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ATI 718plus is a novel nickel-based high-temperature alloy that delivers superior mechanical properties and higher working temperatures compared to the In718 superalloy. In order to study the machinability of ATI 718plus, a combination of experiments and finite element simulation is used to explore the mechanism of serrated chip formation and the evolution of microstructure under high-speed cutting conditions. Firstly, the Johnson-Cook constitutive model parameters of the ATI 718plus alloy were obtained through a split Hopkinson pressure bar experiment. Secondly, we established a 2D orthogonal cutting model on the AdvantEdge FEM platform by implementing the Johnson-Cook constitutive model and damage model via a custom subroutine. Through the comparison of orthogonal cutting experimental data and finite element simulation results, we verified the accuracy of the finite element model and analyzed the mechanism of serrated chip formation. Finally, combining the multi-physics field distribution of different parameters from the finite element simulation and EBSD test results, it is revealed that the microstructural evolution mechanism during the high-speed cutting of ATI 718plus involves grain lamellar refinement induced by CDRX and grain growth induced by DDRX. The interaction of these two processes results in different forms of microstructures. Under specific cutting parameters, a superfine grain layer with a thickness of 10 µm was formed on the machined surface, which holds great referential significance for our control and improvement of the surface properties in cutting machining. [ABSTRACT FROM AUTHOR]

ABSTRACT Background Aim Methods Results Conclusions As traditional Chinese medicinal materials, E'jiao and cubilose are rich in various bioactive substances with good antioxidant, anti‐inflammatory, and immune‐regulating effects.To obtain the optimal ratio of synergistic effect between E'jiao and cubilose.The antioxidant capacity of E'jiao and cubilose digestive fluid was evaluated in vitro, as well as the intracellular oxidation balance between HSF cells and 3D whole‐skin model induced by H2O2.E'jiao, cubilose, and their different ratios of composites had better scavenging ability against free radicals such as DPPH (2,2‐Diphenyl‐1‐picrylhydrazyl). Using HSF cells induced by H2O2 as an oxidative damage model, it was found that the combination of E'jiao and cubilose in a ratio of 2:3 significantly enhanced the activities of SOD, GSH‐PX, and CAT enzymes compared to the separate treatments of E'jiao and cubilose, as well as other combination ratios. It effectively reduced the accumulation of reactive oxygen species caused by H2O2 in HSF (Human Skin Fibroblast) cells and protected the integrity of the cells. Further analysis using flow cytometry and a 3D full‐thickness skin model revealed that the combination ratio of 2:3 increased the proportion of H2O2‐treated cells in the S%+G2% phase from 19.1% + 7.4%–22.1% + 28.8%, helping oxidatively damaged cells partially recover their proliferative capacity. It also promoted the expression of collagen I and collagen IV in the 3D full‐thickness skin model, with improvement rates reaching 168.00% and 123.68%, respectively.These findings indicate that the combination of E'jiao and cubilose in a ratio of 2:3 exhibits good synergistic effects, enhancing the ability of cells to resist oxidative damage, promoting cellular renewal and metabolism, and improving skin antiwrinkle capacity. [ABSTRACT FROM AUTHOR]

AbstractCarbon fiber-reinforced polymer (CFRP) and engineered cementitious composites (ECC) are commonly used to reinforce structural elements, with proven effectiveness in enhancing the performance of concrete-filled steel tube (CFST) columns as shown in prior experimental studies. However, the complex interaction among the components of the reinforced columns, including CFRP, ECC, the steel tube, and the concrete core, as well as the underlying mechanical mechanisms, remain insufficiently understood. This research aims to fill these gaps by developing a 3D finite element (FE) model of circular CFST short columns reinforced with CFRP grid-reinforced ECC for comprehensive numerical analysis. Sensitivity analyses are conducted to determine the governing parameters in the numerical simulation, including mesh size and critical plasticity parameters for the concrete damage model, such as the ratio of the second stress invariant on the tensile meridian to that on the compressive meridian (Kc), and the dilation angle (ψ) for both the concrete core and ECC. The model also accounts for the effects of concrete confinement provided by the CFRP grid-reinforced ECC layer and the circular steel tube. The accuracy of the FE model is validated against existing experimental data, and the model is subsequently used to investigate the behavior of reinforced CFST columns under varying geometric and material properties. The study examines failure modes, axial load-displacement responses, stress distributions, and the contribution of each material component to the load-bearing capacity of the strengthened columns. The results indicate an increase in ultimate axial strength ranging from 13% to 20% for the reinforced CFST columns. While the compressive strength of the ECC has a moderate effect on axial resistance, increasing ECC thickness, concrete strength, and steel tube yield strength significantly enhances the columns’ load-bearing capacity. Finally, a novel design model is proposed and validated, which accounts for the confinement effects provided by the CFRP grid and ECC on the concrete core. [ABSTRACT FROM AUTHOR]

In cold regions, the extensive distribution of silt exhibits limited applicability in engineering under freeze–thaw cycles. To address this issue, this study employed rice husk carbon and calcium lignosulfonate to stabilize silt from cold areas. The mechanical properties of the stabilized silt under freeze–thaw conditions were evaluated through unconfined compressive strength tests and triaxial shear tests. Additionally, scanning electron microscopy was utilized to analyze the mechanisms behind the stabilization. Ultimately, a damage model for rice husk carbon–calcium lignosulfonate stabilized silt was constructed based on the Weibull distribution function and Lemaitre's principle of equivalent strain. The findings indicate that as the content of rice husk carbon and calcium lignosulfonate increases, the rate of improvement in the compressive strength of the stabilized silt progressively accelerates. With an increase in the number of freeze–thaw cycles, the deviatoric stress of the stabilized soil gradually diminishes; the decline in peak deviatoric stress becomes more gradual, while the reduction in cohesion intensifies. The decrease in the angle of internal friction is relatively minor. Microscopic examinations reveal that as the number of freeze–thaw cycles increases, the soil pores tend to enlarge and multiply. The established damage model for stabilized silt under freeze–thaw cycles and applied loads demonstrates a similar pattern between the experimental and theoretical curves under four different confining pressures, reflecting an initial rapid increase followed by a steady trend. Thus, it is evident that the damage model for stabilized silt under freeze–thaw conditions outperforms traditional constitutive models, offering a more accurate depiction of the experimental variations observed. [ABSTRACT FROM AUTHOR]

This paper presents a progressive damage model (PDM) based on the 3D Hashin failure criterion within the ABAQUS/ExplicitTM 2021 framework via a VUMAT subroutine, enhancing the characterization of the mechanical performance and damage evolution in the elastic and softening stages of composite materials via the accurate calculation of damage variables and accommodation of non-monotonic loading conditions. In the subsequent multi-level verification, it is found that the model accurately simulates the primary failure modes at the element level and diminishes the influence of element size, ensuring a reliable behavior representation under non-monotonic loading. At the laminate level, it also accurately forecasts the elastic behavior and damage evolution in open-hole lamina and laminates, demonstrating the final crack band at ultimate failure. This paper also emphasizes the importance of correct characteristic length selection and how to minimize mesh size impact by selecting appropriate values. Compared to ABAQUS's built-in 2D model, the 3D VUMAT subroutine shows superior accuracy and effectiveness, proving its value in characterizing the mechanical behavior and damage mechanisms of fiber-reinforced polymer (FRP) materials. The enhanced 3D PDM accurately characterizes the softening processes in composite materials under simple or complex stress states during monotonic or non-monotonic loading, effectively minimizes the mesh dependency, and reasonably captures failure crack bands, making it suitable for future simulations and resolutions of numerical issues in composite material models under complex, three-dimensional stress states. [ABSTRACT FROM AUTHOR]

