Damage Evolution Behavior Research Articles

Damage evolution behavior of tunnel lining concrete with non‐through crack under single‐sided sulfate attack

AbstractIn order to study the dynamic damage evolution law of tunnel‐lining concrete with non‐through crack under single‐side sulfate attack, a 420‐day sulfate attack concrete test was conducted and the uniaxial compression and acoustic emission (AE) tests were carried out on each corrosion time. The test results showed that the compressive strength of each group can be divided into rising stage and falling stage, and the existence of non‐through crack reduced the compressive strength of concrete specimens and accelerated the corrosion of concrete specimens by sulfate. AE ringing count can be divided into compaction stage, elastic stage, yield stage, and post‐peak stage; the variation patterns of AE varied at different stages. Sulfate attack caused the yield point of concrete to advance. With the increase of corrosion time, microcracks increased gradually, cement mortar was consumed continuously, concrete spalling occurred, the proportion of AE cumulative ringing count Stage II decreased gradually, and the proportion of Stage III increased. Non‐through crack changed the energy storage of Stages II and III and reduced the AE activity of concrete after corrosion. The deeper the crack was, the smaller the average cumulative ringing count was and the lower the AE activity was. AE cumulative ringing counts can be used to characterize the damage evolution of corroded concrete.

Effect of connection modes on seismic responses of a diaphragm wall-subway station system subjected to mainshock-aftershock sequences

Most existing seismic behavior analyses of underground structures simply consider a single earthquake. Meanwhile, the diaphragm wall, as an enclosure structure, is regarded as a security reserve and is always ignored in current studies. Herein, the characteristics of a diaphragm wall-subway station system with different connection modes under earthquake sequences were investigated using numerical simulation. The damage degree of the structural component was calculated through quantitative analysis of the tensile damage picture. The seismic damage level of the station structure was evaluated to characterize the damage transition effect induced by the aftershock according to the inter-story drift angle. Moreover, an empirical model for predicting the inter-story drift angle with respect to different peak accelerations was proposed. The research results indicate that the effect of the connection mode between the sidewall and the diaphragm wall on the damage evolution and deformation behavior of the station structure is significant. Compared with that of the compound wall structure, the seismic damage to the sidewall of the composite wall structure is much less severe, but the slabs become more vulnerable and suffer more severe damage. The accumulative damage triggered by aftershocks aggravates the extent of structural damage and even leads to damage transition. The conclusions illustrated in this paper contribute to a better understanding of the seismic resistance design of diaphragm wall-subway station systems under earthquake sequences.

Experimental Characterization and Phase-Field Damage Modeling of Ductile Fracture in AISI 316L

(1) Modeling and characterization of ductile fracture in metals is still a challenging task in the field of computational mechanics. Experimental testing offers specific responses in the form of crack-mouth (CMOD) and crack-tip (CTOD) opening displacement related to applied force or crack growth. The main aim of this paper is to develop a phase-field-based Finite Element Method (FEM) implementation for modeling of ductile fracture in stainless steel. (2) A Phase-Field Damage Model (PFDM) was coupled with von Mises plasticity and a work-densities-based criterion was employed, with a threshold to propose a new relationship between critical fracture energy and critical total strain value. In addition, the threshold value of potential internal energy—which controls damage evolution—is defined from the critical fracture energy. (3) The material properties of AISI 316L steel are determined by a uniaxial tensile test and the Compact Tension (CT) specimen crack growth test. The PFDM model is validated against the experimental results obtained in the fracture toughness characterization test, with the simulation results being within 8% of the experimental measurements. (4) The novel implementation offers the possibility for better control of the ductile behavior of metallic materials and damage initiation, evolution, and propagation.

