B6377 - Mechanical Vibrations

Learning outcomes

Through the Integrated Course COMFORT RELATED TO SOUND AND VIBRATION, the student acquires fundamental knowledge of airborne acoustic waves and their perception by humans, as well as of mechanical vibrations and the associated challenges in marine engineering. The course provides the theoretical and practical foundations necessary to define, quantify, and measure the principal acoustic and vibrational parameters using standardized methodologies. Students develop competence in signal analysis within both the time and frequency domains, and gain familiarity with the principles of experimental modal analysis applied to naval structures and components. The course also covers the selection and application of acoustic materials in accordance with international technical standards. Finally, the student learns to evaluate and implement engineering solutions for noise control and for the reduction and isolation of vibrations in vessels, with the aim of improving onboard comfort.

Course contents

1. Mechanical vibrations.
Fundamentals of mechanical vibrations.
Single Degree of Freedom Systems: free and forced vibrations; resonance; viscous damping; Coulomb damping; hysteretic damping. Two Degrees of Freedom Systems. Multi-degree of Freedom systems. Continuous Systems: mono and bi-dimensional systems. Approximate methods (Rayleigh and Rayleigh-Ritz).

2. Vibration measurements and Signal analysis
Vibration measurement scheme. Vibration transducers. Frequency analysis: Leakage. Data sampling: Aliasing; Shannon's theorem. Discrete Fourier Transform. Definition of acquisition parameters. Auto- and Cross- Spectrum. Frequency Response Function (FRF) and Coherence function.

3. Experimental Modal Analysis (EMA).
Introduction to experimental modal analysis. Impact hammer and shaker. System excitation: random, impulsive, sinusoidal. Procedure outline. Examples.

4. Vibration reduction and isolation for onboard comfort.
Main sources of onboard vibration. Overview of relevant standards. Vibration isolation. Dynamic damper. Solutions for passive vibration control.

Readings/Bibliography

Lecture slides are available on https://virtuale.unibo.it/.
1. Rao S.S., Mechanical vibrations, Sixth edition, Pearson Education, 2018.
2. Inman D.J., Engineering Vibration, 4th edition, Pearson Education, 2014.

Teaching methods

The course is based on lectures dealing with the theoretical aspects of the course topics and application examples.
Class attendance, although not mandatory, plays a fundamental role in the learning and evaluation process.

Assessment methods

The final exam is oral and includes questions aimed at verifying the acquisition of the knowledge outlined in the course syllabus and at assessing the achievement of the learning objectives.

The use of Artificial Intelligence (AI) tools during the examination is strictly prohibited in any form. Any such use constitutes a violation of academic integrity.

In accordance with the University Didactic Regulations, students may request the cancellation of a positive grade and retake the examination. The following rules apply:

• a positive grade may be cancelled only on the day of the examination;
• a cancelled grade cannot be reinstated under any circumstances;
• each student may request grade cancellation only once during the course.

Teaching tools

Blackboard, PC.
On the E-learning Platform (https://virtuale.unibo.it/), students may find: slides of the course lectures; exercises and application examples.

Office hours

See the website of Alessandro Rivola