The recent progress in the development and research of functionally graded materials (FGMs) has prompted the development of numerical methods in engineering analysis for continuously non-homogeneous media. This paper presents the hybrid Meshless Displacement Discontinuity Method (MDDM) for a cracked structure with functionally graded materials. The fundamental solutions of displacement discontinuity

In order to investigate the fracture toughness of granite samples after elevated temperature treatment and liquid nitrogen (LN2) cooling, a series of fracturing tests were performed on semi-circular bend (SCB) specimens containing pure mode-I fracture. The acoustic emission (AE) technique was employed to monitor the damage process during the test. The experimental results indicate that, overall, the

It has been widely accepted that the Brazilian test can be used to obtain the indirect tensile strength of geo-materials. However, the effects of the contact conditions and the heterogeneity of the rock affect the micro-failure of the disc and the accuracy and feasibility of the Brazilian tensile strength (BTS), which typically leads to deviations from the results of the direct test. This study uses

Three-dimensional (3D) constraint effects for part-through cracks, such as corner and surface cracks, emanating from stress concentrators play important role in damage tolerance design of structures, but have hardly been investigated in the frame of 3D elastic-plastic fracture theory. Here the ability of current elastic-plastic solutions to describe 3D constraints and their effects on crack tip fields

Complex, non-planar fracture geometry is often observed in multi-stage hydraulic fracturing. The opening of hydraulic fractures results in a disturbance of local stress, which in turn affects the propagation of the adjacent fractures (stress shadow effect). The interaction between multiple fractures is of major importance in the design of fracturing treatments. In this study, a fully-coupled three-dimensional

The present work studies the Park–Paulino–Roesler (PPR) model, a unified potential-based cohesive zone model (CZM), for mixed mode I/II fractures in different ranked coals, including weakly caking coals, fat coals and anthracite, by using disk-shaped compact tension (DC(T)) tests and punch-through shear (PTS) tests. The PTS experiments showed that with the increase in coal rank, the initial shear stiffness

The translaminar fracture behavior of three composite laminates, based on thermoplastic matrix PEEK reinforced by a woven carbon fibers obtained by consolidation process, has been studied by means of Compact Tension (CT) and Compact Compression (CC) tests. An orthotropic laminate and two quasi-isotropic laminates, have been tested at room temperature (RT) and at 150°C (i.e. for a temperature slightly

In the present work, a numerical investigation based on a modified peridynamic method of fracture properties of epoxy resin reinforced by nanoparticles, more specifically hyperbranched polyester (HBP), was conducted. Due to the specific features of HBP, certain material nodes in the numerical model were constrained to accurately replicate the effect of HBP in pure epoxy resin, and a Monte Carlo method

With the aim of modelling the energy dissipation phenomenon during the initiation and propagation of cracks, a novel cohesive fracture model is proposed in this study based on the multi-scale model of rocks and the Lennard-Jones potential between non-bonding molecules. The proposed model establishes the corresponding relationship of deformation in the multi-scale model of rocks and suggests that the

Impact resistance is one of the more critical and important features of composite materials used in the aerospace industry. The objective of work was to evaluate the hybrid titanium carbon laminate resistance to dynamic loads. The paper utilizes numerous criteria for evaluation of impact behaviour of materials, including force change, energy absorption characteristics and failure identification. To

A theoretical model is established to describe the crack initiation and propagation in AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA). By the Gibbs free energy change, the critical cycle number for crack initiation has been calculated which indicates B2 precipitates in FCC lamellae can delay crack initiation. The dislocation motion from crack tip has been analyzed. The results show that the equilibrium

This article presents a novel deep learning-based damage evaluation approach by using speckled images. A deep convolutional neural network (DCNN) for predicting the stress intensity factor (SIF) at the crack tip is designed. Based on the proposed DCNN, the SIF can be automatically predicted through computational vision. The data bank consisting of a reference speckled image and lots of deformed speckled

Crack propagation is a very important research subject within the field of rock mechanics. In this study, a J-integral based Maximum Circumferential Tensile Stress theory was applied to the conventional Discontinuous Deformation Analysis (DDA) Method for simulating crack propagation. First, according to the relevant theories of fracture mechanics, a crack propagation theory suitable for DDA was derived

This paper evaluates the mechanical properties, modulus of elasticity (E) and critical stress intensity factor (KIC), of self–compacting concrete with the addition of hook-ended steel fibers, implementing Digital Image Correlation (DIC) to obtain the horizontal and vertical displacement fields for beams under four-point bending test. Based on the vertical displacements and the crack mouth opening displacement

This study focuses on a mixed mode crack growth analysis of an aviation gas turbine engine (GTE) compressor disk based on simulation principles. The operation damages occur via inclined surface cracks in a “dovetail type” disk-and-blade attachment. Based on the sizes and configuration of this attachment, three geometries for simulation models of the GTE compressor disk are proposed. The biaxial loading

