Large-sized Rings Research Articles

Copper-Catalyzed [2 + 2] Cyclization/Ring Expansion of Ene-Ynamides: Construction of Medium- and Large-Sized Rings.

Catalytic cyclization of enynes is an efficient approach for the preparation of cyclic compounds, and a large variety of four- to six-membered rings could be synthesized using this method. However, it has been rarely employed for the construction of medium- and large-sized rings. Herein, we describe a copper-catalyzed cycloisomerization of ene-ynamides through a [2 + 2] cyclization/electrocyclic ring opening cascade, leading to the atom-economical assembly of indole-fused medium- and large-sized rings in moderate to excellent yields under mild reaction conditions. Importantly, the synthetic utility of this reaction was demonstrated by the convenient synthesis of iprindole.

An Industrial-Scale Study of the Hardness and Microstructural Effects of Isothermal Heat Treatment Parameters on EN 100CrMo7 Bearing Steel

The 100CrMo7, commonly employed for bearings in rotating machinery, relies on precise heat treatment parameters to ensure an optimal microstructure and, in turn, mechanical properties. Typically, an austenitizing treatment, followed by rapid cooling in a salt bath for martempering or austempering, is crucial in achieving the desired microstructure and hardness. The present industrial-scale study involved a comparative analysis between martempering and austempering routes regarding the hardness and microstructure evolution of EN 100CrMo7 large-size rings. The investigation delves into the effects of austempering temperatures, holding times, and austenitizing temperature. Furthermore, the role of tempering in reducing the amount of retained austenite was also considered. The results indicate that martempering yielded the highest hardness values while austempering exhibited a decrease in hardness at the center of the rings, though a lower amount of retained austenite (in the range of 3.0–4.9 vol.%) was detected in comparison with martempering. In addition, a 850 °C austenitizing temperature reduced the hardness by 16% in the center of the rings and promoted a high content of upper bainite, thus suggesting its inefficacy for the involved large-size rings. In contrast, a 880 °C austenitizing temperature maintained consistently high HRC values across the ring’s height. Lastly, the analysis highlighted that the cooling rate played a more crucial role than the austempering holding time. Such industrial-scale investigations performed on real components improve the knowledge and control of heat treatment parameters in comparison with the nominal guidelines provided by steel suppliers. These outcomes offer insights for optimizing industrial heat treatment parameters, with practical implications for enhancing steel bearings’ microstructural and mechanical performance and lifespan.

Influence of Diameter Increase Speed on Diameter-Axial Rolling of Large 40Cr13 Stainless Steel Ring

Rolling speed ratios during the rolling process are critical to ring forming in this pepper. The selected roll feed mode is constant with the increasing speed of ring diameter during the main rolling stage. Based on Deform-3D finite element software, a large size ring with a diameter of φ1530 mm was taken as the research object. The numerical model of a large 40Cr13 stainless steel ring is established. The radial-axial rolling process of rings under different diameter increase speeds was simulated, and the changes in radial rolling force, temperature, and strain distribution of rings after rolling were analyzed under different diameter increase speeds. The results show that under the same conditions as other parameters, increasing the ring diameter increase speed has less effect on the temperature and equivalent standard deviation of variation inside the ring after rolling, but has more effect on the external surface, and both SDP and SDT decrease with the increase of ring diameter increase speed. The ring diameter increase speed on the maximum rolling force is more obvious, with the diameter increasing speed increasing. Using the rolling force, temperature standard deviation, and equivalent effect variation standard deviation as reference indexes, the diameter increase rate suitable for 40Cr13 rings is 6 mm/s.

A Method to Measure Permeability of Permalloy in Extremely Weak Magnetic Field Based on Rayleigh Model.

