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In this paper, the desiccation shrinkage and cracking of soils are studied in the framework of the extended finite element method (XFEM). The XFEM is introduced first, then, the results of existing desiccation experiments of soils are introduced and analysed, the parameters of the extended finite element model are determined from the results of the desiccation experiments. The finite element scheme used to describe the desiccation shrinkage of soils which obtained from the hydro-mechanical formulation of the continuous medium is proposed. Then, a 3D hydro-mechanical model for the desiccation experiments is established with ABAQUS via the subroutine of UMAT and the XFEM tools in ABAQUS. The proposed numerical approach is validated by reproducing the desiccation experiments. It was shown that the numerical simulations fit well the experimental measurements. The numerical results, on the other hand, provide some useful information about both desiccation shrinkage and cracking of soils. The proposed approach simple and highly efficient and constitutes a promising approach in studying the crack initiation and propagation in soils induced by the desiccation shrinkage. [ABSTRACT FROM AUTHOR]

Casing failure in hydraulic fracturing can lead to the leakage of fracturing fluid into the aquifer, resulting in groundwater contamination. To prevent such contamination, a universal assessment model applicable for most scenarios is necessary. However, the complexity of the stratum, parameter uncertainty, and computational challenges pose obstacles to risk assessment. In this study, we address these challenges by considering the uncertainty of hydrological parameters and the heterogeneity of the stratum in the development of a new conceptual model. Numerical simulations were conducted to concretize the conceptual model and derive data. Sensitivity analysis were performed to investigate the key factors influencing groundwater contamination, which are vertical hydraulic conductivity and porosity of the overburden layers, porosity of the high-permeability interlayers, and fracturing fluid leak location. Additionally, a Support Vector Machine (SVM) was selected to be developed as an alternative approach. Quasi-Monte Carlo simulations using Halton sequence were carried out to obtain probability distributions. In predicting the flux of contaminants in the aquifer and the time required for the fracturing fluid to reach the aquifer, our results demonstrated strong correlations in the SVM model, with correlation coefficients of 0.9984 and 0.9701, and low Root Mean Square Errors of 4.07 × 10–2 mg and 3.121 days. In a ten-year risk assessment, the probability of contaminant flux in the aquifer being less than 1.875 mg was 100%, indicating a low risk, and the average time for fracturing fluid to reach the aquifer was 1545 days. These findings provide valuable insights into the potential environmental impact of fracturing fluid contaminants and can inform the development of regulations and best practices for fracturing operations. [ABSTRACT FROM AUTHOR]

Summary: The objective of the present paper is to present a numerical study on the penetration performance of concrete targets with 2 different water contents. Numerical analysis has been performed by using the finite element code Abaqus/Explicit, in which a coupled elastoplastic damage model has been developed for saturated/unsaturated concrete under a wide range of confining pressures. The performance of proposed model has been firstly verified by simulating the triaxial compression tests and penetration tests realized with saturated/dry concretes. Comparisons of available experimental results and numerical simulations show that the proposed model is able to reproduce satisfactorily the mechanical behavior of saturated and dry concretes. A higher failure stress and a more important pores closing are generally obtained in dry concrete samples with respect to saturated ones. Furthermore, the main observed patterns of penetration test realized with saturated concrete targets are also satisfactorily simulated by the numerical results. Therefore, the proposed model is used to numerically predict the penetration performance of dry concrete target, and the penetration performance of dry/saturated concrete target is discussed. We observe that in dry concrete target, the penetration of projectile is strongly declined, and a smaller damage zone is created. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of hydraulic conditions on structural vulnerability of concrete structures subjected to near‐field detonations or impacts. [ABSTRACT FROM AUTHOR]

