Main Damage Mechanisms Research Articles

Covid-19: связь с патологией почек. Обзор литературы

COVID-19 is a severe acute respiratory disease caused by the SARS-CoV-2 virus. Although COVID-19 is characterized mainly by diffuse alveolar damage and acute respiratory failure, in some cases COVID-19 may acquire extra-respiratory features, including renal dysfunction that has existed earlier or developed de novo. The reasons for the extra-respiratory manifestations are biological properties of SARS-CoV-2 based on its multiple organ tropism. It has been shown that at least 50% of patients hospitalized for COVID-19 have proteinuria, hematuria, and signs of renal dysfunction, which in some cases reaches the degree of acute kidney injury (AKI). Here we present a review that discusses the clinical aspects and possible pathophysiological mechanisms of kidney damage in COVID-19. It is believed that renal damage observed in this disease is the result of a complex mechanism induced directly or indirectly by SARS-CoV-2 with the development of acute kidney injury. Two main pathophysiological mechanisms of kidney damage in COVID-19 are discussed. The first of them is the direct cytopathic effect of SARS-CoV-2 on the renal epithelium with the development of acute tubulonecrosis. The second mechanism is the cytokine storm syndrome that results from hyperactivation of the immune system with the development of acute renal and multiorgan infl ammatory damage accompanied by hypoxia, persistent hypotension, rhabdomyolysis, hyperactivation of the coagulation cascade, and microcirculation disorders. From a clinical point of view, it should be noted that signs of kidney damage are associated with an increase in the severity of COVID-19 and a poor outcome of the disease, and the prognosis becomes the worst with the development of AKI (the risk of death may increase by 5.3 times). The incidence of COVID-19 in patients with ESRD is higher than in the general population. The most typical for these patients is a severe course of the disease, which determines the increased mortality in comparison with the general population, caused by a respiratory failure with hyperactive infl ammation, cytokine storm, hemodynamic, and multiple organ failures. © 2021 JSC Vidal Rus. All rights reserved.

Phase‐field model for erosion processes

AbstractSolid particle erosion is one of the main damage mechanisms in high‐pressure compressors of jet engines. The significant shape change of the compressor blades leads to performance degradation over lifetime. To enhance predictive capabilities of erosive wear measurements under conditions, related to high pressure compressors, were performed. Even if there is no general model to describe erosive wear, it is understood that the transfer of kinetic energy from the impacting particle into the material is a central aspect in modelling erosion.In order to predict erosive wear of general geometries, Schrade et al. [9] developed a numerical model, based mainly on experimentally determined erosion rates. The shortcoming of such modelling approaches is the limited applicability in situations deferring to the measurement conditions. In the following, we will describe a physically based damage model, closing the gap between measurement and calculating shape changes of general specimens. Based on the phase‐field approach for predicting crack evolution presented by Miehe et al. [6], an overall energy balance of the considered specimen is constructed. A dissipative portion describes the influence of propagating damage, while special boundary conditions provides information about the energy transfer between impinging particles and specimen.

Carvedilol prevents pancreatic β-cell damage and the development of type 1 diabetes in mice by the inhibition of proinflammatory cytokines, NF-κB, COX-2, iNOS and oxidative stress

Inflammation is one of the main mechanisms of pancreatic β-cell damage and the development of type 1 diabetes (T1D). Carvedilol, a beta-adrenergic receptor blocker, has been demonstrated to have anti-inflammatory and antioxidant effects. The aim of this study was to investigate the protective effect of carvedilol against pancreatic β-cell damage and the development of T1D in an experimental model. T1D was induced in mice by multiple low-dose streptozotocin (STZ) injections. Diabetic mice were treated with carvedilol (15 and 20 mg/kg/day, orally) for 14 days. Results showed that blood glucose levels, diabetes incidence, body weight loss and insulitis in the pancreatic tissue were significantly reduced in mice treated with carvedilol. Treatment of mice with carvedilol significantly increased the levels of antioxidants glutathione (GSH), superoxide dismutase (SOD), and catalase and decreased the levels of malondialdehyde (MDA), nitric oxide (NO) and myeloperoxidase (MPO) in the pancreatic tissue as compared with those in the STZ-induced diabetic mice. Carvedilol decreased the expression of nuclear factor kappa B (NF-κB), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) as important modulators of inflammation and β-cell damage in the pancreatic tissue. In addition, carvedilol significantly reduced the levels of proinflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 IL-12, IL-17, interferon (IFN)-γ and chemokine MCP-1, while increased the anti-inflammatory cytokine IL-10 in the pancreatic tissue. In conclusion, these findings suggest that carvedilol is able to prevent pancreatic β-cell damage and the development of T1D in mice by the inhibition of inflammatory and oxidative mediators.

