scholarly journals Rancang Bangun Vibration Test Bench untuk Mensimulasikan Kondisi Unbalance dengan Pengaturan Putaran dan Beban Unbalance

2017 ◽  
Vol 3 (1) ◽  
Author(s):  
Imam Maolana
Keyword(s):  
Electric Motor ◽  
Test Bench ◽  
Load Condition ◽  
Axial Direction ◽  
High Amplitude ◽  
Vibration Measurement ◽  
Wave Form ◽  
Vibration Test ◽  
Vibration Testing ◽  
Rotating Machine

The goal of this work is to design and build a vibration test bench to simulate unbalance in rotating machine. The vibration test bench made of a 25 mm diameter steel shaft and length of 410 mm supported by two ball bearings. Two steel discs to variate unbalance load installed in the shaft powered by 0.5 Hp electric motor with maximum rotation of 1400 RPM. Inverter used to control rotation from electric motor. Vibration testing conducted at two condition; (1) without load and rotation variation, (2) unbalance load with variation of unbalance mass. Pick up point of vibration measurement at bearing house in radial and axial direction. The vibration parameter measured are amplitude and spectrum (wave form). Amplitude measurement using hand held vibrometer, while spectrum using accelerometer conected to a Data Acquisition. After testing the condition using unbalance load, we conclude that the vibration test bench match unbalance condition as described in theory which is high amplitude at machine frequency, and it’s value proportional to unbalance mass. We find that the highest amplitude is at horizontal direction where machine stiffnes is smallest. Vibration testing with no load condition show that there is harmonic in vibration spectrum indicating rotating looseness, probably caused by bearing wear. 

Vibration Measurement and Monitoring of a Rotating Disk Using Contactless Laser Excitation

2013 ◽  
Author(s):  
Itsuro Kajiwara ◽  
Naoki Hosoya
Keyword(s):  
Laser Doppler Vibrometer ◽  
Rotating Disk ◽  
Disk Drive ◽  
Vibration Characteristics ◽  
Vibration Measurement ◽  
Testing System ◽  
Rotating Disks ◽  
Vibration Testing ◽  
Structural Surface ◽  
Theoretical Analyses

This paper proposes a contactless vibration testing system for rotating disks based on an impulse response excited by a laser ablation. High power YAG pulse laser is used in this system for producing an ideal impulse force on structural surface without contact. The contactless vibration testing system is composed of a YAG laser, laser Doppler vibrometer and spectrum analyzer. This system makes it possible to measure vibration characteristics of structures under operation, such as vibration measurement of a rotating disk. The effectiveness of this system is confirmed by experimental and theoretical analyses. In this paper, a platter of hard disk drive is employed as an experimental object. Vibration characteristics of a rotating and non-rotating platter are measured and compared with the results of theoretical analysis.

Gastroduodenal Motility in Neonates: Response to Human Milk Compared With Cow's Milk Formula

PEDIATRICS ◽  
1987 ◽  
Vol 80 (3) ◽  
pp. 434-438
Author(s):  
T. Tomomasa ◽  
P. E. Hyman ◽  
K. Itoh ◽  
J. Y. Hsu ◽  
T. Koizumi ◽  
...  
Keyword(s):  
Breast Milk ◽  
Human Milk ◽  
Infant Formula ◽  
High Amplitude ◽  
Cow’S Milk ◽  
Milk Formula ◽  
Wave Form ◽  
Fasting State ◽  
Cow's Milk ◽  
Gastroduodenal Motility

It is known that breast milk empties more quickly from the stomach than does infant formula. We studied the difference in gastroduodenal motility between neonates fed with human milk and those fed with infant formula. Twenty-four five-to 36-day-old neonates were fed with mother's breast milk or with a cow's milk-based formula. Postprandlial gastroduodenal contractions were recorded manometrically for three hours. Repetitive, high-amplitude nonmigrating contractions were the dominant wave form during the postprandial period. The number of episodes, duration, amplitude, and frequency of nonmigrating contractions were not different following the different feedings. The migrating myoelectric complex, which signals a return to the interdigestive (fasting) state, appeared in 75% of breast milk-fed infants but only 17% of formula-fed infants (P < .05) within the three-hour recording period. Because contractions were similar following the two meals, but a fasting state recurred more rapidly in breast-fed infants, we conclude that factors other than phasic, nonpropagated antroduodenal contractions were responsible for the differences in gastric emptying between breast milk and formula.

