Identification of modular firefighting superstructures' dynamic behaviour

Abstract

Specific functional requirements for firefighting vehicles have resulted in stricter exploitation regimes and frequent off-road use. Current practice appoints the problem of the strength of a superstructure's modules, which are very different in terms of torsional rigidity. It is important to say here that there are no unambiguous manufacturer's guidelines for bodybuilders to complete a firefighting vehicle. In such circumstances, the identification of the dynamic behaviour of modular firefighting superstructures further gains in importance. Developed numerical-experimental approach for identification, analysis and optimisation of the dynamic behaviour of modular firefighting vehicle superstructures is shown. Experimental part of this method is based on excitation of superstructure physical models with, for this purpose specially developed mechanical exciter. Also, natural frequencies of structures, important in terms of resonant zones, are obtained using bump test and FFT analysis. Finite elements method is defined as a diagnostic tool for the identification of structure behaviour, and the measured acceleration values at characteristic points as a proof of the model's correctness i. e. correctness of the applied optimisation approach. The numerical analysis of influence of suspension characteristics and connections of superstructure modules on their dynamic behaviour (eigen-frequencies and amplitudes) are also presented. Comparative analysis of the experimental and numerical results verified the numerical model. Such a model can save the time and money by reducing the experiments needed in the modular firefighting vehicle superstructures optimisation.