Ring Deformation Research Articles

An improved preloaded Curvic coupling model for rotordynamic analyses

Curvic couplings are commonly utilized in aircraft engines and large gas turbines for high load capacity, precision centering of stacked components in rotating assemblies. The couplings have non-axisymmetric, complex curved mating contact surfaces, which transmit torque, moment and force. Coupling contact surface roughness, and tooth and ring deformations introduce local lateral flexibilities, compared with a continuous beam model, and consequently affect rotordynamic vibration predictions. A novel approach of modeling the Curvic coupling is proposed which combines a GW contact model with a 3D solid element model of flexible teeth and coupling rings. This improves on similar approaches that assume rigid teeth and rings or omits a surface roughness – asperity model. Comparisons of the various models with experimental measurements of free-free natural frequencies of an axially preloaded shaft, demonstrate a marked improvement in accuracy with the proposed approach. A parametric study is performed which varies tooth contact pattern, tooth number, pressure angle, half pitch number, and tooth rigidity to evaluate their effects on vibration and stress. The proposed approach is also applied to an industrial rotor to illustrate the effect of the new Curvic coupling model on critical speeds. The higher fidelity flexible tooth model presented shows a significant change in critical speed relative to the rigid tooth model from the literature.

Evaluation on fire resistance of composite segmental lining for shield tunnel

This paper developed a FEM modeling to evaluate the composite segmental lining's fire resistance by simulating the thermo-mechanical behavior under the fire conditions. The mechanical and thermal properties related to concrete and steel were selected and introduced in detail. FE models of the single composite segment, segmental joint, and the full segmental lining were then established in ABAQUS. The verification of the models was conducted compared with the results from three experiments. Based on the calibrated FE models, the bearing capacity was first investigated for all three models at normal temperature and after the fire. The temperature distribution and deformation modes were subsequently examined. An in-depth discussion was conducted on the concrete damage and the corresponding protection methods. A comparison was finally carried out to detect the fire resistance between the plain concrete segment and the composite segment. The results showed that both the bearing capacity and the composite segmental joint's flexibility might significantly decrease due to the fire loading. The concrete damage was mainly caused by the rising temperature and the corresponding deformation of the whole lining ring with the expansion of different components during the fire. The restraint provided by the covered steel plates to the concrete inside led to the enhancement of the fire resistance for the composite segment. The proposed FEM model can be applied to simulate the thermo-mechanical behavior of other types of composite structures with reasonable material properties.

Research on Air-floating Gravity Unloading System of Large-scale Inter-mechanisms

Aiming at the unloading requirements of heavy load, high stiffness and low damping of the upper mechanism during ground separation and unlocking simulation test of a certain mechanism product, a gravity unloading system based on air flotation was developed. The system can not only realize the gravity unloading of the large heavy-duty mechanism, and follow the upper mechanism to rotate at any speed, but also has small rotation resistance and stable movement. It has been verified by experiments that the air-floating gravity unloading system based on the air-floating method can realize 100% gravity unloading of products over 1 ton, and follow the upper mechanism to perform stable rotating motion, and the support deformation of the air-floating ring is better than 0.8um. The rotational resistance torque is better than 0.2Nm. To meet the unloading requirements of high stiffness and low damping of the upper mechanism, the in-depth research on the ground simulation system of the separation and unlocking between the two structures has a certain research reference value.

Study on Transverse Deformation Characteristics of a Shield Tunnel under Earth Pressure by Refined Finite Element Analyses

We establish an elaborate numerical model with which to investigate the deformation characteristics of segmental lining. The numerical model contains reinforcement and connecting bolts that previous numerical studies have generally neglected. We validated the model parameters using a full-scale model test result. Based on this numerical model, we studied the deformation characteristics of segmental lining. Convergence, joint deformation, bolt stress, and reinforcement stress were systematically analyzed under different loading conditions. Furthermore, we discuss the relationships between convergence and joint opening, bolt stress and joint opening. The deformation characteristics of segmental lining are revealed. When the lining is deformed by earth pressure, plastic hinges form at the joints. The segment rotates around the plastic hinge, which is the main reason for segmental lining deformation under earth pressure. Horizontal convergence is a single index to reflect the deformation of tunnel rings, representing the overall deformation of the ring to a certain extent but not the deformation characteristics of the joint. When the loading conditions differ, the relationship between joint opening and horizontal convergence is consistent for some joints and inconsistent for others.

