Centrifugal Loading Research Articles

Modelling the vibration of tyre sidewalls

The dynamical behaviour of the sidewall has an important influence on tyre vibration characteristics. Nonetheless, it remains crudely represented in many existing models. The current work considers a geometrically accurate, two-dimensional, sidewall description, with a view to identifying potential shortcomings in the approximate formulations and identifying the physical characteristics that must be accounted for. First, the mean stress state under pressurisation and centrifugal loading is investigated. Finite-Element calculations show that, while the loaded sidewall shape remains close to a toroid, its in-plane tensions differ appreciably from the associated analytical solution. This is largely due to the inability of the anisotropic sidewall material to sustain significant azimuthal stress. An approximate analysis, based on the meridional tension alone, is therefore developed, and shown to yield accurate predictions. In conjunction with a set of formulae for the ‘engineering constants’ of the sidewall material, the approximate solutions provide a straightforward and efficient means of determining the base state for the vibration analysis. The latter is implemented via a ‘waveguide’ discretisation of a variational formulation. Its results show that, while the full geometrical description is necessary for a complete and reliable characterisation of the sidewall's vibrational properties, a one-dimensional approximation will often be satisfactory in practice. Meridional thickness variations only become important at higher frequencies (above 500Hz for the example considered here), and rotational inertia effects appear to be minor at practical vehicle speeds.

General integral equations of thermoelasticity in micromechanics of composites with imperfectly bonded interfaces

One considers a linear thermoelastic composite medium, which consists of a homogeneous matrix containing a statistically inhomogeneous random set of heterogeneities with various interface effects and subjected to essentially inhomogeneous loading by the fields of the stresses, temperature, and body forces (e.g., for a centrifugal load). The general integral equations connecting the stress and strain fields in the point being considered and the surrounding points are obtained for the random and deterministic fields of inclusions. The method is based on a centering procedure of subtraction from both sides of a new initial integral equation their statistical averages obtained without any auxiliary assumptions such as the effective field hypothesis (EFH), which is implicitly exploited in the known centering methods. The new initial integral equation is presented in a general form of perturbations introduced by the heterogeneities and taking into account both the spring-layer model and coherent imperfect one. Some particular cases, asymptotic representations, and simplifications of proposed equations as well as a model example demonstrating the essence of two-step statistical average scheme are considered. General integral equations for the doubly and triply periodical structure composites are also obtained.

Analysis of uncertainties in measurement of rotor blade tip clearance in gas turbine engine under dynamic condition

The rotor tip clearance in a gas turbine engine varies throughout the engine operating regime. It has considerable influence on the engine performance. Blade to casing rub is imminent at certain operating points of the engine. Mechanical rub at high speeds could damage the total engine hardware. A precise measurement helps to obtain the optimum engine performance with safe engine operation. In this article a typical case study related to fan clearance measurement is discussed, where indications of a proven measurement system is not in agreement with the physical event during engine test. Centrifugal, thermal, assembly and wear effects can affect tip clearance measurement. Centrifugal forces untwist the blade tip, resulting in change in the effective area of the target that is seen by capacitance sensor. Relative component growths due to thermal effect result in the displacement of the sensor from its original position. This could induce error into this measurement. Assembly errors are seen during blade to disc assembly. Wear occurs under the action of centrifugal loading and vibration in compressor blades dovetail roots that are attached to the disc. This leads to wear in involved metal surfaces and it could be a source of error in this measurement. Measurement system also has its own uncertainty. During the current work all sources of errors were evaluated. Probable actual running clearance on the engine and reasons for the mismatch in indication were successfully arrived at through analytical and experimental studies. This work has provided an insight into probable sources of errors and their treatment methodologies using analytical and experimental techniques. This has helped in identifying the changes needed in the calibration procedure, methods to reduce the measurement system uncertainty band and measurement procedure.

