Ring Material Research Articles

Comparison of Pericardial and Prosthetic Rings for Mitral Repair: Are Pericardial Rings Durable in the Mid- to Long-Term Follow Up?

While prosthetic rings are commonly used for mitral valve repairs, autologous pericardium is an alternative ring material that can be used in these procedures. In this report, we aim to present a comparison of two types of rings used for mitral repair. Between January 2005 and January 2009, 107 patients who underwent mitral valve repair surgery were analyzed. Patients were divided into two groups, according to the type of ring that was used for mitral annular stabilization. Glutaraldehyde-treated pericardial rings were used for 31 patients (group 1), whereas prosthetic rings were used for 76 patients (group 2). Survival, freedom from reoperation, recurrent mitral regurgitation, and the effects of rheumatic mitral disease on these parameters were evaluated and compared for both groups. Follow-up time for our cohort was 4.24±0.4 years. There were four and seven late mortalities in groups 1 and 2, respectively, and five reoperations in each group. There was no significant difference between the groups, in terms of survival, freedom from reoperation, and recurrent mitral regurgitation (log-rank analyses for both groups were P = 0.777, P = 0.346, and P = 0.781, respectively). There was no significant difference in freedom from reoperation and recurrent mitral regurgitation for both groups, in terms of underlying rheumatic valvular disease and other types of pathology. Pericardial ring annuloplasty shows to be a considerable alternative technique for mitral valve repair procedures in the mid- to long-term follow up. Rheumatic mitral valves had poor outcomes, when compared with other types of structural valvular pathologies in cases where pericardial rings were used in the repair procedure.

A dense ring of the trans-Neptunian object Quaoar outside its Roche limit.

Planetary rings are observed not only around giant planets1, but also around small bodies such as the Centaur Chariklo2 and the dwarf planet Haumea3. Up to now, all known dense rings were located close enough to their parent bodies, being inside the Roche limit, where tidal forces prevent material with reasonable densities from aggregating into a satellite. Here we report observations of an inhomogeneous ring around the trans-Neptunian body (50000) Quaoar. This trans-Neptunian object has an estimated radius4 of 555 km and possesses a roughly 80-km satellite5 (Weywot) that orbits at 24 Quaoar radii6,7. The detected ring orbits at 7.4 radii from the central body, which is well outside Quaoar's classical Roche limit, thus indicating that this limit does not always determine where ring material can survive. Our local collisional simulations show that elastic collisions, based on laboratory experiments8, can maintain a ring far away from the body. Moreover, Quaoar's ring orbits close to the 1/3 spin-orbit resonance9 with Quaoar, a property shared by Chariklo's2,10,11 and Haumea's3 rings, suggesting that this resonance plays a key role in ring confinement for small bodies.

Effect of Electric Current and Graphite Content on the Wear Behaviors of Copper/Graphite Composites

Abstract The reasonable electric current and graphite content will slow down the wear failure of friction pair and prolong the service life of slip ring. To study the wear behaviors of copper/graphite composites under different currents, the composites with graphite contents of 30%, 25%, 20%, and 15%, denoted as CG30, CG25, CG20, and CG15, were prepared as the material of slip ring. A series of friction and wear tests were carried out, and wear topography and friction vibration were measured. With the increase of electric current, the wear mechanism of CG30 is adhesive wear, and that of CG25 changes from adhesive wear to combined effect of adhesive wear and arc ablation. The anti-wear effect of CG30 is better than CG25. However, the ability of arc suppression of CG25 is better than that of CG30. Therefore, in order to improve the service life of slip rings, it is recommended to choose the composite CG25.

A discrete element modelling of gravity flow in sublevel caving considering the shape and size distribution of particles

ABSTRACT One of the most significant challenges for cave mining methods is dilution, a process which is generally controlled by the gravity flow of caved materials. In this study, the discrete element method (DEM) was used to investigate the effects of changing the porosity of blasted ring material and caved waste rocks and of changing the ring inclination on material flow in a sublevel cave (SLC) mine. Yade software was used to simulate two-dimensional gravity flow in a longitudinal section of the sublevel while taking into consideration the shape and size distribution of the flowing rock particles. Four simulations were generated with different porosities, and the material flow in the models was compared to each other. The results demonstrate that when ring porosity is increased, dilution decreases, and the height of the extraction zone grows longitudinally. Also, a lower porosity of the blasted ore material in the ring can cause early dilution entry and expansion of the extraction zone towards the caved waste.. Finally, the effect of ring inclination on the material flow and dilution was investigated. The results of these simulations show an increased dilution as the ring inclination increases and a change in the shape of the extraction zone.

