Applied
Modal & Operating Deflection Shape Analysis
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APPLIED MODAL & OPERATING DEFLECTION SHAPE ANALYSIS
This
4-1/2 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
today even to apply these tools to complex mechanisms & structures
since such mathematics is now taken care of by the software).
Knowing
how to employ ODS and Modal methods have become particularly important
today now that Resonance is now one of the leading (and often,
The Leading) problems to which today’s machinery is subjected.
That
is, 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
students are provided with structural models of plant machinery
to generate and import Experimental Modal and Operating Deflection
Shape analysis measurements, and to create machinery animations.
Students are then given an overview on how to: Establish a Project;
Create a Structure; Import Data; Interpret data (ODS, ODS FRF,
and Modal); accomplish Modal Analysis Curve Fitting; and employ
Structural Dynamics Modifications (SDM) needed to predict the
effect of modifications within the model before such modifications
are fabricated and put onto place.
However, the focal point of this class is not to learn how to
use all the capabilities of an excellent software package (ME’scopeVES),
but instead on 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 they encounter on a daily basis.
Notebook computer with Windows XP or Windows Vista is required
for loading of ME'scope Demo Software Package.
| APPLIED MODAL & OPERATING DEFLECTION SHAPE ANALYSIS SEMINAR AGENDA |
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?
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Definitions
- Natural Frequency, Critical Speed & Resonance
- The Resonance Phenomenon
|
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 Tests
|
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
- Determining Anticipated Forcing Frequency Amplitudes & Dominant Directions
- Using Single Channel Transducer & Phase Reference
- Limitations of Single Channel ODS Measurements
- Using the Two Channel Method - Reference & Roving Transducer
- Determining the Optimum Locations & Direction for the Roving Transducer
- Getting Repeatable Measurements
- Using Velocity to Obtain Best Frequency Response for Most Problems
- Determining When to Use Other Vibration Parameters
- Setting the Optimum Frequency Range for Specific Problems
- Setting Optimum Frequency Resolution
- Reducing Spectral Leakage by Choosing Best Window Function
- Specifying the Required Number of Measurement Points & Directions
- Checking for Reasonable Animation Motion
- Adjusting for Varying Time & Load
- Keeping Accurate Records of Locations & Measurement Directions
|
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
|
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
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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 Shapes 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
- Acquiring Baseline Data with & without Machine Running
- Setting Proper Frequency Range, #Lines & #Averages for Modal Measurements
- Using Proper Window Function
- Using Proper Excitation Method to Display All Modes of Interest
- Viewing Both the Input & the Response Time Waveform
- Using Exponential Decay Window
- Checking Coherence Function at FRF Peaks to Determine Measurement Quality
- Determining Required #Measurement Points & Directions
- Using Force Window to Reduce Measurement Noise
- Accurate Curve Fitting
- Keeping Accurate Records of Locations & Measurement Directions
- Animating Modal Analysis Computer Model
|
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 Large Gearbox due to Operation Near Resonance
- Resonance Detection on the Frame of a Belt-Driven Blower
- Resonance on a Paper Machine Slitter Frame
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Prerequisites
- Students should have 4 to 8 years vibration spectrum analysis experience.
- Prior
formal vibration training & experience with phase
analysis and spectral analysis, plus exposure to natural
frequency testing is recommended in order to allow the
student to become proficient with the application of Modal
Analysis & Operating Deflection Shape Analysis covered
within this 4-day seminar.
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