This paper is focused on the numerical modelling of long-term stability of the rock joint, which has been performed using the extended finite element method. An elastoplastic damage model is developed for the rock matrix around the joints, while a specially developed interface model has been used for the joints. The proposed model for rock joint is based on the assumptions made on the aperture scale. The simplest exponential degradation law has been proposed for both the residual friction angle and the aperture erosion, for taking into consideration the time effects. The proposed model is then used to simulate some direct shear tests realised on the intact and eroded rock interfaces. Comparison of available test results shows that the proposed model is capable to predict satisfactorily the time-dependant degradation caused by either the residual friction angle decrease and/or interface roughness erosion. Therefore, the time effects is numerically analysed via a parametric study on an academic example. The numerical results show that the degradation caused by the decrease in residual friction angle and erosion on the joint surface reduce dramatically joint’s resistance. [ABSTRACT FROM AUTHOR]

To enhance the understanding of interaction between elastoplastic damage behavior of concrete and penetration behavior of projectile, this study develops an elastoplastic damage model for concrete with an emphasis on the pressure dependence of volume change. Numerical analysis is performed by using the finite element code Abaqus/Explicite, in which the proposed model is incorporated. In order to understand the effect of concrete volume change and concrete damage on the penetration behavior of projectile, a series of parametric studies are carried out. Finally, some projectile penetration tests are simulated by using the proposed model. The numerical results reproduce satisfactorily the main patterns observed in the projectile penetration tests. The interpretation and discussion of numerical results help the engineers and ballisticians complete their knowledge on the vulnerability of concrete structures. [ABSTRACT FROM AUTHOR]

Abstract: This paper includes a presentation of a numerical model for the description of the behavior of unsaturated sandy soils under cyclic loading with particular attention for liquefaction. The model is developed within the framework of the theory of Biot and the formulation of Coussy. It is also based on laboratory observations. The formulation leads to a simplified model, which allows also to deal with saturated soils. The cyclic elastoplastic constitutive model “MODSOL” is used to describe the cyclic behavior of the soil. The paper presents an analysis of the influence of the soil saturation on the response of a sandy soil to both monotonic and cyclic undrained loading paths. It shows that the decrease in the saturation degree of a sandy soil leads to an important increase in their resistance to liquefaction. [Copyright &y& Elsevier]

The present work addresses the question of the quantitative prediction of the biaxial response of polymer–clay nanocomposites experiencing strain-induced crystallization. Polyethylene terephthalate is taken as material model to represent the continuous amorphous phase of nanocomposites. A continuum-based micromechanical model is developed to predict the combined effect of strain-induced phase transformation and nanocomposite structural characteristics on the overall elastic-viscoplastic response. Comparisons with available experimental data are presented to illustrate the capabilities of the model in relation to various loading parameters in terms of loading path, loading rate and loading temperature. The model is used to provide a better understanding of the relationship between nanocomposite structural characteristics, phase transformation, intrinsic properties and loading parameters. [ABSTRACT FROM AUTHOR]

In this paper, a micromechanics-based constitutive representation of the deformation-induced phase transformation in polyethylene terephthalate is proposed and verified under biaxial loading paths. The model, formulated within the Eshelby inclusion theory and the micromechanics framework, considers the material system as a two-phase medium, in which the active interactions between the continuous amorphous phase and the discrete newly formed crystalline domains are explicitly considered. The Duvaut–Lions viscoplastic approach is employed in order to introduce the rate-dependency of the yielding behavior. The model parameters are identified from uniaxial data in terms of stress–strain curves and crystallization kinetics at two different strain rates and two different temperatures above glass transition temperature. Then, it is shown that the model predictions are in good agreement with available experimental results under equal biaxial and constant width conditions. The role of the crystallization on the intrinsic properties is emphasized thanks to the model considering the different loading parameters in terms of mechanical path, strain rate and temperature. [ABSTRACT FROM AUTHOR]

