Modal Analysis Measurement Systems
Modal analysis is a technique used to determine the dynamic properties of a structure or system, such as natural frequencies, damping, and modal shapes. Widely used in mechanical, aerospace, civil, and automotive engineering, it is essential for optimizing design, diagnosing structural problems, and predicting dynamic behavior.
This technique relies on specific measurement systems, composed of sensors, actuators, and processing software, which allow for accurate results. Thanks to the combination of advanced technologies and established methodologies, modal analysis is an indispensable tool for understanding and optimizing the dynamic behavior of structures across various application areas.
Types of Modal Analysis
Experimental Modal Analysis (EMA)
It requires direct measurement of the system's responses, excited artificially (using a shaker or instrumented hammer).
Modal shape identification based on the frequency response function (FRF).
Operative Modal Analysis (OMA)
Based on environmental or natural excitations, without controlled input.
Used in civil structures or large infrastructures.
Numeric Modal Analysis (NMA)
Theoretical calculations through FEM (Finite Element Method) simulation software.
Validation with experimental results.
Components
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Accelerometers: The primary tools for measuring dynamic responses. They can vary in sensitivity, frequency range, and size, making them suitable for different applications.
Displacement Transducers: Used to measure dynamic deformations or displacements in specific contexts.
Laser Doppler Vibrometers (LDV): For non-intrusive vibration measurements on surfaces.
Strain Gauges: Used to measure local deformation related to vibrations.
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Electrodynamic Shakers: Generate controlled vibrations with variable amplitude and frequency.
Instrumented Hammers: Used to provide an impulsive dynamic input. They are equipped with a force transducer to measure the magnitude of the excitation.
Pneumatic or Hydraulic Systems: Used for large-scale excitations, especially in civil structures.
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DAQ (Data Acquisition): Hardware systems capable of digitizing analog signals with high resolution and speed.
ADC Modules (Analog-to-Digital Converter): Converters with precision specifications for dynamic signal analysis, equipped with anti-aliasing filters and simultaneous sampling across channels.
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Used for:
Modal Identification: Natural frequencies, damping, and modal shapes.
Time-domain (IRF) or frequency-domain (FRF) analysis.
Data validation through curve fitting.
Measurement Protocols
System Preparation
Selection of measurement points and strategic placement of sensors.
Calibration of accelerometers and instrumented hammers.
Definition of boundary conditions (constraints and loads).
Data Acquisition
Excitation of the structure using appropriate techniques.
Real-time recording of the dynamic response.
Measurement of FRF (Frequency Response Function) or IRF (Impulse Response Function).
Post-Processing
Data filtering and validation.
Curve fitting to extract modal parameters.
Animation of modal shapes for visual assessment.
Reference Products
NVA - Noise Vibration Anaylzer
The reference tool for studying dynamic signals.
NVT - Noise Vibration Tester
Multi-Purpose Measurement Software for Acoustic and Vibration Phenomenon Analysis
NVT-HMS - Health Monitoring System
Integrated System for Vibration and Dynamic Parameter Monitoring
Applications
Identification of resonances in machines and components, and fault diagnosis.
Reduction of vibrations and noise (NVH - Noise, Vibration, Harshness)
Dynamic evaluation of bridges, buildings, and infrastructures.
Study of aerodynamic vibrations and structural modes in aircraft and satellites.