Main Damage Mechanisms Research Articles

Evolution of Fretting-Induced Cracks and Delamination Wear on Alloy 690 Steam Generator Tubes During Mixed Fretting Regime in Air at Room Temperature

The occurrence of fretting-induced cracks and delamination wear processes in a mixed fretting regime on Alloy 690 steam generator tubes against 304L stainless steel pads was analyzed. Fretting tests in 90° cross-cylinder configuration were performed in air at room temperature. Changes in the contact conditions were evaluated using the energy ratio and the sliding ratio criteria. Damage was characterized using light microscopy, scanning electron microscopy, and optical profilometry. Vickers microindentation was applied to characterize the initial plastic deformation process. It was found that during the initial 1 × 103 cycles, plastic deformation constitutes the main damage mechanism. Thereafter, between 1 × 103 and 1 × 104 cycles, cracks nucleation and propagation accompanied by negligible wear were detected. Beyond 1 × 104 cycles, the dominant main damage mechanism consists of delamination wear assisted by cracks coalescence, and a change from a U-shaped to a W-shaped scar profile was observed in correspondence with the appearance of the delamination wear process.

Carburizing Rate of Pyrolysis Furnace Tube in Long-term Service

The high-temperature working environment of ethylene pyrolysis furnace tubes makes carburization one of the main damage mechanisms, and carburization also leads to the degradation of tube material properties and failure. It is important to study the carburization rate of long-term service furnace tubes for the evaluation of long-cycle use and carburization detection. In this paper, the relationship between carburization rate and carburization time is studied by low-pressure vacuum carburization of Cr35Ni45Nb alloy tubes with different service life (new tubes, two years, three years, and six years) in the field, aiming to provide a scientific basis for the remaining life prediction and carburization inspection for the tube material.

Factors affecting the development of liver fibrosis in patients who experienced COVID-19

The aim of the review is to highlight the main factors affecting the development of liver fibrosis and possible mechanisms of liver damage in patients who have experienced COVID-19. A search was carried out using keywords in the Scopus, Web of Science, and PubMed databases in literary sources of the last three years on factors associated with fibrogenesis in novel coronavirus infection.The review presents the main mechanisms of liver damage in COVID-19: direct effects on hepatocytes and cholangiocytes, hypoxia, and immune-mediated and drug-induced damage. We analyzed the significance of factors affecting fibrosis development in patients with COVID-19: chronic diffuse liver diseases, against which COVID-19 occurs, such as non-alcoholic fatty liver disease, alcohol-associated liver disease, chronic hepatitis B, C, and cirrhosis of the liver.Damage to the liver in coronavirus infection develops by several mechanisms. The development of COVID-19 against the background of diffuse liver pathology of various genesis is associated with progression of these diseases (increased fibrogenesis) and a poorer prognosis.

High-temperature behaviour and interfacial damage of CGI: 3D numerical modelling

Superior mechanical and thermal properties, high wear resistance and a competitive price of compacted graphite iron (CGI) have made it an integral part of industry worldwide. In its applications in automotive engines, high-temperature environments cause thermal expansion that can result in emergence of interfacial damage in CGI. Although graphite-matrix interfacial damage is considered the main damage mechanism that can lead to total fracture of CGI, extensive research on CGI has not yet fully investigated this phenomenon at the microscale, especially under pure thermal loading. This paper focuses on the high-temperature performance of CGI and the onset of damage in graphite in thermal cycles. Three-dimensional numerical models are developed, with a single graphite inclusion embedded in a unit cell of the metallic matrix. Elastoplastic behaviour is considered for both phases in simulations. The effects of morphology and orientation of graphite inclusions on a response of an entire unit cell to thermal loading are investigated. Also, the influence of periodic and fully-fixed boundary conditions on the damage behaviour of CGI is discussed. The results can give a better understanding of the fracture mechanisms of CGI exposed to elevated temperatures.

