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Modal Analysis Software

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Modal Analysis Software by ME’scope

Analysis and Post-Processing of Structural Vibration Data


ME’scope is a series of software packages and options that make it easy to post-process experimental noise and vibration data, analyze and also display data as animated shapes.  ME’scope helps  solve a variety of vibration and vibro-acoustic problems.  With new ME’scope options, machinery and structures can be monitored over long time periods, and notifications can be sent when vibration or noise levels have exceeded prescribed levels.

Multi-channel time or frequency data can be imported from disk files, or directly from a machine or structure.  The industry-leading photo-realistic interactive 3D shape animation allows order-related operating deflection shapes from running machinery, resonant vibration and mode shapes from real structures, vibro-acoustic shapes, or engineering data of any kind derived directly from experimental data to be observed. ME’scope contains state of the art tools for:

  • Operational Deflection Shapes (ODS), Mode Shapes, or Vibro-Acoustic Animation
  • FRF-Based Modal Analysis
  • Operational Modal Analysis
  • Vibro-Acoustic Analysis
  • Dynamics Modeling & Simulation
  • Structural Dynamics Modification
  • Experimental FEA
  • Rotating Machine Monitoring
  • Environmental Monitoring
  • Qualification Testing

ODS Animation

An Operating Deflection Shape (ODS) is the simplest way to see how a machine or structure moves during its operation, either at a specific frequency, or at a moment in time.  An ODS contains the overall dynamic response of a structure due to forced and resonant vibration. Time-based ODS animation sweeps a cursor through a set of time histories describing motions at multiple points and directions on the test object. The animation can be stopped, backed up, and played forward again to observe in slow-motion phenomena that may have taken place very quickly in real time. With frequency-based ODS animation, the cursor is moved to a frequency of interest in the data, and the ODS for that frequency is displayed.  Using animation, resonant vibration, order-related vibration, or other types of forced vibration may be observed.

FRF-Based Modal Analysis

Modal analysis is used to characterize resonant vibration in mechanical structures.  Each resonance has a specific “natural” or modal frequency, a modal damping or decay value, and a mode shape.  FRF-Based parameter estimation (or curve fitting) is used to estimate the modal parameters of a structure from a set of FRFs.   At the heart of the Basic Modal Analysis option is the ME’scope Polynomial method, an easy to use MDOF curve fitter. This curve fitter can be used to simultaneously extract parameters for multiple modes, especially in cases of high modal density.  It can also extract local modes where the resonant vibration is confined to a local region of the structure.   The Multi-Reference Modal Analysis option contains all of the features of the Basic Modal Analysis option, plus additional methods for curve fitting a multiple reference set of FRFs. Multi- Reference curve fitting is used to extract closely coupled modes and repeated roots (two or more modes at the same frequency).  This option contains a Stability diagram for locating stable pole estimates, and three additional curve fitting methods: Complex Exponential, Z-Polynomial, and the patented AF Polynomial method.

Operational Modal Analysis

When the excitation forces causing a structure to vibrate are not measured, then FRFs cannot be calculated, and modal parameters can only be extracted for output-only or operational measurements. Nevertheless, a key advantage of OMA is that data can be acquired under real-world operating conditions. This option contains all of the features of the Multi-Reference Modal Analysis option, plus special tools for curve fitting measurements obtained from output-only or operating data. A common OMA measurement is a Cross spectrum, which is calculated between a roving accelerometer and a reference (fixed) accelerometer. After a set of Cross spectra has been specially windowed, FRF-based curve fitting methods can be used to obtain operating mode shapes.

Vibro-Acoustic Analysis

This option post-processes and displays Acoustic Intensity, Sound Pressure Level (SPL), and Sound Power Level. It enables the analysis of vibro-acoustic problems by displaying both vibration and acoustic data together in the same animated picture. Acoustic Intensity is measured with a two to four channel acquisition probe and a multi-channel data acquisition system. Each Intensity measurement is made either normal to an acoustic grid or surface, or in three directions (tri-axially) at each grid point. Sound Power flow through an acoustic surface is calculated from Intensity data. Sound power is displayed on the acoustic surface using a color map. Interactive Source Ranking allows the breakdown of acoustic energy measured from various components of a test article to be documented. Acoustic sources can be ranked according to their percentage of the total power, in dB units or watts.

Dynamics Modeling & Simulation

This option uses a Multiple Input Multiple Output (MIMO) dynamics model to calculate Inputs, Outputs, and Transfer functions. Each part of the model can be calculated from the other two.   Transfer functions can be calculated from multiple Input and Output time waveforms. Time domain windowing (Rectangular, Hanning, or Flat Top), linear or peak hold spectrum averaging, triggering, and overlap processing can be applied during Transfer function calculations. Ordinary Coherences are also calculated for single Inputs, and Multiple & Partial Coherences are calculated for multiple Inputs. Multiple Output time waveforms or frequency spectra can be calculated from Transfer functions and multiple Input time waveforms or frequency spectra, and animated ODS’s can be displayed directly from the Outputs. Transfer functions can be derived from experiment or from mode shapes. Inputs can be derived from experiment or synthesized. Similarly, multiple Input time waveforms or frequency spectra can be calculated from Transfer functions and multiple Output time waveforms or frequency spectra. The Outputs can be derived from experiment or synthesized. This capability can be used for Force Path Analysis.

Structural Dynamics Modification

If a noise or vibration problem is due to the excitation of a resonance, the structure must either be isolated from its excitation sources, or physically modified to reduce its vibration response levels. With this option, the effects of structural modifications on the modes of a structure can be quickly investigated. The new modes can then be used in MIMO calculations to determine the effect of structural modifications on overall vibration levels. SDM models structural modifications using industry-standard FEA elements. The FEA element library includes the same elements used by the Experimental FEA option. All modification elements are displayed on the 3D structure model. Each element type has its own spreadsheet, where its properties can be viewed and edited. SDM works with either analytical (FEA) modes or experimental modes of the unmodified structure. Because the new modes of the structure are calculated very quickly, SDM can be used for Modal Sensitivity studies, where thousands of solutions are calculated and ranked for comparison. SDM also includes a special command for adding tuned vibration absorbers to a structure.

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