To investigate the influence of bedding planes on its fracture characteristics under dynamic loading, testing and numerical simulations are carried out on semi-circular bend specimens of coal. It is shown that the fracture load and dynamic initiation fracture toughness decrease as the increase of bedding-plane angle. The crack propagation direction is jointly controlled by the maximum principal stress

In this study, a systematic three-dimensional finite element analyses (3D FEA) are performed to evaluate the Mode II stress intensity factor (SIF) for circumferential through-wall cracked pipe under torsion moment. A wide range of crack lengths and pipe radius over thickness ratios are considered. Empirical solution of the mid-thickness Mode II SIF is developed as functions of crack lengths and pipe

Acoustic emission (AE) and digital image correlation were used to monitor mode I fracture in center notch and smooth boundary specimens. The AE source was characterized as a microcrack and represented by the moment tensor, which was obtained by minimizing the error between displacements calculated from an elastodynamic solution and those measured, subjected to the constraint of a microcrack source

It is well known that the grain size has significant influence on the fracture of quasi-brittle materials. In order to give a quantitative description of this influence, many researchers have tried to find empirical relationships between the critical distance and the grain size, connecting a macroscopic parameter with the material microstructures. In this paper, a more rational model of this relationship

Alkali silica reaction (ASR) is one of the mechanisms that can reduce the durability of concrete. ASR causes concrete to swell, thereby creating internal stresses, which result in micro-cracking. This study investigated the impact of using rapid setting cationic bitumen emulsion (CRS) as an additive in roller-compacted concrete (RCC) on the progress of Alkali silica reaction (ASR). For this purpose

Hard rock breaking is a great challenge for deep drilling and mining engineering, and the microwave-assisted rock breaking technique offers a promising solution. However, the lack of knowledge of the effects of microwave irradiation on hard rocks limits the further development of this technology. Laboratory tests have been conducted to investigate the variations of fracture properties of granite subjected

The municipal water distribution systems across the world include a significant amount of cast-iron pipes. Many of the buried cast-iron pipes are over fifty years old and require rehabilitation. Municipalities decide on a rehabilitation solution between the replacement and re-use of the existing pipes based on the remaining strengths of the pipes. Fracture mechanics has appeared as the most viable

High total strain-controlled creep-fatigue tests of 1.8% were performed for a directionally-solidified Ni-based superalloy, DZ445, at 900 °C in air. Dwell times of 0, 2, and 5 min. were introduced at the tensile peak strain for each cycle. Experimental results show a decrease in fatigue life with increasing dwell time. The significant cyclic softening is observed after the application of the dwell

Strain energy release rate (SERR) along a linear crack front of a multidirectional composite DCB specimen shows an obviously non-uniform distribution, which causes the fracture toughness GIavg measured by experiments smaller than the real GIC, and so leading to a lower estimation of fracture toughness. In this study, based on the numerical model a novel semi-empirical closed-form formula was proposed

The two-dimensional (2D) delamination growth in fiber-reinforced polymer (FRP) laminates with in-plane isotropy under Mode I loading condition was numerically investigated using finite element analyses. Two sizes of plate models were developed, focusing on different fracture stages. Cohesive elements were employed to simulate the fracture behavior in the presence of large-scale bridging (LSB). The

Gradient distributions of material properties are taken into account in phase-field model of fracture and the adaptive consistent element-free Galerkin method (EFG) for the fracture analysis of functionally graded materials (FGMs) is presented. Considering the fact that both the moving least-square approximation and the consistent integration scheme contribute to producing the accurate stress fields

The simulation and assessment of fatigue damage of metallic materials are strongly dependent on the definition of critical damage initiation, i.e. the formation of a crack after a certain number of cycles under fatigue loading. To get this described in an appropriate way classical fatigue analysis needs to be combined with fracture mechanics to obtain a realistic size of an initiating macro crack in

The objective of this article is to simulate crack growth of complex Mindlin–Reissner plates by developing an adaptive multi-patch extended isogeometric analysis (XIGA). Nitsche’s method is used to treat continuity between multi-patches or the coupling of non-conforming meshes, exactly describing the geometry of complex plates. The computational meshes in XIGA are independent of the cracks by introducing

Porous amorphous silica (a-SiO2) is of both fundamental and practical interests, as they exhibit a large specific surface area and tunable porous network. However, the brittle nature of a-SiO2 and the presence of pre-existing cracks at both micro- and nano-scales lead to complex mechanical behavior. In this study, we systematically investigate the effects of pre-existing crack and its orientation on

Taking into consideration the mechanics of 2D materials concerning their intrinsic defects, especially at high temperatures, it is important to develop strong structures for extreme working conditions. Molecular dynamics simulations were used in this article to understand the mechanics of mono- and polycrystalline (PC) silicon-germanium nano-sheets (MSiGeNSs and PSiGeNSs) as a function of temperature