Damage evolution of coal with a strong bursting liability and 3D measurement method for elastic deformation energy distribution

When coal with a strong bursting liability is disturbed by a load, catastrophic instability disasters and rockbursts can easily occur. Loaded coal with a strong bursting liability undergoes complex damage evolution and failure behavior due to the intricate interplay among loads, gangue, fractures, and the coal matrix. Intuitively quantifying and characterizing the complex discontinuous structural features, deformation fields, and energy fields within coal is the foundation for the scientific analysis and prevention of disaster mechanisms caused by rockbursts. Therefore, studying the distribution and evolutionary processes of deformation fields and energy fields caused by the evolution of discontinuous structures within coal is highly important for the prevention and control of coal mine rockburst disasters and the protection of coal mine safety during mining operations. In this study, a series of X-ray computed tomography (X-CT) tests were conducted on coal specimens with varying gangue contents under uniaxial compressive loading. The X-CT images clearly illustrated the internal damage evolution of coal with a strong bursting liability, revealing fracture propagation, shear bands, and localized failure under varying loading conditions. Image segmentation was employed to quantitatively analyze the development of damage in coal with a strong bursting liability, revealing the influence patterns of gangue content on the prepeak deformation localization and strength of coal. Additionally, using digital volume correlation, the 3D volumetric displacement and strain of loaded impact-prone coal were determined based on the changes in natural speckle images. The nonuniform distribution of strain was mainly caused by the nonuniform distribution of gangue and pore fractures at the microscopic scale, which explains the localized deformation in coal materials. Importantly, this study provides new full-field strain tensor data and a novel method for measuring the elastic deformation energy of the 3D deformation and cracking processes of loaded coal.

Effects of strain rate and bedding on shale fracture mechanisms

Anisotropic shale is commonly distributed in nature and undergoes both dynamic compressive and tensile load in geological engineering. In this article, the coupling effects of strain rate and bedding structures on the fracture mechanisms of shale are investigated using a split Hopkinson pressure bar (SHPB) system. The tension–compression comparative study is conducted. The Brazilian disc method is modified, and a unified strain rate measurement method is established to comprehensively analyze shale’s fracture-related properties, including moduli, strength and energy dissipation. The results indicate that the energy dissipated by shale fracture is strongly related to its strength. The strain rate and bedding affect the anisotropic strength and dissipated energy by changing the crack density and crack propagation mode. At low or medium strain rates, the bedding orientation of shale determines the direction of crack propagation. However, at high strain rates, microcracks in different directions are widely activated in the shale, which increases the fracture degree and decreases the difference in fracture toughness between the shale’s matrix and bedding planes. This also leads to a decrease in anisotropy and causes the bedding planes to lose control over the direction of crack propagation. Additionally, the dynamic tensile strength of shale increases faster than the compressive one with the strain rate, leading to a reduction in the proportion of tensile failure under impact load. Based on the experimental findings, a new anisotropic damage constitutive model is developed to characterize the dynamic properties of shale. This model reflects the anisotropic damage evolution behaviors and aligns well with experimental results, offering a theoretical foundation for predicting shale’s dynamic fracture behavior. In addition to shale, the developed experimental methods and theoretical models can also be applied to the fracture analysis of other brittle transversely isotropic materials.

Damage Evolution and Energy Catastrophe Behavior during Quasi-static Loading Process of Rockburst

Rockburst pose a serious hazard to deep underground engineering. The damage evolution and energy transformation of rockburst under quasi-static load are the key to reveal the mechanism of rockburst. Based on the instability theory and stiffness theory, the burst rock and surrounding rock combination specimens are designed in this study. Then a constitutive model for simulating the whole process of rockburst is established by statistical damage of rock. The law of damage deformation and energy evolution during rockburst is revealed, and the key factors affecting rockburst intensity are analyzed. The results indicate that the damage mechanism of rockburst is related to the sudden change of damage before and after the peak stress of the burst rock, and the volume ratio of surrounding rock to burst rock. The evaluation index of rockburst proneness based on energy evolution can reflect the energy conversion and transmission relationship between the surrounding rock and burst rock in the combination system, which is of great significance for the evaluation of rockburst proneness.