Synthesis, single crystal, electrochemical and study of fluorogenic dibenzodiaza-crown-appended with bis(ZnTPP) azo-tweezer and spectroscopic elucidation of photo-induced macrocycle-deformation-based chromotropism

In the present research, a new tweezer T bearing azobenzene linker 1 was prepared, characterized by applying FT-IR spectroscopy, fluorescence spectroscopy, UV–visible spectroscopy, and elemental analysis 1H and 13C{1H} NMR. T crystals were obtained by reaction of 1 with ZnTPP in CHCl3/acetone. Under irradiation with a mercury lamp to achieve the trans-to-cis isomerization, a dramatic color change from violet to green in chloroform was observed. The X-ray crystallography of T revealed an observable macroring deformation of the ZnTPP for the trans isomer. We observed a deviation of 0.11 Å from planarity for the least-squares plane of ZnTPP owing to the axial coordination by the pyridine derivative of the parent dibenzodiaza-crown moieties of 1. Hence, we suggested the existence of oop deformations for this photo-responsive chromogenic colour change. Fluorescence (FL) spectrophotometry was applied to elucidate the observed colour change in terms of the ring deformation of ZnTPP, resulting from the trans-to-cis photo-isomerization of the azo-linker moiety of L. This is the first report on the gradual reversible photochromism of ZnTPP moiety, based on the macrocycle-deformation mechanism, wherein colour color change of T was reversible at 60 °C. The CVs of ZnTPP in various concentrations of 1 were examined. The titration of ZnTPP by 1 displays the positive shift of the oxidation potential of ZnTPP in the CV, indicating the complex formation between ZnTPP and 1 in CH2Cl2.

Friction Performance Analysis of Reactor Coolant Pump Shaft Seal Based on Sensor and Computer Simulation

In recent years, the state has put forward a grand plan to develop nuclear power in order to control environmental pollution and carbon emissions. In nuclear power plants, mechanical seals for reactor coolant pump play an important role in nuclear power safety production. However, China cannot independently produce such mechanical seals, and they are blocked by foreign related technologies, which has seriously affected China’s nuclear power development plan and the overall safety of China’s nuclear power operation. Under this background, this paper studies the friction performance of the shaft seal of the reactor coolant pump, uses the sensor to obtain the data of friction factors such as low-pressure leakage, effectively monitors the low-pressure leakage through calculation and simulation modeling, truly reflects the operating state of the reactor coolant pump, and provides a new research direction and experimental basis for further analysis of the friction performance of the shaft seal of the reactor coolant pump. The results show that under the joint action of the pressure difference and the force generated by the deformation of the moving ring plate, the cone angle formed on the seal end face is 1300.9 μ convergence gap of rad. When the inlet water temperature is 65°C, the leakage rate is 1867.8 L/h. The deformation of the moving ring deformation ring plate can hinder the increase of the deformation cone angle of the moving ring. The greater the thickness of the moving ring deformation ring plate, the greater the seal leakage rate. The inlet temperature of the sealing medium and the friction performance of the material also have an impact on the sealing performance.

Iterated Hopf Ore extensions in positive characteristic

Iterated Hopf Ore extensions (IHOEs) over an algebraically closed base field \Bbbk of positive characteristic p are studied. We show that every IHOE over \Bbbk satisfies a polynomial identity (PI), with PI-degree a power of p , and that it is a filtered deformation of a commutative polynomial ring. We classify all 2 -step IHOEs over \Bbbk , thus generalising the classification of 2 -dimensional connected unipotent algebraic groups over \Bbbk . Further properties of 2 -step IHOEs are described: for example their simple modules are classified, and every 2 -step IHOE is shown to possess a large Hopf center and hence an analog of the restricted enveloping algebra of a Lie \Bbbk -algebra. As one of a number of questions listed, we propose that such a restricted Hopf algebra may exist for every IHOE over \Bbbk .

