Modal Analysis

Modal Analysis is used for analyzing pulse and transition characteristics of signals coming from the input channels of FFT spectrum analyzers and seismic stations in real time or recorded time realization view mode.

Modal analysis - shock signal - interface general view

The program helps to determine the natural frequencies and logarithmic decrements of free vibrations of mechanisms and structures by means of impact excitation impact. The additional window Spectrum displays the spectral characteristics of signals from reference and measuring channels as an impact spectrum or a spectrum based on Laplace transform. Thus, Modal Analysis can be used for inspection of building structures according to IEC 60068-2-81:2003 «Environmental testing – Part 2-81: Tests – Test Ei: Shock – Shock response spectrum synthesis» to obtain impact spectra and calculate the main tone of natural vibrations and logarithmic decrement of the main tone of natural vibrations.

Modal analysis - shock signal - interface general view-example 2

Modal Analysis is used for processing and visualization of a vibrational signal and its spectra, automatic determination of natural frequencies, phases, ratios of peak amplitudes of two signals and damping decrement of various mechanisms, parts, structures, and other items by measuring free vibrations by impact excitation.

Modal analysis - shock signal - interface general view-shock spectrum 3

Measured Parameters

  • pulse amplitude is the amplitude (pulse crest factor value) of the reference and measuring channels, in units of measurement;
  • noise RMS is the root-mean-square value (RMS) of the signal noise in the reference and measuring channels before the pulse (in units of measurement);
  • lower and upper limits of the reference and measuring channels, in units of measurement;
  • amplitude/interference ratio of the reference and measuring channels, in units of measurement;
  • amplitude ratio between the measuring and reference channels;
  • pulse width in the reference and measuring channels, in milliseconds;
  • pulse arrival time in the reference and measuring channels, in milliseconds;
  • pulse arrival time difference, in milliseconds;
  • impact spectrum;
  • frequency spectrum based on Laplace transformation;
  • free vibration frequencies and logarithmic damping decrements of pulses in the reference and measuring channels;
  • signal phase in the reference and measuring channels;

Modal Analysis: Application

Reduction of vibration caused by the structural resonance

Detection of specimen damage

Single-impact tests are used to determine the quality of the specimen and to evaluate its structural strength. Tests are carried out by exerting single impacts on the specimen placed on the vibration bench with standard pulse shapes of a certain duration and peak acceleration value. The most important test parameters are the impact strength and speed change. Acceleration impact spectra usually provide detailed information about the potential damage during operation.

Critical equipment production and assembly control

Scheduled maintenance planning

In operation, the product can suffer fatigue deformations, microcracks in joints which do not cause the product geometry to change, but affect its dynamic characteristics. Analyzing such changes allows for predicting routine maintenance.

Experimental research for scientific purposes

Sensor verification

Sensors are verified on a vibration bench by comparing the sensitivity of the test and reference vibration sensors. Verification is performed with single impacts with different durations and peak accelerations. The program calculates the duration of amplitudes, pulses, amplitude ratios, wavefront steepness, and impact acceleration pulse. These parameters serve as primary data for verification.

Modal analysis - shock signal - reference and controlled transducer parameters

Modal analysis - shock signal - interface general view-parameters configuration

Specific Features of ZETLAB Modal Analysis

  • Flexibility

    There are no requirements for the vibration exciter, which significantly simplifies the system and reduces its cost.

  • IEC 60088-2-81:2003

    Calculation of shock response spectrum according to IEC 60088-2-81:2003 (Environmental testing – Part2-81: Tests – Test Ei: Shock – Shock response spectrum synthesis)

  • Capabilities

    Simple and fast determination of natural frequencies and various vibration modes.

  • Products selection

    The program is supplied with FFT spectrum analyzers, seismic stations, and strain-gauge stations.

  • Recording of the results obtained

    Saving measurement results to a file supported by Word, Excel, or Notepad.

Supported Hardware

Modal Analysis is a part of the following software:

Modal Analysis is included in the Signal Analysis software group.

Modal analysis program in the Menu Signal analysis