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Noise and Vibrations

Code:

LEM31127

Sigla:

VR

Áreas Científicas
Classificação	Área Científica
OFICIAL	Solid Mechanics

Ocorrência: 2022/2023 - 1S

Ativa?	Yes
Unidade Responsável:	Departamento de Engenharia Mecânica
Curso/CE Responsável:

Ciclos de Estudo/Cursos

Sigla	Nº de Estudantes	Plano de Estudos	Anos Curriculares	Créditos UCN	Créditos ECTS	Horas de Contacto	Horas Totais
EM	33	Plano de Estudos	3	-	6	60	162

Língua de trabalho

Portuguese

Objetivos

Provide students with the necessary knowledge to understand vibratory phenomena in structures and equipment.

Knowledge of the components of a vibrating system consisting of a mass/spring/damper.
Quantification of vibration signals in different quantities: acceleration; velocity; displacement.
Application of vibration measurement techniques in the conditioned maintenance of mechanical equipment.

In the field of noise, it is intended to teach students basic concepts of acoustics. Know and relate the quantities: pressure, intensity and sound power. Represent these quantities on the dB scale. Know how to add and subtract quantities in dB. Know the isophonic curves and the weighting functions (A, B, C and D). Know how to use the most common functions of noise measuring instruments (sound meter and dosimeter). Practical noise elimination solutions.

Resultados de aprendizagem e competências

The student must know how to establish and solve the equilibrium equations for a one degree of freedom system in free vibration and forced vibration. You should be able to discuss the influence of the different components on the system response and identify the phenomenon of resonance. Know how to determine the transmissibility of a system and how to isolate vibrations in equipment.

The student will know how to process vibration signals using spectral analysis (Fouier Analysis) as well as its application in the conditioned maintenance of mechanical equipment.

The student must be able to relate the quantities: pressure, intensity and sound power and represent these quantities on the dB scale and add and subtract them.

The student must know the isophonic curves and the weighting functions (A, B, C and D).

The student should have knowledge of practical noise elimination solutions.

Modo de trabalho

Presencial

Programa

Part I Vibrations
1. Introduction (8 hours)
Objectives of the study of vibrations in controlling the behavior of structures;
Dynamic request types;
Discretization of systems;
Components of a vibrating system;
Simple harmonic motion. Sum of signals. Beat;
Degrees of freedom of a system.

2. Formulation of equations of motion for one degree of freedom (22 hours)
Systems with one degree of freedom;
Free and forced vibration responses;
Systems with damping;
Response to constant amplitude harmonic requests;
Response due to the existence of unbalanced rotating masses;
Harmonic movement of the support base;
transmissibility;
Vibration isolation.

3. Signal characterizations (6 hours)
Basic measurement techniques;
Fourier analysis. Spectral Analyzers;
Transducers and conditioners;
Calibration;
Use of the computer in the acquisition and processing of data.

4. Application of vibrations in the diagnosis of equipment faults (14 hours)
Characterization of typical equipment failures;
Identification of typical anomalies: imbalance; misalignment; days off; etc;
Imbalance. One-plane and two-plane balancing techniques;
Choice of measurement points;
Presentation of historical cases of equipment failures.

Part II Acoustics
5. Acoustic Concepts (10 hours)
Sound. Pressure, intensity and sound frequency;
Sound intensity levels and their consequences on the human body;
Propagation of sound in the air and through structures;
Noise measuring instruments. sound level meters;
Measurement techniques;
Human reaction to noise;
Practical noise elimination solutions;
Norms and recommendations. General noise regulation.

Bibliografia Obrigatória

Nuno Nunes, Júlio Montalvão; Apontamentos da disciplina
Singiresu S. Rao; Mechanical Vibrations, Prentice Hall, 2011. ISBN: 978-0-13-212819-3

Bibliografia Complementar

Cyril M. Harris; Allan G. Piersol; HARRIS’ SHOCK AND VIBRATION HANDBOOK, McGraww Hill. ISBN: 0-07-137081-1

Métodos de ensino e atividades de aprendizagem

TP classes with theoretical exposition and practical applications.

Tipo de avaliação

Distributed evaluation with final exam

Componentes de Avaliação

Designation	Peso (%)
Teste	70,00
Trabalho laboratorial	30,00
Total:	100,00

Componentes de Ocupação

Designation	Tempo (Horas)
Estudo autónomo	92,00
Frequência das aulas	60,00
Trabalho laboratorial	10,00
Total:	162,00

Obtenção de frequência

To obtain success in the subject, the student will have to take two tests during the semester.
The calculation of the Final Classification follows the following expression:
.
. NF=0.4*T1+0.3*T2 + 0.3*MedTLi
.
. NF - Final Grade
. T1 - 1st Test
. T2 - 2nd Test
. MedTLi - Average of Laboratory Work



.
The grade of each of the laboratory works will be obtained
.TLi = 0.2*PAL + 0.8*Rel
.PAL - Student Preparation and Attitude for and During the Lab
.Rel - Work Report

or
NF=Examination Grade

Fórmula de cálculo da classificação final

Condition for taking advantage:
T1 and T2 >= 8.0 and NF >= 10 (after rounding)

Restrictions:


If (T1+T2)/2 < 9.5 to NF = Test Average

or
NF=Examination Grade