It is known from the split Hopkinson pressure bars experiments on dynamic uniaxial compression of brittle materials such as rocks and concrete that the strength increases with the increase of loading rate and the sample size. Friction and crack propagation do depend upon the loading rate, but this dependence would lead to the opposite effect – the strength decrease with the loading rate. Forrestal

Rock-like materials are heterogeneous and contain numerous defects. Under compression, the widely used two-dimensional wing crack models cannot accurately describe the three-dimensional behaviour of cracks because the three-dimensional secondary crack will wrap (curl) around the disc-shaped primary crack under uniaxial loading. Moreover, experimental results have shown that a single embedded crack

Understanding the hydro-mechanical (HM) coupling grouting process in fractured rock masses is vital for improving grouting effects. In this paper, a hybrid formulation of the unified-pipe network method coupled with zero-thickness interface elements is developed for simulating fracture grouting, named the unified pipe-interface element method (UP-IEM). The UP-IEM can naturally capture both the initiations

We evaluate Weibull’s approach and the coupled criterion (CC) ability to reproduce bending failure stress variations as a function of specimen size in two porous materials, namely gypsum or zinc oxide. Whereas both approaches well reproduce the size effect in gypsum specimens, only the CC succeeds in correctly predicting the failure stress variation for ZnO specimens. We thus question the basis assumption

In this study, a NiCrFeBSi alloy layer with a thickness of about 140 μm was cladded on the AISI4340 steel and then annealed at 700 °C, and the influences of cladding and annealing on tensile and fatigue damage mechanisms of the AISI4340 steel were investigated. The fatigue stress ranges were set from 0 to 0.30–0.75 of the yield strength, and the fatigue deformation and cracking morphologies after different

In this paper, the localized method of fundamental solutions (LMFS), a recently developed meshless collocation method, is applied to the numerical solution of problems with cracks in linear elastic fracture mechanics. The main idea of the LMFS is to divide the entire computational domain into a set of overlapping sub-domains, and in each sub-domain, the classical MFS formulation and the moving least

Looking at wear of incomplete contacts in partial slip we start from an asymptotic description of the contact tractions at the contact edges. We introduce distributed dislocations along the slip zone to account for the profile reduction due to wear and find the long-term time asymptote where the contact is wholly stuck. The resulting stress field is used to find the crack tip stress intensity factors

Fatigue properties of parts built by Additive Manufacturing (AM) are strictly related to process-induced defects and complex surface morphology. Several studies have proved that surface valleys act as crack initiation sites, similarly to surface micro-notches. However, different roughness parameters have been considered in literature for the depth of the surface notches, together with the adoption

The variational principle of safe equilibrium for inhomogeneous elastic cracked bodies is formulated. Using the standard calculus of variations, we show that the crack remains in safe equilibrium as long as the maximum energy reduction rate of the virtually growing crack is negative. The crack starts to grow in the direction of the maximum energy reduction rate when the latter becomes zero. This energetic

A mesh refinement procedure designed for Digital Image Correlation analyses of cracked media is proposed, based on the pixel color for an artificial case, and the crack opening displacement field for two experimental cases. Although evidence that this procedure can improve every case if tiny elements are sought, it is also shown that the size of matrices and consequently, the computational cost can

Previous studies have focused on creep damage evolution behavior of components with one isolated notch, but two or more notches may be placed at the components due to the function requirements, the limitation of the structural size, or may be induced by chemical/physical damage processes. In this work, numerical analyses and creep tests on creep damage and interaction behaviors of neighboring notches

Local crack growth properties within microstructural components are often anisotropic and difficult to measure, especially in materials like titanium alloys, that do not respond well to conventional, stress-ratio-based crack tip marking techniques. A method is described to extract a 3D anisotropic crack growth model from a common triplet colony type in titanium alloys, consisting of three grain-orientation

Matrix microcracking of laminated composites lead to stiffness degradation. Microscopic critical stresses are defined according to the linear elastic fracture mechanics and are found to be independent of the crack density. The microscopic critical stresses are constant as long as the material and the thickness of the cracked plies are constant, and can be used to obtain the semi-analytical expression

Controllable peeling is one of the core requirements of the adhesive applications needing high-precision detachment. In this paper, the peeling of an elastic strip on a viscoelastic substrate is analyzed theoretically focusing on the controllability of the peeling process, especially the interfacial detaching speed. The effects of the speed dependence of the work of adhesion, the substrate viscoelastic

