farzad rafieian

Tractor drivers’ health is so important and some injuries can develop in the long run such as lower back pain or spinal column disorder resulting from low-frequency vibrations. Seat suspension plays a crucial role in the reduction of harmful vibrations in off-road vehicles. Passive suspension design parameters should be tuned properly to remove vibrations efficiently. Lumped parameter models have been widely used in seat suspension optimization to simulate human body responses. In this study, a tractor seat suspension was designed based on an artificial neural network biodynamic model instead of a lumped model. In the optimisation step, a novel approximation approach via an artificial neural network was employed to minimise seat-to-spine vibration transmissibility. Then, a seat suspension was modified based on the optimisation results, and an outdoor dynamic test was carried out to evaluate suspension in vibration transmissibility attenuation.  The gathered data were processed and analyzed in terms of vibration transmissibility, mobility, and apparent mass. The transmitted vibration from floor to spine was measured between 0.2 and 0.4 at 4 to 6 Hz (spine dominant frequency range) on bumpy and smooth roads at various traveling speeds. The effect of seat suspension modification showed the changes in the performance of seat suspension in regard to vibration transmissibility. Thus, this passive suspension may decrease the risk of lower back pain for tractor drivers. So, this modification can be considered by the tractor manufacturer for future designed models to provide more comfort for operators in the daily use of this device.

This paper is about the application of instantaneous angular speed (IAS) signal in a 3-liter six-cylinder gasoline engine. The study is in continuation of former work in which a measurement system was developed for this signal on a rotating machine. The future trend of the research is to measure IAS in an I.C. engine. Therefore, the objective of the current work is to provide a verified software tool which can run simulated experiments with IAS signal output under healthy/faulty conditions. An engine model with detailed crankshaft elements is established in the GT-SUITE[1]</sup> software. Under the GT-SUITE environment, IAS signal output is obtained through simulated experiments. In order to validate the tool, the first torsional natural frequency of the crankshaft obtained from frequency analysis on the IAS signal is compared with the result of modal analysis on the crankshaft structure using the F.E. method. Also, the value is compared with the prediction from the GT CrankAnalysis module. A good match is found, which shows the validity of the developed software tool. Faulty condition of misfiring in one cylinder is simulated using this tool, and expected observations on the IAS output signal are verified to address the future trend of the research using the developed tool in this study.

Town Board Stations (TBS) are usually located in residential areas. Pressure reduction through reducing valves in these stations generates considerable amounts of sound and vibrations. These mechanical waves have undesired effects on the equipment such as reducing the fatigue life of the gas ransmission line. On the other hand, propagation of these wave in the residential area, auses discomfort for the neighbors of these stations. In this paper, vibrations enerated in a TBS and transmitted to the residential building in the area are investigated through modeling and analysis. The aim is to study and propose a method for reducing vibration transmission from the TBS to residential buildings by using a numerical model. A vibration isolator is designed for this purpose with ptimum parameters and considering the practical limitations of the problem. The performance of the isolator is verified with the help of the developed FEmodel. Results show the effectiveness of the designed vibration isolator for the operating range of the TBS.