In mechanical vibration systems, over-damping and under-damping are two possible scenarios that can occur. Let's discuss the causes of each:
- Over-damping: Over-damping occurs when the system is excessively damped, resulting in slow response and a longer time to reach equilibrium. The causes of over-damping include:
High damping coefficient: Over-damping is primarily caused by a high damping coefficient (damping factor). A high damping coefficient leads to increased energy dissipation, which slows down the system's response to external forces or disturbances.
Excessive viscous damping: Viscous damping is commonly used to model the energy dissipation in mechanical systems. If the damping element, such as a damper or viscous fluid, provides excessive damping, it can lead to over-damping. This may occur due to incorrect design or the selection of a highly viscous fluid.
Insufficient stiffness: In some cases, insufficient stiffness in the system can result in over-damping. When the stiffness is too low, it takes longer for the system to reach equilibrium, even with sufficient damping. This can occur when the stiffness of the spring or supporting structure is not adequately matched to the system's mass and damping.
- Under-damping: Under-damping occurs when the system is under-damped, leading to oscillatory behavior and prolonged settling time. The causes of under-damping include:
Low damping coefficient: Under-damping typically arises from a low damping coefficient or insufficient energy dissipation in the system. A low damping coefficient allows more energy to remain in the system, resulting in oscillations that take longer to damp out.
Inadequate damping elements: If the damping elements, such as dampers or shock absorbers, are not properly designed or are absent altogether, the system may become under-damped. Damping elements are crucial in dissipating energy and reducing oscillations.
Excessive stiffness: While insufficient stiffness can cause over-damping, excessive stiffness can lead to under-damping. When the stiffness of the system is too high, the system may exhibit excessive resilience, causing oscillatory behavior that persists for an extended period before settling down.
It's worth noting that critically-damped systems strike a balance between over-damping and under-damping, providing the fastest response to disturbances without oscillation. Achieving critical damping involves setting the damping coefficient to a specific value that avoids both under-damping and over-damping.