Hollow interference fitted multi-ring composite rotor of the superconducting attitude control and energy storage flywheel

The superconducting attitude control and energy storage flywheel is a kind of energy storage flywheel. With respect to this kind of flywheel, a rotor consisting of a hollow hub and three composite cylindrical rings in interference fitted state is presented to achieve high specific energy density. The hollow hub made of high strength steel 18Ni350 is used to change the distribution of centrifugal stress, reduce the maximum radial stress and to ensure the working gap of radial magnetic bearings and motor/generator is constant when the rotor rotates at a high rotary speed. Interference has been introduced between rings or ring and hub to avoid their delamination and eventually increase the maximum speed of the rotor. In order to find out the quantitative relationship among interference, tension force, radial pre-stress and so on, we analyzed the stress distribution of the rotor subjected to centrifugal loads, the initial stresses and displacements of the multi-rings rotor in interference fitted state by mathematical methods and finite element methods. Effects of these factors, such as interference between rings, thickness ratio of rings, different materials of rings and so on, are studied in detail to make clear how they affect the stress distribution of the interference fitted multi-ring composite rotor. The results of this study will give a useful hint for the design, test and manufacture of the composite rotor for the superconducting attitude control and energy storage flywheel.

Static and Dynamic Hypergravity Responses of Osteoblasts and Osteoclasts in Medaka Scales

Fish scales are a form of calcified tissue similar to that found in human bone. In medaka scales, we detected both osteoblasts and osteoclasts and subsequently developed a new scale assay system. Using this system, we analyzed the osteoblastic and osteoclastic responses under 2-, 3-, and 4-gravity (G) loading by both centrifugation and vibration. After loading for 10 min, the scales from centrifugal and vibration loading were incubated for 6 and 24 hrs, respectively, after which the osteoblastic and osteoclastic activities were measured. Osteoblastic activity significantly increased under 2- to 4-G loading by both centrifugation and vibration. In contrast, we found that osteoclastic activity significantly decreased under 2- and 3-G loading in response to both centrifugation and vibration. Under 4-G loading, osteoclastic activity also decreased on centrifugation, but significantly increased under 4-G loading by vibration, concomitant with markedly increased osteoblastic activity. Expression of the receptor activator of the NF-κB ligand (RANKL), an activation factor of osteoclasts expressed in osteoblasts, increased significantly under 4-G loading by vibration but was unchanged by centrifugal loading. A protein sequence similar to osteoprotegerin (OPG), which is known as an osteoclastogenesis inhibitory factor, was found in medaka using our sequence analysis. The ratio of RANKL/OPG-like mRNAs in the vibration-loaded scales was significantly higher than that in the control scales, although there was no difference between centrifugal loaded scales and the control scales. Accordingly, medaka scales provide a useful model by which to analyze bone metabolism in response to physical strain.

A Silicon Carbide Wireless Temperature Sensing System for High Temperature Applications

In this article, an extreme environment-capable temperature sensing system based on state-of-art silicon carbide (SiC) wireless electronics is presented. In conjunction with a Pt-Pb thermocouple, the SiC wireless sensor suite is operable at 450 °C while under centrifugal load greater than 1,000 g. This SiC wireless temperature sensing system is designed to be non-intrusively embedded inside the gas turbine generators, acquiring the temperature information of critical components such as turbine blades, and wirelessly transmitting the information to the receiver located outside the turbine engine. A prototype system was developed and verified up to 450 °C through high temperature lab testing. The combination of the extreme temperature SiC wireless telemetry technology and integrated harsh environment sensors will allow for condition-based in-situ maintenance of power generators and aircraft turbines in field operation, and can be applied in many other industries requiring extreme environment monitoring and maintenance.

Effects of Geometric Factors and Material Properties on Stress Behavior in Rotating Disk

In this study, effects of geometric factors and material properties are investigated on stress behavior of circular rotating disk with constant rotation in various industrial mechanisms using equilibrium equations, geometric relations and stress functions. In this way, research on a thin uniform and homogeneous circular disk under constant rotation is considered. The rotating motion produces centrifugal acceleration on each element of the rotating disk, and this rotating motion becomes the source of external loading for the mentioned problem. Additional exterior loadings are not assumed in this problem. It is comfortable to handle the centrifugal force loading by relating it to a body force density via the disk in order to increase strength (maximum stress) of circular rotating disk. Eventually, stress behavior of rotating disk is analyzed with considering geometric factors and material properties analytically. Finally, it is concluded that the mentioned factors affect on increasing and decreasing stress values of circular rotating disk under constant rotation.