Microstructural effects on fracture toughness of ultra-high strength dual phase sheet steels

The influence of microstructure on the fracture toughness of two industrially processed 1000 MPa dual-phase (DP) steel grades is investigated. Crack initiation and propagation resistance are evaluated by means of the essential work of fracture (EWF) methodology and the main damage and fracture mechanisms are investigated. The results are discussed in terms of the proportion and distribution of the different microstructural constituents, which is assessed by scanning electron microscopy (SEM), high-resolution electron backscatter diffraction (HR-EBSD) and nanoindentation hardness measurements. The investigations show that the strain-induced transformation of retained austenite to martensite (TRIP effect), may be detrimental to cracking resistance, even though it increases tensile properties. This phenomenon is attributed to a "brittle" network effect generated by the presence of hard fresh martensite islands in the fracture process zone. The connectivity of the hard secondary phases and the proportion of soft phase (ferrite) also have a major role in fracture toughness. The DP steel with the larger volume fraction of ferrite and homogeneously distributed martensite islands shows significantly higher crack propagation resistance. The contribution of necking to the ductile fracture process is evaluated by means of thickness measurements in fractured DENT specimens and the correlation between the specific essential work of fracture (we) and tensile properties is investigated. It is concluded that the global formability and cracking resistance of high strength DP steels can be balanced through microstructural tailoring.

The etching process and mechanism analysis of Ta-Sb2Te3 film based on inductively coupled plasma

Compared to the conventional phase change materials, the new phase change material Ta-Sb2Te3 has the advantages of excellent data retention and good material stability. In this letter, the etching characteristics of Ta-Sb2Te3 were studied by using CF4/Ar. The results showed that when CF4/Ar = 25/25, the etching power was 600 W and the etching pressure was 2.5 Pa, the etching speed was up to 61 nm/min. The etching pattern of Ta-Sb2Te3 film had a smooth side wall and good perpendicularity (close to 90°), smooth surface of the etching (RMS was 0.51nm), and the etching uniformity was fine. Furthermore, the mechanism of this etching process was analyzed by X-ray photoelectron spectroscopy (XPS). The main damage mechanism of ICP etching in CF4/Ar was studied by X-ray diffraction (XRD).

Evolution of fretting wear with the number of cycles on Inconel 690 steam generator tubes against AISI 420 steel under gross slip conditions

The evolution of fretting wear with the number of cycles for Inconel 690 steam generator tubes against AISI 420 pads in air at room temperature was studied in a 90° cross-cylinder configuration. Tests were performed under a contact load of 10 N and a displacement amplitude of 50 μm to a total number of cycles between 102 and 106. Fretting wear associated with gross slip was identified as the main damage mechanism. The maximum wear depth was a better descriptor of wear evolution than the Archard defined wear coefficients due to the lack of linearity between wear volume and number of cycles. Debris detached at 106 cycles consist of agglomerates of 5–20 nm sized nanoparticles with chemical composition (Ni, Fe) (Fe, Cr)2O4.

Latest Evidence Regarding the Effects of Photosensitive Drugs on the Skin: Pathogenetic Mechanisms and Clinical Manifestations.

