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In the paper, new hybrid (numerical-analytical) methods to calculate the J-integral, the CTOD, and the load line displacement are presented. The proposed solutions are based on FEM calculations which were done for SEN(B) specimens dominated by plane strain condition. The paper includes the verification of the existing limit load solution for SEN(B) specimen with proposal of the new analytical formulae, which were used for building hybrid equations for determining three selected fracture mechanics parameters. [ABSTRACT FROM AUTHOR]

A computationally robust framework for simulating geomaterial failure patterns is presented in this paper. Finite element simulations which feature the use of embedded discontinuities to track material failure are known to suffer from convergence issues due to a lack of robustness. Oftentimes, complex time step-cutting schemes or arc-length methods are required in order to achieve convergence. This may invariably limit the complexity of constitutive models available for use in tracking nonlinear material behavior. To this end, we use an implicit-explicit integration scheme [Impl-Ex (Oliver et al. in Comput Methods Appl Mech Eng 195(52):7093-7114, 2006)] coupled with a novel constitutive model which allows for combined opening and shearing displacement in tension, as well as frictional sliding in compression. We show that this framework is suitable for capturing complex fracture patterns in geomaterial structures without the need for elaborate continuance schemes. [ABSTRACT FROM AUTHOR]

The paper develops a model based on the finite element analysis of the crack initiation and propagation in the generation IV structural materials due to the liquid metal embrittlement (LME) phenomenon. The stress-strain experimental curves obtained at 400 °C by testing in the liquid lead and air were converted as the Ramberg - Osgood constitutive equations by proposing a new method to obtain the strain hardening coefficient. To estimate the accuracy of prediction are used the residual and standardised residual in the context of regression analysis. Further, a model based on the Gurson-Tvergaard-Needleman approach (GTN) was set up to evaluate the crack initiation and propagation under the LME conditions. An application of the developed micro-mechanical model that predicts the crack initiation and propagation in the Compact -Tension (CT) specimen due to LME is performed. The model is practical in the structural integrity activities framework of the structural materials that will be used in the ALFRED demonstrator, which will be build-up at RATEN ICN, Romania. [ABSTRACT FROM AUTHOR]

Even if precast pre-stressed hollow-core (PPHC) slabs are usually designed as simply supported elements, continuity with the supporting beam may exist when constructed together with a reinforced concrete topping and continuity reinforcing bars. During an earthquake (and possibly other lateral load), this continuity may result in bending moments being induced close to the supports as the buildings sway laterally. The response of precast floors to earthquake-induced demands has been addressed by past research. However, further investigation is required to improve understanding of several aspects of precast floor behaviour either revealed or emphasized by recent earthquakes in New Zealand. This paper proposes a mechanics-based modelling approach for the analysis of PPHC slab-to-beam seating connections. The model has been calibrated against existing test data to predict the failure of a PPHC slab under negative bending moments. The numerical outcomes allow comparison of the moment–drift response, principal tensile stresses, and crack progression during loading. The developed modelling approach will allow future studies to exhaustively investigate all aspects of precast floor behaviour by varying the properties and geometry of the PPHC seating connection. [ABSTRACT FROM AUTHOR]

The present paper aims to study the crack propagating behavior of a stiffened plate under tensile and bending displacement load loads. The extended finite element method (XFEM) is used to analyze the residual ultimate strength of stiffened plates with a central crack. The quasi-static crack growth process is simulated by software ABAQUS. The validity of the grid is validated by the plate with a central crack. The numerical method is validated by comparing the fatigue crack growth rate of the round compact tension specimen (RCT) results of the extended finite element with experiment values. Influential parameters, including the size of the stiffened plates, heights of the stiffeners is varied, and uniaxial tensile and four-point bending models are analyzed. The results show that ultimate strength is reduced by the action of tensile and bending loads. The bottom plate and stiffener are destroyed with crack propagation, successively. With the increase in stiffener height, the crack resistance will also increase, thus restraining the central crack growth of stiffened plates. [ABSTRACT FROM AUTHOR]

Finite element analysis has become an essential tool for simulating and understanding crack growth. This technique holds significant importance in the field of mechanical engineering, where it finds wide application in the design and optimization of structural components and material properties. This work began with the identification of critical zones and estimated the number of load life repeats through fatigue analysis, specifically applied to automotive rims utilizing innovative finite element methods. To investigate crack behavior, we are used the Extended Finite Element Method (XFEM) with the volumetric approach to compute the Stress Intensity Factor (SIF). The results obtained by our study align closely with experimental tests in terms of detecting the critical zone where a crack can appear. Our findings contribute to the understanding of fatigue behavior in automotive rims, offering new insights into their structural integrity and performance under various load conditions. [ABSTRACT FROM AUTHOR]

Fracture mechanics is fundamental in various fields, such as mechanical engineering, civil engineering, hydraulics, and medicine. In addition, thanks to this field, we can estimate the age of the components of a structure, and the inspection and maintenance intervals can be precise. Thus, fracture mechanics is a science that studies numerical tools to characterize various parameters, such as the contour integral (J), stress intensity factors, and internal energy. However, in this paper, comparing the two types of elements (CPS3) and (CPS4R) gives comparable and proportional results; logically, a good correlation was obtained between them. In this article, those parameters were simulated and analyzed numerically by the finite element method (FEM) of a two-dimensional model consisting of a steel material with elastic properties. The analysis of the crack parameters was evaluated by the two models of elements CPS3 and CPS4R. On the other hand, the crack parameters between the two elements were compared. In addition, the numerical simulation was carried out using the computer code ABAQUS 16.3.1. [ABSTRACT FROM AUTHOR]

