2020-2021 / MECA0062-1

Vibration testing and experimental modal analysis

Duration

26h Th, 26h Pr, 30h Proj.

Number of credits

 Master of Science (MSc) in Aerospace Engineering, professional focus in turbomachinery aeromechanics (THRUST)5 crédits 
 Master of Science (MSc) in Aerospace Engineering5 crédits 
 Master of Science (MSc) in Mechanical Engineering (EMSHIP+, Erasmus Mundus)5 crédits 

Lecturer

Jean-Claude Golinval

Language(s) of instruction

English language

Organisation and examination

Teaching in the first semester, review in January

Schedule

Schedule online

Units courses prerequisite and corequisite

Prerequisite or corequisite units are presented within each program

Learning unit contents

Vibration sensors: displacement, speed, acceleration. Signal analysis: power spectral density, discrete Fourier transform, FFT algorithm, digital spectrum analyzers, aliasing and leakage phenomena. Excitation methods in vibration: types of excitation signals (impact, sine sweep, pseudo-random, etc.), electrodynamic exciter, impulse hammer. Theoretical background of modal analysis: transfer function, receptance, mobility, impedance, Bode diagram, Nyquist diagram, development of the dynamic influence coefficient matrix in terms of poles and residues. Identification methods: phase separation and phase resonance methods, identification of modal parameters on the basis of the frequency or impulse response functions, 1 DOF-method(peak picking, circle fitting) and multi-DOF methods, influence of residual terms, multiple excitation. Introduction to model updating methods in linear elastodynamics. Diagnosis of the mechanical state of a machine through vibratory measurements.

Learning outcomes of the learning unit

The aim of the course is to train students to use vibration measurement equipment in laboratories, to acquire, process and exploit the vibratory signals as well as modal identification methods, comparison techniques between theoretical and experimental results and parametric correction methods for structural models on the basis of experimental results.

Prerequisite knowledge and skills

This course requires a basic knowledge in mechanical vibrations.

Planned learning activities and teaching methods

The lab sessions are organised in groups and upon appointment only. The first session is led by a member of the staff from the Vibrations and Identification of Structures Laboratory. It is aimed at allowing students to familiarise themselves with the measuring equipment available in the laboratory. During the following sessions, students work independently on a real lattice-work type of structure or an airplane mock-up. An individual report has to be handed in within a set deadline to be agreed upon with the students. It must include: 1. the detailed description of the measurements made in the laboratory on the test structure, 2. the development and application of two modal parameter identification methods (mode, frequency and damping) of the structure based on the experimental results obtained, 3. the construction and exploitation of a finite element model of the structure tested in the MATLAB or SAMCEF environment, 4. the qualitative and quantitative comparison between theoretical and experimental results. The lab sessions are MANDATORY. Any unjustified absence may lead to the refusal of participation in the final exam.

Mode of delivery (face to face, distance learning, hybrid learning)

The course is organised face-to-face during the first quadrimester.

Organisational adjustments related to the current health context

If the sanitary conditions do not allow to be present at the university, the exam will be organised orally by visio-conference.

Recommended or required readings

  • N. Maia, J. Silva, Theoretical and Experimental Modal Analysis, Research Studies Press Ltd., 1997, ISBN 0-86380-208-7
  • D. J. Ewins, Modal Testing: Theory, Practice and Apllication, Research Studies Press Ltd., 2000, ISBN 0-86380-218-4

Assessment methods and criteria

Below you will find information on the evaluation methods planned for in-person and remote exams as well as those planned for hybrid sessions. Depending on how the health crisis evolves, the chosen method will be communicated to you no later than one month before the start of the exam session.

The final grade will be based on the project report and the written exam:   1. The grade of the project report will be based on the results and the quality of the report (scientific and technical content, conciseness, structuring of the written report and clarity of the text). An oral presntation will be organised at the end of the project.   2. The written exam will consist in answering to questions related to the theoretical concepts presented during the lectures. No document is allowed for the exam.    Student assessment criteria:

  • Project report: 75%.
  • Exam: 25%.
The assessment is based on the weighted geometric average of the project and the exam. The final note is calculated as follows:
                  Final note = (Project)^(0.75) * (Exam)^(0.25)

Work placement(s)

Organizational remarks

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Contacts

Jean-Claude GOLINVAL (JC.Golinval@uliege.be)
Assistant : Olivier DEVIGNE (o.devigne@uliege.be)