Mechanical characteristics, instability precursors, and fatigue life prediction of rocks under fatigue loading are significant for the prediction and prevention of mining disasters. Taking the porous siltstone widely distributed in the mining area of western China as the research object, a characteristic stress determination method based on the evolution characteristics of the multiphase volumetric strain of porous rocks was established. Referring to the characteristic stress interval, bivariate fatigue damage-controlled tests with different upper limit loads and different numbers of cycles were conducted. The results indicate that the strengthening and the weakening of the macroscopic strength of siltstone under fatigue loading are caused by the competition of two mesostructure effects, namely the "weak structure failure effect" and the "compaction embedment effect". The dominant effect varies with different upper limit loads and different numbers of cycles. Importantly, the transition of the bulk compliance from positive to negative is an early precursor of fatigue failure, while the simultaneous sudden increase in cumulative acoustic emission count, acoustic emission bk value, and energy dissipation ratio is an imminent precursor of fatigue failure. The evolution characteristics of the strain, acoustic emission, and energy dissipation indicate that the crack damage stress of siltstone is a reliable indicator of its fatigue strength. Furthermore, a nonlinear viscoplastic damage element was introduced to construct a nonlinear fatigue rheological damage model, and model validation and quantitative analysis of parameter effects were conducted. Finally, by determining the accelerated rheological start threshold and the accelerated rheological failure threshold, a rapid prediction method for the fatigue life was established. Highlights: A characteristic stress determination method suitable for porous rock. Mesoscopic mechanism of strength strengthening and weakening. Early and imminent precursors of fatigue rheological failure. A nonlinear fatigue rheological damage model. [ABSTRACT FROM AUTHOR]

The frequent far-field microdynamic disturbance caused by excavation of high-stress deep underground engineering will induce the continuous damage deterioration of surrounding rock and ultimately lead to disasters, however, the disturbance deformation and damage evolutions under true triaxial static-dynamic combined loading are unclear, and corresponding mechanical model characterizing these properties are scarce. Therefore, this study carried out a series of true triaxial static-dynamic combined loading tests to study the microdynamic disturbance characteristics of rock. The equal cyclic curve method is proposed to determine the defined disturbance critical stress of rock entering the acceleration stage. The separation methods of true triaxial static induced damage and microdynamic induced damage are proposed, and their evolution laws were investigated and the corresponding damage models were established. Further, a damage fractional mechanical model of rock was established, and the theoretical prediction curves were in reasonable agreement with the experimental results. Sensitivity analysis of static-dynamic combined stress and model parameters on disturbance deformation behaviors were further investigated, and model prediction research for the untesting conditions was also carried out to provide more understanding basis for the surrounding rock disaster mechanism and stability analysis of deep engineering under microdynamic disturbance. Numerical simulation of excavation response for typical deep buried engineering was carried out with the proposed mechanical model. Then a rock disturbance fracture degree index was proposed to realize the quantitative characterization of the location, morphology, and degree of disturbance failure in deep buried engineering surrounding rock, and found that disturbance loads promote the further expansion of the plastic zone in the surrounding rock after excavation, inducing further damage to failure. Highlights: A test method for separating true triaxial static damage and disturbance damage was proposed. The threshold of rock entering the deformation acceleration stage was defined and calculated. A novel microdynamic damage fraction mechanical model was proposed, which can well characterize the experimental results. Sensitivity analysis of static and dynamic stresses and model parameters were investigated. A rock disturbance fracture degree index was proposed to evaluate disturbance failure degree of surrounding rock after excavation. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms of crack propagation and failure behavior in rocks is fundamental for geotechnical engineering and mining applications. This study employs a coupled damage model based on the Smoothed Particle Hydrodynamics (SPH) method that integrates the Drucker–Prager and Grady–Kipp models. This mixed failure model is then implemented to simulate the crack propagation morphology and failure modes in uniaxial compression tests of flawed rock samples, and validated against multiple experimental observations. The numerical results exhibit good agreement with experimental observations from the literature in terms of the initiation and propagation of tensile and shear fractures, as well as the final failure morphology. Additionally, this work incorporates contact algorithms to simulate the loading plates, thereby better representing the actual experimental conditions encountered in uniaxial compression tests. Furthermore, a comprehensive parametric study is conducted to investigate the influence of key factors, such as pre-flaw geometry, cohesion, friction at the loading plate interface, and discretization parameters, on the simulated fracture processes and mechanical response. The outcomes indicate the proposed coupled damage model within the SPH framework can accurately capture complex fracture patterns and failure mechanisms in uniaxial compression of flawed rocks. This work demonstrates the capability of the SPH-based mixed-mode failure model to provide insights into rock fracture and failure mechanisms. Highlights: A coupled damage model integrating the Drucker–Prager and Grady–Kipp criteria within a smoothed particle hydrodynamics (SPH) framework is applied to simulate both shear and tensile failure modes in rocks firstly. The model is validated against more experimental observations, demonstrating the model's ability to reproduce the crack propagation and characteristic stress–strain behavior. This work presents a comprehensive parametric study investigating the influence of key factors, such as pre-flaw geometry, cohesion, friction at the loading plate interface, and discretization parameters, on the simulated fracture processes and mechanical response. These systematic investigations provide valuable insights into the governing mechanisms and highlight the importance of proper model calibration for accurate predictions. This work incorporates contact algorithms to simulate the loading plates, thereby better representing the actual experimental conditions encountered in uniaxial compression tests. The tensile wing cracks subjected to uniaxial compression, oriented vertically towards the top boundary of the specimen, are successfully captured. [ABSTRACT FROM AUTHOR]

The Manson-Halford (M-H) nonlinear cumulative damage model is widely applied for fatigue life analysis problems under multi-level loading. In this model, the influence of loading sequence on the fatigue life can be better considerer, but the loading interaction effect is ignored. An improved whale optimization algorithm (IWOA) by integrating multiple strategies is proposed. The ability of global search and local exploitation is balanced and improved through nonlinear convergence factor, adaptive weighting factors and the Cauchy reverse learning strategies. In order to fully account for loading interaction effect, loading weighting factors are introduced to modify the M-H model, and the parameters are optimized through the global search properties of IWOA. The model is evaluated on multi-level loading fatigue experimental data from five metal materials and two aluminum alloy welded joints. The results suggest that the proposed IWOA has better optimization accuracy compared to the standard whale optimization algorithm (WOA). The proposed modified M-H model has better prediction performance compared to the four traditional cumulative damage models, which can be effectively applied to multi-level loading fatigue life analysis problems under actual working conditions. The proposed model is useful for the study of fatigue life evaluation methods. [ABSTRACT FROM AUTHOR]

The study of damage and failure in fractured rock masses is crucial. This study employs the representative volume element (RVE) method to develop a microscale rock model. The model simulates the propagation and rupture of fractures by integrating factors including actual mineralogical composition, the Weibull distribution function, the Mohr–Coulomb damage criterion, and strain softening. Results indicate that fractures reduce the uniaxial compressive strength of the rock and that peak strength is significantly correlated with crack geometries. Plastic damage in rocks was categorized into three stages: elastic, rapid growth, and postpeak softening. A logistic growth model describes the plastic volume change curves for rocks with various fracture geometries, establishing the relationship between plastic damage volume and damage variables. Constitutive models for rocks with varying fracture geometries under uniaxial compression were formulated. The accuracy and applicability of these models were validated, providing a theoretical basis for rock engineering applications. Highlights: A heterogeneous plastic damage model based on representative volume elements is developed.A logistic growth model was used to describe the plastic volume change curves for rocks containing different fracture geometries.The relationship between rock plastic damage volume and damage variables was established.Plastic damage constitutive models of rocks containing different fracture geometries under uniaxial compression were obtained and validated. [ABSTRACT FROM AUTHOR]