In order to solve the problem that the relative permeability of the permalloy is missing and difficult to measure accurately in an extremely weak magnetic field (EWMF, <1 nT), a method to measure the permeability in EWMF based on the Rayleigh model is proposed in this paper. In this method, the Rayleigh model for the magnetic material was first introduced. Then, the test system for measuring the permeability of permalloy for the standard ring specimen was set up. Based on the test data and the Rayleigh model, the functional expression applied to obtain the permeability in EWMF is achieved. Finally, the feasibility and accuracy of the method are verified by the permeability measurement of the custom large-size ring specimen in EWMF (<1 nT) and residual field measurement based on the four-layer shielding cylinder. This method can obtain the relative permeability in any EWMF and avoid test errors caused by extremely weak magnetization signals.

Elaboration of Parameters of Large-Size Rings Production Process Taking into Account the Evolution of Material Relative Density

The paper presents the selected problems in production chain of large-size rings for the offshore industry. There are two goals of the technology: 1) to obtain the correct shape of the rings, 2) to achieve required properties. A significant problem in the processes of large size forgings production is a proper prediction of the as-cast structure defects and their behaviour during deformation (forging). This study examines a method of prediction of relative density changes of the material during forging. Experimental procedure includes a forging test at the laboratory scale and numerical modelling. These results as well as boundary conditions were used as input data for the computer simulations of the large rings production processes. The presented procedure allows for a comprehensive analysis of the production process of large-size rings, taking into account areas with insufficient material compaction. The analysis allows for changes in the production chain at the design stage, which significantly reduces the costs associated with pre-implementation tests.

Demonstration of reinforcement in polymer composite with rings penetrating the diamond-lattice network

To study the qualitative behavior of large rings embedded in crosslinked polymer networks, the effect of large rings on the stress–strain curve was examined by coarse-grained molecular dynamics simulation of the Kremer–Grest model. In this study, large rings were embedded in the diamond-lattice polymer network based on the push-off procedure for ring pure melts and polymer network. To investigate the difference in behaviors with respect to strand penetration into a ring, we applied the chain shrinking process based on the primitive path analysis. We found that the large-sized rings were widely spread and interfered with each other in the network. We evaluated stress–strain curves under uniaxial elongation as a function of the ring size (number of beads per ring Nring) and ring fraction fring. It was found that the nominal stress increased with the increasing Nring and/or fring although the increase is limited owing to the interference of rings. Changes in the ring shape were observed under uniaxial elongation in terms of the gyration radius Rg2, ratio λ1/Rg2, and asphericity A, where λ1 denotes the first eigenvalue of the gyration tensor. We confirmed that the rings embedded in crosslinked network certainly play roles as movable crosslinks and reinforce the network.

Research on dynamic measurement of hot ring rolling dimension based on machine vision

In the process of ring rolling, the rolling process parameters of the equipment have an important influence on the forming process and forming quality of the ring. The ring rolling process has the characteristics of non-linearity, easy interference, rapid growth and asymmetric shape. These factors have resulted in the inability to measure the dimensions of the ring directly. In this work, we established a vision measurement system, and performed a series of operations on the image, such as threshold segmentation, hot ring contour extraction, oxide scale filtering, inner and outer ring extraction, inner and outer ring sampling, data visualization, etc. Moreover, we measured the dynamic dimension characteristics of small and medium size hot ring in the rolling process. The circularity, dimensional difference, center swing and vibration characteristics of the ring in the rolling process are obtained through the algorithm design, which characterizing the size change of the hot ring. The study provides practical methods and theoretical guidance for the subsequent measurement of large-size rings and feedback control of the rolling ring.

Study of Conditions for Thermal Deformation of Additively Grown Billets from VT6 Titanium Alloy using Finite Element Simulation

This article investigates the hot rolling aspects of a large-sized ring of non-standard, cross-sectional shape, produced from VT6 titanium alloy, and grown using additive technologies (АТ). Finite element (FE) simulation was used to develop the cross-sectional shape and study the parameters of the rolling process. The results enabled the choice of the optimal cross-sectional shape of the ring billet produced by direct laser deposition (DLD), and confirmed the possibility of processing the billet on a ring rolling mill.

