This is an excerpt from a white paper authored by Noah Buschard, Applications Engineer at Rogers. Noah breaks down the concepts of Vibration Isolation and Damping in Material Design.
Vibration management should always be considered in any engineering design. Applications that have effectively incorporated vibration management surround us every day, from buildings to rail cars. Even the mirrors on our cars have to pass a vibration test to ensure visual clarity at high speeds. Designs that neglect to properly address vibration often result in malfunctioning components and, in some cases, catastrophic failure.
The Two Facets to Vibration Management: Isolation and Damping
There are two facets of vibration management: isolation and damping:
- Isolation is the prevention of vibrations from entering a system.
- Damping is the absorption of the vibration energy that is entering the system and dissipating it by changing the kinetic energy of vibration into a different form of energy.
The two forms of vibration management are different from each other, but often are used in conjunction to achieve the desired performance.
To best understand vibration, there are a few key concepts to consider:
- Transmissability which is defined as the percent of vibrational energy that is being transmitted through a structure
- Natural frequency also known as resonant frequency, is the specific frequency at which a material will naturally vibrate
Damping and isolation are very different approaches to vibration management, but are often used interchangeably in conversations and specifications. It is important to recall the definitions mentioned above and understand that isolation and damping have different effects on the system. In fact, having a large amount of damping has a negative effect on isolation and vice versa. In Figure 8, it can be seen that as the damping ratio increases the region of isolation decreases.
The easiest way to determine whether a damper or an isolator is needed is to identify the frequencies that are of concern. Selecting the correct isolator will shift the natural frequency lower and move the frequencies of concern into the region of isolation, preventing them from penetrating the system. When the system’s natural frequency can not be shifted lower and the frequencies of concern are located near or at the natural frequency, damping is the appropriate method of vibration management.
This paper will be available for download in a few weeks. An updated link will be provided at that time.