An enhanced nonlinear fatigue damage cumulative model proposed is based on the strength degradation characteristics of composites, aiming to investigate damage progression under fatigue loading. Building upon this foundation, given the assumption of a linear correlation between fatigue cumulative damage and stress level, a methodology is presented for extrapolating the damage curve of untested stress levels from that of tested stress levels. The model substantiates its reliability by validating against experimental data from several distinct material types. The reliability of the model has been validated using experimental data from multiple groups of materials. The experimental results indicate that the model can effectively reflect the fatigue damage development characteristics of composite materials. Simultaneously, the predicted stress levels derived from the proposed methodology show lesser deviation from the fitted data. Finally, a life prediction method founded on the proposed model is introduced, validated for its high prediction accuracy through experimentation. Highlights: An enhanced fatigue damage model of composites is established.A novel residual strength model for composites has been established.Present a methodology for calculating the stress level damage curve.The fatigue life prediction method of the proposed model is developed. [ABSTRACT FROM AUTHOR]

Due to their exceptional impact resistance, ceramics are extensively used in various fields. However, unavoidable pores, microcracks, and inherent defects can degrade the performance of ceramic materials. A damage model of SiC ceramics under passive confining pressure was constructed based on the Lemaitre strain equivalence principle and the Weibull distribution function. This paper presented a dynamic damage model for SiC ceramics subjected to passive confinement pressure based on the principles of damage mechanics. Additionally, the split Hopkinson pressure bar device was employed to investigate the compressive strength and damage evolution of SiC ceramics at various shock pressures and confinement degrees. The experimental results indicate that constraints can reduce the damage to ceramics. The metal sleeve increased stiffness when compressing the ceramic material, allowing the specimen to convert from brittle–plastic–brittle. When sufficient constraints can be provided, the peak strain decreases gradually with the increase of the impact air pressure. Experimental data showing good agreement with the proposed model validated and analyzed the established model. Thinner boundary constraints cannot maintain the stability of ceramic structures, thicker boundaries do not significantly improve performance, and thicker boundaries can cause more weak areas. This paper provides guidance for the design of encapsulated ceramic composite armor by quantitatively studying the constraint thickness. [ABSTRACT FROM AUTHOR]

Quasi-static compression/tension, dynamic compression/shear mechanical property tests, fracture morphology characterization, dynamic response experiment, numerical simulation, and calculation of the ultimate penetration velocity of the high-strength steel under the impact of large mass low-velocity fragments and small mass high-velocity fragments were carried out to study the ballistic performance of high-strength steel used for armor vehicle protection and clarify its dynamic response under Ballistic impact. The fracture mode of the high-strength steel under dynamic impact compression and shear was shear failure. A large number of fine parabolic shear dimples were formed on the fracture surface. The high-strength steel had an obvious strain rate strengthening effect and adiabatic shear sensitivity. The plug formed under the low-velocity impact of a large mass fragment was a cone shape, and the impact area of the target plate underwent slight bending plastic deformation. The damage of the fragment to the target plate includes both adiabatic shear failure and ordinary shear failure. Under the high-velocity impact of small mass fragments, the fragments were seriously deformed and destroyed, and the damage model of the target plate is adiabatic shear failure. [ABSTRACT FROM AUTHOR]

Metal/CFRP hybrid structures have been increasingly applied in the automotive industry due to their favorable weight-saving and crashworthiness. In this article, a nonlinear finite element (FE) model is established to study the axial crushing behavior of aluminum/CFRP thin-walled tube structures. A progressive damage constitutive model is employed to capture the intra-laminar response of composites; Johnson-Cook model is used to describe the crushing process of aluminum layers and a bilinear cohesive zone model is applied for modeling the inter-layer delamination during the collapse process. A user material subroutine VUMAT involving these damage models is coded and executed to attain the numerical solution based on ABAQUS/Explicit solver. The axial crushing processes of thin-walled tubes with different configurations are simulated, and the corresponding damage characteristics are analyzed thoroughly. The influence of aluminum layer arrangement and cross-sectional shape on the crashworthiness and energy absorption of thin-walled tubes is discussed, which provides a design basis for the application of energy absorption elements. [ABSTRACT FROM AUTHOR]

Despite recent advances in treatment, non–small cell lung cancer (NSCLC) continues to have a high mortality rate. Currently, NSCLC pathogenesis requires further investigation, and therapeutic drugs are still under development. Homologous recombination repair (HRR) repairs severe DNA double‐strand breaks. Homologous recombination repair deficiency (HRD) occurs when HRR is impaired and causes irreparable double‐strand DNA damage, leading to genomic instability and increasing the risk of cancer development. Poly(ADP‐ribose) polymerase (PARP) inhibitors can effectively treat HRD‐positive tumors. Extracellular heat shock protein 90α (eHSP90α) is highly expressed in hypoxic environments and inhibits apoptosis, thereby increasing cellular tolerance. Here, we investigated the relationship between eHSP90α and HRR in NSCLC. DNA damage models were established in NSCLC cell lines (A549 and H1299). The activation of DNA damage and HRR markers, apoptosis, proliferation, and migration were investigated. In vivo tumor models were established using BALB/c nude mice and A549 cells. We found that human recombinant HSP90α stimulation further activated HRR and reduced DNA damage extent; however, eHSP90α monoclonal antibody, 1G6‐D7, effectively inhibited HRR. HRR inhibition and increased apoptosis were observed after LRP1 knockdown; this effect could not be reversed with hrHSP90α addition. The combined use of 1G6‐D7 and olaparib caused significant apoptosis and HRR inhibition in vitro and demonstrated promising anti‐tumor effects in vivo. Extracellular HSP90α may be involved in HRR in NSCLC through LRP1. The combined use of 1G6‐D7 and PARP inhibitors may exert anti‐tumor effects by inhibiting DNA repair and further inducing apoptosis of NSCLC cells. [ABSTRACT FROM AUTHOR]

ABSTRACT This study presents a procedure based on constant amplitude (CA) fatigue data to predict the statistical fatigue lifetime of glass/orthopolyester composites subjected to repeated ordered and random two, three, and six sequences of block loadings. A numerical routine was developed to detect cycle‐by‐cycle the statistical strength degradation progression until failure, assuming that the strength at the end of a block cycle equals the strength at the start of the successive one and that the individual samples' static strength, the amount of degraded strength, and fatigue life share the same rank in their respective cumulative distribution function. Predictions conform to the statistically undetectable loading sequence effects and lightly overestimate the lifetimes of random and ordered high‐to‐low (1/100 cycles) repeated two‐block loadings. The vanishing effect of the loading sequence when the block extents remain fixed, the block extent effects for a given three‐block sequence, and the lifetimes of three‐block loadings were fully predicted. The six‐block sequence's experimental lifetimes with different block loading orders and block extent fell within the predicted lifetimes' cumulative distribution function. A reliable damage rule based on residual strength was proposed and compared to the Miner's rule. [ABSTRACT FROM AUTHOR]

Highlights The selection of highly efficient materials is a crucial task for designing protective structures or armor against extreme explosive loadings. Due to the high strength‐to‐weight ratio of various grades of aluminum alloys and composites, they are mostly preferred for making protective structures. Investigation of their explosion resistance characteristics through experiments is very costly, dangerous, and time‐consuming. Hence, the present work deals with a cost‐effective numerical analysis on explosion resistance performance evaluation of various armor‐grade aluminum alloy plates of the same areal densities under 1–3 kilograms of trinitrotoluene explosions at a 100 mm stand‐off distance. The superior‐performance aluminum alloy plate is further reinforced with a high‐strength carbon/epoxy polymer composite to enhance its performance. The masses of the plates are maintained constant throughout the study. The Johnson‐Cook rate‐dependent material model and a progressive damage model including Hashin with Puck‐Schumann failure criteria were used to determine the realistic failures in the aluminum alloys and polymer composites, respectively. The outcomes of the study showed that the AA7075‐T6 plate has the highest deformation resistance under extreme explosion loadings. Carbon fiber‐reinforced aluminum laminate (CRALL) showed improved deformation resistance and energy absorption than those of the same mass of monolithic plate. Explosion resistance of various aluminum alloys of equal masses is compared. AA7075‐T6 provides better protection against blast compared with other alloys. To design CRALL, a carbon/epoxy composite used to reinforce the AA7075‐T6. CRALL provides 16.3% smaller peak deflection than the same mass of AA7075‐T6. CRALL improved energy absorption by 29.3% compared with same mass of AA7075‐T6. [ABSTRACT FROM AUTHOR]