Stepwise Strategy for One-Pot Synthesis of Single-Stranded DNA Rings from Multiple Short Fragments.

Cyclic rings of single-stranded (ss) DNA have various unique properties, but wider applications have been hampered by their poor availability. This paper reports a convenient one-pot method in which these rings are efficiently synthesized by using T4 DNA ligase through convergent cyclization of easily available short DNA fragments. The key to the present method is to separate all the splint oligonucleotides into several sets, and add each set sequentially at an appropriate interval to the solutions containing all the short DNA fragments. Compared with simple one-pot strategies involving simultaneous addition of all the splints at the beginning of the reaction, both the selectivity and the yields of target ssDNA rings are greatly improved. This convergent method is especially useful for preparing large-sized rings that are otherwise hard to obtain. By starting from six short DNA fragments (71-82 nt), prepared by a DNA synthesizer, a ssDNA ring of 452-nt size was synthesized in 35 mol % yield and in high selectivity. Satisfactorily pure DNA rings were obtainable simply by treating the crude products with exonuclease.

Numerical modelling of the multi-stage production process of large-size rings rolling for the shipbuilding industry including analysis of internal discontinuities

This article presents the problems related to production of large-size rings for the shipbuilding and offshore industries. The technology of shaping this type of products includes initial preparing of ingots, making a central hole and rolling on a multi-tool ring rolling mill. The main goal of the plastic deformation, in addition to obtaining the required geometric shape of the products, is to ensure an appropriate internal structure and thus the desired operational properties. A significant problem in the processes of shaping products from forging ingots is a proper characteristic of the internal defects of the cast structure. The purpose of plastic deformation applied at high temperature is to minimize these defects. This study examines the changes in the relative density of the material depending on the degree of structure modification (deformation degree). The results as well as boundary conditions reflected from the industrial processes were used as a data for the computer simulations of the large rings production processes. All of the technological operations are included in these simulations, from heating of the forging ingot to final rolling of the finished product. Numerical simulation was performed using QForm – commercial software based on finite element method (FEM).

Annulative Allylic Alkylation Reactions between Dual Electrophiles and Dual Nucleophiles: Applications in Complex Molecule Synthesis.

Metal-catalyzed allylic alkylation reactions between dual nucleophiles and dual electrophiles represent a powerful set of methods for the synthesis of small-, medium-, and even large-sized rings. Using this strategy, a handful of simple allylic diol derivatives can be transformed into a broad array of complex carbo- and heterocycles of varying ring sizes in just a single step. Because of their ability to rapidly generate complexity, annulative allylic alkylation reactions between dual nucleophiles and dual electrophiles have been extensively employed in the total synthesis of both natural products and pharmaceutical compounds.

Effect of the Surface Roughness on the Shear Strength of Granular Materials in Ring Shear Tests

Surface roughness plays an important role in estimating the shear strength of granular materials. A series of ring shear tests with different surface roughnesses (i.e., smooth and rough surfaces) were performed. A large-sized ring shear device, which is applicable for fine- and coarse-grained sediments, was developed to examine the shear strength of large particle sizes (i.e., commercial gravels with a mean grain size of 6 mm). In terms of surface roughness, the drainage- and shear-velocity-dependent shear strengths of the granular materials were examined. In this study, different shear velocities of 0.1, 0.5, and 1 mm/s were applied under drained and undrained conditions. The test results clearly show that shear stress is affected by drainage, shear velocity, and surface roughness. In particular, a typical strain-hardening behavior is exhibited regardless of the drainage and shear velocity condition. The measured shear strength obtained from both drained and undrained conditions increased with increasing shear velocity. All tests showed a large fragmentation using rough surfaces compared to the smooth surfaces of the device. The grain crushing was significant during shearing, even when normal stress was not applied. For a given shear velocity, surface roughness is an important feature in determining the shear strength of granular materials.

