Progressive Damage Research Articles

Climate Risk and Conservation Challenges at Palermo’s Specola Museum

The Specola Museum is housed on the premises of the old Palermo Observatory, founded in 1790, and preserves most of the observatory’s cultural heritage. Environmental monitoring following the activation of air conditioning systems in 2018 revealed significant deviations from the historic thermo-hygrometric trends, with particularly dangerous fluctuations in relative humidity. A notable example of the impact of these changes is a 19th-century painted wooden Model of Mars, displayed in the Merz Hall since 2021. In less than two years, the Model has shown progressive damage to its paint layers. Conservation actions have been adopted to stop the deterioration process, but the risk of further deterioration phenomena involving other objects is expected to increase substantially in the absence of intervention. This paper presents the outcomes of a preliminary study on the thermo-hygrometric conditions in the Merz Hall. Based on the European Standard EN 15757: 2010 and the Italian Legislative decree of 10 May 2001, safe ranges for temperature and relative humidity have been identified for the long-term preservation of the collection. These findings will inform future climate management strategies in the museum.

Взаимосвязь миокинов и саркопенического ожирения с неалкогольной жировой болезнью печени при конституционально-экзогенном ожирении у детей

Obesity in children is associated with high risk for development and progression of nonalcoholic fatty liver disease (NAFLD). NAFLD has common pathogenetic mechanisms with sarcopenic obesity (SO), in the development of which such myokines as fibroblast growth factor 21 (FGF-21) and irisin play an important role. The study of their secretion peculiarities is relevant to the prospects of using myokines as diagnostic markers or indicators for drug therapy and physical activity control as well as in the development of target therapy for NAFLD. The connection between NAFLD and SO and changes in myokine profile in children is an understudied issue. The purpose of this research was to determine differences between groups of pediatric patients with the presence v. those with the absence of NAFLD in constitutional-exogenous obesity in myokine and SO levels. Methods used: a single-stage comparative single-center uncontrolled study of 95 children aged 12 to 18 y/o with constitutional-exogenous obesity: body mass index (BMI) standard deviation score (SDS)≥+2.0. Results: NAFLD was detected in 48% (n=50/95) [95% CI (42; 63)] of whom steatohepatitis was detected in 40% (n=20/50) [95% CI (26; 55)]. SO was detected in 96% (n=48/50) [95% CI (86; 99)] with NAFLD including children with steatohepatitis (n=20). The combination of SO with elevated FRF-21 levels and decreased irisin was associated with NAFLD (AUC=0.761, [95% CI (0.65; 0.87)]). The SO frequency was statistically significantly higher in NAFLD than in the SO absence (p<0.001). The predictive ability of the SO presence in relation to the detection of NAFLD was found to be high (PCPR=96%, [95% CI (88; 99)]). FRF-21 values above 60 pg/mL (AUC=0.689, [95% CI (0.57; 0.81)]) and irisin values below 7.86 μg/mL (AUC=0.703, 95% CI (0.58; 0.82)]) were associated with the presence of NAFLD. When comparing operational characteristics, no differences were found for AUC value while the best performance was demonstrated by regression model and cut-off point of irisin equal to 7.86 μg/mL. Conclusion: SO combined with changes in myokine profile is associated with NAFLD. Identification of the main factors influencing the NAFLD development in childhood is crucial in preventing the progression of liver damage.

Effect of Panchavalkaladi Taila Yoni Pichu in the management of Paripluta Yoni Vyapad w.s.r. to Pelvic Inflammatory Disease - A Review Article