Cycles of a fasting-mimicking diet (FMD) promote regeneration and reduce damage in the pancreases, blood, guts, and nervous systems of mice, but their effect on kidney disease is unknown. In addition, a FMD has not been tested in rats. Here, we show that cycles of a newly developed low-salt FMD (LS-FMD) restored normal proteinuria and nephron structure and function in rats with puromycin-induced nephrosis compared with that in animals with renal damage that did not receive the dietary intervention. LS-FMD induced modulation of a nephrogenic gene program, resembling renal developmental processes in multiple kidney structures. LS-FMD also activated podocyte-lineage reprogramming pathways and promoted a quiescent state in mature podocytes in the rat kidney damage model. In a pilot clinical study in patients with chronic kidney disease, FMD cycles of 5 days each month for 3 months promoted renoprotection, including reduction of proteinuria and improved endothelial function, compared with that in patients who did not receive the FMD cycles. These results show that FMD cycles, which promote the reprogramming of multiple renal cell types and lead to glomerular damage reversal in rats, should be tested further for the treatment of progressive kidney diseases. [ABSTRACT FROM AUTHOR]

The present study assesses the potential of using machine learning (ML) methods to predict the extent of lightning thermal damage in fiber-reinforced composite laminates using three supervised machine learning (SML) algorithms: (1) linear regression (LR), (2) decision tree (DT)-based, and (3) MLP models. These models were based on the 10 most significant factors that influence the severity of lightning damage, including three current waveform parameters, four material configurations, and three orthogonal electrical conductivities of each composite. All models demonstrated good performance with coefficient of determination (R2) values between 0.84 ~ 0.96. The multilayer perceptron (MLP) regression model trained with the lightning matrix damage dataset showed the most promising results (R2 > 0.94). Additional hyperparameter optimization was performed to improve the prediction performance of the baseline MLP model. The hyperparameter optimization (Adam optimizer, tanh activation function, and three hidden layers with 234 neurons) slightly improved the performance of the baseline MLP model by ~0.02, but achieved faster convergence. This result suggests that the baseline MLP model trained with the lightning matrix damage dataset is sufficiently accurate and robust. This paper highlights that ML-informed regression models can serve as an efficient first pass-estimator of lightning matrix damage in composite laminates, potentially reducing the amount of extremely time-consuming and expensive laboratory-scale lightning tests or streamlining the development of complex lightning damage models for future design. [ABSTRACT FROM AUTHOR]

ABSTRACT One essential initial step in the analysis of ancient DNA is to authenticate that the DNA sequencing reads are actually from ancient DNA. This is done by assessing if the reads exhibit typical characteristics of post‐mortem damage (PMD), including cytosine deamination and nicks. We present a novel statistical method implemented in a fast multithreaded programme, ngsBriggs that enables rapid quantification of PMD by estimation of the Briggs ancient damage model parameters (Briggs parameters). Using a multinomial model with maximum likelihood fit, ngsBriggs accurately estimates the parameters of the Briggs model, quantifying the PMD signal from single and double‐stranded DNA regions. We extend the original Briggs model to capture PMD signals for contemporary sequencing platforms and show that ngsBriggs accurately estimates the Briggs parameters across a variety of contamination levels. Classification of reads into ancient or modern reads, for the purpose of decontamination, is significantly more accurate using ngsBriggs than using other methods available. Furthermore, ngsBriggs is substantially faster than other state‐of‐the‐art methods. ngsBriggs offers a practical and accurate method for researchers seeking to authenticate ancient DNA and improve the quality of their data. [ABSTRACT FROM AUTHOR]

To elucidate the degradation mechanism of expansive soil–rubber fiber (ESR) under freeze–thaw cycles, freeze–thaw cycle tests and consolidated undrained tests were conducted on the saturated ESR. The study quantified the elastic modulus and damage variables of ESR under different numbers of freeze–thaw cycles and confining pressure, and proposed a damage constitutive model for ESR. The primary findings indicate that: (1) The effective stress paths of ESR exhibit similarity across different numbers of freeze–thaw cycles, the critical stress ratio slightly decreased by 8.8%, while the normalized elastic modulus experienced a significant reduction, dropping to 42.1%. (2) When considering the damage threshold, the shear process of ESR can be divided into three stages: weak damage, damage development, and failure. As strain increases, the microdefects of ESR gradually develop, penetrating macroscopic cracks and converging to form the main rupture surface. Eventually, the damage value reaches 1. (3) Due to the effect of freeze–thaw cycles, initial damage exists for ESR, which is positively correlated with the number of freeze–thaw cycles. The rubber fibers act as tensile elements, and the ESR damage evolution curves intersect one after another, showing obvious plastic characteristics in the late stage of shear. (4) Confining pressure plays a role in limiting the development of ESR microcracks. The damage deterioration of ESR decreases with an increase in confining pressure, leading to an increase in ESR strength. (5) Through a comparison of the test curve and the theoretical curve, this study validates the rationality of the damage constitutive model of ESR under established freeze–thaw cycles. Furthermore, it accurately describes the nonlinear impact of freeze–thaw cycles and confining pressure on the ESR total damage. [ABSTRACT FROM AUTHOR]

Highlights The outstanding mechanical performance and flowability of unidirectionally arrayed chopped strands (UACSs) give them an advantage in the manufacture of engineering structures with complex geometry. For the application of practical structures, the impact responses and damage evolution of material under low‐velocity impact must be investigated in advance. In this study, UACS laminates and continuous carbon fiber laminates with a stacking sequence of [0/90]4s and a thickness of 2 mm were fabricated for low‐velocity impact tests at 7, 11, 15, and 20 J. The impact responses and postimpact intralaminar damage area were analyzed according to the experimental results, including impact load responses and ultrasound C‐scan inspections. Moreover, to predict the damage evolution of the internal structure, the 3D finite element models were constructed in ABAQUS using a progressive damage model (PDM) through a user‐material subroutine VUMAT. Compared with continuous carbon fiber laminates, the dissipated energy of UACS laminates increases by approximately 10.64% and 57.37% for the 15 and 20 J, respectively. However, the intralaminar damage area of UACS laminates decreased by 29.96% and 28.16% at 15 and 20 J, respectively, since the discontinuous slits in UACS laminates can guide damage paths and suppress damage propagation. The regularly arrayed short fiber reinforced composite was studied. Revealed the low‐velocity impact responses and predicted the damage evolution. UACS and CFRP laminates have comparable impact performance. Illustrated the slits design can suppress the damage to a relatively small area. [ABSTRACT FROM AUTHOR]

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Structural steel (E250 grade) is used in several engineering applications involving loadings from quasi-static to high strain rates (blast discs, explosion vents, etc.), which introduce large deformation, strain and strain rate hardening, thermal softening, and damage to the material. The material's dynamic constitutive behaviour can be aptly modelled by a visco-plasticity-based Johnson–Cook (J–C) strength model and damage initiation and complete failure by the J–C's damage model. In the latter, damage initiation is modelled through continuum damage mechanics and propagation by the fracture mechanics. This paper focuses on the determination of 10 different J–C's dynamic constitutive and damage model parameters for E250 structural steel by conducting several experiments involving tensile tests at different strain rates (0.0003–1.0 s-1), stress triaxialities (0.33–0.95), temperatures (30–800 °C), and SHPB experiments (at 3000 and 8000 s-1). It explains the processes and step-by-step procedures for extracting the model parameters from the experimental results. A different approach is followed in arriving at fracture strain for extracting damage model parameters to suit fracture mechanic-based damage evolution available in the existing FEA codes. The constitutive and damage model parameters thus determined are validated through numerical simulations and comparison with three independent experiments viz. i) experiment of a plain tensile specimen, ii) tensile experiment of a notched specimen, and iii) hydrostatic burst experiment of a flat burst disc. The responses and failure patterns from numerical simulations agreed very well in all three experiments, thereby validating the determined model parameters. The determined model parameters can be utilised directly in the commercially available nonlinear explicit FEA codes. [ABSTRACT FROM AUTHOR]