Many concrete structures, such as bridges and wind turbine towers, fail mostly due to the fatigue rapture and bending, where the cracks are initiated and propagate under cyclic loading. Modeling the fracture process zone (FPZ) is essential to understanding the cracking behavior of heterogeneous, quasi-brittle materials such as concrete under monotonic and cyclic actions. The paper aims to present a numerical modeling approach for simulating crack growth using a scaled boundary finite element model (SBFEM). The cohesive traction law is explored to model the stress field under monotonic and cyclic loading conditions. In doing so, a new constitutive law is applied within the cohesive response. The cyclic damage accumulation during loading and unloading is formulated within the thermodynamic framework of the constitutive concrete model. We consider two common problems of three-point bending of a single-edge-notched concrete beam subjected to different loading conditions to validate the developed method. The simulation results show good agreement with experimental test measurements from the literature. The presented analysis can provide a further understanding of crack growth and damage accumulation within the cohesive response, and the SBFEM makes it possible to identify the fracture behavior of cyclic crack propagation in concrete members. [ABSTRACT FROM AUTHOR]

Simulations of tunnel excavations have to take into account the natural occurrence of joints and faults in the surrounding rock mass, which dominantly control its mechanical response. In this paper, we present work in progress toward 3D finite element analysis of excavation using equivalent rock-mass properties derived from stochastically generated discrete fracture networks (DFNs). The equivalent stiffness is determined by volume averaging. Presently, we solve the problem linearly for an incremental change of the stress state. The fracture's stiffness is assumed to depend on the initial normal stress acting in direction normal to it. However, within the solved incremental step, we assume the fracture's stiffness to be constant. This assumption is acceptable for small stress changes. Since the fractures represented in the DFN model have preferred directions, the equivalent stiffness is anisotropic. [ABSTRACT FROM AUTHOR]

This paper presents a fully coupled thermo‐hydro‐mechanical (THM) model which simulates frost heave in fully saturated soils. The model is able to simulate the formation and growth of multiple distinct ice lenses. The basic equations of the system were derived using the continuum theory of mixtures, nonequilibrium thermodynamics, and fracture mechanics, considering skeleton deformation, water flow and heat transport. Central to this model is the coupled transport of mass due to the temperature gradient across the frozen fringe, which acts as the main driving force of the phenomenon. The model is formulated in terms of measurable physical properties and thus no ad hoc parametrization is required. In an ice‐lens‐free state, the system is solved as a continuum using the finite element method (FEM). It is then locally treated as a discontinuous system upon the formation of ice lens, by enriching the elements carrying the embedded ice lens(es) using the extended finite element method (X‐FEM). The accuracy and efficiency of the proposed model has been verified using several laboratory tests on Devon silt samples at different overburden pressures and thermal boundary conditions. Shut‐off pressures have been also estimated and compared with the experimental results. [ABSTRACT FROM AUTHOR]

This paper proposed an efficient two-dimensional fatigue crack growth simulation program for linear elastic materials using an incremental crack growth procedure. The Visual Fortran programming language was used to develop the finite element code. The adaptive finite element mesh was generated using the advancing front method. Stress analysis for each increment was carried out using the adaptive mesh finite element technique. The equivalent stress intensity factor is the most essential parameter that should be accurately estimated for the mixed-mode loading condition which was used as the onset criterion for the crack growth. The node splitting and relaxation method advances the crack once the failure mechanism and crack direction have been determined. The displacement extrapolation technique (DET) was used to calculate stress intensity factors (SIFs) at each crack extension increment. Then, these SIFs were analyzed using the maximum circumferential stress theory (MCST) to predict the crack propagation trajectory and the fatigue life cycles using the Paris' law model. Finally, the performance and capability of the developed program are shown in the application examples. [ABSTRACT FROM AUTHOR]

The fractures of thin plates often exhibit complex physical behaviors in the real world. In particular, fractures caused by tearing are different from fractures caused by in-plane motions. In this paper, we study how to make thin-plate fracture animations more realistic from three perspectives. We propose a stress relaxation method, which is applied to avoid shattering artifacts after generating each fracture cut. We formulate a fracture-aware remeshing scheme based on constrained Delaunay triangulation, to adaptively provide more fracture details. Finally, we use our multi-layered model to simulate complex fracture behaviors across thin layers. Our experiment shows that the system can efficiently and realistically simulate the fractures of multi-layered thin plates. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to use numerical methods early in the airframe design process and access the structural performance of wing leading edge devices made of different materials and design details, under bird strike events. Design/methodology/approach: Explicit finite element analysis was used to numerically model bird strike events. Findings: Structural performance charts related to materials and general design details were drawn to explore the design space dictated by the current applicable airworthiness requirements. Practical implications: This paper makes use of the current capability in the numerical tools available for structural simulations and exposes the existing limitations in the terms of material modelling, material properties and fracture simulation using continuum damage mechanics. Such results will always be in the need of fine-tuning with experimental testing, yet the tools can shed some light very early in the design process in a relative inexpensive manner, especially for design details down selection like materials to use, structural thicknesses and even design arrangements. Originality/value: Bird strike simulations have been successfully used on aircraft design, mainly at the manufactured articles design validation, testing and certification. This paper presents a hypothetical early design case study of leading edge devices for appropriate material and skin thickness down selection. [ABSTRACT FROM AUTHOR]

