Mounting Arrangement Research Articles

Rocking stiffness of electrical cabinets with tubular base in nuclear power plants

Safe operation of nuclear power plants during an earthquake requires continued operation of safety related electrical equipment as intended. Such equipment are mounted in electrical cabinets and are seismically qualified by using an in-cabinet response spectra (ICRS). Generation of ICRS requires a good understanding of the cabinet’s dynamic characteristics. Past studies have shown that the rotational stiffness associated with the cabinet base and the mounting arrangement plays a primary role in the dynamic behavior of the cabinet. This rotational stiffness is needed to evaluate and characterize the global rocking mode of cabinet vibration. Existing studies have developed formulations to calculate the rocking stiffness for a few mounting arrangements that are typically found in United States and some other western countries. However, existing formulations could not be applied to cabinets in South Korean nuclear plants due to the differences in cabinet mounting type. This study is focused on consideration of tubular mounting arrangement that is typically found in South Korean plants. First, closed-form formulations are developed using fundamental principles of mechanics for two separate cases of this mounting arrangement. Then, detailed nonlinear finite element (FE) analyses are conducted for different mounting arrangements corresponding to different properties and dimensions of the tubular base. The FE models are used to calibrate the proposed closed-form formulations for various different configurations and structural or geometrical properties of tubular members. The proposed formulations provide a simple and accurate estimation of cabinet rocking stiffness which otherwise is difficult to evaluate without a shake table test or a detailed finite element analysis.

Sharing 5G Antenna with Transmission Tower: Mounting Height, Arrangement, Electromagnetic Interference and Overall Safety

The demand for communication base stations in the 5G era has increased dramatically, the current large-scale transmission towers are important carrier for 5G equipment sharing construction. For the transmission system, the current and previous load code for the design of overhead transmission line in China are investigated. Different wind load specification on the conductors, ground wires and 5G equipment on the transmission towers are studied in finite element coupling model. In addition, the influence of soil and electromagnetic is also considering in calculation model. According to mechanical and simulation model, the structural response of the transmission tower with sharing 5G antenna including different mounting height and arrangement is discussed. Finally, comparison on maximum stress ratio of different horizontal span and overall safety of shared tower is evaluated.

Analysis and Optimisation of Ride Vibration of a Heavy-Duty Truck Based on a Vertical-Pitch-Roll Driver-Vehicle Coupled Dynamic Model

The ride comfort and the cargo safety are of great importance in the vibration design of heavy-duty vehicle. Traditional ride comfort design method based on the response of components of vehicles or interaction between human and seat overlooks the most direct criterion, the response of occupants, which makes the optimisation not targeted enough. It will be better to conduct the ride comfort design with the biodynamic response of driver. To this end, a 17-degrees-of-freedom (DOFs) vertical-pitch-roll vehicle dynamic model of a three-axle heavy-duty truck coupled with a 7 DOFs human model is developed. The ride comfort of human body under the vertical, the pitch, and the roll vibrations can be evaluated with the weighted root-mean-square (r.m.s.) acceleration of the driver in multiple directions. The flexibilities of chassis and carriage are also considered to improve the accuracy of the prediction of the ride comfort and to constrain the mounting optimisation of cab and carriage. After validation, the sensitivity analysis of the mounting system, the suspensions, and arrangement of sprung masses is carried out and significant factors to ride vibration are identified. The optimal combination of design parameters is obtained with the objective of minimizing the vibration of the driver and carriage simultaneously. The optimisation result shows that the weighted driver vibration is reduced by 27.9% and the carriage vibration is reduced by 31.8% at various speeds.

Stress Simulation Study on a Novel Combination String of Transmission Line Insulators

The insulator string mainly plays a role of fixing wire and preventing the current from returning to the ground in the power transmission and transformation project. In order to compress the corridor width of the transmission line and make it convenient for breaking line, we proposed a novel structure in which the V-type fittings and the tensile insulator string are optimally combined. In this paper, the mathematical model of mechanical analysis for the structure is established. According to the equilibrium conditions of space force system, the factors affecting the stress of the structure are analysed. In addition, a simulation model is built in the finite element analysis software. The stress distributions of the new structure by setting two installation angles are calculated and the special parts with weak mechanical properties in the new structure are explored based on the generated stress cloud diagram. We compare the maximum value of the von Mises equivalent stress in the two arrangements. A conclusion of better than 45° at a mounting arrangement angle of 50° was obtained. The research results provide a theoretical reference for further optimization design and installation of the combined structure in the future.

Reduction in edge effects for small panels characterized by a parametric array source.