The coupling effect of cavitation-erosion and corrosion for HVOF sprayed Cu-based medium-entropy alloy coating in 3.5 wt.% NaCl solution

Ship propellers suffered from serious coupling damage of cavitation-erosion (CE) and corrosion when operated with high-speed in the marine environment. To improve the CE-corrosion resistance of the Ni–Al bronze (NAB) propeller alloy, a novel Cu-based medium-entropy alloy coating (Cu55Al20Ni12Ti8Si5, at.%) was prepared by high-velocity oxygen-fuel spraying technology in this study. The characteristics and CE behavior of coating and NAB were comparatively investigated, then the CE damage mechanism was discussed by analyzing CE damage morphologies. The influence of CE on corrosion behavior and the coupling effect between CE and corrosion were further elucidated by electrochemical corrosion experiments. The results indicated that the as-sprayed coating mainly comprised of BCC solid solution phase and NiTi-rich precipitates, which possessed higher hardness (6.73 ± 1.23 GPa) and superior resilience (27.0%) than the NAB. The cumulative mass loss rate for the coating after 18 h CE in distilled water and 3.5 wt.% NaCl solution was only 38.7% and 80.6% that for the NAB, revealing the better anti-CE performance of the coating. The preferential CE of the BCC matrix around the NiTi-rich precipitates, fatigue fracture and lamellar spalling were summarized as the main CE damage mechanism for the coating in 3.5 wt.% NaCl solution. CE had a significant influence on corrosion behavior of coating and NAB, which resulted in corrosion performance degradation of both two materials. The CE-corrosion coupling effect led to the remarkable mass loss, and mechanical effect rather than corrosion effect was ascribed to be the dominated factor for the damage of coating and NAB.

Effect of L‐T and S‐T orientations on fatigue crack growth in an aluminum 7050‐T7451 plate

AbstractThis study is focused on the anisotropic fatigue crack growth (FCG) behavior of an aluminum AA7050‐T7451 plate. L‐T and S‐T orientations were studied in M(T) samples with W = 50 mm, in mode I loading, with R‐ratio of +0.05. A numerical approach was used, assuming that crack tip plastic strain is the crack driving force. A purely kinematic elastic–plastic model was calibrated using experimental data from low cycle fatigue tests of smooth specimens in L and S orientations. The predicted FCG rates agree well with experimental trends in the Paris' regime, suggesting that cyclic plastic deformation is the main damage mechanism. The numerical model was used to estimate the stress ratio effect for both orientations, which was found to be linked with crack closure variations. However, the closure free predicted trends for both microstructural orientations at R = 0.05 are not overlapped, suggesting an effect of microstructure not linked to crack closure.

On the automated characterisation of inclusion-induced damage in 16MnCrS5 case-hardening steel

Manganese sulphide inclusions are commonly found in steels and known to facilitate the formation of deformation-induced damage sites in the form of voids during cold forming. These damage sites either exist as cracks, splitting the inclusion in two parts, or as delamination, separating the inclusion from the surrounding steel matrix. Both negatively influence the longevity of components, especially under cyclic loading. The analysis of damage is inherently scale-bridging, ranging from deteriorated global mechanical properties of the finished part, over the damage behaviour of individual inclusions, to the local description of individual voids. In this work, we set out to devise an analysis approach gathering information on all these scales. To this end, we conducted in-situ tensile tests while acquiring high resolution SEM panoramic images and analysed them with two neural networks, trained for this work, to detect damage sites with respect to the inclusions at which they nucleated. We find that the main damage mechanism during tensile deformation parallel to the length of inclusions is cracking and that damage evolution is equally influenced by void nucleation and void growth in the observed range of deformation. By focussing on the damaging behaviour of different inclusions, we show that the position of inclusions in the microstructure influences the resulting damage evolution and that the vicinity of pearlite bands leads to decreased damage formation.

