ME’scopeVES – Overview

What is ME’scopeVES?

The ME’scopeVES Visual Engineering Series of software packages and options makes it easier for you to observe and analyze noise & vibration problems in machinery and structures using either experimental or analytical data.   With ME’scope, you can import or directly acquire multi-channel time or frequency data from a machine or structure, and post-process it. Its industry-leading interactive 3D animation allows you to observe order-related operating deflection shapes from running machinery, resonant vibration and mode shapes from real structures, acoustic shapes, and engineering shapes directly from acquired data. In addition to its photo-realistic interactive animated display, ME’scopeVES contains state of the art tools for performing:   •  FRF-Based Modal Analysis •  Operational Modal Analysis •  Vibro-Acoustic Analysis •  Dynamics Modeling & Simulation •  Structural Dynamics Modification •  FEA Model Updating

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 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 a test article.  You can stop the animation, back it up, and play it forward to observe in slow-motion phenomena that may have taken place very quickly in real time.   With frequency-based ODS animation, you simply move the cursor to a frequency of interest in your data, and the ODS for that frequency is displayed.  With this animation, you can observe resonant vibration as well as order-related and other types of forced vibration.

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, they can be curve fit using FRF-based curve fitting methods to obtain operating mode shapes.

Vibro-Acoustic Analysis

This option post-processes and displays Acoustic Intensity, Sound Pressure Level (SPL), and Sound Power. It allows you to analyze 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 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 you to graphically document the breakdown of acoustic energy measured from various components of a test article. 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, you can quickly investigate the effects of structural modifications on the modes of a structure. 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 so 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.

FEA Model Updating

By importing an FEA model and its mode shapes, or constructing an FEA model and solving for its modes prior to a modal test, this option helps you determine proper sensor and exciter locations for the test.  Following the test, you can compare the FEA & EMA mode shapes both graphically and numerically to validate your results.  Finally, selected properties of the FEA model can be updated so that its modes more closely match the EMA modal parameters.

This option includes the following features

  • Import FEA models & mode shapes from popular FEA packages
  • Export FEA models & mode shapes in popular FEA file formats
  • Numerical comparison of FEA & EMA mode shapes using
    1. Modal Assurance Criterion (MAC)
    2. Shape difference Indicator (SDI)
  • Animated comparison of FEA & EMA mode shape pairs with highest MAC values
  • SDM-based FEA model updating.
    • Only requires FEA & EMA mode shapes, and FEA elements to be updated
    • Fast & efficient evaluation of thousands of solutions in minutes
    • Evaluates and orders FEA solutions to match
      • EMA frequencies
      • EMA mode shapes
      • EMA damping
    • FEA element properties that can be updated
      • spring stiffness, mass, linear damping
      • rods (cross sectional area)
      • bars (cross sectional area & inertias, Young’s modulus, density, poisons ratio)
      • plate elements (thickness, Young’s modulus, density, poisons ratio)
      • solid elements (Young’s modulus, density, poisons ratio)
    • FEA model creation using industry standard FEA elements The FEA element library includes;
      • springs, masses & dampers
      • rods (with axial stiffness)
      • bars (with axial, shear & bending stiffness)
      • plate elements (triangular & quadrilateral)
      • solid elements (tetrahedra, prisms and bricks)
    • FEA normal & complex mode shape solvers
      • Includes a normal mode solver for FEA models without damping, and a complex mode solver for FEA models with proportional damping.
    • EMA mode shape expansion
      • FEA mode shapes are used to add translational & rotational DOFs to EMA mode shapes
    • EMA & OMA mode shape scaling using FEA modes