -0.31 to 0.50 at strain rates ranging from quasi-static to 104 /s. The fracture mechanisms of Ti6Al4V under these conditions were studied

Mechanical components produced by the 3D-printing technique contain small voids by nature, which make them susceptible to fracture. Therefore, understanding the fracture behavior of these components improves the applicability of this manufacturing method. In this study, the effect of layer orientation is investigated on the mixed-mode I/II fracture behavior of additively manufactured poly-carbonate

We subjected a commercial dental composite formed by interconnecting polymer-ceramic scaffolds to extensive quasi-static, static and cyclic experiments under biaxial flexure. By this we meant to obtain static and cyclic subcritical crack growth exponents that, based on established relationships describing the degradation of frictional bridging mechanisms, could challenge the fragile notion of an R-curve

Majority of minerals or rocks commonly display a positive Poisson’s ratio between 0.05 and 0.45. However, granites that experience high temperature treatment can exhibit negative Poisson’s ratio under low compressive stresses. The underlying mechanism responsible for the auxetic behavior of thermally-treated granites is poorly understood. Here we present experimental results of uniaxial compression

A coupled crystal plasticity-phase field (CP-PF) model is developed in this paper for analyzing crack nucleation and propagation in polyphase-polycrystalline microstructures of Aluminum 7000 alloys. The model explicitly represents elastic and plastic anisotropies, tension-compression asymmetry, and the crack surface topology in the material. The phase field model incorporates a regularization length-scale

To further understand the mixed-mode I/II fracture behavior of Un-plasticized Polyvinyl Chloride (UPVC), a series of mixed-mode I/II experiments on analogy compact tension specimens have been conducted using an MTS 810 hydraulic test machine. The evolution of the displacement field during stable crack extension was monitored by two-dimensional digital image correlation technique. Results obtained from

Extraction of geothermal energy, oil and gas, and coalbed methane (CBM) are all constrained by the rock’s permeability. To stimulate the production, hydraulic fracturing has become a routine procedure, which is influenced by many factors especially the pre-existing natural fractures. The natural fractures have various characteristics, such as aperture, persistence, and density, which have different

In the present work, the normalization (NM) method was used to obtain J integral resistance (J-R) curves based on clamped single edge notched tension (SENT) specimens. The SENT fracture toughness tests using API X80 pipeline steel were carried out for a series of crack depth to specimen width ratios (a/W) and thickness to specimen width ratios (B/W), corresponding to varying in-plane and out-of-plane

In this communication, the inelastic behavior of a unidirectional graphite/polyimide composite, whose constituent phases are both elastic and brittle, is characterized based on the hypothesis of shear-dominated fiber/matrix interfacial degradation as the primary cause of the observed nonlinearity. To accommodate a combined thermo-mechanical multiaxial loading in the off-axis specimens, the finite-volume

By adopting mathematical and physical covers, the Numerical Manifold Method (NMM) simulates cracks with geometrically elaborate patterns in a unified manner. In this contribution, we propose a high-order NMM together with a direct SIF extraction method for crack modeling. In the proposed framework, SIFs are computed in closed-form upon the solution of the NMM discrete system. This novel formulation

As a newly discovered two-dimensional (2D) material group, MXene has exceptional thermal- electronic properties. However, its mechanical behavior, especially fracture, remains unexplored. In-situ SEM tensile experiments show that the fracture of MXene is quite nonlinear with a much-prolonged softening stage in comparison with other 2D materials, which is suspected to be caused by the anisotropy and

Considering the heterogeneity and strain-rate effects of meso-components, concrete was simulated as a three-phase composite and a 3D meso-scale numerical method was set up. The splitting tensile failure of 315 concrete cubic samples having different side lengths with different aggregate contents and maximum aggregate sizes (MAS) has been explored by using the meso-scale numerical approach. In addition

In this paper, the fracture process zone (FPZ) of dam concrete under different loading rates is measured, and the formation process of FPZ is studied by applying digital image correlation (DIC) and acoustic emission (AE) technique. The results show that the FPZ development of dam concrete presents the characteristics of stepwise growth. The FPZ has emerged before the peak load, and the rapid growth

The Regularized eXtended Finite Element Method (Rx-FEM) is a fracture mechanics based technique for progressive failure simulation when multiple damage events such as matrix cracks and delamination are introduced into the finite element model via mesh independent displacement discontinuities. In the Rx-FEM, the Heaviside step function that is used in the eXtended Finite Element Method (x-FEM) is replaced