Risk-based inspection (RBI) of a gas pressure reduction station

One of the principles of corrosion management is proper inspection methodology, and in particular the risk-based inspection (RBI). Occasionally a large percentage of the total risk of a unit is concentrated in a small part of the equipment, which can be reduced by using risk management techniques. In this study, a semi-quantitative risk-based inspection method has been performed in a gas station with for its components (pipelines, filters, etc.), to identify the existing damage mechanisms and also to rank its equipment in terms of inspection intervals. In this regard, RBI was performed for the gas station which consisted of phases (Phase A & Phase B) with Class 300 and Class 600 equipment. According to documented conditions and reviewed records the main damage mechanism for the investigated components in the gas station was identified as wall thinning due to erosion corrosion and external corrosion. In terms of inspection, results showed that most of the equipment studied had medium risk level and a few had medium to high level of risk. In this regard, the corrosion rates of Class 300 and Class 600 equipment were also studied and compared, and it was indicated that the corrosion rates were higher at locations for Class 300 equipment where more pressure drop had occurred. Overall, based on the obtained corrosion rates and obtained risk matrixes, it was concluded that wall thinning (erosion-corrosion) was the determining risk factor for equipment inspected in the gas pressure reduction station.

Research Progress on Metal-Organic Frameworks by Advanced Transmission Electron Microscopy.

Metal-organic frameworks (MOFs), composed of metal nodes and inorganic linkers, are promising for a wide range of applications due to their unique periodic frameworks. Understanding structure-activity relationships can facilitate the development of new MOFs. Transmission electron microscopy (TEM) is a powerful technique to characterize the microstructures of MOFs at the atomic scale. In addition, it is possible to directly visualize the microstructural evolution of MOFs in real time under working conditions via in situ TEM setups. Although MOFs are sensitive to high-energy electron beams, much progress has been made due to the development of advanced TEM. In this review, we first introduce the main damage mechanisms for MOFs under electron-beam irradiation and two strategies to minimize these damages: low-dose TEM and cryo-TEM. Then we discuss three typical techniques to analyze the microstructure of MOFs, including three-dimensional electron diffraction, imaging using direct-detection electron-counting cameras, and iDPC-STEM. Groundbreaking milestones and research advances of MOFs structures obtained with these techniques are highlighted. In situ TEM studies are reviewed to provide insights into the dynamics of MOFs induced by various stimuli. Additionally, perspectives are analyzed for promising TEM techniques in the research of MOFs' structures.

Main mechanisms of central nervous system damage with combined infection of HIV and SARS-COV-2: review

OBJECTIVE: Assess the degree of elaboration regarding mechanisms of the nervous system damage in HIV infection to further evaluate SARS-CoV-2, as a possible contributing factor in emergence and worsening psycho-neurological pathology in HIV-infected patients. MATERIALS AND METHODS: The analytical review was conducted using the medical database PubMed. More than 20 domestic and 30 foreign publications were studied on the mechanisms of the nervous system damage in HIV infection and SARS-CoV-2 between 2019-2022.Some preliminary study was conducted. Outpatient charts data of 146 HIV-infected patients were analyzed; a confirmed diagnosis of COVID-19 mild or moderate form (between 2020-2022) appeared in 42 (25,8%) cases (1st group). The comparison group (2nd group) included 40 patients without HIV infection, but suffered COVID-19, who were surveyed after signing voluntary informed consent. The survey data provided insight into the frequency and severity of neuropsychiatric manifestations and their possible connection with COVID-19. RESULTS: The high neuroinvasive and neurotropic HIV potential was demonstrated and implemented in a variety of ways and mechanisms that manifests in clinical practice by the appearance of diverse neuropsychiatric symptomatology. The study proved the influence of HIV infection on ACE-2 receptor expression by neurovascular cells (NVC) and also revealed some other features, contributing to the potentiation of SARS-CoV-2 invasion in CNS. The results of the preliminary study showed that in the group with HIV-infected 9 patients (21,4% of recover from COVID-19) experienced long-term neuropsychiatric manifestations after coronavirus infection, while all patients had long-term suppressed HIV viral load against the backdrop of regular ARV therapy and satisfactory immune status (CD4+ T-lymphocytes count). In the group without HIV infection after COVID-19 22 (55%) patients experienced neuropsychiatric complications, estimated by them as “extremely strong”. DISCUSSION: Although the study did not reveal a clear link between the presence of immunodeficiency in HIV infection and manifestation of neuropsychiatric pathology after COVID-19, further research is needed to define mutual influence of HIV and SARS-CoV-2 on the emergence of neuropsychiatric pathology. CONCLUSION: Considering a lack of research, where the results obtained could reliably confirm increased risk of complications from the nervous system, caused by SARS-CoV-2 against the backdrop of the existing HIV infection, there is reason to believe that this problem remains relevant today. This dictates the need to examine closely neurological status in patients of this category and monitor neurological complications.

