Vibration analysis with imc WAVE vibration
The acquisition and analysis of machine vibrations and vibrations on the human body can be performed in compliance with standards using imc WAVE vibration. imc WAVE offers professional tools for vibration level and band-limited vibration level analysis, as well as for frequency analysis as FFT, third-octave and octave spectra. In addition to methods for machine diagnosis, the user also has access to methods for the analysis and evaluation of vibrations on the human body.
- Filters (LP, HP, BP, BS)
- Machine diagnostics according to ISO 10816/20816
- Human Vibration Filter, Fast, Slow, Impulse, Peak, Keq
- Vibration 1/1-tel and 1/3-tel octave analysis according to IEC 61260
- FFT analysis (up to 131072 points)
- Machinery diagnosis
- Acceptance and certification measurements with the effect of vibrations on machines
- Product qualifications
- Product optimizations in the development area
- Holistic investigations of causes, propagation paths and effects of vibrations
- Standardized human vibration measurements
- Acceptance and certification measurements with the effect of vibrations on humans
- Seat comfort in vehicles: measurements for qualification and optimization
- Hand-arm vibrations: Hand-guided machines
- How do vibrations occur on machines?
- How can I measure vibrations?
- How do I perform vibration analysis on machines?
- What is frequency analysis?
- What is enveloping curve analysis?
- What are human vibrations?
- How are human vibrations recorded?
- Which frequencies and amplitudes in the human vibration analysis are particularly harmful?
Vibrations originate in in- and out-movements of machines and rotating machines and machine components, for example of pistons, compressors, rotors, shafts and rollers, as well as gearboxes and pumps. The amplitude and the frequencies depend on the natural frequencies and stiffness. Additional shocks that are caused by damage to individual components are additionally provoking vibrations on machines. Based on their amplitudes and frequencies, machine and component faults can be detected and localized, for example: unbalance, rolling bearing damage or misalignment.
In vibration analysis, we record and analyze the vibrations with accelerometers, vibration velocity sensors or vibration displacement sensors.
There are various analysis options for recording and documenting vibrations on machines. These are in particular the vibration level and the band-limited oscillation level. Frequency analysis and envelope analysis methods are used to diagnose vibrations. International standards include ISO 10816, ISO 20816, VDI 3832.
A frequency analysis can be calculated narrow-band as FFT analysis or clearly laid out as as a third-octave and octave analysis. In frequency analysis, a basic distinction is made between two methods: third-octave and octave analysis or FFT analysis.
To get detailed information about a complex sound signal, more information has to be identified about the composition of the signal's frequency. The different frequencies can be best explained with a musical scale.
The octave [lat.], describes the interval of 8 diatonic steps away from the first note. In acoustics it denotes the tonal sound that has twice the frequency, related to a first sound. Since antiquity, the representation of the western tonal system has been based on the octave. The third octave analysis (third [lat.], the third tone) is a frequency analysis with relatively constant frequency resolution, i.e. that the center frequency fm of a bandpass filter in relation to the bandwidth (fB=fO-fU) is the same for all frequency bands. The upper cutoff frequency fO and the lower cutoff frequency fU of a bandpass filter are at an amplitude attenuation of -3 dB (factor 0.707). The relative bandwidth of the octave is fB = 0.707, the third octave is fB = 0.23 and the 1/12th octave is fB = 0.059.
The one-third octave spectrum allows an evaluation of the spectral line distribution, for example of a sound signal. Its advantage is the ability to rate the logarithmic frequency of the human ear. The one-third octave filters roughly correspond in their bandwidths to the frequency groups that reach the discriminating ability of the ear. Because of this, their discriminating power is sufficient for many psychoacoustic problems, including loudness determination.
The Fast Fourier Transform (FFT) is a fast computational algorithm for calculating the discrete Fourier transform (DFT). The algorithm developed by James Cooley and John W. Tukey (1965) uses computational advantages that arise with a number of 2 to the power of N values.
In modern analysis software packages, one is no longer dependent on the number of values of 2 to the N, because if the number of FFT points is not a power of 2, the signal is interpolated to the corresponding higher sampling frequency.
In this way, various parameters can be set with imc WAVE.
- Frequency weighting: A, B, C or Z
- Averaging: none, Leq from start
- Windows: Rectangle, Hamming, Hanning, Blackman Blackman-Harris and Flat-Top
- Overlap: 0%, 10%, 25%, 33.33%, 50%, 66.66%, 75%, 90%
- Diff./Int.: differentiate, dual differentiate, integrate, dual integrate.
- Points: 128.....131072
- Log.axis: Yes / No
- Reference value dB 20 µPa = 2 E-05 Pa
- Display of: Bandwidth, resolution and output rate
Enveloping curve analysis is a method to separate (demodulate) amplitude modulated signals into carrier and damage frequencies. Therefore, it is used for the detection of damage, especially in rolling bearings. Here, each bearing has an individual fingerprint. With the help of an FFT analysis and the knowledge of the mechanic structure of the bearing, the damaging frequencies can be separated according to inner ring, outer ring and rolling element.
Human vibrations are mechanical vibrations that are transmitted to the human body. Typical machines for this are power saws, angle grinders, hammer drills, pneumatic hammers and demolition hammers. The impact of these vibrations on bones and joints leads to circulatory disorders and nerve damage, and in the long term can lead to occupational diseases such as white finger disease. A distinction is made between 2 main groups: Whole-body vibrations and hand-arm vibrations in the X, Y and Z directions.
Mostly with a triax vibration sensor or a seat vibration sensor representing vibration acceleration or vibration velocity.
If we consider the human being as a mechanical model, subdividing it into spring-mass systems, each body-part has a a different natural frequency for, which can be damaged by continuous loading. The vibration load depends mainly on the frequency, the amplitude and the applied pressure force as well as the duration of the impact. International standards include EN 1032, ISO 2631-x, ISO 28927, ISO 5349, ISO 8041 and VDI 2057.