This study sought to explore effects of panel size on underwater acoustic transmission and reflection measurements made with a truncated parametric array source. The transmission loss (TL) and reflection loss spectra of aluminum panels of several different sizes were determined experimentally, and compared to predictions from plane wave theory in the 5-100 kHz frequency range. For the smallest panel size, there were significant discrepancies between experimental data and plane wave theory, which were attributed to contributions from edge-diffracted waves and interferences from the mounting fixture for the panel. For reflection measurements, the latter interference could be corrected for in part by measurement of the reflected signal from the sample holder (with no panel present), and subtracting this signal from reference and test panel waveforms. In order to reduce the contributions from edge diffracted waves in TL measurements, an alternative panel mounting system was investigated, which involved surrounding the panel in a reflective baffle. There was a significant improvement in agreement of experimental TL spectra with plane wave theory for the smallest aluminum panel when the baffle mounting arrangement was used.

An optimized thermal network model to estimate thermal performances on a pair of angular contact ball bearings under oil-air lubrication

To estimate thermal performances of angular contact ball bearings is essential for operating precision and service life of angular contact ball bearings. However, a simple and accurate model estimating the bearing temperature is needed but absent so far. Considering the centrifugal force, gyroscopic moment and thermal expansion, ball loads equilibrium model was first established to analyze the bearing loads. The radial and axial heat transfer, especially the effect of structural constraints on bearings temperature was well characterized as well as the bearing mounting arrangement, and then an enhanced node planning scheme was proposed. With their surroundings considered, an optimized thermal grid model for a pair of front bearings mounted in the high-speed spindle was developed by using this scheme. Next Newton-Raphson method was employed to obtain the numerical solution by Matlab. The bearing temperature variation, moreover, was tested to validate the developed model. The results indicate that both series of results agree well. Compared with the presented models, the deviation between the calculation results and the test values is reduced to less than 9%. As a result, the bearing temperature rise can be better forecasted, which may be beneficialto improve bearing operating accuracy as well as bearing service life.

The Influence of Internal Resonances From Machinery Mounts on Radiated Noise From Ships

Machinery vibration is a significant source of noise from marine vessels. Consequently, problematic machinery is often decoupled from the hull using resilient mounts. When radiated noise is a priority, two-stage mounting arrangements can be used which provide superior performance. This improvement, however, comes at a much higher weight and cost. A commonly overlooked issue with isolation systems is that the individual mounts suffer from internal resonances which reduce their effectiveness. This paper broadly evaluates the influence of these on the underwater noise levels from a typical ship diesel. The effect of nonrigid structural components, that is, the supported machine, the machine foundation, and the intermediate mass in two-stage mounting arrangements, is also discussed. The structureborne and airborne transmission paths are resolved individually using approximate analytical methods, and the source levels are estimated from empirical relationships for typical marine diesels. It is shown that, by mitigating the internal resonances of the mounts, a two-stage mounting arrangement may be unnecessary because of the contribution to the underwater noise by airborne transmission.

Focus on materials, semiconductors, vacuum, and cryogenics

Focus on materials, semiconductors, vacuum, and cryogenics

A31 コントロールモーメントジャイロ搭載人工衛星の耐故障姿勢制御系(M-OS13-7 飛翔体の制御,M-OS13 宇宙機・宇宙ロボットのダイナミクスと制御,「海を越え,国を越え,世代を超えて!」)

In recent years, it has been required accurate and agile attitude control of satellites. For this purpose, the necessity of Control Moment Gyros (CMGs) has been increasing, which can generate much higher torque than reaction wheels which are used as conventional spacecraft actuators. Furthermore, it is important for the attitude control systems to have function of fault tolerant. In a conventional 4 CMG system, the CMGs are placed in a pyramid mounting arrangement with skew angle set to 54.74 degrees. The maximum angular momentum of the CMG system is changed according to the skew angle. The suitable skew angle should be designed considering normal and failure situations. Moreover, the suitable parameters of the satellite attitude and CMG control system are changed according to the skew angle. Therefore, this paper proposes a design method of the fault-tolerant attitude control system. In the proposed method, the skew angle and the parameters of the control system are tuned simultaneously by genetic algorithm. To verify the fault-tolerant of the proposed method, numerical simulations in case that the one CMG is failed are carried out.

A Headset-Mounted Mini Sampler for Measuring Exposure to Welding Aerosol in the Breathing Zone