Photosensitivity induced by drugs is a widely experienced problem, concerning both molecule design and clinical practice. Indeed, photo-induced cutaneous eruptions represent one of the most common drug adverse events and are frequently an important issue to consider in the therapeutic management of patients. Phototoxicity and photoallergy are the two different pathogenic mechanisms involved in photosensitization. Related cutaneous manifestations are heterogeneous, depending on the culprit drug and subject susceptibility. Here we report an updated review of the literature with respect to pathogenic mechanisms of photosensitivity, clinical manifestations, patient management, and prediction and evaluation of drug-induced photosensitivity. We present and discuss principal groups of photosensitizing drugs (antimicrobials, nonsteroidal anti-inflammatory drugs, anti-hypertensives, anti-arrhythmics, cholesterol, and glycemia-lowering agents, psychotropic drugs, chemotherapeutics, etc.) and their main damage mechanisms according to recent evidence. The link between the drug and the cutaneous manifestation is not always clear; more investigations would be helpful to better predict drug photosensitizing potential, prevent and manage cutaneous adverse events and find the most appropriate alternative therapeutic strategy.

Experimental assessment of temperature effect on open-hole notch sensitivity in woven carbon fiber composites

Composite laminates often comprise notch-like features such as drilled assembly holes or geometric discontinuities resulting from damage. These features induce stress concentrations in their vicinities and can, through incompletely understood temperature-dependent damage mechanisms, reduce laminates’ load carrying capacity. Accordingly, this work investigates the effect of elevated temperatures on the notch sensitivity of carbon fiber-reinforced polymer composites and on the initiation and progression of notch-triggered damage mechanisms. This work employs an experimental approach in which tensile notched and un-notched specimens are loaded in controlled temperatures. Specimens are tested at multiple temperatures, and their nominal and local behavior in the vicinity of a circular notch are observed using digital image correlation. Results demonstrated a decreasing trend in the elastic moduli and ultimate tensile strength of notched specimens with increasing temperatures. However, the global response of notched samples at 50 $$^{\circ }$$ C surprisingly deviated from the expected trend and exhibited 8% higher tensile strength than that observed at 25 $$^{\circ }$$ C. Moreover, the notch sensitivity was found to decrease with increasing temperatures. Two main temperature-sensitive notch-triggered damage mechanisms were observed, namely transverse cracks and axial splitting. Transverse cracks were evident at all considered temperatures, while axial splitting was absent at room temperature.

Defining the role of ‘zero wear volume’ in percussive impact

This work defines the previously undetermined contribution of the ‘zero wear’ volume, that is geometry change due to material compression that occurs before other mechanisms that cause change through actual material loss are initiated during to repetitive impact. Five metal alloys widely used in engineering applications, each with a different bulk hardness, were the subjects of the experiments. Using a reciprocating hammer type impact wear test apparatus, flat coupon type specimens were subjected to repetitive impact from a chrome steel ball acting normal to the surface. 36,000 impacts were applied at a nominal rate of 10 impacts per second, each with an impact energy of 0.23J and an impact force of 3.5 kN. The impact wear crater on selected worn specimens was examined using a 3D non-contact profilometer. Scanning electron microscopy techniques were used to further examine the damage on the specimens. The main damage mechanism was plastic deformation and surface fatigue due to spalling. Microcracks and adhered wear debris were noted on the specimens, but with no evidence of delamination, while subsurface examination showed no possible microcracks under the impacted surface and only surface pitting could be observed from subsurface examination. Analysis of the wear scars suggests that zero wear volume is the main contributor to the total volume ‘loss’ for all materials, and, for specific materials, plastic flow volume and bulk hardness could be a significant parameter in characterising zero-wear volume and crater depth.

Comparison on failure behavior of three-dimensional woven carbon/carbon composites joints subjected to out-of-plane loading at room and high temperature

In the present work, an experimental investigation on the failure of 3D woven carbon/carbon all-composites mechanically fastened bolted joints with protruding-head and countersunk-head bolts has been implemented under out-of-plane loading in air at room temperature and up to 1100 °C for the first time. The load-displacement curves and main damage mechanisms for the required temperature points were determined and evaluated, respectively. It follows that, for room temperature, the global mechanical response was characterized by pseudoplastic, and the failure was dominated by the damage mechanisms including matrix cracking, interface debonding and threads fracture, especially, edge bending to breakage occurring for countersunk fastener. For 1100 °C, silicon carbide ceramic anti-oxidation coating was applied to prevent from oxidizing. Due to the relief of the thermal stresses, joints bearing capacity was enhanced by fiber/matrix interface performance improvement accompanying with a brittleness tendency of mechanical response, and the dominating failure mechanisms were carbon/carbon substrate oxidation caused by air entering through the cracks in SiC coating.

