Flexible Mounts Research Articles

Analysis of the response of wind-induced vibrations on flexible photovoltaic mounts

Abstract This article investigates a flexible photovoltaic bracket’s response to wind vibration. A finite element model is established using SAP2000 software for time course analysis. Representative units and nodes were selected to analyze internal force response, displacement response, and acceleration response. The prestress and span change rule of the flexible photovoltaic bracket are also explored, and quantitative research is conducted on the size of prestress and span size. The magnitude of the prestress affects a structure’s responsiveness to wind vibration. As prestress grows, so do deflection and acceleration, and the rate at which axial force is increasing also increases. Conversely, when prestress increases, the rate of deflection reduction falls. Consequently, considering the prestress size, it is advised that 50-kN prestressing be used for the support and wind cables. As the span rises, so do the mid-span span and the axial force of the wind cables, while acceleration also increases. The rate of mid-span deflection increases gradually with the flexible PV mount span, but the rate of axial force increase decreases. It is recommended to limit the span to below 50 m.

Static and Dynamic Response Analysis of Flexible Photovoltaic Mounts

Static and Dynamic Response Analysis of Flexible Photovoltaic Mounts

"One in the breech, five in the magazine": British Aircrew Armament of the First World War

Prior to the successful adaptation of machine guns to military aircraft by means of fixed or flexible mounts, pilots and observers wishing to attack or defend themselves from enemy aircraft were obliged to make use of small arms—pistols, rifles, and shotguns. Whereas a body of research into those armaments integrated into aircraft exists, no dedicated study of aircrew weapons has thus far been published. In an effort to shed light on this little-understood aspect of firearms history, this article summarises the small arms, other than machine guns, known to have seen air service with the British Army’s Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS) during the first two years of the First World War (1914–1918). It also addresses, as far as is practicable, their usage and effectiveness with reference to period examples.

A Theoretical Investigation of the Influence of Powertrain Mounts on Transmission Torsional Dynamics

This paper investigates the effect of the powertrain mounting system on the linear and nonlinear torsional dynamical behaviour of a transmission system. To this aim, two dynamic models, one with rigid mounts and the other with flexible mounts, are presented and compared: the first model considers only the torsional dynamics of transmission and driveline, while the second model includes also a 3 degrees-of-freedom powertrain block. The mechanical coupling and interaction between the powertrain block and transmission system is discussed and formulated. These models are then analyzed in terms of vibrational mode shapes, natural frequencies and Frequency Response Functions (FRFs); a sensitivity analysis of the main transmission parameters, e.g. the gear ratio, is also presented. From the comparison of the two simulated configurations (with and without powertrain mounts) both in time and frequency domain, a significant interaction between the two subsystems is noticed, particularly in the vehicle acceleration signal. Neglecting the powertrain mounts may lead to underestimating the real vibration level. A nonlinear model of a dual clutch transmission, including the main backlashes present along the transmission path (clutch spline, gear meshes, synchronizers), is coupled to the powertrain mounting system model. Finally, the effect of mount stiffness on transmission NVH during critical manoeuvres is shown.

Simulation of Aeroelastic Limit-Cycle Oscillations of Aircraft Wings with Stores

Aircraft wings carrying stores are susceptible to nonlinear aeroelastic limit-cycle oscillations, which can lead to reduced flight and mission performance. Limit-cycle-oscillation dynamics and control simulation studies, although of great importance, are often based on simplified typical-section airfoil models. In this work, the more accurate beam–rod representation is used to capture the spanwise varying displacement of a wing with store. The spanwise variation of wing geometry and structural properties, as well as the presence of multiple stores on rigid or flexible mounts, is efficiently modeled by the primitive-modes approach. Aeroelastic limit-cycle oscillation due to structural nonlinearity is demonstrated via time-marching simulations, as well as the computationally more efficient harmonic-balance method. Some novel forms of limit-cycle-oscillation behavior are observed as the model parameters are varied, and these are explained in terms of the flutter/divergence properties of the base linear aeroelastic system.

Effects of internal mass distribution and its isolation on the acoustic characteristics of a submerged hull

The primary aim of machinery isolation in marine vessels is to isolate structural vibration of the onboard machinery from the hull and to reduce far-field radiation of underwater noise. A substantial proportion of the total submarine mass is on flexible mounts that isolate supported masses from the hull at frequencies above the mounting system resonant frequency. This reduces the dynamically effective mass of the hull and affects the signature of the marine vessel due to propeller excitation. A fully coupled finite element/boundary element (FE/BE) model has been developed to investigate the effect of mass distribution and isolation in a submerged hull. The finite element model of the structure includes internal structures to represent the machinery and other flexibly mounted components. Changes in the radiated sound power demonstrate the effect of machinery isolation on the acoustic signature of the submerged hull due to the external propeller forces. Results are also presented to show how the arrangement of flexible mounts for a large internal structure can influence the radiation due to machinery forces.

서보라이트 픽스쳐의 진동 특성 개선 방법

This paper presents a method to improve vibration characteristics of servo track write (STW) fixture. STW fixtures supported by flexible mounts are subject to various vibration sources. Using Finite element analysis (FEA) vibration modes of the fixture are identified. The FEA results suggest certain vibration modes be reduced through design change of flexible mounts to improve vibration responses of the fixture. Based on layered flexible mounts theory a parametric study on shear and bending stiffness is performed to obtain a suitable flexible mount design leading to increased resistance to rocking motion. Experiments confirm improvement of vibration characteristics and drive performance through new mounts design.

