Dynamics of an impact print hammer.

An acoustic-excitation optical coherence vibrometer (AE-OCV) is proposed for noncontact microstructure vibration measurement and modal analysis. The vibration dynamic parameters of the microstructure can be captured with a subnanometer displacement resolution by the proposed AE-OCV using spectral wavelength calibration algorithm and spectral center correction method. The natural frequency of the microstructure could also be obtained by the developed noncontact AE-OCV system using the swept-frequency acoustic excitation method. Furthermore, a home-made spectrometer based on a high-speed linear camera could provide the system with a frequency measurement range of 0–50 kHz. The developed AE-OCV has an excellent performance in microstructures vibration measurement and modal analysis, especially for high-frequency and nanoscale vibration measurements. It is of great significance to the design of the microelectromechanical system (MEMS), such as the noncontact dynamic measurement of cantilevered beams in atomic force microscopy.

Acoustic-Excitation Optical Coherence Vibrometer for Real-Time Microstructure Vibration Measurement and Modal Analysis

Cutting tool is an important part of machining processes which in the operation frequently runs into wear. The wear cutting tool produces an imprecise product with low quality surface, may endanger machine tools by stimulating chatter. In this study, low cost and fast analysis of the wear of cutting tools in turning and drilling processes are proposed. For that purpose, the experimental set-up which consists of operating turning and drilling machine, simple microphone and Personal Computer (PC) with a sound card are set out. The wear of cutting tools are made by applying artificial wear. The sound data from normal and wear cutting tools of operating turning and drilling machines are recorded by using simple microphone and PC with a sound card. The obtained sound signals are then analyzed in the form of time and frequency domain, spectrogram by Wavelet Transform (WT). It is found that sound signals in time and frequency domain have a significant rise of amplitudes in wear conditions. The spectrograms exhibit the special contours which sign the existence of wear. The results demonstrate that the proposed method can analyze the cutting tool wear very well.

https://iopscience.iop.org/article/10.1088/1757-899X/830/4/042028/pdf

Cutting tool wear analysis using sound signal and simple microphone

: This paper discuss the machine condition monitoring based on vibration signal. This signal will be used to obtain the information of machine health, so that it can be determine the need of machine maintenance and prevent the more damages. Signal acquisition is obtained through vibration sensor, amplifier, signal conditioning, data acquisition, and signal processing. The implementation of the machine condition monitoring was done on the fault of rolling bearing in the centrifugal pump, and crack detection on the shaft. Analysis of vibration signal septrum on the machine could show the indications of the bearing fault and crack on the shaft. Keywords : Machine Monitoring, Vibration Signal, Data Acquisition, Signal Spectrum

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Pemantauan Kondisi Mesin Berdasarkan Sinyal Getaran

Chatter is a problem that frequently found in the area of a machining process, which brings down machining productivity and surface quality. Therefore, reliable and intense chatter detection methods are needed to maintain machining quality. In this study, turning chatter detection approach by using sound signals and a simple microphone is proposed to get an accurate, simple, and low-cost detection method. For that purpose, an experimental set-up which consists of an operating turning machine, simple microphone, and Personal Computer (PC) with sound card was arranged. The chatter in the turning process was stimulated by applying artificial wear to the cutting tool. The sound signal data from normal and with chatter turning process were then grabbed by a simple microphone and PC with a sound card. The sound signals were then evaluated by Fast Fourier Transform (FFT) and Wavelet Transform (WT) for normal and chatter conditions. Both conditions data were then compared to get the characteristic of the sound signal in chatter. It is found that signals in the frequency domain, time-frequency and spectrogram have a significant magnitude spike in chatter condition. The results demonstrated that the proposed method could conscientiously identify the chatter.

Chatter detection in turning process using sound signal and simple microphone

The dynamic characteristics of system, namely the damping ratio, natural frequency, and mode shape are extracted from the frequency response function (FRF). Obtaining dynamic characteristics through FRF on large rotor system is impractical owing to safety and cost. Therefore, the dimensional scale method to predict FRF on a large rotor system is proposed. The method begins by deriving the scaling factor of FRF followed by its validation using finite element (FE) and transfer function modeling. In this case, the transfer function completes the FE modeling to describe the FRF system and compensates the lack in FE modeling in dealing with complex support and shape. Assuming the damping ratio is constant, the characteristic of dimensional analysis through FRF is obtained and the complexity of the proposed method is also discussed.

