Lecture 5 Free vibration Part 2 Flashcards
1
Q
What is classed as lightly damped
A
zeta < 0.2
2
Q
log decrement =
A
ln (xn-1/xn)
3
Q
alternative form of underdamped free vibration equation
A
see book
4
Q
log decrement simplified form (time period)
A
zeta * wn * taud
5
Q
log decrement simplified form
A
2 PI() Zeta/ sqrt(1 - zeta^2)
6
Q
log decrement for lightly damped system
A
2 PI () Zeta
7
Q
logDec for several cycles
A
logdec = 1 /n * ln (xo/xn)
8
Q
what can logdec be used for
A
estimating zeta when given the time history of a response
9
Q
low damping zeta from logdec
A
zeta = ln(x0/xn) / wn * tdrop
where tdrop is the time taen to fall from x0 to xn