Tensile damage evolution and mechanical behaviour of SiCf/SiC mini-composites through 4D in-situ micro-CT and data-driven modelling

Damage evolution of SiCf/SiC ceramic matrix mini-composites (CMMCs) was characterised by using a 4D in-situ micro-computed tomography (CT) tensile test and digital volume correlation (DVC) technique. Additionally, a CT damage data-driven shear lag model was developed to predict its tensile stress-strain response. A 4D in-situ X-ray CT tensile test of a unidirectional SiCf/SiC mini-composite was first carried out. Then two ad-hoc deep-learning image segmentation models were developed to automatically identify its microstructure and damages induced by tension, respectively. Damage evolution was quantitively characterised by visualising the initiation and propagation of matrix cracks in three-dimensions (3D). A two-step approach was employed to evaluate its 3D internal strain distributions at various loading levels, which further revealed strain concentrations and helped establishing the tensile stress-strain response of the CMMCs. It was observed that transverse cracking is the predominant damage mode, and the average crack opening displacement increases with loading. A high-fidelity X-ray CT data-driven shear lag model was developed, incorporating inputs of transverse matrix crack spacing calculated by the 4D in-situ CT test data. The predicted stress-strain response showed a good correlation with the experimental results.

In situ X-ray imaging and numerical modeling of damage accumulation in C/SiC composites at temperatures up to 1200 °C

Carbon fiber reinforced silicon carbide matrix composites (C/SiC) have emerged as key materials for thermal protection systems owing to their high strength-to-weight ratio, high-temperature durability, resistance to oxidation, and outstanding reliability. However, manufacturing defects deteriorate the mechanical response of these composites under extreme thermal-force coupling conditions, prompting significant research attention. This study demonstrates a customized in situ loading device compatible with synchrotron radiation facilities, enabling high spatial and temporal resolution recording of internal material damage evolution and failure behavior under thermal-force coupling conditions. Infrared thermal radiation units in a confocal configuration were used to create ultra-high-temperature environments, offering advantages of compactness, rapid heating, and versatility. In situ tensile tests were conducted on C/SiC samples in a nitrogen atmosphere at both room temperature and 1200 °C. The high-resolution image data demonstrate various failure phenomena, such as matrix cracking and pore linkage. Image-based finite element simulations indicate that the temperature-dependent variation of the failure mechanism is attributable to thermal residual stresses and defect-induced stress concentrations. This work seamlessly integrates extreme mechanical testing methods with in situ observation techniques, providing a comprehensive solution for accurately quantifying crack initiation, pore connection, and failure behavior of C/SiC composites.

Fatigue of Bridge Steel Wire: A Corrosion Pit Evolution Model under the Effects of Wind and Vehicles

To investigate the damage evolution behavior of corroded steel wires under the influence of alternating loads, a damage evolution model for steel wires based on the theory of continuous damage mechanics was established. The damage evolution process at corrosion pits was simulated by using the element birth and death technique in ANSYS 2020R2. Then, a certain cable-stayed bridge was chosen as the research subject, the stress–time data of the sling were computed using a traffic–bridge–wind simulation analysis model, and the influence of corrosion pit distribution on the mechanical properties and fatigue life of wires under an alternating load was discussed. The results show that, in comparison to single-pitted steel wires, double-pits distributed circumferentially across the cross-section of the steel wires lead to more severe stress concentration, accelerating the damage evolution process and significantly reducing the fatigue life of the steel wires. Conversely, the stress concentration caused by double pits distributed along the longitudinal direction of steel wire is similar to that caused by single pits, and it will be even weaker than that caused by single pits with the change in the relative distance of the double pits. Based on the calculation results of the damage evolution model of steel wire, it was found that the corrosion pit crack nucleation life of steel wire under alternating load accounts for nearly 80% of the fatigue life of steel wire, and different corrosion pit distribution modes will significantly affect the fatigue life of steel wire.

