Flat Ring Research Articles

Finishing and Hardening of a Flat Surface Ring Area of a Workpiece by Rotary Burnishing

This work researches a smoothing process of original micro-profile and hardening process of AISI 304 steel surface layer material while performing rotary burnishing of the flat surface ring area. The paper establishes the interrelation between the number of indenter impacts and elementary volume of the material with a roughness and microhardness of the surface layer. The minimum roughness Ra=30 … 45 nanometers and the maximum microhardness of 425 … 475 HV0.25 is reached with the feed rate of 0.05 mm/rev and impact multiplicity of 70 … 100.

Estimates of the evolution of small perturbations in the radial spread (drain) of a viscous ring

This paper studies the evolution of small perturbations in the kinematic and dynamic characteristics of the radial flow of a flat ring filled with a homogeneous Newtonian fluid or an ideal incompressible fluid. When the flow rate is specified as a function of time, the main motion is completely determined by the incompressibility condition regardless of the properties of the medium. A biparabolic equation for the stream function with four homogeneous boundary conditions which simulate adhesion to the expanding (contracting) walls of the ring is derived. Upper bounds for the perturbation are obtained using the method of integral relations for quadratic functionals. The case of an exponential decay of initial perturbations is considered in a finite or infinite time interval. The admissibility of the inviscid limit in this problem is proved, and upper and lower bounds for this limit are estimated.

Effects of Titanium Mesh Cage End Structures on the Compressive Load at the Endplate Interface: A Cadaveric Biomechanical Study.

BackgroundThis study aimed to evaluate whether obliquely angled and ring-shaped titanium mesh cage (TMC) end structures can improve the compressive load on the endplate interface in anterior cervical corpectomy and fusion (ACCF).Material/MethodsA total of 23 volunteers underwent cervical lateral x-ray. The oblique angle of the superior endplate was measured, which was used to construct the gradient of the TMC end. Forty-two fresh cadaveric vertebral bodies were harvested and randomly distributed among four TMC groups with different ends. The baseline indicators of bone mineral density and anteroposterior and transverse dimensions were recorded. The superior endplate was placed at an angle of 12° when performing uniaxial compression testing. The maximum loads of the four TMCs were assessed.ResultsThere were no significant differences among the groups regarding the baseline indicators. The conventional TMC had the lowest maximum load (1362.3±221.78 N, p<0.05), whereas the TMC with an obliquely end ring had the highest maximum load (2095.82±285.64 N, p<0.05). The maximum loads of the TMCs with oblique footprints and flat end ring were much higher than that of the conventional TMC (p<0.05) but significantly lower than that of the TMC with the obliquely end ring (p<0.05), with average values of 1806.91±246.98 N and 1725.3±213.33 N, respectively.ConclusionsBoth the ring shape and oblique angle of the TMC end contributed to an increase in compressive force and are advocated for use in TMC structure optimization to decrease the incidence of TMC subsidence in ACCF.

Super-radiating manipulation of a nano-emitter by active toroidal metamaterials

The far-field radiation of a single dipolar emitter can be controlled by coupling to toroidal dipole resonance attached to metallic double flat rings, realizing a conversion from non- to super-radiating. The underlying physical mechanism is the hybridization interference of toroidal and electric dipoles under an asymmetric configuration by introducing a radial displacement of the dipolar emitter. By embedding gain medium in the gap spacer between double flat rings, the directional far-field super-radiating power can achieve a tremendous enhancement with a moderate requirement on the gain coefficient, promoting light-matter interaction manipulation.