Electrochemically Quantifying Oxygen Reduction Selectivity in Nonaqueous Electrolytes

Understanding the factors that govern the selectivity of the oxygen reduction reaction (ORR) has motivated the study of ORR in nonaqueous media, in which the proton donor can be controlled and molecular catalysts can be solubilized. Rotating ring-disc electrode (RRDE) voltammetry is a powerful method for quantifying ORR selectivity but requires that the ring electrode catalyze H2O2 oxidation at transport-limited rates. While the potentials and ring materials required to satisfy this requirement have been examined for aqueous electrolytes, they have not been systematically investigated for nonaqueous electrolytes despite the growing use of RRDE in these media. Herein, we report that conventional Pt ring electrodes and typical RRDE protocols for nonaqueous media do not give rise to mass-transport-limited H2O2 oxidation kinetics. Instead, H2O2 oxidation is strongly activation-controlled on Pt surfaces with kinetics that depend on the electrolyte and solvent. We identify Au as a superior catalyst for nonaqueous H2O2 oxidation and show that transport-limited H2O2 oxidation can be accessed on high-surface-area Au rings under certain electrolyte conditions. Additionally, we develop a protocol for calibrating and correcting for sluggish H2O2 oxidation kinetics. We show that these two methods provide improved estimates of H2O2 selectivity for ORR catalysis in certain nonaqueous electrolytes.

DETERMINATION OF THE OPTIMAL PARAMETERS OF LASER BORIDING TO IMPROVE THE WEAR RESISTANCE OF PISTON RINGS

Purpose. The goal was to determine the effect of laser heating parameters on the structure and depth of the borated layer, since the properties of piston rings depend on the depth of the latter.
 Research methods. Microstructural and X- ray phase analyzes were used to determine the structural state of piston rings.
 Results. Application of traditional boriding methods associated with diffusion of boron into the solid phase leads to formation of the working layer having high brittleness. The conducted studies revealed that the increase in the speed of displacement of the part in the process of laser heating reduces the depth of the borated layer. Such a dependence is observed both at 0.15 mm thickness of coating and at a thickness of 0.30 mm. For all modes of workpiece displacement speed for the used boron containing envelope with the above-specified thickness a higher thickness of the borated layer and the heat affected area corresponds to a higher thickness of coating. Increase of the spot size leads to an increase in the depth of the layer. By X- ray and metallographic diffraction there were decoded the phases and structural constituents of the borated layer.
 Scientific novelty. An approach to solving the problem of increasing the wear resistance of piston rings without crumbling is shown. The use of laser heating during drilling ensures the formation of a new layer with special properties. However, optimal properties can be achieved only after establishing a relationship between the parameters of the process and the depth of the boron layer. X-ray and metallographic analysis determined the relationship between the rate of irradiation and the proportion of high-boron structures in the layer. It is shown that the borated layer in high-strength cast iron contains such phases as FeB, Fe2B, α- phase, borocementite Fe3(B,C).
 Practical value. Increased wear resistance of piston ring materials, which often limits the growth of machine productivity and their service life. Research results can be extended to other parts subject to intensive wear.

Simulation and Experiment Research on Abrasive Wear of the Ship Mechanical Seal

The wear of friction pair resulting from seawater particles will inevitably bring marine tail shaft mechanical seal in the process of work, and abrasive wear will increase the static ring wear, resulting in the leakage of the mechanical seal. In this paper, through finite element simulation analysis of abrasive wear with different particle sizes and abrasive wear tests under different static ring materials, it is concluded that larger abrasive particle sizes will increase the deformation and residual stress on the surface of static ring materials, thus increasing the amount of wear, and the surface of softer static ring materials will be more serious. Also, if the particle size is too large, the particle concentration of the friction surface will decrease, and the wear will decrease.

