Experimental Study On Flexible Cylinder Rods Impacts

The experimental research of the longitudinal impact between two flexible cylinder rods was investigated. On purpose of delving into the dynamics response during the contact process, the experiment setup of the impacts between two flexible bodies was designed, the contact duration was accurately measured according to the conductivity of aluminum, and the non-contact measurement for the velocity response of the flexible rod during the impact process was non-contact measured by the Laser Doppler Vibrometer. Furthermore the strain at the point near the contact region was implemented by the dynamic strain amplifier. The wave propagation in the flexible rod is revealed through the research. The comparison between experimental and numerical results of Hertz's contact law and FEM-λmodel shows that Hertz's contact law is not applicable for the impact between flexible bodies, and FEM-λmodel, which considers the effect of flexible wave processes higher accuracy.The main contents are described as follows:In chapter 1, the engineering application background and significance of the experimental study on contact-impact of flexible multi-body system are introduced. The research development at home and abroad is summarized. The difficult of the problems which is not solved or not completely worked out is expounded. In addition, the objective of the research is proposed.In chapter 2, the experimental program of contact-impact between two flexible cylindrical rods is designed. The excellent repeatability and feasibility of the experiment is verified.In chapter 3, the important significance of accurately measuring the contact time is elaborated, as well as the principle of the contact time measuring system. The influence of the contact time under different initial velocities and materials is researched. According to the comparison between experimental and FEM simulation results, it is not appropriate to handle a flexible cylinder rod with an aspect ratio by 50:1 as an one-dimensional rod, for the impact end is processed as an hemispherical end.In chapter 4, the dynamical responses, including velocity response, acceleration response, displacement response and the strain of the point near the contact district are measured. According to the analysis and comparison between the dynamical response and simulation results, FEM-λmodel is more appropriate than Hertz contact law in this problem, and two-dimensional FEM simulation has a precise outcome, while one-dimensional FEM simulation has a much more larger error. The wave propagation in the flexible rod is revealed through the research.In chapter 5, the contribution and innovation of this paper are summarized and the prospect of the research is proposed.