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Using the example of assessing the technical condition of the trunnions of drying cylinders in cardboard machines (CBM), the question of the possibility of ranking cyclically loaded elements of dynamic equipment according to the degree of damage to their material by fatigue cracks using acoustic emission (AE) measurements is discussed. As a result of special laboratory studies with varying loads in the cycle of loading and lubrication of crack edges, the features of AE due to the friction of crack edges and plastic deformation at the crack tip during its growth in a viscous material have been established. It is shown that during cyclic loading of the material, AE signals from the friction of its banks are detected more steadily than AE signals due to a crack jump with an increase in its length, and that tracking the former ensures the detection of fatigue damage in the material even under loading conditions insufficient for crack growth. Based on the data obtained, three AE signs of the presence of fatigue damage in the material of the elements of dynamic equipment were developed under the condition of cyclic activation of the movement of crack edges. As a result of industrial testing of the developed AE signs, their operability was confirmed, their boundary values on the operating trunnions of CBM drying cylinders were clarified, and a method for ranking trunnions by the level of damage due to fatigue cracks was proposed. By comparing the results of AE measurements with ultrasound testing, the reliability of the proposed approach was evaluated and showed the probability of detecting a fatigue crack in the trunnions of CBM drying cylinders at the level of 71%, with the probability of skipping and false rejection of the product of 12 and 17%, respectively. The developed technique is also transferable to other massive dynamic equipment after clarifying the boundary values of AE signs of fatigue damage in the material on this type of facilities. [ABSTRACT FROM AUTHOR]

: We analyze 6500 mm long fracture lines of paper as an example of crack propagation involving disorder. The cracks are asymptotically self-affine, with a roughness exponent close to 0.6. Systematic deviations from the power-law-scaling exist below a lengthscale related to the microscopic heterogeneities and possibly to a cross-over from 3d to 2d crack propagation. Several analysis methods are discussed, including first return analysis and the detection of correlated trends. [ABSTRACT FROM AUTHOR]

Shale anisotropy characteristics have great effects on the mechanical behaviour of the rock. Understanding shale anisotropic behaviour is one of the key interests to several geo-engineering fields, including tunnel, nuclear waste disposal and hydraulic fracturing. This research adopted the finite discrete element method (FDEM) to create anisotropic shale models in ABAQUS. The FDEM models were calibrated using the mechanical values obtained from published laboratory tests on Longmaxi shale. The results show that the anisotropic features of shale significantly affect the brittleness and fracturing mechanism at the micro-crack level. The total fracture number in shale under the Uniaxial Compressive Strength (UCS) test is not only related to the brittleness of shale. It is also strongly dependent on the structure of the shale, which is sensitive to shale anisotropy. Two new brittleness indices, BIf and BICD, have been proposed in this paper. The expression for BIf directly incorporates the number of fractures formed inside of the rock, which provides a more accurate frac-ability using this brittleness index. It can be used to calculate the frac-ability of rocks in projects where there are concerns about fractures after excavation. Meanwhile, BICD links brittleness to the CD/UCS ratio in shale for the first time. BICD is easy to obtain in comparison to other brittleness indices because it is based on the Uniaxial Compressive Strength test only. In addition, it has been shown there is a relationship between tensile strength and the crack damage strength in shale. Based on this, an empirical relationship has been proposed to predict the tensile strength based on the Uniaxial Compressive Strength test. Highlights: Through the use of FDEM simulations, the fracturing mechanics of shale, fracturing behaviour, and brittleness of shale have been investigated from a micro-scopic viewpoint taking shale anisotropy into account. Two new brittleness indices are proposed. One relies on the number of fractures in the shale to reflect the shale's frac-ability, and the other uses strength parameters that can be easily obtained from UCS tests. This paper proposes an empirical relationship to predict the tensile strength of rocks based on UCS tests. [ABSTRACT FROM AUTHOR]

This paper describes a new arc-length control procedure for tracing the equilibrium curve of brittle fracture problems modeled with a phase field approach. The balance equations of this model are solved with a staggered strategy. The control equation of the arc-length procedure determines the displacement increments during the mechanical stage. The arc-length parameter is interpreted as imposing a given increment of the driving force appearing into the micro-force balance equation. The innovative technique consisting of applying the control equation to the displacement degrees of freedoms (DOFs) of the mechanical stage offers an enhancement over earlier arc-length strategies that focused on controlling the damage DOFs in the micro-force balance equation stage. This advancement enables the phase field approach to handle and simulate a broader range of problems, as demonstrated in this paper. The arc-length parameter is stepwise adjusted to yield a pre-established maximum damage increment in each staggered scheme step. As a consequence, the crack tip advance can be strictly controlled in every step holding bounded the pseudo-time integration error, even using an explicit staggered strategy. This procedure entails moderate computational costs for tracing the complete equilibrium curve, including unstable responses, limit points, snap-backs, etc., with the subsidiary advantage that lack of convergence has never been detected in the tests presented in this paper. Additionally, line search techniques have not been necessary. The proposed arc-length procedure is easily implemented in standard finite element codes, and according to our numerical experiments, it does not significantly increase the computational burden of the original explicit staggered strategy. [ABSTRACT FROM AUTHOR]

It is very important to predict the blasting fragmentation size of fractured rock mass. Based on the geological conditions of practical engineering rock mass, a plane analysis model of bench blasting in layered rock mass considering microcrack structure was established. And the distribution law of stress in the bench blasting of layered rock mass with different occurrence and layer thickness is analyzed by using the CDEM numerical simulation method. Combined with the theory of rock fracture mechanics and relevant test results, this paper quantitatively studied the change laws of the angle for the cracks to propagate, speed and crack initiation length at different particle points in bench blasting and realized the time history analysis of the crack development and rock fragmentation in bench blasting. And then, this paper derived the quantitative relationship between the post-expansion cranny ratio and the blasting fragmentation from a theoretical point of view, and proposed the prediction method of the median fragmentation in bench blasting of layered rock mass. Combined with the bench blasting productive test of Changjiu (Shenshan) limestone mine, the largest sand aggregate production mine in the world, the correctness of the theoretical results is verified. The test results demonstrate that in a vertically inclined rock bench, the degree of rock fragmentation intensifies in the horizontal direction, and the overall fragmentation effect can be optimized by adjusting the blasting hole spacing; the blasting fragmentation prediction method proposed in the paper can accurately predict the median fragmentation of layered rock, which provides a novel method for predicting the effects of bench blasting. Highlights: The prediction method for the median fragmentation of layered bench rock mass blasting is obtained The quantitative relationship between the post-expansion cranny ratio and the median fragmentation of bench blasting is theoretically derived The distribution law of microcracks in bench rock mass is simulated by discrete fracture network model. The internal force distribution characteristics are analyzed by continuous medium discrete element method The propagation law and rock breaking process of microcracks and layered cracks in bench blasting are studied At the same time, the correctness of the prediction method is verified by the field test and production of Changjiu (Shenshan) limestone mine [ABSTRACT FROM AUTHOR]