Study on electrodeposition of CoNiW coating on 1045 steel as piston ring materials and its wear resistance performance

The CoNiW alloy coating is electrodeposited on the 1045 steel as piston ring materials by electrodeposition method to greatly improve the wear resistance performance. The electrodeposition of CoNiW belongs to a kind of induced co-deposition. The tungstate ions in the plating solution are beneficial to increase the deposition mass. Moreover, tungsten atoms could occupy the lattice junction of nickel and cobalt atoms to generate lattice distortion, which will reduce the grain size, decrease the surface roughness and improve the wear resistance performance. Compared with Co coating and CoNi coating, the CoNiW electrodeposited coating has the best wear resistance performance with the smallest surface roughness (0.179 µm) and the thinnest wear scar (7.4 µm average depth).

国内外超大直径特种环件材料对比分析

国内外超大直径特种环件材料对比分析

Tribo-electrical behaviors of CNTs-MoS2/Cu composites under sliding electrical contact with brass

As a new material for slip rings, CNTs-MoS2/Cu composites were prepared to improve tribo-electrical properties, including friction property, wear property, current-carrying property, and electrical conductivity. The high content of MoS2 and low content of CNTs improve the friction and wear properties, but weaken the current-carrying property and electrical conductivity. The sintering temperature changes the contents of MoS2 and affects the tribo-electrical property. The wear mechanisms of composites depend both on the electric currents and the contents of MoS2 and CNTs. The wear mechanism is adhesive wear under 1 A. It turns to the coupling of adhesive wear and arc ablation under 21 A. The results are of great significance to improve the performance of tribo-pairs that work under sliding electrical contact.

Effect of Elastic Contact Force on Tribological Characteristics of Current-carrying Roll Rings in Rotating Conductive Joints

A novel rotating conductive joint consisting of an inner raceway, an outer raceway, and an elastic ring was proposed in this study. The elastic ring was clamped between the inner and outer raceways using elastic compression force. The effect of the elastic force on the current-carrying properties and the damage of the ring material was investigated. As the elastic force increased from 10.2 N to 20.4 N, the total frictional force decreased from 15.5 N to 9.5 N, and the contact resistance decreased from 0.37 Ω to 0.18 Ω. While monitoring the revolution and rotation of the elastic ring, it was observed that the slip-rolling ratio decreased from 43.04% to 31.74%. Furthermore, a low friction coefficient was obtained under a high elastic force, which could be attributed to the small slip-roll ratio. The scanning electron microscopy and optical microscopy results revealed that a low friction coefficient led to subsurface crack initiation and a low degree of grain deformation. When the friction coefficient at a single contact point was greater than 0.34, fatigue occurred directly on the contact surface. The high friction-induced plastic deformation could cause surface hardening. Therefore, a high friction coefficient and large surface fatigue did not lead to high wear at low elastic forces.

Maintenance Cycle Reduction Time and Energy Savings of Mechanical Face Seals Using Thermodynamic FEM Analysis

The lifetime cost evaluation of a seal must take into account all expenses throughout its operation. The thermodynamic aspects of mechanical face seals (MFSs) analyzed using FEM for various pairs of materials and their correlation with wear, reliability, and economic feasibility have not been researched in the literature. The MFSs analyzed in this paper were manufactured by ROSEAL S.A. for use in water pumps. The materials of the primary seal rings used by manufacturers were taken into account. The operating conditions were as follows: n = 3000 rpm, water temperature = 80 °C, and pressure = 0.1 MPa. In our study, we focused on the thermodynamic phenomena occurring in the MFS. The thermodynamic simulation was run using the FEM software MSC Nastran. Maps of the temperatures and the heat flow in the primary seal rings, for the two types of MFS and for different pairs of materials, were obtained using FEM analysis. The results highlight that the flow rate of leaks increases linearly with the angular speed of the pressure ring and is independent of the materials used in the primary seal.

Effect of addition of MWCNTs to a mineral lubricant on Diesel engine performance

In this research, a diesel engine lubricant, modified with Multi-Walled Carbon Nanotubes (MWCNTs) was evaluated. Carboxylic group functionalized MWCNTs were dispersed in 15W40 mineral oil for Diesel engines and retaining ring and cylinder sleeve materials from F300 diesel engine were used for tribological tests. The Nanofluid (0.1 0.5 and 1% wt.) rheological behavior was characterized. Nanolubricants with 1% wt and base oil were evaluated on a Pin-on-Disk test. Results suggest both wear rate and coefficient of friction reduction when MWCNTs are used, while no significant rheological properties changes were observed.

Characterization of an Etch Profile at a Wafer Edge in Capacitively Coupled Plasma.

