This paper presents an experimental study of the nonlinear characteristics of an axially moving string. An experimental system with a simple configuration, which is similar to a practical application, was built. Two laser sensors were used to monitor the vertical and horizontal vibrations of the moving string under different conditions. Using the Hilbert-Huang transform method, the detailed results of a typical measured data series, which include intrinsic mode decomposition, Hilbert spectrum and marginal spectrum, are introduced. For comparison, marginal spectra for almost all test cases are also given. Based on the results, several observed nonlinear phenomena, which include whirling motion, resonances, quasiperiodical and a beating motion, torus doublings and one chaotic motion, are presented. The quantitative nonlinear vibrating details and the observed rich behaviors help explain the great complexity of a single moving string.

The research object of theoretical mechanics is usually rigid rod and disc. In order to activate the teaching atmosphere of theoretical mechanics, some elements of life can be introduced in the conceptual explanation. For this reason, the family dynamics model based on force and couple is established preliminary by matching the force and couple with some elements in the family. Enlivened the classroom atmosphere and deepened students' understanding of key concepts. This teaching imaginative, broke through the engineering of the original category, associated with life, enrich the students' humanistic feelings and home care, blend in people's rational and perceptual, people become a whole person, classroom has become a whole class.