Applied Modal & Operating Deflection Shape Analysis

Overview

This 4½ day course provides a basic understanding on how to use Experimental Modal Analysis (EMA) and Operating Deflection Shape (ODS) Analysis.

 

The focus of this class is on applying these powerful diagnostic tools on real-world machinery and structures rather than expending class time on deriving high-level mathematical formulas (a background in differential equations and Laplace transforms will aid the student in comprehending concepts taught, but is not required since such mathematics is now taken care of by the software).

 

Knowing how to employ ODS and Experimental Modal Analysis has become particularly important today now that Resonance is one of the leading (and often, The Leading) problem to which today’s machinery is subjected.

 

The emphasis in this class will be on how to properly perform ODS and EMA measurements, how to interpret their results from computer animations, and how to formulate meaningful recommended corrective actions required to resolve problem conditions found.

The following topics are covered:

  • Theory - Experimental Modal Analysis (with primary focus on impact excitation).
  • Theory - Operating Deflection Shape (ODS) analysis.
  • Extensive overview of ME'scopeVES v6.0 software and hands on use (about 50% of class time).
    • Creating a Project
    • Drawing Structures (3D Models)
    • Importing Data to ME'scopeVES
    • Curve Fitting Data (Modal Analysis FRF and ODS data)
    • Animating Models
    • Analyzing and Interpreting Test Data Results (ODS, ODS FRF, and Modal)
    • Documenting Test Results
  • Test setup and performing Impact Modal Tests.
  • Test setup and performing ODS Analysis on rotor kit.
  • Determining the dynamic forces acting on a machine's bearing housing or support structure.
  • Introduction to Structural Dynamics Modifications (SDM) to predict the effect of modifications to the model (before modifications are actually made to the test structure).
  • Introduction to developing Finite Element Analysis models using ME'scopeVES.
  • Case studies of industrial machinery vibration problems analyzed using Experimental Modal and ODS Analysis.

Class Focal Point

The focal point of this class is to learn how to use the capabilities of an excellent software package (ME'scopeVES) and how to simplify what formerly were complex methodologies making them practical and demonstrating how these powerful ODS and Modal analysis tools can be applied on machinery and support frame/foundation problems that are encountered on a daily basis.

Prerequisites

  • Students should have 4 to 8 years vibration spectrum analysis experience.
  • Prior experience with natural frequency testing and ODS analysis will help students improve comprehension of the techniques taught.
  • Laptop computer must be brought to the class to allow participation in numerous class exercises. Full capability ME'scopeVES software (deluxe version) will be loaded onto student computers, along with sample computer models and actual ODS & Modal data.

Special Lab Day on 5th Day of Class

  • Put into Practice What You Have Learned during the First 4 Class Days
  • Perform ODS Analysis on a Rotor Kit
  • Perform Modal Analysis on a Real-World Support Frame
  • Use ME'scopeVES to Download Data, Develop Computer Animations, Detect Problems Found and Formulate Optimum Corrective Actions

Seminar Agenda

Experimental Modal Analysis (EMA)

  • Definition of Modal Analysis & Review of its Applications
  • Design Optimization
  • Diagnostics on a Variety of Machine Types & Structures
  • Troubleshooting Specific Problems
  • Confirming When Resonance Exists & What Component is Resonant
  • Condition Monitoring Program Enhancement via Modal Analysis

Mode Shapes

  • Definition of Mode Shapes & Importance in Resolving Resonance Problems
  • Mode Shapes of Simple Machines & Structures
  • Mode Shapes of More Complex Machines & Structures
  • Mode Shape Types - Rigid Body, Bending & Torsional Modes
  • Unique Mode Shape & Damping for Each Excited Natural Frequency

Modal Analysis Requirements

  • Overview of Mathematics & Concepts Behind Modal Analysis
  • Multi-channel Analyzers - Spectrum Analyzers or Certain Data Collectors
  • Modal Analysis Software Available
  • Structural Modification Software
  • Excitation Instruments - Impulse Force Hammers, Shakers, etc.

Frequency Response Functions (FRF's) & Related Topics

  • Definition of FRF's
  • Types of FRF's (Dynamic Compliance, Dynamic Stiffness, Mobility, Impedance, Accelerance & Effective Mass)
  • Choice of Proper FRF Type for Specific Machine or Structure
  • Damping – Real vs. Imaginary
  • Use of Real or Imaginary Component for Plotting Mode Shapes
  • Coherence Function - Definition and Importance of Coherence on Ensuring Quality Modal Analysis Results
  • Cross Channel Phase Measurements

Modal Analysis Rules of Thumb

Modal Analysis Demonstrations on Real Structures & Machines

  • Comparison of Results From Instruments Available Today
  • Demonstration of Optimum Techniques Taught
  • Frequency Response Functions
  • Modal Damping
  • Mode Shapes
  • Interpreting Modal Animation Results
  • Development of Required Corrective Actions

Modal Analysis Case Studies

  • Turbine Foundation & Bearing Pedestal Resonances Driving an ID Fan
  • Detection of Cracks on a Large Gearbox due to Operation Near Resonance
  • Resonance Detection on the Frame of a Belt-Driven Blower
  • Resonance on a Paper Machine Slitter Frame

 

Introduction and Course Overview

  • Definitions of Experimental Modal & Operating Deflection Shape Analysis
  • Terminology of Modal and Operating Deflection Shape Analysis
  • Instrument, Transducer & Software Requirements for Modal Analysis
  • How Modal Analysis Differs from Operating Deflection Shape Analysis (ODS)
  • General Modal and Operating Deflection Shape Analysis Test Methods
  • What will Modal Analysis Tell You about the Machine and/or Structure Tested?

Single Channel “Bump" Testing With a Variety of FFT Analyzers

  • Single Channel FFT and Time Waveform Measurement
  • Recommended Specific Measurement Setups on Various Analyzers
  • Importance of Proper Triggering
  • Phase Behavior Below, At, & Above Resonance
  • Probable Natural Frequencies
  • Background Forcing Frequencies
  • Corrupted Data - How to Detect & Correct
  • Hammer Type and Tip Hardness - Effect on Excited Frequencies
  • Limitations of Single Channel Bump

Operating Deflection Shape Analysis (ODS)

  • Definition of ODS Analysis & Review of its Applications
  • Self-Induced Motions of Machinery
  • Defining “How Much” Motion Present
  • Defining “Time-Varying” Motions
  • Resonant or Non-Resonant Responses
  • Animating The Vibrating “Shape”

ODS Rules of Thumb

ODS Demonstrations

  • Demonstration of Optimum Techniques Taught
  • Use of Instruments from Various Vendors
  • Animating ODS Computer Model
  • Interpreting ODS Animation Results
  • Development of Required Corrective Actions

ODS Case Studies

  • Excessive Flexure on a Large Scrubber Fan at 3X Fan RPM
  • Structural Weakness & Flexure on a Paper Machine Support Frame
  • Misalignment, Excessive Frame Flexure & Ineffective Isolators on a Process Fan

Seminar Fee: $1995

A $100 DISCOUNT will be given for payments at least 60 DAYS prior to the seminar start date.

Seminar Fees include textbook, breaks and lunches.

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1230 West Morehead Street, Suite 400

Charlotte, North Carolina  28208