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1.
Ecotoxicol Environ Saf ; 276: 116270, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38574645

RESUMEN

Mycotoxin contamination has become a major food safety issue and greatly threatens human and animal health. Patulin (PAT), a common mycotoxin in the environment, is exposed through the food chain and damages the gastrointestinal tract. However, its mechanism of enterotoxicity at the genetic and metabolic levels remains to be elucidated. Herein, the intestinal histopathological and biochemical indices, transcriptome, and metabolome of C57BL/6 J mice exposed to different doses of PAT were successively assessed, as well as the toxicokinetics of PAT in vivo. The results showed that acute PAT exposure induced damaged villi and crypts, reduced mucus secretion, decreased SOD and GSH-Px activities, and enhanced MPO activity in the small intestine and mild damage in the colon. At the transcriptional level, the genes affected by PAT were dose-dependently altered in the small intestine and fluctuated in the colon. PAT primarily affected inflammation-related signaling pathways and oxidative phosphorylation in the small intestine and immune responses in the colon. At the metabolic level, amino acids decreased, and extensive lipids accumulated in the small intestine and colon. Seven metabolic pathways were jointly affected by PAT in two intestinal sites. Moreover, changes in PAT products and GST activity were detected in the small intestinal tissue but not in the colonic tissue, explaining the different damage degrees of the two sites. Finally, the integrated results collectively explained the toxicological mechanism of PAT, which damaged the small intestine directly and the colon indirectly. These results paint a clear panorama of intestinal changes after PAT exposure and provide valuable information on the exposure risk and toxic mechanism of PAT.


Asunto(s)
Metabolómica , Ratones Endogámicos C57BL , Patulina , Transcriptoma , Animales , Patulina/toxicidad , Ratones , Transcriptoma/efectos de los fármacos , Masculino , Intestino Delgado/efectos de los fármacos , Intestino Delgado/patología , Intestino Delgado/metabolismo , Mucosa Intestinal/efectos de los fármacos , Mucosa Intestinal/metabolismo , Colon/efectos de los fármacos , Colon/patología , Intestinos/efectos de los fármacos , Intestinos/patología
2.
Lasers Med Sci ; 37(3): 1503-1514, 2022 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-34562156

RESUMEN

The 755-nm Alexandrite Laser has a good clinical effect in treating resistant port wine stain, without causing thermal damage of normal tissue and side effects such as purpura. However, little is known about the mechanism of vascular damage induced by 755-nm laser irradiation, which restricts the optimization of laser parameters. In this work, the thermal damage model and the pressure damage model were used to study the damage mechanism of 755-nm laser irradiation on vessels, and the incident energy density and pulse width required for vascular damage were determined according to the damage mode. Under the irradiation of 755-nm laser, the vascular injury pattern was the co-occurrence of vessel rupture and vessel constriction, and the energy density required for the treatment of vessels with a diameter of 200 µm to reach the damage threshold was the lowest.


Asunto(s)
Terapia por Láser , Láseres de Estado Sólido , Mancha Vino de Oporto , Humanos , Láseres de Estado Sólido/efectos adversos , Modelos Teóricos , Mancha Vino de Oporto/cirugía
3.
Exp Brain Res ; 239(4): 1247-1260, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33599834