Up to the beginning of the twenty-first century, most of quasi-brittle structures, in particular the ones composed by concrete or masonry frames and walls, were designed and built according to codes that totally ignored fracture mechanics theory. The structural load capacity predicted by strength-based theories, such as plastic analysis and limit analysis, do not exhibit size-effect. Within the framework of fracture mechanics theory, this paper deals with the analysis of the effect of non proportional loadings on the strength reduction with the structural scaling. In particular, this study investigates the size-effect of quasi-brittle materials subjected to self-weight. Although omnipresent, gravity-load is often considered negligible in most studies in the field of fracture mechanics. This assumption is obviously not valid for large structures and in particular for geometries in which the dead load is a major driving force leading to fracture and structural failure. In this study, an analytical formulation expressing the relation between the strength-reduction and the structural scaling and accounting for self-weight, was derived for both notched and unnotched bodies. More specifically, a closed form expression for size and self-weight effects was first derived for notched specimens from equivalent linear elastic fracture mechanics. Next, equivalent linear elastic fracture mechanics theory being not applicable to unnotched bodies, a cohesive model formulation was considered. Particularly, the cohesive size effect curve and the generalized cohesive size effect curves, originally obtained via cohesive crack analysis for weightless bodies with sharp and blunt/unnotched notches, respectively, were equipped of an additional term to account for the effect of gravity. All the resulting formulas were compared with the predictions of numerical simulation resulting from the adoption of the Lattice Discrete Particle Model. The results point out that the analytical formulas match very well the results of the numerical model for both notched and unnotched samples. Furthermore, the analytical formulas predict a vertical asymptote for increasing size, in the typical double-logarithm strength versus structural size representation. The asymptote corresponds to a characteristic size at which the structure fails under its own weight. For large structural sizes approaching this characteristic size, the newly developed formulas deviate significantly from previously proposed size-effect formulas. The practical relevance of this finding was demonstrated by analyzing size and self-weight effect for several quasi-brittle materials such as concrete, wood, limestone and carbon composites. Most importantly, the proposed formulas were applied to the failure of semi-circular masonry arches under spreading supports with different slenderness ratios. Results show that analytical formulas well predict numerical simulations and, above all, that for vaulted structures it is mandatory accounting for the effect of self-weight. [ABSTRACT FROM AUTHOR]

This paper aims to study the Mode-I penny-shaped crack problem of an infinite body of one-dimensional hexagonal piezoelectric quasicrystal. The problem is transformed into a mixed-boundary value problem in the context of electro-elasticity of quasicrystals, and the corresponding integro-differential equations are analytically solved. Two extreme cases of electrically impermeable and permeable crack surface are considered. By virtue of the generalized potential theory method, the three-dimensional complete analytical solutions of three-dimensional crack problems under symmetric concentrated and uniform loads are expressed in terms of elementary functions. Important parameters in fracture mechanics are explicitly derived, such as crack surface displacements, the distributions of generalized stresses at the crack tip and the corresponding generalized stress intensity factors. The validity of the proposed solutions and the coupling effect of phonon-phason-electric fields are investigagted through numerical examples. [ABSTRACT FROM AUTHOR]

This paper presents a forensic numerical study on hydro-fracturing at three locations within an excavation in a clayey till underlain by an aquifer in Ontario, Canada. The pioneering forensic studies were based on continuum mechanics using finite element method (FEM) combined with an effective medium approach, which did not explicitly simulate the physical process of fracture propagation. This has overestimated the size of the venting holes (i.e., model aperture approximately 8 m, observed approximately 0.1 m), hindering accurate assessment of the venting locations at the excavation base. For this reason, a coupled hydro-mechanical XFEM analysis, which explicitly models fracture propagation, was performed in this study to revisit the case history from the perspective of fracture mechanics. Parametric study is also performed to investigate the influence of flow rate on the direction of the fracture propagation, and thus location of venting holes. It is shown that the coupled hydro-mechanical XFEM analysis offers better predictions than previous FEM analysis for both, locations and sizes of the three observed venting holes. The parametric study reveals that an increase in the flow rate from 5 to 10 L/min (which is within the reported range) leads to a wider and less curved fracture, altering the predictions of the venting locations at the excavation base by around 8 m. This is because an increasing flow rate causes wider aperture and higher shear stress near the fracture tip, which intensifies the re-orientation of maximum principle stress that facilitates the re-direction of the propagating fractures. [ABSTRACT FROM AUTHOR]

Fracture of viscoelastic materials is considered to be a complex phenomenon due to their highly rate sensitive behavior. In this context, we are interested in the quasi-static response of a viscoelastic solid subjected to damage. This paper outlines a new incremental variational based approach and its computational implementation to model damage in viscoelastic solids. The variational formalism allows us to embed the local constitutive equations into a global incremental potential, the minimization of which provides the solution to the mechanical problem. Softening damage models in their local form are known to result in spurious mesh-sensitive results, and hence, non-locality (or regularization) has to be introduced to preserve the mathematical relevance of the problem. In the present paper, we consider two different regularization techniques for the viscoelastic damage model: a particular phase-field and a lip-field approach. The model parameters are calibrated to obtain some equivalence between both these approaches. Numerical results are then presented for the bidimensional case and both these approaches compare well. Numerical results also demonstrate the ability of the model to qualitatively represent the typical rate-dependent behaviour of the viscoelastic materials. Besides, the novelty of the present work also lies in the use of lip-field approach for the first time in a viscoelastic context. [ABSTRACT FROM AUTHOR]