An energy‐based isotropic elastoplastic damage model is developed for investigating the elastoplastic damage responses and stress–strain relationships of nano‐silica incorporated concrete. The formulation employs a multiscale micromechanical framework to determine the effective elastic properties of composites at different scales. The stress–strain constitutive relation is derived by splitting the strain tensor into "elastic‐damage" and "plastic‐damage" parts while introducing the homogenized free potential energy function and the undamaged potential energy function. The elastoplastic damage response of the material is further characterized by elastic–plastic‐damage coupling. To construct realistic 3D three‐phase concrete mesostructures in numerical simulations, this paper introduces an encapsulation placement method that avoids particle overlap checking when placing aggregates. This methodology allows adjustments for the aggregate compactness as needed and enhances computational efficiency in concrete mesostructure construction. The numerical results of the modeling show good agreement with the experimental values in the open literature. Further, the influence of nano‐silica addition contents and ITZ (interfacial transition zone) thicknesses on the elastoplastic damage response of nano‐silica incorporated concrete are quantitatively and qualitatively investigated for the optimization of nano‐silica incorporated cementitious composites. The proposed model facilitates simulating and optimizing the mechanical characteristics of nano‐silica incorporated concrete and enhances the computational efficiency of 3D concrete modeling with the introduced encapsulation placement method. [ABSTRACT FROM AUTHOR]

Considering the nonlinearity of shear in the mechanics of composite materials, the increase of shear strength when the substrate interface is compressed, and the shear of the matrix itself, the Chang–Chang criterion is improved. The improved Chang–Chang criterion was used to establish a progressive damage model of low‐velocity impact of composites. The low‐velocity impact process of T700/EM134 composite laminates in the energy range from 5 to 10 J was compared by physical tests and finite element simulations, and the calculated impact response curves and material damage were in good agreement with the test results, which proved that the model of the improved criterion was suitable for the damage prediction of low‐velocity impact of composite laminates. Highlight: Consider various situations in composite material shearing.Improved based on the Chang–Chang criterion.Establishing a progressive damage model for low‐speed impacts.Comparison through physical experiments and finite element simulation.Prove that the improved criterion model is suitable for damage prediction. [ABSTRACT FROM AUTHOR]

Highlights The 3D woven spacer fabric lightweight composites (WSFC) show promising applications in construction, transportation and aerospace. In this study, the 3D WSFC with different structural variations (e.g., layer thicknesses, stacking and face layer thickening) were designed and fabricated. The fracture strengths of single‐layer WSFC in the weft direction with layer thicknesses of 5, 10 and 15 mm were 54.4, 14.3, and 5.4 MPa. In the weft direction, the fracture strengths of double‐ and triple‐stacked 3D WSFCs were 30.6 and 21.7 MPa, which improved 1.1 times and 3.0 times as compared with those of original single‐layer 3D WSFCs, respectively. The double‐ and triple‐stacked WSFC also had large flexural deformation. The 3D WSFC with double‐layer misaligned stacking had the similar flexural strengths in both directions, which obviously reduced the performance differentiation of 3D WSFC in different directions. With the addition of face layer fabric, the mechanical performances of 3D WSFC were notably enhanced, and the damage modes were changed from brittle failure to ductile failure. Furthermore, a multi‐scale model of 3D WSFC with different structural variations was developed for numerical simulation to analyze the stress distribution and damage mechanism. Stacking design obviously improves mechanical properties of 3D WSFC. WSFC with misaligned stacking has similar flexural strengths. A multi‐scale elastic–plastic damage model for 3D WSFC is established. Damage modes of WSFC are changed with the stacking method. [ABSTRACT FROM AUTHOR]

AbstractIn the present investigation, the selective laser melting (SLM) technique has been utilized for the 3-dimensional printing (tensile test specimens) of SS316L steel powder at 00 (horizontal) and 900 (vertical) angles. Further, an experimental and finite element analysis approach has been made to analyse the effect of printed orientation or direction on the Hollomon power law parameters (strain hardening exponent (n) and strength coefficient (K)) and ductile damage parameters (fracture strain (εf), stress triaxiality (η) and strain rate (ε̇)). The influence of printing orientation on plastic deformation behavior has also been analysed. The results revealed that 00 angle 3D-printed specimens exhibited 11.05%, 21.97% and 9.50% more yield strength, tensile strength and elongation than 900 angle 3D-printed tensile test specimens. Further, the strain hardening exponent (n) and strength coefficient (K) (Hollomon power law hardening model parameters) for 00 angle 3D-printed specimens are 35.80% and 32.47% more than the 900 angle 3D-printed tensile test specimens respectively. The fracture strain for 00 angle 3D-printed specimens is 37.82% less than the 900 angle 3D-printed tensile test specimens. The percentage difference between FEA and experimental results is less than 5% which shows the good prediction capability of estimated Hollomon power law parameters and ductile damage model parameters with developed FEA model for 00 and 900 3D printed specimens. [ABSTRACT FROM AUTHOR]

The solution of coupled multi‐field problems by means of commercially available finite element codes such as Abaqus constitutes an important part in the study of industrial processes. Against this background, a comprehensive implementation framework for a gradient‐enhanced continuum damage formulation in a thermo‐mechanically coupled finite deformation setting is proposed in this contribution. To assess the applicability of the implementation framework to industrial processes, a thermo‐mechanically coupled, gradient‐enhanced ductile damage model is exemplarily employed. The resulting three‐field problem, consisting of the balance of linear momentum, the heat equation and the balance of micromorphic momentum, is implemented based on an Abaqus user material by making use of a novel two‐instance formulation. Representative simulation results are discussed, with the specific focus lying on the application to manufacturing processes involving complex contact interactions. The Abaqus framework is made available as an open‐source code on GitHub, see Sobisch et al., Finite Elements in Analysis and Design 232 (2024) 104105. [ABSTRACT FROM AUTHOR]

In addressing the difficulty of forming Fiber Metal Laminates (FMLs), a laminate composed of a 0.1 mm-thick 304 Stainless Steel Foil (SSF) and Carbon Fiber Reinforced Plastics (CFRP) as the base material is prepared using a specific process. Subsequently, forming limit diagrams are obtained through hemispherical bulge forming experiments to investigate the forming performance of FMLs laminates. The damage phenomena of various forming specimens during the thermal stamping process are analyzed. Based on different damage forms, corresponding theoretical models are established to simulate and predict the forming damage modes of FMLs through simulation. The research results indicate that the stamping formability of FMLs is influenced by the damage tolerance of the thin stainless steel foil. During the thermal stamping process, FMLs may experience delamination, fracture/crack of the thin stainless steel foil, and rupture/tearing/wrinkling of the prepreg. To address these issues, cohesive elements, GTN-M-K damage, and Hashin damage models are established, providing a reasonable simulation prediction of the stamping damage phenomena of FMLs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The VO2 and VO2 -SiO2 composite films were prepared by sol-gel method. The phase structure and transmittance of films were characterized by X-ray diffraction (XRD) and ultraviolet visible spectrophotometer. The results reveal that the prepared VO2 film is monoclinic phase (B), and the XRD patterns of VO2 -SiO2 composite film is similar to that of VO2 film. The optical transmittance of films have reached over 90% within the range of 450 nm to 800 nm. The laser induced damage threshold (LIDT) of VO2 -SiO2 composite film is 3. 9 J/cm2, which is 77. 3% higher than that of VO2 film. The difference in damage morphology between VO2 film and VO2 -SiO2 film were studied by FESEM and step analyzer. The VO2 film exhibits melt type damage, while the VO2 -SiO2 film exhibits melt type damage and stress damage. In addition, laser-induced damage models for different films were constructed and damage characteristics and underlying mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Background/Objectives: Microwave ablation (MWA) is the leading therapy method for treating patients with liver cancer. MWA simulation is used to further improve the therapy and to help develop new devices. Methods: A water-cooled ablation needle was reconstructed. MWA simulations of a polyacrylamide phantom were carried out and compared with a representative clinical example (tumor diameter: 8.75 mm). The Arrhenius damage model and a critical temperature approach of 60 °C were applied to assess the necrosis zones. Finally, the simulation results were compared to the corresponding MR measurements. Results: Most of the heating in the simulation took place at a distance of 5 mm along the transverse axis and 20 mm along the longitudinal axis above the needle tip. The calculated Dice scores for the Arrhenius model were 0.77/0.53 for the phantom/clinical case. For the critical temperature approach, Dice scores of 0.60/0.66 for the phantom/clinical case were achieved. Conclusions: The comparison between simulated and measured temperature increases showed an excellent agreement. However, differences in the predicted necrosis volume might be caused by omitting consideration of the heat sink effect, especially in the clinical case. Nevertheless, this workflow enables short MWA simulation times (approximately 3 min) and demonstrates a step towards possible integration into daily clinical use. [ABSTRACT FROM AUTHOR]

