Study On Dropping Impact Dynamic Characteristic Of Two-Degree-of-Freedom Packaging System

During the transportation, the packaging system can be predigested as two-degree-of- freedom systems since the main body connected with cushioning materials and the critical element connected with the main body.The critical element is always damged fristly and the theories of dropping damage boundary curve is one of core content packaging dynamics,but presently general theories are based on singal-degree-of- freedom system.In this paper, the author studied the predigestion conditions, and the theories of dropping damage boundary curve of two-degree-of- freedom systems and experimental methods to prove the theories of dropping damage boundary curve of two-degree-of- freedom systems. The research content mainly includes the followings:1.Research on the predigestion and the effect factors of acceleration respondenceBy applying the Runge-Kutta, the main effect factors were analyzed on the predigesting including mass ratio and nominal frequency ratio and the magnified coefficient method caused rather error. As a result, these factors have directly effect to the acceleration reaction when the double degree freedom system is predigested as a single-degree- of-freedom system, at the same time, and analyzed the effect factors of acceleration respondence for two-degree-of-cubic nonlinear system, two-degree-of-tangent nonlinear system and two- degree-of-hyperbolic tangent nonlinear system. The result shows that original velocity, mass ratio and nominal frequency ratio affect completely different for different nonlinear system.2.Research on the theories of dropping damage boundary curve of two-degree-of- freedom systems and experimentingThe theories of dropping damage boundary curve of two-degree-of- freedom systems were put forward with considering frequency ratio and dimensionless velocity as basic variable and mass ratio parameter variable, the dropping damage boundary curve of two-degree-of- freedom systems of linear system, two-degree-of-cubic nonlinear system, two-degree-of tangent nonlinear system and two-degree-of hyperbolic tangent nonlinear system were solved by applying Matlab,and obtain a series of dropping damage boundary curves with different parameters. This concept and methods are enriched the traditional theories of dropping damage boundary curve.The mass-spring model was used to validate the theories of dropping damage boundary curve of two-degree-of- freedom systems of linear system, two-degree-of-freedom system of cubic nonlinear and two-degree-of- freedom systems of tangent nonlinear, the result shows that the experimental data general tally with the dropping damage boundary curve, it proves that the dropping damage boundary curve is right.3.Experiment on the reaction of dropping and parameter identificationThe impact dynamic model making up of EPE and mass was established based on time parameter identification. As a result, the linear rigidity of EPE decreases with width increasing dropping from the same height, the linear rigidity of same width EPE increases with height increasing and the nonlinear parameter can't be established. The dynamic characteristics of EPE have cubic nonlinear character and change with dropping height or width. The BP neural network of EPE dynamic cushioning character was established based on dropping impact data, the test result shows that the BP neural networks is credible. In this paper, the EPE dynamic cushioning character was tested in four dropping height for the same density four kind of width EPE in the four kinds stress. The BP neural network has rather precision extended capacity for inside training specimen.