Rate-dependent damage sequence interaction model for predicting the mechanical property of in-service aluminum alloy 6005A-T6

Engineering structures and materials will undergo fatigue, aging, and other degradation behaviors during long-term service under the combined influence of complex boundary conditions. These service damages make the materials and structures no longer meet the initial design requirements and pose a potential risk to the service system. This study proposes a material mesoscopic model to decouple the microstructure into a system composed of matrix and void phases. The matrix phase has an invariant constitutive relationship as an ideally undamaged material, and the different evolutionary behaviors of the void phase are described as damage evolution functions and lead to different stress–strain behaviors of the actual material. First, the damage described by different definitions is proposed, and a nonlinear function of damage evolution consistent with the Weibull distribution characteristic of microstructural continuity is derived. Then, an experimental–numerical method is improved to accurately identify the accelerated damage evolution behavior under various strain rates. Finally, the ideally undamaged constitutive of the matrix phase and the damage evolution function of the void phase are established, which can cover the void nucleation, growth, and aggregation process. Besides, the damage sequence interaction model is established in conjunction with the mesoscopic physical mechanism, and the total damage evolution function for materials containing prior service damage in subsequent ductile deformation is achieved by measuring the apparent elastic modulus of the material only. Finally, the ideally undamaged constitutive and damage evolution function are calibrated for aluminum alloy 6005A-T6, commonly used in the car body structure of rail vehicles, and verified with damaged specimens that experienced certain service loads. The material's damage sequence interaction mode is determined, and the rate-dependent residual strength is predicted.

Revealing damage evolution and ablation behavior of SiC/SiC ceramic matrix composites by picosecond laser high-efficiency ablation

The picosecond laser was utilized to fabricate the slanting microholes efficiently on SiC/SiC ceramic matrix composites. The machining damage, material oxidation, and temperature field were mainly analyzed through static and in-situ detections. The damage evolution and ablation behavior of SiC/SiC composites were qualitatively and quantitatively revealed. The results showed that the lowest peak temperature of the slanting microhole was 282.6 °C. The heat accumulation effect and thermal stress that was tensile stress in nature present caused recasts, microcracks, fiber fracture, fiber debonding, and fiber stripping. Fibers and matrix underwent slight oxidation, forming SiO2 recasts through the phase transition. The pulse energy, frequency, and inclination angle regularly affected the quantity, size, and distribution of microcracks, material removal rate (MRR), and hole wall roughness. The maximum MRR was about 2.5 mm3/s, corresponding to the minimum time was 0.9 s. The circularly polarized picosecond laser could process parallel striped laser-induced periodic surface structures (LIPSS) on the hole wall.

Damage evolution and removal behaviors of GaN crystals involved in double-grits grinding

Elucidating the complex interactions between the work material and abrasives during grinding of gallium nitride (GaN) single crystals is an active and challenging research area. In this study, molecular dynamics simulations were performed on double-grits interacted grinding of GaN crystals; and the grinding force, coefficient of friction, stress distribution, plastic damage behaviors, and abrasive damage were systematically investigated. The results demonstrated that the interacted distance in both radial and transverse directions achieved better grinding quality than that in only one direction. The grinding force, grinding induced stress, subsurface damage depth, and abrasive wear increase as the transverse interacted distance increases. However, there was no clear correlation between the interaction distance and the number of atoms in the phase transition and dislocation length. Appropriate interacted distances between abrasives can decrease grinding force, coefficient of friction, grinding induced stress, subsurface damage depth, and abrasive wear during the grinding process. The results of grinding tests combined with cross-sectional transmission electron micrographs validated the simulated damage results, i.e. amorphous atoms, high-pressure phase transition, dislocations, stacking faults, and lattice distortions. The results of this study will deepen our understanding of damage accumulation and material removal resulting from coupling between abrasives during grinding and can be used to develop a feasible approach to the wheel design of ordered abrasives.

