Vibration Of Mechanical Equipment Research Articles

Crack-Based Composite Flexible Sensor with Superhydrophobicity to Detect Strain and Vibration.

Vibration sensors are widely applied in the detection of faults and analysis of operational states in engineering machinery and equipment. However, commercial vibration sensors with a feature of high hardness hinder their usage in some practical applications where the measured objects have irregular surfaces that are difficult to install. Moreover, as the operating environments of machinery become increasingly complex, there is a growing demand for sensors capable of working in wet and humid conditions. Here, we present a flexible, superhydrophobic vibration sensor with parallel microcracks. The sensor is fabricated using a femtosecond laser direct writing ablation strategy to create the parallel cracks on a PDMS film, followed by spray-coating with a conductive ink composed of MWCNTs, CB, and PDMS. The results demonstrate that the developed flexible sensor exhibits a high-frequency response of up to 2000 Hz, a high acceleration response of up to 100 m/s2, a water contact angle as high as 159.61°, and a linearity of 0.9812 between the voltage signal and acceleration. The results indicate that the sensor can be employed for underwater vibration, sound recognition, and vibration monitoring in fields such as shield cutters, holding significant potential for mechanical equipment vibration monitoring and speech-based human-machine interaction.

Self-powered vibration sensor based on the coupling of dual-mode triboelectric nanogenerator and non-contact electromagnetic generator

Random vibration of mechanical equipment will lead to structural fatigue damage, while strong and sustained vibration will lead to the overall performance decline of the equipment. Vibration sensors can be used to monitor the stability of mechanical operation. However, in some complex unattended environments, it is still a significant challenge to realize real-time equipment monitoring and early warning. Therefore, we propose a self-powered multifunctional vibration sensor based on coupling a dual-mode triboelectric nanogenerator and a non-contact electromagnetic generator (M-HNG) for automatic condition monitoring. The dual-mode triboelectric nanogenerator and non-contact electromagnetic generator can work together to realize real-time self-powered vibration monitoring. We established the prototype model of the vibration sensor, simulated the working principle of each part of the sensor, and fitted the functional relationship between the vibration amplitude and speed of the sensor and the output electrical signal. The results show that the short-circuit current of the sensor is very sensitive to the change in external vibration speed and has good stability in its detection range. Using a non-contact electromagnetic generator can effectively improve the service life of the vibration sensor. The system can continuously monitor the vibration signals generated by machinery during operation and provide an effective way for structural health monitoring, especially in extreme environments or unattended conditions.

In situ automatic monitoring and working state assessment of inclined shafts in coal mines

The application of fabricated segmental lining in deeply buried inclined shafts in complex strata has been significantly increased in recent years. However, the structural safety of the fabricated lining is vulnerable to high ground stress and high water pressure, as well as the vibration of mechanical equipment and ground disturbance caused by coal mining. Thus, applying an automatic load-monitoring system to the inclined shaft in coal mines has great engineering importance in evaluating structural safety. In this study, an automatic monitoring and data transmission system for the inclined shaft was developed. In addition, by considering the non-linear characteristics of segment joints and different working states of concrete segments, a more functional assessment method was proposed based on the limit state assessment theory. According to the in situ monitoring project in the number 2 inclined shaft of Bulianta coal mine in China, the calculated internal forces are in good agreement with the monitored data, and the proposed assessment method shows reliable results during the operation period.

Self-Powered Acceleration Sensor Based on Liquid Metal Triboelectric Nanogenerator for Vibration Monitoring.

An acceleration sensor is an essential component of the vibration measurement, while the passivity and sensitivity are the pivotal features for its application. Here, we report a self-powered and highly sensitive acceleration sensor based on a triboelectric nanogenerator composed of a liquid metal mercury droplet (LMMD) and nanofiber-networked polyvinylidene fluoride (nn-PVDF) film. Due to the ultrahigh surface-to-volume ratio of nn-PVDF film and high surface tension, high mass density, high elastic as well as mechanical robustness of LMMD, the open-circuit voltage and short-circuit current reach up to 15.5 V and 300 nA at the acceleration of 60 m/s2, respectively. The acceleration sensor has a wide detection range from 0 to 60 m/s2 with a high sensitivity of 0.26 V·s/m2. Also, the output voltage and current show a negligible decrease over 200,000 cycles, evidently presenting excellent stability. Moreover, a high-speed camera was employed to dynamically capture the motion state of the acceleration sensor for insight into the corresponding work mechanism. Finally, the acceleration sensor was demonstrated to measure the vibration of mechanical equipment and human motion in real time, which has potential applications in equipment vibration monitoring and troubleshooting.

