Calculation of natural frequencies and eigenmodes
Eigen frequencies (also known as natural frequencies) and modal shapes are two essential notions for understanding and describing the vibratory behavior of a system.
Natural frequencies, modal shapes and damping
Natural frequencies correspond to the frequencies at which a system enters into resonance. At each resonance frequency, a particular deformation of the object is observed: its mode shape.
These intrinsic characteristics of a structure can be:
- Calculated in preliminary design in order to anticipate any problem: resonance frequency too low or in coincidence with a vibration source (motor, bearings, rotating machines).
- Measured to identify the origin of a failure or to readjust an existing digital model.
In addition, when a structure resonates, the damping controls the amplitude of the vibration response. It is therefore essential to know a priori, this property through structural damping, also called hysteretic, or viscous damping.
These two damping models can be determined from experimental measurements and an identification of the eigenmodes of the structure. These models can be the subject of the creation of material maps in order to be taken into account in the digital models.
Tests and calculations by CEVAA
The CEVAA and the various entities of the 6NAPSE Group, offer to support you on these issues either through its skills in Dynamic Structure Calculation and Calculation/Test Correlation, or by Vibration Tests which can for example be carried out by Laser Scanning Vibrometry or even by Materials Characterization Tests.
The CEVAA has the means of testing and calculations to meet the needs of its customers to intervene on this theme.
Many projects carried out in fields such as automotive, aeronautics, railways or even Defense allow us today to be at ease on a panel of diverse and varied products and parts (blades, vehicle tanks, braking system, industrial equipment, etc.).
The use of finite element type software (Optistruct from the HyperWorks suite, Nastran from the MSC Software suite, Code_Aster developed by EDF) makes it possible to carry out these calculations which, after analysis of the results, can be the subject of recommendations/recommendations from the from our teams.
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