ON RING DEFORMATION BY INTERNAL PRESSURE

Large-sized rings, manufactured by various methods of metal forming, are used in many industries. For the power industry, it is relevant to manufacture of retaining rings made of non-magnetic austenitic steel in order to strengthen the winding frontal parts of the rotors of turbine-type generators of a large unit capacity. In the process of generator operating, the retaining ring is one of the most loaded elements. As a result, material of retaining rings should have high strength properties, sufficient plasticity and good magnetic inductivity. Deformation of rings by internal pressure is the most promising and effective way of their cold hardening, providing a favorable and uniform stress-strain state of the metal in the manufacture of non-magnetic retaining rings for powerful turbine-type generators. Since the finished ring must acquire specific dimensions and a specified deformation degree in the process of cold hardening, the urgent task is calculation of the billet dimensions. The existing calculation procedure relies heavily on experimental manufacture data and is applicable only to a narrow range of rings, which reduces the accuracy of calculation and, ultimately, leads to an increase in ring allowances and a decrease in the metal utilization factor. In this research work a new technique for calculating the initial dimensions of rings, which is based on the incompressibility condition was developed and proposed. Taking into account the assumed boundary conditions, a system of two equations with three terms is compiled. To solve an incomplete equation system, it was suggested to introduce additional equations – in first version of the technique, the well-known solution of Nadai was used. In the second version – the condition of constancy of relative thickness of the ring wall permissible from the experimental data of deformation of rings of different sizes was used. The results of calculating the rings initial dimensions for both proposed techniques were compared with the experimental data. The maximum deviation from experimental data does not exceed 4 % and the deviation average value does not exceed 1 %, which indicates a sufficiently high accuracy of the proposed calculation techniques and the possibility of using them in manufacturing practice.

Plasticity in vitreous silica induced by cyclic tension considering rate-dependence: Role of the network topology

In this paper, we investigate the visco-plastic stress response of vitreous silica under tension using molecular dynamics simulations. Firstly, we show significant rate-dependence by alternately subjecting vitreous silica to loading and relaxation. Using this strategy, we eliminate viscous effects, a quasi-static hysteresis is obtained and remaining plastic deformations are observed. We investigate the medium-range order at various deformation states on the quasi-static hysteresis. We demonstrate that, although, the short-range order does not noticeably differ at various deformation states on the quasi-static hysteresis, the medium-range order, evaluated through the ring statistics, shows significant changes. Based on the observation of similar trends regarding the ring statistics, three groups, i.e. small-, medium- and large-sized rings, are classified and their changes are linked to the plastic behavior. Furthermore, in order to link the medium range order to rate-dependence, changes in the ring statistics, caused through mechanical relaxation, are investigated and discussed.

Melting and Thermomechanical Processing of High Strength 0.3%C–CrMoV (ESR) Steel

0.3%C–CrMoV steel were processed through electric arc furnace melting followed by electro slag refining. 2800 mm diameter class of rolled rings and 8 mm thick plates required for fabrication of solid rocket booster motorcase were realized. Tensile and fracture toughness properties were evaluated as a part of characterization of the steel. Low fracture toughness in initial melts was investigated using optical and scanning electron microscopy. Modifications in methods of alloying additions/processing were suggested and incorporated to achieve the desired mechanical properties in industrial scale melts. Process was also fine-tuned by incorporating additional thermomechanical working and heat treatment cycles to achieve the required mechanical properties. Hardening cycle of 925 °C for 1 h followed by oil quenching and tempering cycle of 505 °C for 2 h followed by oil quenching was found to result in optimum combination of mechanical properties. Repeatability in processing and consistency in achieving the mechanical properties of the steel at industrial scale was demonstrated by processing 24 melts of 6 tons each into large size rings and plates.

GINGER

Gyroscopes IN General Relativity (GINGER) is a proposal of an Earth-base experiment to measure the Lense–Thirring effect. GINGER uses an array of ring lasers, which are the most sensitive inertial sensors to measure the rotation rate of the Earth. GINGER is based on a three-dimensional array of large size ring lasers, able to measure the de Sitter and Lense–Thirring effects. The instrument will be located in the INFN Gran Sasso underground laboratory, in Italy. We describe preliminary developments and measurements. Earlier prototypes based in Italy, GP2, GINGERino, and G-LAS are also described and their preliminary results reported.

