Analyzes dynamic structure

Experimental Modal analysis and by finite elements

The principle of modal analysis is to deduce from the vibratory matrices of the parameters "resonance frequencies" and "deformations of the real structure" or the prototype out of model. 

The esperimental  modal analysis is a technique that needs the acquisition of the transfer functions (interspectre) between the efforts generated by a controlled external excitation and the answer of the structure on points of discretization.

The modal extraction, which consists in establishing an incomplete modal base (Natural frequencies, clean deformations) is carried out by using smoothing methods to exploit the transfer functions acquired on the basis of suitable mathematical model taking into account the type of excitation, of the coupling of modes, and the importance of the structure.

The modal analysis by finite elements makes it possible to obtain the same results.

The applications of the experimental modal analysis are varied and many and we can quote the following scopes of applications :

• Dynamic characteristics of materials. Experimental determination of the Young modulus and structural damping.

• Precise details of the dynamic behavior of the structures. Determination of the Natural frequencies and clean deformations od a structure or model in order to confront them with the spatio-frequentiel characteristics of the excitation.

• Retiming by code FINITE ELEMENTS. It is a question of comparing the modal diagram resulting from the two mthods in order to have a retroactive action on the modeling assumptions of the finite elements model.

• Modification of the structures. Digital simulation of modification of structure strating from the experimental modal base.

• Structural connections. Simulation, numerical synthesis of two structures having each one their modal diagram resulting either from the experimentation, or of the experimentation and calculation.

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Materials used and marketed by dB Vib Technologies.

Operational deformation

Anlysis of the operational deformation with the goal to identify the answers of a structure for a real excitation frequency.

Applications :

When an installation (machine, structure of self-supporting quality, piping ...) is under operation, it vibrates at frequencies, because it is subjected to the torques of  vibratoires.

Interests

The analysis of the deformation of a structure under real excitation allows :

• to visualize the movements of the installation in 3 dimensions,

•  to locate the most vibrating points and the points of inflection for which one has the most constriants,

• to check by comparaison the effectiveness brought by a modification of structure or operating conditions of the installation.

To download our data sheet.

Materials uses and marketed by dB Vib Technologies.