Since concrete infrastructure may lose its expected physical and functional properties over time, accurate inspection and assessment of such infrastructure systems is necessary to ensure safety and serviceability and prevent unsafe working conditions and the occurrence of hazards. In this paper, an experimental investigation was conducted on several concrete specimens under uniaxial compression to

This paper describes the development of a new inverse analysis approach to derive the fracture mode I parameters of fibre reinforced concrete (FRC) by using the experimental data obtained from three-point notched beam bending tests (3PNBBT) and round panel tests supported on three points (RPT-3PS). The approach is based on a global fitting strategy, in which the numerical response is simulated by means

This paper presents the calculation of complex stress intensity factors (K) for interface cracks in commonly used bi-material specimens subjected to arbitrary ununiform stress fields. First, detailed finite element analyses were carried out for cracks in centre-cracked plate (CCP) and single edge-cracked plate (SECP) bi-material specimens of different material combinations under non-uniform stress

Commonly, fracture toughness tests on deeply cracked specimens are used to assess defects in large-scale components. The paper presents a method for selection of test specimen type, size and crack length in order to obtain fracture toughness estimates relevant to defects in cracked pipes. The method uses available closed-form T-stress, stress intensity factor and limit load solutions to determine the

Crack extensions in uncharged and hydrogen-charged side-grooved A(T) specimens of conventionally forged 21-6-9 austenitic stainless steels are simulated using the cohesive zone modeling approach. Two-dimensional plane strain finite element analyses with fixed cohesive parameters are first conducted to fit the experimental load-displacement curves. Similar analyses using varying cohesive parameters

The engineered cementitious composite (ECC) cracking process involves discontinuities. To solve this difficulty, a semi-discrete model for ECC based on peridynamics (PD) is established. In this paper, the pairwise force function is modified by using an improved damage coefficient. This model is established by modeling the matrix and the interactions between the fiber and matrix. The interactions between

In this work, an experimental-numerical screening method for studying the elastic–plastic properties in high strength steel subjected to environmentally assisted degradation due to hydrogen is proposed. The experiments were performed on single-edge-notch bend specimens loaded with a monotonic constant displacement rate, and the specimens were electrochemically hydrogen pre-charged and/or in-situ. A

The tensile strength of loess is important for the tension-related crack and failure in the Loess regions. While the previous work on the tensile strength of loess mainly focuses on the test method and its variation with different internal and external factors, the micro-mechanical characteristics of the tensile experiments are seldom studied. Taking the unconfined penetrated test (UP test) as example

Dynamic loads applied to metals may lead to brittle or ductile fracture depending on the imposed strain rates, material properties, and specimen geometry. With an increase in the applied velocity, brittle to ductile failure mode transition may also be observed. Furthermore, at high strain rates, ductile fracture may be preceded by shear bands, which are narrow bands of intense plastic deformation,

The ductile fracture behavior of metallic materials is usually coupled with complex stress states. In order to describe the facture behavior of metallic materials under a broad range of stress states, a modified Gurson-Tvergaard-Needleman damage model was proposed by Wei Jiang and has been used to simulate the ductile fracture of 2024-T3 aluminum alloy. However, it was a heavy and trifle job to determine

The addition of Multi-wall carbon nanotubes (MWCNTs) or functionalized-graphene nanoplatelets (f-GNPs) into the epoxy resin create an electrical conductive networks which can be employed for structural health monitoring (SHM) in sensitive adhesive joints. The opening fracture mode (Mode I) loading condition, as one of the important fracture modes in adhesive joints was precisely evaluated in this study

Fracture of martensitic AISI 52100 steel with 12% retained austenite was experimentally studied at temperatures below the tempering temperature by KIc tests and at extremely low loading rates. Depending on temperature, KIc and JC decreased with 6% to 23% for slow rates. It increased with temperature at standard rate but not for slow loading. FE-simulations with elasto-plasticity, phase transformation

Based on the theory of multiple displacement fields, the quasi-static MPM has been extended to simulate crack behavior in this paper. Compared with the existing crack simulation methods, this new method not only avoids the meshing difficulties and complex shape functions but also supports the modeling of crack growth in an arbitrary direction. The key fracture parameters, stress intensity factors,

This research paper explores and highlights the effect of aspect ratio (AR) and specific surface area (SSA) of Graphene Nano-Platelets (GNPs) on the interlaminar fracture behavior of carbon fiber-reinforced polymer (CFRP) composites. Various types of GNPs having different aspect ratios were dispersed in an epoxy system by using the three roll milling technique at a fixed content of 0.5 wt.%. The blends

Fracture processes in quasi-brittle materials are governed by the strain localization phenomenon, which involves the formation of localized damage zones and cohesive cracks. In this work, we present numerical tools to model strain localization from the onset of localized damage to the formation and propagation of multiple intersecting cracks. Two main ingredients are used for this purpose: (i) a microplane

The effects of environment (in air and 3.5 wt% NaCl solution) and artificially-induced surface scratches are investigated on the fatigue properties of railway EA4T (also called 25CrMo4) alloy steel. This steel is found to be markedly sensitive to the chloride-containing environment, with cracking at stresses two thirds of the in-air fatigue limit (+/−326 MPa) under rotating bending (Wöhler) tests.