In this study, virtual crack closure technique (VCCT) and extended finite element method (XFEM) are coupled to each other as XFEM-VCCT approach to simulate mode I fatigue delamination growth in composites, employing the direct cyclic method in Abaqus. Both two-dimensional plane strain and three-dimensional finite element models under force and displacement control are considered. Numerical simulation

Microwave assisted mechanical rock breaking is a hybrid rock breaking method that combines microwave heating and mechanical rock breaking technologies and is proven to have potential applications in mineral processing, mining, and geotechnical engineering. It is, thus, important to understand the effect of microwave-induced damage on rock fracture characteristics. In this study, granite specimens of

In this paper, the influence of the stress triaxiality on the failure strain of short fiber-reinforced composite, manufactured by the injection molding process, is investigated by tensile tests on notched ASTM-D638 specimen and ASTM E1820-01 U-Shape specimens made of a polyamide-6 thermoplastic polymer reinforced with 20% of short carbon fibers (PA6-20CF). From the combined experimental and FEA investigations

The single lap shear test is widely used to measure the strength of dissimilar welds even though such a test brings limited understanding of the intrinsic weld toughness. The present study proposes a numerical finite element (FE) analysis and experimental characterization of dissimilar joints presenting various microstructures (thickness of the intermetallic layer (IML) and hardness profile). For this

In order to investigate the size effect and reason of rock fracture toughness, the split loading test was carried out in the GCTS rock mechanics testing machine using the center-cracked circular disc (CCCD) samples with diameters of 50 mm, 100 mm, 150 mm and 205 mm, respectively. The lengths of fracture process zone (lFPZ) were determined by the maximum normal stress criterion. The size effect of the

Inertial force effects complicate the determination of the mode I interlaminar fracture toughness under high loading rates in composites. Although using a quasi-static analysis is a common approach, it is not always valid. A time-based threshold criterion is proposed to determine when dynamic effects might be neglected during the analysis of a high loading rate Double Cantilever Beam test. The criterion

A prior study [1] benchmarks a relatively new axisymmetric Flat Bottom Hole (FBH) specimen concept for use in crack growth threshold testing, with reduced crack initiation loads achieved by applying by an electrical pulse around the notch tip prior to testing. In this study, an improved electrothermal pulsing technology is used with higher current capability, and more precisely timed pulses. Electrical

In this work a physical mechanism-based phase-field model for adiabatic shear bands (ASBs) in collapsing thick-walled cylinders (TWCs) is addressed within the framework of the unified phase-field theory for damage and fracture (Wu, 2017; Wu and Nguyen 2018). Owing to the properly constructed energetic degradation function and crack geometric function, this model is capable of characterizing the three-stage

In this study, we explored the effects of different softening laws on the modelling of progressive damage in unidirectional composites materials using a 2D lattice model. The lattice model was based on axial springs that accounted for nearest-neighbour interactions. We considered linear and exponential softening laws and assessed their influence on the dynamic fracture response of unidirectional composite

The fracture strength of photovoltaic silicon wafers is affected by factors such as slicing process parameters and saw wire parameters. This paper numerically simulates the process of diamond wire sawing silicon crystals combined with the linear elastic fracture mechanics. A mathematical analysis model has been established to calculate the fracture strength of diamond wire cut silicon wafers in the

The diverse mechanical properties and geometric configurations of the projectiles usually cause challenges to the accurate damage prediction of the carbon fiber reinforced plastic (CFRP) laminates. In this study, the mass and dimension of rigid projectiles are considered to explore their influence on the damage behaviors of CFRP, including dynamic deformation, fracture pattern, failure, etc. Experiments

The damage and fracture mechanisms of concrete are complicated due to the material’s inherent meso-scale heterogeneities. In this study, continuous random fields for selected properties, such as the tensile strength, are first generated on the basis of real microscale X-ray Computed Tomography (CT) images of concrete, using statistical reconstruction algorithms and the Karhunen-Loève expansion technique

Using the Stroh sextic formalism, we derive the elastic field describing stresses and displacements for a blunt crack in a generally anisotropic elastic material subjected to two-dimensional deformations. The blunt crack is represented by a parabolic cavity. We find that the elastic field is exact everywhere in an anisotropic elastic material with a parabolic boundary and is not confined to the near-tip

Plastic dissipation accompanies fatigue crack growth in ductile materials. Previous studies presented a relation between plastic dissipation (dW/dN) and the fatigue crack growth rate (da/dN), where some researchers assumed a linear relation between both to enable crack growth predictions. To study the validity of this assumption, this paper reports an experimental study on fatigue crack growth in 7075-T6