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Vibration-based damage detection is based on the fact that vibration characteristics such as natural frequencies and mode shapes of structures are changed when the damage is happened. The vibration-based damage detection of a beam is formulated as a single-objective optimization problem in which genetic algorithm (GA) is used as the optimizer. This paper presents the encoding by locations and damage factor (ELD) which employs location and damage amount as the decision variables. The proposed encoding can reduce the number of decision variables that used in the previous encoding, the encoding by damage factor of each element (EDE). The search space of GA with ELD is then smaller than that of GA with EDE. The simulation results reveal that GA with ELD can identify the damage occurred in the beam more correctly than GA with EDE. Moreover, the damage predicted by GA with ELD is quite close to the actual damage for all 3 test cases. [ABSTRACT FROM AUTHOR]

The paper deals with investigation of the interaction between an edge-crack and an aggregate in a silicate-based composite, because adding of aggregates into basic matrix material can improve the fracture mechanical properties of the material significantly. In this work, the three-point-bending test is modelled by means of the finite element method and the dependences of fracture parameters on various material and geometrical parameters of the aggregate and the interfacial transition zone are studied. The results are discussed thoroughly. [ABSTRACT FROM AUTHOR]

Considering fracture constraint is an efficient way to describe stress-strain field and fracture toughness more accurately, so it is necessary to realise the relationship with in-plane and out-of-plane constraint for different standard specimens. In this paper, three-dimensional finite element method is applied to study the in-plane and out-of-plane constraint for both cruciform specimen and single edge notched bending specimen made from commercial pure titanium. Crack length and in-plane loading as the factors affecting in-plane constraint, and thickness as the factor affecting the out-of-plane constraint are used to study the effect on both in-plane and out-of-plane constraint in this paper. From the results, in-plane and out-of-plane constraint are both related to specimen geometries and loading styles. And there exist relationships with in-plane and out-of-plane constraint because of factors for different specimens. Depending on crack length, out-of-plane constraint increases with in-plane constraint. While depending on transverse loading, out-of-plane constraint decreases with in-plane constraint. In addition, when the in-plane constraint of a specimen is higher, in-plane constraint increases with out-of-plane constraint (thickness). When the in-plane constraint is lower, in-plane constraint almost remains unchanged with out-of-plane constraint. [ABSTRACT FROM AUTHOR]

The spherical pressure hull used in the manned cabin of deep-sea submersibles endures low-cycle fatigue problems during the process of cyclic submergence and recovery, but fatigue testing on its full-scale model is difficult to conduct. To approximate the problem, the paper proposed the design of an L-type equivalent welding joint to simulate the status of the strengthened part of the spherical pressure hull under a certain cyclic axial pressure history. The design principle of the equivalent welding joint is to ensure that the stress ratio between inner and outer surface and the distribution of the simulated test piece should be similar to or smaller than the actual stress distribution characteristics in the critical zone of the spherical hull for conservative consideration. The angle of the L-type joint is 175° in the present study, at which the stress on the outside is at the turning point from compressive stress to tensile stress. The fatigue experiment of the equivalent welding joint is conducted with measurements of crack growth and residual stresses. Multiple cracks are observed in the vicinity of the weld, which grows showing a typical low-cycle fracture morphology. The three-dimensional finite element modelling for the equivalent welding joint with prefabricated notch and the same weld zone shape with its tested piece is carried out. An improved crack growth model proposed by the author's group, considering multiple factors, is adopted for crack growth calculation and compared with experimental results, which shows satisfactory agreement. The finite element modelling based on the pre-designed L-type joint combined with the improved crack growth rate model can be applied as a simplified method to simulate the fatigue life of the spherical pressure hull. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to develop a variational formulation for predicting structure behavior and accounting for damage mechanics in metallic materials. Mechanical and coupled thermomechanical models are used to predict failure in manufacturing processes. Ductile failure is accompanied by a significant amount of plastic deformation in metallic structural components. Finite element simulation of damage evolution in ductile solids is presented in this paper. Uncoupled models are implemented in a finite element model simulating deep drawing as well as cutting processes. Based on the Johnson–Cook model, the effect of deformation on the evolution of flow stress is described. The combined effect of strain, strain rate, and temperature on plasticity and damage behavior in cutting processes is considered. The accuracy of these models is verified when predicting ductile damage in forming and cutting processes. [ABSTRACT FROM AUTHOR]

