Vasil B. Georgiev

Finite Element Study of the Effect of Structural Modifications on Structure-borne Vehicle Interior Noise

This paper presents the results of the numerical investigation of structure-borne vehicle interior noise in a simplified model of vehicle compartment. The aim of the paper is to analyze the effects of different variations of certain geometrical and material parameters of vehicle structure on structural-acoustic frequency response functions. It has been found that geometrical modifications have little influence on the structural natural frequencies. However, they strongly affect the acoustic natural frequencies and normal modes as well as the resulting sound pressure responses. The increase in thickness of the bottom plate suppresses the sound pressure responses very efficiently. However, variations of material characteristics of wind- and back-screen do not have much influence on the interior noise.

Simplified Modelling of Vehicle Interior Noise: Comparison of Analytical, Numerical and Experimental Approaches:

The present paper describes the results of the investigation of low and medium frequency vehicle interior noise carried out using simplified structural-acoustic models. Analytical, finite element (FE) and experimental studies are presented and compared. In particular, the analytical approach is based on the formula representing the interior acoustic pressure in terms of structural and acoustic normal modes. This procedure does not take into account the effect of the enclosed air on structural vibrations. The FE analysis considers structural vibration modes, interior acoustic modes, full structural-acoustic interaction and the resulting structure-borne noise. The above-mentioned analytical and numerical results are compared with each other, and both of them are compared with the experimental results obtained for the simplified reduced-scale vehicle model “QUASICAR” developed in Loughborough University. The comparisons demonstrate some specific features of the analytical and numerical approaches and outline the acceptable limits of simplification in modelling vehicle interior noise. Although this study is concerned with structure-borne vehicle interior noise, its results and conclusions could be of interest for a wider range of engineering problems, such as building acoustics and dynamics of thin shell structures.

Semianalytical modeling of plate flexural waves generated by laser‐initiated air shock waves

The paper describes the results of the semianalytical modeling of the interaction of laser‐initiated air shock waves with an infinite elastic plate. The impact of the incident shock wave on the plate has been approximated by an equivalent cylindrically diverging surface force resulting from the combined surface pressure of the incident and reflected shock waves. This force has been then represented in the wave number‐frequency domain by means of Hankel and Fourier transforms which have been carried out numerically ‐ and the problem has been solved using the Greens function method applied to an infinite plate. The resulting frequency spectra and time histories of the generated flexural wave pulses have been calculated for different values of laser pulse energy and for different heights of the laser beam focusing above the plate surface. The obtained theoretical results have been compared with the results of the reduced‐scale model experiments on shock wave interaction with the ground in which large plasti...

Generation of Rayleigh-type Waves on Plate Edges by Laser-initiated Airborne Shock Waves

The present paper describes the results of the semi-analytical modelling of the interaction of laser-initiated air shock waves with the edge of an infinite vertically mounted elastic plate. The impact of the shock wave on the plate edge is approximated by an equivalent edge force resulting from the combined pressure of the incident and reflected shock waves. This force is then represented in the wavenumber-frequency domain by means of Fourier transforms that are carried out numerically. After that the problem is solved using the Green’s function method. The resulting frequency spectra and time histories of generated Rayleigh-type wave pulses propagating along the plate edge are calculated for different heights of the laser beam focusing above the plate edge. The obtained theoretical results are compared with the results of the laboratory experiments on laser-initiated air shock wave interaction with an edge of a large vertically mounted Perspex plate that is used for reduced-scale modelling of blast wave interaction with the ground surface. The resonant properties of the accelerometer have been taken into account to describe the received signals. The comparison shows that the obtained semi-analytical results are in good agreement with the experiments.