Facing the contradiction between increasing maintenance demand and limited financial, as well as smaller social and environmental impacts, the optimisation of bridge maintenance strategies should be carried out. In this paper, the assessment model of four objectives, including the safety performance, economic, social and environmental impacts, in sustainability criteria are proposed. Moreover, a systematic optimisation framework of maintenance strategy of deteriorating bridges considering sustainability criteria and a novel decision-making method are developed, based on fuzzy analytic hierarchy process (FAHP) and a decision-making algorithm based on linear programming techniques for multidimensional analysis of preference (LINMAP). The case analysis results verify the effectiveness and superiority of the previous optimisation framework, and also show that the final optimal strategy obtained by the proposed decision-making algorithm can reflect the will of experts well. Compare with the essential maintenance, the implementation of preventive maintenance is more conducive to realise the sustainable development of the deteriorating bridges. The sensitivity analysis results show that the monetary discount rate has a greater impact on the life cycle maintenance cost, which is mainly controlled by the total social cost, while the direct maintenance cost only accounts for a small part. [ABSTRACT FROM AUTHOR]

Concrete shrinkage and creep significantly affect the serviceability of bridges, especially long-span bridges. To investigate the long-term shrinkage and creep behaviors of low-shrinkage and low-creep C60 high-performance concrete (hereinafter referred to as LSLC HPC C60), 76 LSLC HPC C60 specimens are designed and subjected to shrinkage and creep tests for 270 days. The results indicate that the LSLC HPC C60 exhibits a similar trend in shrinkage and creep development as ordinary C60 concrete but with smaller creep and shrinkage values. New parameters for the two commonly used creep models are recommended based on experimental data. By comparing the measured data, it is determined that the parameter-recommended creep models are more suitable for predicting the creep performance of the LSLC HPC C60. A finite-element model of a long-span bridge is established, and the recommended models are imported into the bridge model. The multidecade deflections of the main span of the bridge are analyzed considering different creep models. The calculated results indicate that the parameter-recommended creep models can be used to predict the long-term deflections of long-span bridges with the LSLC HPC C60. [ABSTRACT FROM AUTHOR]

• A precise & efficient framework is proposed to obtain tunnel response under faulting. • Damage level classifications for tunnel lining under faulting are established. • Damage behavior of tunnel lining under strike-slip faulting is highlighted. This paper presents a novel numerical framework that can simulate the mechanical response and damage characteristics of mountain tunnels under faulting more precisely and efficiently. Both the submodeling and two-stage models are adopted in the framework. The submodeling technique is used to obtain a precise simulation of tunnel-fault interaction while ensuring computational efficiency. The two-stage models can acquire accurate initial stress of the tunnel lining and simulate the tunnel-rock interaction during fault movement, which can also achieve the transition from static to dynamic analysis. The computational efficiency can be improved by about 73 % via the proposed numerical framework compared to the conventional numerical analysis when keeping the same mesh sizes. Moreover, overall lining damage indices and cross-sectional ovalization are introduced to quantitatively evaluate the respective damage and deformation of the tunnel lining cross-section, and damage level classifications for tunnel lining under faulting are established. Parametric sensitivity analyses are performed to investigate key factors affecting the mechanical damage behavior of mountain tunnels under strike-slip faulting, including fault dislocation, fault zone width, and the tunnel-fault intersection angle. The increasing fault dislocation causes larger tunnel-rock interaction around the fault plane, making the damage and deformation of tunnel lining around the fault plane more severe. The fault zone width has a significant impact on the damage and deformation range of tunnel lining. The tunnel-fault intersection angle contributes great influence on the magnitude and range of tunnel lining damage and deformation. The tunnel lining would suffer relatively severe damage and deformation when the two fault blocks move away from each other along the tunnel axial. [ABSTRACT FROM AUTHOR]