RESUMEN

The objective of this study is to analyze the differential protein expression profile in cerebral cortex of rats with middle cerebral ischemia/reperfusion (MCAO/R), explore the brain damage mechanism of MCAO/R at protein level, and provide experimental foundation for searching specific marker proteins of MCAO/R. Rat model of MCAO/R was established by modified suture-occluded method, and the model was evaluated by the results of brain 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin-eosin (HE) staining. Cerebral cortex of rats from sham-operated group (Sham) and MCAO/R groups was used for FASP enzymatic hydrolysis, i-TRAQ quantitative labeling, and reverse-phase liquid chromatography purification and separation. Orbitrap Q Exactive mass spectrometry was used for qualitative and quantitative analyses of total differential protein expression profiles. MCAO/R rats had obvious cerebral infarction lesions, and the relative surface area of cerebral infarction was significantly different compared with sham rats, suggesting that MCAO/R rat model was successfully prepared. There were 199 significant difference proteins (MCAO/R vs Sham, p < 0.05, |fold change|> 1.2), including 104 up-regulated proteins and 95 down-regulated proteins. Gene ontology (GO) enrichment analysis showed that the up-regulated proteins were mainly concentrated in the biological processes of positive regulation of NF-κB transcription and I-κB kinase-NF-κB, etc. Down-regulated proteins were mainly concentrated in long-term synaptic potentiation, cellular response to DNA damage stimulus, etc. KEGG pathway analysis showed that the pathway involved in differential proteins includes oxidative phosphorylation, metabolic pathway, and Ras signaling pathway. Network analysis of differential proteins showed that Alb, ndufb5, ndufs7, ApoB, Cdc42, Ndufa3, Igf1r, P4hb, Mbp, Gc, Nme1, Akt2, and other proteins may play an important role in regulating oxidative stress, apoptosis, and inflammatory response in MCAO/R. Quantitative proteomics based on i-TRAQ labeling reveals the effect of inflammation and apoptosis in brain damage mechanism of MCAO/R. Besides, this research provide some experimental foundation for search and determination of potential therapeutic targets of MCAO/R.


Asunto(s)
Isquemia Encefálica , Daño por Reperfusión , Animales , Encéfalo , Corteza Cerebral , Infarto de la Arteria Cerebral Media , Proteómica , Ratas , Reperfusión
4.
Proc Natl Acad Sci U S A ; 115(3): 483-488, 2018 01 16.
Artículo en Inglés | MEDLINE | ID: mdl-29284751

RESUMEN

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial-temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (µXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem µXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands. Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through µXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials.

5.
Sensors (Basel) ; 21(13)2021 Jun 25.
Artículo en Inglés | MEDLINE | ID: mdl-34202169

RESUMEN

Carbon Fibre-Reinforced Polymers (CFRPs) in aerospace applications are expected to operate in moist environments where carbon fibres have high resistance to water absorption; however, polymers do not. To develop a truly optimised structure, it is important to understand this degradation process. This study aims to expand the understanding of the role of water absorption on fibrous/polymeric structures, particularly in a matrix-dominant property, namely interlaminar strength. This work used Acoustic Emission (AE), which could be integrated into any Structural Health Monitoring System for aerospace applications, optical strain measurements, and microscopy to provide an assessment of the gradual change in failure mechanisms due to the degradation of a polymer's structure with increasing water absorption. CFRP specimens were immersed in purified water and kept at a constant temperature of 90 °C for 3, 9, 24 and 43 days. The resulting interlaminar strength was investigated through short-beam strength (SBS) testing. The SBS values decreased as immersion times were increased; the decrease was significant at longer immersion times (up to 24.47%). Failures evolved with increased immersion times, leading to a greater number of delaminations and more intralaminar cracking. Failure modes, such as crushing and multiple delaminations, were observed at longer immersion times, particularly after 24 and 43 days, where a pure interlaminar shear failure did not occur. The observed transition in failure mechanism showed that failure of aged specimens was triggered by a crushing of the upper surface plies leading to progressive delamination at multiple ply interfaces in the upper half of the specimen. The crushing occurred at a load below that required to initiate a pure shear failure and hence represents an under prediction of the true SBS of the sample. This is a common test used to assess environmental degradation of composites and these results show that conservative knockdown factors may be used in design. AE was able to distinguish different material behaviours prior to final fracture for unaged and aged specimens suggesting that it can be integrated into an aerospace asset management system. AE results were validated using optical measurements and microscopy.


Asunto(s)
Polímeros , Agua , Acústica , Temperatura
6.
Molecules ; 26(4)2021 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-33672940

RESUMEN

Pseudomonas is considered as the specific spoilage bacteria in meat and meat products. The purpose of this study was to evaluate the inactivation efficiency and mechanisms of slightly acidic electrolyzed water (SAEW) against Pseudomonas deceptionensis CM2, a strain isolated from spoiling chicken breast. SAEW caused time-dependent inactivation of P. deceptionensis CM2 cells. After exposure to SAEW (pH 5.9, oxidation-reduction potential of 945 mV, and 64 mg/L of available chlorine concentration) for 60 s, the bacterial populations were reduced by 5.14 log reduction from the initial load of 10.2 log10 CFU/mL. Morphological changes in P. deceptionensis CM2 cells were clearly observed through field emission-scanning electron microscopy as a consequence of SAEW treatment. SAEW treatment also resulted in significant increases in the extracellular proteins and nucleic acids, and the fluorescence intensities of propidium iodide and n-phenyl-1-napthylamine in P. deceptionensis CM2 cells, suggesting the disruption of cytoplasmic and outer membrane integrity. These findings show that SAEW is a promising antimicrobial agent.