This paper presents the Finite Element (FE) analyses carried out with the aim to predict the tooth root fatigue and Rolling Contact Fatigue (RCF) behavior of spur gears, in terms of crack propagation maximum number of cycles. The combination of different materials, i.e. steel and titanium, and surface treatments, i.e. case-hardening and application of surface layers by Physical Vapor Deposition (PVD), are investigated. The residual stresses induced by the deposition of the coating are modelled. The stress intensity is described by linear elastic relations based on the crack tip opening displacement and the crack propagation in the case-hardened spur gears is described with the help of mathematical models. Experiments are carried out to evaluate tooth damage under RCF for different treated gears. The best solutions in terms of bulk material – treatment combination among the ones investigated are identified, also highlighting innovative possibilities which can guarantee appreciable performance. [ABSTRACT FROM AUTHOR]

The crack closure phenomenon significantly influences low cycle fatigue (LCF) crack growth. The crack closure theory deems that a crack can grow only when the applied load is greater than the fatigue crack opening and closing loads. The revised crack closure theory proposed in this paper provides a new understanding of crack growth: It is no longer the range of stress intensity factor ΔK that controls the crack growth rate, but the effective stress intensity factor ΔKeff. Therefore, it is of great importance to study the crack closure phenomenon of LCF. A combination of experiments and the finite element method (FEM) was used to study the effect of overload on the crack closure effect, and the study was carried out using compact tensile (CT) specimens made of AH32 steel. The FEM was used to obtain the stress changes near the crack tip and the opening displacement changes in the crack trailing area after a single tensile overload, to study the intrinsic mechanism of overload on crack closure, and to obtain the LCF crack opening and closing loads by the nodal displacement method. The effect of overload on crack morphology was observed by using high-magnification electron microscopy in combination with testing. [ABSTRACT FROM AUTHOR]

In order to better understand the interfacial debonding behavior of pipe joints during the whole loading process, an analytical solution for the full-range behavior of adhesively bonded pipe joints under combined thermal and mechanical tensile loadings is presented in this paper. The solution was developed based on a simplified rigid-softening bond–slip model, and two cases with different softening region development were discussed. The analytical results were presented in a finite element model, and the effect of temperature on load–displacement curves and ultimate loads was shown based on the model. Through the nonlinear fracture mechanics, the analytical expressions of the interfacial shear stress and the load–displacement relationship can be obtained. The stress transfer mechanism, the interface crack propagation and the ductility behavior of the joints can be explained. This analytical result can help improve the potential application of fabricated structural components, precision instruments, oil and gas pipelines. [ABSTRACT FROM AUTHOR]

Weibull stress is widely used to predict the probability of cleavage fracture with local approaches. However, the calculation of Weibull stress requires detailed elastic plastic finite element analyses, which limit the application of local approaches in engineering practice. In this paper, analytic and semi-analytic solutions of Weibull stress for 2D crack/notch models with elastic and elastic–plastic materials under mode II loading are obtained, which allow the Weibull stress to be estimated according to the macroscopic fracture mechanics parameters like stress intensity factor K or J integral together with material properties. The obtained Weibull stress solutions are verified by using results of finite element analyses with modified boundary layer models and a single-edge-notched specimen. The results show that the Weibull stress solutions of this paper can predict the results calculated by direct finite element analyses very well. [ABSTRACT FROM AUTHOR]

Assessing the failure stability of engineering structures under service loadings by means of relevant crack growth concepts is one of key issues in damage tolerance analysis. Therefore, the behaviour of fatigue damages is theoretically examined through the crack growth rate. This paper describes a straightforward methodology to generate failure resistance under cyclic loading. To explore fatigue behaviour of two through--the--thickness cracks located at a hole, the stress intensity factor and life are estimated by means of developed analytical model. Stress state field is numerically analysed using the finite element method. Through relevant applications predictive capability of estimates is discussed. Relevant failure evaluations are performed in the case of complex--valued functions by employing the Euler's integration method, which is implemented in the software program developed. Whereas the type of cracks examined is taken into account through the stress intensity factor. [ABSTRACT FROM AUTHOR]

Over the last few decades, cardiovascular stents have emerged as crucial biomedical devices. Stents undergo cyclic physiological loading, which can lead to progressive accumulation of structural damage over time eventually resulting in a stent fracture. Considering the critical role of stents, it is necessary to assess their fatigue endurance and predict a potential premature failure due to fatigue loading. This paper presents a comprehensive analysis of coronary stent design based on both fatigue failure and damage-tolerant approaches. Employing the fatigue failure approach, S-N analysis was conducted to pinpoint the critical zones of the stent. Initial resistance to fatigue was evaluated using Goodman's and Soderberg's criteria. These criteria were applied to principal and effective stresses obtained using the Finite Element Method. Susceptibility to fatigue damage was performed by simulating the initial crack growth, and it was assessed through the Paris power law. The damage-tolerant approach yields more conservative fatigue stress ranges compared to fatigue failure criteria, ensuring safety under standard physiological loading conditions. The presented approach offers reliable insights into stent durability, with potential for further enhancement. [ABSTRACT FROM AUTHOR]

