Pre-Conference Courses

 

Lights, Camera, IMAC!
Rosen Plaza Hotel, Orlando, FL  |  February 10-13, 2025

Operational Modal Analysis: Background, Theory & Practice (2-Day)

DATE/TIME:
Saturday-Sunday, February 8-9, 2025  |  9:00 a.m. - 6:00 p.m.
 

DESCRIPTION:
This preconference course covers the theory and practice of Operational Modal Analysis (OMA). It will cover the theory behind popular analysis techniques, such as Frequency Domain Decomposition (FDD) and Stochastic Subspace Identification (SSI). Practical measurement techniques will be reviewed, both in case of well-separated and closely spaced modes. The OMA techniques will be illustrated by several application examples from Civil Engineering Structures such as buildings and bridges, and Mechanical Engineering Structures such as automotive and aerospace and space structures. Other topics like statistical based damage detection and Structural Health Monitoring (SHM) based on Operational Modal Analysis framework will also be covered. The theory will be illustrated by several demonstrations originating from real life measurements, as well as by actual field and laboratory tests during the second day of the course.

 

WHO SHOULD ATTEND:
Engineers and researchers who have basic knowledge of modal analysis and who would like to expand their knowledge into the field of Operational Modal Analysis in order to be able to solve problems when the excitation is unknown as for civil structures excited by wind, traffic etc. or mechanical structures exhibiting self-generated vibration during operation.

 

COURSE OUTLINE:

• Welcome and Introduction
• Signal vs. System Analysis
• Operational Modal Analysis Theory
• Frequency Domain identification techniques (FDD, EFDD, CFDD)
• Time Domain Identification techniques (SSI)
• Harmonic Detectiondetection and reduction in the time and frequency domains
• Use of Projection Channels, Time-Frequency Analysis
• Test Planning and Data Quality Control
• Application Examples and Case Studies
• Hands-on tests and practical case studies
• Demonstration of educational and commercial software

 

INSTRUCTORS:

 

COURSE FEE
The regular course fee is $1,000 and the student fee is $500. Course fee includes lunches, course handout material, and refreshment breaks. Lodging and additional food or materials are not included.

 

CANCELLATION LIABILITY
If the course is cancelled for any reason, the Society for Experimental Mechanics’ liability is limited to the return of the course fees.

Attendees may want to bring personal laptops, but they are not required. Course notes and limited term licenses of OMA software will be provided.

 

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Modal Domain Approaches for Nonlinear Identification and Analysis in Industry

DATE/TIME:
Saturday, February 8, 2025  |  9:00 a.m. - 6:00 p.m.
 

DESCRIPTION:
While many methods have been proposed to experimentally characterize structures that exhibit nonlinearity, very few methods have proven robust enough for regular use in industry. Many industrial applications demand methods that do not require nonlinearities to fit a specific functional form or to be localized to a few known locations. Furthermore, methods must be robust to noise and be applicable to structures where many modes of vibration can be active simultaneously. This course provides an overview of methods for detecting and characterizing nonlinearity, with a focus on methods that have been applied broadly and to a wide range of structures and types of nonlinearities.

The course covers methods based on both free and force responses. The former utilizes the Hilbert Transform to post process impact excited measurements to understand how the natural frequency and damping ratio of each mode of interest varies with vibration amplitude. Forced response techniques, including swept-sine, force appropriation and response-controlled testing are also elaborated and application examples are presented. The concept of a quasi-linear behavior of a nonlinear system is covered in detail and used to develop several of these methods. Quasi-linear approaches are powerful and form the basis of the describing function method and the nonlinearity matrix concept, both of which are utilized in the analytical modal analysis of nonlinear systems and are discussed in this context. The course ends by highlighting the limitations of modal approaches and potential directions for future research.

 

WHO SHOULD ATTEND:
The course is designed for practicing engineers, students and faculty interested in better understanding nonlinear structural dynamics and employing experimental methods to characterize them. The experimental methods build on traditional linear modal analysis techniques and hence are readily grasped by an experimentalist familiar with linear modal analysis.