Experimental Research on Vibration Characteristics of Laminated Composite Cantilever Beam

2021 ◽  
Author(s):  
Rui Yang ◽  
Xiaobin Li ◽  
Hongxi Li
Keyword(s):  
Cantilever Beam ◽  
Optical Measurement ◽  
Laminated Composite ◽  
Experimental Methods ◽  
Test Methods ◽  
Vibration Characteristics ◽  
Test Method ◽  
Vibration Measurement ◽  
Vibration Test ◽  
Test Results

Abstract In this paper, the vibration characteristics of laminated composite cantilever beam is taken as the research object. Firstly, a vibration formula specific for laminated composite cantilever beam is derived, from which the low order natural frequency of laminated composite cantilever beam is calculated; Secondly, two experimental methods, electrical and optical measurement, are used to study the vibration characteristics of laminated composite cantilever beam, and the influence of different test methods, sensor types, number of measuring points and excitation methods on the test results are analyzed. Through the combination of theory and experiment, a test method that can be applied to the vibration test of composite material laminated structure cantilever beam is obtained. Based on the laser vibration measurement method in the optical method, the results show that the deviation between the experimental data and the theoretical solution is the smallest when the distance between the probe and the specimen is 0.5m and the sampling time is 5s by using the optical fiber vibrometer. The research content of this article can provide a reasonable reference for related vibration test research.

scholarly journals A Multi-Sensor Approach to the Interpretation of Radar Altimeter Wave Forms from Two Arctic Ice Caps

1987 ◽  
Vol 9 ◽  
pp. 60-68 ◽  
Author(s):  
Mark R. Drinkwater ◽  
Julian A. Dowdeswell
Keyword(s):  
Surface Roughness ◽  
Leading Edge ◽  
High Amplitude ◽  
Wave Form ◽  
Radar Altimeter ◽  
Ice Caps ◽  
Lower Amplitude ◽  
Wet Snow ◽  
Radio Echo Sounding ◽  
Wave Forms

Data collected over Svalbard on 28 June 1984 by a 13.81 GHz airborne radar altimeter enabled analysis of signals returned from two relatively large ice masses. Wave forms received over the ice caps of Austfonna and Vestfonna are analysed with the aid of existing aerial photography, radio echo-sounding data, and Landsat MSS images acquired close to the date of the altimeter flight. Results indicate that altimeter wave forms are controlled mainly by surface roughness and scattering characteristics. Wet snow surfaces have narrow 3 dB back-scatter half-angles and cause high-amplitude signals, in contrast to relatively dry snow surfaces with lower-amplitude diffuse signals. Metre-scale surface roughness primarily affects wave-form amplitude and leading-edge slope, this becoming apparent over ice streams on Vestfonna.

Diagnosis of rotating machine unbalance using machine learning algorithms on vibration orbital features

2020 ◽  
pp. 107754632092983
Author(s):  
Leonardo S Jablon ◽  
Sergio L Avila ◽  
Bruno Borba ◽  
Gustavo L Mourão ◽  
Fabrizio L Freitas ◽  
...  
Keyword(s):  
Machine Learning ◽  
Learning Strategies ◽  
Machine Learning Algorithms ◽  
Vibration Measurement ◽  
Machine Learning Techniques ◽  
Rolling Element Bearings ◽  
Rotating Machines ◽  
Signal To Noise ◽  
Rotating Machine ◽  
Rolling Element