Inflammatory diseases of the intestinal tract in piglets severely impair the economic performance of pig farms. Pig milk exosomes can encapsulate miRNAs which can then enter the piglet intestine to play an immunomodulatory role. Previously, we comparatively analyzed and identified exosomal miRNAs in the colostrum and mature milk of Bamei and Landrace pigs, and we screened for ssc-miR-22-3p, which is associated with inflammation and immune response; however, the role played by ssc-miR-22-3p in the immune response in IPEC-J2 cells is not yet clear. In this study, we first constructed a pig intestinal inflammatory response model using Lipopolysaccharide (LPS) and Polyinosinic-polycytidylic acid (Poly (I:C)), and we investigated the role of ssc-miR-22-3p targeting MAPK14 in the regulation of LPS and Poly (I:C)-induced inflammatory injury in IPEC-J2 cells by RT-qPCR, cell counting kit-8 (CCK-8), EdU staining, lactate dehydrogenase (LDH) activity assay, and dual luciferase reporter gene assay. We successfully established LPS and Poly (I:C)-induced cell damage models in IPEC-J2 cells. The immune response of IPEC-J2 cells was stimulated by induction of IPEC-J2 cells at 10 μg/mL LPS and 20 μg/mL Poly (I:C) for 24 h. Overexpression of ssc-miR-22-3p decreased cytokine expression and promoted cell viability and proliferation. The functional enrichment analysis revealed that ssc-miR-22-3p targets genes enriched in the pathways of negative regulation of inflammatory response and bacterial invasion of epithelial cells. The validity of the binding site of ssc-miR-22-3p to MAPK14 was tested by a dual luciferase reporter gene. Pig milk exosome ssc-miR-22-3p promotes cell viability and proliferation by targeting MAPK14, and it alleviates LPS and Poly (I:C)-induced inflammatory responses in IPEC-J2 cells. [ABSTRACT FROM AUTHOR]

When building a tunnel in an environment rich in high‐temperature hot water, it is particularly necessary to pay attention to the influence of sulfate ions in underground hot water on tunnel shotcrete. In order to study the sulfate erosion mechanism and mechanical properties of shotcrete in a real high‐temperature hot water environment, this study was carried out by setting the curing temperature (20, 40, 60, and 80°C), humidity (55% RH, 95% RH), and erosion age (0, 15, 30, 60, and 90 d) as the test influencing factors; a full combination of dry‐wet cycle test was carried out, and the specimens under different conditions were analyzed macroscopically and microscopically. The results show that with the increase of the number of dry‐wet cycles, the quality of shotcrete increases first and then decreases, and the mechanical properties gradually decrease. In the early stage of erosion, the erosion product is mainly ettringite, and the macroscopic damage is aggregate spalling. In the later stage of erosion, the erosion product is mainly gypsum, and the macroscopic damage is expansion damage. Compared with standard curing, a certain degree of high temperature curing has little effect on the sulfate attack resistance of shotcrete, but when the curing temperature exceeds 60°C, the concrete is seriously damaged. Finally, by constructing the damage model of sulfate attack shotcrete, the variation of compressive strength of shotcrete with age after sulfate attack under different curing conditions was successfully predicted. [ABSTRACT FROM AUTHOR]

Purpose: Concrete gravity dams are important structures for flood control and hydraulic power generation, but they can be vulnerable to seismic activity due to ground movements that trigger crack propagation. Design/methodology/approach: To better understand the factors that affect the stability of concrete gravity dams against concrete fracture during earthquakes, a concrete plastic damage model has been utilized with two new expressions to simulate compressive and tensile damage variables. Findings: The findings showed that the crack patterns were strongly influenced by the concrete's strength. The simulation results led to the proposal of appropriate concrete properties aimed at minimizing damage. These findings, together with the proposed model, offer significant insights that can enhance the safety and stability of concrete gravity dam structures. Originality/value: This study offers a comprehensive analysis of concrete behavior under varying grades and introduces simple and robust expressions for evaluating concrete parameters in plastic damage models. The versatility of these expressions enables accurate simulation of stress-strain curves for different grades, resulting in excellent agreement between model results and experimental findings. The simulation of the Koyna Dam case study demonstrates a similarity in crack patterns with previous simulations and field observations. [ABSTRACT FROM AUTHOR]

The extraction of thick coal seams at high intensity inevitably leads to more severe strata pressure, especially when influenced by adjacent goaf areas. The combination of multiple strata pressures results in significant deformation of the surrounding rock along the goaf roadway. In order to the problem of large deformation of the surrounding rock of the gob-side roadway, this study proposes a novel method for protecting gob-side roadway using energy-gathering blasting (EGB) to cut roof and relieve pressure, which combines parallel pull-rods fracture theory with the Weibull strength of rock microelements to establish a new energy-gathering blasting model. The optimal spacing of blast holes is determined and the correlation between damage degree and energy-absorbing coefficient as well as explosive center distance is analyzed. Numerical simulation methods are employed for validation, and the results demonstrate that the EGB technique effectively blocks the transmission of stress in non-energy-absorbing directions, further enhancing energy accumulation in the energy-gathering direction. This leads to slower attenuation of effective stress and particle vibration velocity in the energy-gathering direction, promoting the directional expansion of energy-gathering fractures and revealing the mechanical mechanism of energy-gathering fracture directional expansion. Based on this technology, a method for relieving overburden pressure in the surrounding rock is proposed. Through EGB technique cutting the long cantilever structure of thick and hard rock layers is snapped, force them to collapse and expand, thereby supporting the overlying structure and reducing stress concentration in the roadway's surrounding rock. This method reveals the mechanism of pressure unloading in the mining area after roof cutting. Furthermore, based on theoretical analysis, the parameters for roof-cutting pressure unloading are designed, and engineering practice confirms the successful reduction of stress on both sides of the roadway ahead of the working face, optimizing the stress environment of the roadway and achieving the goal of protecting the tests have validated the effectiveness of the method, significantly reducing stress and deformation in the surrounding rock of the roadway. The research findings provide a scientific basis for controlling roadway deformation under similar conditions. Highlights: A new EGB method is proposed based on characteristics of rock. A novel damage model for EGB has been constructed by combining the rock micro element strength with the tension rod fracture theory. The application of EGB method in coal mining can effectively reduce mine pressure and protect roadway. [ABSTRACT FROM AUTHOR]