Impedance based bolt pre-load monitoring using piezoceramic smart washer

Bolted connection is widely used in mechanical and civil engineering; however, in some cases, bolt looseness may cause catastrophic consequences. Bolt pre-load monitoring in real time can help to ensure the safety of component connections and durability of the entire steel structure. Previous research has demonstrated that a ‘smart washer (SW)’ fabricated by embedding a piezoceramic transducer into two flat metal rings could effectively detect the pre-load looseness of a bolted connection. The active sensing method, in which two SWs are necessary, was used in the previous research. In this research, an electro-mechanical impedance (EMI) method enabled by one ‘SW’ was developed to investigate the pre-load condition of a bolted connection. Since the installed SW is directly subjected to the same axial pre-load as that on the bolt, the piezoceramic SW with the EMI technique is uniquely suited for pre-load monitoring of a bolted connection. The pre-load reduction is directly reflected by the EMI of the piezoceramic SW. In particular, a decrease of the pre-load on a bolt connect results in the reduced of its resonant frequency, which can be revealed by the real part of the impedance. In addition, the root mean square deviation (RMSD) of the impedance signals was employed as an index to evaluate the bolt looseness degree. For the experimental study, a bolted connectional specimen with a piezoceramic SW was fabricated and investigated. In the experiment, eleven cases of different pre-loads on the bolt were studied. Experimental results clearly show that with the decrease of the bolt pre-load, the resonant frequency of the bolt joint also decreased, as reflected by the impedance of piezoceramic SW. In addition, experimental results demonstrated that the SW with the EMI based RMSD index can monitor bolt pre-load.

Form Factor of Flat Rings

Calculation results are presented for the form factor of a flat ring in a linear formulation of the theory of elasticity. The form factor accounts for the influence of the sample dimensions and Poisson’s ratio on the modulus of elasticity being measured. The two-dimensional problem of elastic deformation of a ring with boundary conditions specified for its entire surface was solved. Six flat rings of various sizes were made and their modulus of elasticity was measured to validate the results of calculations. The dispersion of values of Young’s modulus, corrected by the calculated form factor, did not exceed 2.5%, which corresponds to the range of error of measurement methods for the modulus of elasticity.

On the Structure-Property Relationships of Cation-Exchanged ZK-5 Zeolites for CO2 Adsorption.

The CO2 adsorption properties of cation-exchanged Li-, Na-, K-, and Mg-ZK-5 zeolites were correlated to the molecular structures determined by Rietveld refinements of synchrotron powder X-ray diffraction patterns. Li-, K-, and Na-ZK-5 all exhibited high isosteric heats of adsorption (Qst ) at low CO2 coverage, with Na-ZK-5 having the highest Qst (ca. 49 kJ mol-1 ). Mg2+ was located at the center of the zeolite hexagonal prism with the cation inaccessible to CO2 , leading to a much lower Qst (ca. 30 kJ mol-1 ) and lower overall uptake capacity. Multiple CO2 adsorption sites were identified at a given CO2 loading amount for all four cation-exchanged ZK-5 adsorbents. Site A at the flat eight-membered ring windows and site B/B* in the γ-cages were the primary adsorption sites in Li- and Na-ZK-5 zeolites. Relatively strong dual-cation adsorption sites contributed significantly to an enhanced electrostatic interaction for CO2 in all ZK-5 samples. This interaction gives rise to a migration of Li+ and Mg2+ cations from their original locations at the center of the hexagonal prisms toward the α-cages, in which they interact more strongly with the adsorbed CO2 .

Temperature estimation and slip-line force analytical models for the estimation of the radial forming force in the RARR process of flat rings

In this study, a mathematical model for the prediction of the temperature evolution in the ring during the radial-axial ring rolling process is developed and used, together with the authors’ previous results, to determine analytically the flow stress of the material during process. These results, combined with Hill's slip-line field solution adapted to the RARR process, allow a fast and reasonably precise calculation of the radial forming force, a key parameter at the preliminary stage of the process design. The approach is validated by applying the proposed model to a case available in the literature and comparing the analytical results with those of the laboratory experiment and FEM simulation. Following the successful comparison, the models were applied to a large variety of flat rings, comparing analytical predictions with the results of FEM simulations. The accuracy of the analytical calculation and the reliability of the proposed models, for different ring configuration and process parameters, are presented and discussed.