Asunto(s)
Ácidos/farmacología , Membrana Celular/patología , Electrólisis , Viabilidad Microbiana/efectos de los fármacos , Pseudomonas/efectos de los fármacos , Agua/farmacología , Membrana Celular/efectos de los fármacos , Membrana Celular/ultraestructura , Permeabilidad de la Membrana Celular/efectos de los fármacos , Citoplasma/efectos de los fármacos , Desinfección , Pseudomonas/citología , Pseudomonas/ultraestructura
7.
Fa Yi Xue Za Zhi ; 36(4): 545-548, 2020 Aug.
Artículo en Inglés, Zh | MEDLINE | ID: mdl-33047541

RESUMEN

ABSTRACT: Cantharidin poisoning has been proven to cause multiple organ damage. Acute circulatory failure, acute renal failure, and multiple organ failure resulting from cantharidin poisoning are the main causes of death for patients with cantharidin poisoning. However, research on the damage of main target organs and mechanism of cantharidin poisoning is not clear. This paper reviews the latest toxicological and pathological research literatures at home and abroad related to cantharidin poisoning and comprehensively summarizes the latest research progress on the toxicological and pathological damage and mechanism of the digestive system, circulatory system, respiratory system, urinary system, reproductive system, skin mucosa, immune system, and nervous system after cantharidin poisoning, to provide reference for improving the molecular toxicological mechanism of cantharidin poisoning and decision-making in the clinical intervention of cantharidin poisoning.


Asunto(s)
Cantaridina , Intoxicación , Humanos
8.
Fa Yi Xue Za Zhi ; 36(2): 181-186, 2020 Apr.
Artículo en Inglés, Zh | MEDLINE | ID: mdl-32530164

RESUMEN

ABSTRACT: Objective To study the mechanism of rib fracture caused by landing on different parts of the trunk using finite element method, and to provide some new techniques and new ideas for the reconstruction of the whole process of falls from height. Methods The finite element method was used to study the rib fracture of human security model THUMS4.0 caused by landing on different parts of the trunk. Then the model was compared with actual cases and the mechanism of rib fracture caused by falls from height was analyzed from a biomechanical point of view. Results There were some differences in the stress and strain distribution as well as the rib fracture sites when different parts touched the ground. Ribs on both sides of the body were fractured when the front of the trunk touched the ground, and the fractures were mainly located in the junction of the ribs and costal cartilage and the midaxillary line area. When the right anterior part of the trunk touched the ground, rib fracture occurred first on the side that touched the ground, and rib fractures were mainly located in the area from the right midaxillary line to the posterior axillary line, and junction of ribs on both sides and costal cartilage. When the back of the trunk touched the ground, the fracture sites were mainly located on the back of the ribs on both sides. When the right posterior part of the trunk touched the ground, multiple rib fractures were likely to occur in the parts that touched the ground. The plastic strains were mainly concentrated at the fracture sites, while the von Mises stresses were not only concentrated at the fracture sites, but also at other sites. Conclusion There are some differences in rib fracture location sites and injury mechanisms when different parts of the trunk touch the ground.


Asunto(s)
Fracturas de las Costillas , Accidentes por Caídas , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Fracturas de las Costillas/etiología , Costillas , Torso
9.
Zhongguo Zhong Yao Za Zhi ; 44(16): 3406-3414, 2019 Aug.
Artículo en Zh | MEDLINE | ID: mdl-31602902