DYNAMIC COMPRESSIVE PROPERTIES OF ALUMINIUM-MATRIX COMPOSITES REINFORCED WITH SiC PARTICLES

The aluminium-matrix composites (AMCs) consisted of (5, 10 and 15) x/% SiC particles (SiCp) in an aluminium alloy 7055 matrix. Specimens were taken from hot-press sintering. High-strain-rate tests were performed using the split-Hopkinson pressure bar (SHPB) method. The microstructures were observed with a scanning electron microscope (SEM) to understand the damage mechanisms of the SiCp/7055 Al composites at high strain rate. The SHPB test results show that the SiCp-reinforced composites are more sensitive to strain rate than the unreinforced material. The strain-rate sensitivity of the flow stress of these composites increases substantially with the increase of the strain rate. The flow stress of SiCp/7055Al composites with 10 x/% and 15 x/% SiCp at 3000 s–1 first increases and then decreases with the increase of the plastic strains, which was caused by the heat generated during adiabatic compression. Microstructure-characterization results show that SiCp cracking and SiCp/7055Al interface debonding are the main damage mechanisms of the composites. The SiCp volume fraction and strain rate affect the damage of composites during the dynamic compressive deformation of the SiCp /7055Al composites.

White X-Ray Radiation Effects in MOS Capacitors With Atomic Layer Deposited HfO2/Al2O3 and Al2O3/HfO2/Al2O3 Gate Dielectric Stacks for High Total Doses

White x-ray radiation effects in metal-oxide- semiconductor (MOS) capacitors with HfO2/Al2O3 (H/A) two-layer and Al2O3/HfO2/Al2O3 (A/H/A) three-layer gate dielectric stacks are investigated at high total dose levels of approximately 10, 50, and 100 Mrad(Si), based on capacitance-voltage (C-V) and current-voltage (I-V) measurements before and after irradiations, and the annealing behaviors at ambient temperature of the irradiated MOS capacitors are also observed over a long time. The H/A and A/H/A stacks are grown by atomic layer deposition (ALD), and have the same physical and equivalent oxide thicknesses. The C-V results indicate that the H/A and A/H/A-stack capacitors have almost an identical radiation response up to 50 Mrad(Si), and hole trapping is the main damage mechanism for the stacks. An anomalous C-V rebound for the A/H/A-stack capacitor after 100 Mrad(Si) is attributed to the existence of the potential well in the A/H/A stack, considering the continuously increased C-V shift for the H/A-stack capacitor with doses. In addition, radiation-induced interface traps lead to a significant C-V stretch-out even after 10 Mrad(Si), and multi-photon absorption is proposed for the production of the interface traps due to white x-ray irradiation at a high dose rate. Meanwhile, the I-V results show that the leakage current of the tested capacitors is increased after irradiation, and the A/H/A-stack capacitor has a much smaller leakage current than the A/H-stack capacitor, both before and after irradiation, because of its stack structure advantage in suppressing the leakage current. The primary mechanism for the leakage current is analyzed using the Frenkel-Poole model.