Selective Laser Melting (SLM) is one of the revolutionary additive manufacturing (AM) technologies to produce metallic mechanical parts. To thoroughly understand the damage and fracture behavior of SLM-fabricated Ti6Al4V alloy under complex stress states, a number of tensile, compressive and torsional experiments covering various stress states were conducted with different types of the specimens. A

Using a system composed of a polarized light microscopy and a charge coupled device (CCD), the crack propagation behavior in BaTiO3 (BTO) crystal under electric field was in situ investigated with the field direction parallel or perpendicular to the crack surface. In addition, the growth behavior of Vickers indentation surface cracks under alternating electric field was also in situ investigated. Three

Based on the design relation value of the variation dispersion coefficient β at the notch tip in concrete specimens at the peak load Pmax, a Weibull distribution method was employed to analyze the experimental data for different loading methods (3 PB, 4 PB, WS). The dispersion coefficient β, which complies with the Weibull distribution for notched specimens, leads to a Weibull distribution of the tensile

A vector form conjugated-shear bond-based peridynamic model is proposed to overcome the limitation of the fixed Poisson’s ratio based on the assumption of central force between material points in bond-based peridynamic theory. In the virtue of this proposed approach, the angle variation of a pair of conjugated-shear bonds is derived as a vector in terms of the displacements at three points located

The use of supercritical carbon dioxide (SC-CO2) for the fracturing of coal bodies has excellent development prospects and practicability. It alters the fissure structure of coal bodies and achieves CO2 geological sequestration. This process, which involves the mutual interaction of coal, fissures, supercritical fluid, and gas, can be subdivided into fluid-induced and phase change-induced fracturing

This study develops a numerical method combining the phase-field regularized cohesive zone model (PF-CZM) and random fields for modeling of complicated mesoscopic fracture in quasi-brittle materials. In this method, the material’s fracture properties such as tensile strength and fracture energy are assumed as spatial random variables and represented by Weibull random fields (RFs), which are mapped

In this paper, a novel phase field (PF) model for fracture is developed in the framework of strain gradient elasticity. The strain energy decomposition methods initially proposed for linear elastic fracture problems are extended to the gradient elasticity situation. The PF model is numerically implemented through Abaqus subroutine UEL (user defined element) with nine-node quatrilateral C1-continous

In the present work, the fracture behavior of bioceramic composites for bone tissue reconstruction is evaluated under opening/shearing modes using an approach combining experiments and numerical computations. Different microstructure configurations of the biomaterials are examined in the aim to improve the crack resistance by considering as constituents commercial Alumina (Al2O3), synthesized Tricalcium

To investigate the degradation of the residual fracture energy of concrete suffering from fatigue loading, 150 three-point bending (TPB) beams were first subjected to a fatigue load until the preset number of fatigue cycles was reached, and then the static load was applied to these specimens until failure occurred. Based on the equilibrium relationship between the energy dissipated by the fatigue fracture

The fracture behavior of a cortical bone is significantly affected by its hierarchal structure and a high degree of material anisotropy. Recently, continuum damage models have proven to be an effective tool to characterize such kind of material behavior. However, these models suffer from drawbacks such as mesh dependency, spurious damage growth, and incorrect prediction of damage initiation during

Diffused and localised plasticity in a narrow band between the pre-existing micro-voids are the dominant modes of deformation in a ductile material. In this paper, a yield function is presented for porous metallic materials accounting for these two modes of deformation. The model has been proposed by modifying Madou and Leblond’s model taking into account the effect of shear localisation between the

The aim of this work is to model complex fracture and fatigue processes in microstructural geometries of nodular cast iron. Herein, recently developed generalised phase-field formulation for modelling fracture in brittle and ductile solids subjected to both monotonic and cyclic loading is employed. Three different sized microstructural specimens are analysed using different modelling options to investigate

A new gradient-based formulation for predicting fracture in elastic–plastic solids is presented. Damage is captured by means of a phase field model that considers both the elastic and plastic works as driving forces for fracture. Material deformation is characterised by a mechanism-based strain gradient constitutive model. This non-local plastic-damage formulation is numerically implemented and used

This paper concerns numerical modelling of the deformation process, taking into account the local fracture of porous 316L sinters at the mesoscopic scale using the finite element method. Calculations are performed with the use of geometrical models, to map the realistic shape of the porous mesostructure of the material, obtained by means of computed microtomography. The microtomographic device has

