Dynamic Modeling Theory And Experiment Investigation For Flexible Multi-Body System With Contact-Impact

In this dissertation, modeling theory and experiment technique for flexible multi-body system with single-point and multiple-point contact-impact are investigated. Based on Euler-Bernoulli assumption, and considering geometric nonlinear effect and local deformation of the impact point, Dynamic model for flexible multi-body system with contact-impact is established by using nonlinear spring-damper model. Furthermore, various factors that may affect the dynamic behaviors are taken into account, and the structural damping effect as well as softening effect due to temperature increase is investigated. Different experiments for the single-point and multiple-point contact-impact are designed and carried out. The agreement of the simulation and experiment results verifies the applicability of the nonlinear spring-damper impact force model, and the importance of the effect of the flexibility, damping and the temperature variation. The main contents are described as follows:In chapter 1, the engineering application background and the significance of the research work on contact-impact of flexible multi-body system are introduced. The research development of the theoretical analysis and experiment investigation for the contact-impact of flexible multi-body system is reviewed. In addition, the research trend and important problems of the contact-impact are put forward, and the objective of the research is proposed.In chapter 2, dynamic theoretical model for flexible multi-body system with single-point and multiple-point contact-impact is established using nonlinear spring-damper model. Firstly, based on Euler-Bernoulli assumption and precise strain-displacement relationship, dynamic equations considering geometric nonlinear effect of an elastic beam are established using absolute nodal coordinates. Furthermore, the contact-impact force calculation model is proposed. The effect of the damping as well as the effect of the temperature variation on the elastic stiffness is taken into account, and then, according to the kinematic constraint equations, dynamic equations of the multi-body system with contact-impact are assembled. Finally, the module chart of simulation of flexible multi-body system with single-point and multiple-point contact-impact is designed.In chapter 3, simulation and experiment research on flexible multi-body system with single-point is carried out. Considering the contact-impact between a flexible rod and a beam, a contact-impact model of flexible multi-body system, which takes various physical factors into account for engineering applications, is put forward. In such model, the effect of the structural damping of each flexible body as well as the effect of the damping force in the spring model is considered. According to the relation between the structural damping coefficient and the rate of decay of the vibration amplitude, free vibration experiment is carried out to measure the structural damping coefficient. The agreement of the simulation and experiment results verifies the correctness of the modeling theory. Based on these, significant effect of the flexibility and damping on the impact behavior is revealed, especially in case that the elastic vibration is excited. Finally, the beam is locally heated in order to show the softening effect due to the temperature increase.In chapter 4, simulation and experiment research on flexible multi-body system with multiple-point is carried out. Designing experiment among a steel sphere, a flexible rod and a flexible beam, the agreement of the simulation and experiment results verifies the applicability of the modeling theory on flexible multi-body system with multiple-point. The time variation between the active impact and passive impact is shown. Furthermore, significant effect of the flexibility and structural damping on the multiple-point impact behavior is revealedIn chapter 5, the investigations of contact-impact in this dissertation are summarized and the prospect of the research is proposed.