Mixed-mode fracture is a common failure phenomenon of materials, while its experiment requires at least a material test machine, test materials and special machining procedures. In this paper, a simple but effective mixed-mode fracture experiment using office paper is proposed, so one can easily conduct the mixed-mode fracture experiment and understand its fracture criteria such as the maximum tensile stress (MTS) criterion. [ABSTRACT FROM AUTHOR]

Abstract  In this study, a simplified Acoustic Emission (AE) equipment, in essence an AE signal conditioner and a USB (Universal Serial Bus) data acquisition system, is used to study what happens in paper structures during mechanical loading. By the use of such equipment, some parameters that can be extracted are e.g. the stress and strain at onset of AE, the stress and strain at the onset of rapid AE defined as some numerical factor (larger then one) times the initial emission rate, the emission rate at the first stage of loading and the stress and strain at final failure i.e. when the specimen loses its load carrying ability.In this study however, the interest is focused on one particular parameter i.e. the elastic strain energy density W c at onset of AE. This is a parameter with a clear physical meaning and in this study, the correlation between this parameter and a fracture toughness measure, is investigated.The conclusion is that when nine different paper materials (with a large span regarding properties) are considered, there is a correlation (however not linear) between these two parameters. [ABSTRACT FROM AUTHOR]

Plant fibers have enormous potential for enhancing concrete's impact resistance due to their exceptional toughness and ductility. Nevertheless, theoretical studies on the impact properties of plant fiber-reinforced concrete (PFRC) are still relatively few. Thus, it is crucial to investigate from a theoretical standpoint how plant fibers affect concrete's impact properties. Based on the modified Griffith fracture theory, this study established the relationship between plant fiber type and strain hysteresis factor. In order to simulate the damage process of PFRC, a micro-spring system was used. Based on this, a dynamic constitutive model considering the influence of plant fibers was proposed by combining the methods of damage mechanics and fracture theory. Parameter fitting and inverse analysis were used to validate the accuracy of the proposed model. Additionally, the mechanical behavior of four types of PFRC (Jute, Flax, Ramie and Sisal Fiber Concrete) under impact loading was simulated by the finite element method (FEM) using the proposed model. The results show that the predictions of the proposed model maintain a good of fit R2 more than 0.98 with the experimental results. The parameter fitting and inversion results also show that the proposed model has a good prediction. Simulation results show that sisal fiber-reinforced concrete exhibited the best performance among the four types of PFRC under identical loading conditions, offering more significant advantages for engineering applications. Theoretical and simulation studies on the impact properties of PFRC were conducted in this paper, and the findings are believed to provide a valuable methodological basis for the engineering application of using less expensive plant fibers to enhance concrete impact properties. [ABSTRACT FROM AUTHOR]

In reservoir simulation, it is important to understand the mechanical behaviour of fractured rocks and the effect of shear and tensile displacements of fractures on their aperture. Tensile opening directly enhances the fracture aperture, whereas shear of a preexisting rough-walled fracture creates aperture changes dependent on the local stress state. Since fracture dilatation increases reservoir permeability, both processes must be included in a realistic and consistent manner into the mechanical reservoir simulation model. Here, we use the extended finite volume method (XFVM) to conduct flow and geomechanics simulations. In XFVM, fractures are embedded in a poroelastic matrix and are modelled with discontinuous basis functions. On each fracture segment the tractions and compressive forces are calculated, and one extra degree of freedom is added for both the shear and tensile displacement. In this particular XFVM implementation we assume that linear elasticity and steady state fluid pressure adequately constrain the effective stress. In this paper, shear dilation is not calculated a posteriori, but it enters the equations such that aperture changes directly affect the stress state. This is accomplished by adding shear dilation to the displacement gradients and therefore ascertains a consistent representation in the stress-strain relations and force balances. We illustrate and discuss the influence of this extra term in two simple test cases and in a realistic layer-restricted two-dimensional fracture network subjected to plausible in situ stress and pore pressure conditions. [ABSTRACT FROM AUTHOR]

It is crucial to propose an accurate fatigue life prediction method to ensure the structural integrity and operational reliability of engineering components in real-world service conditions. This paper considers how the uncertainty of fatigue failure in composite materials under variable amplitude loading conditions affects material fatigue life. It proposes an improved method to predict the residual fatigue life of a composite material by converting the number of loading cycles under different loading sequences. Firstly, the method suggests that the number of loading cycles for the same composite material, under variable amplitude loading conditions and at different stress levels, conforms to the assumptions of the Weibull cumulative distribution and the principle of probabilistic consistency. Using this assumption, a transformation model is established for the number of cyclic loading cycles in composite materials under variable amplitude loading conditions. Specifically, the model can convert the number of loading cycles under various loading sequences into an equivalent number of cycles under a uniform loading condition. Next, the residual fatigue life of the specimen at the final stress level was determined by analyzing fatigue test data under variable amplitude loading conditions. Finally, the proposed method is validated and compared using fatigue test data from the literature, which includes composites tested under two and three variable amplitude loading conditions. Validation results indicate that the proposed method for predicting residual fatigue life offers more accurate predictions, with all predicted life factors falling within ± 1.2 life factors. Additionally, compared to other existing models for predicting residual life, the proposed method effectively captures the impact of randomness and uncertainty in the fatigue failure process of composite materials using probabilistic statistical theory. This offers a more valuable reference for predicting fatigue life under variable amplitude load. [ABSTRACT FROM AUTHOR]

