Abstract
Detailed and many-degree-of-freedom system of FE models are used for theoretical determination of load and stress properties of bus structures. If the vehicle overpasses individual road obstacle the nonlinearity of suspension system must be taken into account. In this case multiplied and detailed data, information shall be processed for determining the system critical points due to the solution of differential equitation. The goal is to determine the properties of bus structure’s dynamic stresses. The calculated dynamic stresses are practically independent from the particularity of the FE model, only the modal coordinates carry their dynamical properties! So the task is to calculate, estimate the vehicle critical points’ stress realisations (position and time) on the set of excitation field (signal shape, number of inputs, vehicle velocity). It has to be taken into account that using a relatively simple FE model ca. 4000 time-functions has to be processed, belonging to a single excitation. This stress-sequence gives an upper estimation (envelope curve) for the structure global stress properties. E.g. stress realisation of any structural element is practically linear combination of couple time-curves (calculation, error estimation; 5 in-phases and 2 counter-phases!). Summarizing the results of tested and calculated midi bus type IK GMC: • the bus structure’s global stress property in case of transient displacement can be adequately described, independently from the partition of the structure’s FE model (if it is appropriate to describe static stress) • in first approach the extreme stresses of the structures can be approximated by a time function (axle modal component, v<30 km/h)
Keywords: bus structure, dynamic stress, modal analysis, nonlinearity, transient excitation, extreme stress, error estimation