Health is an important factor that contributes to human well-being and economic growth. Wisdom, art, strength and wealth are no use if health is lacking. Nidation of seed will grow only in satisfactory environment. Creation of good offspring highly depends on the woman’s reproductive health. Yoni Shuddhta is one among the major essential for a healthy offspring. Twenty types of Yoni Vyapad mentioned as the major cause of disease of the female reproductive tract. Paripluta Yoni Vyapad is one of them and in this, Vata and Pitta Dosha is considered the primary cause. It can be correlated with Pelvic Inflammatory Disease. PID is a disease of the upper genital tract. The main clinical features of Pelvic inflammatory disease are purulent vaginal discharge with foul smell, fever, pelvic pain and dyspareunia. It affects approximately 10% of women of reproductive age. Delayed management of PID may result in higher rates of miscarriage, chronic pelvic pain, STD, progressive organ damage and long-term reproductive disability due to its recurrence. There is a need to solve this emerging problem. In modern medicine antimicrobials, analgesics, NSAIDs are often prescribed in the treatment of Pelvic inflammatory disease which can be cause of many sides effect as headache, dizziness, drowsiness etc. So, the proper solution is made to find the safe and curative remedy in the form of Panchvalkaladi Tail Yoni Pichu for Paripluta Yoni Vyapad.

Antioxidant and Ultrastructural Alterations in Wheat During Drought-Induced Leaf Senescence

Wheat is one of the most important crops to ensure food production globally. Understanding the mechanism of leaf senescence in wheat plays a crucial role in improving its productivity and resilience under various stress scenarios. In this study, we investigated biochemical, functional, and ultrastructural changes during leaf senescence in wheat genotypes with contrasting drought tolerance. For this, key parameters such as chlorophyll and total protein content, membrane stability, malondialdehyde level, and the activity of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, benzidine peroxidase, and catalase) were comparatively analyzed during both natural and drought-induced senescence. Additionally, the expression of superoxide dismutase isoform genes functioning in different cellular compartments was studied, alongside ultrastructural changes in flag leaves. The experiments involved genotypes of bread wheat (Triticum aestivum L.) and durum (Triticum durum Desf.) wheat. The plants were grown in controlled environment chambers under control and drought conditions using a completely randomized design. After the booting stage, irrigation was discontinued for drought-treated plants. Flag leaves were sampled at 7, 14, 21, 28, and 35 days after anthesis. Drought-tolerant genotypes exhibited slower chlorophyll degradation, lower lipid peroxidation, enhanced membrane stability, and stronger antioxidant responses, allowing them to maintain cellular function longer, whereas sensitive genotypes showed accelerated leaf senescence. Transcript levels of FeSOD increased significantly post-flowering but declined as senescence progressed, while MnSOD expression exhibited a rise towards the later stages of ontogenesis across all studied genotypes. Ultrastructural analysis revealed progressive damage to chloroplast membranes, thylakoid structures, and mesophyll cell walls under stress conditions, particularly in sensitive genotypes. These findings contribute to a deeper understanding of the physiological and molecular responses of wheat to drought stress, offering potential targets for improving crop performance in water-limited environments.

Damage and Failure Modeling of Composite Material Structures Using the Pam-Crash Code

Simulating composite material structures requires complex constitutive models, which normally require fine meshes to obtain an accurate prediction of their behavior. Pam-Crash software has been used for several years in the automotive industry and has been proved to be an efficient tool for simulating metallic structures, returning good correlations in a fast computational time. However, constitutive models for composite materials in Pam-Crash present some difficulties: some materials are not able to be suitably modeled and the predictive results depend on the mesh refinement. This work proposes a solution for predicting the progressive damage of composite materials in Pam-Crash, which scales the energy dissipated by the damage mechanisms and checks the viability of modeling the material behavior, taking into account the recommended size of finite elements in the automotive industry. The proposed solution is applied for the simulation of Open Hole specimens to evaluate the ultimate strength consistency. After this, it is applied for the simulation of Compact Tension specimens to check the consistency of crack propagation behavior. By considering the target size of the finite elements in the material card definition, the predictions demonstrate great improvement in the equivalence in results between different mesh refinements. Finally, the solution is applied to simulate impact tests on large structures. Good correlations with experimental data are obtained in fast computational times, making this methodology a candidate for application in composite-related automotive simulations.

Different Therapeutic Approaches for Dry and Wet AMD.