The investigation of fatigue failure in polymeric materials subjected to cyclic loading holds significant importance across diverse engineering applications. Numerous variables influence material behavior, encompassing material-related factors such as composition, molecular weight, orientation, and additives, as well as external factors like applied stress magnitude (stress amplitude, dynamic stress frequency and mean stress), and operating temperature. This paper presents an experimental exploration into the impact of loading parameters—mean stress, stress amplitude, and dynamic stress frequency—on the failure modes of two thermoplastic materials: high-density polyethylene (HDPE) and polyvinyl chloride (PVC). The study begins with an assessment of the mechanical and physical properties of the materials, followed by the design and manufacturing of a specialized uniaxial fatigue test rig. Tensile–tensile fatigue tests incorporating positive mean stress are conducted, evaluating the influence of altering stress amplitude and frequency on fatigue life and failure mode. The outcomes reveal that HDPE primarily experiences thermal and creep failure modes, with a lack of observed fatigue failure. Conversely, PVC specimens manifest three distinct failure modes: ductile, creep, and fatigue, with the type of failure contingent upon loading parameters. These findings offer significant insights into the various fatigue failure modes and contribute to an enhanced comprehension of the intricate interplay between loading dynamics and failure modes in polymeric materials. [ABSTRACT FROM AUTHOR]

Brittle material Mode I fracture may be characterized by the double cleavage drilled compression test. For linear elastic materials, the critical energy release rate, or fracture toughness, can be estimated simply using the linear elastic fracture mechanics. For other types of constitutive behavior, the material parameter has to be determined with numerical fracture modeling. In this paper, we have used two approaches, the phase-field damage model and the cohesive elements, in order to estimate the critical energy release rate of an elastoplastic material. Firstly, we assessed the numerical models and discussed their parameters by comparison of available data from double cleavage drilled compression experimental tests run on a silica glass. Both phase-field damage and cohesive zone models were able to reproduce fracture initiation at the observed macroscopic stress for the linear elastic material. However, the material toughness could not be predicted by the phase-field approach due to the result dependence on the model regularization parameter. Secondly, an elastoplastic methyl methacrylate polymer was submitted to the compression test in our lab. Both models were then extended for elastic-perfectly plastic materials. Crack initiation was obtained at the observed macroscopic strain for similar critical energy release rate ranges for both approaches, providing good confidence in the estimated material toughness. [ABSTRACT FROM AUTHOR]

Crossbow-related injuries resulting in serious and mortal consequences have increased in recent years, and although significant research exists for both injury and fatality on the human body, limited data exists on the lethality of the bolt and the failure modes of protective materials. This paper concerns itself with the experimental validation of four differing crossbow bolt geometries, their effects on material failure and potentially lethality. During this study, four different types of crossbow bolt geometries were tested against two protection mechanisms that differed in mechanical properties, geometry, mass and size. The results show that at 67 ms−1, ogive, field and combo tips do not provide lethal effect at 10-m range, whilst a broadhead tip will perforate both the para-aramid and a reinforced area of polycarbonate material consisting of two 3-mm plates at 63–66 ms−1. Although perforation was apparent with a more honed tip geometry, the chain mail layering within the para-aramid protection and friction caused by polycarbonate petalling on the arrow body reduced the velocity enough to demonstrate the materials under test are effective at withstanding crossbow attack. Subsequent calculation of the maximum velocity that arrows could achieve if fired from the crossbow within this study shows results close to the overmatch value of each material and therefore a requirement to advance the knowledge in this field to influence the development of more effective armour protection mechanisms. [ABSTRACT FROM AUTHOR]

Creep failure of hierarchical materials is investigated by simulation of beam network models. Such models are idealizations of hierarchical fibrous materials where bundles of load-carrying fibers are held together by multi-level (hierarchical) cross-links. Failure of individual beams is assumed to be governed by stress-assisted thermal activation over local barriers, and beam stresses are computed by solving the global balance equations of linear and angular momentum across the network. Disorder is mimicked by a statistical distribution of barrier heights. Both initially intact samples and samples containing side notches of various length are considered. Samples with hierarchical cross-link patterns are simulated alongside reference samples where cross-links are placed randomly without hierarchical organization. The results demonstrate that hierarchical patterning may strongly increase creep strain and creep lifetime while reducing the lifetime variation. This is due to the fact that hierarchical patterning induces a failure mode that differs significantly from the standard scenario of failure by nucleation and growth of a critical crack. Characterization of this failure mode demonstrates good agreement between the present simulations and experimental findings on hierarchically patterned paper sheets. [ABSTRACT FROM AUTHOR]

A theoretical basis for evaluating safety and stability of underground engineering is to study changes in rock strength and failure. In the process of coal mining, the failure mechanical properties in coal present a complex change principle that, under various in situ stresses and in a hydrological environment, results in material failure because of its unstable state being driven by energy. Therefore, by establishing a relationship between energy change and deformation process of coal failure, it would contribute to reflecting the essential characteristics relating to coal strength and failure. In order to explore the mechanics and energy evolution characteristics of water-bearing coal under the triaxial compression process, triaxial compression mechanical experiments of coal under different water contents and confining pressures have been conducted in this paper, whose effects relating to different confining pressures, including water content on changes in total strain energy, elastic strain energy, and the dissipation energy of coal have been analysed. As coal is a porous medium containing a pore and fissure structure, the volume change law relating to coal during the deformation and failure process is characterised by porosity, consequently, a damage constitutive model for coal was established from the perspective of energy dissipation based on statistical damage theory. It is believed that this model could better reflect the deformation behaviour of coal under triaxial compression, in which the relationship between damage evolution characteristics and energy dissipation changes has been reflected in the model. Further, the methods of determining the model's parameters have been proposed to verify the rationality of the established model. Finally, the influence of confining pressure and water content on the brittleness in coal has been discussed from the position of energy evolution. Highlights: Triaxial compression experiments were conducted on coal specimens to investigate the effects of water content and confining pressure on energy evolution. Based on statistical damage theory, the constitutive model that combined energy dissipation and coal failure was established. The effects of water content and confining pressure on the coal brittleness were discussed from the aspect of energy evolution. [ABSTRACT FROM AUTHOR]

The article discusses the paper "Simulation of Porosity by Microballoon Dispersion in Epoxy and Urethane: Mechanical Measurements and Models," by M.A. El-Hadek and H.V. Tippur. The aim of the paper is to experimentally determine Young's modulus, tensile strength, and fracture toughness of syntactic foams, and the provision of micromechanical models for predicting such material parameters. El-Hadek and Tippur claim they could successfully estimate the effective stiffness by neglecting the particle wall thickness in the homogenization procedure. The particle wall thickness is one of the most important parameters influencing the effective mechanical properties of syntactic foams.