In this paper, the asymptotic behaviour of the stress intensity factor (SIF) near a corner of a crack is discussed. The weight function of Oore-Burns and FE analysis are used in order to explain the trend of the SIF. The analytical analysis shows that the SIF at the corner has a cusp behaviour as a function of the distance from the corner. This is a crucial mathematical property obtained from the Oore-Burns

This study benchmarks a relatively new axisymmetric specimen concept for use in threshold testing, where the crack initiates and grows from the corner of a flat-bottomed circular hole in a cylindrical specimen while the bottom of the hole is cyclically loaded with a flat-ended plunger. The Flat-Bottom Hole (FBH) specimen is configured so the stress intensity naturally decreases as the crack grows radially

The replacement of water by supercritical carbon dioxide in coal and rock mass fracturing has shown excellent development prospects. However, large-scale industrial implementation of supercritical carbon dioxide fracturing (SCDF) requires an accurate estimation of crack initiation pressure, while laboratory test methods are time-consuming and involve too complicated testing and sample preparation procedures

A critical overview of past research on the interaction integral (I-integral) method is presented. The I-integral is the two-state mutual energy release rate decided by a designable auxiliary field and the actual field. Due to the designability of the auxiliary field, the I-integral has been used extensively in extracting the individual stress intensity factors (SIFs) and the T-stress of a crack in

The current analyses present results of running ductile fracture propagation in high strength X100 line pipe steels under the influence of anisotropy. Mechanical anisotropy is commonly available in pipe products as a result of the manufacturing process, especially, those subjected to hot/cold-worked deformation. The outcomes of the present analyses show that its effect on the behavior of running ductile

Fatigue crack initiation can be regarded as a generalized phase transformation from the view of breaking energy barrier. A new phase transformation model is proposed to predict fatigue crack initiation based on the second law of thermodynamics. Evolution of dynamic energy during crack initiation and the damage under fatigue loading is considered combining with the entropy theory. The system becomes

In this paper, 316H creep crack growth data at 550 °C are analysed to investigate the effect of in-plane constraint on creep crack initiation times. A constraint parameter is proposed to quantify the difference between an actual opening stress and the Riedel-Rice opening stress field in plane strain, using experimentally measured C*. Test data analysis shows that creep crack initiation times can be

Fracture mechanism of hydraulic fracturing for anisotropic shale is of very importance in shale gas mining technology. The classical fracture criteria can better predict tensile (Mode I) fracture under arbitrary loading condition (pure tensile, pure shear and mixed-mode), but have difficultly in predicting shear (Mode II) fracture. In this paper, a new mixed-mode fracture criterion (modified K-ratio

This paper presents a DEM experiment for developing a rock joint constitutive model that is able to consider lab-scale geometrical parameters of waviness and unevenness. We carried out a systematic parametric study using DEM framework to investigate the influence of asperity area and asperity angle on the peak shear strength and peak dilation angle. Based on the insights obtained from numerical outputs

During the past couple of decades, modern fracture criteria have been developed based on a crack-tip material length scale so-called the critical distance, where the critical energy/stress/strain parameter required for the crack propagation is measured. However, in most cases, the critical distance has been considered as a material parameter measured under pure mode I crack tip displacements and independent

Fatigue crack growth thresholds for ferritic steels and aluminum alloys in flaw evaluation documents are reviewed. The WRC (Welding Research Council) Bulletin, ASME (American Society of Mechanical Engineers) Code Section VIII, IIW (International Institute of Welding) and BS (British Standards) 7910 give constant fatigue crack growth threshold values at negative stress ratios. However, the definitions

Hydraulic fracturing is a necessary production enhancement procedure for low permeable conglomerate reservoirs. To study the hydraulic fracture (HF) propagation mechanism in strong heterogeneous conglomerate reservoirs, a numerical simulation based on the modified global cohesive zone method (CZM) was proposed. Two types of geological conglomerate models were built, and natural fractures were also

The damage evolution and plastic flow are usually coupled for rocks due to heterogeneity, which is significant for the design and construction of underground structures. In this paper, a novel damage model considering the plastic strain is proposed for rocks. The novelty of the model lies in the damage evolution associated with the plastic flow, which incorporates double variables (damage and plastic

In this paper, the evolution of microstructure and the role of twin boundary during the fracture process of nano-twinned Ag are studied through molecular dynamics simulation. The fracture process of nano-twinned Ag with multiple twin boundaries is compared with both the fracture process of single crystal Ag and nano-twinned Ag with single twin boundary. Results demonstrate that multiple twin boundaries