Гомоцистеїн як біомаркер судинної патології

The purpose of the study was to analyze professional literature sources devoted to the influence of homocysteine on the development of vascular disorders. The role of homocysteine as a biomarker of vascular pathology is considered. Materials and methods. Bibliosemantic and analytical methods were used in the study. The analysis of the specialized literature (47 sources) was carried out using information in the scientific-metric databases MEDLINE/PubMed, Scopus and Google Scholar. Results and discussion. Homocysteinemia is a pathological condition associated with quite serious consequences for the body; the endothelium of vessels suffers mostly: systemic endothelial dysfunction develops (including disruption of the synthesis and exchange of the endothelium-relaxing factor – nitric oxide), oxidative stress, activation of platelet aggregation, hypercoagulation occurs (due to a decrease in the activity of heparin, thrombomodulin and an increase in the activity of thromboxane A2). The prevalence of hyperhomocysteinemia in Ukraine is quite high and reaches 10% among healthy adults, 2% among young people and adolescents, from 13% to 43% in patients with cardiovascular pathology. The C677T polymorphism of the methylenetetrahydrofolate reductase gene is widespread among the population of Ukraine (40.7%). Researchers believe that hyperhomocysteinemia is an independent and modifiable risk factor for vascular pathology. Conclusion. Homocysteine is recognized as one of the markers of vascular pathology. Scientists consider the activation of oxidative stress, damage to the endothelium, stimulation of the proliferation of smooth muscle cells, and pro-inflammatory effects to be the main mechanisms of vascular damage in hyperhomocysteinemia. The described pathological changes are accompanied by a violation of the regulation of vascular tone, mostly due to a decrease in the synthesis of nitric oxide. Unbalanced synthesis of nitric oxide causes and potentiates oxidative stress, the processes of atherothrombogenesis. The professional literature presents enough scientific data that convincingly prove the role of homocysteine in the development of cardiovascular and neurological pathology. However, there is a small number of studies devoted to the relationship between hyperhomocysteinemia and periodontal diseases, and the pathogenetic mechanisms of the influence of hyperhomocysteinemia on the development of vascular disorders in coronavirus disease are not fully disclosed

Braiding procedure and axial compressive behaviors of three-dimensional integrated braided composite three-way circular tubes

The three-dimensional braided composite multi-way tube is one kind of high strength joint with a unique seamless braided microstructure. Here we report a new method to prepare the three-way integrated braided preform. Quasi-static axial compressive damages and strengths of the three-way braided composite tubes were tested for revealing the effects of braided structure on the compressive behaviors. We have paid more attention to braiding yarn strain distribution at the connection region and have found the braided yarns are in a uniform braided structure in this region. Compressive strength and initial stiffness can be improved by reducing branch length or increasing braiding layers. The surface strain on the branch tube shows obvious periodicity related to the braided structure while that on the connection region is affected by the bulging movement due to the compression of the three branch tubes. The main damage mechanisms are yarn breakage, yarn debonding, and kink band. This uniform braided structure paves the way to form the seamless braided structure among three branch tubes with high compressive strength.

Experimental investigations into mechanical response and damage mechanisms of fiber aluminum hierarchical composites

Carbon fiber reinforced aluminum matrix hierarchical composites have attracted the attention as a potential lightweight material for aerospace. Two typical Cf/Al composites were prepared by pressure infiltration method with changing the infiltration pressure. The analysis of microstructure, mechanical properties and failure behavior were carried out to systematically reveal the damage mechanisms of composites to realize their full potential. The results show that the infiltration process and solidification behavior of composites can be revealed by analyzing the evolution law of macrosegregation and microstructures. Compared with the matrix alloy, the bending strength of H-Cf/Al composites increased by 47%, and the compression strength of P-Cf/Al composites increased by 128%. To clarify the crack propagation behaviors of H-Cf/Al composite, toughening mechanisms such as crack deflection, crack bridging, and crack branching are discussed. The shear tests show that the failure characteristics of H-Cf/Al composites are mainly fiber bundle interface cracking, while the strong interlaminar shear strength of P-Cf/Al composites dominated by fiber splitting is attributed to serious interface reaction. In addition, main damage mechanisms affecting the ultimate failure were identified, namely interface splitting cracks, plastic deformation of matrix and fiber damage. This study provides meaningful enlightenment for the preparation and application of fiber-reinforced metal matrix composites.

Bio-tribological studies of Structalit/UHMWPE composites as an alternative to UHMWPE for hip joint application

In this study, epoxy based composites are evaluated for their mechanical and bio-tribological properties to find an alternative to UHMWPE liner material for hip joints. Structalit/UHMWPE composites were successfully developed with excellent filler-matrix bonding. Lower friction and wear of the composite (with 24 wt% of UHMWPE) against CoCrMo are attributed to the higher bulk mechanical strength and lower interfacial shear strength. Additionally, lubrication was supported by heterogeneity driven lubricant flow at the composite pin surface. Burnishing, abrasion, and protuberances were main surface damage mechanisms of UHMWPE whereas composite had few micro-cracks on its surface when filler loading was less.