RESUMEN

This paper summarizes the research progress of reproductive toxicity of Tripterygium wilfordii from 1979,and the toxicity characterization,damage mechanism,and attenuated measures are summarized. It was found that,the reproductive toxicity caused by T. wilfordii is mainly distributed on components of Tripterygium glycosides,triptolide,tripchlorolide,and clinically preparations,such as Leigongteng Tablets and Tripterygium Glycosides Tablets. Adverse reactions to male reproductive system caused by Tripterygium preparations mainly include decreased sperm motility,oligospermia or spermatozoa,decreased fertility or infertility,etc. Long-term drug use may also lead to testicular atrophy and decreased sexual desire. Adverse reactions to women are mainly manifested as menstrual disorders,decreased menstrual volume or even amenorrhea,decreased sexual desire,infertility,etc. The reproductive toxicity of T. wilfordii is related to apoptosis of reproductive cells,disturbance of spermatogenesis or oogenesis,damage of testis and ovary in reproductive target tissues,and changes of internal environment in gonad tissues( hormones,hormone synthesis rate-limiting enzymes and energy metabolism). Drug compatibility,hormone replacement,medication duration and dosage form changes can help reduce the damage of T. wilfordii to the reproductive system. In addition,in view of the existing problems in the current study,the author proposes new directions in clinical studies,pharmacological metabolism mechanism,preparation quality standards and new therapeutic effects,etc.,to provide a basis for the safe and reasonable clinical application of T. wilfordii.


Asunto(s)
Medicamentos Herbarios Chinos/toxicidad , Genitales/efectos de los fármacos , Tripterygium/toxicidad , Femenino , Humanos , Masculino , Ovario/efectos de los fármacos , Testículo/efectos de los fármacos
10.
J Occup Environ Hyg ; 13(12): 924-935, 2016 12.
Artículo en Inglés | MEDLINE | ID: mdl-27224852

RESUMEN

Asbestos amosite fibers were investigated to evaluate the damage caused by a transmission electron microscope (TEM) electron beam. Since elemental x-ray intensity ratios obtained by energy dispersive x-ray spectroscopy (EDS) are commonly used for asbestos identification, the impact of beam damage on these ratios was evaluated. It was determined that the magnesium/silicon ratio best represented the damage caused to the fiber. Various tests showed that most fibers have a current density threshold above which the chemical composition of the fiber is modified. The value of this threshold current density varied depending on the fiber, regardless of fiber diameter, and in some cases could not be determined. The existence of a threshold electron dose was also demonstrated. This value was dependent on the current density used and can be increased by providing a recovery period between exposures to the electron beam. This study also established that the electron beam current is directly related to the damage rate above a current density of 165 A/cm2. The large number of different results obtained suggest, that in order to ensure that the amosite fibers are not damaged, analysis should be conducted below a current density of 100 A/cm2.


Asunto(s)
Asbesto Amosita/química , Asbesto Amosita/efectos de la radiación , Microscopía Electrónica de Transmisión/métodos , Magnesio , Silicio/química , Espectrometría por Rayos X/métodos
11.
Artículo en Inglés | MEDLINE | ID: mdl-26865010

RESUMEN

Most of our previous studies reported aluminum causes no cell damage or lysis, and no subsequent toxin release in conventional treatment of drinking water or in the laboratory, on the contrary, we investigated the effect of long-term and large-dose alum treatment, because the environmental conditions in lakes and treatment plants are widely different. The microcosm experiments were designed to simulate the effect of adding alum under the similar conditions of common lakes and reservoirs, and the bottle experiments were conducted to examine the budget or dynamics of microcystin after adding alum. In precipitate analyses, we also confirm the release and dynamics of microcystin and the damage mechanisms of Microcystis cells under alum treatment. In microcosms treated with alum alone, the extracellular microcystin-LR (MC-LR) concentration increased to approximately 82% in 7 days. Similar results were obtained in bottle experiments. By plotting the concentration of released microcystin over time, we inferred that the extracellular MC-LR concentration exponentially rose toward an asymptotic maximum. Moreover, in scanning electron microscope images, some cells exhibited torn membranes with miniscule traces of aluminum hydroxide coating. We conclude that alum treatment, particularly at maximum dosage administered over long periods, seriously damages Microcystis cells and induces microcystin release. Therefore, long-term application of large alum doses is not recommended as an in-lake treatment.