Smart washer—a piezoceramic-based transducer to monitor looseness of bolted connection

The safety of a bolted connection, as one of the most common ways of making two or more parts/components work together in engineering structures, is very important in order to ensure the health of the whole structure. However, bolt loosening or pre-load degradation may induce the failure of the bolt connection, threatening the normal operation of the system’s structure. As a result, it would be beneficial if the health condition of the bolt connection could be monitored in real time. In this paper, a ‘smart washer’, fabricated by embedding a piezoceramic patch into two pre-machined flat metal rings, was invented and then introduced as a transducer to detect the looseness of a bolted connection. A simple specimen, which consists of two steel plates connected by a nut, a bolt and two smart washers, was fabricated as the test object to study the performance of the ‘smart washers’ (SWs). For the specimen, a smart washer was used as an actuator to generate a stress wave, and the other one was used as a sensor to detect the propagated wave that traveled through the interface of the bolted connection. A time reversal method was employed to quantify the energy of the stress wave propagating between the two washers, and thus it was possible to build a relationship between the extent of any pre-loaded degradation of the bolt connection and the response signal of the stress wave traveling between the two washers. In addition, a normalized bolt looseness index was proposed for evaluating the looseness of a bolt connection based on wavelet energy analysis.

Incremental versus continuous load-lubrication procedure in the determination of friction conditions by the ring compression test

This work presents the differences found when using two types of methodology (continuous and incremental) in the application of load-lubricant during ring compression tests. Friction calibration maps have been obtained by conducting ring compression tests to flat rings of aluminium alloy UNS A97075-T6 with molybdenum disulphide (MoS2) as lubricant. Accordingly, in order to determine the particular values of the Coulomb friction coefficient, the problem was simulated using an elasto-plastic model with the finite element code Abaqus/Standard. A friction coefficients map from experiments and finite element simulation is drawn to compare the friction coefficient values derived from the continuous and incremental procedure. A comparison with experiments done with graphite powder as lubricant is also presented. Results of this investigation show that friction curves are affected by the methodology of load-lubricant application, and some guidelines about the use of these maps depending on the actual process conditions are provided.

Incremental versus continuous load-lubrication procedure in the determination of friction conditions by the ring compression test

This work presents the differences found when using two types of methodology (continuous and incremental) in the application of load-lubricant during ring compression tests. Friction calibration maps have been obtained by conducting ring compression tests to flat rings of aluminium alloy UNS A97075-T6 with molybdenum disulphide (MoS2) as lubricant. Accordingly, in order to determine the particular values of the Coulomb friction coefficient, the problem was simulated using an elasto-plastic model with the finite element code Abaqus/Standard. A friction coefficients map from experiments and finite element simulation is drawn to compare the friction coefficient values derived from the continuous and incremental procedure. A comparison with experiments done with graphite powder as lubricant is also presented. Results of this investigation show that friction curves are affected by the methodology of load-lubricant application, and some guidelines about the use of these maps depending on the actual process conditions are provided.

Mutual influence of plateau roughness and groove texture of honed surface on frictional performance of piston ring–liner system

The cylinder liner surface finish, which is commonly produced using the honing technique, is an essential factor of engine performance. The characteristics of the texture features, including the cross-hatch angle, the plateau roughness and the groove depth, significantly affect the performance of the ring pack–cylinder liner system. However, due to the influence of the honed texture features, the surface roughness of the liner is not subject to Gaussian distribution. To simulate the mixed lubrication performance of the ring–liner system with non-Gaussian roughness, the combination of a two-scale homogenization technique and a deterministic asperities contact method is adopted. In this study, a one-dimensional homogenized mixed lubrication model is established to study the influence of groove parameters on the load-carrying capacity and the frictional performance of the piston ring–liner system. The ring profile, plateau roughness, and operating conditions are taken into consideration. The main findings are that for nonflat ring, shallow and wide groove textures are beneficial for friction reduction, and there exists an optimum groove density that makes the friction minimum; for flat ring, wide and sparse grooves help improving the tribological performance, and there exists an optimum groove depth that makes the friction minimum.