Failure of many brittle materials and structures can be modeled using interface‐oriented finite elements combined with intrinsic cohesive zone models. The discontinuous Galerkin (DG) finite element method provides an innovative framework for modeling brittle crack propagation with zero‐thickness interface elements, which can accommodate extrinsic cohesive laws to avoid the artificial compliance required in intrinsic cohesive models. However, robust formulations and implementations of DG methods are critical in alleviating the well‐known convergence issues for both crack nucleation and propagation with reduced instability. This paper presents a robust interface element formulation by modifying the incomplete interior penalty Galerkin (IIPG) method, which successfully avoids the initial element interface penetration across elements that occurs prior to crack nucleation, and thereby greatly reduces the instability issue as cracks open. We further verified and validated our implementation by using a bar tension test and a beam fracturing benchmark. The robustness of our proposed interface element method was demonstrated by a micromechanics fiber/matrix debonding problem with 64 fibers embedded in a bulk matrix. [ABSTRACT FROM AUTHOR]

Surface cracks are commonly observed in coatings and films. When structures with coatings are subject to stretching, opening mode cracks are likely to form on the surface, which may further lead to other forms of damage, such as interfacial delamination and substrate damage. Possible crack forms include cracks extending towards the interface and channeling across the film. In this paper, a two-dimensional numerical model is proposed to obtain the structural strain energy at arbitrary crack lengths for bilayer structures under uniaxial tension. The energy release rate and structural stress intensity factors can be obtained accordingly, and the effects of geometry and material features on fracture characteristics are investigated, with most crack patterns being confirmed as unstable. The proposed model can also facilitate the analysis of the stress distribution in periodic crack patterns of films. The results from the numerical model are compared with those obtained by the finite element method (FEM), and the accuracy of the theoretical results is demonstrated. [ABSTRACT FROM AUTHOR]

The paper investigates the interaction of a steel striker with a three-layer target barrier. The barrier had three layers: ceramic, orthotropic organoplastic, and aluminum. The interaction velocity was 841 m/s, and the initial interaction angles with the barrier surface were set normal and 45°. The study is carried out numerically by the finite element method in a three-dimensional setting using the computer complex EFES developed by the authors. An elastic-brittle model is proposed to describe the behavior of the composite. A tensor-polynomial criterion of the second degree is used for the composite fracture. To describe the fracture of the orthotropic material of the target barrier, a two-stage model is proposed. The model of the composite behavior takes into account different strength moduli in compression and tension. As a criterion for the ceramics fracture, the deformation criterion was used. The behavior of the striker material and the metal layer are described by an elastoplastic medium, for the fracture of which a deformation criterion is proposed based on the limiting value of plastic deformation. The influence of the layer arrangement and initial interaction angle on the fracture of the target barrier has been studied. [ABSTRACT FROM AUTHOR]

In this paper, the effect of thermal stress on crack-inclusion problem in inhomogeneous superconducting cylinder in the cooling process is investigated. By using the gradient finite element method, the thermodynamic coupling equation is solved numerically and the thermal stress is obtained during the drop from room temperature to operating temperature. Then the stress intensity factors for the cooling process are solved. The effects of thermal stress on crack growth are discussed, and the effects of the inclusion on crack growth under thermal stress are analyzed. According to the results, the crack length increases to promote the crack growth, then the effect of thermal stress on the crack growth increases as the crack length increases. In addition, the size and type of the inclusion, as well as the distance of the inclusion from the crack tip, can also affect the crack extension. [ABSTRACT FROM AUTHOR]

This paper conducted experiments and theoretic analysis of the fracture performance of pultruded GFRP (Glass Fiber Reinforced Polymers) laminates. The mode-I fracture toughness of pultruded GFRP laminates was evaluated by the eccentrically loaded, Extended Compact Tension (ECT) specimen. The geometry of specimen and experimental procedure refer to ASTM E1922. A total of 16 specimens were tested, which included 0° and 90° roving orientation. Finite element analysis with the Virtual Crack Closure Technique (VCCT) was implemented to calibrate the experimental results. A correction function for normalized notch length was proposed for pultruded GFRP translaminar fracture toughness. Carpet plot was designed to discuss the relationship between fiber volume ratio and fracture toughness, which demonstrated that the fracture toughness strongly correlated with the fiber volume ratio. Also, the effect of fraction of 0° layers on fracture toughness and material orthotropy was studied. The relationship of material orthotropy parameter and fracture toughness was discussed. [ABSTRACT FROM AUTHOR]

In the context of the eXtended Finite Element Method (X-FEM), the use of two level set functions allows the representation of the crack to be achieved regardless of the mesh. The initial crack geometry is represented by two distinct level set functions, and the crack propagation is simulated by an update of these two level set functions. In this paper, we propose a new approach, based on the Fast Marching Method (FMM), to update the level set functions. We also propose a new implementation of the FMM, designed for tetrahedral volume meshes. We then extend this method to all types of volume elements (tetrahedra, hexahedra, pentahedra, pyramids) available in a standard finite element library. The proposed approach allows one to use the same mesh to solve the mechanical problem and to update the level set functions. Non-planar quasi-static crack growth simulations are presented to demonstrate the robustness of the approach, compared to existing methods based on the integration of Hamilton-Jacobi equations or geometric approaches. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to investigate the interface relaxation FEM–BEM coupling method to resolve problems involving nonlinear fracture mechanics. In this coupling technique, the nonlinear portion near the crack tip is modeled by the finite element method (FEM) and the remainder of the domain which is linear elastic is discretized using the boundary element method (BEM). In the coupling procedure adopted here, there is no need to combine the coefficients matrices of FEM and BEM subdomains and separate computing for each subdomain with successive renewal of the variables on the interface are performed to reach the final convergence. To demonstrate the effectiveness of the developed approach, several practical problems of nonlinear fracture mechanics are analyzed. The conventional FEM computations are also performed, and a critical comparison of the results is made. [ABSTRACT FROM AUTHOR]