Dimensional analysis of a rotor system through FRF using transfer function and finite element methods

Pada sistem poros rotor yang berputar seringkali terjadi getaran. Getaran yang muncul pada mesin khususnya pada sistem rotor dinamik kemungkinan disebabkan oleh beberapa faktor, diantaranya adalah adanya massa tak seimbang pada rotor atau poros, ketaksesumbuan poros (misalignment), cacat pada bantalan (bearing defect), pemasangan rumah bantalan yang longgar, dan sebagainya. Dengan bantuan analisis sinyal getaran dapat diketahui fenomena getaran yang terjadi pada sistem. Pada penelitian ini, dilakukan kaji eksperimental terhadap fenomena getaran pada sistem poros rotor yang memiliki massa tak seimbang pada rotor dan ketaksesumbuan poros akibat diberikannya perpindahan paksa (enforced-displacement) pada poros. Untiuk itu dibuat sebuah model alat uji rotor dinamik yang diputar oleh sebuah motor AC, terdiri dari tiga tumpuan bantalan dengan satu piringan massa. Untuk pencuplikan data digunakan accelerometer sebagai transduser, pulse analyzer Bruel & Kjoer tipe 3560C sebagai perangkat pencuplikan dan pengolahan sinyal, perangkat lunak MATLAB 6.1 digunakan sebagai pengolah dan penyaji data. Dari hasil pengujian terungkap bahwa untuk kasus akibat massa tak seimbang diperoleh spektrum frekuensi dengan nilai amplitudo yang tinggi pada frekuensi 1 x frekuensi putaran motor, dan untuk kasus ketaksesumbuan diperoleh spektrum frekuensi dengan amplitudo yang tinggi pada frekuensi harmonik putaran poros.

Experimental study of vibration on rotor system due to unbalance mass and misalignment

This paper deals with scale-fullscale models of rotor-bearing systems on rotating condition. The investigation is focused on the gyroscopic effect, which causes forward and backward whirl frequencies. When the rotor-bearing system is scaled proportionally in its dimension (height, length, and width), the scaling factor of whirl frequencies can be derived. It depends on the ratio between a transverse and polar moment of inertia on its rotating axis called the gyroscopic factor. The experimental study is conducted to validate it on three scaled rotor-bearing systems, which shifts its disc from the middle of the shaft on the scale of 1:1, 2:1, and 3:1 to clearly show the gyroscopic effect on first bending natural frequency. The scaling factor is then validated using the Campbell diagram by finding its critical speed. From this critical speed, the whirl frequencies along the range of the full-scale model speed can be obtained. The result also shows that the scaling factor remains the same whether it is at rotation or rest condition. Consideration must be made on the effect of the structural design, that is, blade and support, because of its unsymmetric stiffness that can cause backward whirl frequencies. The bearing stiffness must be ensured to be scaled proportionally, especially on journal bearing cases. This finding can be used by engineers to deal with scaling method implementation on rotating machinery design.

Gyroscopic effect on a scaled rotor-bearing system

This research is conducted to determine the natural frequencies of a twisted beam with different orientation of principal axes numerically using Autodesk Inventor. Further, the results are compared experimentally. To simplify in the analysis, the twisted cantilever beam is divided into two segments model. The orientation between two segments is simulated and tested variously. The natural frequencies obtained numerically and experimentally are selected only in transverse vibration based on the simulation of each mode shape of the cantilevered beam. In general, the natural frequencies of the simulated cantilever beam and experiment results tend to similar results.

https://iopscience.iop.org/article/10.1088/1757-899X/602/1/012069/pdf

Natural frequencies of twisted cantilever beam

A main drive is an important mobilizing motor component in a raw mill. Due to the extremely condition of constant operation of the raw mill results in failure of the main drive. This disturbs the raw mix intake and halts the next processes. In order to observe and diagnose the cause of failure on the main drive, it is important to conduct a maintenance. The Predictive maintenance technique utilized in this research is the vibration analysis technique. The measuring process of the vibration is conducted through the use of transducer velocity in radial and axial directions on the drive and non-drive components of the RIM03 motor and the symetro gear. The vibration, spectrum, velocity, and speed of rotation are analyzed in the x-Viber. Based on the vibration measurement data, the root cause of vibration can be analyzed through spectrum velocity. In this research, the critical result is found at the LS symetro gear. The occurred problem on the LS symetro gear is caused by misalignment shaft on the symetro gear connecting to gear pinion. The solution which can be applied is heat treatment to the shaft, therefore misalignment can be reduced.

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Jhon Malta

Papers

Dimensional analysis of a rotor system through FRF using transfer function and finite element methods

Experimental study of vibration on rotor system due to unbalance mass and misalignment

Gyroscopic effect on a scaled rotor-bearing system

Natural frequencies of twisted cantilever beam

Analisis Kerusakan Melalui Predictive Maintenance pada Main Drive Raw Mill Indarung II/III