There is a need for a small personal aerosol sampler for measuring occupational exposure to airborne particles in the breathing zone. Existing aerosol samplers are too large to be mounted inside modern welder's protective equipment without disturbing the worker. A headset-mounted mini sampler has been developed to fill this gap with focus on manganese exposure. This mini sampler is easy to use and can be mounted inside modern, slimline welder's face shield. The mini sampler is based on a commercially available 13-mm filter holder that has been modified to incorporate an inlet nozzle made of aluminium. The nominal flow rate of the mini sampler is 0.75 l min(-1). The mini sampler is to be worn mounted on a headset, modified from professional microphone headsets. Several aspects related to using the mini sampler have been tested by personal and static sampling at five workplaces and in the laboratory. Four headset models were tested for their suitability as a sampler holder, of which three models were accepted by the welders. The sampling bias of the mini sampler versus the IOM sampler and the open-face 25-mm filter holder, respectively, depends on the size distribution of the sampled aerosol. At the lowest encountered mass concentration ratio of the open-face 25-mm filter holder to the IOM sampler (0.65), the sampling bias of the mini sampler versus the IOM sampler is approximately -26% and versus the open-face 25-mm filter holder is approximately +12%. For manganese, the negative root mean square (RMS) sampling bias of the mini sampler versus the IOM sampler is -0.046 and versus the open-face 25-mm filter holder is non-significant. Both these biases are statistically non-significant. The mini sampler can therefore be employed for determining welders' occupational exposure to manganese. The pressure drop across the filter can become excessive due to the small filtration area. Compared to the Casella Apex pump, the SKC AirChek2000 pump was generally found to be able to keep its flow rate constant within +/-5% at higher concentrations and for longer sampling times. Our results indicate that the inhalable fraction of the welding aerosol mass at the visited plants only consisted of 25-55% welding fume particles (agglomerates of coagulated particles generated by nucleation/condensation). The rest of the mass is made up of particles from spattering and grinding. More than 65% of manganese is generally found in the fume particles. The weighing precision of 13-mm filters is 2.2 microg. The RMS sample loss due to transport when loaded samples are shipped by mail in padded envelopes is 6 microg. Both figures are very low in comparison to the mass expected to be collected by personal sampling, generally exceeding 200 microg. The headset-mounted mini sampler is user-friendly, easy to adjust individually, does not disturb the welder during sampling and allows sampling inside personal protective equipment. The headset mounting arrangement improves personal sampling as it maintains the sampler close to the nose/mouth during the whole sampling period. This study shows that the developed headset-mounted mini sampler is suitable for assessing exposure to manganese in welding aerosol.

A mini-sampler for welding aerosol mounted in close vicinity of the mouth/nose

A small personal aerosol mini-sampler to be used inside modern welding visors has been developed. The main object of the mini-sampler has been to sample manganese. The sampler is based on commercially available 13 mm filter holders but modified to incorporate an inlet nozzle made of aluminium. The nominal flow rate of the mini-sampler is 0,75 l/min. The sampler is to be worn mounted on a headset, modified from professional microphone headsets. The headset mounting arrangement was accepted by the welders. The sampling bias of the mini sampler versus the IOM sampler depends on the coarseness of the sampled aerosol. At the lowest concentration ratio of the open-face 25 mm filter holder to the IOM sampler equal to 0,65, the bias of the mini sampler is approximately -26% versus the IOM. The RMS sampling bias of the mini sampler versus the IOM sampler for manganese is -4,6%. The inhalable fraction of welding aerosol mass consists only of 25-55% of welding fume. The rest of the mass is made up of spatter particles and grinding particles. For manganese generally more than 65% is found in the fume.

Cooling fan mounting arrangement with vibration isolation member

A mounting arrangement for mounting a cooling fan to a support member (30) includes a fan frame (10) having a mounting flange (14) for confronting with the support member, and a plurality of vibration isolation members (20) attached to the mounting flange. When the fan frame is secured to the support member, the vibration isolation members are pressingly sandwiched between the mounting flange and the support member

Wet and dry installation of submersible pumps

The installation of submersible pumps can be either ‘wet’ or ‘dry’, and the question often arises as to which mounting arrangement is preferable in different circumstances, as Sergey Berezin, general manager of JSC LEP in Moscow, explains. He also considers what should be taken into account when designing pump stations using submersibles, particularly where dry installation is involved.

A study of brake noise and the influence of the centre of pressure at the disc/pad interface, the coefficient of friction and calliper mounting geometry

It is generally accepted that the coefficient of friction between the friction pair, the pad and the rotor plays a significant role in the propensity of a brake to generate noise. Because of the ease with which changes may be made to the pad compound material it is this that is more often the subject of change when there is a problematic noisy brake with both the rotor and the calliper tending to remain ‘isolated’ from examination. This paper investigates the propensity of a brake to generate noise over a range of temperatures and pressures under conditions that allow a mechanically induced offset centre of pressure between the pad and rotor to be varied. It is shown that for a high-volume production car brake there is an increased tendency for it to generate noise when a very specific leading offset centre of pressure is engineered. With this condition it is shown that a situation is promoted whereby the brake becomes mechanically unstable, with system changes such as brake pressure and temperature variations having little influence on the brake to alter its tendency to generate noise. Furthermore, it is shown that the critical offset centre of pressure may be related to the coefficient of friction between the friction pair and the mounting geometry of the calliper. Confirmation of the findings are supported by a repeat investigation of the vehicle's alternative brake calliper. It is suggested that the source of a noisy brake may lie as much in basic mechanical design as inappropriate material choice. Further confirmation is demonstrated through the study of a commercial sliding fist-type brake, where the brake is significantly noisier when the centre of pressure and calliper mounting arrangement provide an appropriate spragging angle related to the friction coefficient.

