Theoretical Study On Product Damage Evaluation And Protective Packaging Dynamics

Damage of products frequently occurs at the circulating process. A cost of thousands of million Yuan to hundreds of billion Yuan can be anticipated due to inappropriate packaging. The main reason may due to the lack of in-depth investigation of packaging dynamics.It's very important to investigate the dynamical characteristics of packaging system for packaging design. Traditionally, the product was modeled as a lumped mass, neglecting the complex configuration of most products. In fact, the product system and the vehicle system constitute a complex product-transport-system via the coupling packaging interface, and the damage of most products usually occurs firstly at the so-called critical component. In this paper, the dynamical characteristics and damage evaluation approaches of this complex system were investigated.Firstly, the shock characteristics of typical linear and nonlinear packaging system with critical component were investigated. The dynamical model of the system was developed, and the numerical results of the general dynamical equations were obtained. Then, to evaluate the shock characteristics of critical component, a new concept of three-dimensional shock response spectrum was proposed, with the dimensionless pulse duration, the frequency ratio and the ratio of the maximum shock response acceleration of the critical component to the peak pulse acceleration as the three basic coordinate parameters. Based on the results, the effect of the pulse duration, the frequency ratio, the pulse peak acceleration, the damping ratio of critical component and cushioning pad in addition to the defined system parameter on the maximum shock response acceleration of critical component was discussed. And also, a concept of damage boundary surface was proposed to evaluate the damage potential of critical component.The shock characteristics of stacking packaging system were investigated under the action of half-sine acceleration pulse. The dynamical model of the system was developed, and the numerical results of the general dynamical equations were obtained. Then, to evaluate the shock characteristics of the system, the concept of combined shock response spectrum and combined damage boundary were proposed, and the effect of peak pulse acceleration, damping ratio of cushioning pad in addition to the number of stacking layers on the combined shock spectrum and combined damage boundary of the system was discussed.The inverse substructuring method proposed by Lim was introduced to investigate the the dynamical characteristics of the system of product-transport-system. And the inverse substructuring method of one-coordinate coupled three-substructure system was deducted. The method was verified by both numerical computation and test of self-made experimental model, the measurement error sensitivity of the method was discussed and the effect of the dynamical parameters of coupling packaging interface in addition to the frequency ratio of critical component to main body on the dynamical response characteristics of critical component were analyzed. Finally, the dynamical response and transportation packaging reliability of product-transport-system under the excitation of road roughness was obtained by applying the inverse substructuring method. And then, an optimized packaging design method, namely, reliability transportation packaging design method, was proposed.