Asunto(s)
Compuestos de Alumbre/toxicidad , Muerte Celular/efectos de los fármacos , Agua Potable/química , Lagos/microbiología , Microcistinas/metabolismo , Microcystis/efectos de los fármacos , Microcystis/metabolismo , Purificación del Agua/métodos
12.
Electromagn Biol Med ; 35(1): 84-101, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-25356665

RESUMEN

Systems emitting ultra-wideband high power microwave (HP/UWB) pulses are developed for military and civilian applications. HP/UWB pulses typically have durations on the order of nanoseconds, rise times of picoseconds and amplitudes around 100 kV m(-1). This article reviews current research on biological effects from HP/UWB exposure. The different references were classified according to endpoints (cardiovascular system, central nervous system, behavior, genotoxicity, teratology …). The article also reviews the aspects of mechanisms of interactions and tissue damage as well as the numerical work that has been done for studying HP/UWB pulse propagation and pulse energy deposition inside biological tissues. The mechanisms proposed are the molecular conformation change, the modification of chemical reaction rates, membrane excitation and breakdown and direct electrical forces on cells or cell constituents, and the energy deposition. As regards the penetration of biological matter and the deposited energy, mainly computations were published. They have shown that the EM field inside the biological matter is strongly modified compared to the incident EM field and that the energy absorption for HP/UWB pulses occurs in the same way as for continuous waves. However, the energy carried by a HP/UWB pulse is very low and the deposited energy is low. The number of published studies dealing with the biological effects is small and only a few pointed out slight effects. It should be further noted that the animal populations used in the studies were not always large, the statistical analyses not always relevant and the teams involved in this research rather limited in number.


Asunto(s)
Absorción de Radiación , Microondas , Radiobiología/métodos , Animales , Humanos , Microondas/efectos adversos , Modelos Biológicos , Radiometría
13.
Materials (Basel) ; 17(12)2024 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-38930188

RESUMEN

To investigate the influence of water content on the rockburst phenomena in tunnels with horizontal joints, experiments were conducted on simulated rock specimens exhibiting five distinct levels of water absorption. Real-time monitoring of the entire blasting process was facilitated through a high-speed camera system, while the microscopic structure of the rockburst debris was analyzed using scanning electron microscopy (SEM) and a particle size analyzer. The experimental findings revealed that under varying degrees of water absorption, the specimens experienced three stages: debris ejection; rockburst; and debris spalling. As water content increased gradually, the intensity of rockburst in the specimens was mitigated. This was substantiated by a decline in peak stress intensity, a decrease in elastic modulus, delayed manifestation of pre-peak stress drop, enhanced amplitude, diminished elastic potential energy, and augmented dissipation energy, resulting in an expanded angle of rockburst debris ejection. With increasing water content, the bond strength between micro-particles was attenuated, resulting in the disintegration of the bonding material. Deformation failure was defined by the expansion of minuscule pores, gradual propagation of micro-cracks, augmentation of fluffy fine particles, exacerbation of structural surface damage akin to a honeycomb structure, diminishment of particle diameter, and a notable increase in quantity. Furthermore, the augmentation of secondary cracks and shear cracks, coupled with the enlargement of spalling areas, signified the escalation of deformation failure. Simultaneously, the total mass of rockburst debris gradually diminished, accompanied by a corresponding decrease in the proportion of micro and fine particles within the debris.

14.
Materials (Basel) ; 17(4)2024 Feb 19.
Artículo en Inglés | MEDLINE | ID: mdl-38399213

RESUMEN

Carbon/Carbon (C/C) composites exhibit excellent mechanical properties at high temperatures, making them widely used in aerospace, such as the leading edges of spaceplane wings and the nose cones of hypersonic aircraft. However, damage caused by rain erosion to C/C composites affects their mechanical properties and poses significant challenges during operational service periods. A jet impingement test platform was employed to conduct single and multiple water-jet erosion tests on three-dimensional orthogonal C/C composite materials and to investigate the residual mechanical properties of the specimens after jet impact. The damage was characterized using optical microscopy, scanning electron microscopy, and X-ray computed tomography. The results showed that the damage types of the C/C composite materials under water-jet impingement included fiber bundle fracturing, delamination, and debonding. The extent of erosion damage was positively correlated with the jet velocity and diameter. The changes in the multi-jet damage indicated a cumulative expansion process, and z-directional fiber bundles exhibited superior resistance to jet impact damage propagation. The results of the three-point bending tests showed that the greater the initial impact damage, the lower the residual mechanical properties of the materials, and the residual strength of the specimen suddenly decreased when damage occurred at the back of the specimen.