Presentation of a new 2D fast and straightforward version for the Lemaitre’s ductile damage model

Damage is an undesirable and progressive process that ultimately leads to complete failure of materials. Obtaining a robust tool to precisely and reliably predict damage evolution behavior in ductile sheet metals is among the most crucial challenges for researchers and engineers. In this paper, first, based on the continuum damage mechanics (CDM) and the original Lemaitre’s ductile damage model, a new 2D fast and straightforward version specialized for the plane stress conditions as well as a novel numerical integration algorithm are fully presented. Additionally, a modified numerical approach, founded on the bisection method is suggested for determining the material-dependent ductile damage parameter of the model. Then, an explicit subroutine is developed and implemented to numerically predict damage evolution behavior in different ductile sheet metals and shapes. Finally, the numerical simulation results of damage initiation, growth, and crack onset are attained and validated. The numerical simulation predicted results reveal that the novel offered version of the Lemaitre’s ductile damage model in conjunction with the enhanced numerical approach is able to more rapidly predict the material-dependent ductile damage parameter and also the evolution of damage in ductile sheet metals under various loading and boundary conditions.

Study on fatigue damage evolution behavior of SLM formed IN 718 alloy

SLM (Selective Laser Melting) Inconel718 alloy has good corrosion resistance, oxidation resistance and fatigue resistance, which is an indispensable and important material in industrial fields such as energy power, aerospace and nuclear power. In this paper, the fatigue damage evolution behavior of SLM Inconel718 alloy under different heat treatment is studied by the MTS fatigue testing machine and DIC (digital image correlation method). The results show that the fatigue evolution of SLM Inconel718 alloy changes slowly in the initial stage of fatigue evolution. When the damage factor reaches the critical value, alloy begins to enter the rapid damage stage. In the steady stage, SLM Inconel718 alloy has small damage accumulation. In the rapid damage stage, the damage degree of SLM Inconel718 alloy increases and the damage accumulates rapidly. The critical damage factor can effectively distinguish these two stages, and the critical damage factor under different heat treatment shows: AT2 > AT1 > AT3.

Complete constitutive model of CFRP including continuous damage in low strain rate compression and temperature generation in high strain rate impact

AbstractThis paper reports a method to construct the complete constitutive model of carbon fiber‐reinforced plastic (CFRP) by distinguishing the strain rate state and modifying the material stiffness. In quasistatic (low strain rate) compression, the initial nonlinear effect caused by the material defects was described by introducing an nonlinear increasing factor. In dynamic (high strain rate) impact, the nonlinear strengthening effect was described by introducing the dynamic amplification factors of stress and strain based on the reference state. Considering the instantaneous temperature rise obtained from the impact work–temperature generation equation and the influence of temperature on modulus and strength, the coupled thermomechanical constitutive models combining the strain rate effect and the temperature effect were established. The user‐defined material subroutines (VUMAT) were developed, and then these constitutive models were verified by finite element analysis (FEA). Finally, the developed material subroutine was applied to predict the impact penetration of CFRP laminates, and the results show that the opening holes, damage and energy dissipation are in good agreement with the reference experiment. This work comprehensively analyzed the construction method of CFRP constitutive models, which would provide a guidance for the coupled thermomechanical behavior under dynamic impact.Highlights An anisotropic continuum mechanical constitutive behavior considering strain rate effect and damage evolution behavior was established. A macroscopic anisotropic constitutive model including the coupled impact temperature generation‐mechanical behavior was established. Combined with the incremental finite element method, the three‐dimensional user‐defined material subroutines (VUMAT) were developed and verified. The thermomechanical impact penetration behaviors of CFRP laminates was predicted, and the stress field, temperature field and failure characteristics were visualized.