Scaled experimentation can potentially provide significant benefits such as reduced costs materials and time in testing but is afflicted by the phenomena of scale effects, where the behaviour at scale can be markedly different to that at full size. The design of scaled experiments is presently predominantly founded on the theory of dimensional analysis, which itself is grounded on the invariance of

Bone is a biological composite possessing complex hierarchical structure, which endows it with extraordinary damage tolerance. Despite the progress on the relationship between fracture behavior and the hierarchical structure of bone, contributions of the submicroscale constituents to fracture resistance of bone remain elusive. In this study, the calculations are carried out for fracture in staggered

This article addresses an analysis relating KOP to Kmax,th (FCG threshold) using measured FCG threshold data at various load ratios from R = 0.1 to R = 0.9 under constant amplitude loading. KOP is estimated at near threshold region, due to the low-resolution measurement limit. It is shown that threshold Kmax,th is related to KOP through a critical monotonic plastic strain. Key observation is that this

Shear behaviors of core samples from a deep geothermal exploration well was investigated using direct shear tests. The fracturing process inside the intact rock samples during shear was monitored using acoustic emission (AE) technique. The results show that three shear stages including compaction, quasi-elastic and failure phases can be easily divided based on the shear stress-shear displacement or

It is the singular term dominating the stress field near the vertex of a sharp notch, while the non-singular terms also play a non-ignorable role on the complete stress field. The non-singular stresses near the apex of anti-plane sharp notches are calculated and their roles on the fracture mechanics are analyzed in this paper. By coupling the singular characteristic analysis with the finite element

The adhesives used for the attachment of electronic components to space boards should withstand harsh vibrations of the space launch, which requires their characterization in fatigue. The present study investigates Ablestik 8-2 epoxy adhesive within this context. Novel adhesive test assemblies were devised, which consist of a rigid ceramic component bonded to a resonant flexible epoxy-fibreglass (E-glass)

A comprehensive mesoscopic investigation has been conducted to examine the evolution of the fracture process zone (FPZ), using notched plain concrete beams subjected to three-point bending as a generic representation. The concrete beams are modelled as random heterogeneous materials containing three components, namely coarse aggregates, mortar and the interface transition zone (ITZ). To better represent

Notched three-point-bending (3PB) tests of small concrete samples with a fixed depth/size but various span/depth ratios can be performed in almost every laboratory. Additional usefulness is added to the flexibility of those fixed-depth 3PB tests in this study by providing a simple closed-form solution for determination of the depth and span independent tensile strength ft and fracture toughness KIC

As a regularization method for modeling fracture phenomenon, the phase field method can not accurately capture the location of crack tip. J-integral is an important physical parameter to quantify the stress state of crack tip. In this study, the J-, M- and L-integrals of the fourth-order phase field model for brittle fracture are proposed based on the Noether theorem, and the corresponding infinitesimal

Multiple delamination planes can form when a composite structure is subjected to out-of-plane stresses during static over-loading or impact loading. Numerical modelling of such events is often prohibitively expensive because large numbers of cracks can co-exist and interact, and fracture models usually affect the time step size in explicit solutions. Here a new method called Adaptive Mesh Segmentation

Bedding planes have a strong influence on the mechanical characteristics of layered rocks. To study the effects of bedding plane properties on the strength, fracture and acoustic emission (AE) characteristics of rock, Brazilian tests of sandy mudstone with different angles between the bedding plane inclination and loading direction (the bedding plane-loading angle) were first conducted. Based on the

Analytical solutions are derived for interfacial energy release rate and mode mixity angle in the inverted four-point bending test. In the test, the loads applied in the classical four-point bending test are inverted so that the crack faces come into contact at the midspan and mode mixity with an important mode II component is produced. The contact forces are evaluated by employing a beam model and

Rock mass is often subjected to complicated stress disturbance in many civil and mining engineering. This work aims to investigate the fatigue mechanical characteristics of marble having different interbed orientation subjected to multi-level constant-amplitude (MLCA) cyclic loads. The impacts of interbed structure on rock fracture and energy characteristics were investigated and characterized experimentally