Advanced measurement of rotor vibration in electric drives

The combination of microelectronic acceleration transducers and an RF telemetry link can provide a reliable means of measuring shaft vibrations of electric drives. Clear advantages include the possibility of installing the instrumentation into currently existing motor systems without any need to use flexible couplings or mounts. The proposed system covers frequencies up to several kilohertz and can handle torque transients of 20 Nm with a typical uncertainty of 1%. The preliminary system is extendable to cover adaptive control of dynamic drive performance and can be customized to specific speed and torque ranges.

Recent developments in the in‐situ measurement of sediment geoacoustic properties

The latest version of the in‐situ sediment acoustic measurement system (ISSAMS) allows direct, in‐situ measurement of sediment geoacoustic properties. Geoacoustic probes, which are mounted on a rigid frame, are inserted into the sediment hydraulically. The entire operation is controlled and monitored in real‐time from the surface. Data is collected and processed by a wet‐side computer and transmitted to the surface for waveform display and analysis. Video cameras both monitor insertion of probes and provide preliminary indication of sediment type. A seabird CTD is used to measure bottom water temperature, salinity, and sound speed. Sediment compressional wave velocity and attenuation are measured over pathlengths of 40 to 110 cm and at depths of between 0 to 50 cm below the sediment–water interface. Pulsed sine waves are transmitted at 58‐kHz and time delays and voltages are used to determine values of velocity and attenuation between identical radial‐poled ceramic cylinders (two transmit and two receive). Shear wave velocity and attenuation are measured using a similar pulse technique. Bimorph bender elements mounted in flexible silicone rubber mounts and driven at 100 to 2000 Hz to generate shear waves. Values of sediment geoacoustic properties from muddy sediments of Eckernförde Bay, Baltic Sea and carbonate sediments of the Florida Keys presented used to illustrate the operation and utility of the new system.

Vibration transmission through rolling element bearings, part II: System studies

This paper extends the proposed bearing stiffness formulation of Part I and demonstrates its superiority over existing models in vibration transmission analyses for a generic single shaft-bearing-plate-mount system. The bearing stiffness matrix [ K] bm is incorporated in discrete system models involving lumped parameter and finite element modeling techniques. Shaft, plate and mount flexibilities are also included in such models. The stability issue associated with the proposed bearing model is addressed analytically by using Liapunov's stability method, and the system is found to be dynamically stable provided the preloads are sufficiently high. Eigensolution and forced harmonic response to the following rolling element bearing system example cases are obtained by using our formulation and results are compared with the predictions yielded by the current vibration models: (i) rigid shaft and plate system freely suspended; (ii) rigid shaft and plate supported on flexible mounts; (iii) an experimental set-up consisting of a flexible shaft, two ball bearings, a rectangular plate and the supporting structure. Analytical results indicate that our proposed model is indeed capable of predicting plate rigid-body angular motion or plate flexural motion as excited by shaft motion. Such predictions are not observed in existing vibration models. Also, models with lower degrees of freedom, developed by several previous investigators, tend to underestimate the resonant frequencies and force or moment transmissibilities as compared with our multi-degree-of-freedom models. Finally, comparisons between our model and experiment have been found to be reasonably good.

Isolation of nuclear power plants from earthquake attack

The analysis of one-mass and two-mass models indicates that the earthquake-generated horizontal forces and deformations of the main structures of a nuclear power plant can be reduced by a factor of about ten times by mounting the overall power plant building on a recently developed base-isolation system. The very high forces which the ‘resonant appendage‘ effect may induce in some critical components (such as fuel elements, control rods and essential piping) may be reduced by a factor of 40 or more times by the isolation system. The parameters of the isolation system have been chosen as appropriate to the level of protection which should be provided for a nuclear plant in a seismically active area. Consideration is given to flexible mounts and dampers suitable for such an isolator.

Hexamine electro-optic light modulators

Although hexamine exhibits a low electro-optic coefficient, large strain-free crystals offer practical devices for both DC and high frequency modulation at reduced operating voltages. A modulator with a light aperture of f/10 has a half-wave voltage of 4.5 kV and shows an extinction ratio of 2000:1. In a multipass mode the voltage can be reduced to less than 100 V but with a consequent loss of angular aperture and light transmission. Precautions taken during modulator construction in order to preserve crystal isotropy included the selection of gold leaf as electrode material and flexible mounts to support the section.

High-pressure plastic lamination for flexible mounts of cover-slip preparations.

A Carver laminating press has been used for the lamination of small glass cover slip preparations of smears, aspiration biopsies, organ imprints and tissue culture materials between 41/2 × 57/8 × 0.012 inch thick Vinylite plastic sheets at 10,000 lb/inch2 of pressure and 400° F. The procedure described was to minimize some of the difficulties encountered in the cytological assessment of a variety of tissue and cell preparations. Lamination flattens the cells sufficiently to increase cytological detail and to reduce overlapping without sacrificing staining properties. Giemsa, Wright's methylene blue, orcein, and hematoxylin-eosin stains were used in the preparations. None of these stains were altered by the procedure. Laminated cell preparations are more suitable for making automatic and visual cell counts and for counting intracellular organoids