Active control of machine tool vibrations in external turning operations

Vibration and noise in metal cutting are ubiquitous problems in the workshop. The external turning operation is one kind of metal cutting that exhibits vibration-related problems. Severe noise is also a problem growing in proportion due to regulations in preventing hearing loss. Active vibration control is a potential solution to such problems. With the piezoceramic actuator technology of today, the size of the actuator can be kept small and still be able to produce a sufficient amount of force for the antivibrations. Results from several continuous cutting experiments show a 40 dB reduction of the cutting tool vibration level. The design of the active technique enables this technology to be applicable to a general lathe, provided the mounting arrangement is fairly similar.

Acoustic analysis of bone using point-source-like transducers

An improved apparatus and method for providing a measurement of the characteristic behavior of an acoustic wave in a bone of a subject. A preferred embodiment has first and second transducers and a mounting arrangement for mounting the transducers in spaced relationship with respect to the bone. The first transducer may transmit acoustic energy over a broad solid angle, thereby behaving as a point source of acoustic energy. Additionally or alternatively, the second transducer may collect acoustic energy over a broad solid angle, thereby behaving as a point receiver. A signal processor in communication with the second transducer provides a measurement that is a function of at least one of transient spectral or transient temporal components of the signal received by the second transducer.

Installation effects on fan acoustic and aerodynamic performance

Sound power measurements were performed on an upright vacuum cleaner in order to identify predominant noise generating mechanisms and to recommend corrective noise control modifications that would cause no increase in production costs. These modifications were then implemented and their effectiveness quantified. In general, the noise radiated by the vacuum cleaner is dominated by aerodynamic sources. Aerodynamic interactions occur between the electric motor cooling fan and nearby motor mounting fixtures resulting in intense tones at blade rate and harmonic frequencies. These tones are reduced by as much as 25 dB in level, to the broadband sound power level of the unit, by eliminating certain flow obstructions, and mounting the motor in an alternative fashion. Motor cooling performance is also dramatically improved by the new mounting arrangement resulting in a 26 °C reduction in steady-state operating temperature. © 1999 Institute of Noise Control Engineering. †S0736-2501„99...00101-0‡

Noise cancelling microphone and boot mounting arrangement

An apparatus for mounting a noise cancelling microphone (34) within a communication device comprises a housing having a front portion (36), a back portion and side portions (40). The front portion (36) and one of the side portions (40) have apertures (38 and 40). Within the housing lies a receptacle (32 or 50 or 100) for retaining a microphone or transducer (34). The receptacle is arranged and constructed to form a chamber (32) between the apertures (38 and 40) in the front portion (36) and the side portion (40) of the housing.

A space simulation chamber for space power insulation

An account is given of an experimental facility which has been designed specifically for the study of electrical insulation in a simulated space environment. Insulation in space can experience a very wide range of environmental stimuli and it is very difficult if not impossible to stimulate them all. Those that are considered in the present work are vacuum, temperature, nuclear radiation and atomic oxygen. The facility consists of a stainless steel high-vacuum chamber with a sample mounting arrangement which allows sample temperatures to be varied between 80 and 470 K. Test specimens can also be exposed to electromagnetic radiation within the chamber. Atomic oxygen treatment of materials takes place before they are introduced to the chamber. The materials being considered are Kapton and an epoxy resin formulation. Various electrical measurements are being undertaken and comprise primarily dielectric loss by frequency domain spectroscopy and pre-breakdown current pulse activity under direct stress, while the provision exists for conductivity and breakdown measurements as well. These are made in real time under vacuum, temperature and low dose rate electromagnetic radiation following an ageing procedure which involves combinations of these three foregoing environmental stimuli and atomic oxygen.

Acoustic calibrator for plethysmographic surface pressure sensors

Plethysmographic surface pressure sensors measure heart sounds, breathing sounds, blood pressure, blood flow sounds, fetal movement, and other sounds indicative of physiological conditions. An acoustic calibrator for such sensors should provide a specific acoustic impedance and permit a mounting arrangement resembling in-service conditions. The calibrator described here consists of a water-filled balloon, on which the test sensor is mounted at the equator. A hydrophone positioned in the center of the balloon serves as a nearly isotropic source at low frequencies. Since the excited sound field is not free but reverberant, a free-field calibration of the hydrophone as projector cannot be used. Rather, a rigidly supported reference sensor of known calibration is tightly coupled to the balloon surface to calibrate the amplitude of the local surface pressure (which is sensitive to mounting conditions) as a function of frequency. The calibration of an acoustically based fetal heart tone monitor will be presented as an example.