The diagnosis of failures in rotating machines has been subject to studies because of its benefits to maintenance improvement. Condition monitoring reduces maintenance costs, increases reliability and availability, and extends the useful life of critical rotating machinery in industry ambiance. Machine learning techniques have been evolving rapidly, and its applications are bringing better performance to many fields. This study presents a new strategy to improve the diagnosis performance of rotating machines using machine learning strategies on vibration orbital features. The advantage of using orbits in comparison to other vibration measurement systems is the simplicity of the instrumentation involved as well as the information multiplicity contained in the orbit. On the other hand, rolling element bearings are prevalent in industrial machinery. This type of bearing has less orbital oscillation and is noisier than sliding contact bearings. Therefore, it is more difficult to extract useful information. Practical results on an industry motor workbench with rolling element bearings are presented, and the algorithm robustness is evaluated by calculating diagnosis accuracy using inputs with different signal-to-noise ratios. For this kind of noisy scenario where signal analysis is naturally tough, the algorithm classifies approximately 85% of the time correctly. In a completely harsh environment, where the signal-to-noise ratio can be smaller than −25 dB, the accuracy achieved is close to 60%. These statistics show that the strategy proposed can be robust for rotating machine unbalance condition diagnosis even in the worst scenarios, which is required for industrial applications.

Quadratic Mode Shape Components From Ground Vibration Testing

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
L. H. van Zyl ◽  
E. H. Mathews
Keyword(s):  
Mode Shape ◽  
Ground Vibration ◽  
Axial Displacement ◽  
Vibration Test ◽  
Transverse Displacement ◽  
Vibration Testing ◽  
Linear Mode ◽  
Quadratic Mode ◽  
Acceleration Signals ◽  
Shape Component

Points on a vibrating structure generally move along curved paths rather than straight lines. For example, the tip of a cantilever beam vibrating in a bending mode experiences axial displacement as well as transverse displacement. The axial displacement is governed by the inextensibility of the neutral axis of the beam and is proportional to the square of the transverse displacement; hence the name “quadratic mode shape component.” Quadratic mode shape components are largely ignored in modal analysis, but there are some applications in the field of modal-basis structural analysis where the curved path of motion cannot be ignored. Examples include vibrations of rotating structures and buckling. Methods employing finite element analysis have been developed to calculate quadratic mode shape components. Ground vibration testing typically only yields the linear mode shape components. This paper explores the possibility of measuring the quadratic mode shape components in a sine-dwell ground vibration test. This is purely an additional measurement and does not affect the measured linear mode shape components or the modal parameters, i.e., modal mass, frequency, and damping ratio. The accelerometer output was modeled in detail taking into account its linear acceleration, its rotation, and gravitational acceleration. The response was correlated with the Fourier series representation of the output signal. The result was a simple expression for the quadratic mode shape component. The method was tested on a simple test piece and satisfactory results were obtained. The method requires that the accelerometers measure down to steady state and that up to the second Fourier coefficients of the output signals are calculated. The proposed method for measuring quadratic mode shape components in a sine-dwell ground vibration test seems feasible. One drawback of the method is that it is based on the measurement and processing of second harmonics in the acceleration signals and is therefore sensitive to any form of structural nonlinearity that may also cause higher harmonics in the acceleration signals. Another drawback is that only the quadratic components of individual modes can be measured, whereas coupled quadratic terms are generally also required to fully describe the motion of a point on a vibrating structure.

scholarly journals Early Fault Detection by Vibration Measurement

2021 ◽  
Vol 10 (5) ◽  
pp. 358-365
Author(s):  
D. H. Omar ◽  
M. H. Belal ◽  
F. R. Gomaa
Keyword(s):  
Fault Detection ◽  
Experimental Studies ◽  
Vibration Monitoring ◽  
Vibration Measurement ◽  
Maintenance Cost ◽  
Rotating Machine ◽  
Analysis Technique ◽  
Measurement Devices ◽  
Early Fault Detection ◽  
Monitoring Devices

Early fault detection by using vibration monitoring devices could help industries to avoid sudden stoppage of the machine, thus reduces machine downtime and maintenance cost to save time and money. Early fault detection by using vibration measurement devices are very useful for determining the condition of rotating elements and its analysis. In this paper, experimental studies were performed to predict misalignment faults in rotating machine which is connected with simple rigid coupling. The vibration is collected by using Micro log data collector. From results, we can easily predict misalignment in rotating machine using spectrum analysis technique.

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