Inverse Sub-structuring Analysis For Product Transport System With Difficult-to-Measure Interface Based On FRF Probe Techniques

In the field of transport packaging,the product transport system can be regarded as a coupled multi-level system composed of product,package and vehicle.In the system,product(critical component)is the weakest and plays the most important role in cushioning packaging design and damage monitoring.Therefore,it’s extremely important to measure and monitor the dynamic characteristics of products.However,the measurement faces many difficulties as follows:(a)Many packages are opaque so it’s impossible to monitor them by eyes;(b)The structural changes and material damages cannot be distinguished by eyes though packages are transparent.(c)It will waste many human and material resources to monitor the product by opening packages.For the reasons given above,the inverse sub-structuring method has developed fast recently due to its function that can obtain the dynamic characteristics of product by those of coupled system.Unfortunately,packaging structures are spatially complex and the dynamic characteristics at coupling interface of product transport system are usually difficult to measure.To solve the problem,the paper proposes a set of probe techniques,which can measure the dynamic characteristics at coupling interface indirectly.The proposed method makes inverse sub-structuring analysis more workable.The study mainly includes:(a)To solve the problem that measurement for FRFs at coupling interface in coupled system is very difficult,FRF probe techniques including variable cross-section probe and shearing probe are proposed respectively,which can break through different kind of spatial limitation,based on existing probe technique.Besides method for measurement of auto FRFs,method for cross FRFs is also established,which make it workable to obtain entire FRF matrix by probe technique.(b)To know more about the reason and relationship between varieties of factors and probe technique,many kinds of FEMs(finite element models)are established by Ansys workbench.The influence of probe mass is focused and improvement for formulation is presented.(c)The variable cross-section probe is applied to single-coordinate coupled system,including single-coordinate rigidly coupled system and single-coordinate flexibly coupled system,to obtain the FRFs at coupling interfaces indirectly.The indirectly measured FRFs are used to predict FRFs of products by inverse sub-structuring method.(d)The shearing probe is applied to multi-coordinate coupled system,including multi-coordinate rigidly coupled system and multi-coordinate flexibly coupled system,to obtain the FRFs at coupling interfaces indirectly.The indirectly measured FRFs are used to predict FRFs of products by inverse sub-structuring method.