Numerical Prediction of the Fatigue Crack Growth Rate in SLM Ti-6Al-4V Based on Crack Tip Plastic Strain

This study presents a numerical model to predict the fatigue crack growth (FCG) rate in compact tension specimens under constant amplitude cyclic loadings. The material studied is the Ti-6Al-4V titanium alloy produced by selective laser melting, which was submitted to two different post-treatments: (i) hot isostatic pressing, and (ii) heat treatment. The developed finite element model uses the cumulative plastic strain at the crack tip to define the nodal release. Two different FCG criteria are presented, namely the incremental plastic strain (IPS) criterion and the total plastic strain (TPS) criterion. The calibration of the elasto-plastic constitutive model was carried out using experimental data from low cycle fatigue tests of smooth specimens. For both proposed crack growth criteria, the predicted da/dN-ΔK curve is approximately linear in log-log scale. However, the slope of the curve is higher using the TPS criterion. The numerical predictions of the crack growth rate are in good agreement with the experimental results, which indicates that cyclic plastic deformation is the main damage mechanism. The numerical results showed that increasing the stress ratio leads to a shift up of the da/dN-ΔK curve. The effect of stress ratio was dissociated from variations of cyclic plastic deformation, and an extrinsic mechanism, i.e., crack closure phenomenon, was found to be the cause.

The modern concept of neuroprotective therapy in the acute period of ischemic stroke

In recent years, significant successes have been achieved in the treatment of acute ischemic stroke. Given the trend towards an increase in the proportion of patients undergoing intravenous thrombolysis and / or mechanical thrombectomy, the question justifies: is there place for neuroprotective therapy (NT) in the era of active introduction of reperfusion treatment? The review discusses the main mechanisms of brain damage in ischemia / reperfusion and the leading neuroprotective strategies studied in clinical trials. Neuroprotective approaches to suppress excitotoxicity, oxidative and nitrosative stress are presented. The clinical efficacy of magnesium sulfate, uric acid, and edaravone is discussed. Non-pharmacological methods of neuroprotection have been characterized, including remote ischemic conditioning, therapeutic hypothermia and neurostimulation. NT in a situation of impossibility of cerebral reperfusion is discussed. The results of randomized clinical trials and meta-analyzes on citicoline (ceraxon) are analyzed. A clinical case is presented illustrating the management of a patient for whom reperfusion therapy was not feasible due to the course of the disease. In the era of the active development of reperfusion methods for the treatment of ischemic stroke, the goal-setting of NT has changed: it is intended to expand the possibilities of application and increase the effectiveness of intravenous thrombolysis and/or mechanical thrombectome, as well as neutralize their negative reperfusion effects. The main targets for NT remain excitotoxicity, oxidative and nitrosative stress. On the other hand, the real clinical situation associated with the low frequency of reperfusion technology in our country necessitates the use of neuroprotectors effective in this category of patients. In this regard, the administration of ceraxon increases the chances of achieving functional independence. The most effective use of the drug from the first day of the disease at a dose of 2000 mg per day intravenously for at least 4-6 weeks with further long-term oral administration at a dose of 1000 mg per day.