Multi-stepped creep constitutive model based on asymptotic damage evolution behavior of sandstone

Multi-stepped creep constitutive model based on asymptotic damage evolution behavior of sandstone

Studies on the life, damage evolution, and crack propagation behaviors of TC18 titanium alloy under repeated impact loading

TC18 titanium alloy has been widely used as the key structure which is often subjected to repeated impacts in service in aerospace engineering. In this study, the repeated impact responses of TC18 were investigated by conducting various repeated drop hammer impact tests. Abundant microscopic characterization technologies were used to reveal the correlation between damage evolution and the impact response. The results show that the average impact fatigue life (Nf¯) of the notched three-point-bend specimen decreases exponentially with the impact energy. Microscopic observation shows that cracks nucleate at the initial 40%∼50% of Nf¯, then propagate steadily during the next 50% to 90% of Nf¯. During the last 10% of Nf¯, the cracks propagate rapidly, resulting in the failure. During crack propagation, the repeated impacts induce complex stress states in the vicinity of cracks, leading to grain refinement, phase transition, and strengthened texture. The phase transition and strengthened texture mechanisms are mainly due to the generation of the platelet-like α subgrains inside the refined grains. The results in this paper are crucial for understanding the microscopic damage and failure mechanism of TC18 under repeated impacts, which helps to establish the damage accumulation-based life prediction model in the future.

An energy-based chemo-thermo-mechanical damage model for early-age concrete

Cracking prediction and control in hydration process of mass concrete and structures has always been a challenging task. In this work, an energy-based chemo-thermo-mechanical damage model for early-age concrete is well established within the framework of thermodynamics and continuum damage mechanics. The evolution laws for the mechanical damage are driven by the work conjugate elastoplastic damage energy release rates to fully represent the microcracks closure-reopening effect, the anisotropy, and the aging effect of concrete relating to the degree of hydration. A formulation fitted from a large number of test data is introduced to simulate the thermal evolution during hydration process, resulting in an excellent approximation of the degree of hydration. When the degree of hydration is 1, the model is degenerated into the classical plastic damage model. The presented model is thus able to simulate the hydration process of early-age concrete and mechanical responses of concrete as well as reinforced concrete structures at any age. The model is implemented by user defined subroutine in Abaqus, in which a sequential coupling method is established. Several benchmark tests are successfully reproduced, indicating that the proposed model is capable of predicting the damage evolution and typical nonlinear behavior of early-age concrete and hardened concrete. The computational efficiency of the model is significantly improved compared to the classical ones due to the introduction of the fitting formulation of the thermal evolution and the sequential coupling method to reduce the nonlinearity of the system. The strategy allows the model to be applied in massive concrete structures during construction and provide valuable prediction as well as guidance for large scale engineering structures.

A multi-scale model from microscopic cracks to macroscopic damage of concrete at elevated temperatures

A multi-scale model is established to describe the relationship between the macroscopic damage evolution and microscopic cracks behaviors of concrete at elevated temperatures. The evolution equation of the ideal microscopic crack system of concrete at elevated temperatures is deduced for construct the model, which can predict the microscopic crack density and macroscopic damage of concrete at elevated temperatures. The multi-scale model fuses some advantages of the traditional microscopic and macroscopic damage models. Finally, multi-scale damage of a concrete block under high temperature is predicted and compared with the corresponding experimental results, which is utilized to support the ability of the developed model. The results show that the developed multi-scale model can be used to evaluate fire damage of concrete structures in macro-scale as well as explain its physical mechanisms in micro-scale.

Damage and deformation behavior of reinforced concrete pipes with varying joints under surface explosion

Reinforced concrete pipes (RCP) are the mainstay of urban water transmission networks. Urban development entails increased potential for blasting activities (such as subway tunneling, excavation, and demolition) as well as the risk of accidental explosions. This paper provides a detailed description of the damage evolution and deformation process of RCP under explosive loads using validated numerical simulation methods. A concise phenomenon-based method is introduced for RCP damage grading. Furthermore, a comparative analysis is conducted on the damage and deformation of RCP resulting from explosions at different locations and with varying weights. At last, this paper especially investigates and explains the impact of four commonly used joint types on the RCP’s response to explosions. The research results help to enhance the understanding of damage evolution and deformation behavior of RCP (or similar structures) induced by explosion, and are also references for protection, repairing and failure identification of segmented structures subjected to explosion.