The use of polyvinylidene fluoride (PVDF) films as sensors for vibration measurement: A brief review

ABSTRACTInformation about vibrating objects can be obtained by vibration measurements. Piezoelectric sensors made by piezoelectric ceramics, quartz, or organic piezoelectric materials, e. g. polyvinylidene fluoride (PVDF) have been adopted by many researchers to measure vibrations. Among these piezoelectric materials, PVDF has attracted much attention for its excellent properties such as outstanding chemical resistance, high thermal stability, low permitivities, low acoustic impedances, flexibility and membrane forming properties. In this paper, PVDF is introduced in brief. In addition, this paper briefly reviews the use of PVDF films as sensors for vibration measurement in the areas of portable medical detections, structural health monitoring, mechanical equipment vibration measurements and other applications. Meanwhile, some cases which have good low-frequency performances or novel features in structures will be especially introduced to provide helpful experiences for future applications. In the end, a spiral-shaped PVDF cantilever and a double-clamped PVDF beam of two piezoelectric energy harvesters are mentioned to provide ideas for reducing the resonant frequencies and enhancing the output signals of PVDF vibration sensors respectively. The idea of how to enhance the output signals of PVDF sensors for low frequency vibration measurements may be helpful to the development of geophone.

The Development of an Intelligent Hybrid Active-passive Vibration Isolator

A hybrid active-passive vibration isolator made up of electromagnetic actuator and air spring in parallel can be used to effectively isolate the broadband and line spectrum vibration of mechanical equipment simultaneously. However, due to its reliability and safety problems caused by the impact, its application in ships is limited. In this paper, an impact- resistant structure and an air gap self-sensing method of the passive-active hybrid vibration isolator are proposed and developed on the base of modelling, simulation and analysis. A thin magnetic rubber is filled into the air gap of electromagnetic actuator, which can avoid rigid collision between the armature and the permanent magnet under the action of impact. A suspension armature structure including pre-compression spring is suggested, which can automatically compensate the deformation caused by impact and protect the coil and permanent magnet from impact damage. An air gap self-sensing method is developed through detecting the voltage between the input and output terminals of actuator, which is verified by experiments.

A method for determining the force spectrum produced by mechanical equipment.

Currently there is no standardized method for determining the force spectrum produced by a piece of mechanical equipment. This information is useful for conducting detailed vibration analysis in buildings, specifying proper vibration isolation for mechanical equipment, and comparing mechanical equipment vibration performance. This paper presents a method for estimating the force spectrum for a piece of mechanical equipment supported on spring isolators. The force spectrum is calculated from the measured vibration response of the sprung mass and the frequency response function of the system. For validation, this procedure was used to determine the force spectrum of a 21 500 CFM air handling unit externally mounted on nominally 1-in. static deflection spring isolators. The calculated force spectrum was then used as a force input to a finite element model of a mass-spring-damper system with the same properties as the sprung air handler. The predicted results compare favorably with the measured vibration response and tend to support that this is a viable method for characterizing the force produced by mechanical equipment.

Mechanical equipment and ambulances. Strange bedfellows of cardiovascular services.

A case study will be presented regarding vibration and noise control design for an existing heart hospital. Facility expansion within a crowded site necessitates sandwiching a suite of new cardiac catheterization laboratories between mechanical equipment rooms above and the hospital’s main ambulance driveway below. The facility expansion also includes cardiac computed tomography, magnetic resonance imaging, and nuclear imaging, plus cardiovascular care, treatment, and administrative support spaces. Procedure and support spaces can be disturbed by mechanical equipment noise and vibration and noise from ambulance siren. Cardiac procedure instruments and imaging can be disturbed by low frequency noise and vibration from building mechanical systems, ambulance traffic, and building occupants. Design criteria for permissible building vibration and continuous background noise will be presented along with relevant sources and bases. Measurement evaluation results for design will be contrasted with criteria. Measures incorporated in design to mitigate vibration and noise on catheterization laboratories will be discussed. Measures considered in design include structural floor “detuning” concepts, stiffened supports for catheterization laboratory C‐arms, mechanical equipment vibration isolation mounts, and floating concrete floor systems for mechanical rooms. If available, postconstruction spectral analysis measurements of building noise and vibration will be presented.

Method for synchronous digital analysis of equipment vibration signals

A description is given of a method for synchronous digital analysis of nonsteady signals corresponding to the vibration of mechanical equipment under transient conditions;the metrological characteristics of the method are also analyzed.