抄録
A uniform density bar is suspended at its two supporting points by two strings whose two end points are attached to an upper static wall,and works as a bifilar suspension pendulum of three oscillation modes: two swinging modes and one torsional mode.There are three configurations of this pendulum: the distance between the two points at the wall is longer or shorter than that on the bar,and it is just the same.These give rise to the effects just as softening/hardening of nonlinear spring,as studied in a previous paper.When the vertical motion is included with forcing and vertical excitation,the nonlinear effects due to inertia type terms are shown to change in various ways,using the method of multiple scales and harmonic balance.The nonlinear hardening/softening may be applicable to mitigation technology
