Classical Modal Analysis

Modal analysis is vital to understanding and optimising the inherent dynamic behaviour of structures, leading to lighter, stronger and safer constructions, less fuel/power consumptions, higher comfort, and better performance.

In modal analysis a mathematical model of a structure’s dynamic behaviour is obtained. The mathematical model consists of a set of mode shapes each with an associated natural frequency and modal damping. These modal parameters provide a complete description of the structure’s dynamic behaviour.

Experimental Modal Analysis is based on determining the modal parameters by testing, unlike Analytical Modal Analysis, where the modal parameters are derived from Finite Element Models (FEMs). There are two ways of doing Experimental Modal Analysis: Classical Modal Analysis and Operational Modal Analysis . In Classical Modal Analysis frequency response functions (or impulse response functions) are calculated from measured input forces and output responses of a structure. In Operational Modal Analysis only the output responses are measured. The ambient and operating forces are used as unmeasured input.

Classical Modal Analysis is used in a vast range of applications including:

• Optimisation of the structure’s dynamic properties (mass, stiffness, damping)
• Ensuring that resonances are away from excitation frequencies
• Prediction of the dynamic behaviour of components and assembled structures
• Prediction of the forces from measured responses
• Prediction of the responses due to complex excitation
• Prediction of the effect of structural modifications
• Inclusion of damping in Finite Element models
• Correlation of test models with Finite Element models
• Updating of Finite Element models using test results
• Damage detection and assessment

Classical Modal Analysis ranges from simple mobility tests with impact hammers to multi-shaker testing of large and complex structures with hundreds of response accelerometers. Brüel & Kjær’s modal solution are expandable and can grow with your requirements.

Structural Dynamic Test Consultants

Modal Test Consultant (MTC) Type 7753 and Operating Deflection Shapes Test Consultant (ODSTC) Type 7765 are PULSE applications developed to simplify and dramatically reduce the time required to perform structural dynamic measurements. Together they are referred to as Structural Dynamic Test Consultants. MTC supports both Classical Modal Analysis and Operational Modal Analysis. 

The Structural Dynamic Test Consultants utilise the PULSE multi-analysis platform. They are graphically driven and easily controlled, linking the measurement directly to the on-screen test object geometry. These features, together with highly effective tools for setup, measurement and validation, make testing fast and reliable. ODS results can be animated directly in ODSTC and FRFs directly in MTC. The data generated (time, spectra, geometry and DOF information) can then be used directly by your chosen post-processing package, such as PULSE Reflex Modal Analysis, PULSE Reflex Correlation Analysis, Test for I-deas^® or ME'scopeVES^TM (all available through Brüel & Kjær).

PULSE Reflex Modal Analysis

PULSE Reflex Modal Analysis is an easy-to-use post-processing application that enables you to perform single and poly-reference Classical Modal Analysis even in the most demanding situations. Accurate results are quickly obtained by following an intuitive, yet flexible workflow process that guides you efficiently through measurement validation, parameter estimation setup, mode selection, analysis validation and reporting.

PULSE Reflex Modal Analysis can be used as a stand-alone application by importing standard measurement data and geometry file formats. However, using PULSE™ Modal Test Consultant™ Type 7753 for geometry-driven data acquisition and validation, then seamlessly transferring data to PULSE Reflex Modal Analysis Type 8720/8721 for analysis and validation, comprises a truly integrated, easy-to-use and powerful modal test and analysis system.

	Modal Test Consultant is graphically driven, linking the measurement directly to the on-screen test object geometry. The user is safely guided through the specific tasks required for the test
	Points, lines, surfaces or basic shapes can be edited and combined to rapidly build up the test object geometry. Complex geometries can be imported from finite element models and decimated to test models
	Modal Test Consultant incorporates timesaving tools for maximum data reliability and shorter test time. One example is the automatic double-hit detection and rejection tool
	PULSE seamlessly handles multiple exciter testing (MIMO analysis providing accurate, precise and reliable FRF data sets for the modal parameter extraction process
	PULSE Reflex Modal Analysis provides an intuitive user interface that puts the tools you need at your fingertips. The graphical user interface is built around a workflow model that leads you easily through any analysis process
	PULSE Reflex Modal Analysis contains a targeted set of best-in-class mode indicator functions, curve-fitters, animation and validation tools

Hammer Guide