Age-related macular degeneration (AMD) is the most common cause of irreversible loss of central vision in elderly subjects, affecting men and women equally. It is a degenerative pathology that causes progressive damage to the macula, the central and most vital part of the retina. There are two forms of AMD depending on how the macula is damaged, dry AMD and wet or neovascular AMD. Dry AMD is the most common form; waste materials accumulate under the retina as old cells die, not being replaced. Wet AMD is less common, but can lead to vision loss much more quickly. Wet AMD is characterized by new abnormal blood vessels developing under the macula, where they do not normally grow. This frequently occurs in patients who already have dry AMD, as new blood vessels are developed to try to solve the problem. It is not known what causes AMD to develop; however, certain risk factors (i.e., age, smoking, genetic factors) can increase the risk of developing AMD. There are currently no treatments for dry AMD. There is evidence that not smoking, exercising regularly, eating nutritious food, and taking certain supplements can reduce the risk of acquiring AMD or slow its development. The main treatment for wet AMD is inhibitors of VEGF (vascular endothelial growth factor), a protein that stimulates the growth of new blood vessels. VEGF inhibitors can stop the growth of new blood vessels, preventing further damage to the macula and vision loss. In most patients, VEGF inhibitors can improve vision if macular degeneration is diagnosed early and treated accordingly. However, VEGF inhibitors cannot repair damage that has already occurred. Current AMD research is trying to find treatments for dry AMD and other options for wet AMD. This review provides a summary of the current evidence regarding the different treatments aimed at both forms of AMD with particular and greater attention to the dry form.

Particle flow simulation of fracture responses and anchoring mechanisms of cemented materials subjected to static-dynamic combined loads

This study aims to reveal the evolution of energy, cracks, force chain, and ultimate failure modes of cemented gangue backfill materials subjected to static-dynamic combined loads, as well as the reinforcement mechanisms of pre-tightening bolts on mechanical performance and progressive damage. The particle flow models with various fractal dimensions (D) of particle size distribution were established, and irreversible damage accumulation during dynamic loading was achieved through a nonlinear parallel-bonded stress corrosion model. The simulation results show that, compared to uniaxial compression, the energy release lag at peak strength is eliminated under static-dynamic combined loading, and the brittle failure feature becomes more pronounced. The filling effect of fine aggregates optimizes the uniformity of internal stress distribution, with the peak parallel bond strain energy increasing by 9.60%, 8.42%, and 14.81% as D increases from 2.1 to 2.85. At initial dynamic loading, the instantaneous increase in axial stress reaches the crack initiation stress, significantly increasing the number of tensile cracks. As pre-static load increases, the model sample is subjected to a higher internal stress environment during dynamic loading, leading to more remarkable force chain breakage observed at peak strength. Shear failure, including oblique shear failure and tensile-shear mixed failure, is the primary failure mode under static-dynamic combined loading. The additional constraints provided by bolts increase strain energy stored in particles and contacts and reduce the crack number at peak strength, with the constraining effect exhibiting more pronounced as preload increases. For anchored samples, the end of pallets is the initiation point for shear cracks, which extend along the edge of the preload concentration area, while tensile cracks initiating from the sample ends propagate toward the preload concentration area.

Management of Chronic Kidney Disease through Ayurvedic Shodhana and Shamana Chikitsa: A Case Report

Chronic Kidney Disease (CKD) has become a major public health issue affecting both younger and older individuals. The prevalence of CKD is on the rise, primarily driven by conditions such as hypertension and type 2 diabetes mellitus. CKD is characterised by progressive and irreversible damage to the kidneys, often presenting asymptomatically in its early stages. As the disease advances, patients may experience symptoms such as pedal oedema, decreased appetite, nausea, reduced urine output, frothy urine and fatigue. Laboratory tests typically show increased levels of creatinine and serum urea, indicating poor renal function. Traditional treatments, including dialysis and renal transplantation, remain mainstream approaches for managing CKD. However, these interventions are often financially prohibitive for many individuals in India, underscoring the urgent need for more affordable and accessible alternatives. In response to these challenges, Ayurvedic medicine offers promising alternative treatments. Hereby, the authors present a case of a 30-year-old male suffering from CKD; despite being recommended for dialysis, the patient opted for Ayurvedic treatment. Ayurvedic Shodhana chikitsa (purification and rejuvenating therapy) through Basti (therapeutic enema) combined with oral herbomineral formulations has demonstrated renoprotective effects and potential benefits in improving haematological parameters in CKD cases. The present case report highlights the importance of traditional Ayurvedic approaches as alternatives to prevent dialysis for CKD patients, particularly in low-income populations.