The operation modes for the proposed FCC-ee collider foresee a very small beam spot size and stored beam energies of up to 20.6 MJ in Z production. This necessitates a dedicated beam dumping system. To reduce the complexity of the system as well as to minimize the required space, an optimized, semi-passive system has been designed and is presented here. The beam dilution is done with a defocusing triplet structure, followed by passive beam diluter elements (spoilers). This greatly reduces the risk of possible dilution failure scenarios compared to an active dilution kicker-magnet system. The dump core itself is located ∼ 70 m downstream of the spoilers and is designed following the experience gained from the LHC dump. The dilution performance as well as the interaction effects responsible for the energy deposited in the spoiler, are directly related to the radiation length and the dimension of the device in beam direction. Materials for these spoilers have been studied extensively and key requirements have been identified using both Monte Carlo shower simulations and thermo-mechanical Finite Element Analysis. Even though the maximum temperature reached in the spoilers is well within the working temperature range of the material, the induced mechanical stresses can lead to material failure. Thermo-mechanical simulations have shown that the transversal beam shape plays a key role in the magnitude of mechanical stresses as a result of the beam impact and the abrupt temperature change. This problem is addressed in this paper and an optimized solution is presented. [ABSTRACT FROM AUTHOR]

• For blunt crack tips, as the radius increases, the specimens' compliance also increases. • For sharp crack tips, as the element size of the crack tip increases, the specimens' compliance decreases. • Similar compliance results are obtained for both meshes when the radius or element size of the crack tip are low enough. • Two models were created that show the crack tip radius or the element size impact on the elastic unloading compliance. • A parameter that normalizes the crack tip radius or the element size with the specimens' width is proposed. Elastic unloading compliance is a common technique to determine instantaneous crack size in fracture mechanics properties such as resistance curves (R-curves) and fatigue crack growth. This technique uses a polynomial, developed using finite elements models, to correlate compliance with crack depth. In these models, crack tip is usually modeled with a blunt mesh (with a crack tip radius ρ) or a sharp mesh (with element size in the width direction l) , and neither are standardized in the literature. This paper shows that both affect compliance, therefore potentially impacting results of fracture mechanics properties acquired from simulations. This paper focuses on how those parameters affects compliance in SE(B) models. Finally, a parameter φ that normalizes ρ or l with the width was developed and recommended values based on compliance convergence are suggested. Controlling φ may help to ensure reliable results in fracture mechanics models where compliance needs to be determined. [ABSTRACT FROM AUTHOR]

This paper introduces a novel method for assessing fracture mechanics parameters such as Stress Intensity Factor (SIF), Energy Release Rate (J) and Crack Tip Opening Displacement (CTOD). An electromagnetic–mechanical coupling (EMC) approach is employed to evaluate and to measure these fracture parameters by monitoring the variation of impedance using eddy currents. This approach relies on the eddy current signal obtained from a sensor, which calculates and verifies SIF parameters along with the J-integral and CTOD through changing the sensor impedance. To ensure theoretical consistency, the magnetic field is theoretically used, formulated and verified. Additionally, a numerical simulation method employing the finite element method is used to analyze and identify cracks in structures and assess their propagation. The quantification of SIF and J-integral parameters is demonstrated using two sensors based on a differential probe. This research paper demonstrates that the proposed method is the most efficient approach for exploring and detecting cracks in materials, as well as understanding their propagation behavior. [ABSTRACT FROM AUTHOR]

Nowadays, the use of timber as a building material is gaining more prominence. When designing timber structures, it is necessary to pay increased attention to the design of their connections. The commonly used connections are dowel-type connections, which are often used in combination with steel plates slotted into cut-outs in timber members. The presented paper deals with the behavior of double-shear bolted connections of squared timber and round timber with slotted-in steel plates. Several variants of connections with different distances between the fastener and the loaded end were selected for the experimental testing. A total of six types of test specimens were made from spruce timber, for which their selected physical properties were determined and evaluated before the experimental testing. Test specimens of bolted connections were first tested in tension parallel to the grain until failure under quasi-static loading. The connections were broken by splitting. Ductile failure preceded brittle failure. The actual load-carrying capacities were lowest for the lowest end distance. The load-carrying capacities for the middle and the longest end distances were comparable. The results of the experiments were then used for comparison with calculation procedures according to the standard for the design of timber structures and with calculations according to the theory of linear elastic fracture mechanics. The experiments and the analytical models were supported by a simple numerical analysis based on the finite element method. [ABSTRACT FROM AUTHOR]

