What are real and complex modes?
According to whether the modal parameters (mainly referring to the modal frequency and modal vector) are real or complex, the modal can be divided into real modal and complex modal. For an undamped or proportionally damped vibration system, the vibration phase difference at each point is zero or 180 degrees, and its modal coefficient is a real number, which is the real mode at this time; for a non-proportional damped vibration system, each point has a different phase except for the amplitude The difference is not necessarily zero or 180 degrees, so that the modal coefficient is a complex number, that is, a complex mode is formed.