Effect of fiber breakage defect and waviness defect on compressive fatigue behavior and damage evolution of 3D multiaxial braided composites

This paper reports the effects of fiber breakage defects and waviness defects on the compressive fatigue behavior and the progressive damage evolution process of 3D Multiaxial Braided Composites (3DMBCs). Combined with finite element compression simulation and ultra-depth microscope, the internal defect content of composites with different braiding angles was determined. The results demonstrate that the weakening effect of waviness and fiber breakage defects is greater than the strengthening effect of the braiding angle. This causes the fatigue resistance of 3DMBCs with the 31° braiding angle being better in both directions of 0° and 90°. The increase of 4° waviness and 10% fiber breakage defect results in the average fatigue life of composites being shortened by 48% and the energy consumption rate increased by 10% at 85% stress level in the 90° compression direction. The alteration in loading direction modifies the included angle corresponding to the stress component. The stress component parallel to the fiber direction under compressive fatigue load leads to interfacial debonding in the composites, whereas the stress component perpendicular to the fiber direction results in pronounced shear failure.

INVESTIGATION OF IMPACT PERFORMANCE OF CYLINDER CORRUGATED SANDWICH STRUCTURES WITH DIFFERENT GEOMETRIC CONFIGURATIONS

The aim of this study is to numerically investigate and compare the impact performance of CFRP composite cylinder sandwich structures with five different geometric configurations. The impact performances and damage types of composite cylinder structures for different core configurations were determined. The impact analyses were performed in LS DYNA finite element program using MAT-54 material model with Progressive damage analysis based on the combination of Hashin damage criterion, Cohesive zone model and Bilinear traction-separation law. Among the five different specimens in the study, the highest peak force (PF) value of 1.88 kN was obtained at impact point P2 of the Trapeozidal sandwich structure. The lowest value was obtained at P1 impact point in Triangular sandwich structure with 0.62 kN. The highest and lowest energy absorption efficiency occurred in the Triangular structure, 78% and 38% respectively. The PF value at P2 point is higher than P1. The effect of core support on PF is very important. Since point P1 is not supported by the core, it is determined that the deformation is larger than P2.

Experimental and numerical investigations on the mechanical behavior of composite pre-tightened tooth connection under impact loading

The composite Pre-Tightened Tooth Connection (PTTC) is characterized by high connection efficiency and large bearing capacity, specifically designed for use in fiber-reinforced polymer (FRP)-metal protective structures that are inherently subjected to impact loads. In this study, impact tests were performed on single- and double-tooth specimens under high-velocity impact loads using the Split Hopkinson Pressure Bar (SHPB) apparatus to investigate their impact behavior. Additionally, a progressive damage model was numerically developed and validated against the experimental results to examine the failure patterns and mechanisms of the PTTC. The effects of tooth depth, tooth length, number of teeth, and impact velocity on the impact behavior were also analyzed parametrically. The results indicated that the primary failure modes of the PTTC are ductile compression-shear failure and brittle shear failure. In cases of compression-shear failure, the bearing capacity is lower than that of shear failure; however, it exhibits superior energy absorption characteristics. Therefore, it is recommended that the PTTC be designed to facilitate compression-shear failure when subjected to high-velocity impact. The length, depth, and number of teeth significantly influence the failure mode, bearing capacity, and energy absorption of the PTTC. Adequate design attention should be given to these factors for applications involving impact loads.

