Dynamic Analysis allows us to understand the behaviour of a structure under a time-varying load. The time-varying load induces time-varying response (displacements, velocities, accelerations, forces, and stresses). This characteristic of dynamic analysis makes them more complicated, but also more realistic than static analysis.
A dynamic analysis, unlike a static analysis, does not ignore real time effects; it includes inertia and damping. As a general rule, if the loading is applied gradually and the excitation frequency is less than 1/3 of the structure’s lowest natural frequency, then a dynamic analysis may not be necessary and a static analysis may be acceptable.
- Types of Dynamic Analysis
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Modal Analysis - is the most fundamental of all the dynamic analysis types. It is used to calculate the vibration characteristics (natural frequencies and mode shapes) of a structure. Often the goal of modal analysis is to design the vibrational modes of a system away from its known operating frequencies. An example of this is bridge design, where to avoid pedestrian-induced synchronous lateral excitation; resonant modes with a significant lateral component should be above 1.5Hz.
Harmonic Analysis - is used to determine the steady-state response of a structure to harmonically time-varying loads of known amplitude and frequency. It is used to analyse components of rotating equipment such as compressors, engines, pumps, and turbo-machinery.
Spectrum Analysis - An extension of the modal analysis, used to calculate stresses and strains due to a response spectrum input. Used to determine how a component responds to earthquakes.
Random Vibration PSD input (power spectral density).
Spacecraft and aircraft components
Often standards will state a spectral to be used for random vibration analysis for example IEC 61373 for the Shock and vibration tests of rolling stock equipment
Transient Dynamic Analysis - Used to determine the response of a structure to arbitrarily time-varying loads. Allows for the modelling of nonlinearities such as contact.
Explicit Dynamic Analysis - Explicit dynamic analysis is used for large deformation, short duration and complex contact problems.
- Associated Products
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ANSYS Structural
ANSYS Explicit STR
Reurdyn
ANSYS LS-DYNA
LS-DYNA
ANSYS AUTODYN
Mechanisms Dynamic Option