The local-to-global principle for triangulated categories via dimension functions

We formulate a general abstract criterion for verifying the local-to-global principle for a rigidly-compactly generated tensor triangulated category. Our approach is based upon an inductive construction using dimension functions. Using our criterion we give a new proof of the theorem that the local-to-global principle holds for such categories when they have a model and the spectrum of the compacts is noetherian. As further applications we give a new set of conditions on the spectrum of the compacts that guarantee the local-to-global principle holds and use this to classify localising subcategories in the derived category of a semi-artinian absolutely flat ring.

Hofmeister Anion Effects on Thermodynamics of Caffeine Partitioning between Aqueous and Cyclohexane Phases.

Specific anion effects on the thermodynamics of caffeine partitioning between aqueous and cyclohexane phases were studied in the presence of 11 sodium salts by utilizing UV-vis spectroscopy. It is observed that weakly hydrated anions such as ClO4-, SCN-, and I- salt caffeine into the aqueous phase and increase the standard Gibbs free energy for caffeine transfer. On the other hand, well-hydrated anions such as CO32- and SO42- salt caffeine molecules out of the aqueous solution and promote the transfer process. Results suggest that weakly hydrated anions associate with the hydrophobic patches of caffeine including three methyl groups and a flat heteroatomic ring to solvate caffeine molecules. Well-hydrated anions are excluded from the caffeine surface to salt caffeine molecules out of aqueous solution. Moreover, the enthalpy and entropy of caffeine transfer were obtained by measuring the standard Gibbs free energy for caffeine transfer at varied temperatures. The transfer of caffeine from the aqueous to cyclohexane phase was an endothermic process driven by the entropy of caffeine transfer. However, the trend in standard Gibbs free energy across the Hofmeister series was determined by the enthalpy of caffeine transfer. These results provide an enthalpic origin to explain the Hofmeister trends in aqueous solution.

Resonance-based metamaterial in the shallow sub-wavelength regime: negative refractive index and nearly perfect absorption

The research on magnetic resonances in typical meta-atoms has led to the discovery of electromagnetic metamaterials (MMs). These new materials played a crucial role in achieving extraordinary phenomena as well as promised potential applications. In this paper, we numerically and experimentally investigated two different MM effects: the absorption and the negative refraction, which induced by magnetic resonances in a symmetric structure. The meta-atom sandwich model that includes two parallel flat rings separated by an insulating slab was designed. Firstly, three resonances in sub-wavelength range were demonstrated, revealing the negative permittivity and permeability effects. Notably, negative refractive index (NRI) was gained at the third-gap resonance, resulting from superposition of the rest of the electric resonance and the magnetic one accompanied by multi-plasmon. Moreover, the manipulation of the structural parameters could control the NRI behavior and, interestingly, a nearly perfect absorption peak arises in shallow sub-wavelength regime.

WEAR OF Si OR B DOPED AMORPHOUS CARBON COATINGS

The paper describes a complex wear research on DLC (amorphous carbon) doped with boron (B) and silicone (Si). The tests were carried out in two different sliding systems: flat–on–flat (ring contact, unidirectional sliding) and ball–on–flat (reciprocating sliding). Water and medical saline solutions were used as lubricants. A comparative analysis of the results revealed differences in the initiation and progress of wear and the endurance with regard to coating’s composition, lubricant and contact geometry. The results obtained from the tests show the influence of the additive element on the wear resistance and the high dependency of coatings’ performance in the type of contact and of the lubricant used. In all cases analysed, the use of medical saline solution resulted in accelerated wear or an increased result scatter in comparison to pure water lubrication.