Cylindrical sandstone specimens with same crack lengths and different crack inclinations (β) were subjected to direct tensile testing (DTT) and uniaxial compression testing (UCT) in a laboratory. Meanwhile, the acoustic emission signals, mechanical and acoustic characteristics, numerical simulation results and the failure modes of the specimens were analyzed. The test results showed that the existence

In this work, the fracture prediction method based on two-parameter J-Ad* (J-integral and a new load-independent unified constraint parameter Ad*) with considering both in-plane and out-of-plane constraints has been investigated for semi-elliptical surface cracks in plates under bending. The crack initiation locations and fracture initiation loads for different crack sizes have been comparatively predicted

Understanding the anisotropic fracture mechanism of shale is of significance to assess the development of a stimulated reservoir volume. In this study, three-point bending tests were carried out using notched deep beam specimens of shale with 7 different bedding dip angles to investigate the anisotropic fracture behavior. The anisotropic characteristics of the fracture toughness, energy release rate

The fracture characteristics of layered shale rock determine the efficiency of shale gas production through hydraulic fracturing. An effective and robust numerical method may play a significant role in predicting the crack propagation path in layered shale. In this study, a lower-dimensional interfacial element and tangential derivative variable are developed to describe the evolution of the phase-field

This technical note studies the debonding problem in the Eshelby’s elliptical inclusion with remote stresses. Usually, if one inserts eigenstrains in the inclusion, the normal stress along the interface of matrix and inclusion is negative. In addition, if one increases the remote loading gradually, the normal negative stress along interface will be becoming vanishing. This limit loading for the remote

The problem of an infinite homogeneous isotropic medium with a rigid inclusion and exerting a uniform remote heat flux is deeply studied. The previous solutions without considering the rigid-body displacement of the rigid inclusion relative to the matrix cannot strictly satisfy the boundary condition of displacement and/or the resultant moment constraint around the rigid inclusion. In this paper, the

In this study, the crack lengths in adhesively bonded double cantilever beam (DCB) test specimens have been determined using the digital image correlation technique in combination with an elastic foundation model. This method facilitates the continuous measurement of the crack length and offers significant advantages over conventional visual observation including improved accuracy and the potential

The purposes of the present work are to evaluate the prediction accuracy of characteristic cycle on creep-fatigue life prediction and to analyze the advantages and disadvantages of various models in tensile strain-dwell tests. The parameters of the first cycle, the 10% life, the half-life, and the characteristic cycle that we proposed (a turning point between the initial rapid softening and subsequent

Ceramic balls made of silicon nitride (Si3N4) exhibited excellent mechanical properties are used in high-end components operating at ultra-high speeds, and high and low temperatures. Previously, studies have involved the cyclic mechanical and thermal fatigue tests of ceramic balls under a constant temperature. However, the thermal fatigue characteristics of brittle materials have not been theoretically

Shale has remarkable bedding characteristics, and the key technology of shale gas extraction engineering is garnering great interest in the influence of bedding on the fracture mechanisms and fracture criteria of shale. Three-point bending tests combined with digital image correlation (DIC) were carried out on semicircular bend (SCB) specimens of shale with different bedding angles to investigate the

The acceptance of weld volumetric imperfections such as porosity from the perspective of structural integrity is guided by workmanship criteria. However, there is a lack of knowledge on how and to what extent volumetric imperfections can affect the outcome of fracture toughness tests. The small size of laboratory test specimens potentializes the relative impact of such imperfections. This study numerically

Particle reinforced elastomer matrix composites always show a size-dependently mechanical behavior when the particle size shrinks down to micro- or even nano-scale. A systematic investigation on microscopic mechanisms of such a size effect is carried out in this paper based on tensile and tear experiments of silicone rubber elastomer filled with surface modified silica particles, in which the particle

A split Hopkinson pressure bar system was used to apply a high-speed dynamic load to a flattened Brazilian disc, and the dynamic characteristics of purely type-I or -II fractures or mixed type-I-II composite fractures were studied in detail. The effect of the strain rate and the inclination angle of the prefabricated cracks was analyzed and compared with theoretical results. Furthermore, a dynamic

