1 For the dynamic system a Determine the equilibrium equatio

1. For the dynamic system,
(a) Determine the equilibrium equations in the generalized coordinate system (degrees of freedom) shown in the figure. m=mass, J=rotary inertia, k=stiffness (spring or torsional stiffness in shafts), etc.
(b) Compute the natural frequencies of the system.
(c) Compute the modes of the system and make a sketch of them.
(d) Compute the mass normalized modes and verify that the modes are mass orthogonal.
(3) 2k X2 no S

Solution

a) As two mass are connected together by linear springs. Then independent coordinates are position mass of left side & right side so their will two degrees of freedom.

Looking at mass on left side, change in length of spring k2depends on both mass positions (see attached F.B.D)

-k1x1 + k2(x2-x1) + f1(x) = m1x1

Above equation suggest there will be two natural frequencies with two possible solutions

= sqrt (k/m)

= sqrt (3k/m)

solving Eigen vector equation

2k   -(k/m)m     -k                     X11                              0

                                                                        =

0       -k          2k-(k/m)m          X21                               0

Natural frequency is

X1 = X11 {1

                  1}

b)Modal shape is

ø = 1    1

      1    -1

c) Solution for each mass is

x(t) =xi ejit

1. For the dynamic system, (a) Determine the equilibrium equations in the generalized coordinate system (degrees of freedom) shown in the figure. m=mass, J=rota

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