• A peridynamic hydrogen embrittlement model is proposed. • The limitation of Poisson's ratio of existing peridynamic hydrogen embrittlement model is solved. • The hydrogen-assisted crack propagations of mode I and mixture mode are simulated. Hydrogen embrittlement is an important metal failure mechanism that affects the large-scale application of hydrogen energy. And developing an effective numerical model is vital for understanding and preventing hydrogen-assisted crack propagation. This paper proposes a peridynamic hydrogen embrittlement model based on the two-parameter model of bond-based peridynamics, where the limitation of Poisson's ratio is relieved. The bond damage criterion that considers the hydrogen embrittlement mechanism is applied. Both the hydrogen diffusion and the hydrogen embrittlement phenomenon are simulated. The efficiency of the proposed peridynamic hydrogen embrittlement model is validated through four numerical examples, including the mode I crack propagations and complex crack paths simulations. The numerical results of the proposed peridynamic hydrogen embrittlement model are compared to the results of other numerical models and experiments. And the influences from hydrogen diffusion time steps and grain boundary diffusion coefficients on hydrogen-assisted crack propagation are investigated. The numerical results show that more diffusion time steps and larger grain boundary diffusion coefficients lead to faster hydrogen diffusion and faster crack propagation. [ABSTRACT FROM AUTHOR]

This study investigates strand corrosion-induced concrete cracking under various prestress experimentally and analytically. Experimental data on the critical time of cover cracking, crack width and corrosion loss obtained from the accelerated corrosion test are presented and discussed. The expansion ratio of strand corrosion products is estimated based on the infrared spectroscopy and thermal gravimetry. An analytical model, incorporating the coupled effects of prestress and strand corrosion, is proposed to predict the global process of concrete cracking from initiation to propagation. Strand rust-expansion ratio and the residual stiffness of cracked concrete are also included in the model. Results show that prestress can accelerate the corrosion-induced cracking process. By varying prestress from 0 to 75% strand tensile strength, the critical time of cover cracking decreases 22% and the crack propagation rate increases 9%. It is found that the proposed model is accurate in predicting corrosion-induced crack width in prestressed concrete beams. [ABSTRACT FROM AUTHOR]

To investigate the strength and failure characteristics of silty mudstone using different stress paths, silt-like mudstone specimens were subjected to triaxial unloading tests. The results indicate the following. (1) When subjected to equivalent initial deviator stress levels and differing confining pressures, the peak stress, residual stress, and elastic modulus, exhibited during unloading, increased concordantly with greater initial confining pressure. Both the peak strain and residual strain increased with rising initial confining pressure. The increase in peak strain and residual strain initially decelerated, then noticeably increased, before ultimately decreasing again. Additionally, the unloading failure time and strain rate demonstrated a negative correlation as the confining pressure increased. (2) Under different initial deviatoric stress conditions, the peak stress, residual stress, and residual strain, under unloading confining pressure conditions, decreased as the initial deviatoric stress levels elevated. Conversely, the peak strain and elastic modulus initially increased, then decreased under increasing initial deviatoric stress conditions. The unloading failure time and strain rate were both observed to decrease as the initial deviatoric stress levels increased. (3) Utilizing the Mohr stress circle enabled the characterization of the shear strength variation in the specimens during the unloading process. The cohesion and internal friction angle remained relatively consistent across the different unloading stress paths appraised, with cohesion being greater in path I versus path II, whereas the internal friction angle exhibited an inverse relationship. (4) The specimen failed during unloading due to lateral expansion caused by unloading confining pressure and collapse failure. The failure fracture surfaces predominantly manifested shear failure morphologies. [ABSTRACT FROM AUTHOR]

The stability and safety of rock mass in underground constructions are influenced by the damage processes of cracks evolution caused by the excavation under coupled hydro-mechanical loading conditions. In this paper, to understand the crack development and damage evolution of sandstone under different seepage conditions, a series of triaxial compression tests with acoustic emission under different water pressures (5, 10, 15 MPa) are carried out. The stress-strain behavior, crack stress thresholds, failure mode, AE characteristics and micromechanical mechanisms are analyzed and discussed. The experimental results demonstrate that the crack stress thresholds and the mechanical property of studied sandstone decrease with the increase of water pressure. Moreover, the water pressure has an important influence on and deformation behavior of sandstone, for instance, the elastic modulus and deformation modulus decreased when the water pressure increased. Based on the result of accumulated ring counts, the damage evolution of sandstone gradually increased with increasing water pressure. Finally, the micro-structural evolution under the coupling effects of water pressure and applied stress is discussed. The obtained results can be used to identify the initiation and propagation of studied sandstone in the engineering applications. [ABSTRACT FROM AUTHOR]