Recently, the uniformity in the wafer edge area that is normally abandoned in the fabrication process has become important for improving the process yield. The wafer edge structure normally has a difference of height between wafer and electrode, which can result in a sheath bend, distorting important parameters of the etch, such as ionic properties, resulting in nonuniform etching. This problem nowadays is resolved by introducing the supplemented structure called a focus ring on the periphery of the wafer. However, the focus ring is known to be easily eroded by the bombardment of high-energy ions, resulting in etch nonuniformity again, so that the focus ring is a consumable part and must be replaced periodically. Because of this issue, there are many simulation studies being conducted on the correlation between the sheath structural characteristics and materials of focus rings to find the replacement period, but the experimental data and an analysis based on this are not sufficient yet. In this study, in order to experimentally investigate the etching characteristics of the wafer edge area according to the sheath structure of the wafer edge, the etching was performed by increasing the wafer height (thickness) in the wafer edge area. The result shows that the degree of tilt in the etch profile at the wafer edge and the area where the tilt is observed severely are increased with the height difference between the wafer and electrode. This study is expected to provide a database for the characteristics of the etching at the wafer edge and useful information regarding the tolerance of the height difference for untilted etch profile and the replacement period of the etch ring.

Saturn’s atmospheric response to the large influx of ring material inferred from Cassini INMS measurements

During the Grand Finale stage of the Cassini mission, organic-rich ring material was discovered to be flowing into Saturn’s equatorial upper atmosphere at a surprisingly large rate. Through a series of photochemical models, we have examined the consequences of this ring material on the chemistry of Saturn’s neutral and ionized atmosphere. We find that if a substantial fraction of this material enters the atmosphere as vapor or becomes vaporized as the solid ring particles ablate upon atmospheric entry, then the ring-derived vapor would strongly affect the composition of Saturn’s ionosphere and neutral stratosphere. Our surveys of Cassini infrared and ultraviolet remote-sensing data from the final few years of the mission, however, reveal none of these predicted chemical consequences. We therefore conclude that either (1) the inferred ring influx represents an anomalous, transient situation that was triggered by some recent dynamical event in the ring system that occurred a few months to a few tens of years before the 2017 end of the Cassini mission, or (2) a large fraction of the incoming material must have been entering the atmosphere as small dust particles less than ∼100 nm in radius, rather than as vapor or as large particles that are likely to ablate. Future observations or upper limits for stratospheric neutral species such as HC3N, HCN, and CO2 at infrared wavelengths could shed light on the origin, timing, magnitude, and nature of a possible vapor-rich ring-inflow event.

Delivery of ceramide phosphoethanolamine lipids to the cleavage furrow through the endocytic pathway is essential for male meiotic cytokinesis.

Cell division, wherein 1 cell divides into 2 daughter cells, is fundamental to all living organisms. Cytokinesis, the final step in cell division, begins with the formation of an actomyosin contractile ring, positioned midway between the segregated chromosomes. Constriction of the ring with concomitant membrane deposition in a specified spatiotemporal manner generates a cleavage furrow that physically separates the cytoplasm. Unique lipids with specific biophysical properties have been shown to localize to intercellular bridges (also called midbody) connecting the 2 dividing cells; however, their biological roles and delivery mechanisms remain largely unknown. In this study, we show that ceramide phosphoethanolamine (CPE), the structural analog of sphingomyelin, has unique acyl chain anchors in Drosophila spermatocytes and is essential for meiotic cytokinesis. The head group of CPE is also important for spermatogenesis. We find that aberrant central spindle and contractile ring behavior but not mislocalization of phosphatidylinositol phosphates (PIPs) at the plasma membrane is responsible for the male meiotic cytokinesis defect in CPE-deficient animals. Further, we demonstrate the enrichment of CPE in multivesicular bodies marked by Rab7, which in turn localize to cleavage furrow. Volume electron microscopy analysis using correlative light and focused ion beam scanning electron microscopy shows that CPE-enriched Rab7 positive endosomes are juxtaposed on contractile ring material. Correlative light and transmission electron microscopy reveal Rab7 positive endosomes as a multivesicular body-like organelle that releases its intraluminal vesicles in the vicinity of ingressing furrows. Genetic ablation of Rab7 or Rab35 or expression of dominant negative Rab11 results in significant meiotic cytokinesis defects. Further, we show that Rab11 function is required for localization of CPE positive endosomes to the cleavage furrow. Our results imply that endosomal delivery of CPE to ingressing membranes is crucial for meiotic cytokinesis.