Osteon orientations play a critical role in defining the orthotropic properties of cortical bone. Cortical bone has different mechanical and materials properties in longitudinal and transverse directions, which are mainly due to the different osteon orientations. This study aims to consider a pre-existing technique with modifications in enrichment techniques for modeling and orthotropic fracture analysis

This paper aims to develop a variable-node multiscale extended finite element method (V-XFEM) for dynamic fracture analysis of the linearly uncoupled and coupled physical phenomena in a compact formula. The general governing equations for the linearly uncoupled and coupled physical phenomena are presented in a compact form. The local mesh refinement technique for modeling cracks is used to improve

The study investigates fatigue growth and shape evolution of a corner crack in a pin-loaded hole by means of three-dimensional FE analyses. The constraint factor/plasticity-induced crack closure strategy was tuned to reproduce experimentally measured crack front shapes. The study quantitatively determines the LEFM acceptability regions using elastic–plastic simulations. It also assesses the sensitivity

Material structures with different loadings can fail in any mode, such as buckling, fracturing, and necking. Determining how to predict the failure properties of different modes is the most important issue in engineering for safety considerations. Well-known methodologies are mainly based on empirical postulations, and deal with different failure modes separately. In the present work, material structures

This paper discusses the effects of mixed mode loading on cohesive zone parameters obtained from load-crack mouth opening displacement (CMOD) curves in asphalt mixtures at intermediate temperature. To this end, a coupled viscoelastic numerical-experimental approach has been used to capture the cohesive strength and fracture energy in the fracture process zone utilizing asymmetric semi-circular bending

In this work, the crack growth of carbon black-filled ethylene propylene diene monomer rubber was analysed by experimental investigations and numerical simulations. The investigated sample is loaded cyclically under displacement-controlled test condition. The sample had a defined initial crack length. Due to the cyclic loading, the crack grows further due to excess critical energy flux. A uniform pattern

Understanding the evolution of microstructure and micro-region properties of weldments during cyclic loading is a challenge for the reliability assessment of high-temperature components. This work is devoted to quantitatively evaluating the variation of micro-region properties and corresponding responsible microstructural features of P92 steel weldments under interrupted fatigue tests and subsequent

Non-proportional multiaxial low-cycle fatigue (MLCF) tests were performed on CP-Ti at different multiaxial strain ratios. The optical microscopy observations and life prediction models verified that the critical plane of CP-Ti was the maximum principal strain plane and that it was effective under non-proportional loading. A non-proportional life coefficient and strain energy density coefficient are

Three-dimensional Finite Element Analyses of pre-cracked small punch test (p-SPT) specimens are performed to evaluate plastic constraint factor (m). The m factor is useful to correlate the J-integral with the crack tip opening displacement (CTOD). The through-thickness square pre-cracked specimen is analyzed for this purpose. Parametric studies are carried out by varying the crack length, the material

A method for calculating the creep damage during low cycle fatigue (LCF) (tensile plasticity reversed by compressive plasticity, PP) controlled by strain rate ε̇ was proposed. According to the equivalent principle of creep damage with the same reduction in cross section, a creep damage model considering a continuously changing stress was established based on the equivalent creep stress σen, which was

During its lifetime, a hydraulic fracture is known to traverse a trajectory in a region of a parametric space of non-dimensional evolutionary parameters. The topology of this diagram depends upon the phenomena considered. For the specific case of a 2D-plane strain fracture propagating in an elastic solid on a straight path normal to the minimum compressive stress, with a constant rate of injection

This paper develops a phase-field approach to model hydro-thermally induced crack propagation in thermo-poroelastic media. Both thermal conduction and convection, and the fully thermo-poroelastic coupled effect are taken into consideration in the phase-field model. The fluid content is influenced by the volumetric strain, temperature, and pressure. The heat flux is susceptible to temperature change

Three-dimensional (3D) phase-field models based on the cell-based smooth finite element method (CS-FEM) are established in this paper. The present model consists of three key ingredients: 1) a phase-field model of fracture in elasto-plastic solids, 2) a staggered scheme for nonlinear interactions between the phase-field equations and those for the elasto-plastic solid mechanics, and 3) its underline

This work aims to experimentally investigate the failure mechanism and the spatiotemporal evolution of permeability in the fissured rock-like specimens under the coupled hydromechanical conditions. The different factors on the coupled hydromechanical loading/unloading failure mechanism are investigated. The experimental results of 3-D internal fracture morphology obtained from the X-ray CT scanning