The first part of a comprehensive review of the literature on wood published in the Journal of Materials Science since its inception in 1966 is presented. Papers are reviewed by subject ranging from the determination of the microfibril angle in the wood cell wall through to the evaluation of fatigue life. The role of moisture content in determining mechanical properties of wood is explored and mechanical properties are reported including creep, fatigue and fracture. It is concluded that JMS has played a key role in disseminating state of the art literature on new developments in the understanding of the structure-related properties of wood. [ABSTRACT FROM AUTHOR]

The following response to the discussion of the above mentioned paper is divided into two parts: (1) a response to the issue of our comparison of the ‘apparent period of specimen oscillation’, t, and the natural vibration period of a cracked specimen,T, and (2) a verification of the applicability of our model to ‘short time-to-fracture’ tests, which Rokach has questioned, due to a lack of knowledge of Hopkinson bar techniques. [ABSTRACT FROM AUTHOR]

Fault slip will directly affect the technical performance of solid expandable tubular (SET). However, there are few researches on the mechanical behavior of shear failure when SET crosses the slip fault. In response to the above problems, this paper builds a three-dimensional dynamic tube-rock system numerical model that considers nonlinear frictional contact and fault slip based on the SET material constitutive model, Coulomb friction, and shale layer rock. The purpose is to reveal the influence of fault slip on the mechanical behavior of SET and to analyze the risk point of SET failure. The results of the study show that as the amount of fault slip increases, the maximum value of the Mises stress of SET appears in the direction perpendicular to the amount of fault slip (90°). With the increase in the number of faults, the shear stress distribution on the cross section hardly changes, and the shear stress distribution on the fault plane presents a "8" shape. When the included angle is 60°, the shear stress on the shear plane is the largest and the shear distribution is the most uneven. The research results of this paper provide a theoretical basis for the slip shear of SET. [ABSTRACT FROM AUTHOR]

Cemented granular materials (CGMs) are multi-phase materials consisting of a skeleton of solid particles and a cement phase completely or partially filling the voids among the particles. Although CGMs have been increasingly used in geotechnical applications, their mechanical behaviour has not been clearly understood yet. Peridynamics is a numerical method that can accurately simulate the damage/failure process in solid materials only based on inherent material properties. However, it has limited capability for modelling complicated materials like CGMs. In this paper, a novel peridynamics model is developed to remove the restrictions and investigate the mechanical behaviours of CGMs with different volume fractions of cementitious phase. The irregularly shaped particles are created based on X-ray scanning of rock particles. Key mechanical phenomena including inter-particle frictional contact, distribution of cement bonds and cement clogs between particles are considered in the model. The simulation results in this paper are supported by experimental tests, showing that the mechanical parameters of CGMs vary significantly with change in the cement volume fraction. For a small cement volume fraction up to 2%, pure cement bonds control the overall behaviour of CGMs. From 2 to 12%, the bulk behaviour of cement clogs affects CGMs, and after 12%, cement bonds and clogs with defects control the behaviour of CGMs. This peridynamics model is capable of modelling the unconfined compressive strength and Young's modulus of CGMs under a large variation of cement ratios. [ABSTRACT FROM AUTHOR]

The dynamics of a “peeling front” or an elastic line is studied under creep (constant load) conditions. Our experiments show in most cases an exponential dependence of the creep velocity on the inverse force (mass) applied. In particular, the dynamical correlations of the avalanche activity are discussed here. We compare various avalanche statistics to those of a line with non-local elasticity, and study various measures of the experimental avalanche-avalanche and temporal correlations such as the autocorrelation function of the released energy and aftershock activity. From all these we conclude, that internal avalanche dynamics seems to follow “line depinning”-like behavior, in rough agreement with the depinning model. Meanwhile, the correlations reveal subtle complications not implied by depinning theory. Moreover, we also show how these results can be understood from a geophysical point of view. [ABSTRACT FROM AUTHOR]

The mechanical properties of the crack tip are vital for material safety evaluation. The weld material of welded joints is prone to work hardening during processing and installation, which changes the material mechanical properties and seriously affects the safety assessment of nuclear power welded joints. At the same time, nuclear power pipelines will creep under high temperatures and cause changes in the mechanical field at the crack tip. This paper obtains the mechanical properties of nickel-based alloy 182 in a nuclear power water environment. With the help of ABAQUS software, the change rules of the crack tip stress field and creep field under different hardening degrees are analyzed, and then the influence on crack tip creep and crack propagation rate is analyzed. Results show that increasing pre-hardening will increase the Mises stress around the crack tip, and the creep around the crack tip is expressed under pre-deformation, indicating that pre-hardening can accelerate the cracking of stress corrosion to a certain extent. Research has shown that the work hardening induced by the pre-deformation has an important influence on the creep rate at the crack tip, and the high creep zone is mainly concentrated in the direction of crack propagation. Under a certain work hardening rate, the crack growth will be accumulated. [ABSTRACT FROM AUTHOR]

This article discusses the possibilities of estimation of safe sizes of integrity defects on the basis of risk criteria. Such defects occur at all stages of the lifetime of structures. In most cases the estimation of their hazard and determination of allowable sizes attract attention when the defects can lead to brittle or quasi-brittle fractures. In this case, the models of linear and nonlinear destruction mechanics are applied, when the defects are considered as internal elliptical or surface semielliptical cracks. The stochastic variety of shapes, sizes, locations, and orientations of defects has a significant influence on the failure mechanisms. Therefore, the probabilistic problem of estimating allowable sizes of defects according to the criteria of risk of failure is relevant. This paper examines a general approach to estimation of the hazards of defects according to risk criteria. Two formulations of the probabilistic problem of risk estimation are presented: on the basis of single-parameter and two-parameter failure criteria. The risk function is used as the calculated characteristic, represented as the probability of failure according to a given criterion. An equation of the risk function based on single-parameter failure criteria is presented. The main focus is on the probabilistic model based on the two-parameter Morozov failure criterion. This criterion provides a wide range of opportunities for analyzing various failure mechanisms with variations in the size of defects. An expression for the risk function based on the family of two-dimensional Lu–Bhattacharya probability distributions of Weibull type is derived. It is shown that correlations between failure mechanisms can significantly influence the probabilities of failure and, consequently, the allowable size of defects. [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]

