Resolving machine vibration problems using ODS and Modal Motion Analysis

In case of recurring machine failures, it is recommended to proactively look for the causes. Here, dynamic movements in and around the machine often play a prominent role. Unexpected flexibilities and deformations can result in a source of complex forces and excessive vibrations. Although Experimental Modal Analysis (EMA) and Operational Deflection Shape Analysis (ODS) are often considered advanced techniques, they can also be approached very pragmatically. This course provides an applicable introduction to these techniques and teaches how simple measurement tools can be used to gain additional insights into machine behaviour. Practical examples and demonstrations are used throughout the training. The day ends with a number of interesting cases.

• How do we describe a dynamical system?
• What is resonance and what is a natural frequency?
• How do we deal with resonance in our system?
• What is Operational Deflection Shape (ODS) and Modal Analysis (EMA/OMA), and how do we apply them?

• Introduction to vibration and system dynamics (Bram Vervisch)

To start the training day, the basic concepts within vibration theory are briefly and powerfully repeated. The relationship between various concepts such as amplitude, phase, frequency, bottom plot, frequency response function (FRF), coherence, etc. is made clear in this session. This is important in order to be able to start the following sessions in the same way. A dynamic system with variable degrees of freedom is characterised here pragmatically and mathematically.

• Resonance, natural frequencies and solutions (Bram Corne)

From the previous session, this section looks at the concept of resonance. Influential parameters such as mass, damping and stiffness will be discussed as well as ways to map resonances or natural frequencies (bump-test, run-up, coast-down, impact test...). In addition, we also look more closely at the possible solutions if resonance is established in an industrial application. This is driven by practical examples and cases.

• ODS, OMA and EMA (Bram Vervisch)

This session forms the core of the seminar. The techniques of an Operational Deflection Shape (ODS), an Operational Modal Analysis (OMA) and an Experimental Modal Analysis (EMA) are fully explained. Both from a practical and a theoretical point of view, these analysis techniques are linked to their specific applications. The student will not only get an insight in why a certain technique is applied, but also in how it is applied.

• Case studies and demonstration (Bram Vervisch and Bram Corne)

The different theoretical approaches throughout the training day are revisited during these sessions with a direct link to the industry. Each of the cases presented are real-life examples that the lecturers have handled themselves, explaining in detail the situation, approach, diagnostic process and solution strategy. Classroom demonstrations are also provided to showcase each of the different techniques.