A simulation result of trapped charge in PPD CIS induced by total ionizing dose effect

This paper describes a method for simulating the total ionizing dose (TID) radiation effect of a PPD CMOS image sensor (CIS) using TCAD. This paper takes the CIS pixel unit as the research object, modeling the device structure and combining it with a gamma radiation model to simulate the distribution of radiation-induced charge generation rate, electron concentration, and potential at each interface in the entire region before and after irradiation with TID equal to 5, 20, 50, 80, 100, 200, and 300 krad(Si). At the same time, the curves of the above parameters changed with the increase of TID radiation have been simulated. Furthermore, the influence of different TIDs on the parameters mentioned above at each interface has been investigated based on the two main damage mechanisms of the TID radiation effect: radiation-induced oxide trapped charge and radiation-induced interface trapped charge. It was also discovered that as the TID increases, the depletion region of the pinned photodiode (PPD) becomes broader, causing the dark current to increase.

Fatigue Crack Propagation under Christmas Tree Load Pattern

Most mechanical components are subject to dynamic loads, which can cause failure in service. This study aims to evaluate the effect of variable amplitude loadings on fatigue crack growth (FCG) in CT specimens produced with the AA2024-T351 aluminum alloy. Specifically, it is intended to predict the FCG rate when the specimen is subjected to a complex loading pattern, named the “Christmas Tree Spectrum”. Crack growth is simulated by node release, which occurs when the cumulative plastic strain at the crack tip reaches a critical value (110%) that is supposed to be a material property. It is therefore assumed that cyclic plastic deformation is the main damage mechanism. The specimen was subjected to four different load patterns: the 6–60 N low-frequency constant amplitude load (CAL); the 6–21 N high-frequency CAL; the Christmas Tree (15–9) and the Christmas Tree (9–3) patterns. The Christmas Tree 15–9 load pattern is defined by nine increments of +15 N and −9 N followed by eight increments of +9 N and −15 N. The results indicate that the Christmas Tree (15–9) pattern increases crack tip damage relative to the constant amplitude loading. This is attributed to small variations in material hardening, particularly during the unloading phase of the load block. On the other hand, the Christmas Tree (9–3) pattern did not show a significant effect, indicating the importance of the range of small-amplitude cycles. The crack closure phenomenon is usually used explain the effect of loading parameters, but this is an exception.

Effect of crack flank holes on fatigue crack growth

The effect of drilling two symmetric holes along the crack flanks on the fatigue crack growth (FCG) rate was evaluated numerically. The FCG increases (decreases) when the crack tip is behind (ahead) the holes. This behaviour is enlarged both by increasing the diameter of the holes and by reducing the distance between them. This is consequence of the geometrical effect, which modifies the plastic zone size. Experimental work validated the numerical model, indicating that that cumulative plastic strain at the crack tip is an adequate crack driving force and that cyclic plastic deformation is the main damage mechanism of FCG.

Review of Creep-Thermomechanical Fatigue Behavior of Austenitic Stainless Steel

Research on the creep-thermomechanical fatigue (CTMF) behaviors of austenitic stainless steel for nuclear power plant pipelines is reviewed in the present paper. The stress response behavior, the main damage mechanisms, including thermomechanical fatigue, creep, oxidation, and dynamic strain aging (DSA), as well as the effects of strain dwell type, dwell time, and temperature-strain phase angle on fatigue life behavior of austenitic stainless steel under CTMF loading conditions are systematically discussed, and the coupled effects of various damage mechanisms are revealed. It is emphasized that CTMF is closer to the actual service condition of nuclear power plant pipes. It is pointed out that the traditional method of life design based on the isothermal fatigue test data is not conservative. Finally, the research on CTMF behaviors of austenitic stainless steel for nuclear power plant is summarized and prospected.