Active tuned mass dampers for control of in-plane vibrations of wind turbine blades

This paper investigates the use of active tuned mass dampers (ATMDs) for the mitigation of in-plane vibrations in rotating wind turbine blades. The rotating wind turbine blades with tower interaction represent time-varying dynamical systems with periodically varying mass, stiffness, and damping matrices. The aim of this paper is to determine whether ATMDs could be used to reduce in-plane blade vibrations in wind turbines with better performance than compared with their passive counterparts. A Euler–Lagrangian wind turbine mathematical model based on energy formulation was developed for this purpose, which considers the structural dynamics of the system and the interaction between in-plane and out-of-plane vibrations. Also, the interaction between the blades and the tower including the tuned mass dampers is considered. The wind turbine with tuned mass dampers was subjected to gravity, centrifugal, and turbulent aerodynamic loadings. Investigations show promising results for the use of ATMDs in the vibration control of wind turbine blades. Copyright © 2013 John Wiley & Sons, Ltd.

417 三重相反境界要素法による遠心力を伴うメッシュレス三次元弾塑性解析(GS-1,3,12 計算力学(2))

417 三重相反境界要素法による遠心力を伴うメッシュレス三次元弾塑性解析(GS-1,3,12 計算力学(2))

Identification–Oriented Control Designs with Application to a Wind Turbine Benchmark

Wind turbines are complex dynamic systems forced by stochastic wind disturbances, gravitational, centrifugal, and gyroscopic loads. Since their aerodynamics are nonlinear, wind turbine modelling is thus challenging. Therefore, the design of control algorithms for wind turbines must account for these complexities, but without being too complex and unwieldy. Therefore, the main contribution of this study consists of providing two examples of robust and viable control designs with application to a wind turbine simulator. Due to the description of the considered process, extensive simulations of this test case and Monte–Carlo analysis are the tools for assessing experimentally the achieved features of the suggested control schemes, in terms of reliability, robustness, and stability, in the presence of modelling and measurement errors. These developed control methods are finally compared with different approaches designed for the same benchmark, in order to evaluate the properties of the considered control techniques.

RBF Neural Network Approach for Identification and Control of DC Motors

In this paper, a neural network approach for the identification and control of a separately excited direct (DC) motor (SEDCM) driving a centrifugal pump load is applied. In this application, two radial basis function neural networks (RBFNN) are used: The first is a RBFNN identifier trained offline to emulate the dynamic performance of the DC motor-load system. The second is a RBFNN controller, which is trained to make the motor speed follow a selected reference signal. Two RBFNN control schemes are proposed using direct inverse and internal model control schemes. The performance of the RBFNN identifier and controller is investigated in terms of step response, sharp changes in speed trajectory, and sudden load change, as well as changes in motor parameters. The performance of RBFNN in system identification and control has been compared with the performance of the well-known back-propagation neural network (BPNN). The simulation results show that both of the BPNN and RBFNN controllers exhibit excellent dynamic response, adapt well to changes in speed trajectory and load connected to the motor, and adapt to the variations of motor parameters. Furthermore, the simulation results show that the step response of RBFNN internal model and direct inverse controllers are identical.