Internal subsurface cracks in continuously cast slabs can lead to catastrophic failure of the material when it is subjected to further rolling or shaping. The interplay of multiple factors contributes to the formation of these cracks, making it occasionally challenging to accurately assess slab quality based solely on surface appearance. This paper presents an in-depth exploration of the internal quality of slabs, that aimed to identify the critical parameters responsible for initiating and propagating these cracks. The investigation employs a range of methodologies, including macro- and micro-metallographic analysis, thermo-mechanical simulations, that aid in characterizing defects and understanding material vulnerability. To prevent such failures in cast products, the study also proposes optimized operational parameters. [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]

This paper contains a comparison of the flexural strength results of two different samples. Both samples were made using additive manufacturing, from ABS (acrylonitrile butadiene styrene) material with the inclusion of an unknown filler designated as X. They also have in common that they are divided into two groups, the first group with a material infill of 100 %, and the second group with a material infill of 50 %. In order to determine that the material infill really affects the flexural strength results, the samples are differentiated by their shape. The first sample consists of tiles, while the second sample consists of pipes. The samples are printed vertically, which doesn't change the material's inherent mechanical qualities but does change the amount of infill and the strength of the bond between the layers. The difference between the values of the stress at failure of the material in the tile group is approximately 20 %, while in the tube group this difference is approximately 6 %. We can conclude that filling with the material in the range of 50 to 100 % during the production of pipes has an insignificant effect on bending strength, while this is not the case with plate samples. Based on this, there definitely is a significant influence of geometry when determining flexural strength. The idea for further research should be to measure the influence of samples treated with acetone on their flexural strength. [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]

The influence of tool wear on cutting force in turning glass–ceramics was studied, and a theoretical model of turning force considering tool wear was established in this paper. Firstly, the crack propagation behavior and the form of energy dissipation were analyzed during chip formation, and the model of the force due to chip formation was established based on the fracture mechanics of brittle solids and the principle of energy transfer. Secondly, the mechanical model caused by the flank wear was established by analyzing the microscopic wear mechanism of the tool and the source of friction. Finally, the theoretical model of turning force considering the tool wear was established. The model is only applicable to brittle removal mode. Two different cutting tools were selected to carry out the experiment of turning fluorophlogopite glass–ceramics. The relationship between cutting force and tool wear was discussed, and the accuracy of the model was verified. The results showed that the tool wear has a direct impact on the cutting force, and the theoretical model of cutting force established is in good agreement with the experimental data in this paper. [ABSTRACT FROM AUTHOR]

The paper presents the dynamic impact properties of laser-sintered polyamide PA2200 in accordance with the building orientation. The idea of deTermining the impact properties in relation to building orientation lays on orientation-property dependence founded in our previous studies of tensile, bending and fracture mechanics testing. The specimens were manufactured under the same energy density and temperature conditions, at four orientations, as described in the paper content. The experimental investigation was carried out on a pendulum impact testing machine to deTermine the impact energy and strength according to the building orientation. Brittle fracture was observed for all specimens, independent of building orientation, and a similar behavior was also observed in the elastic zone of deflection. However, impact strength and impact energy are influenced by orientation. [ABSTRACT FROM AUTHOR]

Residual stress is an important factor that affects the properties of cold spray coatings. The study performed 2D single-, 3D single-, and 3D multiple-particle finite element simulations based on the Eulerian method, and hole drilling measurements to study residual stress in cold-sprayed copper coatings. The study examined how the basic modeling parameters affect residual stress in the 2D system. It found that the mesh size, substrate dimension, and simulation duration change the residual stress; while material failure does not have much effect because failure is localized. It also found that thermal softening, which occurs when the initial temperature and/or plastic deformation increase, helps to reduce the residual stress. In addition, the residual stress along the axisymmetric axis of the particle changes from being compressive at first to being compressive-tensile-compressive along the through-depth thickness direction with the interfacial stress being tensile that mainly originates from friction shear of the interfacial layers. For the 3D single-particle simulations, the average residual stress to the through-depth thickness shows tension to compression transition and is similar to the 2D cases. For the 3D multiple-particle simulations, the residual stresses in the coatings/substrate are all compressive because of the repeated and strong impact of the particles, which agree with the experimental measurements. The study also found that the compressive stresses decrease when the coating thickness increases because of more plastic deformation-induced thermal softening. This paper clarifies the effects of Eulerian-based finite element parameters on simulating residual stress in cold spray and will serve as a valuable reference for future studies. [ABSTRACT FROM AUTHOR]

To investigate the effect of initial cracks on the fatigue performance of high-strength bolts for high-speed train brake discs, the fatigue crack propagation behavior of high-strength bolts under the coupling action of preload and dynamic fatigue load was investigated experimentally and numerically based on the theory of linear elastic fracture mechanics. Firstly, fatigue tests of high-strength bolts with initial crack defects were carried out, and then a three-dimensional accurate numerical model with the hexahedral mesh for a bolt-nut was established by MATLAB, and the fatigue crack propagation behaviors were investigated using ABAQUS-FRANC3D interactive technology. In this paper, the effects of the initial crack state, the bolt preload, the axial excitation load, and the friction coefficient of the screw pair on crack propagation life were emphatically studied, and the simulated crack propagation trajectory and crack propagation life agreed well with the experimental results. The findings indicated that 0°-oriented cracks beginning at the maximum principal stress were predicted to have the shortest fatigue life. The crack propagation life was sensitive to the initial crack size, the coefficient of initial crack geometry, and the bolt preload, but not to the friction coefficient of the screw pair. Furthermore, when evaluating the effect of fatigue load on crack propagation, the load ratio, the mean load, and the load range should all be considered. [ABSTRACT FROM AUTHOR]