During the drying process, an initially saturated clay deforms mainly due to the loss of water. It causes clay shrinkage that represents one of the fundamental reasons of cracking by desiccation. It is of great interest to understand the desiccation process in such complex soils. However, the main point is that many properties of the material, such as water content distribution, displacement, strain and stress fields, remain difficult to reach by experimental approach only. Numerical simulations may help estimate these variables, and reinforce in a significant way the experimental measurements. The proposed method of analysis allows to understand more deeply the process of drying in clays including shrinkage, crack initiation and finally, crack network development. This research, combining numerical simulations and laboratory tests allows to go further in investigating the drying phenomenon in remolded and initially saturated kaolinitic clay. [ABSTRACT FROM AUTHOR]

Crushing of rockfill grains is one of the most important issues in the stability study of rockfill dams/embankments. In engineering applications, crushing characteristics of a rockfill grain depend strongly on its number of contact points with neighboring grains. The present work aims to propose a breakage criterion including the effects of coordination number, which refers to the increase of grain strength with the redistribution of stress towards hydrostatic stress conditions due to the continual crushing of neighboring grains. In order to analyze the influence of coordination number on grain crushing, single-particle crushing tests with different coordination numbers are first simulated by a bonded particle model using the discrete-element method (DEM). The mechanical confinement effects of neighboring grains are investigated by installing rigid walls around crushable agglomerates. One observes that the failure pattern and strength of agglomerates are significantly affected by the coordination number. The grain strength generally increases with increasing coordination number. Based on the results obtained at the grain scale, a new breakage criterion is proposed for rockfill materials. The proposed criterion is then embedded in a population balance model in DEM. The oedometer tests with three different grain sizes are simulated using the proposed criterion. In order to avoid the unrealistic mechanical response and reduce the energy accumulation in the particle spawning, a new numerical procedure is adopted in the simulations. The simulated stress–strain curve, normal compression line, and particle size distribution are in agreement with the experimental results. Comparison between the proposed criterion and some previous criteria illustrates the merits of the new criterion. The micro-responses of the samples, including the evolution of average coordination number and average particle stress, are also discussed. Discrete-element modeling and micromechanical analysis will enhance the understanding of crushing and deformation behaviors of rockfill materials. Highlights: The influence of coordination number on the failure pattern and crushing strength of rockfill grains is investigated at the grain scale. A new breakage criterion is proposed for the crushing of rockfill grains with the consideration of coordination number effects. A new numerical procedure is adopted to avoid the unrealistic mechanical response in the particle spawning. By simulating the oedometer tests with three different grain sizes, the crushing characteristics of rockfill materials are studied at the structure scale. Micro-mechanical analysis and discrete-element modeling will enhance the understanding of the crushing and deformation behaviors of rockfill materials. [ABSTRACT FROM AUTHOR]