15.
Materials (Basel) ; 17(8)2024 Apr 18.
Artículo en Inglés | MEDLINE | ID: mdl-38673236

RESUMEN

Aluminum matrix composites (AMMCs) have demonstrated substantial potential in the realm of armor protection due to their favorable properties, including low density, high specific stiffness, and high specific strength. These composites are widely employed as structural components and frequently encounter high strain rate loading conditions, including explosions and penetrations during service. And it is crucial to note that under dynamic conditions, these composites exhibit distinct mechanical properties and failure mechanisms compared to static conditions. Therefore, a thorough investigation into the dynamic mechanical behavior of aluminum matrix composites and precise constitutive equations are imperative to advance their application in armor protection. This review aims to explore the mechanical properties, strengthening the mechanism and deformation damage mechanism of AMMCs under high strain rate. To facilitate a comprehensive understanding, various constitutive equations are explored, including phenomenological constitutive equations, those with physical significance, and those based on artificial neural networks. This article provides a critical review of the reported work in this field, aiming to analyze the main challenges and future development directions of aluminum matrix composites in the field of protection.

16.
Heliyon ; 10(2): e24482, 2024 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-38293484

RESUMEN

The research object is diorite in the Lingbei TBM section of the Hanjiang-To-Weihe River Qinling tunnel, with a buried depth of over 1 km. Using MTS-2000 microcomputer-controlled electro-hydraulic servo universal testing machine and DS5-16b acoustic emission (AE) monitoring system, uniaxial compression and acoustic emission monitoring tests were carried out on rock samples, to study the uniaxial compression mechanical properties and acoustic emission characteristics of the deep diorite. The results of the study indicate that: (1) During uniaxial compression, diorite undergoes four stages: initial compaction, elasticity, yield and failure, in which the curve of the initial compaction stage is significantly smoother. The uniaxial compressive strength is 41.95 MPã102.42 MPa, with an average of 74.07 Mpa; The axial peak strain ranges from 1 % to 1.4 %, and the failure mode belongs to brittle ductile splitting failure. (2) The cumulative ringing count and energy showed a very slow increase trend during the calm period; After entering a surge period (with the appearance of Kaiser points), both show a significant transition state; During the slow increase period, the overall growth rate of the two slowed down and remained almost silent. (3) On the basis of the analysis of RA-AF values during the deformation and rupture process of diorite, it can be seen that the damage type of diorite is tensile damage by the significant low RA value and high AF value characteristics, which coincides with the actual damage fracture characteristics of the rocks in the sample. (4) During the compaction stage, there are few acoustic emission location points, which correspond to low energy and are mainly distributed at the higher and lower ends of the sample; After entering the elasticity stage, the number of positioning points significantly increases and gradually expands towards the middle; Near Kaiser point, the number of location points and corresponding energy are both in a sharp increase state, and this trend is in good agreement with the changes in the ringing count-time and energy-time curves. (5) The damage time mainly starts at the end of the calm period, and the pattern of change in the damage curve coincides with the localization point and energy evolution. The results of the research can be used as a referential basis for the development of the excavation, protection and other construction plans for the Lingbei TBM section of the Hanjiang-To-Weihe River Qinling tunnel or similar surrounding rock tunnels, as well as for further conducting triaxial unloading tests on diorite.

17.
Materials (Basel) ; 17(12)2024 Jun 13.
Artículo en Inglés | MEDLINE | ID: mdl-38930257

RESUMEN

This study concerned the in situ investigation of the defect evolution and fracture mechanism of additively manufactured (AM) Ti-6Al-4V under uniaxial tensile tests. In order to achieve this, microstructure characterization was initially carried out in order to identify the defects within the matrix of the candidate material. In situ testing was then performed, focusing on the spherical defect to observe its evolution under tensile loading. It was found that, before the fracture stage, the geometric evolution of the spherical defect towards an ellipse shape was dominated by the load in the tensile direction. In addition, the slip band density was found to be aggravated near the spherical defect due to the geometric discontinuity-induced stress concentration. During the fracture process, the defect geometry evolved as an irregular shape, which was mainly attributed to the micro-void-induced localized multi-axial stress state. The fracture analysis indicated that defects play a key role in crack initiation, leading to the fracture of LPBF materials.