Experimental and numerical investigation on the failure behaviors of laminates with various shaped cutouts under tensile loading

Composite structures in aircraft often contain many cutouts, and failure of these structures is prone to occur near the edge of cutouts. Therefore, the failure behaviors of laminates with various shaped cutouts should be carefully investigated. To this end, experiments and numerical simulations are employed to investigate this issue. The tensile tests of composite laminates with circular, elliptical, square, and rectangular cutouts were carried out. Digital image correlation was utilized to capture the strain fields around the cutout. Combining the strain failure criterion and the modified exponential damage variables a three-dimensional progressive damage model was established, which can accurately predict the peak loads of composite laminates with diverse cutouts. All errors between the experimental and numerical results are less than 10 %. The experimental and numerical results indicate that the shape of the cutout has a great influence on the peak loads. As the ratio of major axis to minor axis (a/b) is increased from 1 to 5, peak loads obviously increase for the laminates with elliptical cutouts. Experimental results show that the average peak load of the laminates with elliptical cutout (a/b = 4) is 20.0 % higher than that of the laminates with circular cutout (a/b = 1). The dispersed distribution of high strains near the edge of the cutout results in an improvement of bearing capacity. As the ratio of length to width (l/w) in rectangular cutouts is increased from 0.5 to 3, peak loads are also improved obviously, because experimental results show that the average peak load of the laminates with rectangular cutout (l/w = 0.5) is 12.3 % lower than that of the laminates with square cutout (l/w = 1). Therefore, to improve the peak loads, it is very necessary to select the proper ratios of a/b and l/w. The above conclusions can serve as a reference for the design of composite structures.

Simulation and multi-dimensional damage evolution analysis of detailed micro-model representing ancient brick masonry compressive behavior

To further investigate the crack propagation and damage evolution mechanisms of ancient masonry under uniaxial compression, this study employs numerical simulation techniques alongside laboratory experiments to characterize and predict both the apparent and internal cracking behaviors of ancient masonry, utilizing a detailed micro-model constructed from the constitutive equations governing brick blocks and mortar. The findings indicate that this comprehensive micro-model effectively replicates the crack development process. The microscopic damage evolution is delineated by distinct stages: initiation, propagation, penetration, and ultimate failure. Furthermore, the mesoscopic fracture degree serves as a quantitative measure for assessing the mesoscopic evolution of ancient masonry during damage events. An internal damage assessment model has been developed to intricately describe the crack propagation process from within to outside. Additionally, recognizing the inherent randomness and complexity associated with crack development, we introduce a fractal dimension index which significantly enhances tracking accuracy throughout all phases of crack progression. Concurrently, in conjunction with a progressive damage model, multi-faceted predictions and evaluations regarding crack development are conducted to provide an effective framework for understanding the damage processes affecting ancient masonry.

Fatigue life prediction of hybrid carbon-flax-epoxy laminates using progressive failure analysis and cohesive zone model

A 3D progressive fatigue damage model was incorporated into ABAQUS software to predict the fatigue life of hybrid carbon-flax-epoxy composites. A cohesive zone method was employed to simulate delamination damage at carbon/flax interface. To evaluate the accuracy of the finite element model, two different layups, namely, unidirectional [0–90C2/0 F6]S (UD) and angle-ply [0–90C2/(±45) F6]S (AP), consisting of 12 flax fibers layers (F) sandwiched between four woven carbon fibers layers (C) were created using hand lay-up technique and then placed in compression molding. There is a good agreement between experimental and predicted fatigue life. It was observed that the predicted fatigue life is reduced by about 14% by changing the void content from 0.38% to 3.83%. The finite element analysis revealed that the matrix in the flax region of the AP layup failed at 12% of fatigue life, followed by delamination at the carbon/flax interface, consistent with SEM results.

The Uncoupling of Disease Activity from Joint Structural Progression in Patients with Rheumatoid Arthritis Treated with Filgotinib.