Structural analysis of composite wind turbine blade using advanced beam model approach

In this paper, a structural analysis of a composite rotor blade for a small wind turbine was attempted by adopting an advanced beam model. To fulfill the general light-weight requirement, various composite materials were used. The present beam modeling approach included two-dimensional cross-sectional analyses and a geometrically exact one-dimensional beam analysis. These efforts led to a much lower cost in terms of computational time and resources. Thus, it was found to be appropriate for iterative evaluations of blade design candidates. However, it was also expected that the proposed approach may be limited in terms of its ability to model complicated three-dimensional blade structures. Thus, to evaluate the present approach with regard to such a limitation, a threedimensional finite element model of such a blade was constructed using CATIA V5 and MSC.PATRAN. For a precise simulation of the actual operating conditions, the influences of aerodynamic and centrifugal loads were considered simultaneously for a static analysis as part of both analyses. Finally, the advantages and limitations of the current approach were investigated and discussed through comparisons with the results by NASTRAN. Possible improvements in terms of the accuracy of the proposed approach were also extracted and discussed.

Effect of Viscosity on the Separation Ability of a Hydrocyclone

On bases of numerical simulation and theoretical analysis, two cases of media, water and slurry (a kind of pseudoplastic power-law fluids), were used in the same hydrocyclone under the same operating condition. The Compare results show that the effect of the medium viscosity on the radial-velocity profile is slight; on the other hand, the effect of the media viscosity on the tangential-velocity profiles is important. The increase of the media viscosity produces not only the increase of the viscous resistance but also the steep reducing of the peak value of tangential-velocity profiles, which means that the inward viscous force loading upon the particles are enforced, on the other hand , the outward centrifugal force loading on the particles reduces greatly. The increase of the media viscosity leads to the great decrease of the separation ability of a hydrocyclone.

Frictional Contact Problem Study on Compressor by a Parametric Quadratic Programming Method

A locomotive-type turbocharger compressor with 24 blades under combined centrifugal and interference-fit loading was considered in the numerical analysis. The solution of elastoplastic frictional contact problems belongs to the unspecified boundary problems where the interaction between two kinds of nonlinearities should occur. To save the time cost in the numerical computation, multi-substructure technique was adopted in the structural modeling. The effect of fit tolerance, wall thickness of shaft sleeve and rotational speed on the contact stress was discussed in detail in the numerical computation. To decrease the difficulty of the assembling process and make sure the safety of the working state, the amount of interference between the shaft sleeve and shaft by press-fitting should be controlled strictly to avoid the rapid increase of the contact stress. The numerical results show the high accuracy and good convergence of the algorithm presented here. The study play a referenced role in deciding the proper fit tolerance and improving design and manufacturing technology of compressor impellers.

Geometrical optimization of a hingeless deployment system for an active rotor blade

Deployment systems for the Gurney flap need to sustain large centrifugal loads and vibrations while maintaining precisely the displacement under aerodynamic loading. Designing such a mechanism relies on both the actuation technology and the link that transmits motion to the control surface. Flexible beams and piezoelectric patch actuators have been chosen as components to design this mechanism. Flexible beams provide a hingeless robust structure onto which the piezoelectric actuators are bonded. A candidate topology is determined by investigating the compliance of a simple wire structure with beam elements. A parameterized finite element model is then built and optimized for displacement and force through surrogate optimization.

Nonlinear dynamics of rotating box FGM beams using nonlinear normal modes

In this work an analysis is performed on the nonlinear planar vibrations of a functionally graded beam subjected to a combined thermal and harmonic transverse load in the presence of internal resonance. Adopting the direct perturbation MMS technique, the partial differential equations of motion of the beam are reduced to sets of first-order nonlinear modulation equations in terms of the complex modes of the beam. The assumption of steady-state values of centrifugal loads is evaluated. It has to be said that there is a lack of information about modeling of rotating box beams made of functionally graded materials (FGMs) under thermo-mechanical loads. The influence of the transverse load amplitude and the internal detuning parameter on the strength of nonlinear modal interaction is illustrated. It is also shown that the system exhibits periodic and quasiperiodic responses for a typical range of parameter values.

