Avaliação de um sistema de fixação em poltronas de um ônibus urbano

Abstract

The present work studied the bolted joint used to fix the feet of seats on the floor of a bus used in urban public transport. Ensuring the integrity of the seat fastening is essential for the safety of bus passengers, since its daily use involves everything from the accommodation of the seated passenger to the support for passengers who are standing. This work evaluated the relaxation and the loss of tightening torque of the bolted joint in question, considering the various variable loads to which the joint is subjected daily, for this purpose, piezoelectric load cells were used in the joint screws, making the collection of the traction loads with the vehicle traveling on different types of tracks and with passengers performing various daily actions under the seat that can somehow interfere with the correct functioning of the bolted joint. To obtain the necessary data on the materials that make up the joint, mechanical tests were carried out in the mechanical testing laboratory of the company Marcopolo and in the polymer laboratory of the University of Caxias do Sul. Through the results obtained in the tests, calculations were performed according to the VDI 2230 standard and based on the results of the calculations, proposals for improvements in the dimensioning of the joint were suggested, mainly due to the existence of the wooden floor and the polymeric carpet in the composition of the joint's counterparts screwed. The improvement proposals presented involved the use of a steel bushing around the screws and the validation tests of the proposals presented pre-load loss values of 5.1% and 6.6%, values below the current configuration of the joint bolted with a pre-load loss of 29.4% (sic).