This paper proposes a new idea and method which is to use configuration mechanics to describe the evolution of complex microstructures and multiple defects such as discontinuity, heterogeneity and anisotropy in the borehole rock under the coupling of mechanics and chemistry. It is used to deal with the evolution of complex microstructures and multiple defects in the borehole rock that are difficult to deal with in the traditional fracture mechanics and damage mechanics of the continuum theory. The two-dimensional/three-dimensional M-integral is numerically calculated using the domain integration method, and the material failure criterion based on configuration force and conservation integral is used to calculate the shale lining fracture pressure. The results show that the calculation results can better predict the fracture pressure. It shows that the established multi-field coupling borehole rupture pressure model based on the M-integral of configuration mechanics can provide a theoretical reference for the complex formation stability under multi-field coupling and the wellbore stability control during field operations. [ABSTRACT FROM AUTHOR]

In recent years, interest in the effect of positive temperatures on rock faces has increased, as evidenced by the extensive literature on the subject. The subsurface rock masses of rock slopes are submitted to uncontrollable natural temperature cycles which cause deformation, displacement, opening and closing of discontinuities and can lead to surface failure or more important rockfalls. In this paper we offer a review of the publications on this theme focusing on in situ observations and measurements. Measurements are described and analysed considering conditions of temperature and insolation, displacements, strains, focusing on two French sites (Les Rochers de Valabres and La Roque-Gageac). Mechanical analysis is then performed. The impact of temperature variation is studied from basic assumptions to much more complex ones. Thermoelasticity is first assessed, and analytical computation is suggested, fracture mechanism and fatigue are also considered. Finally, we outline some challenges to be addressed in the coming years. Highlights: The article reviews the accumulated knowledge on the effect of positive temperature changes on slope stability. Excluding the effect of water freezing and thawing. The different types of measurements are reviewed considering surface and in-depth measurements of temperature, displacements, fracture opening, and strain. Simple thermo-elastic analysis, alongside solutions from fracture mechanics are proposed. A focus is proposed on 2 French sites to illustrate interpretations. The conclusion summarizes the points of consensus, the aspects that are still under discussion among authors or should be more debated and open to pending challenges for the next years. [ABSTRACT FROM AUTHOR]

Severe plastic deformation (SPD) processes offer the possibility of improving the mechanical properties of metallic materials by grain refinement. However, this great potential has so far mostly been applied on a laboratory scale or on small series. Equal-Channel Angular Pressing (ECAP) also enables to integrate the advantages in industrial processes with large output—so far, mainly for bars or thick plates. In this paper, we investigate the ECAP process for sheet metal. Preliminary investigations have shown that cracks form on the surface when aluminum AA5083 sheets are processed. To solve this problem, we determined the Johnson–Cook fracture criterion for the material and modeled the process numerically. The simulation was carried out with the superposition of a backpressure and subsequently implemented and validated experimentally. The semi-finished sheet metal products from the ECAP investigation were then mechanically characterized with microhardness measurements and tensile tests. In addition, the microstructure was investigated with Electron Back Scatter Diffraction (EBSD). Even comparatively small amounts of backpressure (10 MPa) already result in a significant suppression of the crack formation in the numerical and experimental investigations. The microhardness measurements indicate a more homogeneous strain distribution for a sufficient level of applied backpressure which enables the processing of crack-free sheets in multiple ECAP passes. As with ECAP of bulk materials, tensile tests on the processed sheets show a reduced elongation to failure (− 73%) but a significantly increased yield strength (+ 157%) compared to the initial condition of the material. Distinct substructures are found in the EBSD measurements and explain this behavior. The findings provide the basis for using ECAP on an application-oriented scale and demonstrate an advanced manufacturing method for the production of high-strength aluminum sheets. [ABSTRACT FROM AUTHOR]

This paper presents a novel framework combining the state-based peridynamics (SBPD) with the extended finite element method (XFEM) for crack propagation in two-dimensional solids. Numerical examination is conducted fulfilling both the quasi-static and time-dependent loading conditions. The computational domain is partitioned into two regions: (a) SPBD region: the vicinity of crack tips and potential region where the crack is likely to propagate, and (b) XFEM region: the area behind the crack tip and the rest of the body. The salient features of the developed framework include: (a) avoiding requirement of a priori knowledge of enrichment functions like the conventional XFEM; (b) without fracture criteria for crack propagation; (c) no restriction on the value of Poisson's ratio like the bond-based peridynamics; and (d) higher computational efficiency than the pure peridynamics. The efficiency and accuracy of the proposed framework are systematically demonstrated through benchmark examples involving quasi-static crack growth and dynamic crack branching problems. [ABSTRACT FROM AUTHOR]

The article presents discussion on analysis of the dynamic responses for a pre-cracked three-point bend specimen. Theoretical part presents a very simple model of the impact specimen. As it was shown in the discussion, accuracy of this model and its applicability for the short time to fracture tests is questionable. An example that demonstrates a weak accuracy of the model is also presented. Most controversial section of the discussion is comparison between the vibration period of the cracked specimen and the apparent period of specimen oscillation.

Railway turnouts are essential in the train traffic route management for modern railways. Despite significant devotion to railway turnout research, one of their most common failures has not been thoroughly investigated, which is a fatigue over the turnout crossing nose. At the crossings, wheel-rail discontinuity imparts high-frequency high-magnitude forces, which are the source of fatigue failure over the crossing nose. In this study, a novel approach built on "Peridynamics" (PD) has been developed to obtain new insights into the fatigue cracks. A recent approach using "crack on mid-plane" has also been employed in this study to enhance the limited capability of Peridynamics. This paper is the world's first to investigate fatigue failures over a crossing nose from fracture mechanics perspective. This paper also introduces a novel adaptive time-mapping method as an alternative to earlier time-mapping methods for fatigue models proposed in the open literature. The new model has been verified against both Finite Element Method and experimental data. It reveals that our new approach can simulate fatigue damage, particularly in mode I crack propagation. The study has provided important insights on the fatigue crack development, which is not possible before by existing Peridynamics fatigue model. The new approach on the basis of "adaptive time-mapping" and "crack on mid-plane" is demonstrated to be effective and efficient in PD simulations. [ABSTRACT FROM AUTHOR]