Copper‐Catalyzed C(sp2)–C(sp3) Cross‐Dehydrogenative Coupling of Quinones with Cyclic Alkanes: One‐Step Access to Parvaquone and its Analogs

AbstractA copper‐catalyzed direct cross‐coupling reaction of quinones with cycloalkanes in the presence of tert‐butyl hydro peroxide was developed. This methodology allows the direct installation of cycloalkyl groups with medium‐ and large‐sized rings on 1,4‐naphthoquinones, anthracene‐1,4‐dione, or 1,4‐benzoquinones. Based on this new protocol, the one‐pot synthesis of the antimalarial drug, parvaquone, was achieved.

Cavitands as Chaperones for Monofunctional and Ring-Forming Reactions in Water.

Cyclic processes involving medium-sized rings show low rates because internal strains-torsions and transannular interactions-are created during the reactions. High dilution is often used to slow the competing bi- and higher-molecular processes but cannot accelerate the desired cyclization reaction. Here we apply cavitands to the formation of medium- to large-sized rings through conversion of long-chain diisocyanates to cyclic ureas. The reactions take place in aqueous (D2O) solution, where hydrophobic forces drive the starting materials into the cavitands in folded conformations. The guest assumes the shape to fill the space properly, which brings the reacting ends closer together than they are in bulk solvent. Complexation overcomes some of the internal strains involved in precyclization shapes of the guest molecules and accelerates the cyclization. The results augur well for applications of water-soluble cavitands to related processes such as remote functionalization reactions.

The GINGER project and status of the GINGERino prototype at LNGS

GINGER (Gyroscopes IN GEneral Relativity) is a proposal for measuring in a ground-based laboratory the Lense-Thirring effect, known also as inertial frame dragging, that is predicted by General Relativity, and is induced by the rotation of a massive source. GINGER will consist in an array of at least three square ring lasers, mutually orthogonal, with about 6-10 m side, and located in a deep underground site, possibly the INFN - National Laboratories of Gran Sasso. The tri-axial design will provide a complete estimation of the laboratory frame angular velocity, to be compared with the Earths rotation estimate provided by IERS with respect the fixed stars frame. Large-size ring lasers have already reached a very high sensitivity, allowing for relevant geodetic measurements. The accuracy required for Lense-Thirring effect measurement is higher than 10-14 rad/s and therefore Earth angular velocity must be measured within one part in 10-9. A 3.6 m side, square ring laser, called GINGERino, has been recently installed inside the Gran Sasso underground laboratories in order to qualify the site for a future installation of GINGER. We discuss the current status of the experimental work, and in particular of the GINGERino prototype.

Origin of structural analogies and differences between the atomic structures of GeSe4 and GeS4 glasses: A first principles study.

First-principles molecular dynamics simulations based on density functional theory are employed for a comparative study of structural and bonding properties of two stoichiometrically identical chalcogenide glasses, GeSe4 and GeS4. Two periodic cells of 120 and 480 atoms are adopted. Both glasses feature a coexistence of Ge-centered tetrahedra and Se(S) homopolar connections. Results obtained for N = 480 indicate substantial differences at the level of the Se(S) environment, since Ge-Se-Se connections are more frequent than the corresponding Ge-S-S ones. The presence of a more prominent first sharp diffraction peak in the total neutron structure factor of glassy GeS4 is rationalized in terms of a higher number of large size rings, accounting for extended Ge-Se correlations. Both the electronic density of states and appropriate electronic localization tools provide evidence of a higher ionic character of Ge-S bonds when compared to Ge-Se bonds. An interesting byproduct of these investigations is the occurrence of discernible size effects that affect structural motifs involving next nearest neighbor distances, when 120 or 480 atoms are used.