The freeze–thaw (FT) cycle will lead to rock damage and cause hidden danger to the safety of rock engineering. In order to explore the FT damage characteristics of rocks in cold regions, 0, 20, 30, 40 and 50 FT cycle tests and uniaxial compression tests were carried out on intact and single-fracture cyan specimens with crack inclination angle β of 0°, 45° and 90°, respectively, to study the FT damage problems of rocks from the aspects of physical, mechanical and energy characteristics. The results show that the FT damage of cyan sandstone specimens is mainly dominated by the mechanical action of water–ice phase transition, resulting in relatively little influence on the saturation weight. The porosity of the cyan sandstone specimen increases gradually with the increase of FT cycle, and it has an exponential function relationship with the peak strength, Hoek–Brown model parameter s and energy storage limit, which also implies their variation with the increase of FT cycle. Based on Lemaitre's strain equivalent hypothesis and energy dissipation principle, FT-stress damage models of intact and fractured rocks are established. It is found that the initial damage and critical damage are positively correlated with the number of FT cycles and negatively correlated with crack inclination angle. With initial damage as the characteristic parameter, a critical damage model for rocks subjected to FT cycles is proposed based on the test data and data obtained from existing references. In addition, a normalized degradation equation for the peak strength and energy storage limit of FT-damaged rocks under uniaxial compression is proposed based on classical damage mechanics and critical damage model, and its applicability is verified by test data and relevant data from references. In general, the results of this study can provide a reference for the study of FT damage of rocks in cold regions, and be conducive to clarifying the relationship between FT damage of rocks and the deterioration of mechanical properties and energy storage capacity. Highlights: The change of peak strength, apparent stiffness, Hoek Brown model parameter were discussed. The energy accumulation effect, energy storage limit, peak dissipated energy and energy dissipation effect were analyzed. A freeze–thaw-stress damage model for intact and fractured rocks was established, the concepts of initial and critical damage were introduced. The critical damage model of FT damaged rocks was obtained and discussed. The normalized degradation equations of peak strength and energy storage limit of FT damaged rocks are proposed. [ABSTRACT FROM AUTHOR]

Rapid and partial acquisition are features of rock drilling for obtaining rock properties. Most previous research has primarily concentrated on how to quickly obtain rock mechanics parameters, with limited emphasis on extracting rock parameter fields, particularly in three dimensions. This study attempted to develop a numerical integrated method to extract 3D parameter fields of rocks based on a newly developed digital-controlled drilling platform. The importance of incorporating a damage model for accurate simulations of rock drilling through finite element analysis (FEA) was investigated. By calibrating damage parameters through uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) tests, these parameters can be considered constants in rock drilling simulations across various rock types. The accuracy of rock parameters estimated by the proposed method and the derived analytical model were further demonstrated through comparison with the corresponding standard tests. Furthermore, the 3D parameter field of rocks was obtained by integrating a deep learning method and micro-CT technology. The numerical prediction illustrated the advantages of acquiring a rock parameter field in achieving more accurate simulations of the rock failure process. Besides, our solution can also provide support for the parameter selection of numerical models considering spatial variability for natural rocks. Highlights: A digital-controlled equipment for rock drilling was developed. Equations were derived for extracting rock parameters through the drilling data. A deep learning method was developed to reproduce the three-dimensional parameter field of rocks. The significance of considering the realistic rock parameter field was numerically demonstrated. [ABSTRACT FROM AUTHOR]

Fracturing of rocks subjected to cryogenic treatment significantly impacts the stability and permeability of underground storage facilities for liquefied natural gas (LNG). However, existing fracturing damage models lack coverage across the entire spectrum of practical engineering conditions, spanning potential temperature ranges from room temperature to − 160 °C and saturation levels from 0 to 100%. Addressing this gap, this study utilizes cracked sandstone disks to investigate the fracture toughness of sandstone following cryogenic treatment to − 160 °C using the Brazilian splitting test. In the experimental setup, treatment temperatures are specified at 15, − 40, − 80, − 120, and − 160 °C, while saturations range from 0 to 100%. The experimental findings reveal that ultralow temperatures reduce the fracture toughness of saturated sandstone by approximately 30%, whereas for dry sandstone, this reduction is approximately 7.4%. This suggests a significant influence of different pore saturations on fracture toughness. A damage model, based on the Boltzmann function, is established to incorporate the effects of both temperature and saturation. This model accurately predicts the damage variable concerning treatment temperature and saturation. Generally, as temperature decreases, the damage variable also decreases, exhibiting two stages: rapid decrease followed by gradual decrease. The transition temperature, marking the division between these stages, tends to be lower in sandstone with higher saturation levels. The experimental results are further discussed within the context of the mineral compositions present in the sandstone, elucidating the thermal–mechanical mechanisms at play. Although the current damage model is specific to sandstone, the methodological approach is generalizable to generic rock types. The damage model's adaptability allows for testing fitting parameters for specific rock types or adjusting the relevant thermal coefficients. These findings and the developed model offer valuable insights for the reliable analysis of stability and permeability in LNG storage facilities or similar geologic engineering projects. Highlights: The Mode-I fracture toughness of sandstone under variable saturation conditions subjected to cryogenic temperatures of − 160 °C is investigated. Saturated sandstone experiences more than four times the amount of damage compared to dry sandstone under ultralow temperatures. A damage model is developed to incorporate the influences of both temperature and saturation. [ABSTRACT FROM AUTHOR]

Soft biological tissues, such as arterial tissue, have the ability to grow and remodel in response to damage. Computational method plays a critical role in understanding the underlying mechanisms of tissue damage and healing. However, the existing healing model often requires huge computation time and it is inconvenient to implement finite element simulation. In this paper, we propose a computationally efficient gradient-enhanced healing model that combines the advantages of the gradient-enhanced damage model, the homeostatic-driven turnover remodeling model, and the damage-induced growth model. In the proposed model, the evolution of healing-related parameters can be solved explicitly. Additionally, an adaptive time increment method is used to further reduce computation time. The proposed model can be easily implemented in Abaqus, requiring only a user subroutine UMAT. The effectiveness of proposed model is verified through a semi-analytical example, and the influence of the variables in the proposed model is investigated using uniaxial tension and open-hole plate tests. Finally, the long-term development of aneurysms is simulated to demonstrate the potential applications of the proposed model in real biomechanical problems. [ABSTRACT FROM AUTHOR]

The hydro-mechanical behaviour and the constitutive model of sandy mudstone were investigated in this article. Two groups of hydro-mechanical triaxial compression tests were conducted. The results indicated that the inelastic deformation, damage, permeability and failure of the sandy mudstone were affected by the pore pressure and confining pressure. The hydro-mechanical behaviour was characterised by the coupled elastoplastic damage model. This model was based on the effective stress principle and numerical return mapping algorithms. Sensitivity analysis was also performed to examine the effects of four key parameters on the modelling of elastoplastic and damage behaviour. This study can provide a foundation for physical understanding and mathematical modelling of sandy mudstone under coupled loads. [ABSTRACT FROM AUTHOR]

Parametric indices are empirically related to two or more response parameters with a combination coefficient and do not conform to a physical definition of damage. The combination parameter is expected to be contingent on the loading and the state of calibration other than failure. Damage is also defined as the 'deterioration of a physical quantity' and the resulting non-parametric index does not involve any empirical constant. However, the non-parametric indices saturate much before unity. This paper first aims to assess the performance of some of the existing non-parametric indices. Experimental response until failure of a circular RC bridge pier under cyclic loading is numerically simulated for this purpose. A new physical-definition based non-parametric damage index is proposed. Setting this alternate definition as the benchmark, performance of parametric Park-Ang index, some of its variants and other non-parametric indices are studied at levels other than failure through a damage progression analysis using cyclic and seismic excitations. A parametric index and its simplified form consistent with that physical-definition are next proposed with weighted-hysteretic-energy and normalized-deformation as parameters. The same calibrated model is used in subsequent assessment. Associated combination-coefficient exhibits a stable relationship with peak drift and a loading-independent functional form is proposed. [ABSTRACT FROM AUTHOR]