To better understand the microstructure parameters controlling grain crushing and how the microstructure evolution influences the crushing characteristics of rockfill particles, the emphasis of the present study focuses on the size effects on the crushing strength of rockfill particles, with special attention to internal flaws. Single‐particle crushing tests are performed on rockfill particles with four different size fractions. By combining these results with the experimental results from the literature, the suitability of the Weibull model to describe the size effects on the breakage strength of rock grains is discussed. To understand why larger grains possess lower strength, a bonded particle model (BPM) is established in YADE to simulate the particle crushing tests. Model parameters are calibrated against the obtained force–displacement curve. The failure and deformation behaviors of studied rockfill particles are satisfactorily reproduced by the numerical simulation. The size effects are then studied using the agglomerates with different flaw characteristics (e.g., sizes, numbers, volume ratios, distributions, and locations). Numerical results exhibit that for the studied rockfill particles, when the ratio of flaw size to agglomerate size is less than 0.186, the flaw volume ratio is the key factor for size effects, and the breakage strength of particles is slightly related to the flaw size. In contrast, the breakage strength of particles depends not only on the flaw volume ratio but also on the flaw distribution/location when the flaw size is large. Microscopic analysis and DEM modeling can improve the understanding of crushing and deformation behaviors of rockfill particles. [ABSTRACT FROM AUTHOR]

Particle crushing is a fundamental issue in the analysis of the deformation and failure behaviour of rockfill materials. The impact of morphology on the crushing behaviour of granite particles is investigated via a series of in-situ X-ray micro-CT tests and DEM simulations. Single-particle crushing tests are performed on rock particles of three different sizes. During mechanical loading, four in-situ CT scans are performed on each grain using an innovative loading apparatus. The CT test images reveal that the shape of the particle and its heterogeneous structure are crucial factors in determining failure patterns. Additionally, various shape indexes of rock particles change progressively and tend to stabilize, while their fragments follow a fractal distribution, seemingly independent of their initial size. Based on CT images, numerical particles with realistic shapes and internal flaws are generated using a proposed numerical method. It is observed that an increase in elongation index EI or flatness index FI results in a decrease in characteristic strength σ0\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\sigma _0$$\end{document} and an increase in Weibull modulus m. [ABSTRACT FROM AUTHOR]

The present paper focuses on the hydro-mechanical behaviour of concrete under high confining pressures. By using the poromechanics approach, an elastoplastic model is adopted to describe the mechanical behaviour of concrete under different saturation conditions and high confining pressures. A hydrostatic compression test with the measurement of interstitial pore pressure is firstly used to identify the model's parameter. After that, three quasi-oedometric tests with different water contents are simulated. The obtained numerical results exhibit that the mechanical behaviour of concrete is strongly coupled with its hydraulic responses. For instance: the saturation kinetics is accelerated by the plastic deformation related to pore collapse and volumetric compaction. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of interstitial pore pressure on the vulnerability of concrete structures subjected to near-field detonations or impacts. • Fully coupled hydro-mechanical behaviour of concrete under high confining pressure is analysed. • Hydraulic responses of concrete under high confining pressure are simulated. • Two plastic mechanisms observed in triaxial stress state are influenced by the presence of pore water. [ABSTRACT FROM AUTHOR]

[Display omitted] • In line with the idea of three-dimensional reconstruction technology of CT, a kind of numerical computed tomography method of engineering rock mass is proposed. • Numerical computed tomography method can apparently display the spatial distribution morphology of damage and failure area of rock mass. • Numerical computed tomography method can effectively reveal the intrinsic connection of evolution and quantification of rock mass damage and failure. • Numerical computed tomography method is not limited by the engineering scale effect, and has satisfactory applicability and engineering values. By and large, the traditional CT technology cannot involve the important problems of intrinsic damage identification and reconstruction of large-scale engineering rock mass. In the light of the numerical simulation technology, the digital image processing technology and the three-dimensional reconstruction technology, a kind of numerical computed tomography method is proposed. On the basis of numerical simulation, the external program of the characteristic variable of rock mass damage and failure is called to generate the cloud map model of rock mass damage and failure. In addition, the sequence layered profile images are created by automatically cutting the cloud map model via the self-complied program, as well as adopting the digital image processing technology for batch cropping, batch gray-scale and binarization processing. Eventually, the three-dimensional reconstruction technology is employed to reconstruct the spatial distribution morphology of the internal damage and failure of rock mass. At that point, the proposed method is applied to apparently exhibit the evolution morphology of spatial distribution of the Rm 417 tunnel failure area, and effectively reveal the intrinsic connection of the Rm 417 tunnel failure, such as the location, evolution path and morphology. Consequently, the validity and reliability of the numerical computed tomography method are verified, which has satisfactory applicability and applied values. [ABSTRACT FROM AUTHOR]