Design of Pulsed Magnet for Adjusting the Residual Stress Field in Large-Size Aluminum Alloy Rings

Large-size aluminum alloy rings are widely used as connector, transition ring and reinforcing structure in aerospace and other fields. However, the residual stress introduced during the manufacturing process lead to the structural instability and poor mechanical properties of the aluminum alloy rings. In this paper, pulsed electromagnetic force is used to deform the aluminum alloy rings into plastic state and eliminate the residual stress in the workpieces. The residual stress in a large-size aluminum alloy ring with an outer diameter of 720 mm, a wall thickness of 60 mm, and a height of 60 mm was studied in this paper. To meet the demand of high energy input for bulging the alloy ring, an actuator coil with high voltage insulation and tough inner support was optimized designed by finite element software COMSOL Multiphysics. It was found that adding a steel ring with a truncated gap inside the epoxy skeleton can improve the compression strength of the magnet and increase the plastic deformation of the aluminum alloy ring. Besides, simulation results showed that multiple discharges can reduce the discharge voltage, which can effectively increase the service life and safety of the magnet system.

Raman spectroscopy and X‐ray diffraction of diphenylphosphoryl azide under high pressures

AbstractDiphenylphosphoryl azide ((C6H5O)2P(O)N3, DPPA) was studied by in situ Raman scattering spectroscopy and synchrotron angle‐dispersive X‐ray diffraction (ADXRD) technologies up to 11.6 GPa at room temperature. The analyses of Raman spectra revealed that the liquid DPPA transformed from Phase I to Phase II at 0.4 GPa and went to Phase III at 1.3 GPa. The first phase transition was attributed to the change of molecular conformation, and the second phase transition was induced by the deformation of benzene rings. The XRD results suggested that DPPA remained in a liquid state during the two phase transitions. The azide group became increasingly asymmetric under pressure and decomposed at 11.6 GPa. The low decomposition pressure of the azide group is conducive to the formation of polymeric nitrogen. Exploring the behaviors of the azide group under pressure might be helpful for understanding the potential application of DPPA in the synthesis of high energy density materials (HEDMs).

Deformation behaviors and failure mechanism of segmental RC lining under unloading condition

A shield tunnel lining structure is a type of complex structure system, and few systematic studies have been performed on its transverse deformation response under upper unloading conditions. In this paper, a sophisticated numerical model of segmental rings considering rebars, bolts, sealing grooves and caulking grooves was built to analyze the transverse deformation response of shield tunnels under upper unloading conditions. The failure mechanism of the segmental ring was studied based on the plastic hinge theory, and the controlling index of convergence deformation was proposed for engineering applications. Meanwhile, the structural response and failure process of the segmental ring under unloading were compared with those under continuous loading conditions. The results show that with the decrease in load, the tunnel deformation mode changes from the horizontal ellipse to the vertical ellipse, and the maximum vertical convergence deformation of the segmental ring is 46.3 mm when the unloading ratio is 0.68. The bending moment and axial force of the segmental ring decreases, subsequently reverses and keeps increasing until the structure failure. Concrete cracks mainly appear on the waist, crown and invert of the shield tunnel and penetrate along the thickness and longitudinal directions. The plastic hinge successively forms at 73°, 287°, 180°, 8°, and 352° locations during unloading. The variation in the segmental ring stiffness under the overlying unloading condition first recovers and subsequently continues decreasing until structural failure.

Vibronic fine structure in the nitrogen 1s photoelectron spectra of molecules from Franck-Condon simulations: Azines