While modern treatments can prevent progressive bone destruction in patients with rheumatoid arthritis (RA) achieving clinical remission, it is unclear whether residual clinical activity may cause or be associated with progressive joint damage. This post hoc analysis evaluated the association between clinical disease activity and structural progression in patients with RA treated with filgotinib (FIL) in FINCH 1 (NCT02889796). Patients with RA and inadequate response to methotrexate (MTX) use were randomized 3:3:2:3 to FIL 200mg (FIL200) or FIL 100mg (FIL100) once daily, adalimumab 40mg biweekly, or placebo, all with background MTX. We evaluated the change from baseline (CFB) in modified total Sharp score (mTSS), erosion score, and joint space narrowing score among patients achieving Clinical Disease Activity Index (CDAI) remission (CDAI ≤ 2.8), low disease activity (LDA; 2.8 < CDAI ≤ 10), medium disease activity (MDA; 10 < CDAI ≤ 22), and high disease activity (HDA; CDAI > 22) at 24weeks. At week 24, the least squares (LS) mean CFB in mTSS was similarly low across treatments among patients who achieved CDAI remission (range 0.00-0.11) or LDA (n = 285 and 575, respectively). In patients with MDA and HDA (n = 471 and 157, respectively), smaller LS mean CFB in mTSS was seen in the FIL200 group vs. the placebo group (P < 0.05 for both). RA clinical remission and LDA achievement were associated with suppressed progression of joint destruction over 24weeks in all treatment groups. Only FIL200 significantly inhibited joint damage compared with placebo in patients with MDA or HDA, indicating an uncoupling of clinical disease activity and structural progression in patients receiving FIL200. NCT02889796.

Infant skull fractures align with the direction of bone mineralization.

The geometry and mechanical properties of infant skull bones differ significantly from those of adults. Over the past decades, debates surrounding whether fractures in infants come from deliberate abuse or accidents have generated significant impacts in both legal and societal contexts. However, the etiology of infant skull fractures remains unclear, which motivates this study with two main components of work. Firstly, we present and implement a progressive unidirectional fabric composite damage model for infant cranial vaults to represent ductile and anisotropic properties-two typical mechanical characteristics of infant skulls. Secondly, we hypothesize that these intrinsic material properties cause injuries perpendicular to the fiber direction to dominate infant skull fractures, resulting in fracture lines that align with the direction of mineralization in the infant skull. The material model and the finite element (FE) model were verified hierarchically, and this hypothesis was verified by reconstructing two legal cases with known fall heights and implementing the above damage model into CT-based subject-specific infant FE head models. We discovered that the infant skull is more susceptible to injuries within planes perpendicular to the mineralization direction because of the anisotropic mechanical property caused by the direction of mineralization, leading to infant skull fractures aligning with the mineralization direction. Our findings corroborated the several previously reported observations of fractures on cranial vaults, demonstrating that these fractures were closely associated with sutures and oriented along the mineralization direction, and revealed the underlying mechanisms of infant skull fracture pattern. The modeling methods and results of this study will serve as an anchor point for more rigorous investigations of infant skull fractures, ultimately aiming to provide convincing biomechanical evidence to aid forensic diagnoses of abusive head trauma.

OXIDANTS AND BLOOD-RETINAL BARRIER: PROGRESSION AND MOLECULAR MECHANISMS OF DIABETIC RETINOPATHY

Diabetic retinopathy is a microvascular complication of the eye that arises as a consequence of poor control of hyperglycemia in patients with diabetes mellitus. This condition is characterized by progressive damage to the blood vessels of the retina, leading to increased vascular permeability, microaneurysms, intraretinal hemorrhages and, in more advanced stages, neovascularization. Depending on its degree of progression, it can be classified into a non-proliferative form, more frequent in the initial stages, and a proliferative form, which appears in advanced stages and is associated with a higher risk of severe visual loss. Regarding its pathophysiology, chronic hyperglycemia triggers a series of harmful metabolic and molecular pathways, such as the accumulation of reactive oxygen species, which cause oxidative stress and jointly contribute to endothelial damage and dysfunction of the blood-retinal barrier. Patients with this complication require strict and continuous glycemic control using hypoglycemic drugs capable of reducing the osmolar disturbances characteristic of diabetes, combined with specific ocular therapies such as endothelial growth factor inhibitors, which slow down neovascularization and consequently reduce the likelihood of blindness. However, even with treatment protocols, diabetic retinopathy remains the leading cause of blindness in adults worldwide, underlining the importance of prevention and early diagnosis. This study was based on the bibliographic method, collecting scientific medical data from specialized journals such as PUBMED and Scielo published between 2018 and 2023. The results highlight the close relationship between hyperglycemic states and diabetic retinopathy. Thus, it is concluded that it is essential to develop new therapies that attack not only the advanced symptoms of the disease, but also the early molecular changes that occur during the early stages of diabetic retinopathy, effectively combating the cause and effect of the pathology.