Abrasive waterjet peening is a preferable alternative to traditional shot peening which can be used for surface strengthening of structural components. The fatigue crack behavior of 2024 aluminum alloy specimen treated by abrasive waterjet peening was investigated in this paper. The jet flow field was analyzed firstly by adopting CFD. The peening process was then modeled to calculate the residual stress distribution on the target surface, and the results were verified by experiments. The numerical model for the fatigue test was then established for evaluating the crack growth characteristics in the specimen with residual compression induced by the peening. The results indicated that the effective stress intensity factor range and the crack propagation rate are reduced due to the peening-induced residual stress. The effective stress intensity factor range reaches 13.1 MPa·m0.5, and the crack propagation rate reaches 1.7 × 10–7 mm/cycle at the depth of maximum residual stress, respectively. The crack closure coefficient decreases with an increase of the shot peening intensity, while increases with an increase of the stress ratio. [ABSTRACT FROM AUTHOR]

Background: Digital image correlation (DIC) with microscopes has become an important experimental tool in fracture mechanics to study local effects such as the plastic zone, crack closure, crack deflection or crack branching. High-resolution light microscopes provide 2D images but the field of view is limited to a small area and very sensitive to its alignment. A flexible positioning system is therefore needed to collect such DIC data during the entire fatigue crack growth process. Objective: We present in our paper a new experimental setup for local high-resolution 2D DIC measurements at any location and at any time during fatigue crack growth experiments with a non-fixed DIC microscopy system. Methods: We use a robot to move the 2D DIC microscope to any location on the surface of the specimen. Optical and tactile methods automatically adjust the system and ensure highest image quality as well as accurate alignment. In addition, an advanced repositioning method reduces out-of-plane motion effects. Results: The robot is able to achieve a repositioning accuracy of less than 0.06 mm in vector space, resulting in very low Von Mises strain scattering of 0.07 to 0.09% in the DIC evaluation. The system minimizes systematic errors caused by translation and rotational deviations. Effects such as crack deflection, crack branching or the plastic zone of a fatigue crack can be investigated with a field of view of 10.2 x 6.4 mm2. Conclusions: The robot supported DIC system generates up to 8000 high-quality DIC images in an experiment that enables the application of digital evaluation algorithms. Redundant information create confidence in the results as all revealed effects are comprehensible. This increases the information content of a single fatigue crack growth test and accelerates knowledge generation. [ABSTRACT FROM AUTHOR]

In a recent contribution, Shrimali and Lopez-Pamies (Extreme Mech Lett 58, 101944, 2023a) have shown that the Griffith criticality condition that governs crack growth in viscoelastic elastomers can be reduced—from its ordinary form involving a historically elusive loading-history-dependent critical tearing energy T c —to a fundamental form that involves exclusively the intrinsic fracture energy G c of the elastomer. The purpose of this paper is to make use of this fundamental form to explain one of the most telltale fracture tests for viscoelastic elastomers, the so-called delayed fracture test. [ABSTRACT FROM AUTHOR]

When plates with edge cracks in the rolling process is straightened by cyclic tensile and compressive stress, the tip of edge crack always accompanied by stress concentration, which leads to crack propagation. In this paper, damage parameters are imported into the plate straightening model based on determining the GTN damage parameters of magnesium alloy materials by inverse finite element calibration method, the influence of different straightening process schemes and prefabricated V-shaped crack geometry on crack growth is analyzed through the way of the combination of simulation and straightening experiment. The results show that the peak values of equivalent stress and equivalent strain under each straightening roll appear at the crack tip. The value of longitudinal stress and equivalent stain decrease with the distance to crack tip becomes larger. The peak value of longitudinal stress appears when the crack circumferential angle is about 100°, and the crack tip is easy to form crack propagation; when the plate passes roll 2 and roll 4, the equivalent stress and strain concentration at the crack tip are most obvious; when the reduction reaches a certain degree, the void volume fraction (VVF) reaches the VVF of the material breaking; with the increase of the entrance reduction, the number of VVF at the crack tip which reaches the material fracture increases, and the length of crack propagation increases; the stress concentration at the tip of V-shaped crack with large length–width ratio is obvious, and the VVF is more likely to reach the VVF at the time of material fracture, crack initiates and propagates easily. [ABSTRACT FROM AUTHOR]

This paper is a continuation of two recent publications on crack growth in viscoelastic media. It provides further theoretical results for large strains that enable prediction of crack opening displacement for comparison with experimental data in the region of the singularity. In order to achieve good agreement with experiment it was necessary to account for far-field viscoelasticity. Additionally, it is found that with large deformation throughout the singularity, the deformation consists of simple shearing and stretching normal to the crack plane. Thus, there is no significant displacement parallel to the crack plane; such simplicity exists for materials that stiffen or soften at high strains if the stress obeys a power law in strain at high strains. This finding means that, despite the frame-dependence of the theory, there is no local rotation in the singularity to affect the stress. [ABSTRACT FROM AUTHOR]

The paper presents the results of verification calculation on the crack resistance of a high-pressure cylinder taken out of service due to the detection of crack-like defect. The critical dimensions of cracks, at which brittle failure of the cylinder can occur, and the safety coefficient of the cylinder in terms of crack resistance, are determined. Based on the provisions of linear fracture mechanics, back in the XIX century it was established that the causes of the failure of high-strength materials are crack-like defects of the operational or the technological origin. The causes of these defects can be operational impacts (vibration, cyclic loading and aggressive environments) and design and technological factors (welding, rolling, heat treatment, etc.). One of the actual problems of theoretical and experimental research of reliability of structural materials in industrial equipment is to study influence of the internal and the surface semi-elliptic cracks on safety of their operation. [ABSTRACT FROM AUTHOR]

Damage mechanics models exhibit favorable properties such as the intrinsic influence of stress triaxiality on damage evolution and the prediction of crack initiation as well as propagation leading to structural failure. However, their application requires advanced expertise hindering the transfer of these models into industrial practice, especially since the parameter calibration is a key obstacle. In this paper, a simplified procedure is proposed for a non-local extension of the Gurson–Tvergaard–Needleman model (GTN), which is a highly accepted model for ductile failure of metals. The procedure is iteration free and requires experimental input data from only two standardized tests. The parameters are determined using look-up diagrams created on the basis of systematic simulations and made available for different material behavior covering the majority of ductile metals. Benchmark tests for three different steels are conducted to evaluate the robustness of the proposed procedure. The reliability of the GTN model is validated for all investigated materials. [ABSTRACT FROM AUTHOR]