A Dynamic Substructure Technique For Multiple Impact Dynamics Of Complicated Flexible System

Multiple-impact dynamics of complicated flexible system increasingly attract attentions of scientist with the rapid development of morden industry. However, since it is related to variable contact topology, impact-induced transient wave, dynamic responses in variable time scale and nonlinear effect et al., multiple impacts dynamics of complicated flexible system is still not well understood. In this thesis, to solve the multiple-impact transient responses and the impact-induced transient wave phenomenons of complicated flexible system, the dynamic substructure technique (DST) was developed to study some contents briefly described as the followings:(1) A basic theory of DST was developed to account for multiple-impact dynamics of complicated flexible system. Since the governing equations of impact phase and separate phase and the determination method for the initial conditions of displacement and velocity of each phase were presented, the present DST can be adopted to solve multiple-impact problem and calculate the propagation of the impact-induced transient waves even if the impact bodies have space motion and finite deformation before impact.(2) The present DST was applied to investigate the propagation of transient waves excited by multiple impacts. Its availability was validated successfully. The applications include the impact-induced longitudinal wave propagations in uniform bar, discontinuous bar and micro/nano piezoelectric actuators and the impact-induced transverse wave propagations in simply supported beam.(3) Considering the transverse inertia of flexible bar, a new DST was proposed, which can study the geometric dispersion of impact-induced transient wave. The DST solutions were compared with those of the Releigh-Love bar theory and 3-dimension explicit finite element method LS-DYNA.(4) The present DST was adopted to study the multiple-impact problems of some flexible systems, such as a cantilever uniform bar longitudinally struck by a rigid block, a simply supported uniform beam transversely struck by a rigid sphere and a non-homogeneous discontinuous bar longitudinally struck by a rigid block.(5) Considering the electromechanical coupling effect of piezoelectric ceramics and the inertial effect of flexible components, a DST was presented to study the multiple-impact problem of micro/nano piezoelectric impact drive systems. It can investigate the step-like motion of the object body and the multiple-impact behaviors reasonably by the comparison of the experimental data and the numerical solutions of the spring-mass model.