Vibronic coupling plays a pivotal role in molecular spectroscopy. We present a theoretical study on vibrationally resolved x-ray photoelectron spectra (XPS) of seven azines (${\mathrm{C}}_{x}{\mathrm{H}}_{y}{\mathrm{N}}_{z}$; pyridine, three diazines, two triazines, and one tetrazine) at the nitrogen $1s$ edge, to explore the vibronic coupling effects as influenced by consecutive replacement of the CH group with a N atom. Franck-Condon simulations were performed with the Duschinsky rotation effect included, where the electronic structure was calculated by the density functional theory. Validations on pyrimidine show good agreement with the experiment, weak functional dependence, and weak mode mixing effect. We observed an evident blue shift in binding energies with the increasing number of N atoms in this series, together with molecule-dependent vibronic fine structures. These molecules have either ${\mathrm{C}}_{\text{2v}}$ or ${\mathrm{C}}_{\text{s}}$ molecular symmetry at the optimized core-ionized geometries. Franck-Condon-active vibrational modes were identified to be low frequency (500--1650 ${\mathrm{cm}}^{\ensuremath{-}1}$), totally symmetric (${A}_{1}$ or ${A}^{\ensuremath{'}}$), in-plane ring deformation modes. Core ionization on ${\mathrm{N}}^{*}$ always leads to elongation of the ${\mathrm{N}}^{*}\ensuremath{-}\mathrm{N}$ bond length, accompanied by an increase of the $\ensuremath{\angle}\mathrm{C}\ensuremath{-}{\mathrm{N}}^{*}\ensuremath{-}X$ bond angle ($X=\mathrm{C}$, N). Our study predicts accurate theoretical reference spectra for the azine family and provides useful information on the properties of the core-ionized states as influenced by the structural change of $\mathrm{CH}\ensuremath{\leftrightarrow}\mathrm{N}$ replacement.

Vibrationally-Resolved X-ray Photoelectron Spectra of Six Polycyclic Aromatic Hydrocarbons from First-Principles Simulations.

Vibrationally resolved C 1s X-ray photoelectron spectra (XPS) of a series of six polycyclic aromatic hydrocarbons (PAHs; phenanthrene, coronene, naphthalene, anthracene, tetracene, and pentacene) were computed by combining the full core hole density functional theory and the Franck-Condon simulations with the inclusion of the Duschinsky rotation effect. Simulated spectra of phenanthrene, coronene, and naphthalene agree well with experiments both in core binding energies (BEs) and profiles, which validate the accuracy of our predictions for the rest molecules with no high-resolution experiments. We found that three types of carbons i (inner C), p (peripheral C bonded to three C atoms), and h (peripheral C bonded to an H atom) show decreasing BEs. In linear PAHs (the latter four), h-type carbons further split into h1 or h2 (on inner or edge benzene ring) subtypes with chemical shifts of ca. 0.2-0.4 eV. All major Franck-Condon-active modes are characterized to be in-plane vibrations: low-frequency (<800 cm-1) C-C ring deformation modes play an essential role in determining the peak asymmetries; and for each h-type carbon a high-frequency (ca. 3600 cm-1) C*-H stretching mode is responsible for the high-energy tail. We found that core ionization leads to reduction of all C*-C and C*-H bond lengths and ring deformation with a definite direction. Based on theoretical spectra of four linear PAHs, we found asymptotic relations and anticipated possible spectral features for even larger linear PAHs. Our calculations provide accurate reference spectra for XPS characterizations of PAHs, which are useful in understanding the vibronic coupling effects in this family.

3D numerical investigation on response of shield tunnel under combined effects of fire and structural loading

As a significant infrastructure hazard, fires in tunnels have brought about a great deal of economic and social losses each year. From a holistic tunneling design perspective, it is essential to predict accurately the displacements and internal forces of the lining under coupled effects of elevated temperatures and various loading conditions. To this end, an elaborate three-dimensional (3D) numerical model, which incorporated the concrete segments, reinforcing rebars and connecting bolts, was established to investigate the deformation and failure mechanism of the segmental ring in shield tunnels under coupled effects of fire and structural loading. The validation based on the experimental results of segment lining and joints shows that the established model can be employed to analyze the entire tunnel ring structures. Two types of numerical models, i.e., single-ring and three-ring models, were established and the thermo-mechanical coupled performance were examined. Based on the verified model, the general temperature field and deformation distribution were described and elaborated. With respect to the significant insights on mechanical behaviors of shield tunnel rings in fire, the results of inner force redistribution, the joint opening elaboration and the failure mechanism of the shield tunnel structure under fire effects and initial loadings were further discussed. The results of this study can provide valuable guidance for the fire resistance design in the tunnel.

