An assessment of trailer suspension dynamic behavior via vibration measurements

A dynamic response of a semi-trailer suspension to a real road profile under two different loads was investigated in this study. The trailer was a low loader for transporting heavy and large loads which configuration could be adjusted to the current needs. During the described investigation the vehicle was composed of: detachable gooseneck, maximally extended low bed and 5 hydraulically steered axles comprised 2-axle and 3-axle assemblies. The experiments were performed for unloaded and loaded with 60 tons trailer, that was equal to maximum trailer pay load. Acceleration measurements at unsprung and sprung parts of the vehicle were applied. As a test surface a railway track crossing was chosen. Acceleration time series were analysed by the means of power spectral density. The isolation of free vibration and forced vibration frequencies and effectiveness of suspension damping over wide frequency range was done. Two characteristic signal bands were identified. In the frequency range up to 10 Hz vehicle vibration energy decreased for the load increase for both, sprung and unsprung parts. In contrast, in the range between 10 and 25 Hz at higher load increase of vibration energy was noticed, however only at unsprung mass. Data analysis revealed complexity of vehicle vertical acceleration as a response to the road profile. Nevertheless, it allowed for estimation of the trailer dynamic loads under real road conditions.