Design theory and optimization method of a hybrid composite rotor for an ultracentrifuge

A centrifuge rotor, the most important component that determines a centrifuge's capability, has to sustain severe centrifugal loading. Since the centrifugal force is proportional to the material density, fiber reinforced composites having high specific strengths, i.e. the ratio of their strengths to their densities, are suitable materials for designing a centrifuge. However, unfortunately fibrous composites do not have those superior specific strengths in all directions, their transverse strength being very weak and almost similar to that of pure matrix materials. Therefore, in order to overcome such a weakness of the fibrous composites, it is very important to understand the stress relations between constituent materials of a hybrid composite rotor with respect to their dimensional parameters and material properties. In this study, deriving analytical solutions for a rotating hybrid composite disc as well as considering stress concentration in the disc by FE (finite element) analysis, we developed an optimization method that can maximize the performance of a hybrid composite rotor.

Effects of centrifugal load on tooth contact stresses and bending stresses of thin-rimmed spur gears with inclined webs

Firstly, centrifugal deformation and stresses of thin-rimmed spur gears with inclined webs are analyzed in this paper with the finite element method (FEM) when the gears run at very high speeds. It was found that centrifugal load has a significant effect on tooth root bending stresses of the thin-rimmed gears at high speeds. So, it is necessary to consider the effect of the centrifugal load on tooth root bending stresses into bending strength calculations of the thin-rimmed gears when the gear speed is greater than 10,000min−1. Secondly, loaded tooth contact analyses (LTCA) are conducted for the thin-rimmed inclined web gears when they are deformed by the centrifugal load and engaged with a solid mating gear. FEM combined with a mathematical programming method is used to do the analyses. Tooth contact stresses and root bending stresses of the thin-rimmed gears are calculated under a torque load. It was found that the centrifugal deformation of the thin-rimmed inclined web gears almost has no effects on the tooth contact stresses and root bending stresses. This conclusion is different from the one obtained from the thin-rimmed straight web gears. Li (2008) [5] reported that the centrifugal deformation of the thin-rimmed straight web gears had significant effects on the tooth contact stresses and root bending stresses of the contact teeth. Finally, it is explained why the centrifugal deformation of the thin-rimmed inclined web gears does not affect the tooth contact stresses and root bending stresses.

Analysis of the contact stresses in curvic couplings of gas turbine in a blade-off event

The contact pressure distribution of the curvic couplings in a heavy duty gas turbine under a blade-off load condition is investigated in a three-dimensional finite element model. Several blade-off positions on each stage disk may develop the different characters on the contact pressure distributions of the curvic couplings during the application of a blade-off load. Both the position and magnitude of the applied blade-off load and the distribution of the spindle bolts have an effect on the contact pressure distribution of the curvic couplings. Further the contact stress on the left and right sides of the teeth develops different characters during the application of torque load following not only a normal centrifugal load but also a blade-off load which produces a unbalanced equivalent bending force. Furthermore the stiffness of the connection body part of the rotor between the compressor end and the turbine end associated with its section thickness is crucial in deciding the contact stress distribution on the curvic couplings. This analysis shows a change in the magnitude of contact stress of each set of the curvic couplings.

Effect of temperature on the strength of a centrifugal compressor impeller for a turbocharger

High pressure ratio turbocharger technology is used to decrease fuel consumption, reduce emissions and improve power density of an internal combustion engine. The centrifugal compressor is the turbocharger’s core component. The reliability of its impeller becomes critical as the pressure ratio gets higher and the temperature starts playing an important role. In order to study the effect of the flow temperature on the reliability of a centrifugal compressor impeller, solid–fluid coupling is used to calculate the temperature distribution on the impeller surface. This temperature distribution is then applied as boundary condition in three-dimensional finite element analysis to analyze impeller stress. The results show that the percentage of impeller stress caused by thermal load remains approximately constant (about 2%) at different pressure ratios, which does not increase with increasing pressure ratio. Centrifugal load plays an absolutely critical role in the impeller stress at different pressure ratios. High pressure ratio also leads to an increase of air temperature, which causes higher material temperature and consequently the lower ultimate tensile strength of the impeller material. The maximum compressor pressure ratio which the impeller can bear decreases from 4.6 to 4.2 for the researched compressor if the effect of temperature on the ultimate tensile strength was considered. That means the effect of the temperature on compressor impeller strength and reliability at high pressure ratio should be considered while it can be ignored at low pressure ratio.