Modelling and numerical simulation of magnetostrictive materials for reduction of friction

This study aims to enhance the multifunctional properties in top piston rings by adding magnetostrictive materials to reduce friction between them and the cylinder lining. The magnetostrictive effect will create mechanical deformations in piston rings, with consequent friction reduction. The present study consisted of a finite element analysis (FEA), using COMSOL Multiphysics® software, where both the amplitude of deformation and the reduction of the contact forces were analysed. These variables are useful to predict the ability to introduce mechanical vibrations in piston rings that can lead to the reduction of friction. The results showed a reduction of the contact force below 4%, and deformation amplitudes in the sliding plane of 6.50 μm and 3.20 μm, approximately, in the axial and circumferential directions, respectively. Those results are promising, enhancing the potential of smart materials and magnetostrictive effects to create mechanical vibrations and reduce friction in piston ring structures.

Dynamic characteristics of elastic ring squeeze film damper coupled high-speed ball bearings

This paper explores an elastic ring squeeze film damper (ERSFD) model incorporating high-speed ball bearings to study the journal dynamics at different rotor operating speeds and squirrel cage stiffness. Firstly, dynamic model of the ERSFD is established. The journal works under ball-outer raceway excitation rather than rotor unbalance force. Bearing high-speed characteristics including ball centrifugal force, contact angle change and heavy thrust-applied load are outlined in quasi-static model when deriving bearing force. Oil film pressure is governed by the Reynolds equation and solved iteratively using the central finite difference scheme. Flow performance through the orifice and its effect on the oil film pressure are analyzed using computational fluid dynamics (CFD) technique. Elastic ring deformation is addressed using a thin-walled ring model. Secondly, squirrel cage stiffness and rotor operating speeds were chosen as influence parameters to numerically examine the journal steady-state and transient dynamics, and finally the center orbit and vibration of the journal were experimentally measured. The results demonstrate that an increase in squirrel cage stiffness enables the journal to orbit at small size but leads to higher transmissibility. Small squirrel cage stiffness and rotor operating speed result in high amplitude and velocity oscillations and destabilize the journal; alternatively, higher squirrel cage stiffness is ineffective in transmissibility attenuation regardless of rotor operating speed. It was concluded that a small squirrel cage stiffness cooperating with high rotor operating speed contributes to stabilize journal and attenuate vibration effectively.

Degradation of β-lactam antibiotic ampicillin using sustainable microbial peroxide producing cell system

The enormous use of synthetic antibiotic and personal care products has impacted the natural microbiome and ecosystem. Overtime, treatment technologies developed suffered due to incomplete removal hence, a pilot dual-chambered microbial peroxide-producing cell that degrades ampicillin catalyzed by homogenous Fenton-reaction was designed. The system reported maximum current at 16.714 ± 0.048 µAcm−2, power output of 1.956 ± 0.015 mW m−2; 88 ± 2.90 mM of H2O2 generation with Na2SO4 that degraded 95.9 ± 3.00 to 97.8 ± 3.20% of 10 mg L−1ampicillin within 72 hrs with electro-active Shewanella putrefaciens. An E. coli bioactivity assay with ampicillin exhibited no sensitivity zone due to the loss of activity. Analytical spectroscopic studies reveal β-Lactam ring deformation; Liquid Chromatography-Mass Spectroscopy clearly shows the presence of degradation metabolites. A sustainable wastewater treatment with 72 ± 4.5% reduction in anodic chemical oxygen demand was achieved. Present results designate the technology, as promising for effective antibiotics removal for wastewater treatment concomitant with electricity generation.

Impact Response of a Ring on Viscoelastic Foundation

This paper studies the transient responses of an elastic ring on a viscoelastic foundation (RoVEF) to suddenly applied loading. The RoVEF is a mechanical model established for analysing the dynamic behaviour of a flexible crashworthy structure (FCS) applied to bridge piers against ship-impact. Details of the RoVEF model is given, from which the free vibration modes of the structure are formulated. Two key parameters dominating the dynamic behavior of RoVEF, namely the ratio of the foundation stiffness to the ring's flexural rigidity λ and the foundation viscous coefficient η, are identified. The dynamic responses of RoVEF to external impact loadings are solved by using the modal superposition method. It is shown that as λ increases, the ring is flexible and its deformation is more localized. The η parameter facilitates the decaying of the ring's deformation to its equilibrium value. For an FCS with a relatively strong outer ring (λ<0.5), its impact responses can be approximated as a single degree-of-freedom mass-spring-damper system, in which the equivalent mass, spring stiffness and viscous coefficient are given in explicit forms.