Hydraulic fracturing becomes a key technology for unconventional oil and gas development. As a fracturing fluid, CO2 displays considerable advantages, particularly in shale gas exploitation. However, little research has quantitatively analyzed the effectiveness and efficiency of CO2 fracturing in naturally fractured reservoirs. In this study, a CO2 fracturing model is established in naturally fractured

The additive manufacturing technology can be used to manufacture the complex lattice structures that are difficult to be fabricated by the traditional manufacturing technologies. In order to study the fracture and failure behavior of Ti6Al4V lattice structures manufactured by selective laser melting under compressive load, the cell topologies of face centered cubic with vertical struts (FCCZ) and body

This study aimed to reveal the interface behavior of iron-based shape memory alloy (Fe-SMA) strips bonded to metallic substrates in order to ensure the integrity of such joints. A series of single lap-shear tests was performed on Fe-SMA-to-steel adhesively bonded joints. The test results reveal that the bond strength can reach over 70% of the tensile strength of the Fe-SMA and the cohesive failure

The effects of span-depth ratios on the energy release rate for three-point bending beams were examined. Expressions for the energy release rate for three-point bending specimens with various span-depth ratios were developed using linear interpolation method. The double-G fracture parameters were calculated through tests of three-point bending beams with the same span (800 mm) but various depths (100

Metal additive manufacturing (AM) while offering advantages such as generating parts with intricate geometries, introduces challenges such as intrinsic defects. Since fatigue cracks often start at defects, developing analytical methods to predict fatigue failure is necessary for critical AM applications involving cyclic loadings. In this work a computational framework is presented where a generalized

The Rubber Cord Adhesion Inflation Test (RCAIT) is a recently proposed test protocol to study tyre rubber-steel cord fracture (Kane et al., 2019). As in the traditional blister test, a pressurised fluid is injected between the two adherends to propagate fracture. The fracture energy, Gc, is directly related to the strain energy stored in the inflated rubber. It was shown that evaluation of Gc for RCAIT

This paper details the dynamic materials testing of three advanced ceramics (CoorsTek Engineered Ceramics AD85 and AD995 alumina and a silicon carbide) and a cermet (Luminant TitanMade®) and discusses the observations of damage accumulation in these materials as they were strained to failure. Through the use of a Kolsky bar in conjunction with a Shimadzu HPV-X2 ultra-high-speed camera and Correlated

NiTi wires and thin ribbons are used in shape memory actuators as active elements undergoing repeated thermal cycles. The NiTi actuators operate either under constant force (CF loading constraint) or they act against a variable force (VF loading constraint) from an elastic bias spring. Any stress riser represents a danger for potential actuator failure upon cycling. Although NiTi actuators always include

Early-age fracture tests are conducted on concrete beams with discrete steel, macro polypropylene and blends of macro and micro polypropylene fibers. The fracture behavior with aging of the concrete matrix containing 0.66% volume fraction of fibers is investigated at 1, 3, 7, and 28 days of age. The age-dependent multi-linear cohesive stress crack-separation (σ-w) relationship and the modulus of elasticity

The ductile fracture behavior of a high strength steel is investigated using a micromechanics-based approach with the objective to build a predictive framework for the fracture strain and crack propagation under different loading conditions. Part I of this study describes the experimental results and the determination of the elastoplastic behavior and damage nucleation under different stress triaxiality

In this paper, the fracture mechanics analysis in functionally graded materials and structures (FGMs) is presented. The elemental differential method, is extended to simulate the fracture behaviors of the functionally graded materials, in which the system of equations is established directly based on the equilibrium equations. The first and second order differentiations of the shape functions are utilized

A thermo-chemo-mechanical cohesive zone model (CZM) is proposed to describe the shear behaviour of the interface between cemented paste backfill (CPB) and rock under the coupled effects of temperature and binder hydration. To quantitatively evaluate the thermal effect on the binder hydration, an equivalent thermal age is put forward to express the contribution of temperature to the mechanical properties

The fracture behavior of concrete can be described by an R-curve, which represents the ability of concrete to resist crack propagation. In this study, the R-curve is defined as the envelope of the energy release rates in the critical state and is constructed on the basis of the boundary effect model. Two fracture parameters are introduced for constructing the R-curve, namely, the fracture energy Gf

We present a dynamic adaptive eigenfracture algorithm for the study of crack propagation in brittle materials. The original eigenfracture method is an variational approximation of the Griffith-type fracture with convergence as the element size vanishes. To improve its convergence rate, we extend the eigenfracture approach by using the effective energy release rate as the adaptive refinement criteria

The present paper is devoted to numerical investigation on fracture parameters of cracked shells subjected to out-of-plane loading using ordinary state-based peridynamics (PD). The nonlocal deformation gradient and equivalent domain integral are introduced to evaluate fracture parameters. To reduce the surface effect and obtain more accurate results, the energy method and volume correction algorithm