This paper aims to investigate the effect of thermal shock on hydraulic fracturing in hot dry rock (HDR). To simulate the thermal shock effect caused during the injection of cold water, several natural granite specimens were slowly heated to various target temperatures and then rapidly cooled down by flowing water. Laboratory hydraulic fracturing experiments were performed on granite specimens under

Fracture criterion of local symmetry has been widely used to predict the fracture kink and simulate the fracture trajectory in rocks under the mixed-mode loading. Under small scale yielding, it must include two aspects: the local mode I stress intensity factor (SIF) kI is maximum and the local mode II SIF kII is zero. When fracture just initiates, the local kII is not zero, but it will be gradually

In this study, the mechanisms of top-down crack (TDC) propagation were investigated based on viscoelastic finite element (FE) analyses. By computing J-integral through 3D FE viscoelastic analyses, TDC propagation mechanisms were examined in pavement structures with cement-treated base (CTB) and granular base (GB) and different asphalt concrete (AC) layer thicknesses. The results showed that applying

The Voronoi cell finite element model (VCFEM) containing three phases of inclusion, interphase and matrix in an element has been proven to be very accurate and efficient in the analysis of inclusion reinforced composites. In this paper, we extended our previous study to include the matrix-interphase interface debonding problems. The traction-free at the debonded matrix-interphase interface and the

A computational method for multi-material corners that enables accurate estimations of generalized stress intensity factors with relatively coarse and uniform discretizations is described in this paper. Specifically, explicitly modeled geometries of material junctions, crack tips and debonded interfaces are isoparametrically and hierarchically enriched to construct approximations with the known local

The ductile fracture behavior of a high strength steel is addressed in this two-part study using a micromechanics-based approach. The objective of Part II is to propose, identify, and validate a numerical model of ductile fracture based on the Gurson–Tvergaard–Needleman model. This model is enhanced by the Nahshon–Hutchinson shear modification in combination with a generalization of the Thomason coalescence

The dynamic interfacial crack propagation and crack kinking phenomena in sandwich panels are studied. The paper derives an analytical approach based on the Extended High-Order Sandwich Panel Theory (EHSAPT) and a cohesive interface modeling. The mathematical modeling of the panel makes a distinction between the face sheets and the core. The core is further divided into two bodies aiming to allow the

The fatigue assessment methods considering surface strengthening process were proposed through experimental investigation of fatigue properties of carburized Cr-Ni alloy under stress ratios of 0 and 0.3. Interior-failure is caused by continuous debondings of refined grains due to stress concentration around interior-inclusion, while surface-failure is caused by grain dislocation slip around surface-inclusion

Innovations of advanced materials have been at the core of most engineering technologies, devices and systems. Composite laminates in particular have been extensively employed in many major and advanced industries including aircraft, maritime transport, and automobiles. Failure in composite structures is critical and often complicated, and that is the consequence of the evolution of and interactions

The aim of this study was to develop a numerical model for the process of non-uniform corrosion under realistic temperature-relative humidity variations. Non-uniform distribution of corrosion products and their expansion around the steel bar were modeled in 2D. Cohesive elements embedded in the finite element mesh were used to model concrete cracking under corrosion. The proposed model was used to

New methods for implementing cohesive zones in computational mechanics were derived by re-interpreting cohesive-zone “traction laws” as “strength models” and using concepts from damage mechanics. When applied to pure mode I or mode II loading, this approach is identical to prior methods. But, when applied to mixed-mode loading, it defines a new approach called strength cohesive zone modeling (or “strength

Particle-based model (PBM) has been extensively used to investigate progressive failure process of rock due to its advantage in modeling fracture development. In order to make the PBM reproduce rock failure behavior more realistically, this study develops an advanced clumped particle model for rock based on 3D Voronoi tessellation (VCPM). In the newly developed model, irregular clumps are identified

The transition zone was defined as an interface with certain thickness, strong heterogeneity and anisotropy in the vertical profile for layered formations, which had great effect on hydraulic fracture (HF) height propagation. In this paper, a numerical model for transversely isotropic layered shale with transition zone was established by utilizing the extended finite element method (XFEM) based on

Maglev trains with an operation speed higher than 600 km/h show a great advantage during the next generation ground transportation. To tackle the structural integrity of maglev bogies made of forged 6082-T6 aluminum alloys, a time-domain stepwise fatigue assessment (TSFA) approach was proposed to consider complex dynamic fatigue loads. Firstly, a vehicle-bridge coupled maglev vehicle dynamic model

The effect of embedding in concrete on the fatigue performance of steel reinforcement bars is not evident. Some test series provided in literature demonstrate a higher fatigue resistance of embedded bars as compared to bars in air, whereas others provide a lower resistance. In addition, debate exists on the mechanisms behind the difference between tests in air and tests in concrete, if any. These mechanisms