Kitchenalia in Bronze Age Cyprus

This article explores the materiality of food production and consumption within the household in Bronze Age Cyprus. The focus is on embodied encounters with the “stuff of food”—the pots, pans, and other kitchen implements that were used on a daily basis—and how these shaped people's lives. Throughout the Early and Middle Bronze Ages, generations of families on Cyprus used Red Polished pottery to serve and consume food and drink: the round-bottomed pots were not designed to be laid on a table, indicative of the development of very specific customs of dining at home. The very limited range of pottery (wares and forms) available to the Early-Middle Cypriot householder suggests a monotone cultural experience. The introduction of vessels with flat bases or ring bases at the beginning of the Late Bronze Age might indicate a move to dining around a table—a radically different engagement with the physical, material world that undoubtedly affected social relations. This was accompanied by radical shifts in production practices—a move away from household production into the realm of craft specialists—alongside which there was an explosion in the range of tableware for consumption of food and drink and of utilitarian wares used within the kitchen. This article interrogates the implied transformations in the cultural knowledge embedded within people's engagement with their material world and the very different visual and tactile experiences involved in the daily use of pottery in the Late Bronze Age Cypriot household.

Did the silicoflagellate genusOctactisevolve fromBachmannocena?

It has long been assumed that Octactis and Stephanocha (previously known as Distephanus ) are closely related. Both have apical rings, but with Octactis possessing an apical ring of larger diameter relative to the basal ring and made of thinner elements. However, closer examination of the basal rings and double skeletons (doublets) shows other differences that have received little attention. The location of the struts and pikes on each side of the Neogene Stephanocha basal ring are consistently rotated towards the basal corners. This establishes a distinct basal element between the struts and pikes that is tilted to form a zig-zag basal design that creates an interlocking of the doublet skeletons. The pikes project into the region of the paired skeleton and the apical ring is also rotated with respect to the basal ring. In contrast, Octactis has a flatter basal ring without pikes, and possesses strut attachments located midway between the corners with the doublet held together only by organic material. Recent examination of living Octactis from the Seto Inland Sea of southern Japan provides a better understanding about the variability and structure of Octactis skeletons than previously available. Among these are double skeletons that have an incompletely formed daughter that consists only of the basal ring. The older literature includes line drawings that illustrate similar double skeletons, but these have not been previously photographed or adequately understood. Such skeletons are also found singly after disarticulation, and have a strong resemblance to those of fossil Bachmannocena (formerly known as Mesocena ), which also has a flat basal ring lacking apical structures and pikes. The hypothesis that Octactis evolved from Bachmannocena rather than from Stephanocha is presented, with the possible evolution of an apical ring in Bachmannocena accounting for the differences between the skeletal morphologies of Octactis and Stephanocha .

Flat local morphisms of rings with prescribed depth and dimension

Abstract For any pairs of integers (n,m) and (d, e) such that 0 ≤ n ≤ m, 0 ≤ d _ e, d ≤ n, e ≤ m and n -d ≤ m - e we construct a local flat ring morphism of noetherian local rings u : A → B such that dim(A) = n; depth(A) = d; dim(B) = m and depth(B) = e.

Tribological Performance of Polyamide-Imide Seal Ring Under Seawater Lubrication

High-performance engineering polymers are potential candidate materials for mechanical seals, especially in corrosive environments and environments where substantial shock and vibration loads are present. This study addresses the friction and wear performances of polyamide-imide (PAI) sliding against tungsten carbide (WC) in seawater for seal applications. The experimental setup consists of two nominally flat rings rotating against each other to simulate the contact in mechanical seals. Three types of experiments were performed, i.e., measurement of friction and wear in a series of 8-h tests, measurement of the friction coefficient as a function of speed and load and measurement of PV (pressure times velocity) limit. Test results show that at lightly loaded conditions WC/PAI seal rings in seawater can reach hydrodynamic lubrication with ultra-low friction coefficient and wear rate.