The modeling of the structural behavior of composite materials is an interesting but complex task since the response of the material to loading structural may be difficult to predict, and the failure may be manifested in different forms. In cross-ply fiber-reinforced composites, the major failure mechanisms include: (i) the failure of the matrix material (transverse cracking), (ii) delamination and (iii) the breakage of the fibers. The process of the transverse cracking is a well studied damage mechanism and can be used in numerical simulations, in order to study the effects of various parameters on the crack density. In this paper, the finite element modeling of a cross-ply composite under uniaxial loading in tension is performed using ABAQUS software, considering all the potential damage mechanisms. The model takes into account shear-lag effect for the determination of the stress transfer and furthermore it adopts a homogenization procedure for the calculation of elastic and viscoelastic material properties. Stochasticity is introduced by assigning various interfacial strengths that follow a Gaussian distribution, so as to predict the cracking sequence up to saturation in the transverse to the 0 ∘ layers. The results are directly compared with available experimental measurements showing reasonable agreement. Finally, a cross-ply RVE model was created and loaded in uniaxial tension and crack propagation is modelled with the Extended Finite Element Method (XFEM). The stress concentration calculations around the crack tips are in agreement with the mesoscale model. [ABSTRACT FROM AUTHOR]

Empirical criteria and fracture/damage mechanics are used to evaluate the safety of lining cracks in the conventional methods. However, the former lacks a scientific basis, and the latter requires complicated mechanical calculations. To overcome the above shortcomings, this paper proposes a new method to perform crack analysis of plain concrete linings, based on the double-K fracture criterion. The proposed method uses two crack width indices, i.e., initiation and unstable fracture widths, to divide the fracture process of lining into three stages: initiation stage, stable propagation stage, and instability propagation stage. These two crack width indices are calculated by the equivalent transformation of fracture toughness. Using the proposed criterion, the safety state of the concrete lining can be determined by comparing the field measurement width and crack width indices. A specific code based on the extended finite element method (XFEM) is developed to simulate the fracture process of concrete lining. Several numerical experiments are carried out to evaluate the proposed fracture criterion. The results show that the two fracture indices of the proposed criterion can accurately identify two demarcation points of the three stages of the lining fracture process, including the nonlinear starting point and the unstable fracture point of the load–displacement curve. Compared with conventional methods, the proposed method uses the geometric parameter to estimate the mechanical state of cracks, so the complicated mechanical calculation can be avoided. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study on the effects of microwave irradiation on the mechanical properties of hard rock. More specifically, the weakening effect of microwave heating induced damage on the uniaxial compressive and tensile strength of granite-like rock is numerically evaluated. Rock fracture is modelled by means of a damage-viscoplasticity model with separate damage variables for tensile and compressive failure types. We develop a global solution strategy where the electromagnetic problem is solved first separately in COMSOL multiphysics software, and then provided into a staggered implicit solution method for the thermo-mechanical problem. The thermal and mechanical parts of the problem are considered as uncoupled due to the dominance of the microwave-induced heat source. The model performance is tested in 2D finite element simulations of heterogeneous numerical rock specimens subjected first to heating in a microwave oven and then to uniaxial compression and tension tests. According to the results, the compressive and tensile strength of rock can be significantly reduced by microwave heating pretreatment. [ABSTRACT FROM AUTHOR]

The advent of the Three-Dimensional (3D) printing technique, as an Additive Manufacturing technology, made the manufacture of complex porous scaffolds plausible in the tissue engineering field. In Fused Deposition Modeling based 3D printing, layer upon layer deposition of filaments produces voids and gaps, leading to a crack generation and loose bonding. Cohesive zone model (CZM), a fracture mechanics concept, is a promising theory to study the layers bond behavior. In this paper, a combination of experimental and computational investigations was proposed to obtain bond parameters and evaluate the effect of porosity and microstructure on these parameters. First, we considered two different designs for scaffolds beside a non-porous Bulk design. Then, we performed Double cantilever beam and Singe Lap Shear tests on the 3D printed samples for Modes I and II, respectively. Afterward, we developed the numerical simulations of these tests using the Finite element method (FEM) to obtain CZM bond parameters. Results demonstrate that the initial stiffness and cohesive strength were pretty similar for all designs in Mode I. However, the cohesive energy for the Bulk sample was approximately four times of porous samples. Furthermore, for Mode II, the initial stiffness and cohesive energy of the Bulk model were five and four times of porous designs while their cohesive strengths were almost the same. Also, using cohesive parameters was significantly enhanced the accuracy of FEM predictions in comparison with fully bonded assumption. It can be concluded that for the numerical analysis of 3D printed parts mechanical behavior, it is necessary to obtain and suppose the cohesive parameters. The present work illustrates the effectiveness of CZM and FEM combination to obtain the layer adhesive parameters of the 3D printed scaffold. [ABSTRACT FROM AUTHOR]

The elastoplastic field near crack tips is investigated through finite element simulation. A refined mesh model near the crack tip is proposed. In the mesh refining area, element size continuously varies from the nanometer scale to the micrometer scale and the millimeter scale. Graphics of the plastic zone, the crack tip blunting, and the deformed crack tip elements are given in the paper. Based on the curves of stress and plastic strain, closely near the crack tip, the stress singularity index and the stress intensity factor, as well as the plastic strain singularity index and the plastic strain intensity factor are determined. The stress and plastic strain singular index vary with the load, while the dimensions of the stress and the plastic strain intensity factors depend on the stress and the plastic strain singularity index, respectively. The singular field near the elastoplastic crack tip is characterized by the stress singularity index and the stress intensity factor, or alternatively the plastic strain singularity index and the plastic strain intensity factor. At the end of the paper, following Irwin's concept of fracture mechanics, σ δ K criterion and ε δ Q criterion are proposed. Besides, crack tip angle criterion is also presented. [ABSTRACT FROM AUTHOR]

