Static studies assume that loads are constant or applied very slowly until they reach their full values. Because of this assumption, the velocity and acceleration of each particle of the model is assumed to be zero. As a result, static studies neglect inertial and damping forces.
For many practical cases, loads are not applied slowly or they change with time or frequency. For such cases, use a dynamic study. Generally if the frequency of a load is larger than 1/3 of the lowest (fundamental) frequency, a dynamic study should be used.
Linear dynamic studies are based on frequency studies. The software calculates the response of the model by accumulating the contribution of each mode to the loading environment. In most cases, only the lower modes contribute significantly to the response. The contribution of a mode depends on the load’s frequency content, magnitude, direction, duration, and location.
Objectives of a dynamic analysis include:
- Design structural and mechanical systems to perform without failure in dynamic environments.
- Modify system's characteristics (i.e., geometry, damping mechanisms, material properties, etc.) to reduce vibration effects.