Coupling effect of strain rate and temperature on tensile damage mechanism of polyphenylene sulfide reinforced by glass fiber (PPS/GF30)

Influence of loading temperature on the damage mechanism of polyphenylene sulfide (PPS) reinforced by glass fiber (PPS/GF30) under tension was experimentally studied from quasi-static (QS) to high strain rates. Two kinds of PPS/GF30 samples were prepared: PPS-0° and PPS-90° (correspond to fibers oriented parallel and perpendicular to the injection direction, respectively). After microscopic observation and thermomechanical characterizations by dynamic mechanical analysis, tensile tests up to failure with strain rates varying from 10−3 s−1 to 100 s−1 have been carried out at 25°C and 120°C with regard to PPS/GF30 glass transition temperature. To achieve the coupling effect of high strain rate and high temperature, a special chamber was designed to install on the servo-hydraulic machine. The results of QS tensile tests confirm the significant effect of fiber orientation and temperature on the Young’s modulus, the ultimate stress, and strain. High strain tensile test results showed that the PPS/GF30 composite is strain rate dependent at both temperatures. The results indicated that Young’s modulus remains constant by strain rate increasing at both temperatures while ultimate stress and strain are increased. No significant damage has been observed at 25°C in QS loading, whereas the macroscopic damage variable is increased to 20% at 120°C. Debonding at the fiber–matrix interface is the main damage mechanism at 120°C.

Numerical Simulation of Cavitation Erosion Aggressiveness Induced by Unsteady Cloud Cavitation

A numerical investigation of the erosion aggressiveness of leading edge unsteady cloud cavitation based on the energy balance approach has been carried out to ascertain the main damaging mechanisms and the influence of the free stream flow velocity. A systematic approach has permitted the determination of the influence of several parameters on the spatial and temporal distribution of the erosion results comprising the selection of the cavitation model and the collapse driving pressure. In particular, the Zwart, Sauer and Kunz cavitation models have been compared as well as the use of instantaneous versus average pressure values. The numerical results have been compared against a series of experimental results obtained from pitting tests on copper and stainless steel specimens. Several cavitation erosion indicators have been defined and their accuracy to predict the experimental observations has been assessed and confirmed when using a material-dependent damaging threshold level. In summary, the use of the average pressure levels during a sufficient number of simulated shedding cycles combined with the Sauer cavitation model are the recommended parameters to achieve reliable results that reproduce the main erosion mechanisms found in cloud cavitation. Moreover, the proposed erosion indicators follow a power law as a function of the free stream flow velocity with exponents ranging from 3 to 5 depending on their definition.

Measurements of surface and bulk radiation damage effects in silicon detectors for Phase-2 CMS Outer Tracker

In this work we address the effects of bulk and surface damages on detectors fabricated by Hamamatsu on standard float zone (FZ) p-type material with an active thickness of 290 µm or thinned to 240 µm. In order to disentangle the effects of the two main radiation damage mechanisms, ionization effects and atomic displacement, the structures underwent two types of radiation: X-ray with doses from 0.05 to 70 Mrad (SiO2) and neutron in the range of 1−10 × 1014 neq/cm21MeV equivalent. The combined surface and bulk damage could be investigated in structures that underwent both types of irradiation. A wide set of measurements has been carried out on the test structures for a complete characterization.

An experimental investigation on lateral crushing response of glass/carbon intraply hybrid filament wound composite pipes

The current study aimed to examine an experimental investigation on the energy absorption capability of glass/carbon intraply hybrid filament wound composite pipes subjected to quasi-static lateral compression loading. The composite pipes with different fiber orientation angles were fabricated for both hybrid and non-hybrid to systematically analyze the performance of intraply hybridization process. At least 5 samples of each composite pipe configuration were tested to obtain the load–displacement curves and fracture patterns. The failure modes and fracture mechanisms of crushed samples were discussed to establish the influence of hybridization on crashworthiness parameters through load–displacement response. Separation between the layers (delamination) was occurred as the main damage mechanism in all samples. Hybridization with glass fiber significantly increased the energy absorption capability and load carrying capacity of carbon fiber-reinforced composite pipes. Their crushing values were found as between the values of pipes made of glass fiber and carbon fiber as expected. Furthermore, hybridization provided to opportunity of more stable load–displacement response for crushing process. An increment in fiber orientation angle was also led to increase in energy absorption capability and load carrying capacity. The pipe made of glass with higher fiber orientation had the best specific energy absorption.