We have discovered a peculiar form of fracture that occurs in a highly stretchable silicone elastomer (Smooth-On Ecoflex 00-30). Under certain conditions' cracks propagate in a direction perpendicular to the initial precut and in the direction of the applied load. In other words' the crack deviates from the standard trajectory and instead propagates perpendicular to that trajectory. The crack arrests stably, and thus the material ahead of the crack front continues to sustain load, thereby enabling enormous stretchabilities. We call this phenomenon "sideways" and stable cracking. To explain this behavior, we first perform finite-element simulations that demonstrate a propensity for sideways cracking, even in an isotropic material. The simulations also highlight the importance of crack-tip blunting on the formation of sideways cracks. Next, we provide a hypothesis on the origin of sideways cracking that relates to microstructural anisotropy (in a nominally isotropic elastomer). To substantiate this hypothesis, we transversely prestretch samples to various extents before fracture testing, as to determine the influence of microstructural arrangement (chain alignment and strain-induced crystallization) on fracture energy. We also perform microstructural characterization that indicates that significant chain alignment and strain-induced crystallization indeed occur in this material upon stretching. We conclude by characterizing how a number of loading conditions, such as sample geometry and strain rate, affect this phenomenon. Overall, this paper provides fundamental mechanical insight into basic phenomena associated with fracture of elastomers. [ABSTRACT FROM AUTHOR]

Glued-in rods (GiR) represent a very successful type of adhesively bonded joints in timber engineering. Despite their apparent geometrical simplicity, their dimensioning still challenges practitioners. A major source of mechanical complexity resides in the orthotropic nature of the wood, or engineered wood products, as laminated veneer lumber (LVL). This paper presents a relatively simple design approach based upon fracture mechanics (FM) and associated double-cantilever beam (DCB) tests that complemented tensile tests for material characterisation. In comparison with the state-of-the-art related to FM in timber engineering, the paper presents a practitioner oriented approach of a yet complex set of GiR geometries involving beech LVL (M16-8.8 threaded rods embedded in cross sections of 120 × 120 mm2 and embedment lengths of 96mm, 128mm and 160mm). The developed numerical model resulted in a good description of the load-displacement of a series of full scale, including very good estimates of their load capacities. Additionally, it allowed for significant insights regarding the complicated relationship between geometry, orthotropy, strength of the component and failure of the GiR, as for examples the complex fracture process, and the importance of transverse tensile stresses, which play a preponderant role, equal in importance to shear stresses. [ABSTRACT FROM AUTHOR]

The experimental results of a novel ultrasonic monitoring method to identify different types of flaws in reinforced concrete are presented. The authors' previous work has demonstrated the ability to use the proposed ultrasonic guided wave leakage (UGWL) to identify the onset of mechanical delamination. This paper presents the results from using the UGWL method to identify chemical delamination (corrosion) and cracking in concrete (other than delamination at the steel-concrete interface) in reinforced concrete. The proposed UGWL method monitors the change in amplitude of ultrasonic waves leaked from a guided wave transmitted through an embedded steel reinforcing bar. The energy of UGWL is influenced by the conditions between the steel reinforcing bar, acting as the waveguide, and the surrounding concrete. This experimental study demonstrated that the UGWL monitoring method is sensitive not only to the onset of delaminations, but also to the development of corrosion activity and cracks. [ABSTRACT FROM AUTHOR]

Summary: This paper describes a particular formulation of the extended finite element method (XFEM) specifically conceived for application to existing discontinuities of fixed location, for instance, in geological media. The formulation is based on two nonstandard assumptions: (1) the use of sub‐interpolation functions for each subdomain and (2) the use of fictitious displacement variables on the nodes across the discontinuity (instead of the more traditional jump variables). Thanks to the first of those assumptions, the proposed XFEM formulation may be shown to be equivalent to the standard finite element method with zero‐thickness interface elements for the discontinuities (FEM+z). The said equivalence is theoretically proven for the case of quadrangular elements cut in two quadrangles by the discontinuity, and only approximate for other types of intersections of quadrangular or triangular elements, in which the XFEM formulation corresponds to a kinematically restricted version of the corresponding interface plus continuum scheme. The proposed XFEM formulation with sub‐interpolation, also helps improving spurious oscillations of the results obtained with natural interpolation functions when the discontinuity runs skew to the mesh. A possible explanation for these oscillations is provided, which also explains the improvement observed with sub‐interpolation. The paper also discusses the oscillations observed in the numerical results when some nodes are too close to the discontinuity and proposes the remedy of moving those nodes onto the discontinuity itself. All the aspects discussed are illustrated with some examples of application, the results of which are compared with closed‐form analytical solutions or to existing XFEM results from the literature. [ABSTRACT FROM AUTHOR]