Experimental and simulation study on the hysteretic behavior of double-ring joints for a single-layer grid shell under cyclic eccentric loading

Based on the mechanical characteristics of assembled joints in a single-layer grid shell, a cyclic eccentric loading method was designed to study the hysteretic behavior of double-ring joints under the action of axial force and moment through experiment and finite element analysis. The effects of structural parameters and axial force eccentric distance on the failure mode, hysteretic behavior and energy-dissipating capacity of double-ring joints were explored, which laid a foundation for the research on dynamic collapse properties and shape optimization of grid shell. The following conclusions were obtained: 1) Two main failure modes occurred for double-ring joints: the fracture of the bolt and the fracture of the central ring at the bolt hole. The failure mode was affected by the axial force. 2) All the hysteretic loops included five stages, and the plastic deformation of the central ring improved the energy-dissipating capacity of the joint. 3) Under the action of eccentric compression with eccentric distance δ ≤ 80 mm and eccentric tension, with increasing eccentric distance, the rotational stiffness and ultimate bending moment increases. Under the action of eccentric compression with eccentric distance δ > 80 mm, the eccentric distance has little effect on the rotational stiffness and ultimate bending moment.

The ribbed-annular dome's upper tier model stability experimental studies

Abstract. Purpose. The work’s aim is to check the stability loss hypothesis with the snap-through effect of the ribbed-annular dome's upper tier on a full-scale model by experimental tests, and confirming the nonlinear tier's work under external load. Methodology. The ribbed-ring dome circumscribe in the plan as a circle with a diameter of 18 m with the dome rise ratio to the span - 1/4, which consisted of 8 ribs and had 6 tiers in height, was taken as an dome-model analog.The upper tier of the dome is bounded by the lower ring, which is the upper ring for the tier below, and the dome's upper support ring.Tier rings and ribs are made of steel closed bent welded profiles with rectangular cross section. As a dome's upper tier model, it was decided to use the von-Mises truss as a popular model for two-rod inclined systems' theoretical stability studies, which allows modeling these systems nonlinear behavior. The classic von-Mises truss using in modeling the dome's upper tier behavior is associated with a number of problems.First, the tier is a three-dimensional system with eight rods, so it was decided to model the tier with an equivalent low-pitched truss, which is 1/4 of the upper tier.Secondly, the lower tier ring has limited rigidity and can be deformed, while the classic truss has fixed supports, which is why it was decided to add elastic horizontal supports to the classic von-Mises truss model.Horizontal elastic supports were performed as steel pair puffs and were simulated the dome's upper tier lower support ring deformations. Findings. The obtained data primary and secondary processing, and the full-scale experiment results analysis were carried out. The ribbed-annular dome's upper tier nonlinear deformations nature under the external concentrated vertical load action in the ridge node was confirmed.It was established that in the ridge joint the upper tier's stability loss nature has the snap-through effect. Scientific innovation. The deformation dependencies for the equivalent von-Mises truss with elastic supports with the help of full-scale experimentwere obtained. A comparison of the equivalent truss' behavior experimental studies results with the existing theoretical studies' results was made. The experimental and theoretical studies results analysis confirmed the experimental data results reliability and analytical expressions feasibility use for the preliminary assessment of von-Mises truss' with elastic supports stability. Practical value. The obtained results of experimental research allow creating tools for designers to increase the dome structures reliability.

Noise Identification for an Automotive Wheel Bearing

In this study, we identified the noise generated from automotive wheel bearings, which has recently emerged as a new problem in electric vehicles. The wheel bearing assembly considered in this study consists of a wheel bearing, dust shield, and knuckle, which are fastened with bolts. To obtain the noise characteristics of the wheel bearing, the noise and vibration were experimentally measured when the bearing rotated. Additionally, the natural frequencies and mode shapes of the main components of the bearing were acquired via modal testing. By comparing the obtained natural frequencies with the peak frequencies of the measured noise and vibration signals, we identified where the noise radiated. To specifically identify bearing defects, a finite element analysis model was established, and the deformation of the bearing under load was analyzed. Based on the analysis, we determined that the deformation of the outer ring in an outboard row, which resulted from bolt fastening, leads to noise and vibration in the wheel bearing.