High-temperature nodal ring semimetal in two-dimensional honeycomb-kagome Mn2N3 lattice

The search for two-dimensional (2D) nodal ring semimetallic materials is a current research hotspot in spintronics, and designing a 2D nodal ring (NR) material with high Curie temperature (T C) and strong robustness to spin–orbit coupling (SOC) is an even greater challenge. Here, based on the first-principles calculations and symmetry analysis, we predict that 2D Mn2N3 is a nodal ring semimetal (NRSM) with three energy bands near the Fermi energy level consisting of electrons in the same spin channel. An electron-like energy band and two hole-like energy bands near the Fermi plane cross to form two NRs centered at the point Γ. Symmetry analysis shows that the spin-polarized NR semimetal is robust to SOC due to the conservation of horizontal mirror symmetry. Monte-Carlo simulations further demonstrate that the T C of the 2D Mn2N3 reaches 530 K, well above the room temperature. Notably, the 2D Mn2N3 remains an NRSM on h-BN substrate. Our results not only reveal a general framework for designing 2D NR materials, but also promote further research in the direction of multifunctional quantum devices for spintronics.

TEM Study of the Microstructure of an Alumina/Al Composite Prepared by Gas-Pressure Infiltration.

Ceramic injection moulding and gas-pressure infiltration were employed for the manufacturing of alumina/AlSi10Mg composites. Porous ceramic preforms were prepared by mixing alumina powder with a multi-binder system and injection moulding the powder polymer slurry. Then, the organic part was removed through a combination of solvent and thermal debinding, and, finally, the materials were sintered at different temperatures. Degrading the binder enabled open canals to form. The sintering process created a porous ceramic material consisting of alumina without any residual carbon content. During infiltration, the liquid metal filled the empty spaces (pores) effectively and formed a three-dimensional network of metal in the ceramic. The microstructure and properties of the manufactured materials were examined using high-resolution transmission electron microscopy, porosimetry, and bending strength testing. Microscopy observations showed that the fabricated composite materials are characterised by a percolation type of microstructure and a lack of unfilled pores. The research confirmed the diversified nature of the connection at the particle–matrix interface. It was observed that the interphase boundary was characterised by the lack of a transition zone between the components or a continuous transition zone, with the thickness not exceeding 30 nm. Thanks to their increased mechanical properties and low density, the obtained composites could be used in the automotive industry as a material for small piston rings and rods, connecting rods, or even gears.

Design and Hardware Experiment of Concentrating Magnetic Ring of Current Sensors Used in Open-Loop Fluxgate

In order to improve the ability of fluxgate current sensor to detect weak residual current, starting from the magnetic ring, which is the key magnetic concentrating element, and adopting the method of Comsol simulation analysis, the open-loop fluxgate is introduced from the aspects of magnetic ring material selection and structural design, etc. The key technology of the design of the magnetic concentrating ring of the current sensor is verified by experiments that the magnetic ring can increase the sensitivity of the current measurement by 15.4 times, and the frequency can reach 6.7 kHz, which can meet the AC and DC complex leakage current detection. Provide technical reference for designers engaged in this type of sensor.

Effect of tempering temperature on the microstructure, mechanical properties and abrasive wear behavior of a new C–Cr–Mo–V alloy steel used in TBM cutter ring

Tunnel boring machine (TBM) cutter ring material is a type of C–Cr–Mo–V alloy steel which possesses high hardness and wear resistance. To systematically study the effect of tempering temperature on the microstructure, mechanical properties and abrasive wear behavior of TBM cutter ring, a new C–Cr–Mo–V alloy steel (DB3) was subjected to tempering treatment and abrasive wear test. The results indicate that the tempering temperature controlled the hardness and toughness by adjusting the amount of precipitates and austenite transformation. Outstanding mechanical properties were obtained upon tempering at 520 °C. The wear resistance of DB3 steel was mainly controlled by hardness under non-impact abrasive wear condition. However, under the condition of impact abrasive wear, the wear resistance of DB3 steel was affected by hardness and toughness, and only in a certain range of toughness, the wear resistance increased with the increase of hardness. The experimental results can provide some reference for the heat treatment process of DB3 steel used in TBM cutter ring.