Modeling and analysis of failure initiation and progression of 3D braided composites: a multi-region multi-cell approach

Accurate modeling and analysis are keys to obtaining precise failure behavior of advanced composites with manufacturing details. However, existing models lack a unique shape and fail to account for the intricate yarn path and manufacturing nuances. The current work emphasizes multi-region-based multi-cell models to analyze the damage initiation and progression behavior of 3D braided polymer composites under tensile loading. The progressive damage model is applied with Hashin 3D UMAT and maximum stress failure criteria for the modeled fiber bundle and matrix in the finite element analysis framework. Also, the effects of the void are considered to incorporate manufacturing-induced variations. The damage initiation and progression results are shown with stress-strain curves and verified with existing literature. It is obtained that the observed damage varies according to the different regions of the composite structure. The significant advantage of the current work is that it emphasizes modeling and failure analysis that accounts for manufacturing intricacies, enabling accurate representation of complex advanced composites using a computationally efficient small-scale model. Results and discussions indicate that this approach can be utilized to predict the failure of 3D complex shape composites efficiently.

Study of bond-slip performance of steel tube with UHPC based on acoustic emission parameter analysis

Conventional methods for assessing bond performance are hindered by challenges in measuring strain and a lack of sufficient sensitivity to internal structural damage. This paper examines the bond behavior between steel and ultra-high-performance concrete (UHPC) based on acoustic emission (AE). The tests included a total of 2 concrete-filled steel tube (CFST) specimens and 4 concrete-encased CFST specimens. The bonding test was analyzed using AE parameters in combination with the damage process, damage morphology, and loading curve of the test specimens. Furthermore, damage correspondence was explored for the AE parameter indexes and the bond damage indexes of the conventional method. The findings reveal that the AE peak frequencies associated with the bond failure between steel tube and concrete span 30–100 kHz, 110–130 kHz, and 220–260 kHz. The AE event rate, cumulative absolute energy, Ib-curve, and percentage of tensile cracks can be used as judgmental and early warning features for interface damage. The damage process at the interface and the concrete crack development can be characterized by the severity index HI and the severity value Sr. The measurement curves obtained from various AE sensor positions exhibit remarkable similarity. A correlation can be discerned between the severity index (Sr) of the AE and the bond damage degree (Dt) ascertained through conventional methods, effectively mirroring the structural damage progression.

Exploring the role of sample size on fracture growth mechanisms in intact rock: Insights from 3D DEM-DFN analysis

The effect of sample size on the deformation characteristic and fracture growth mechanism of intact rock subjected to unconfined compressive stress state is examined in this study via discrete element method coupled with discrete fracture network. Three-dimensional numerical models are first developed based on reported laboratory experiments and verified to realistically replicate the effect of sample size on the macro-mechanical response of the intact rock. This includes strength behavior, fracturing activities and energy budgets. Micromechanical analyses are then performed to understand the role of sample size on the deformational behavior and damage progression in intact rock. Emphasis is placed on the distributions of coordination number, evolutions of crack density and the degree of crack anisotropy with regard to invariants of crack tensors. Results reveal that deformability and strength of intact rock are vastly reliant on the sample size. Increasing sample size facilitate the accumulation of induced microcracks due to the increased probability of interparticle bond failure. It is found that the increase in sample size can result in more tensile openings with strong dilatancy. Finally, the monotonical increase in seismic b-values with the increase in sample size suggests an acceleration in the number of small-magnitude AE events.