Coupled heat and moisture transfer has a severe influence on building envelop durability. This phenomenon has more concerns as the rapid development of new moisture buffering materials. In this paper, a detailed description of hollow concrete block filled with compressed straw bricks is presented. In order to reveal heat and moisture coupling mechanism of the multilayer energy-saving wall, a series of tests were developed based on our designed controllable coupled heat and moisture test. The experiments were divided into 3 groups according to directions of heat and moisture transfer and the variations of boundary conditions. The temperature and humidity profiles within the wall thickness through two different directions are monitored during the test. The experimental results highlight the important influence of temperature and relative humidity gradient on the hygrothermal properties of the multilayer wall. It also illustrates that filling compressed straw bricks into hollow concrete block can hinder heat transfer and improve moisture buffering performance of multilayer wall. Based on our developed model, a piece of software (HMCT 1.0) to simulate the hygrothermal performance in multilayer wall was proposed for deep understanding of the experimental results. A good agreement was found between simulation results and tested values. [ABSTRACT FROM AUTHOR]

• Fatigue crack growth rate was determined by measuring fracture stripe width. • Characterization parameters of fatigue crack propagation and critical fracture was proposed. • A numerical fatigue crack propagation model was established. • Parametric analysis considering initial pit depth and stress amplitude was performed. High-strength steel wires are widely used in large-span bridges. Fatigue damage of steel wires is becoming more and more prominent under adverse environment and repeated load. This paper performed the fatigue crack growth rate tests of high strength steel wires under different stress ratios. The striated fracture morphology was obtained by stepwise fatigue loading method. The fatigue crack growth rate of steel wire was determined by measuring fracture stripe width by optical microscope. The experimental curves of fatigue crack growth rate versus stress intensity factor range under various stress ratios were obtained. The fracture morphology of steel wires after fatigue was observed by scanning electron microscopy. The characterization parameters of fatigue crack growth and critical fracture required for numerical simulation were obtained based on experimental results and statistical method. Following that, a numerical fatigue crack propagation model was established combined with ABAQUS and FRANC3D. The numerical model was validated by experimental observations in the present study and open literature. A parametric analysis method considering initial pit depth and stress amplitude was proposed to evaluate the residual life of steel wires. The results showed that the linear elastic fracture mechanics and numerical simulation-based method can be used to assess the fatigue life of virgin and corroded steel wires. [ABSTRACT FROM AUTHOR]

Time-dependent behavior of subcritical crack growth is one of the main characteristics in rocks. The double-torsion test is commonly used to study the slow crack growth behavior of brittle and quasi-brittle materials. However, double-torsion specimen is difficult to processing, the process of the laboratory test is irreversible, and the current numerical simulation is difficult to consider the time-dependent behavior, and so on. In view of all above problems, an idealized particle model was built, and the crack was identified in this article, based on the theory of particle flow. The numerical model was built using Particle Flow Code in 3 Dimensions, and the macromechanical and micromechanical parameters of the model were calibrated. The process of the macroscopic crack propagation and its evolution were analyzed. The intrinsic relations with the load, the displacement, and the time were established. The results show that the Particle Flow Code in 3 Dimensions can reproduce the time-dependent behavior of subcritical crack growth in double-torsion test. And, the peak and the law of the curves are in good agreement with the laboratory test results. Therefore, the Particle Flow Code in 3 Dimensions numerical simulation can be used as a new effective method to reveal the slow crack growth behavior, to get the relevant parameters such as V, KI, and KIC, and to build the relationship between V and KI. The results of this article will have some reference value for the simulation and application of double-torsion test. [ABSTRACT FROM AUTHOR]