The tensile deformation characteristics and the damage evolution of aluminum alloy sheets were investigated with acoustic emission (AE) technology, while microstructural characterization of material damage and surface strain were respectively measured with a morphological assessment method and digital image correlation technique. The Gurson–Tvergaard–Needleman mesoscopic damage model was incorporated

Hydraulic fracturing is the main technology for the development of unconventional resources. The key factor affecting the formation of the fracture network in hydraulic fracturing is the reactive and expansion of natural fractures. The damage-stress-seepage coupling hydraulic fracturing expansion model is established based on the extended finite element method. It quantitatively analyzes the influence

In the present study, weight function (WF) method was used to investigate the propagation pattern of a two-dimensional parallel subsurface crack under a moving contact pressure. Under contact loading, the crack was fully closed and only shear fracture modes led to the propagation. At first, the histories of stress intensity factors (SIFs) were calculated using the available two-dimensional WFs. Then

The effect of penetrating and non-penetrating fluids, and of opening shape, on hydraulic fracturing has been extensively studied, both theoretically and experimentally. These factors are important because of their effect on fracture initiation and breakdown pressure. This paper revisits these problems, but with a novel experimental procedure that allows one to see details of fluid penetration and fracturing

This study investigates experimentally and numerically the resistance to separation between composite skins and different complex geometries of the corrugated core filled with PVC foam. To this purpose, three different geometries including simple foam core without any corrugated composite, longitudinal trapezoid, and square cores are considered and manufactured as waved (corrugated) composite core

During the process of reservoir stimulation, how to create more fractures has become a key issue for the tight sandstone reservoir development. From the experimental investigation and numerical simulation, the effect of pore pressure distribution on fracture propagation was analyzed. The experiment consisted of 300 × 300 × 600 mm3 sandstone specimens was divided into two laboratory tests to investigate

A multiple impact loading test was conducted on notched semi-circular bend (NSCB) marble specimens by using a split Hopkinson pressure bar (SHPB) apparatus. Then, specimens with various dynamic cumulative damages were subjected to dynamic three-point bending loading. During the multiple impact loading test, the dynamic incident energy was kept constant in each impact. The dynamic peak stress and the

Linear Elastic Fracture Mechanics (LEFM) is a widely applied theory to numerically simulate hydraulic fracture initiation and propagation in the subsurface. However, LEFM with the typical fracture toughness measured from unconfined laboratory tests does not apply to hydraulic fracturing applications under subsurface conditions because the fracture toughness is affected by the confining stress and fluid

This paper is devoted to a state-of-the-art review on extended Isogeometric Analysis (XIGA) for computational fracture mechanics. The basic knowledge and formulations of the recently developed XIGA method are discussed in the present work, which includes over one hundred ninety publications that have appeared in the literature. XIGA is a numerical approach that enjoys the benefits of both, extended

The critical Crack Tip Opening Angle (CTOAC) has been proved to be a promising parameter to characterize the crack arrest toughness of natural gas pipeline. However, the accuracy and consistency of its experimental measuring results are seriously affected by the uncertainties in locating the crack tips and the points on both crack surfaces at a certain distance behind the crack tips. Load-displacement

This article applies the finite element over-deterministic (FEOD) method to determine the coefficients of the crack tip asymptotic fields in an anisotropic plane. This method relies on finding the best fit of the crack tip displacement equations to the displacements taken from a large number of nodes around the crack tip. We first revisit the asymptotic solution of crack tip fields in an anisotropic

Mode I opening and mixed-mode I-II fracture experiments were performed with a homogeneous, fine grained sandstone using the three-point bending test. Specimens were notched at various lengths and positions of the beam edge to produce the desired loading condition. A micropolar peridynamic model was used to simulate the fracture initiation and propagation process. The analytical implicit formulation

As a non-contact optical experimental method, caustic method is commonly employed in measuring stress intensity factor at the crack tips of different materials. Caustics theory is commonly used for solving stress intensity factor at crack tips in homogeneous isotropic materials, but it lacks the required accuracy for solving stress intensity factor in interfacial cracks in dissimilar materials. In

Unidirectional tensile tests of PMMA square hole specimens result in mixed mode crack initiation at the square hole corners, highlighted by inclined cracks with respect to the V-notch bisector. Generalized stress intensity factors (GSIF) of the opening and shear modes at a V-notch are derived experimentally in a direct manner from digital image correlation (DIC) displacement and strain fields by means

Focus on the loading sequential effects on the multiaxial fatigue damage accumulation, tests including two series of constant amplitude loadings and 12 groups of two-step loading spectra were conducted on 7075-T651 aluminum alloy. Under the same equivalent stress amplitude, the multiaxial fatigue life raises with the increase of stress amplitude ratio. Fatigue damage accumulation rate is decreased