18.
Materials (Basel) ; 17(13)2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-38998291

RESUMEN

Carbon fiber reinforced polymer (CFRP) tendons are composite materials that offer significant advantages in terms of tensile strength and lightweight properties. They are being increasingly utilized in the construction industry, particularly in bridge cables and building structures. However, due to their relatively poor transverse mechanical properties compared to steel cables, securing these tendons with anchors presents a challenge. This paper reviews the structure and force characteristics of three types of anchors for CFRP tendons-clamping anchorage, bonded anchorage, and composite anchorage-analyzes and summarizes the anchorage characteristics and damage mechanisms of each type of anchorage, and highlights that the optimization of the mechanical properties of the tendons is key to the design and research of anchoring systems. The new composite anchorage offers comprehensive advantages, such as minimal tendon damage at the anchorage section, more uniform stress distribution, and better anchorage performance, despite being more complex in design compared to single-type anchorages. However, there remain challenges and research gaps in testing and validating these anchoring systems under realistic loading and environmental conditions, including impacts, cyclic stresses, humidity, and high temperatures. Future efforts should focus on developing new testing techniques and models to simulate real-world conditions, enabling more accurate assessments of anchorage performance and longevity. By doing so, we can fully harness the mechanical properties of CFRP tendons and further enhance the safety and efficiency of our built environment.

19.
Materials (Basel) ; 17(15)2024 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-39124429

RESUMEN

Room temperature drop hammer impact and compression after impact (CAI) experiments were conducted on carbon fiber-epoxy resin (CF/EP) composites to investigate the variation in impact load and absorbed energy, as well as to determine the residual compressive strength of CF/EP composites following impact damage. Industrial CT scanning was employed to observe the damage morphology after both impact and compression, aiding in the study of impact-damage and compression-failure mechanisms. The results indicate that, under the impact load, the surface of a CF/EP composite exhibits evident cratering as the impact energy increases, while cracks form along the length direction on the back surface. The residual compressive strength exhibits an inverse relationship with the impact energy. Impact damage occurring at an energy lower than 45 J results in end crushing during the compression of CF/EP composites, whereas energy exceeding 45 J leads to the formation of long cracks spanning the entire width of the specimen, primarily distributed symmetrically along the center of the specimen.

20.
Materials (Basel) ; 17(15)2024 Aug 04.
Artículo en Inglés | MEDLINE | ID: mdl-39124521

RESUMEN

Low-heat Portland cement and ground granulated blast furnace slag are widely used for the preparation of hydraulic concrete. Nevertheless, the effect and mechanism of corrosion on low-heat Portland cement paste mixed with ground granulated blast furnace slag need to be further explored. This paper investigated the impact of ground granulated blast furnace slag on the calcium leaching of low-heat Portland cement paste by evaluating its mass loss, porosity, leaching depth, compressive strength, and Vickers hardness, and comparing it with the leaching performance of ordinary Portland cement paste. Furthermore, the phase composition and morphology of low-heat Portland cement paste containing ground granulated blast furnace slag were analyzed by X-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy. The results indicate that, after 180 days of soaking in ammonium chloride solution, the mass loss rate, growth rate of porosity, leaching depth, and compressive strength loss rate of low-heat Portland cement paste were 8.0%, 43.6%, 9.1 mm, and 27.7%, respectively, while those of ordinary Portland cement paste were 7.4%, 37.8%, 8.4 mm, and 30.1%, indicating that low-heat Portland cement paste is slightly more damaging than ordinary Portland cement. The addition of ground granulated blast furnace slag could significantly improve the leaching resistance of low-heat Portland cement. For instance, after adding 20% ground granulated blast furnace slag, the above test values were 2.4%, 28.5%, 5.6 mm, and 20.8%, respectively. The reason for this is that ground granulated blast furnace slag has the potential to reduce the porosity of low-heat Portland cement paste, and it can also undergo the secondary hydration reaction with its hydration product Ca(OH)2 to enhance the paste structure. Considering the cost performance, the suitable dosage of low-heat Portland cement paste for satisfactory leaching resistance is about 20%.

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