The transportation and disposal of tunnel muck have detrimental environmental impacts. For this reason, the practice of reusing such a resource in engineering materials has substantial environmental and economic benefits. Seasonal frozen regions are extensively distributed worldwide, and freeze–thaw (F-T) cycles can largely degrade the performance of engineering materials, underscoring the importance of knowledge on the F-T resistance of tunnel muck. This study investigates the impact of F-T cycles on the mechanical and microscopic behavior of slurry shield tunnel muck stabilized with basalt fiber (BF) and inorganic curing agent (ICA). The qualities of muck discharged from slurry shield tunneling were improved in the composite formation of fine sand and muddy silty clay. Then tests were conducted to obtain the stress-strain characteristics, uniaxial compressive strength (UCS), and microstructure of the improved tunnel muck with different numbers of F-T cycles (N) and BF contents. Based on the Weibull probability distribution function, the damage evolution model of ICA-BF stabilized tunnel muck was proposed. The results show that the UCS decreases parabolically when the F-T cycle increases, and the F-T damage degree is 24.5%–40.6% after 12 cycles. Increasing BF content can effectively improve tunnel muck's F-T resistance (an optimal ratio of 0.5%). The failure strain of the reinforced tunnel muck is linearly correlated to the BF content and has a weak correlation with the number of F-T cycles. The F-T damage to material strength can be divided into rapid (N=0–3), slow (N=3–9), and stable (N>9) stages. The established F-T damage model can accurately predict the evolution of the F-T damage degree. [ABSTRACT FROM AUTHOR]

Compressive cyclic loads induce a progressive failure in rock materials, and the long-term stability can not be guaranteed by the strength under monotonic load. To this end, the present study aims at establishing an elastoplastic fractional fatigue damage model for predicting the accumulative deformation of rock materials in a unified framework. A fractional-order plastic flow rule is introduced to describe volume transformation of rock sample from compression to expansion, eliminating the need for plastic potential functions. And a hardening function with an equivalent plastic shear strain is adopted. Concerning the fatigue effects, the progressive deterioration of material due to cyclic loads is intricately linked to microstructural degradation, depicted by a convolution law. In the context of creep deformation, loading cycle serves as an equivalent time measure, connecting the plastic deformation with the fatigue damage. In order to verify the accuracy, the proposed model is numerically implemented by a returning mapping procedure simulate the mechanical responses of three types of rocks in both uniaxial and triaxial cyclic tests. Comparative analysis with associated fatigue model is also provided to evaluate the accumulative deformation and damage evolution of concerned rocks. • A fractional-order fatigue damage model for predicting the accumulative deformation of rocks is established. • The continuous progression due to cyclic damage is linked to microstructure degradation by a convolution law. • The model is numerically implemented by a returning mapping procedure considering the plastic and damage effects. • The accuracy is validated by comparison with experimental data of different types of rocks in cyclic tests. [ABSTRACT FROM AUTHOR]

This work presents a Finite Element approach to model the in-plane mechanical behavior of C/C-SiC fabrics at the lamina level, including the non-linear response of diverse lay-ups and the bending-to-tensile strength ratio at failure. The material model employs a decomposition into two idealized phases, which can be exploited to capture matrix- and fiber-dominated responses at a high level of abstraction. The constitutive law of the matrix phase adopts a Continuum Damage approach driven by two Tsai-Wu surfaces, while a quasi-brittle behavior is attributed to the fibers phase. This decomposition effectively represents the influence of matrix degradation on the response and failure of the laminates. Moreover, simulations reveal that a statistical distribution of the strength is required to represent some of the experimental outcomes. The correlation with experimental data that was achieved points out that the technique is a promising tool for supporting the early design phase of CMC structures. [ABSTRACT FROM AUTHOR]

Rock damage model is of great significance to the forecast of rock failure in engineering design such as tunnel, drilling, stability of slope, and mine. However, the applicability of statistical damage constitutive models and efficient model selection criteria of rock have not been fully investigated, which leads to difficulties in resolving issues practice via employing models. In the paper, we developed a rock damage constitutive model based on power law distribution and investigated the corresponding applicability in describing rock damage behavior. The uniaxial compression tests for different rocks (e.g., sandstone, granite, mudstone, shale, and marble) are carried out to verify the applicability of the model, and the criterion for model selection is proposed based on the rock porosity strain ratio. The results show that the proposed model exhibits better performance in predicting variation for the brittle rock damage compared with the common damage model based on Weibull distribution. Besides, the applicability of the proposed model can be extended to elastic–plastic rock by adopting the sigmoid function. The research in this study provides an effective model to describe rock damage behavior for brittle and elastic–plastic and presents a criterion for model selection. [ABSTRACT FROM AUTHOR]

Different types of social infrastructure, such as roads and bridges, are essential and necessary for supporting our daily lives and economic operations. Because 39% of Japan's road bridges and 27% of its tunnels will have been in use for 50 years or more by 2023, maintaining them has become a significant national concern (Ministry of Land, Infrastructure, Transport and Tourism, White Paper on Land, Infrastructure, Transport and Tourism in Japan (2017), p. 114). Because of the declining birthrate, the deteriorating labor force, and the weakening local economy, the Japanese government must maintain these social infrastructures while facing severe budgetary challenges. And efficient and economical maintenance strategies and plans are required. This paper proposes optimal maintenance policies which consider the unique circumstances of social infrastructure and minimize maintenance costs. By applying these policies to wave-dissipating blocks in Japan, the effectiveness of them is confirmed. [ABSTRACT FROM AUTHOR]

In this study, the prediction of damage in the wire drawing process of 2011 aluminum alloy was investigated through both experimental and numerical methods. A comprehensive experimental setup was designed involving 20 cases of wire drawing with varying die angles ( 10 ° , 15 ° , 21 ° , 27 ° , and 34 ° ) and reductions (21%, 29%, 31%, and 38%). Each case was tested three times, and the drawing forces, as well as occurrences of wire breakage, were recorded. The mechanical behavior of the material was firstly characterized using uniaxial tensile tests, whose results were used to determine the material parameters of both the hardening Voce law and those of uncoupled and coupled damage models. Then, the numerical simulations of the wire drawing process were performed using a finite element model, accounting for axisymmetric conditions and mesh convergence analysis to ensure accuracy. The previously characterized damage models were applied to evaluate their fracture prediction capabilities. A novel presentation method using three-dimensional graphs was employed to indicate the level of damage for each angle and reduction, providing greater sensitivity and insight into the damage values. Good agreement between the experimental and numerical data was demonstrated for the bilinear coupled damage model, validating its effectiveness. This study contributes to a better understanding of damage prediction in the wire drawing process, with implications for improving industrial practices and material performance evaluations. [ABSTRACT FROM AUTHOR]

The effect of triaxiality on the evolution of damage in Al-2024 aluminum cylindrical specimens is studied in this work. Uncoupled and coupled damage models, all of them explicitly dependent on triaxiality, are assessed and compared. These models are characterized by tensile tests on cylindrical specimens without notches, to obtain the material parameters for each model. The capability of each model to predict fracture when different positive triaxial conditions evolve is then evaluated through tensile tests on notched cylindrical specimens. In particular, the damage index, evaluated at the fracture strain level, is compared with the experimental results validating the models. Moreover, the triaxiality evolution in the different specimens is studied in order to assess its effect on damage, demonstrating that the fracture strain decreases at greater triaxiality values. Observations through scanning electron microscopy confirm this pattern; i.e., an increase in triaxiality reveals a shift in the fracture mechanism from a more ductile condition in the original specimens to a more brittle one as the notch radius decreases. In addition, bilinear damage evolution is proposed to describe the physical behavior of the material when the Lemaitre coupled model is considered. In such a case, special attention must be devoted to the material characterization since coupling between hardening material parameters and damage affects the results. [ABSTRACT FROM AUTHOR]