This paper investigates the fracture resistance of asphalt concretes reinforced with carbon and kenaf fibers. Pure mode I, pure mode II and mixed mode I/II fracture resistance of reinforced asphalt concretes are measured through SCB (semi-circular bend) tests at a low temperature of −15 °C. Three different lengths (i.e., 4 mm, 8 mm and 12 mm) with three different dosages (i.e., 0.1, 0.2 and 0.3% by

Weak bedding planes and joints predominate the anisotropic behaviours of rock mass under external static or dynamic loads. In this article, the rate-dependent fracture performance of a bedding plane-rich rock was experimentally investigated via a split Hopkinson pressure bar (SHPB) system. Based on the dynamic loading of notched semi-circular bending rock specimens at various intersection angles between

Electromechanical resonant de-icing systems provide a low-energy solution against ice accumulation on aircraft. Recent researches show a growing interest towards these systems in the context of more electrical aircraft. Electromechanical de-icing systems consists in electric actuators producing stress within the ice, through micro-vibrations of the surface to be protected, leading to bulk or adhesive

Concrete can be considered as a heterogeneous material at mesoscale comprising of several constituents such as aggregates, mortar and Interfacial Transition Zone (ITZ). Mechanical behavior as well as the durability characteristics of concrete is highly dependent on the mesostructure of concrete and investigating the complex phenomena surrounding concrete at mesoscale considering the heterogeneity presents

In the present study, the self-ability of glass fibers-epoxy smart composites containing different percentage of microcapsules (7, 14 and 21 wt%) was investigated. It is worth noting that the microcapsules’ shell and healing agent were urea formaldehyde and diluted epoxy, respectively. The self-healing composites were destructed by various damage forces through quasi-static penetration method. Therefore

A cohesive zone modeling (CZM) approach is adopted to model crack extensions in as-received and hydrided curved compact tension (CCT) specimens of irradiated Zr-2.5Nb pressure tube materials at room temperature. With the CZM approach, two-dimensional finite element analyses are conducted to model the crack extensions in the CCT specimens. A varying cohesive energy approach is adopted, where the varying

Stress-intensity factor and compliance solutions developed for a single edge notch (SEN) specimen has been validated and verified for tension-compression loading. Fatigue crack growth tests were conducted on the SEN and a surface-crack specimen at stress ratios, R of −1.0 and −2.0 using IN718 forged nickel base superalloy material. (The surface-crack specimen is referred to as the KB-bar specimen in

This work presents an experimental study performed to investigate the influence of the width and size of the specimen on the fracture response of concrete notched beams. Twenty-eight beams with six cross-sections has been tested using a three-point bending (TPB) test setup, which is designed according to the draft of a report developed by Joint ACI/ASCE 446 Technical Committee. Two depths (70 mm and

An improved interfacial bonding model was proposed from potential function point of view to investigate interfacial interactions in polycrystalline materials. It characterizes both attractive and repulsive interfacial interactions and can be applied to model different material interfaces. The path dependence of work-of-separation study indicates that the transformation of separation work is smooth

The focus of this work is to investigate spall fracture in polycrystalline materials under high-speed impact loading by using an atomistic-based interfacial zone model. We illustrate that for polycrystalline materials, increases in the potential energy ratio between grain boundaries and grains could cause a fracture transition from intergranular to transgranular mode. We also found out that the spall

By its nature, metal fatigue has random characteristics, leading to extensive scatter in the results. Both initiation and propagation of a fatigue crack can be seen as random processes. This manuscript develops a numerical analysis using cohesive zone elements allowing the use of one single model in the finite element simulation of the complete fatigue life. The present formulation includes a damage

The goal of this work is to quantitatively examine the effect of adhesive resin cement on the probability of crack initiation from the internal surface of ceramic dental restorations. The possible crack bridging mechanism and residual stress effect of the resin cement on the ceramic surface are examined. Based on the fracture-mechanics-based failure probability model, we predict the failure probability

The fracture toughness of dental nanocomposites fabricated by various methods of mixing, silanization, and loadings of nanoparticles had been characterized using fatigue-precracked compact-tension specimens. The fracture mechanisms near the crack tip were characterized using atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The near-tip fracture

The long-term stability of cemented total hip replacements critically depends on the lasting integrity of the bond between bone and bone cement. Conventionally, the bonding strength of bone-cement is obtained by mechanical tests that tend to produce a large variability between specimens and test methods. In this work, interfacial fracture toughness of synthetic bone-cement interface has been studied