 

OUTLINE:

• Introduction to Nonlinearity Including Real World Examples
  • Phenomena observed in general nonlinear systems including internal resonances and modal coupling
  • Introduction to quasi-linear and modal models
• Testing Techniques Including Hammer, Sine Beat and Force Appropriation
  • Techniques for detecting nonlinearity
  • Common pitfalls including the unique case of bilinear systems
• Quasi-Linear Behavior and Analytical Modal Analysis of Nonlinear Systems with Discrete Nonlinearity
  • Nonlinearity matrix concept
  • Analytical modal analysis of nonlinear systems
• Quasi-Linear Behavior and Experimental Modal Analysis of Nonlinear Systems
  • Response Controlled Stepped-Sine Testing (RCT)
  • Modal identification and nonlinear modal models by RCT
  • Experimental modal analysis of nonlinear systems
  • Applications to complex engineering systems
• Quasi-Linear Modal Methods for Identification of Nonlinearity
  • Hilbert Transform identification
  • Restoring Force Surface (RFS) identification methods in the time and frequency domain
• Modal Coupling and Future Work
  • Case studies where modal coupling has been observed and characterized

 

INSTRUCTORS:

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.

COURSE FEE
The regular course fee is $500 and the student fee is $250. Course fee includes lunches, course handout material, and refreshment breaks. Lodging and additional food or materials are not included.

CANCELLATION LIABILITY
If the course is cancelled for any reason, the Society for Experimental Mechanics’ liability is limited to the return of the course fees.

Attendees are encouraged to bring their own laptops. None will be provided.

 

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Optical Techniques for Experimental Modal Analysis

DATE/TIME:
Sunday, February 9, 2025  |  9:00 a.m. - 6:00 p.m.
 

DESCRIPTION:
Optical techniques have the ability to measure large quantities of data on surfaces of test articles to produce full-field datasets for model validation. While several commercial and open-source optical measurement packages exist, there is no complete modal analysis software that incorporates optical techniques, so practitioners are often left assembling an optical experimental modal analysis capability on their own. This course will provide basic instruction for those practitioners who would like to develop an experimental modal analysis capability using optical techniques.

This course will cover the basics of optical measurements, including cameras and lenses, lighting, patterning, and 2D and stereo DIC. It will then discuss practical aspects of combining optical techniques with experimental modal analysis. Finally advanced topics in optical methods will be discussed.

 

COURSE SCHEDULE:

1. Introduction – Bryan Witt – 9:00 a.m.
   1. Introduce instructors and students
   2. General overview of optical techniques
   3. When are optical techniques useful
   4. Comparison to Laser Doppler Vibrometry
2. Imaging Basics – Dan Rohe – 9:30 a.m.
   1. General Camera Concepts and Terminology
   2. Camera Geometry and Pinhole Model
   3. Reconstructing 3D from 2D
   4. Camera calibration
   5. Some considerations when selecting a camera/lens for a given test
3. Break – 11:15 a.m.
4. DIC – Phil Reu – 11:30 a.m.
   1. Overview of 2D DIC and test parameters
      1. Subset and step sizes
      2. Interpolants
      3. Correlation settings
   2. Patterning and Lighting of test article
   3. Stereo DIC
   4. High-speed DIC considerations
   5. List of current software packages
   6. Measurement uncertainty
5. Lunch – 1:00 p.m.
6. Practical aspects of Optical Testing for Experimental Modal Analysis – Bryan Witt – 2:00 p.m.
   1. Test planning
      1. Frequency range
      2. Estimating pixels of displacement
      3. Additional instrumentation/data acquisition system
   2. Test setup
      1. Camera Selection
         1. High resolution
         2. Memory requirements
         3. Nonvolatile memory
      2. Camera Mounting
      3. Part preparation/speckling
   3. Test Execution
      1. Synchronizing camera and data acquisition system data
      2. Averaging reference images to reduce noise
      3. Excitation strategy
         1. Hammer excitation difficulties
         2. Shaker excitation/advantages and drawbacks of specific excitation signals
         3. Shaping excitation signals
      4. Image averaging
   4. Postprocessing and Mode Fitting
      1. Handling Correlation drops
      2. Aligning coordinate systems
      3. Combining optical and sensor data
      4. Computing FRFs
      5. Fine alignment of time delay between data acquisition and camera
      6. Noise mitigation
7. Break – 3:45 p.m.
8. Advanced Techniques – Dan Rohe – 4:00 p.m.
   1. Motion Magnification
   2. Synthetic Images
   3. Radiographic Imaging
9. Conclusions and Wrap up – Phil Reu – 5:30 p.m. – 6:00 p.m.

 

WHO SHOULD ATTEND:
People who are familiar with experimental modal analysis who are interested in incorporating camera-based measurements into their modal testing activities.

 

INSTRUCTORS:

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.

COURSE FEE
The regular course fee is $500 and the student fee is $250. Course fee includes lunches, course handout material, and refreshment breaks. Lodging and additional food or materials are not included.

CANCELLATION LIABILITY
If the course is cancelled for any reason, the Society for Experimental Mechanics’ liability is limited to the return of the course fees.

Attendees are encouraged to bring their own laptops. None will be provided.