Experimental and numerical analysis of novel multi-layer sandwich panels under three point bending load

In this study, mechanical behavior of multilayer corrugated core laminated composite sandwich panel subjected to quasi-static three-point bending is investigated experimentally as well as numerically. Parameters such as contact force, energy absorption and specific absorbed energy (unit mass energy) for different geometries of corrugated core (rectangular, trapezoidal and triangular) are studied during loading process and failure. Composite plates and corrugated cores have been manually made using ML506 epoxy resin with 15% hardener and 45% volumetric woven glass fibers. Experimental results show that multilayer sandwich composite panels not only strengthen the structure in the quasi-static three-point bending process, but also make the absorbed energy to grow significantly by increasing the contact force and displacement up to the complete failure. The main mechanisms of damage and failure of sandwich panel specimens during load bearing process are matrix cracking, fiber breakage, delamination, local indentation, global bending, crushing and buckling of cell walls and face sheet and core de-bonding. Rectangular geometry of corrugated core, in terms of energy absorption and specific energy exhibits better results in comparison to other shapes. Numerical simulation using ABAQUS FEA package led to results, which are in good agreement with experimental ones and make it possible to use simulation instead of costly tests for analysis and design.

Experiments and numerical modelling on angle-ply laminates under remote mode II loading

Delamination is a very frequent damage mechanism that affects the integrity of laminated composites. In this study, the effect of ply orientation on crack growth resistance was analyzed for three different anti-symmetric interfaces (±30°,±45° and ±60°) and compared to a unidirectional baseline under remote mode II loading. Fracture toughness at initiation was the same regardless of the ply orientation, nevertheless, the energy dissipated during crack propagation increased with ply angle. The fracture process exhibited by the anti-symmetric laminates showed repetitive zig-zag patterns featuring simultaneous crack migration and delamination. A first set of numerical analyses based on the virtual crack closure technique (VCCT) revealed that the anti-symmetric local fracture modes, i.e. longitudinal shear vs. transverse shear, are responsible for delamination and crack migration, respectively. The main damage mechanisms and their evolution, as observed experimentally, were well reproduced by an appropriate cohesive zone model, which takes into account the ply orientation during delamination.

The Progressive Failure Analysis of Uni-Directional Fibre Reinforced Composite Laminates

ABSTRACTThe three dimensional standard damage model developed by Lavedeze et.al [9, 13] for uni-directional fibre reinforced ply is implemented into the nonlinear solution of NX Nastran within composite solid element to analyze the progressive damage process and ultimate failure of fibre reinforced composite laminates. This ply level meso-damage-constitutive-model takes into account main damage mechanisms including fibre breaking, matrix transverse cracking, and fibre/matrix de-bonding; also considers contributions like plasticity coupling, damage delay effects, and elastic nonlinearity in fibre compression. Dissipated energy and damage status are also introduced to reflect the damage condition on the macrostructural-level. Using the implemented code, simulation is carried out on the uniaxial tension of a [±45]2s laminate with IM6/914 material, wherein the predicted ply shear rupture stress matches the experimental results very well and better than the theoretical predictions in literature. Moreover, a [-45/0/45/90] holed laminate loaded in tension is simulated to show the complex behavior of subcritical damage evolution and failure process in the composite structure. The composite solid element with damage model supported in NX Nastran is shown to be a reliable tool to analyze the progressive failure of uni-directional fibre reinforced composite laminates.

Micro-computed tomography analysis of damage in notched composite laminates under multi-axial fatigue

The broad application of polymer composites in engineering demands the deep understanding of the main damage mechanisms under realistic loading conditions and the development of proper physics-based models.Towards this goal, this study presents a comprehensive characterization of the main damage mechanisms in a selection of notched composite structures under multiaxial fatigue loading. Thanks to a synergistic combination of X-ray micro-computed tomography (μ-CT) and Digital Image Correlation (DIC), the main failure modes are identified while the crack volume associated to each mechanism is characterized. This study provides unprecedented quantitative data for the development and validation of computational models to capture the fatigue behavior of polymer composite structures.